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Structure of arthropod communities in some saline lakes of central British Columbia Lancaster, Jill 1985

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STRUCTURE OF ARTHROPOD COMMUNITIES IN SOME SALINE LAKES OF CENTRAL BRITISH COLUMBIA By J I L L LANCASTER B . S c . (Honours) U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1983 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF ZOOLOGY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o 13ie reqira?e~d standaftad September, 1985 © J i l l L a n c a s t e r , 1985 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of 1£Oo UDfe JT* The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Drink*, 1 - / f r < i i ABSTRACT A q u a t i c a r t h r o p o d s communities were examined w i t h r e s p e c t t o f a c t o r s d e t e r m i n i n g s p e c i e s d i s t r i b u t i o n s and community s t r u c t u r e i n a s e r i e s o f e i g h t l a k e s on t h e C h i l c o t i n P l a t e a u o f B r i t i s h C o l u m b i a . C l i m a t e , a l t i t u d e , p h y s i c a l l o c a t i o n , w a t e r t e m p e r a t u r e and b a s i n shape were s i m i l a r f o r a l l l a k e s , and a l t h o u g h s i z e d i f f e r e d , no e v i d e n c e was found f o r t h e i n f l u e n c e o f b a s i n morphology on community s t r u c t u r e . S a l i n i t y and v e g e t a t i o n c h a r a c t e r i s t i c s d i f f e r e d w i d e l y among l a k e s , so t h r e e major p r o c e s s e s were i n v e s t i g a t e d : t h e a s s o c i a t i o n o f (1) s a l i n i t y w i t h f a u n a l c o m m u n i t i e s , (2) s a l i n i t y w i t h f l o r a l c o m m u n i t i e s , and (3) f a u n a l w i t h f l o r a l c o m m u n i t i e s . These r e l a t i o n s h i p s were examined i n l i g h t o f d i v e r s i t y - s t a b i l i t y h y p o t h e s e s . The s e v e r i t y component o f e n v i r o n m e n t a l s t a b i l i t y was r e p r e s e n t e d by s a l i n i t y , and mean s u r f a c e w a t e r c o n d u c t i v i t y ranged from 56 t o 13115 uS c m - ! a t 2 5 °c. S a l i n i t y v a r i a t i o n s among l a k e s were d e t e r m i n e d p r i m a r i l y by t h e i o n s Na, H C O 3 , C O 3 , CI and K. Two c l a s s i f i c a t i o n schemes (taxonomic and e c o l o g i c a l ) and s e v e r a l a n a l y t i c a l t e c h n i q u e s (community parameters and c l u s t e r a n a l y s i s ) i n d i c a t e d t h a t the d i s t r i b u t i o n and s t r u c t u r e o f f a u n a l and f l o r a l communities were r e l a t e d t o s a l i n i t y . In t o t a l , 84 a r t h r o p o d t a x a and 26 macrophyte s p e c i e s were found and d i v i d e d i n t o t h r e e g r o u p s : t h o s e c h a r a c t e r i s t i c o f h i g h s a l i n i t i e s (>5000 u S ) , o f moderate o r low s a l i n i t i e s (<5000 u S ) , o r t o l e r a n t o f a l l s a l i n i t i e s . Faunal assemblages i n a l l l a k e s were dominated by f i l t e r f e e d e r s , and p r e d a t o r s were more abundant i n s a l i n e l a k e s . S h r e d d e r s , c o l l e c t o r s and p r e d a t o r s were found i n a l l the l a k e s , b u t s a l i n e l a k e s had fewer s i z e g r o u p s . F l o a t i n g l e a v e d macrophytes o c c u r r e d o n l y i n i i i f r e s h w a t e r l a k e s , submerged forms were r a r e i n h i g h l y s a l i n e l a k e s , and emergent forms were found i n a l l l a k e s , a l t h o u g h they were l e s s abundant a t h i g h s a l i n i t i e s . G e n e r a l l y , t h i s study s u p p o r t s t h e h y p o t h e s i s t h a t s a l i n e h a b i t a t s have l e s s d i v e r s e communities than f r e s h w a t e r o n e s . In a l l f l o r a l and f a u n a l sample s e t s , i n c r e a s e d s a l i n i t y was accompanied by a d e c r e a s e i n s p e c i e s r i c h n e s s . V i r t u a l l y a l l measures o f macrophyte community d i v e r s i t y and p r o d u c t i v i t y were i n v e r s e l y c o r r e l a t e d w i t h s a l i n i t y . Faunal subgroups must be examined s e p a r a t e l y when measures o f community s t r u c t u r e i n c o r p o r a t e r e l a t i v e abundances. P a t t e r n s o f a s s o c i a t i o n o b s e r v e d i n the e n t i r e f a u n a l community were d i c t a t e d by t h e n u m e r i c a l l y dominant e n t o m o s t r a c a n subcommunity, and p a t t e r n s i n o t h e r subgroups were masked. Z o o p l a n k t o n t r o p h i c l e v e l d i v e r s i t y i n c r e a s e d w i t h d e c r e a s i n g s a l i n i t y and changes i n community c o m p o s i t i o n were analogous t o t h o s e o f e u t r o p h i c a t i o n . In both c o l e o p t e r a n and hemipteran c o m m u n i t i e s , d i v e r s i t y d e c r e a s e d and d e n s i t y i n c r e a s e d w i t h i n c r e a s i n g s a l i n i t y . P o s s i b l e c a u s a l mechanisms s t r u c t u r i n g each community a r e h y p o t h e s i z e d . Faunal d i s t r i b u t i o n s c o r r e s p o n d e d t o t h e i r known h a b i t a t p r e f e r e n c e s i n terms o f macrophyte c o m m u n i t i e s . I t was d i f f i c u l t t o d i s t i n g u i s h between t h e i n f l u e n c e o f s a l i n i t y o r macrophyte communities on animal communities as animal communities were o f t e n a s s o c i a t e d w i t h b o t h . TABLE OF CONTENTS Page A b s t r a c t i i T a b l e o f C o n t e n t s i v L i s t o f T a b l e s v i L i s t o f F i g u r e s v i i i L i s t o f P l a t e s x L i s t o f A p p e n d i c e s x i Acknowl edgements x i i G e n e r a l I n t r o d u c t i o n 1 S i t e D e s c r i p t i o n 6 C h a p t e r _1: P h y s i o c h e m i c a l F e a t u r e s I n t r o d u c t i o n 11 M a t e r i a l s and Methods 14 R e s u l t s and D i s c u s s i o n 18 Summary 29 C h a p t e r 2: Fauna! Communities I n t r o d u c t i o n 30 M a t e r i a l s and Methods 36 R e s u l t s 43 D i s c u s s i o n 81 Summary 100 C h a p t e r 3 :^ Macrophyte Communities I n t r o d u c t i o n 104 M a t e r i a l s and Methods 106 R e s u l t s 108 D i s c u s s i o n 130 V P a g e > Summary 136 C h a p t e r 4_: R e l a t i o n s h i p s B e t w e e n F a u n a l a n d F l o r a l C o m m u n i t i e s I n t r o d u c t i o n 138 M a t e r i a l s a n d M e t h o d s 141 R e s u l t s 142 D i s c u s s i o n 149 Summary 159 R e f e r e n c e s 161 A p p e n d i c e s 176 LIST OF TABLES Page T a b l e 1 Annual v a r i a t i o n s i n mean s u r f a c e c o n d u c t i v i t y o f study l a k e s 21 T a b l e 2 Mean c o n d u c t i v i t y and p r e d i c t e d i o n c o n c e n t r a t i o n s i n 1 9 7 8 . . . . 2 1 T a b l e 3 P r i n c i p a l component s c o r e s f o r l a k e s and i o n s , p l u s c o r r e l a t i o n o f i o n PC s c o r e s w i t h i o n c o n c e n t r a t i o n s 22 T a b l e 4 Morphometric p r o p e r t i e s o f study l a k e s 22 T a b l e 5 C o r r e l a t i o n s among a b i o t i c v a r i a b l e s 23 T a b l e 6 L i s t o f community parameters used to c h a r a c t e r i z e f a u n a l communities 41 T a b l e 7 L i s t o f s p e c i e s p r e s e n t i n s a m p l e s , t h e i r s i z e , t r o p h i c l e v e l and d i s t r i b u t i o n 44 T a b l e 8 Numerical v a l u e s f o r f a u n a l community parameters 63 T a b l e 9 Summary o f r e l a t i o n s h i p s between community parameters 65 T a b l e 10 Summary o f r e l a t i o n s h i p s between community p a r a m e t e r s and p h y s i o c h e m i c a l v a r i a b l e s 67 T a b l e 11 C o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s between p h y s i o c h e m i c a l and f a u n a l dendrograms 80 T a b l e 12 D i s t r i b u t i o n o f a q u a t i c p l a n t s r e c o r d e d by C.W.S 117 T a b l e 13 A q u a t i c macrophyte community parameters 121 T a b l e 14 Summary o f r e l a t i o n s h i p s between p h y s i o c h e m i c a l v a r i a b l e s and a q u a t i c macrophyte community parameters 121 T a b l e 15 A q u a t i c p l a n t p r o d u c t i v i t y measured i n 1984 and i t s r e l a t i o n s h i p t o a b i o t i c v a r i a b l e s 131 T a b l e 16 Summary o f r e l a t i o n s h i p s between f l o r a l and f a u n a l community p a r a m e t e r s 143 v i i Page T a b l e 17 Summary o f r e l a t i o n s h i p s between f l o r a l and f a u n a l community parameters and s a l i n i t y 145 T a b l e 18 C o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l and f l o r a l dendrograms 147 v i i i LIST OF FIGURES Page F i g u r e 1 Map o f study a r e a 7 F i g u r e 2 D a i l y t e m p e r a t u r e range i n Lake 1 (Box 27) i n 1978 19 F i g u r e 3 Seasonal c o n d u c t i v i t y o f each l a k e i n 1978 19 F i g u r e 4 C l u s t e r a n a l y s i s o f study l a k e s based on d i s s i m i l a r i t y o f 1978 p r e d i c t e d i o n i c c o m p o s i t i o n , and p r e d i c t e d i o n i c c o m p o s i t i o n p l u s morphometric c h a r a c t e r i s t i c s 27 F i g u r e 5 C l u s t e r a n a l y s i s o f a r t h r o p o d s p e c i e s based on s i m i l a r i t y o f l a k e s o c c u p i e d 47 F i g u r e 6 C o m p o s i t i o n and r e l a t i v e abundance o f l i m n e t i c z o o p l a n k t o n c o l l e c t e d i n Van Dorn b o t t l e s 50 F i g u r e 7 C o m p o s i t i o n and r e l a t i v e abundance o f E n t o m o s t r a c a c o l l e c t e d i n l i g h t t r a p s 50 F i g u r e 8 C o m p o s i t i o n and r e l a t i v e abundance o f a l l s p e c i e s c o l l e c t e d i n l i g h t t r a p s 54 F i g u r e 9 C o m p o s i t i o n and r e l a t i v e abundance o f C o l e o p t e r a c o l l e c t e d i n l i g h t t r a p s 57 F i g u r e 10 C o m p o s i t i o n and r e l a t i v e abundance o f C o l e o p t e r a c o l l e c t e d i n sweep n e t s 57 F i g u r e 11 C o m p o s i t i o n and r e l a t i v e abundance o f Hemiptera c o l l e c t e d i n l i g h t t r a p s 60 F i g u r e 12 C o m p o s i t i o n and r e l a t i v e abundance o f Hemiptera c o l l e c t e d i n sweep n e t s 60 F i g u r e 13 Mean and s t a n d a r d e r r o r o f d i v e r s i t y v s . t ime i n l i m n e t i c z o o p l a n k t o n communities 66 Page F i g u r e 14 C l u s t e r a n a l y s i s o f study l a k e s based on z o o p l a n k t o n c o l l e c t e d i n Van Dorn b o t t l e s 71 F i g u r e 15 C l u s t e r a n a l y s i s o f s t u d y l a k e s based on E n t o m o s t r a c a c o l l e c t e d i n l i g h t t r a p s 71 F i g u r e 16 C l u s t e r a n a l y s i s o f study l a k e s based on a l l s p e c i e s c o l l e c t e d i n l i g h t t r a p s 73 F i g u r e 17 C l u s t e r a n a l y s i s o f study l a k e s based on C o l e o p t e r a c o l l e c t e d i n l i g h t t r a p s 75 F i g u r e 18 C l u s t e r a n a l y s i s o f study l a k e s based on C o l e o p t e r a c o l l e c t e d i n sweep n e t s 75 F i g u r e 19 C l u s t e r a n a l y s i s o f study l a k e s based on Hemiptera c o l l e c t e d i n l i g h t t r a p s 77 F i g u r e 20 C l u s t e r a n a l y s i s o f study l a k e s based on Hemiptera c o l l e c t e d i n sweep n e t s 77 F i g u r e 21 Seasonal c o n d u c t i v i t y o f each l a k e i n 1983 and 1984 109 F i g u r e 22 C l u s t e r a n a l y s i s o f s t u d y l a k e s based on p r e d i c t e d i o n i c c o m p o s i t i o n and morphometric c h a r a c t e r s , f o r 1983 and 1 9 8 4 . . I l l F i g u r e 23 C l u s t e r a n a l y s i s o f a q u a t i c macrophyte s p e c i e s based on s i m i l a r i t y o f l a k e s o c c u p i e d 118 F i g u r e 24 R e l a t i v e p r o p o r t i o n o f f l o a t i n g , submerged and emergent macrophytes i n each l a k e 120 F i g u r e 25 C l u s t e r a n a l y s i s o f study l a k e s based on macrophyte s p e c i e s c o m p o s i t i o n and r e l a t i v e abundance 123 F i g u r e 26 Macrophyte s t a n d i n g c r o p i n the l i t t o r a l zone o f each l a k e . . 1 2 6 F i g u r e 27 S t a n d a r d i z e d macrophyte s t a n d i n g c r o p i n the l i t t o r a l zone o f each l a k e 128 X LIST OF PLATES Page P l a t e 1 Lake 2 ( B a r k l e y L . ) s i t u a t e d i n a d e p r e s s i o n i n the r o l l i n g p r a i r i e 9 P l a t e 2 S h a l l o w , s o f t s h o r e l i n e o f Lake 2 ( B a r k l e y L . ) 9 P l a t e 3 F i r m , g r a v e l l y bottom o f Lake 7 (Round-Up) w i t h w h i t e p r e c i p i t a t e d s a l t s on emergent r o c k s 10 P l a t e 4 Stands o f emergent S c i r p u s l a c u s t r i s and a heavy a l g a l bloom on t h e s u r f a c e o f Lake 5 ( J a c k s o n L . ) 113 P l a t e 5 Lake 3 (Near O p p o s i t e C r e s c e n t ) i n e a r l y s p r i n g b e f o r e any annual p l a n t growth 113 P l a t e 6 Mat o f f l o a t i n g - l e a v e d Potamogeton natans i n Lake 1 (Box 2 7 ) . . 1 1 4 P l a t e 7 Submerged M y r i o p h y l l u m e x a l b e s c e n s i n Lake 2 ( B a r k l e y L . ) 114 P l a t e 8 Submerged v e g e t a t i o n i n Lake 4 (Rock L . ) 115 P l a t e 9 M a r g i n o f emergent J u n c u s b a l t i c u s i n Lake 8 ( B a r n e s L . ) 115 x i LIST OF APPENDICES Page Appendix A Seasonal c o n d u c t i v i t y o f each l a k e i n 1978 176 Appendix B Abundance o f a r t h r o p o d s p e c i e s and e c o l o g i c a l c a t e g o r i e s i n each study l a k e c o l l e c t e d i n : 1 . Van Dorn water b o t t l e s 177 2 . Submerged l i g h t t r a p s 178 3 . L i t t o r a l sweep n e t s 182 Appendix C P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l community parameters 184 Appendix D P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l community parameters and p h y s i o c h e m i c a l v a r i a b l e s . . . 1 8 5 Appendix E Mean c o n d u c t i v i t y o f each study l a k e i n 1 9 8 3 , and s e a s o n a l c o n d u c t i v i t y o f each i n 1984 187 Appendix F R e l a t i v e abundance o f macrophyte s p e c i e s i n each l a k e 188 Appendix G P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f l o r a l community parameters and p h y s i o c h e m i c a l v a r i a b l e s . . . 1 9 0 Appendix H P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l and f l o r a l community parameters 191 x i i ACKNOWLEDGEMENTS I would l i k e thank my s u p e r v i s o r , D r . G . G . E . S c u d d e r , f o r i n i t i a t i n g t h i s p r o j e c t and s u p p o r t i n g my w o r k , p l u s my committee members, D r . W.E. N e i l l and D r . C C . L i n d s e y , f o r h e l p i n g me s t a y on t h e r i g h t t r a c k . I am much i n d e b t e d t o D r . N e i l l f o r r e a d i n g e a r l y d r a f t s o f t h e m a n u s c r i p t and p r o v i d i n g i n v a l u a b l e a d v i c e and encouragement. I owe many thanks t o S y d , D i c k and Rob Cannings f o r t h e i r t i m e i n t h e f i e l d c o l l e c t i n g samples and d a t a , and f o r t h e i r p a t i e n c e a n s w e r i n g i n t e r m i n a b l e q u e s t i o n s . Thanks t o S . Boyd and t h e Canadian W i l d l i f e S e r v i c e f o r making t h e i r d a t a a v a i l a b l e . D . J . L a r s o n o f the Memorial U n i v e r s i t y o f Newfoundland and R . E . Roughley o f the U n i v e r s i t y o f M a n i t o b a p r o v i d e d a s s i s t a n c e i d e n t i f y i n g b e e t l e s . C o n g r a t u l a t i o n s and thanks t o a l l the p e o p l e who s u r v i v e d my memorable c o l l e c t i n g a d v e n t u r e s t o R i s k e C r e e k : Doug R e i d , Kathy B e l l , Heather McLean, E d i e B i j d e m a s t and Paul C o o p e r . Most i m p o r t a n t l y , a v e r y s p e c i a l t h a n k s t o D r . L . M . "Weirdo" Moore and J . J . " N o - B r a k e s " R o b i n s o n , my f e l l o w inmates o f t h e B r a i n - D e a t h Ward, who p r o v i d e d t h e n e c e s s a r y s u p p o r t and comic r e l i e f t h a t h e l p e d t u r n my " i m a g i n a r y t h e s i s " i n t o a r e a l i t y . Lynn k i n d l y waded t h r o u g h p a r t s o f the m a n u s c r i p t and a s s u r e s me i t i s w r i t t e n i n E n g l i s h . E d i e B i j d e m a s t , Syd C a n n i n g s , D i c k C a n n i n g s , R i c h L e c h l e i t n e r , Joan M a r t i n , G a r r y S t e n s o n , and a l l t h e o t h e r c r i t t e r s , d e s e r v e medals f o r p u t t i n g up w i t h me and my p r a n k s , and f o r making the f o u r t h f l o o r a t e r r i f i c p l a c e t o b e . T h i s r e s e a r c h was s u p p o r t e d by an NSERC P o s t Graduate S c h o l a r s h i p t o J . L a n c a s t e r and an NSERC O p e r a t i n g G r a n t t o D r . G . G . E . S c u d d e r . 1 GENERAL INTRODUCTION I n l a n d s a l i n e l a k e s c o m p r i s e o n l y a very s m a l l f r a c t i o n o f the t o t a l a q u a t i c e n v i r o n m e n t , y e t they have i n t r i g u e d b i o l o g i s t s f o r many y e a r s . These unusual h a b i t a t s c o n f r o n t p o t e n t i a l c o l o n i z i n g organisms w i t h e x t r e m e l y s e v e r e o s m o t i c p r o b l e m s , b u t n e v e r t h e l e s s they c o n t a i n some c h a r a c t e r i s t i c i n h a b i t a n t s ( B a y l y , 1 9 7 2 ) . Q u e s t i o n s o f how a q u a t i c organisms a r e a f f e c t e d by w a t e r s a l i n i t y can be approached a t an e c o l o g i c a l o r p h y s i o l o g i c a l l e v e l : p h y s i o l o g i c a l l y , e n v i r o n m e n t a l f a c t o r s " a c t " a t the o r g a n i s m a l l e v e l whereas e c o l o g i c a l l y , h i g h e r l e v e l s o f community o r g a n i z a t i o n can be c o n s i d e r e d an i n t e g r a t i o n o f a l l t h e d i r e c t i n d i v i d u a l - e n v i r o n m e n t r e l a t i o n s ( S c o t t , 1 9 7 4 ) . T h i s i n v e s t i g a t i o n does n o t deal w i t h t h e p h y s i o l o g i c a l p r o c e s s e s o f o s m o t i c r e g u l a t i o n and t o l e r a n c e , b u t c o n c e n t r a t e s on t h e e c o l o g i c a l l e v e l o f community s t r u c t u r e i n s a l i n e l a k e s e r i e s . Lakes o f t h e C h i l c o t i n P l a t e a u r e g i o n o f B r i t i s h Columbia p r e s e n t an i d e a l o p p o r t u n i t y t o study the e f f e c t s o f s a l i n i t y on a q u a t i c organisms as they c o v e r a wide range o f s a l i n i t y , w h i l e many o t h e r f a c t o r s such as c l i m a t e , a l t i t u d e and g e o g r a p h i c a l l o c a t i o n a r e s i m i l a r f o r a l l l a k e s . P r e v i o u s s t u d i e s comparing s a l i n e l a k e f l o r a and fauna have encompassed ranges o f c l i m a t e , a l t i t u d e , o r permanence, so s e v e r a l major e n v i r o n m e n t a l f a c t o r s o t h e r than s a l i n i t y may have a f f e c t e d the b i o t a o f t h e s e l a k e s ( B e a d l e , 1943; Rawson & Moore, 1944; Moore, 1952; B a y l y & W i l l i a m s , 1966; Hammer e t a l _ . , 1975; Geddes e t a l _ . , 1981; Brock & S h i e l , 1983; G a l a t & R o b i n s o n , 1983; Timms, 1983; van V i e r s s e n & V e r h o e v e n , 1 9 8 3 ) . Timms (1981) s t u d i e d t h r e e l a k e s t h a t had s i m i l a r p h y s i o g r a p h i c a l and p h y s i o c h e m i c a l f e a t u r e s e x c e p t s a l i n i t y , b u t more than t h r e e l a k e s a r e r e q u i r e d t o 2 a d e q u a t e l y d e s c r i b e p a t t e r n s i n community s t r u c t u r e and c o r r e l a t e them w i t h e n v i r o n m e n t a l v a r i a b l e s . I t has been e s t a b l i s h e d t h a t t h e s a l i n i t y g r a d i e n t p r e s e n t i n t h e s e C h i l c o t i n l a k e s i n f l u e n c e s the d i s t r i b u t i o n o f o r g a n i s m s , i . e . a q u a t i c angiosperms ( R e y n o l d s & R e y n o l d s , 1 9 7 5 ) , H i r u d i n e a (Scudder & Mann, 1 9 6 8 ) , a r t h r o p o d s ( S c u d d e r , 1 9 6 9 a ) , c r u s t a c e a n z o o p l a n k t o n ( R e y n o l d s , 1 9 7 9 ) , Odonata (Cannings e t a l _ . , 1980; Cannings & C a n n i n g s , 1 9 8 5 ) , C o r i x i d a e ( S c u d d e r , 1969b; 1 9 8 3 ) , and Chironomidae (Cannings & S c u d d e r , 1 9 7 8 ) . However, v i r t u a l l y no work has been done on community s t r u c t u r e o r the r e l a t i o n s h i p between p l a n t and animal communities i n t h e s e l a k e s . There a r e t h r e e major p r o c e s s e s which need t o be i n v e s t i g a t e d s i m u l t a n e o u s l y i n o r d e r t o u n d e r s t a n d the community s t r u c t u r e and s p e c i e s i n t e r a c t i o n s o f s a l i n e l a k e e c o s y s t e m s : (1) the e f f e c t s o f s a l i n i t y on animal c o m m u n i t i e s , (2) t h e e f f e c t s o f s a l i n i t y on p l a n t c o m m u n i t i e s , and (3) t h e r e l a t i o n s h i p between p l a n t and animal c o m m u n i t i e s . There have been a number o f s t u d i e s on s a l i n e l a k e fauna and s a l i n e l a k e f l o r a , b u t few have a t t e m p t e d t o r e l a t e the t w o , as t h i s study d o e s . One o f t h e d i f f i c u l t i e s accompanying s t u d i e s o f community s t r u c t u r e a l o n g e n v i r o n m e n t a l g r a d i e n t s i s how b e s t t o q u a n t i f y and d e s c r i b e both t h e e n v i r o n m e n t and community. In o r d e r t o p r o v i d e a complete p i c t u r e and a v o i d a b i a s e d p e r s p e c t i v e , s e v e r a l d i f f e r e n t and complementary t e c h n i q u e s s h o u l d be employed. In t h i s s t u d y , a b i o t i c and b i o t i c a s p e c t s o f the l a k e s were d e s c r i b e d i n two g e n e r a l ways: s i m p l e q u a n t i t a t i v e parameters and m u l t i v a r i a t e t e c h n i q u e s . M u l t i v a r i a t e t e c h n i q u e s o b j e c t i v e l y s e a r c h f o r p a t t e r n s among communities t h a t may c o r r e s p o n d t o e n v i r o n m e n t a l g r a d i e n t s , whereas q u a n t i t a t i v e c o m p a r i s o n s o f n u m e r i c a l parameters t e s t f o r s p e c i f i c r e l a t i o n s h i p s between the a b i o t a and b i o t a . In t h i s s t u d y , comparisons 3 between b i o t i c and a b i o t i c n u m e r i c a l parameters a r e perhaps b e s t viewed i n terms o f t h e d i v e r s i t y - s t a b i l i t y c o n c e p t , a t o p i c a l and c o n t r o v e r s i a l a r e a o f e c o l o g y . The c o n c e p t o f a r e l a t i o n s h i p between d i v e r s i t y and s t a b i l i t y has been p r e v a l e n t i n e c o l o g i c a l l i t e r a t u r e f o r the p a s t 30 y e a r s , and much o f the c o n t r o v e r s y a s s o c i a t e d w i t h t h i s t o p i c i s a t t r i b u t e d t o the wide spectrum o f meanings c o v e r e d by t h e terms " d i v e r s i t y " and " s t a b i l i t y " . D i v e r s i t y and s t a b i l i t y a r e r e l a t e d not by one h y p o t h e s i s , b u t r a t h e r a whole f a m i l y o f hypotheses depending on whether t h e s e terms a r e a p p l i e d t o e i t h e r t h e a b i o t i c e n v i r o n m e n t o r the b i o t i c community. Some g e n e r a l hypotheses a r e : 1 . D i v e r s e communities a r e more ( o r l e s s ) s t a b l e than l e s s d i v e r s e c o m m u n i t i e s . 2 . D i v e r s e environments have more ( o r l e s s ) s t a b l e / d i v e r s e communities than l e s s d i v e r s e e n v i r o n m e n t s . 3 . S t a b l e environments have more ( o r l e s s ) s t a b l e / d i v e r s e communities than l e s s s t a b l e e n v i r o n m e n t s . A s h o r t paper by MacArthur (1955) t h a t attempted t o r e l a t e community s t a b i l i t y t o f o o d web s t r u c t u r e ( d i v e r s i t y ) , s t i m u l a t e d a p l e t h o r a o f s t u d i e s t e s t i n g Group 1 type h y p o t h e s e s . Goodman (1975) r e v i e w s much o f the e a r l y l i t e r a t u r e on t h i s t o p i c and f i n d s no e v i d e n c e s u p p o r t i n g M a c A r t h u r 1 s h y p o t h e s i s . Hypotheses d e a l i n g w i t h d i v e r s e environments (Group 2) o f t e n f o c u s on the r e l a t i o n s between s p a t i a l o r s u b s t r a t e h e t e r o g e n e i t y and community s t r u c t u r e , as seen i n s t u d i e s on b i r d s p e c i e s d i v e r s i t y ( M a c A r t h u r & M a c A r t h u r , 1961; MacArthur et _ a l . , 1 9 6 6 ) . T e s t s o f Group 3 hypotheses examine r e l a t i o n s between e n v i r o n m e n t a l g r a d i e n t s and b i o t i c c o m m u n i t i e s , a common t o p i c i n e c o l o g y , a l t h o u g h many such s t u d i e s a r e n o t d i s c u s s e d i n t h e framework o f d i v e r s i t y - s t a b i l i t y t h e o r y . Some 4 s t u d i e s s u c c e s s f u l l y c o n f u s e t h e s e groups o f h y p o t h e s e s , t h e r e b y a d d i n g t o the c o n t r o v e r s y . Z a r e t (1982) a t t e m p t e d t o r e l a t e Group 1 and Group 3 t y p e h y p o t h e s e s , b u t appears t o have f a l l e n s h o r t o f h i s g o a l , p a r t l y owing t o a c a r e l e s s n e s s o f t e r m i n o l o g y (Kimmerer, 1 9 8 4 ) , a l t h o u g h Kimmerer h i m s e l f uses some f a l l a c i o u s a r g u m e n t s . T h i s p a r t i c l u a r study uses a s a l i n e l a k e s e r i e s p r i m a r i l y t o t e s t t h e h y p o t h e s i s t h a t s t a b l e e n v i r o n m e n t s have more d i v e r s e f a u n a l (and f l o r a l ) communities than l e s s s t a b l e ones (Group 3 ) . S e c o n d a r i l y , i t examines t h e h y p o t h e s i s t h a t more d i v e r s e f l o r a l communities h o s t more d i v e r s e f a u n a l communities (Group 2 ) . Z a r e t (1982) deems Group 3 hypotheses t r i v i a l because t h e impetus f o r d i v e r s i t y - s t a b i l i t y q u e s t i o n s came from o b s e r v e d l a t i t u d i n a l d i v e r s i t y g r a d i e n t s . There a r e f e w , i f any s t u d i e s , however, t h a t u n e q u i v o c a l l y demonstrate such t r e n d s o r t h a t a t t e m p t t o e l u c i d a t e the mechanisms p r o d u c i n g such a t r e n d . More s p e c i f i c a l l y , many s t u d i e s o f s a l i n e l a k e s s u g g e s t t h a t i n c r e a s i n g s a l i n i t y i s accompanied by d e c r e a s i n g community d i v e r s i t y , b u t none has r i g o r o u s l y t e s t e d the h y p o t h e s i s o r examined i t i n l i g h t o f t h e d i v e r s i t y - s t a b i l i t y c o n c e p t . The h y p o t h e s i s t h a t s t a b l e e n v i r o n m e n t s have more d i v e r s e communities than l e s s s t a b l e ones can be expanded i n t o an even l a r g e r number o f s u b - h y p o t h e s e s depending on e x a c t l y how " d i v e r s i t y " and " s t a b i l i t y " a r e d e f i n e d . E n v i r o n m e n t a l s t a b i l i t y can be d e f i n e d as t h e s e v e r i t y , v a r i a b i l i t y , or p r e d i c t a b i l i t y o f a b i o t i c f a c t o r s . Hence, t h e h y p o t h e s i s assumes t h a t l e s s d i v e r s e communities a r e found i n h a b i t a t s w i t h s e v e r e a b i o t i c c o n d i t i o n s , v a r i a b l e c o n d i t i o n s , u n p r e d i c t a b l e c o n d i t i o n s , o r c o m b i n a t i o n s t h e r e o f . Community d i v e r s i t y g e n e r a l l y r e f e r s t o t h e s t r u c t u r a l c o m p l e x i t y o f a community i n terms o f t h e number o r r e l a t i v e abundance o f s p e c i e s o r morphs. D i v e r s i t y can be measured o r e s t i m a t e d 5 from community c e n s u s e s ; t h i s t o p i c w i l l be d i s c u s s e d i n more d e t a i l i n Chapter 2 . I make no a t t e m p t t o examine community s t a b i l i t y as i t cannot be measured d i r e c t l y , i t s p r e s e n c e can o n l y be i n f e r r e d from changes i n t h e community t h r o u g h t i m e . Community s t a b i l i t y can be d e f i n e d i n a v a r i e t y o f ways, b u t u s u a l l y r e f e r s t o the tendancy o f a system t o remain n e a r , or r e t u r n t o , an e q u i l i b r i u m p o i n t a f t e r a p e r t u r b a t i o n ( O r i a n s , 1 9 7 5 ) . 6 STUDY S I T E The s t u d y s i t e , B e c h e r ' s P r a i r i e , i s i n t h e C h i l c o t i n P l a t e a u r e g i o n of c e n t r a l B r i t i s h C o l u m b i a : west o f the F r a s e r R i v e r and near R i s k e Creek ( F i g . 1 ) . E n v i r o n m e n t a l parameters such as p h y s i c a l l o c a t i o n , a l t i t u d e and c l i m a t e a r e s i m i l a r f o r a l l l a k e s . The l a k e s a r e a t 950 m e l e v a t i o n and l i e 250 t o 2000 m a p a r t , w i t h i n a 5 km r a d i u s , among many o t h e r s m a l l water b o d i e s i n p i n e - a s p e n p a r k l a n d . The c l i m a t e i s c h a r a c t e r i z e d by r e l a t i v e l y low annual t e m p e r a t u r e s w i t h l a r g e s e a s o n a l and d a i l y f l u c t u a t i o n s (-11 .6 and 13.7 °C mean d a i l y t e m p e r a t u r e f o r J a n u a r y and J u l y r e s p e c t i v e l y ) , and low p r e c i p i t a t i o n (35 cm a n n u a l l y ) (Cannings e t a K , 1 9 8 0 ) . The l a k e s a r e under i c e - c o v e r from m i d - O c t o b e r t o l a t e A p r i l (Cannings & S c u d d e r , 1 9 7 8 ) . The water l e v e l i s r e l a t i v e l y s t a b l e d u r i n g any one season as l a k e s l a c k i n l e t o r o u t l e t s t r e a m s , a r e not c o n n e c t e d w i t h t h e main d r a i n a g e s y s t e m , and hence a r e not s u b j e c t t o f l o o d i n g (Munro, 1 9 4 5 ) . The e i g h t study l a k e s v a r y both i n s i z e and c h e m i c a l c h a r a c t e r : l a r g e r , more s a l i n e l a k e s a r e g e n e r a l l y dominated by NaHC03 w h i l e i n s m a l l e r , f r e s h e r ones MgC03 o f t e n p r e d o m i n a t e s (Cannings & S c u d d e r , 1 9 7 8 ) . D e t a i l e d p h y s i c a l and c h e m i c a l p r o p e r t i e s o f t h e w a t e r b o d i e s a r e g i v e n i n Topping & Scudder ( 1 9 7 7 ) . A l l are a t h a l a s s i c i n i o n i c o r i g i n , as d e f i n e d by B a y l y ( 1 9 6 7 ) , i . e . they have no p r e s e n t o r h i s t o r i c a s s o c i a t i o n s w i t h a m a r i n e e n v i r o n m e n t [ s e e W i l l i a m s (1981a) f o r f u r t h e r d i s c u s s i o n o f t e r m s ] . The c o m p l e x i t y o f the g e o l o g y i n c e n t r a l B r i t i s h Columbia and g e n e r a l l a c k o f g e o l o g i c a l d a t a from the study a r e a p r e c l u d e a d e t a i l e d g e o l o g i c a l i n t e r p r e t a t i o n o f l a k e w a t e r c h e m i s t r y (Topping & S c u d d e r , 1977) . S u r f a c e w a t e r s a l i n i t y u s u a l l y v a r i e s s e a s o n a l l y and a n n u a l l y both w i t h i n and between l a k e s . These v a r i a t i o n s a r e owing t o changes i n t h e 7 F i g . 1 . Study a r e a . Numbers 1-8 = l a k e s s t u d i e d : 1 = Box 2 7 , 2 = B a r k l e y L . , 3 = Near O p p o s i t e C r e s c e n t , 4 = Rock L . , 5 = L. J a c k s o n , 6 = L. L y e , 7 = Round-Up L . , 8 = Barnes L. 8 volume and t i m e o f s p r i n g r u n - o f f , and t o d i f f e r e n t amounts o f m i x i n g between s u r f a c e and l o w e r , more s a l i n e w a t e r ( S c u d d e r , 1969a; Topping & S c u d d e r , 1 9 7 7 ) . There a r e d i f f e r e n c e s i n the v e r t i c a l d i s t r i b u t i o n o f t e m p e r a t u r e i n d i f f e r e n t l a k e s . In g e n e r a l , l a k e s a r e homeothermal i n t h e upper 2 m, and l a k e s s h a l l o w e r than 3-4 m, o r w i t h c o n d u c t i v i t e s l e s s than 5500 }iS, a r e e s s e n t i a l l y i s o t h e r m a l t h r o u g h o u t ( S c u d d e r , 1969a; Topping & S c u d d e r , 1977) . The e i g h t l a k e s examined i n t h i s study a r e a l l permanent, l a c k f i s h p r e d a t o r s , and were s p e c i f i c a l l y chosen t o o b t a i n a wide range o f s a l i n i t i e s : i n 1978 mean c o n d u c t i v i t y ranged from 56 t o 13115 JJS cm~l a t 25 ° C . F o r c o n v e n i e n c e , l a k e s were numbered from 1 t o 8 i n o r d e r o f i n c r e a s i n g s a l i n i t y ( F i g . 1 ) . A l l l a k e s a r e s i t u a t e d i n d e p r e s s i o n s i n t h e r o l l i n g p r a i r i e ( P l a t e 1 ) . The two most f r e s h w a t e r l a k e s s t u d i e d are both s m a l l , s h a l l o w , and have e x t r e m e l y s o f t s h o r e l i n e s ( P l a t e 2 ) , whereas o t h e r s have f i r m m a r g i n s , o f t e n w i t h p r e c i p i t a t e d s a l t s ( P l a t e 3 ) . P l a t e 1 . 1 4 . i x . 8 4 . Lake 2 ( B a r k l e y L . ) s i t u a t e d i n a d e p r e s s i o n i n the r o l l i n g p r a i r i e . P l a t e 2 . 1 4 . i x . 8 4 . Lake 2 ( B a r k l e y L . ) w i t h a s h a l l o w s o f t s h o r e l i n e . 10 1 2 . v i i i . 8 4 . Lake 7 (Round-Up) w i t h a f i r m g r a v e l l y bottom and w h i t e p r e c i p i t a t e d s a l t s on emerged r o c k s . 11 CHAPTER 1: PHYSIOCHEMICAL FEATURES Introduction E c o l o g i c a l s t u d i e s o f a q u a t i c fauna must c o n s i d e r the p h y s i c a l and c h e m i c a l n a t u r e o f t h e w a t e r s as w e l l as t h e fauna because a q u a t i c ecosystems a r e i n t i m a t e l y c o u p l e d w i t h and a f f e c t e d by t h e a b i o t i c e n v i r o n m e n t ( W i l l i a m s , 1 9 6 7 ) . T h i s study i s c o n c e r n e d w i t h f a u n a l community d i f f e r e n c e s i n a s a l i n e l a k e s e r i e s and t h e p h y s i o c h e m i c a l ( o r o t h e r ) f a c t o r s t h a t c o n t r i b u t e t o t h e s e d i f f e r e n c e s . The o b j e c t i v e o f t h i s f i r s t c h a p t e r i s t o c h a r a c t e r i z e t h e p h y s i o c h e m i c a l p r o p e r t i e s o f the study l a k e s . A l t h o u g h the main d i f f e r e n c e between study l a k e s i s s a l i n i t y , a v a r i e t y o f a b i o t i c f a c t o r s c o u l d i n f l u e n c e t h e b i o t a . The s t u d y l a k e s a r e a l l c l o s e enough t o g e t h e r t h a t they have t h e same g e o l o g i c a l o r i g i n , a r e a t t h e same a l t i t u d e , and a r e s u b j e c t t o t h e same c l i m a t e . C o n s e q u e n t l y , t h e s e f a c t o r s , o f t e n s i g n i f i c a n t i n l a k e m e t a b o l i s m ( H u t c h i n s o n , 1957; W e t z e l , 1 9 7 5 ) , were not c o n s i d e r e d w i t h r e s p e c t t o d i f f e r e n c e s i n t h e b i o t a . L o c a l f a c t o r s such as w a t e r t e m p e r a t u r e , c h e m i s t r y and b a s i n morphometry, however, may v a r y and a f f e c t the b i o t a , and t h e r e f o r e were examined. Temperature i s a key e n v i r o n m e n t a l f a c t o r d i r e c t l y i n f l u e n c i n g l i f e - h i s t o r y p a t t e r n s o f a q u a t i c a n i m a l s , and i n d i r e c t l y i n f l u e n c i n g t h e i r food s u p p l y t h r o u g h changes i n the p h y t o p l a n k t o n community. Sweeney (1984) p r o v i d e s an e x c e l l e n t r e v i e w o f t h e l i f e - h i s t o r y l i t e r a t u r e on a q u a t i c i n s e c t s ; H u t c h i n s o n (1967) r e v i e w s c r u s t a c e a n z o o p l a n k t o n and p h y t o p l a n k t o n . T h e r e f o r e , the p o s s i b i l i t y o f water t e m p e r a t u r e d i f f e r e n c e s a f f e c t i n g b i o l o g i c a l communities i n t h e study l a k e s must be c o n s i d e r e d . 12 Water s a l i n i t y , i n terms o f both the t o t a l and p r o p o r t i o n a t e c o n c e n t r a t i o n s o f i o n s , v a r i e s among l a k e s and can i n f l u e n c e t h e m e t a b o l i s m of many organisms through o s m o t i c s t r e s s and c o n s e q u e n t l y a f f e c t community s t r u c t u r e . Every organism has a c r i t i c a l range o f s a l t c o n c e n t r a t i o n s w i t h i n which t h e i n t e g r i t y o f b i o c h e m i c a l mechanisms o f t h e organism i s e n s u r e d ; v a r i a t i o n s above o r below t h i s range can be f a t a l . Some organisms a v o i d the problems o f o s m o t i c s t r e s s by b e i n g t o l e r a n t o f a wide range o f c o n d i t i o n s , such as most z o o p l a n k t o n ( H u t c h i n s o n , 1967; B r a n d , 1 9 8 1 ) , o r by r e g u l a t i n g t h e i r i n t e r n a l e n v i r o n m e n t t h r o u g h s e l e c t i v e a b s o r p t i o n and e x c r e t i o n o f i o n s , as i n s e v e r a l d i p t e r a n s p e c i e s ( P h i l l i p s . , 1978) and b r i n e shrimp ( C r o g h a n , 1958a; 1958b; 1958c; 1958d; Geddes, 1975a; 1975b; 1 9 7 5 c ) . A l t h o u g h s a l i n i t y a c t s a t the o r g a n i s m a l l e v e l , i t s e f f e c t s may be m a n i f e s t on an e c o l o g i c a l s c a l e , as many s t u d i e s have i n d i c a t e d ( B e a d l e , 1943; Rawson & M o o r e , 1944; M o o r e , 1952; B a y l y & W i l l i a m s , 1966; S c u d d e r , 1969a; S a v a g e , 1971; R e y n o l d s , 1975; Cannings & S c u d d e r , 1978; W i l l i a m s , 1978; Cannings et _ a K , 1980; Geddes e t _aj[., 1981; Timms, 1981; 1983; Brock & S h i e l , 1 9 8 3 ) . Few s t u d i e s , however, have examined t h e r o l e o f i o n i c p r o p o r t i o n s t o the e c o l o g y o f f a u n a l groups a l t h o u g h they may w e l l be i m p o r t a n t as s u g g e s t e d by B a y l y ( 1 9 6 9 ) , P a t e r s o n & Walker (1974) and W i l l i a m s ( 1 9 8 1 b ) . A l t h o u g h t h i s i n v e s t i g a t i o n does not deal d i r e c t l y w i t h t h e p h y s i o l o g i c a l p r o c e s s e s o f o s m o t i c r e g u l a t i o n and t o l e r a n c e , s a l i n i t y i s o b v i o u s l y a f a c t o r i m p o r t a n t t o a q u a t i c c o m m u n i t i e s . One o f the e c o l o g i c a l q u e s t i o n s a d d r e s s e d i n t h i s study r e q u i r e s t h a t s a l i n i t y be e x p r e s s e d i n terms o f e n v i r o n m e n t a l s t a b i l i t y , as mentioned i n the General I n t r o d u c t i o n . S a l i n i t y i s r e a d i l y q u a n t i f i e d i n terms o f the t h r e e components o f e n v i r o n m e n t a l s t a b i l i t y : s e v e r i t y as mean o r maximum s a l i n i t y , v a r i a b i l i t y as the range o r d e v i a t i o n w i t h i n one y e a r , and 13 p r e d i c t a b i l i t y as the v a r i a t i o n between y e a r s . T h i s i s a c o n v e n i e n t way t o q u a n t i f y t h e s e a s o n a l and annual v a r i a t i o n s i n s a l i n i t y known t o o c c u r i n the study l a k e s ( S c u d d e r , 1969a; Topping & S c u d d e r , 1977) . The morphology o f l a k e b a s i n s can have i m p o r t a n t e f f e c t s on b i o t i c communities i n terms o f p r o d u c t i v i t y , t h e s p e c i e s / a r e a phenomenon, and t h e r e l a t i v e c o n t r i b u t i o n o f l i t t o r a l p r o c e s s e s t o t h e whole l a k e . The shape of l a k e b a s i n s i s o f t e n r e f l e c t e d by p r o d u c t i v i t y : s t e e p s i d e d b a s i n s a r e u s u a l l y deep and u n p r o d u c t i v e whereas s h a l l o w d e p r e s s i o n s w i t h a g r e a t e r p e r c e n t a g e c o n t a c t of water w i t h the sediments g e n e r a l l y e x h i b i t moderate t o h i g h p r o d u c t i v i t y ( W e t z e l , 1 9 7 5 ) . A number o f s t u d i e s have f o c u s e d on the i m p o r t a n c e o f l a k e morphometry t o l a k e p r o d u c t i v i t y (Rawson, 1952; 1955; Hayes & A n t h o n y , 1 9 6 4 ) , so I i n c l u d e d b a s i n shape i n l a k e c h a r a c t e r i z a t i o n . S e c o n d l y , t h e t h e o r y o f i s l a n d b i o g e o g r a p h y p o s t u l a t e s t h a t t h e s i z e o f an i s l a n d i s d i r e c t l y p r o p o r t i o n a l t o t h e number of i n h a b i t i n g s p e c i e s (MacArthur & W i l s o n , 1 9 6 7 ) , and i t has been shown t o be t r u e i n some c a s e s [ s e e summary and e a r l y r e f e r e n c e s i n S i m b e r l o f f ( 1 9 7 4 ) ; F r y e r (1985) f o r a more r e c e n t e x a m p l e ] . The l a k e s on B e c h e r ' s P r a i r i e can be c o n s i d e r e d i s l a n d s o f v a r i o u s s i z e s s i t u a t e d c l o s e enough t o g e t h e r t h a t a l l s p e c i e s have equal p o t e n t i a l f o r d i s p e r s a l t o a l l l a k e s , as suggested f o r C o r i x i d a e ( S c u d d e r , 1 9 6 9 b ) . T h e r e f o r e , I examined l a k e s i z e w i t h r e s p e c t t o f a u n a l community s t r u c t u r e . T h i r d l y , b i o t i c communities can be i n f l u e n c e d by t h e r e l a t i v e c o n t r i b u t i o n o f l i t t o r a l p r o c e s s e s t o the whole l a k e , e s p e c i a l l y i n s m a l l l a k e s such as t h o s e i n t h i s study ( W e s t l a k e , 1963; 1 9 6 5 ) . L i t t o r a l f l o r a c o n s t i t u t e a major s i t e f o r the s y n t h e s i s o f o r g a n i c m a t t e r which c o n t r i b u t e s s i g n i f i c a n t l y t o t h e p r o d u c t i v i t y o f l a k e s and t o the r e g u l a t i o n o f m e t a b o l i s m o f t h e whole l a k e ecosystem ( K o w a l c z e w s k i , 1975; W e t z e l , 1 9 7 5 ) . Morphometric components of a l a k e 14 d e t e r m i n e t h e p o t e n t i a l f o r l i t t o r a l p r o c e s s e s t o i n f l u e n c e the e c o s y s t e m , and s h o u l d be c o n s i d e r e d a p o s s i b l e i n f l u e n c e on b i o t i c c o m m u n i t i e s . Materials and Methods There a r e many ways t o d e s c r i b e p h y s i c a l and c h e m i c a l a s p e c t s o f a l a k e , and I used c o m p o s i t e measures o f t h e environment i n the form o f s i n g l e n u m e r i c a l parameters and p i c t o r i a l dendograms produced by m u l t i v a r i a t e methods. The n e c e s s a r y raw d a t a f o r t h e s e c h a r a c t e r i z a t i o n s were assembled from a v a r i e t y o f s o u r c e s : u n p u b l i s h e d c h e m i c a l and t e m p e r a t u r e d a t a c o l l e c t e d by R . A . , R . J . & S . G . Cannings i n 1978, p h y s i o c h e m i c a l d a t a from 1966 p u b l i s h e d by Topping & Scudder ( 1 9 7 7 ) , and some o f my own map measurements. TEMPERATURE. Water t e m p e r a t u r e was measured a t 1 m depth w i t h Ryan model-D underwater c o n t i n u o u s c h a r t r e c o r d e r s from May t o O c t o b e r , 1978. CHEMISTRY. Among the s i m p l e s t measures o f s a l i n i t y a r e t o t a l i o n c o n c e n t r a t i o n , TDS ( t o t a l d i s s o l v e d s o l i d s ) , and c o n d u c t i v i t y . T o t a l i o n c o n c e n t r a t i o n i s t h e sum o f t h e c o n c e n t r a t i o n s o f t h e e i g h t major c a t i o n s and a n i o n s , C a , Mg, N a , K , H C O 3 , C O 3 , SO4 and C I , a n a l y z e d i n d e p e n d e n t l y [ s e e T o p p i n g & Scudder (1977) f o r t e c h n i q u e s ] ; TDS i s an e s t i m a t e o f a l l i n o r g a n i c m a t e r i a l s d i s s o l v e d i n w a t e r ; c o n d u c t i v i t y ( s p e c i f i c c o n d u c t a n c e ) i s a measure o f the r e s i s t a n c e o f a s o l u t i o n t o e l e c t r i c c u r r e n t . A study o f 32 B . C . l a k e s , i n c l u d i n g t h o s e i n t h i s s t u d y , showed c o n d u c t i v i t y t o be a s i g n i f i c a n t l i n e a r f u n c t i o n o f TDS and a s i g n i f i c a n t c u r v i l i n e a r f u n c t i o n o f t o t a l i o n c o n t e n t (Topping & S c u d d e r , 1 9 7 7 ) . C o n s e q u e n t l y , t h i s study c o n s i d e r e d o n l y c o n d u c t i v i t y t o i n d i c a t e s a l i n i t y as i t was the most c o n v e n i e n t and r e a d i l y a v a i l a b l e measure. 15 C o n d u c t i v i t y a t 1 m depth was measured w i t h a Radiometer CD 2 c o n d u c t i v i t y meter m o n t h l y , from May t o October 1978. One drawback o f t o t a l s a l i n i t y measures i s t h a t i n d i v i d u a l i o n s l o s e t h e i r unique i d e n t i t y when anonymously lumped t o g e t h e r . To a v o i d t h i s problem I used m u l t i v a r i a t e o r d i n a t i o n t e c h n i q u e s t h a t c o n s i d e r both i o n i c c o m p o s i t i o n and c o n c e n t r a t i o n s i m u l t a n e o u s l y and e q u a l l y , y e t produce a q u a n t i t a t i v e l i n e a r arrangement o f l a k e s . O r d i n a t i o n i s a mathematical t r e a t m e n t d e s i g n e d t o produce an o b j e c t i v e n u m e r i c a l arrangement o f samples ( l a k e s ) r e f l e c t i n g t h e s i m i l a r i t y o f t h e i r c o n s t i t u e n t v a r i a b l e s ( i o n s ) . I t aims t o r e s o l v e t h e t o t a l v a r i a t i o n i n a s e t o f v a r i a b l e s i n t o l i n e a r l y independent c o m p o s i t e v a r i a b l e s which s u c c e s s f u l l y a c c o u n t f o r maximal v a r i a b i l i t y i n t h e d a t a ( S i n h a , 1977) . In t h i s way one can o b j e c t i v e l y examine whether most o f the i n f o r m a t i o n i n the d a t a can be e x p r e s s e d by a few a x e s . The f i r s t a x i s c o n t a i n s t h e l a r g e s t s h a r e o f s t a t i s t i c a l v a r i a t i o n i n t h e o r i g i n a l d a t a ; the second and subsequent components a r e unique and u n c o r r e l a t e d w i t h p r e c e d i n g o n e s , and e x p r e s s d e c r e a s i n g amounts o f t o t a l v a r i a t i o n i n t h e d a t a (Gates e t a]_., 1 9 8 3 ) . Component s c o r e s f o r each l a k e on t h e s e axes can then be used as a c o m p o s i t e measure o f s a l i n i t y i n terms o f e n v i r o n m e n t a l s e v e r i t y , b u t not v a r i a b i l i t y o r p r e d i c t a b i l i t y u n l e s s an element o f t i m e i s i n c l u d e d . In a d d i t i o n , i t i s p o s s i b l e t o d e t e r m i n e which v a r i a b l e s ( i o n s ) combine t o d e f i n e each component by l o o k i n g f o r c o r r e l a t i o n s between i n d i v i d u a l i o n s and component s c o r e s . Any a s s o c i a t i o n s between component s c o r e s and b i o t i c parameters might g i v e some i n d i c a t i o n o f which i o n s a r e p h y s i o l o g i c a l l y l i m i t i n g t o s p e c i e s . Of the many o r d i n a t i o n t e c h n i q u e s a v a i l a b l e , p r i n c i p a l components a n a l y s i s ( P C A ) , as p r o v i d e d by BMDP ( F r a n e e t j i K , 1 9 8 3 ) , was used t o 16 o r d i n a t e the l a k e s from t h e i r i o n i c c o m p o s i t i o n . The n e c e s s a r y d a t a on i o n c o n c e n t r a t i o n s were p r e d i c t e d f o r 1978 from v a l u e s i n Topping & Scudder ( 1 9 7 7 ) . G i v e n t h a t c o n d u c t i v i t y i s c l o s e l y r e l a t e d t o t o t a l i o n c o n t e n t (Topping & S c u d d e r , 1 9 7 7 ) , and s i n c e the r e l a t i v e p r o p o r t i o n of i o n s i n each l a k e i s c o m p a r a t i v e l y s i m i l a r from y e a r t o y e a r ( S c u d d e r , p e r s o n a l c o m m u n i c a t i o n ) , i t i s p o s s i b l e t o p r e d i c t i n d i v i d u a l i o n c o n c e n t r a t i o n s i n any o t h e r y e a r from a measure o f c o n d u c t i v i t y . P r e d i c t e d c o n c e n t r a t i o n s o f the e i g h t major i o n s i n each l a k e c o n s t i t u t e d the raw d a t a m a t r i x from which a c o v a r i a n c e m a t r i x was c a l c u l a t e d and s u b j e c t e d t o PCA. A c o v a r i a n c e m a t r i x was used because a l l v a r i a b l e s a r e i n the same u n i t s , and because t h i s m a t r i x e x t r a c t s more i n f o r m a t i o n than one based on c o r r e l a t i o n s o n l y . MORPHOMETRY. The s i m p l e s t and perhaps b e s t c o m p o s i t e measure o f l a k e s i z e i s mean d e p t h , c a l c u l a t e d as t h e r a t i o o f l a k e volume t o s u r f a c e a r e a . Morphometric measures o f l a k e s u r f a c e a r e a , volume, and mean depth were t a k e n from T o p p i n g & Scudder ( 1 9 7 7 ) . The morphometeric measure o f s h o r e l i n e development r e f l e c t s p o t e n t i a l f o r the development o f l i t t o r a l communities i n p r o p o r t i o n t o l a k e volume ( W e t z e l , 1 9 7 5 ) , and hence i t s c o n t r i b u t i o n t o t h e whole l a k e . V a l u e s f o r s h o r e l i n e development are o n l y comparable among l a k e s i f a r e a i s c o n s t a n t ( H u t c h i n s o n , 1 9 5 7 ) . Because l a k e a r e a i s not c o n s t a n t among l a k e s , I m o d i f i e d t h e s h o r e l i n e development f o r m u l a so d i f f e r e n t l a k e s would be c o m p a r a b l e . S h o r e l i n e development (D[_) i s the r a t i o o f l a k e p e r i m e t e r ( s h o r e l e n g t h , L) t o the c i r c u m f e r e n c e o f a c i r c l e o f a r e a equal t o t h a t o f the l a k e . When c o r r e c t e d f o r a r e a (A) the r a t i o (D|_/0 i s as f o l l o w s : DLA = L 17 High v a l u e s o f D[_A i n d i c a t e h i g h p o t e n t i a l f o r l i t t o r a l p r o c e s s e s t o a f f e c t the whole l a k e , and v i c e v e r s a f o r low v a l u e s . I measured s h o r e l i n e l e n g t h w i t h a c h a r t o m e t e r on a 1 : 5 0 , 0 0 0 map and n o r m a l i z e d r e s u l t s a c c o r d i n g t o Hakanson ( 1 9 8 1 ) . These d a t a were then used t o c a l c u l a t e s h o r e l i n e development (D[_) and t h e r a t i o o f D|_ t o a r e a (DL /0. CLASSIFICATION. M u l t i v a r i a t e c l a s s i f i c a t i o n t e c h n i q u e s , l i k e o r d i n a t i o n , p e r m i t a s i m u l t a n e o u s and equal e x a m i n a t i o n o f both i o n i c c o m p o s i t i o n and c o n c e n t r a t i o n . These t e c h n i q u e s group s i m i l a r e n t i t i e s ( l a k e s ) t o g e t h e r i n c l u s t e r s by means o f s i m i l a r i t y o r d i s s i m i l a r i t y i n d i c e s . H i e r a r c h i c a l c l a s s i f i c a t i o n s a r r a n g e groups i n t o h i e r a r c h i c a l dendrograms i n d i c a t i n g r e l a t i o n s h i p s among g r o u p s . The unweighted p a i r - g r o u p s method u s i n g a r i t h m e t i c a v e r a g e s , UPGMA, as p r o v i d e d by NT-SYS ( R o h l f e t a l _ . , 1980) and recommended by Sneath & S o k a l ( 1 9 7 3 ) , was used t o c l u s t e r t h e e i g h t l a k e s . T h i s method f o l l o w s a p o l y t h e t i c a g g l o m e r a t i v e h i e r a r c h i c a l s t r a t e g y c l u s t e r i n g s i m i l a r l a k e s t o g e t h e r and a r r a n g i n g the groups i n t o a h i e r a r c h i c a l dendrogram. E u c l i d e a n d i s t a n c e , a d i s s i m i l a r i t y measure, was used t o group l a k e s as i t tended t o produce t h e l e a s t amount o f d i s t o r t i o n when n u m e r i c a l d a t a were c o n v e r t e d t o p i c t o r i a l dendrograms. The c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t (Sokal & R o h l f , 1962; R o h l f , 1974; Romesburg, 1984) was used t o e v a l u a t e the amount o f d i s t o r t i o n a s s o c i a t e d w i t h c l u s t e r s . T h i s t e c h n i q u e computes the c o r r e l a t i o n between the o r i g i n a l s i m i l a r i t y c o e f f i c i e n t s , on which t h e dendrogram i s b a s e d , and t h e c o p h e n e t i c v a l u e s which a r e a m a t r i x o f coded s i m i l a r i t y v a l u e s e x t r a c t e d from t h e dendrogram. A p e r f e c t c o r r e l a t i o n (r=1.00) between t h e o r i g i n a l s i m i l a r i t y c o e f f i c i e n t s and c o p h e n e t i c v a l u e s i n d i c a t e s no d i s t o r t i o n on c o n v e r t i n g d a t a i n t o a dendrogram. A c o r r e l a t i o n o f r=0.80 i s u s u a l l y c o n s i d e r e d t h e c u t - o f f f o r a c c e p t a b l e 18 dendrograms, a l t h o u g h t h e r e may s t i l l be some d i s t o r t i o n (Romesburg, 1 9 8 4 ) . Two dendrograms were drawn, the f i r s t from c o n c e n t r a t i o n s o f t h e e i g h t major i o n s a l o n e , and the second w i t h t h e a d d i t i o n o f t o t a l c o n d u c t i v i t y and s i x morphometric v a r i a b l e s : s u r f a c e a r e a , volume, mean d e p t h , s h o r e l i n e l e n g t h , s h o r e l i n e d e v e l o p m e n t , and t h e s h o r e l i n e d e v e l o p m e n t / a r e a r a t i o . Results and Discussion TEMPERATURE. E v i d e n c e s u g g e s t s t h a t t e m p e r a t u r e i s n o t a f a c t o r a f f e c t i n g t h e d i s t r i b u t i o n o f o r g a n i s m s among l a k e s as a l l e i g h t l a k e s had s i m i l a r t e m p e r a t u r e p r o f i l e s a t 1 m d e p t h . S i m i l a r r e s u l t s were found by Scudder ( 1 9 6 9 a ) , J a n s s o n & Scudder ( 1 9 7 4 ) , and Cannings e t al_. ( 1 9 8 0 ) . F i g . 2 p r e s e n t s a p l o t o f t e m p e r a t u r e s r e c o r d e d i n Lake 1 showing marked s e a s o n a l v a r i a t i o n , w i t h a r e c o r d e d minimum o f 6 ° C and maximum o f 23 ° C , and i s r e p r e s e n t a t i v e o f t e m p e r a t u r e p r o f i l e s i n t h e o t h e r study l a k e s . CHEMISTRY. Of the t h r e e components o f e n v i r o n m e n t a l s t a b i l i t y , ( s e v e r i t y , v a r i a b i l i t y and p r e d i c t a b i l i t y ) , o n l y s e v e r i t y can be r e p r e s e n t e d by s a l i n i t y . T h i s study does not examine the e f f e c t s o f e n v i r o n m e n t a l p r e d i c t a b i l i t y as b i o l o g i c a l data were a v a i l a b l e f o r o n l y one s e a s o n , a l t h o u g h e v i d e n c e s u g g e s t s t h a t s a l i n i t y has g r a d u a l l y i n c r e a s e d o v e r t h e p a s t 20 y e a r s ( T a b l e 1 ) . S u r f a c e w a t e r s a l i n i t y v a r i e d s e a s o n a l l y , g e n e r a l l y i n c r e a s i n g from s p r i n g t o autumn, b u t i t i s d i f f i c u l t t o s e p a r a t e e n v i r o n m e n t a l v a r i a b i l i t y from s e v e r i t y as mean, range and maximum c o n d u c t i v i t y a r e a l l h i g h l y c o r r e l a t e d ( F i g . 3 ) . Mean c o n d u c t i v i t y , r a n g i n g from 56 \iS i n Lake 1 t o 13115 jiS i n Lake 8 , was used t o r e p r e s e n t e n v i r o n m e n t a l s t a b i l i t y i n the form o f s e v e r i t y . 19 F i g . 2 . D a i l y t e m p e r a t u r e range i n Lake 1 (Box 27) a t 1 m depth i n 1978. F i g . 3 . Seasonal c o n d u c t i v i t y (uS c m ~ l , 25 ° C ) i n each l a k e i n o r d e r o f i n c r e a s i n g s a l i n i t y . (See F i g . 1 f o r l a k e names; see Appendix A f o r n u m e r i c a l v a l u e s ) . Log conductivity ro co • o# • o» • o» • c» • o» 3 CD Temperature (°C) -£ 9 9 £-l\3 Ol ro o 00 CO O 21 T a b l e 1 . Annual v a r i a t i o n s i n mean s u r f a c e c o n d u c t i v i t y o f study l a k e s . (uS cm" •1, 25 ° C ) . (See F i g . 1 f o r l a k e names) • y e a r Lake 1963 1966 1967 1969 1972 1978 1983 1984 1 40 40 56 42 65 2 592 720 932 740 956 3 810 830 1437 1443 1762 4 1496 1500 2759 2723 3038 5 2766 3230 4544 4443 5014 6 7125 5350 6448 6548 6550 8281 8067 9348 7 6885 6890 10365 10667 11942 8 13000 8343 10938 11816 11820 13115 12117 14580 T a b l e 2 . Mean c o n d u c t i v i t y and p r e d i c t e d i o n c o n c e n t r a t i o n s i n 1978. (See F i g . 1 f o r l a k e names). mean c o n d u c t i v i t y mi H i e q u i v a l e n t s per l i t e r  Lake (uS cm-1 2 5 ° C ) Na K Ca Mg CO3 HCO3 CI SO4 1 56 0 . 1 3 0 . 1 4 0 . 3 2 0 . 2 2 0 . 1 4 0 . 4 1 0.14 0 . 1 3 2 932 3 . 0 9 0 . 9 8 0 . 6 0 8 . 0 8 0 . 6 9 9 . 0 2 0 . 3 8 0 . 6 3 3 1437 5 . 9 8 1 . 0 6 1.72 7 . 8 1 1 . 4 4 11.39 0 . 6 2 2 . 3 8 4 2759 2 7 . 5 0 1 .81 1.14 3 . 2 1 7.97 2 2 . 7 8 2 . 9 0 0 . 3 3 5 4544 2 6 . 6 0 2 . 5 1 2 . 3 3 2 6 . 5 3 3 . 4 2 9 . 8 6 5 . 9 3 3 9 . 2 5 6 8281 8 8 . 0 5 6 . 4 6 0 . 9 4 3.72 19.94 4 9 . 9 6 27.91 8 . 8 4 7 10365 110.86 7 . 9 0 0 . 9 0 4 . 5 9 2 2 . 3 7 4 8 . 4 9 3 8 . 2 4 17.07 8 13115 145.59 14.87 0 . 4 8 3.27 5 5 . 0 1 5 9 . 8 5 4 1 . 4 0 2 8 . 6 8 22 T a b l e 3 . P r i n c i p a l component s c o r e s f o r l a k e s and i o n s , p l u s P e a r s o n ' s p r o d u c t moment c o r r e l a t i o n o f i o n PC s c o r e s w i t h i o n c o n c e n t r a t i o n s , c a l c u l a t e d from data i n T a b l e 2 . ( * * = p < 0 . 0 1 ) . (See F i g . 1 f o r l a k e names). Lake PCI PC2 i o n PCI r PC2 r 1 - 0 . 9 2 7 - 0 . 4 8 0 Na 5 6 . 0 0 1 . 0 0 * * 0.11 0 . 0 0 2 - 0 . 8 4 4 - 0 . 3 2 8 HC03 2 2 . 2 0 0 . 9 7 * * - 3 . 5 7 - 0 . 1 6 3 - 0 . 7 8 7 - 0 . 2 7 5 CI 17.80 0 . 9 9 * * - 0 . 3 9 - 0 . 0 2 4 - 0 . 4 1 6 - 0 . 7 0 6 C 0 3 17.70 0 . 9 4 * * - 0 . 2 0 - 0 . 0 1 5 - 0 . 4 4 2 2 . 3 6 1 K 4 . 9 0 0 . 9 7 * * 0 . 3 0 0 . 0 6 6 0 . 6 7 2 - 0 . 6 5 5 S 0 4 7 . 5 2 0 . 5 0 12.90 0 . 8 6 * * 7 1 . 0 3 0 - 0 . 1 6 3 Mg - 1 . 9 1 - 0 . 2 3 7 . 5 8 0 . 9 2 * * 8 1.710 0 . 2 4 6 Ca - 0 . 1 8 - 0 . 2 7 0 . 4 6 0 . 6 8 T a b l e 4 . Morphometric p r o p e r t i e s o f study l a k e s ( a r e a , volume and mean depth d a t a from Topping & S c u d d e r , 1 9 7 7 ) . (See F i g . 1 f o r l a k e names). s u r f a c e mean s h o r e l i n e s h o r e l i n e a r e a volume depth l e n g t h s h o r e l i n e development/ Lake (ha) (m3 x 10 3 ) (m) (m) development a r e a r a t i o 1 4 . 3 0 2 3 . 0 0 . 5 846 1 .15 0.27 2 4 . 5 5 3 2 . 8 0 . 7 - 1184 1.57 0 . 3 5 3 6 . 8 8 9 9 . 2 1 . 4 1022 1 .10 0 . 1 6 4 3 4 . 6 4 3 8 7 . 5 1 .1 3433 1 . 6 5 0 . 0 5 5 5 . 8 1 7 9 . 9 1 . 4 1397 1 . 6 3 0 . 2 8 6 4 6 . 5 2 1283.2 2 . 8 4597 1 . 9 0 0 . 0 4 7 3 0 . 8 4 787.6 2 . 6 2721 1 . 3 8 0 . 0 5 8 17.19 3 4 8 . 4 2 . 0 2626 1 .79 0 . 1 0 23 T a b l e 5 . C o r r e l a t i o n s among a b i o t i c v a r i a b l e s . * = p<0.10; * * = p < 0 . 0 5 ; * * * = p < 0 . 0 1 . v a r i a b l e  V a r i a b l e c o n d u c t i v i t y PCI PC2 mean depth PCI 0.99*** PC2 0.12 0.00 mean depth 0.83** 0.81** -0.02 D LA -0.63* -0.66* 0.38 -0.75** 24 O r d i n a t i o n r e s u l t s i n d i c a t e t h a t v a r i a t i o n s i n s a l i n i t y among t h e e i g h t l a k e s were d e t e r m i n e d p r i m a r i l y by the f o l l o w i n g i o n s : N a , H C O 3 , C I , CO3 and K; the r e m a i n i n g i o n s , S O 4 , Mg and C a , have l i t t l e i n f l u e n c e . Mean c o n d u c t i v i t y v a l u e s and p r e d i c t e d c o n c e n t r a t i o n s o f e i g h t major i o n s based on the r e l a t i v e p r o p o r t i o n s p r e s e n t e d i n Topping & Scudder ( 1 9 7 7 ) , and used i n o r d i n a t i o n , are p r e s e n t e d i n T a b l e 2 . PCA summarized i o n i c c o m p o s i t i o n on two p r i n c i p a l component a x e s , each r e p r e s e n t i n g a d i f f e r e n t group o f i o n s ( T a b l e 3 ) . The f i r s t component a c c o u n t e d f o r 93% o f the t o t a l v a r i a n c e i n t h e d a t a , t h e second added o n l y 5% more, i n d i c a t i n g t h a t t h i s one p r o j e c t i o n more than a d e q u a t e l y r e p r e s e n t s t h e s t r u c t u r e o f t h e d a t a m a t r i x . T a b l e 3 shows c o r r e l a t i o n s between i n d i v i d u a l i o n s and c a l c u l a t e d p r i n c i p a l component s c o r e s . There i s a s i g n i f i c a n t c o r r e l a t i o n o f PCI w i t h N a , H C O 3 , C O 3 , CI and K; PC2 w i t h SO4 and Mg. P r i n c i p a l component s c o r e s c a l c u l a t e d f o r each l a k e a r e a l s o measures o f s a l i n i t y o r e n v i r o n m e n t a l s e v e r i t y . MORPHOMETRY. A l l t h e study l a k e s were of s i m i l a r form d e s p i t e v a r i a t i o n s i n s i z e . Morphometric p r o p e r t i e s o f t h e l a k e s ( T a b l e 4) d i f f e r e d c o n s i d e r a b l y w i t h a r e a s r a n g i n g from 4 . 3 0 t o 4 6 . 5 2 h a , volumes from 2 3 . 0 t o 1283.2 x 10 3 m 3 , and s h o r e l i n e l e n g t h from 846 t o 4597 m. Mean depth measures i n d i c a t e t h a t a l l the b a s i n s were r e l a t i v e l y " s a u c e r s h a p e d " . The l a k e s i n t h i s study were too s m a l l t o use mean depth as an i n d i c a t o r o f l a k e p r o d u c t i v i t y , as i n v e r s e r e l a t i o n s h i p s between mean depth and p r o d u c t i v i t y h o l d o n l y f o r l a r g e l a k e s , and d e t e r i o r a t e among s m a l l l a k e s ( W e t z e l , 1 9 7 5 ) . S h o r e l i n e development v a l u e s i n d i c a t e t h a t l a k e s ranged from a l m o s t c i r c u l a r t o more e l l i p t i c a l , b u t none were very c o n v o l u t e d . Not s u r p r i s i n g l y , s m a l l l a k e s tended t o have h i g h e r v a l u e s o f D L A i n d i c a t i n g a g r e a t e r p o t e n t i a l f o r l i t t o r a l p r o c e s s e s t o a f f e c t t h e 25 whole l a k e . T h i s may w e l l be an i n d i c a t o r o f p r o d u c t i v i t y . RELATIONSHIPS BETWEEN VARIABLES. The e i g h t l a k e s were c h a r a c t e r i z e d a c c o r d i n g t o f i v e c o m p o s i t e a b i o t i c p a r a m e t e r s : mean c o n d u c t i v i t y , two p r i n c i p a l component axes based on i o n i c c o m p o s i t i o n , mean depth and t h e r a t i o o f s h o r e l i n e development t o a r e a . R e l a t i o n s h i p s among t h e s e f i v e v a r i a b l e s a r e shown i n T a b l e 5 , i n terms o f P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t ( S o k a l & R o h l f , 1 9 8 1 ) . Not s u r p r i s i n g l y , c o n d u c t i v i t y i s s i g n i f i c a n t l y c o r r e l a t e d w i t h P C I , b u t n e i t h e r i s c o r r e l a t e d w i t h PC2 as PC2 i s by d e f i n i t i o n o r t h o g o n a l t o any o t h e r component axes produced i n the a n a l y s i s . The r e s u l t s i n T a b l e 5 show a s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n between mean depth and both c o n d u c t i v i t y and P C I . T h i s a s s o c i a t i o n i s p r o b a b l y i n c i d e n t a l r a t h e r than c a u s a l as t h e r e l a t i o n s h i p d i d n o t h o l d when the t e s t was r e p e a t e d u s i n g mean depth and c o n d u c t i v i t y d a t a from 29 l a k e s i n Topping & Scudder (1977) ( r = 0 . 0 1 ; p > 0 . 0 5 ) . T h i s chance a s s o c i a t i o n i s not a s e r i o u s drawback t o the s t u d y . Because a p o s i t i v e c o r r e l a t i o n e x i s t s between l a k e s i z e and s a l i n i t y , a p o s i t i v e a s s o c i a t i o n o f community s t r u c t u r e w i t h mean depth w i l l p r o b a b l y be accompanied by a p o s i t i v e a s s o c i a t i o n w i t h s a l i n i t y , and l i k e w i s e f o r n e g a t i v e a s s o c i a t i o n s . I s l a n d b i o g e o g r a p h y p r e d i c t s a p o s i t i v e r e l a t i o n s h i p between community parameters and l a k e s i z e , b u t a n e g a t i v e r e l a t i o n s h i p i s p r e d i c t e d between community parameters and s a l i n i t y . As i t i s i m p o s s i b l e t o s i m u l t a n e o u s l y have s i g n i f i c a n t b u t o p p o s i t e a s s o c i a t i o n s o f community s t r u c t u r e w i t h both l a k e s i z e and s a l i n i t y , o n l y one h y p o t h e s i s can be s u p p o r t e d a t a t i m e . There i s a s i g n i f i c a n t i n v e r s e r e l a t i o n s h i p between s h o r e l i n e d e v e l o p m e n t / a r e a r a t i o and mean depth which i s not t o t a l l y unexpected as l a k e s i z e i s used t o c a l c u l a t e DLA« DLA tends t o be n e g a t i v e l y 26 a s s o c i a t e d w i t h both c o n d u c t i v i t y and PCI (0.05<p<0.10 i n both c a s e s ) , a l s o p r o b a b l y an i n c i d e n t a l r e l a t i o n s h i p owing t o the p o s i t i v e c o r r e l a t i o n between l a k e s i z e and s a l i n i t y . T h i s a s s o c i a t i o n may be a handicap i n i n t e r p r e t i n g b i o l o g i c a l d a t a as an i n v e r s e r e l a t i o n s h i p i s p r e d i c t e d between community s t r u c t u r e and both s a l i n i t y and D|_ .^ CLASSIFICATION. The n u m e r i c a l c l a s s i f i c a t i o n r e s u l t s o f p r e d i c t e d c h e m i c a l d a t a ( T a b l e 2) and c h e m i c a l p l u s morphometric d a t a ( T a b l e s 2+4) a r e shown i n F i g . 4 . I n " b o t h c a s e s , the c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s a r e g r e a t e r than the c r i t i c a l l e v e l o f a c c e p t a n c e so dendrograms a r e c o n s i d e r e d adequate r e p r e s e n t a t i o n s o f the o r i g i n a l d a t a . In g e n e r a l , the dendrograms i n d i c a t e one major dichotomy o f l a k e t y p e s w i t h two b r a n c h e s : one c o n t a i n i n g s a l i n e Lakes 6 , 7 and 8 ; the o t h e r c o n t a i n i n g t h e more f r e s h w a t e r Lakes 1 t o 5 . In both i n s t a n c e s ( w i t h and w i t h o u t morphometric v a r i a b l e s ) Lakes 6 and 7 a r e grouped t o g e t h e r b e f o r e Lake 8 i s a d d e d . D e t a i l s o f the c l u s t e r i n g o f Lakes 1 t o 5 a r e dependent t o some e x t e n t on whether o r n o t morphometric v a r i a b l e s a r e i n c l u d e d . When l a k e s a r e c l u s t e r e d s o l e l y on t h e b a s i s o f i o n i c c o m p o s i t i o n ( F i g . 4 a ) , Lakes 1 t o 4 a r e a l l t i g h t l y c l u s t e r e d and Lake 5 i s c o n s i d e r e d r e l a t i v e l y d i s s i m i l a r , p r o b a b l y owing t o i t s e x t r a o r d i n a r i l y h i g h c o n c e n t r a t i o n s o f Mg and SO4 ( T a b l e 2 ) . With t h e a d d i t i o n o f morphometric v a r i a b l e s ( F i g . 4 b ) , Lakes 1 and 2 a r e c o n s i d e r e d l e a s t d i s s i m i l a r w i t h Lakes 3 , 4 and 5 s e q u e n t i a l l y added t o the c l u s t e r a t more o r l e s s r e g u l a r i n t e r v a l s . T h i s d i f f e r e n c e i s p r o b a b l y a t t r i b u t a b l e t o t h e i n f l u e n c e o f l a k e s i z e . None o f the r e s u l t i n g dendrograms a r e s u r p r i s i n g even though no a p r i o r i a s s u m p t i o n s about r a n k i n g c o u l d be d e v e l o p e d from t h e o r i g i n a l d a t a . 27 F i g . 4. C l u s t e r a n a l y s i s o f study l a k e s based on d i s s i m i l a r i t y o f (a) 1978 p r e d i c t e d i o n i c c o m p o s i t i o n , c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t r = 0 . 8 1 3 , and (b) 1978 p r e d i c t e d i o n i c c o m p o s i t i o n p l u s morphometric c h a r a c t e r s , r = 0 . 8 6 7 . (See F i g . 1 f o r l a k e names). N o t e : L e a s t d i s s i m i l a r (most s i m i l a r ) l a k e s a r e j o i n e d t o g e t h e r f i r s t , and more d i s s i m i l a r ones a r e added to t h e c l u s t e r l a t e r . 28 8 7 6 5 Lake 4 3 2 1 8 I 7 I 6 j — 5 Lake I | 4 I 3 I 2 1 — i — . — . . — i — . — . (b) 6 4 2 0 W Dissimilarity 29 Summary T h i s f i r s t c h a p t e r b r i e f l y d i s c u s s e s some hypotheses o f how e n v i r o n m e n t a l f a c t o r s can i n f l u e n c e b i o t i c c o m m u n i t i e s , and c h a r a c t e r i z e s p h y s i o c h e m i c a l p r o p e r t i e s o f t h e study l a k e s i n l i g h t o f t h e s e h y p o t h e s e s . E v i d e n c e s u g g e s t s t h a t t e m p e r a t u r e was not an i m p o r t a n t f a c t o r i n f l u e n c i n g b i o t i c communities as a l l l a k e s had s i m i l a r t e m p e r a t u r e p r o f i l e s . Of t h e t h r e e components o f e n v i r o n m e n t a l s t a b i l i t y , o n l y e n v i r o n m e n t a l s e v e r i t y was r e p r e s e n t e d by s a l i n i t y d a t a . S a l i n i t y v a r i e d markedly among l a k e s and o r d i n a t i o n r e s u l t s i n d i c a t e t h a t t h e s e v a r i a t i o n s were d e t e r m i n e d p r i m a r i l y by t h e i o n s N a , HCO3, C I , CO3 and K. M o r p h o m e t r i c a l l y , a l l l a k e s were o f s i m i l a r f o r m , v a r y i n g m a i n l y i n s i z e . F i v e c o m p o s i t e a b i o t i c parameters c h a r a c t e r i z e the l a k e s and r e l a t i o n s h i p s among parameters a r e d i s c u s s e d . These a b i o t i c v a r i a b l e s can now be used i n n u m e r i c a l c o m p a r i s o n s w i t h b i o t i c community p a r a m e t e r s . M u l t i v a r i a t e c l u s t e r diagrams p i c t o r i a l l y r e p r e s e n t a b i o t i c s i m i l a r i t i e s among l a k e s and a r e c l e a r l y r e l a t e d t o s a l i n i t y . These dendrograms a c t as t e m p l a t e s a g a i n s t w h i c h t o compare dendrograms produced from p u r e l y b i o l o g i c a l d a t a . 30 CHAPTER 2: FAUNAL COMMUNITIES Introduction T h i s c h a p t e r e x a m i n e s t h e r e l a t i o n s h i p b e t w e e n w a t e r s a l i n i t y a n d f a u n a l c o m m u n i t y s t r u c t u r e , i n t e r m s o f t h e d i v e r s i t y - s t a b i l i t y h y p o t h e s i s . A s d e f i n e d i n t h e G e n e r a l I n t r o d u c t i o n , t h i s h y p o t h e s i s s t a t e s t h a t e n v i r o n m e n t a l l y s t a b l e h a b i t a t s h a v e more d i v e r s e c o m m u n i t i e s t h a n l e s s s t a b l e o n e s , w h e r e s a l i n i t y d e f i n e s e n v i r o n m e n t a l s t a b i l i t y i n t e r m s o f s e v e r i t y ( C h a p t e r 1 ) . I t i s w e l l known t h a t many o r g a n i s m s a r e p h y s i o l o g i c a l l y a f f e c t e d by w a t e r s a l i n i t y ( B a y l y , 1 9 7 2 ) , y e t f e w s t u d i e s h a v e e x a m i n e d i t s e f f e c t s on c o m m u n i t y s t r u c t u r e . T h e m a i n d i f f e r e n c e b e t w e e n my s t u d y l a k e s i s s a l i n i t y , b u t a v a r i e t y o f a b i o t i c f a c t o r s c o u l d i n f l u e n c e t h e b i o t a . C o n s e q u e n t l y , a b i o t i c m e a s u r e s o f b a s i n m o r p h o m e t r y a r e a l s o c o m p a r e d t o t h e f a u n a l c o m m u n i t y t o t e s t f o r t h e p o s s i b l e e f f e c t s o f o t h e r p r o c e s s e s ( C h a p t e r 1 ) . A t h o r o u g h i n v e s t i g a t i o n o f l a k e c o m m u n i t i e s s h o u l d c o n s i d e r b o t h t h e e n t i r e f a u n a p l u s s u b s e t s o f t h e f a u n a , a n d c o n s i d e r c o m m u n i t i e s i n t h e d i f f e r e n t l a k e z o n e s ( l i m n o s , l i t t o r a l , b e n t h o s ) i n c o n c e r t . I n w o r k w i t h a s i n g l e t a x o n o n e m u s t a l w a y s c o n s i d e r w h e t h e r o b s e r v a t i o n s a r e an a r t e f a c t o f t h e t a x o n , o r w h e t h e r t h e e n t i r e f a u n a m i g h t p r e s e n t a d i f f e r e n t p i c t u r e ( S i m b e r l o f f , 1 9 7 4 ) . C o n v e r s e l y , g e n e r a l i z a t i o n s a b o u t t h e e n t i r e c o m m u n i t y may mask p a t t e r n s i n i t s c o m p o n e n t s u b s e t s t h a t may be i m p o r t a n t f a c t o r s c o n t r o l l i n g c o m m u n i t y s t r u c t u r e . E x p e r i m e n t a l s t u d i e s by H a l l e t a]_. ( 1 9 7 0 ) s u g g e s t t h a t c o m m u n i t i e s i n d i f f e r e n t l a k e z o n e s a r e n o t f u n c t i o n a l l y i n d e p e n d e n t b u t i n t i m a t e l y i n t e r r e l a t e d w i t h e a c h o t h e r . T h i s s t u d y e x a m i n e s t h e s t r u c t u r e o f b o t h t h e e n t i r e f a u n a l c o m m u n i t y a n d i t s s u b s e t s , i n b o t h t h e l i m n e t i c a n d l i t t o r a l z o n e s o f s e v e r a l l a k e s . 31 I t i s now g e n e r a l l y agreed t h a t s e v e r a l d i f f e r e n t measures o f community s t r u c t u r e must be used s i m u l t a n e o u s l y t o p r o v i d e t r u e r e p r e s e n t a t i o n o f a community and a v o i d the l o s s o f v a l u a b l e i n f o r m a t i o n . T h e r e f o r e , I used a v a r i e t y o f methods t o measure community s t r u c t u r e t o p r o v i d e a complete p i c t u r e o f the communities and perhaps i n s i g h t i n t o t h e v a r i o u s p o s s i b l e mechanisms c o n t r o l l i n g community s t r u c t u r e . Methods o f a n a l y z i n g community s t r u c t u r e f a l l i n t o two broad c a t e g o r i e s : s i m p l e q u a n t i t a t i v e parameters and m u l t i v a r i a t e t e c h n i q u e s . Community parameters f a l l under t h e g e n e r a l heading " d i v e r s i t y " b u t i n c l u d e s p e c i e s r i c h n e s s , d i v e r s i t y i n d i c e s , h i e r a r c h i c a l d i v e r s i t y , and a new f a m i l y o f super community i n d i c e s I have d e v e l o p e d . M u l t i v a r i a t e t e c h n i q u e s used i n community e c o l o g y i n c l u d e d i r e c t g r a d i e n t a n a l y s i s , c l a s s i f i c a t i o n , and o r d i n a t i o n ( G a u c h , 1 9 8 2 ) . T r a d i t i o n a l l y , s t u d i e s on t h e d i v e r s i t y - s t a b i l i t y phenomenon i n t e r p r e t d i v e r s i t y i n terms o f taxonomic s p e c i e s ; t h i s s t u d y a d d i t i o n a l l y c o n s i d e r s an e c o l o g i c a l c l a s s i f i c a t i o n i n which i n d i v i d u a l s a r e c a t e g o r i z e d a c c o r d i n g t o t h e i r f e e d i n g e c o l o g y and s i z e . Both Walker (1973) and P a t e r s o n & Walker (1974) s t a t e t h a t low t r o p h i c d i v e r s i t i e s a r e c h a r a c t e r i s t i c o f s a l i n e w a t e r s , y e t no one has q u a n t i t a t i v e l y examined t h e t r o p h i c s t r u c t u r e o f s a l i n e l a k e c o m m u n i t i e s . A l l measures o f community s t r u c t u r e can be a p p l i e d t o both taxonomic s p e c i e s and e c o l o g i c a l c a t e g o r i e s . QUANTITATIVE PARAMETERS To d a t e , most i n v e s t i g a t o r s o f s a l i n e l a k e communities used s p e c i e s r i c h n e s s (number o f s p e c i e s ) t o i m p l y d e c r e a s i n g d i v e r s i t y w i t h i n c r e a s i n g s a l i n i t y ( B e a d l e , 1943; Rawson & M o o r e , 1944; Moore, 1952; B a y l y & W i l l i a m s , 1966; S c u d d e r , 1969a; Hammer e t a l . , 1975; W i l l i a m s , 1978; 32 R e y n o l d s , 1979; W i e d e r h o l m , 1980; Geddes e t a l _ . , 1 9 8 1 ) , b u t r i c h n e s s may not be t h e b e s t measure of community d i v e r s i t y . F i r s t l y , s p e c i e s r i c h n e s s may be h i g h l y dependent on s a m p l i n g e f f o r t , i . e . o b s e r v e d r i c h n e s s may i n c r e a s e w i t h more o r l a r g e r s a m p l e s . T h i s i s p r o b a b l y not a s i g n i f i c a n t problem i n most s a l i n e l a k e s t u d i e s as t h e unusual n a t u r e o f t h e s e h a b i t a t s has l e d t o more e x t e n s i v e s a m p l i n g o f s a l i n e l a k e s than f r e s h w a t e r o n e s , y e t they appear t o have fewer s p e c i e s (Rawson & M o o r e , 1944; B a y l y & W i l l i a m s , 1966; S c u d d e r , 1969a; Timms, 1981; and o t h e r s ) . More i m p o r t a n t l y , s p e c i e s r i c h n e s s may be the s i m p l e s t , most fundamental measure o f a community and i t does perhaps i n d i c a t e the number o f s p e c i e s p h y s i o l o g i c a l l y c a p a b l e o f s u r v i v i n g i n an e n v i r o n m e n t , b u t a l o n e i t i s not a u s e f u l method f o r making i n f e r e n c e s about community s t r u c t u r e . Two communities can have the same number o f s p e c i e s y e t have q u i t e d i f f e r e n t r e l a t i v e p r o p o r t i o n s , n i c h e s , i n t e r s p e c i f i c r e l a t i o n s h i p s , e t c . U n l e s s one assumes t h a t t h e s e p r o p e r t i e s a r e s i m i l a r , a l t h o u g h the i d e n t i t y o f p a r t i c u l a r s p e c i e s may be d i f f e r e n t , t h e r e i s no r e a l b a s i s f o r comparing the r i c h n e s s o f two communities as a gauge o f community s t r u c t u r e ( P e e t , 1 9 7 4 ) . F o r e x a m p l e , Timms' (1981) r e s u l t s i n d i c a t e t h a t p a r t i c u l a r animal s p e c i e s occupy b r o a d e r n i c h e s i n s a l i n e l a k e s , hence t h e n a t u r e o f b i o l o g i c a l i n t e r a c t i o n s may v a r y and s p e c i e s r i c h n e s s may not be a s u i t a b l e measure o f community s t r u c t u r e . T h i s drawback o f comparing s p e c i e s r i c h n e s s was one m o t i v a t i o n f o r a t t e m p t i n g t o c r e a t e a more a p p r o p r i a t e measure o f community s t r u c t u r e , such as a d i v e r s i t y i n d e x . D i v e r s i t y i n d i c e s e l e g a n t l y combine s p e c i e s r i c h n e s s and abundance i n a s i n g l e measure o f community s t r u c t u r e . M a t h e m a t i c a l l y t h e r e are many ways t o combine r i c h n e s s and abundance i n a s i n g l e d i v e r s i t y i n d e x , and the l i t e r a t u r e c o n t a i n s many r e v i e w s o f t h i s t o p i c ( H u r l b e r t , 1970; P e e t , 1974; 33 P i e l o u , 1975; R o u t l e d g e , 1979; W a s h i n g t o n , 1 9 8 4 ) . I n d i c e s based on i n f o r m a t i o n t h e o r y a r e perhaps b e s t known among e c o l o g i s t s , p a r t i c u l a r l y the Shannon-Wiener i n d e x . Some advantages o f t h i s i n d e x a r e t h a t i t i s a p p r o p r i a t e f o r m e a s u r i n g community d i v e r s i t y from samples o f t h e t o t a l p o p u l a t i o n ( P i e l o u , 1 9 7 5 ) , i t i s independent o f sample s i z e ( M a c A r t h u r , 1 9 6 5 ) , and i t i s h i e r a r c h i c a l l y a d d i t i v e ( P i e l o u , 1974; 1 9 7 5 ) . A f o r m u l a f o r h i e r a r c h i c a l d i v e r s i t y ( P i e l o u , 1974; 1975) may e x t r a c t even more i n f o r m a t i o n about a community when i n d i v i d u a l s a r e c l a s s i f i e d i n more than one way. U n f o r t u n a t e l y , h i e r a r c h i c a l d i v e r s i t y does not o f t e n appear i n t h e l i t e r a t u r e and t h o s e who have used i t were r e s t r i c t e d t o taxonomic c l a s s i f i c a t i o n s and o f f e r e d l i m i t e d b i o l o g i c a l i n t e r p r e t a t i o n o f f i n d i n g s ( L l o y d et , 1968; K a e s l e r & H e r r i c k s , 1979; Osborne e t a l . , 1980; B e n - E l i a h u & S a f r i e l , 1 9 8 2 ) . There i s no reason t o r e s t r i c t c l a s s i f i c a t i o n s t o taxonomy, and c a t e g o r i z a t i o n a c c o r d i n g t o t r o p h i c l e v e l , s i z e , o r growth form may be much more r e v e a l i n g b i o l o g i c a l l y . For e x a m p l e , a n i m a l s can be c l a s s i f i e d i n t o both taxonomic and t r o p h i c g r o u p i n g s . T h i s method may p r o v i d e i n s i g h t i n t o what mechanisms c o n t r o l community s t r u c t u r e i n s a l i n e l a k e e c o s y s t e m s . There a r e s e v e r a l p o s s i b l e e x p l a n a t i o n s o f how p h y s i o c h e m i c a l f a c t o r s c o u l d d i r e c t l y o r i n d i r e c t l y c o n t r o l the s t r u c t u r e o f animal c o m m u n i t i e s , and some p l a u s i b l e s c e n a r i o s a r e as f o l l o w s : (1) the d i s t r i b u t i o n s o f a l l organisms a r e d i r e c t l y a t t r i b u t e d t o p h y s i o l o g i c a l l i m i t a t i o n s , (2) p r e d a t o r s and/or c o m p e t i t o r s c o n t r o l l i n g h e r b i v o r e p o p u l a t i o n s a r e p h y s i o l o g i c a l l y r e s t r i c t e d , (3) h e r b i v o r e s a r e d i s t r i b u t e d a c c o r d i n g t o t h e i r o s m o t i c t o l e r a n c e , o r (4) the d i s t r i b u t i o n and/or abundance o f f o o d f o r h e r b i v o r e s i s a f f e c t e d by s a l i n i t y . A h i e r a r c h i c a l d i v i s i o n o f d i v e r s i t y c o u l d h e l p t e a s e a p a r t t h e s e p o s s i b i l i t i e s . I f a community shows d e c r e a s i n g s p e c i e s d i v e r s i t y w i t h i n each t r o p h i c l e v e l , b u t 34 not d e c r e a s i n g t r o p h i c l e v e l d i v e r s i t y , one m i g h t s u s p e c t p h y s i o l o g i c a l c o n s t r a i n t s p l a y a more i m p o r t a n t r o l e than food r e s o u r c e s . In t h e r e v e r s e s i t u a t i o n one m i g h t s u s p e c t f o o d q u a l i t y o r q u a n t i t y t o be r e l a t e d t o s a l i n i t y and i m p o r t a n t i n s t r u c t u r i n g t h e community. O b s e r v a t i o n s o f t h i s s o r t do n o t p r o v i d e d e f i n i t i v e e x p l a n a t i o n s o f c a u s a l r e l a t i o n s h i p s , b u t do s u g g e s t a r e a s f o r f u r t h e r s t u d y . A d i v e r s i t y i n d e x i s a s i n g l e d e s c r i p t i v e s t a t i s t i c and o f f e r s a l i m i t e d amount o f i n f o r m a t i o n by i t s e l f . Communities can be compared t o each o t h e r on the b a s i s o f t h e i r d i v e r s i t y i n d i c e s , b u t one would p r e f e r c o m p a r i s o n s w i t h an independent r e f e r e n c e p o i n t . There have been s e v e r a l a t t e m p t s a t " e v e n n e s s " o r " e q u i t a b i l i t y " i n d i c e s which compare o b s e r v e d d i v e r s i t i e s t o a t h e o r e t i c a l maximum f o r t h a t p a r t i c u l a r community ( L l o y d & G h e l a r d i , 1964; P i e l o u , 1966; 1975; H u r l b e r t , 1 9 7 0 ) . The major f l a w t o a l l evenness i n d i c e s , however, i s t h a t they must presuppose a s p e c i f i c s p e c i e s - a b u n d a n c e d i s t r i b u t i o n , be i t g e o m e t r i c , l o g n o r m a l , o r M a c A r t h u r ' s broken s t i c k d i s t r i b u t i o n (May, 1975; Southwood, 1 9 7 8 ) . Evenness i n d i c e s have not been very p o p u l a r i n e c o l o g i c a l s t u d i e s because t h e r e i s no agreement on which s p e c i e s - a b u n d a n c e d i s t r i b u t i o n i s a p p r o p r i a t e . I propose a new approach t o t h i s problem by c r e a t i n g a t h e o r e t i c a l maximum " s u p e r community" d e t e r m i n e d by sample communities t h e m s e l v e s , not a presupposed s p e c i e s - a b u n d a n c e d i s t r i b u t i o n . The s u p e r community i n d i c e s I have d e v e l o p e d a r e c o n c e p t u a l l y v e r y s i m p l e : g i v e n any s e r i e s o f d i s c r e t e c o m m u n i t i e s , each one i s i n d e p e n d e n t l y compared, by means o f s i m i l a r i t y i n d i c e s , t o a t h e o r e t i c a l super community. The super community c o n t a i n s a l l s p e c i e s from a l l communities i n the s e r i e s , a t t h e maximum d e n s i t y known f o r each s p e c i e s . The super community i t s e l f , l i k e a l l t h e o r e t i c a l maxima, i s p r o b a b l y not b i o l o g i c a l l y f e a s i b l e , 35 b u t i t does employ an i n t u i t i v e l y more r e a l i s t i c s p e c i e s - a b u n d a n c e d i s t r i b u t i o n than o t h e r t h e o r e t i c a l m o d e l s . T h i s t y p e o f a n a l y s i s i s f e a s i b l e f o r o n l y a s p e c i f i c v a r i e t y o f community s t u d i e s , such as s p a t i a l l y d i s t i n c t communities where a l l s p e c i e s a r e c a p a b l e o f o c c u r r i n g a t a l l s i t e s , o r communities t h a t are s e p a r a t e d i n t i m e b u t not s p a c e . T h i s p a r t i c u l a r study f a l l s i n t o t h e f i r s t c a t e g o r y : t h e l a k e s on B e c h e r ' s P r a i r i e a r e i s l a n d s s i t u a t e d c l o s e enough t o g e t h e r t h a t a l l s p e c i e s have equal p o t e n t i a l f o r d i s p e r s a l t o a l l l a k e s . B i o l o g i c a l l y , t h e s e i n d i c e s measure t h e number o f s p e c i e s p r e s e n t i n a l a k e r e l a t i v e t o t h e t o t a l number a v a i l a b l e f o r c o l o n i z a t i o n , o r they measure t h e c o m p l e x i t y o f a sample community r e l a t i v e t o the most complex community p o s s i b l e . The main advantages o f super community i n d i c e s a r e t h a t (1) they compare sample communities t o a r e f e r e n c e p o i n t d e t e r m i n e d by the samples t h e m s e l v e s and not some presupposed s p e c i e s - a b u n d a n c e d i s t r i b u t i o n , (2) a v a r i e t y o f s i m i l a r i t y i n d i c e s can be used t o compare samples t o super communities depending on the n a t u r e o f t h e d a t a and p e r s o n a l p h i l o s o p h y o f the r e s e a r c h e r , (3) i n d i c e s a r e comparable t o o t h e r community parameters and a r e a p p r o p r i a t e f o r use i n s i m p l e d e s c r i p t i v e s t a t i s t i c s , i . e . c o r r e l a t i o n s w i t h e n v i r o n m e n t a l p a r a m e t e r s , and (4) i n d i c e s a r e e a s i l y i n t e r p r e t t e d b i o l o g i c a l l y . MULTIVARIATE TECHNIQUES M u l t i v a r i a t e t e c h n i q u e s o f a n a l y s i s have l o n g been p o p u l a r among p h y t o s o c i o l o g i s t s and more r e c e n t l y have r e c e i v e d much a t t e n t i o n from animal e c o l o g i s t s ( S p r u l e s , 1975; S p r u l e s & H o l t b y , 1979; Gates e t a l . , 1983; Townsend e t _al_. , 1 9 8 3 ) . There a r e t h r e e complementary methods of m u l t i v a r i a t e a n a l y s i s : d i r e c t g r a d i e n t a n a l y s i s , o r d i n a t i o n , and 36 c l a s s i f i c a t i o n . D i r e c t g r a d i e n t a n a l y s i s examines t h e d i s t r i b u t i o n o f i n d i v i d u a l s p e c i e s p o p u l a t i o n s a l o n g r e c o g n i z e d e n v i r o n m e n t a l g r a d i e n t s . O r d i n a t i o n i s t h e o b j e c t i v e n u m e r i c a l arrangement o f samples o r v a r i a b l e s a l o n g axes t h a t may c o r r e s p o n d t o e n v i r o n m e n t a l g r a d i e n t s . C l a s s i f i c a t i o n methods group v a r i a b l e s i n t o c l u s t e r s depending on t h e i r r e l a t i v e s i m i l a r i t i e s . Two examples o f c l a s s i f i c a t i o n used i n t h i s study a r e c l u s t e r i n g s i m i l a r sample s i t e s on the b a s i s o f t h e i r s p e c i e s c o m p o s i t i o n , and c l u s t e r i n g s p e c i e s on t h e b a s i s o f t h e sample s i t e s t h a t they o c c u r r e d i n . The c h o i c e o f method depends on study o b j e c t i v e s and d a t a s e t s t r u c t u r e . Materials and Methods INVERTEBRATE SAMPLING AND ENUMERATION A l l samples were c o l l e c t e d between May and O c t o b e r 1978, by R . A . , R . J . & S . G . C a n n i n g s . L i m n e t i c z o o p l a n k t o n were sampled i n t r i p l i c a t e every t e n days w i t h a 2 l i t r e Van Dorn b o t t l e a t 1-2 m d e p t h , m i d - l a k e . Submerged l i g h t t r a p s were s e t between dusk and dawn one n i g h t a month i n each l a k e , a t 1 m depth j u s t above bottom mud. These s i m p l e f u n n e l t r a p s c o n s i s t e d o f a 1 . 4 l i t r e (48 o z . ) c a n , a f f i x e d t o an u p r i g h t p o s t , w i t h a f u n n e l o p e n i n g and a Cyalume l i g h t s t i c k i n s i d e t o a t t r a c t a n i m a l s . L i t t o r a l zone fauna were sampled w i t h sweep n e t s e v e r y t e n d a y s . To ensure t h a t sweep samples were q u a n t i t a t i v e and c o m p a r a b l e , samples were always taken a t t h e same p o i n t a l o n g the l a k e shore and each sample c o n s i s t e d o f 5 o r 10 s t a n d a r d i z e d sweeps, depending on f a u n a l d e n s i t y . A l l specimens were s t o r e d i n 70% e t h a n o l . One d i f f i c u l t y i n h e r e n t t o a l l community s t u d i e s i s how t o d e l i m i t a 37 community: t a x o n o m i c a l l y , t e m p o r a l l y , s p a t i a l l y o r by s a m p l i n g t e c h n i q u e . In t h i s s t u d y , communities were d e f i n e d s i m u l t a n e o u s l y by s a m p l i n g t e c h n i q u e and l a k e z o n e , as each method was a p p l i e d t o a d i f f e r e n t l a k e z o n e , and d e f i n e d by taxonomic s u b s e t s o f t o t a l sample s e t s . A l t h o u g h samples were t a k e n o v e r a p e r i o d o f f i v e months, the t i m e element was l a r g e l y i g n o r e d owing t o t h e h i g h l y v a r i a b l e n a t u r e o f a q u a t i c communities and i n a d e q u a t e number o f r e p l i c a t e samples n e c e s s a r y t o a c c u r a t e l y q u a n t i f y temporal c h a n g e s . I n s t e a d , community s t r u c t u r e was measured i n each l a k e o v e r t h e e n t i r e s e a s o n . In t o t a l , t h e f o l l o w i n g communities i n each l a k e were examined and a n a l y z e d i n d e p e n d e n t l y : w a t e r b o t t l e s a m p l e s : l i m n e t i c z o o p l a n k t o n ; l i g h t t r a p s a m p l e s : a l l s p e c i e s ; E n t o m o s t r a c a ; C o l e o p t e r a ; H e m i p t e r a ; sweep s a m p l e s : C o l e o p t e r a ; H e m i p t e r a . L i g h t t r a p s c o l l e c t an enormous number and v a r i e t y o f t a x a t h a t may not j u s t l y be lumped t o g e t h e r i n n u m e r i c a l a n a l y s i s o f community s t r u c t u r e . T h e r e f o r e , s u b s e t s o f the t o t a l c o l l e c t i o n were a l s o e x a m i n e d . L i t t o r a l sweep samples c o n t a i n e d a phenomenal volume o f m a t e r i a l , b u t o n l y a d u l t C o l e o p t e r a and Hemiptera were enumerated as t h e s e i n d i v i d u a l s were r e a d i l y removed from s a m p l e s , p o s s i b l e t o i d e n t i f y t o s p e c i e s , and complementary t o s u b s e t s o f l i g h t t r a p m a t e r i a l . A l l i n d i v i d u a l s were examined and i d e n t i f i e d t o s p e c i e s where p o s s i b l e . Taxonomic i d e n t i f i c a t i o n s employed p r i m a r i l y t h e f o l l o w i n g w o r k s : (1) C r u s t a c e a - : Brooks (1957; 1 9 5 9 ) , D e x t e r ( 1 9 5 9 ) , W i l s o n ( 1 9 5 9 ) , Yeatman (1959) and Pennak ( 1 9 7 8 ) ; (2) Odonata: Cannings & S t u a r t (1977) ; (3) H e m i p t e r a : H u n g e r f o r d ( 1 9 4 8 ) , Scudder (1976) and T r u x a l ( 1 9 7 9 ) ; (4) C o l e o p t e r a : Wall i s ( 1 9 3 3 ) , Hatch ( 1 9 5 3 ; 1965; 1971) , Anderson (1971; 1976; 1 9 8 3 ) , L a r s o n ( 1 9 7 5 ) , Gunderson (1977) and C o l o n n e l l i ( 1 9 8 0 ) ; (5) 38 T r i c h o p t e r a : W i g g i n s ( 1 9 7 7 ) , (6) D i p t e r a : Cook ( 1 9 5 6 ) , Coffman (1978) and Bel ton ( 1 9 8 3 ) . F u r t h e r d e t e r m i n a t i o n s o f C o l e o p t e r a were performed by D . J . L a r s o n a t the Memorial U n i v e r s i t y o f Newfoundland and R . E . Roughley a t t h e U n i v e r s i t y o f M a n i t o b a . Voucher specimens and r e f e r e n c e m a t e r i a l a r e i n the Spencer E n t o m o l o g i c a l Museum a t the U n i v e r s i t y o f B r i t i s h C o l u m b i a . F o u n d a t i o n s f o r a t r o p h i c c l a s s i f i c a t i o n scheme a r e p r o v i d e d by Cummins (1973; M e r r i t t & Cummins, 1 9 7 8 ) , and enough i n f o r m a t i o n i s a v a i l a b l e i n the l i t e r a t u r e t o a s s i g n i n d i v i d u a l s p e c i e s t o each f e e d i n g e c o l o g y g r o u p . [ H e r e i n a f t e r , f e e d i n g e c o l o g y groups w i l l be r e f e r r e d t o as t r o p h i c l e v e l s . ] The f i v e t r o p h i c l e v e l s used a r e as f o l l o w s : (a) s h r e d d e r ; h e r b i v o r e : A n i m a l s t h a t s h r e d l i v e o r decomposing v a s c u l a r p l a n t m a t e r i a l , e g . H a l i p l u s s p p . (b) c o l l e c t o r ; f i l t e r f e e d e r : A n i m a l s t h a t f i l t e r suspended f i n e p a r t i c u l a t e o r g a n i c m a t t e r from t h e w a t e r c o l u m n , e g . Daphnia s p p . ( c ) c o l l e c t o r ; sediment f e e d e r : A n i m a l s t h a t g a t h e r f i n e p a r t i c u l a t e o r g a n i c m a t t e r from s e d i m e n t s and d e p o s i t s , e g . H y a l l e a a z t e c a , C h i r o n o m i n i . (e) p r e d a t o r ; e n g u l f e r : A n i m a l s t h a t f e e d on whole l i v e a n i m a l s ( o r p a r t s ) and have r a p t o r i a l m o u t h p a r t s , e g . D y t i s c i d a e , C h a o b o r u s . ( f ) p r e d a t o r ; p i e r c e r : A n i m a l s t h a t f e e d on l i v e animal c e l l and t i s s u e f l u i d s and have p i e r c i n g mouth p a r t s , e g . C o r i x i d a e . Data a c q u i r e d from the l i t e r a t u r e were used t o a s s i g n s p e c i e s t o l e v e l s . Measures o f a d u l t t o t a l body l e n g t h , e x c e p t i n i n s e c t o r d e r s o t h e r than Hemiptera and C o l e o p t e r a which employed l e n g t h s o f l a s t l a r v a l i n s t a r s , were used t o d e s i g n a t e s i z e g r o u p s . These s i z e groups were c o l l a t e d as o c t a v e s ( l o g a r i t h m i c l i k e i n t e r v a l s ) t o emphasize s u b t l e s i z e d i f f e r e n c e s 39 among s m a l l s p e c i e s . A p p r o x i m a t e l y t e n s i z e groups were d e t e r m i n e d f o r each sample s e t i n o r d e r t o p r o v i d e a wide enough range o f groups f o r n u m e r i c a l a n a l y s i s . T r o p h i c l e v e l - s i z e groups a r e r e f e r r e d t o as e c o l o g i c a l c a t e g o r i e s . MEASURES OF COMMUNITY STRUCTURE To i n v e s t i g a t e the r e l a t i o n s h i p between s a l i n i t y and f a u n a l c o m m u n i t i e s , t h e s e r i e s o f e i g h t l a k e s was c h a r a c t e r i z e d a b i o t i c a l l y a c c o r d i n g t o w a t e r c h e m i s t r y and morphometry ( C h a p t e r 1 ) , and b i o t i c a l l y a c c o r d i n g t o s p e c i e s d i s t r i b u t i o n , r i c h n e s s , abundance, d i v e r s i t y , h i e r a r c h i c a l d i v e r s i t y , and super community i n d i c e s . In a d d i t i o n , l a k e s were c l a s s i f i e d i n t o h i e r a r c h i c a l c l u s t e r diagrams on the b a s i s o f t h e i r s p e c i e s c o m p o s i t i o n and abundance. The d i v e r s i t y i n d e x I chose i s the Shannon-Wiener i n d e x ( e n t r o p y f o r m u l a ) based on i n f o r m a t i o n t h e o r y ( K h i n c h i n , 1957; M a r g a l e f , 1 9 6 8 ) : H' = - I P i l n P i where p-j = t h e p r o p o r t i o n o f i n d i v i d u a l s i n s p e c i e s i T h i s f o r m u l a r e a d i l y d i v i d e s t o t a l community d i v e r s i t y i n t o t h e h i e r a r c h i c a l components, t r o p h i c l e v e l d i v e r s i t y and the mean w i t h i n - t r o p h i c l e v e l s p e c i e s d i v e r s i t y averaged o v e r a l l t r o p h i c l e v e l s , such t h a t : H ' ( s ) = H ' ( t ) + H ' t ( s ) where H ' ( s ) = t o t a l s p e c i e s d i v e r s i t y H ' ( t ) = t r o p h i c l e v e l d i v e r s i t y H ' t ( s ) = mean w i t h i n - t r o p h i c l e v e l s p e c i e s d i v e r s i t y The m a t h e m a t i c a l f o r m u l a i s as f o l l o w s : 40 H ' ( s ) = -Xpjln pj + ip j ( - I p i l n pi) where p-j = p r o p o r t i o n o f i n d i v i d u a l s i n s p e c i e s i P j = p r o p o r t i o n o f i n d i v i d u a l s i n t r o p h i c l e v e l j There a r e many s i m i l a r i t y , o r d i s s i m i l a r i t y , measures w h i c h c o u l d be used i n a s u p e r community i n d e x . In t h i s study I c o n s i d e r e d two c o n t r a s t i n g m e a s u r e s : (1) J a c c a r d ' s c o e f f i c i e n t c a l c u l a t e d from b i n o m i a l s p e c i e s p r e s e n c e / a b s e n c e d a t a where common and r a r e s p e c i e s have equal w e i g h t s , and (2) E u c l i d e a n d i s t a n c e s c a l c u l a t e d from q u a n t i t a t i v e s p e c i e s abundance d a t a and i n f l u e n c e d m a i n l y by n u m e r i c a l l y dominant s p e c i e s . Super community i n d i c e s u s i n g J a c c a r d ' s c o e f f i c i e n t a r e s i m i l a r t o s p e c i e s r i c h n e s s i n d i c e s ; t h o s e e m p l o y i n g E u c l i d e a n d i s t a n c e s a r e more c l o s e l y r e l a t e d t o t r a d i t i o n a l d i v e r s i t y i n d i c e s . T a b l e 6 l i s t s a l l community parameters and t h e i r s y m b o l s . P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t was used t o s t a t i s t i c a l l y compare each parameter w i t h p h y s i o c h e m i c a l v a r i a b l e s d i s c u s s e d i n C h a p t e r 1 . G i v e n samples c o l l e c t e d o v e r a p e r i o d o f t i m e , t h e r e a r e s e v e r a l ways t o d e t e r m i n e a s i n g l e i n d e x o f community s t r u c t u r e : maximum d i v e r s i t y , d i v e r s i t y o f p o o l e d s a m p l e s , d i v e r s i t y measures averaged o v e r t i m e , and s t a t i s t i c a l l y e s t i m a t e d d i v e r s i t y . [ T h i s problem i s d i s c u s s e d i n terms o f d i v e r s i t y i n d i c e s , b u t i t a p p l i e s t o most community p a r a m e t e r s . ] U n f o r t u n a t e l y , t h i s study does n o t p r o v i d e the l a r g e number o f samples r e q u i r e d t o e s t i m a t e d i v e r s i t y , by e i t h e r s e q u e n t i a l l y p o o l e d q u a d r a t s ( P i e l o u , 1975) o r a j a c k k n i f e e s t i m a t e ( Z a h l , 1 9 7 7 ) , and t o c a l c u l a t e a measure o f v a r i a n c e . The maximum d i v e r s i t y found a t any p o i n t d u r i n g t h e season measures a s y s t e m ' s p o t e n t i a l f o r s u p p o r t i n g s p e c i e s a t any one time ( R o o t , 1 9 7 3 ) , b u t t h i s measure may be confounded by v a g r a n t s p e c i e s and c o n s e q u e n t l y not i n d i c a t e t h e t r u e maximum. The d i v e r s i t y o f a l l samples 41 T a b l e 6 . L i s t o f community parameters used t o c h a r a c t e r i z e f a u n a l c o m m u n i t i e s . Symbol d e s c r i p t i o n D d e n s i t y (number o f i n d i v i d u a l s per u n i t volume) s s p e c i e s r i c h n e s s (number o f s p e c i e s ) t i e c o l o g i c a l c a t e g o r y r i c h n e s s (number o f e c o l o g i c a l c a t e g o r i e s ) DIVERSITY INDICES H ' ( s ) t o t a l s p e c i e s d i v e r s i t y H ' ( t ) t r o p h i c l e v e l d i v e r s i t y H ' ( t i ) e c o l o g i c a l c a t e g o r i e s d i v e r s i t y H ' x ( s ) mean w i t h i n - t r o p h i c l e v e l , s p e c i e s d i v e r s i t y H'tH) mean w i t h i n - t r o p h i c l e v e l , s i z e group d i v e r s i t y H ' t j ( s ) mean w i t h i n - e c o l o g i c a l c a t e g o r y , s p e c i e s d i v e r s i t y SUPER COMMUNITY INDICES Q j ( s ) J a c c a r d ' s c o e f f i c i e n t , based on p r e s e n c e / a b s e n c e o f s p e c i e s Q j ( t i ) J a c c a r d ' s c o e f f i c i e n t , based on p r e s e n c e / a b s e n c e o f e c o l o g i c a l c a t e g o r i e s Qd(s) E u c l i d e a n d i s t a n c e , based on r e l a t i v e abundance o f s p e c i e s Q d ( t i ) E u c l i d e a n d i s t a n c e , based on r e l a t i v e abundance o f e c o l o g i c a l c a t e g o r i e s 42 p o o l e d t h r o u g h o u t the season a c c o u n t s f o r s e a s o n a l r e p l a c e m e n t o f s p e c i e s ( R o o t , 1 9 7 3 ) , and i t i s n o t g r e a t l y a f f e c t e d by v a g r a n t s . Independent d i v e r s i t y measures averaged o v e r t i m e w i l l n o r m a l l y be s i m i l a r t o but l o w e r than p o o l e d m e a s u r e s , and even l o w e r than s t a t i s t i c a l l y e s t i m a t e d v a l u e s ( H e n d r i c k s o n , 1 9 7 9 ) . P r e l i m i n a r y c a l c u l a t i o n s i n d i c a t e d a s t r o n g c o r r e l a t i o n between p o o l e d and averaged d i v e r s i t i e s so o n l y one ( p o o l e d ) was used i n t h i s study t o c a l c u l a t e a s i n g l e measure o f d i v e r s i t y , o v e r the e n t i r e s e a s o n . In t h i s s t u d y , h i e r a r c h i c a l c l a s s i f i c a t i o n was t h e o n l y m u l t i v a r i a t e t e c h n i q u e employed w i t h any s u c c e s s . D i r e c t g r a d i e n t a n a l y s i s was r e j e c t e d as f a r t o o u n w i e l d y ; o r d i n a t i o n was e x p l o r e d i n depth b u t abandoned as data s e t s were t o o d i s c o n t i n u o u s t o a n a l y z e w i t h o u t a h i g h degree o f d i s t o r t i o n , u s i n g the a v a i l a b l e p r o g r a m s . The program used t o c l u s t e r d a t a on t h e e i g h t study l a k e s was UPGMA, as d e s c r i b e d i n C h a p t e r 1 . Both taxonomic s p e c i e s and e c o l o g i c a l c a t e g o r i e s were used t o produce c l u s t e r d i a g r a m s . E u c l i d e a n d i s t a n c e s c l u s t e r e d l a k e s on the b a s i s o f s p e c i e s / c a t e g o r i e s abundances. J a c c a r d ' s c o e f f i c i e n t o f s i m i l a r i t y , c a l c u l a t e d from b i n o m i a l p r e s e n c e / a b s e n c e d a t a , was used t o c l u s t e r l a k e s on t h e b a s i s o f t h e i r s p e c i e s o r c a t e g o r i e s c o m p o s i t i o n , and t o c l u s t e r s p e c i e s on the b a s i s o f l a k e s t h a t they o c c u p i e d . T h i s l a t t e r t e c h n i q u e i s an o b j e c t i v e way o f d e s i g n a t i n g s p e c i e s as t y p i c a l f r e s h w a t e r , e u r y h a l i n e , or h i g h s a l i n i t y s p e c i e s . The c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t ( S o k a l & R o h l f , 1962; R o h l f , 1974; Romesburg, 1984) was used t o e v a l u a t e the amount o f d i s t o r t i o n a s s o c i a t e d w i t h each c l u s t e r and t o q u a n t i t a t i v e l y compare dendrograms based on b i o t i c and a b i o t i c v a r i a b l e s . 43 Results DISTRIBUTION Three p r i n c i p a l groups o f s p e c i e s , t h o s e r e s t r i c t e d t o s a l i n e l a k e s , t o f r e s h w a t e r l a k e s , and t h o s e o c c u r r i n g a t moderate s a l i n i t i e s o r t o l e r a n t o f a wide range o f s a l i n i t y , were r e v e a l e d when m u l t i v a r i a t e c l a s s i f i c a t i o n c l u s t e r e d s p e c i e s a c c o r d i n g t o l a k e s t h a t they o c c u r r e d i n ( F i g . 5 ) . A l i s t o f the s p e c i e s p r e s e n t i n the s a m p l e s , t h e i r s i z e , t r o p h i c l e v e l , and d i s t r i b u t i o n i s p r o v i d e d i n T a b l e 7 . Group A a t t h e top o f F i g . 5 c o n t a i n s s p e c i e s t h a t a r e p r i m a r i l y i n h a b i t a n t s o f f r e s h w a t e r l a k e s , and most n o t i c e a b l e i s t h e t i g h t c l u s t e r o f s p e c i e s t h a t were found o n l y i n Lake 1 , i n c l u d i n g Daphnia r o s e a , D. c a t a w b a , A l o n a q u a d r a n g u l a r i s , H a l i p i us l e e c h i and Hydroporus g r i s e o s t r i a t u s . The c e n t r e c l u s t e r (Group B) c o n t a i n s s p e c i e s t o l e r a n t o f a l l s a l i n i t i e s such as C e r i o d a p h n i a q u a d r a n g u l a , C a l l i b a e t i s s p p , Enallagma s p p , N o t o n e c t a k i r b y i , C e n o c o r i x a b i f i d a , C h i r o n o m i n i and H a l i p l u s i m m a c u l i c o l 1 i s , p l u s many o t h e r s u b - g r o u p s such as t h o s e s p e c i e s t h a t were found i n a l l l a k e s l e s s than 5500 j ; S : Chydorus  s p h a e r i c u s , Cymatia a m e r i c a n a , C a l l i c o r i x a a u d e n i , Hygrotus l u t e s c e n s and Chaoborus a m e r i c a n u s . Group C , a t t h e bottom o f the dendrogram, c o n t a i n s s p e c i e s i n c l u d i n g B r a n c h i n e c t a m a c k i n i , Daphnia s i m i l i s , Moina h u t c h i n s o n i , Diaptomus n e v a d e n s i s , Diaptomus s i c i l i s , D a s y c o r i x a r a w s o n i , C e n o c o r i x a  e x p l e t a , Hygrotus m a s c u l i n u s and Hydroporus s p e n c e r i , t h a t were found o n l y i n s a l i n e l a k e s . COMMUNITY COMPOSITION CRUSTACEAN ZOOPLANKTON. Z o o p l a n k t o n s p e c i e s c o m p o s i t i o n and r e l a t i v e abundance d i f f e r e d markedly among l a k e s ( F i g . 6 a ; 7 a ) , w i t h C l a d o c e r a dominant i n f r e s h t o m o d e r a t e l y s a l i n e l a k e s ; c a l a n o i d copepods 44 T a b l e 7 . L i s t o f s p e c i e s p r e s e n t i n s a m p l e s , t h e i r s i z e , t r o p h i c c l a s s , a n d d i s t r i b u t i o n . ( S e e F i g . 1 f o r l a k e n a m e s ) . # s p e c i e s mean l e n g t h (mm) t r o p h i c l e v e l 1 2 3 l a k e 4 5 6 7 C l a s s B r a n c h i o p o d a O r d e r A n o s t r a c a 1 B r a n c h i n e c t a m a c k i n i D e x t e r 2 2 . 5 c o l l e c t o r ; f i l t e r f e e d e r 0 O r d e r D i p l o s t r a c a , S u b o r d e r C l a d o c e r a 2 D a p h n i a magna S t r a u s 5 . 0 c o l l e c t o r f i l t e r f e e d e r 0 0 3 D. s i m i l i s C l a u s 2 . 8 c o l l e c t o r f i l t e r f e e d e r 0 0 4 D. r o s e a S a r s 1 . 3 3 c o l l e c t o r f i l t e r f e e d e r 0 5 D . p u l e x / s c h j S d l e r i 1 . 7 5 c o l l e c t o r f i l t e r f e e d e r 0 0 0 0 6 D. c a t a w b a C o k e r 1 . 3 3 c o l l e c t o r f i l t e r f e e d e r 0 7 S i m o c e p h a l u s v e t u l u s S c h j S d l e r 3 . 0 c o l l e c t o r f i l t e r f e e d e r 0 0 0 0 0 0 8 S c a p h o l e r b e r i s k i n g i S a r s 0 . 9 c o l l e c t o r f i l t e r f e e d e r 0 0 0 0 9 C e r i o d a p h n i a q u a d r a n g u l a ( O . F . M u l l e r ) 1 . 0 c o l l e c t o r f i l t e r f e e d e r 0 0 0 0 0 0 0 10 M o i n a h u t c h i n s o n i Brehm 1 . 6 . c o l l e c t o r f i l t e r f e e d e r 11 L e y d i g i a q u a d r a n g u l a r i s ( O . F . M u l l e r ) 0 . 9 c o l l e c t o r f i l t e r f e e d e r 0 0 12 A l o n a q u a d r a n g u l a r i s ( O . F . M u l l e r ) 0 . 9 c o l l e c t o r f i l t e r f e e d e r 0 13 A . r e c t a n g u l a S a r s 0 . 3 8 c o l l e c t o r f i l t e r f e e d e r 0 0 0 0 14 C h y d o r u s s p h a e r i c u s ( O . F . M u l l e r ) 0 . 4 c o l l e c t o r f i l t e r f e e d e r 0 0 0 0 0 C l a s s O s t r a c o d a 15 S p e c i e s 1 1 . 0 c o l l e c t o r s e d i m e n t f e e d e r 0 0 16 S p e c i e s 2 1 . 0 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 0 C l a s s C o p e p o d a 17 D i a p t o m u s l e p t o p u s F o r b e s 1 . 9 1 c o l l e c t o r ; f i l t e r f e e d e r 0 0 0 18 D. n e v a d e n s i s L i g h t 3 . 7 3 p r e d a t o r ; e n g u l f e r 0 0 19 D. s i c i l i s F o r b e s 1 . 3 c o l l e c t o r f i l t e r f e e d e r 0 0 0 20 E u c y c l o p s a g i l i s ( K o c h ) 0 . 9 5 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 21 C y c l o p s v e r n a l i s F i s c h e r 1 . 1 1 p r e d a t o r ; e n g u l f e r 0 0 0 22 C . n a v u s K e r r i c k 1 . 1 1 p r e d a t o r ; e n g u l f e r 0 0 23 M a c r o c y c l o p s a l b i d u s ( J u r i n e ) 1 . 4 8 p r e d a t o r ; e n g u l f e r 0 0 0 0 C l a s s M a l a c o s t r a c a r O r d e r A m p h i p o d a 24 H y a l e l l a a z t e c a ( S a u s s u r e ) 6 . 0 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 0 0 25 Gammarus l a c u s t r i s S a r s 2 0 . 0 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 0 C l a s s I n s e c t a O r d e r C o l l e m b o l a 26 S m i n t h u r i d e s s p . 0 . 7 5 c o l l e c t o r ; s e d i m e n t f e e d e r 0 O r d e r E p h e m e r o p t e r a , 27 C a e n i s s p p . 4 . 5 c o l l e c t o r ; s e d i m e n t f e e d e r 0 28 S i p h l o n u r u s s p p . 1 4 . 5 c o l l e c t o r s e d i m e n t f e e d e r 0 29 C a l l i b a e t l s s p p . 8 . 0 c o l l e c t o r s e d i m e n t f e e d e r 0 0 0 0 0 0 0 O r d e r O d o n a t a 30 L e s t e s c o n g e n e r Hagen 2 4 . 0 p r e d a t o r ; e n g u l f e r 0 0 0 0 31 L . d i s j u n c t u s S e l y s 2 6 . 0 p r e d a t o r ; e n g u l f e r 0 0 32 E n a l l a g m a s p p . 2 5 . 5 p r e d a t o r ; e n g u l f e r 0 0 0 0 0 0 0 8 T a b l e 7 . CONT. 45 # s p e c i e s mean l e n g t h (mm) t r o p h i c l e v e l l a k e 1 2 3 4 5 6 7 8 33 A e s h n a i n t e r r u p t a W a l k e r 4 0 . 5 p r e d a t o r ; e n g u l f e r 0 34 Sympetrum s p p . 1 5 . 0 p r e d a t o r , e n g u l f e r 0 35 O r d e r P l e c o p t e r a 1 2 . 0 s h r e d d e r ; h e r b i v o r e 0 O r d e r H e m i p t e r a F a m i l y N o t o n e c t i d a e 36 N o t o n e c t a k i r b y i H u n g e r f o r d 1 4 . 5 p r e d a t o r , p i e r c e r 0 0 0 0 0 0 0 37 N . u n d u l a t a Say F a m i l y C o r i x i d a e 1 4 . 5 p r e d a t o r , p i e r c e r 0 0 38 C y m a t i a a m e r i c a n a H u s s e y 7 . 0 p r e d a t o r , p i e r c e r 0 0 0 0 0 39 D a s y c o r i x a r a w s o n i H u n g e r f o r d 8 . 1 9 p r e d a t o r , p i e r c e r 0 0 0 40 C a l l i c o r i x a a u d e n i H u n g e r f o r d 7 . 6 p r e d a t o r p i e r c e r 0 0 0 0 0 41 H e s p e r o c o r i x a l a e v i g a t a ( U h l e r ) 1 0 . 4 5 p r e d a t o r , p i e r c e r 0 0 0 0 0 0 42 C e n o c o r i x a b i f i d a ( H u n g e r f o r d ) 7 . 3 5 p r e d a t o r p i e r c e r 0 0 0 0 0 0 0 0 43 C . e x p l e t a ( U h l e r ) O r d e r C o l e o p t e r a F a m i l y H a l i p l i d a e 6 . 8 p r e d a t o r p i e r c e r 0 0 0 44 H a l i p i u s immacul i c o l 1 i s H a r r i s 2 . 7 5 s h r e d d e r h e r b i v o r e 0 0 0 0 0 0 0 0 45 H . s t r i g a t u s R o b e r t s 3 . 0 s h r e d d e r h e r b i v o r e 0 0 0 0 0 0 0 46 H . s t a g n i n u s L e e c h 3 . 4 s h r e d d e r h e r b i v o r e 0 0 0 0 0 0 47 H . l e e c h i W a l l i s F a m i l y D y t i s c i d a e 4 . 2 5 s h r e d d e r h e r b i v o r e 0 48 L a c c o p h i l u s b i g u t t a t u s K i r b y 4 . 3 5 p r e d a t o r e n g u l f e r 0 0 49 H y g r o t u s s a y i B a l f o u r - B r o w n e 3 . 0 5 p r e d a t o r e n g u l f e r 0 0 0 50 H . u n g u i c u l a r i s ( C r o t c h ) 5 . 2 9 p r e d a t o r e n g u l f e r 0 0 0 0 0 0 51 H. l u t e s c e n s ( L e C o n t e ) 3 . 3 5 p r e d a t o r e n g u l f e r 0 0 0 0 0 52 H . m a s c u l i n u s ( C r o t c h ) 4 . 3 p r e d a t o r e n g u l f e r 0 0 0 53 H. i m p r e s s o p u n c t a t u s ( S c h a l l e r ) 4 . 7 7 p r e d a t o r e n g u l f e r 0 54 H y d r o p o r u s s t r i a t e l l u s L e C o n t e 4 . 0 6 p r e d a t o r e n g u l f e r 0 55 H. g r i s e o s t r i a t u s ( D e G e e r ) 4 . 8 6 p r e d a t o r e n g u l f e r 0 56 H . s p e n c e r i ( L e e c h ) 5 . 6 9 p r e d a t o r e n g u l f e r 0 0 0 57 A g a b u s a j a x F a l l 6 . 9 2 p r e d a t o r e n g u l f e r 0 0 0 58 A . g r i s e i p e n n i s L e C o n t e 6 . 9 3 p r e d a t o r e n g u l f e r 0 0 59 A . a n t e n n a t u s L e e c h 7 . 6 8 p r e d a t o r e n g u l f e r 0 0 0 60 I . f r a t e r c u l u s L e C o n t e 1 0 . 2 2 p r e d a t o r e n g u l f e r 0 0 61 I . s u b a e n u s E r i c h s o n 1 0 . 4 6 p r e d a t o r e n g u l f e r 0 0 0 62 R h a n t u s f r o n t a l i s (Marsham) 9 . 5 7 p r e d a t o r e n g u l f e r 0 0 0 0 0 0 0 63 D y t i s c u s c o r d i e r i Aube 2 9 . 0 p r e d a t o r e n g u l f e r 0 64 D. a l a s k a n u s B a l f o u r - B r o w n e 2 7 . 4 p r e d a t o r e n g u l f e r 0 0 65 G r a p h o d e r u s l i b e r u s ( S a y ) 1 1 . 5 4 p r e d a t o r e n g u l f e r 0 66 G . p e r p l e x u s S h a r p 1 4 . 6 5 p r e d a t o r e n g u l f e r 0 67 G . o c c i d e n t a l i s H o r n F a m i l y H y d r o p h i l i d a e 1 2 . 6 5 p r e d a t o r e n g u l f e r 0 68 L a c c o b i u s s p . 2 . 7 5 s h r e d d e r h e r b i v o r e 0 0 69 E n o c h r u s d i f f u s u s L e C o n t e 6 . 0 s h r e d d e r h e r b i v o r e 0 0 46 T a b l e 7 . CONT. # s p e c i e s mean l e n g t h (mm) t r o p h i c l e v e l 1 2 l a k e 3 4 5 6 7 8 F a m i l y C u r c u l i o n i d a e 70 L i x e l l u s f i l i f o r m i s L e C o n t e 4 . 4 s h r e d d e r ; h e r b i v o r e 0 0 71 L i t o d a c t y l u s g r i s e o m i c a n s R e d t e n b a c h e r 2 . 8 s h r e d d e r ; h e r b i v o r e 0 0 O r d e r T r i c h o p t e r a 72 L e p i d o s t o m a s p p . 1 0 . 0 s h r e d d e r ; h e r b i v o r e 0 73 T r i a n o d e s s p p . 1 0 . 0 s h r e d d e r ; h e r b i v o r e 0 0 0 0 0 O r d e r D i p t e r a F a m i l y C u l i c i d a e 74 A e d e s c a m p e s t r i s D y a r & Knab 1 1 . 5 c o l l e c t o r ; f i l t e r f e e d e r 0 0 75 A . f i t c h i i ( F e l t * Y o u n g ) 1 1 . 5 c o l l e c t o r ; f i l t e r f e e d e r 0 76 A . f l a v e s c e n s ( M u l l e r ) 1 1 . 5 c o l l e c t o r ; f i l t e r f e e d e r 0 77 C h a o b o r u s a m e r i c a n u s ( J o h a n n s e n ) 1 1 . 5 p r e d a t o r ; e n g u l f e r 0 0 0 0 0 F a m i l y C h i r o n o m i d a e 78 M a c r o p e l o p i i n l 1 0 . 0 p r e d a t o r ; e n g u l f e r 0 0 0 0 79 P e n t a n e u r i n i 1 0 . 0 p r e d a t o r ; e n g u l f e r 0 0 8 0 C h i r o n o m i n i 1 0 . 0 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 0 0 0 0 0 0 81 T a n y t a r s i n i 1 0 . 0 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 0 82 O r t h o c l a d i i n i / M e t r i o c n e m i n i 1 0 . 0 c o l l e c t o r ; s e d i m e n t f e e d e r 0 0 0 0 0 0 F a m i l y H e l e i d a e 8 3 A l l u a u d o m y i a s p . 5 . 5 p r e d a t o r ; e n g u l f e r 0 84 B e z z i a / P r o b e z z i a s p . 9 . 5 p r e d a t o r ; e n g u l f e r 0 47 F i g . 5 . C l u s t e r a n a l y s i s o f a r t h r o p o d s p e c i e s based on s i m i l a r i t i e s o f l a k e s o c c u p i e d , r = 0 . 8 5 4 . P r i n c i p a l s u b g r o u p s , d e s i g n a t e d by stem l e t t e r s , a r e d i s c u s s e d i n t h e t e x t . (See T a b l e 7 f o r s p e c i e s names). 48 49 31 79 15 55 47 35 63 65 66 34 33 72 28 27 26 84 83 12 6 4 53 22 11 67 20 64 61 81 60 48 37 57 59 30 71 70 17 16 13 8 - 46 -45 • 44 - 80 -42 - 36 - 32 - 29 - 9 - 51 - 4 0 - 77 - 3 8 - 14 E3 U Species 25 24 5 23 21 - 76 - 75 - 69 - 10 -54 -82 - 78 - 74 - 5 8 - 68 -19 - 56 -52 - 4 3 - 39 -18 -3 -1 0 0.2 0.4 0.6 0.8 1.0 Similarity 49 Legend f o r F i g s . 6 - 1 2 : C o m p o s i t i o n and r e l a t i v e abundance o f a r t h r o p o d (a) s p e c i e s and (b) e c o l o g i c a l c a t e g o r i e s i n t h e e i g h t study l a k e s . - = <5 % m = 5-10 % ffl = 10-25 % M = 25-50 % 50-100 % See F i g . 1 f o r l a k e names; see T a b l e 7 f o r s p e c i e s names; t r o p h i c l e v e l s a r e as f o l l o w s : a = s h r e d d e r ; h e r b i v o r e b = c o l l e c t o r ; f i l t e r f e e d e r c = c o l l e c t o r ; sediment f e e d e r e = p r e d a t o r ; e n g u l f e r f = p r e d a t o r ; p i e r c e r Numbers 1-10 accompanying t r o p h i c l e v e l s r e f e r t o i n c r e a s i n g body s i z e ; t h e s e numbers i n t h e v a r i o u s sample s e t s are n o t c o m p a r a b l e . Dashed l i n e s i n (b) p a r t o f F i g u r e s s e p a r a t e t r o p h i c l e v e l s . E c o l o g i c a l c a t e g o r i e s w i t h i n each t r o p h i c l e v e l a r e p r e s e n t e d i n o r d e r o f i n c r e a s i n g s i z e . 50 F i g . 6 . L i m n e t i c z o o p l a n k t o n c o l l e c t e d i n Van Dorn b o t t l e s . (See p g . 49 f o r l e g e n d ; see Appendix B . l f o r n u m e r i c a l v a l u e s ) . F i g . 7 . E n t o m o s t r a c a c o l l e c t e d i n l i g h t t r a p s a m p l e s . (See p g . 49 f o r l e g e n d ; see Appendix B.2 f o r n u m e r i c a l v a l u e s ) . 51 % 17 13 8 2 3 14 7 9 5 11 2 19 18 3 10 b1 b 3 b 4 b 5 b 6 b7 e 3 e 4 e 6 Species Trophic level 52 i n h i g h l y s a l i n e o n e s . In both l i m n e t i c and l i g h t t r a p s a m p l e s , two h i g h l y v a r i a b l e s p e c i e s , Daphnia p u l e x and D. s c h 0 d 1 e r i were lumped t o g e t h e r because they were d i f f i c u l t t o d i s t i n g u i s h m o r p h o l o g i c a l l y . Two p a i r s o f s p e c i e s , Daphnia r o s e a / c a t a w b a and C y c l o p s v e r n a l i s / n a v u s were a l s o lumped t o g e t h e r i n l i g h t t r a p samples as t h e amount o f t i m e r e q u i r e d t o s e p a r a t e t h e s e p a i r s was p r o h i b i t i v e w i t h the volume o f m a t e r i a l . Lake 1 , the most f r e s h w a t e r , i s dominated by Daphnia r o s e a and D. c a t a w b a , s p e c i e s unique t o t h i s l a k e , whereas m o d e r a t e l y s a l i n e Lakes 2 - 5 a l l have s i m i l a r s p e c i e s ensembles dominated by Daphnia p u 1 e x / s c h 0 d l e r i . These l a k e s d i f f e r e d from each o t h e r i n t h e p r e s e n c e o r absence and r e l a t i v e abundance o f minor s p e c i e s . For e x a m p l e , o n l y Lakes 4 and 5 s u p p o r t e d p o p u l a t i o n s o f Daphnia  magna, b u t not as a major component o f t h e community. High s a l i n i t y Lakes 6 , 7 and 8 were dominated by t h e c a l a n o i d copepods Diaptomus s i c i l i s and D.  n e v a d e n s i s , and t h e c l a d o c e r a n Daphnia s i m i l i s ; o n l y Lake 8 c o n t a i n e d t h e h a l o b i o n t c l a d o c e r a n Moina h u t c h i n s o n i . Entomostraca c o l l e c t i o n s i n w a t e r b o t t l e and l i g h t t r a p samples were s i m i l a r , b u t some d i f f e r e n c e s a r e as f o l l o w s : (1) L i g h t t r a p samples showed Diaptomus n e v a d e n s i s r a t h e r than D. s i c i l i s as t h e dominant copepod i n s a l i n e l a k e s . (2) S e v e r a l t y p i c a l l i t t o r a l s p e c i e s , namely L e y d i g i a  q u a d r a n g u l a r a , S c a p h o l e b e r i s k i n g i , Simocephalus v e t u l u s and M a c r o c y c l o p s  a l b i d u s , were more common i n t h e l i t t o r a l than l i m n e t i c z o n e . (3) Water b o t t l e samples i n c l u d e d c e r t a i n d i p t e r a n l a r v a e , namely, Chaoborus  americanus and c h i r o n o m i d s . C h i r o n o m i d s were not i d e n t i f i e d beyond f a m i l y l e v e l s i n c e most were e a r l y i n s t a r s . In the l i m n e t i c zone o f the study l a k e s , t h e s e D i p t e r a o c c u r r e d a t such h i g h d e n s i t i e s (Chaoborus c o m p r i s e d 11% o f the community i n Lake 2) t h a t I c o n s i d e r them i m p o r t a n t t o the f u n c t i o n i n g community, even though they a r e not n o r m a l l y c o n s i d e r e d members 53 o f the l i m n e t i c z o o p l a n k t o n . A l t h o u g h d i p t e r a n s were p r e s e n t i n l i g h t t r a p s a m p l e s , they were i n c l u d e d o n l y i n a n a l y s i s o f t h e e n t i r e l i g h t t r a p community, and not i n the e n t o m o s t r a c a n s u b s e t . There was a marked d i f f e r e n c e i n t h e r e l a t i v e abundance o f z o o p l a n k t o n e c o l o g i c a l c a t e g o r i e s between low t o moderate and h i g h s a l i n i t y l a k e s ( F i g . 6 b ; 7 b ) . L a k e s 1-5 a l l had s m a l l f i l t e r f e e d i n g h e r b i v o r e s ( C h y d o r u s , C e r i o d a p h n i a ) , and were dominated by l a r g e f i l t e r f e e d e r s ( D a p h n i a ) . More s a l i n e l a k e s a r e a l s o dominated by l a r g e f i l t e r f e e d e r s ( D a p h n i a ) , b u t had no s m a l l f i l t e r f e e d e r s . L i m n e t i c samples showed p r o p o r t i o n a t e l y more medium s i z e d f i l t e r f e e d e r s i n s a l i n e l a k e s than l i g h t t r a p s d i d , owing t o h i g h e r c a t c h e s o f Diaptomus s i c i l i s . F r e s h t o m o d e r a t e l y s a l i n e l a k e s have s m a l l and l a r g e p r e d a t o r s ( c y c l o p o i d s and d i p t e r a n s r e s p e c t i v e l y ) , b u t t h e r e were no medium s i z e d o n e s . C o n v e r s e l y , s a l i n e l a k e s had some medium s i z e d p r e d a t o r s ( c a l a n o i d s ) , b u t no s m a l l o r l a r g e o n e s . No l a r g e p r e d a t o r s a r e shown i n F i g . 7b as the d i p t e r a n l a r v a e r e p r e s e n t i n g t h i s c a t e g o r y were not i n c l u d e d i n l i g h t t r a p s a m p l e s . In s a l i n e Lakes 6 - 8 , p r o p o r t i o n a t e l y more medium s i z e d p r e d a t o r s were found i n l i g h t t r a p s than b o t t l e samples owing t o h i g h e r c a t c h e s o f D. n e v a d e n s i s . LIGHT TRAPS. S p e c i e s c o m p o s i t i o n and r e l a t i v e abundance o f the 70 a r t h r o p o d s p e c i e s c o l l e c t e d i n l i g h t t r a p s d i f f e r e d markedly among l a k e s ( F i g . 8 a ) . A l l l a k e s were n u m e r i c a l l y dominated by s p e c i e s o f C l a d o c e r a and Copepoda. A l l i n d i v i d u a l s were i d e n t i f i e d t o s p e c i e s where p o s s i b l e a l t h o u g h t h e r e were e x c e p t i o n s . S p e c i e s lumping o f C l a d o c e r a and Copepoda i s mentioned a b o v e . Chironomidae were i d e n t i f i e d t o t r i b e as f u r t h e r i d e n t i f i c a t i o n was t o o t i m e consuming o r i m p o s s i b l e w i t h e a r l y i n s t a r s . F o r t u n a t e l y , most c h i r o n o m i d s p e c i e s w i t h i n a t r i b e b e l o n g t o the same e c o l o g i c a l c a t e g o r y . 47 48 48 56 63 33 34 72 27 28 26 79 8384 ^6 44 60 61 37 31 17 16 51 38 13 14 8 15 59 62 40 36 77 23 50 41 30 7 9 57 45 73 29 81 42 32 35 78 80 822/%2M 5 2 4 25 46 11 2 19 75 76 56 52 39 43 74 3 18 1 10 Species Fig. 8a. All species collected in light trap samples. (See pg. 49 for legend; see Appendix B.2 for numerical values). 55 F i g . 8 b . A l l e c o l o g i c a l c a t e g o r i e s c o l l e c t e d i n l i g h t t r a p s a m p l e s . (See p g . 49 f o r l e g e n d ; see Appendix B.2 f o r n u m e r i c a l v a l u e s ) . 56 A l l l a k e s were n u m e r i c a l l y dominated by l a r g e s i z e d f i l t e r f e e d e r s ( D a p h n i a ) , as shown i n F i g . 8b p r e s e n t i n g the d i s t r i b u t i o n and r e l a t i v e abundance o f e c o l o g i c a l c a t e g o r i e s i n l i g h t t r a p s a m p l e s . Low s a l i n i t y l a k e s had s m a l l f i l t e r f e e d e r s ( C e r i o d a p h n i a , S c a p h o l e b e r i s , C h y d o r u s ) , b u t no v e r y l a r g e ones and had a wide s i z e range o f sediment f e e d e r s . C o n v e r s e l y , s a l i n e l a k e s had v e r y l a r g e f i l t e r f e e d e r s ( B r a n c h i n e c t a ) , b u t no v e r y s m a l l ones and o n l y m i d - s i z e sediment f e e d e r s ( C h i r o n o m i n i , C a l l i b a e t i s ) . P r e d a t o r s were p r e s e n t i n a l l l a k e s , b u t s a l i n e l a k e s had fewer s i z e c l a s s e s and p r o p o r t i o n a t e l y more i n d i v i d u a l s . COLEOPTERA. T w e n t y - e i g h t C o l e o p t e r a s p e c i e s were c o l l e c t e d i n the e i g h t l a k e s , 18 i n l i g h t t r a p s ; 27 i n sweep s a m p l e s , and l a k e s d i f f e r n o t i c e a b l y i n t h e i r c o m p o s i t i o n and r e l a t i v e abundance ( F i g s . 9 a ; 1 0 a ) . A l l c o l e o p t e r a n s caught i n l i g h t t r a p s were i n the f a m i l i e s H a l i p l i d a e and D y t i s c i d a e , w h i l e sweep n e t s a l s o c a u g h t members o f the H y d r o p h i l i d a e and C u r c u l i o n i d a e . S e v e r a l h e r b i v o r o u s s p e c i e s , H a l i p i us i m m a c u l i c o l l i s , H.  s t r i g a t u s , L i t o d a c t y l u s g r i s e o m i c a n s , L i x e l l u s f i 1 i f o r m i s , Enochrus  d i f f u s u s and L a c c o b i u s s p p , were more common i n sweep samples than l i g h t t r a p s . Sweep n e t s c o l l e c t e d more s p e c i e s than l i g h t t r a p s , b u t t h e i r n u m e r i c a l abundance was v e r y v a r i a b l e . L i g h t t r a p samples o f b e e t l e communities i n t h e most s a l i n e Lakes 7 and 8 were composed a l m o s t e x c l u s i v e l y o f Hygrotus m a s c u l i n u s , a t y p i c a l h i g h s a l i n i t y s p e c i e s t h a t a l s o o c c u r r e d i n Lake 6 , b u t i n t h e company o f abundant Agabus a j a x and H a l i p l u s s t a g n i n u s . Lakes 2-5 were c h a r a c t e r i z e d by abundant p o p u l a t i o n s o f H. s t a g n i n u s and Rhantus f r o n t a l i s , e x c e p t Lake 4 where R. f r o n t a l i s was not f o u n d , b u t Hygrotus u n g u i c u l a r i s was r e l a t i v e l y common. Lake 1 was unusual i n t h a t i t c o n t a i n s more s p e c i e s than any o t h e r , s e v e r a l were u n i q u e , and two unique s p e c i e s ( H a l i p l u s 57 F i g . 9. C o l e o p t e r a c o l l e c t e d i n l i g h t t r a p s a m p l e s . (See p g . 49 f o r l e g e n d ; see Appendix B.2 f o r n u m e r i c a l v a l u e s ) . F i g . 10. L i t t o r a l C o l e o p t e r a c o l l e c t e d i n sweep l e g e n d ; see Appendix B.3 f o r n u m e r i c a l n e t s . (See p g . 49 f o r v a l u e s ) . 58 5547 65 66 48 60 61 51 57 59 50 49 62 44 45 67 71 70 64 46 53 69 54 68 58 52 56 al a2 a3 el e2 e3 64 e5 e6 e8 Species Trophic level 59 l e e c h i and Hydroporus g r i s e o s t r i a t u s ) were abundant. The c o m p o s i t i o n and r e l a t i v e abundance o f e c o l o g i c a l c a t e g o r i e s i s shown i n F i g . 9 b . The d i v i s i o n between p r e d a t o r s and s h r e d d e r s c o i n c i d e s w i t h a taxonomic d i v i s i o n between t h e f a m i l i e s D y t i s c i d a e and H a l i p l i d a e . As s a l i n i t y i n c r e a s e d , h e r b i v o r e s ( H a l i p l u s s p p . ) were fewer and s m a l l e r . Lake 1 had a wide range o f p r e d a t o r s i z e s o c c u r r i n g w i t h more o r l e s s equal abundance, m o d e r a t e l y s a l i n e l a k e s a l s o had a wide range o f p r e d a t o r s i z e s b u t were dominated by medium s i z e d forms ( R h a n t u s ) , and h i g h l y s a l i n e l a k e s were p o p u l a t e d a l m o s t e x c l u s i v e l y by s m a l l p r e d a t o r s ( H y g r o t u s ) . U n l i k e l i g h t t r a p s a m p l e s , sweep samples showed no s t r o n g p a t t e r n i n the r e l a t i v e abundance o f taxonomic s p e c i e s o r e c o l o g i c a l c a t e g o r i e s a c r o s s l a k e s ( F i g . 1 0 ) . Lake 1 had some unique s p e c i e s and some s p e c i e s were r e s t r i c t e d t o h i g h l y s a l i n e l a k e s , b u t no s t r o n g p a t t e r n i s a p p a r e n t . One i m p o r t a n t f e a t u r e , however, i s t h e abundance of h e r b i v o r e s i n a l l l a k e s . HEMIPTERA. Compared t o o t h e r g r o u p s , t h e r e were r e l a t i v e l y few h e m i p t e r a n s i n t h e s e l a k e s . F i g s . 11 and 12 show t h e c o m p o s i t i o n and r e l a t i v e abundance o f Hemiptera s p e c i e s and e c o l o g i c a l c a t e g o r i e s , i n l i g h t t r a p and sweep s a m p l e s . There was a marked d i f f e r e n c e i n s p e c i e s c o m p o s i t i o n above and below c o n d u c t i v i t i e s o f 5000 uS (Lakes 1-5 v s . 6 - 8 ) ( F i g s . 11a; 1 2 a ) . C e n o c o r i x a b i f i d a was r e l a t i v e l y abundant i n a l l l a k e s , a l l o t h e r s p e c i e s were t y p i c a l o f e i t h e r h i g h o r low s a l i n i t y l a k e s . The h a l o b i o n t , D a s y c o r i x a r a w s o n i , was c a u g h t more o f t e n i n l i g h t t r a p s than i n sweep n e t s , however, both t e c h n i q u e s p r o v i d e d s i m i l a r r e p r e s e n t a t i o n s o f t h e h e m i p t e r a n f a u n a . A l l t h e s e Hemiptera a r e i n the same t r o p h i c l e v e l ( p r e d a t o r ; p i e r c e r ) so F i g s , l i b and 12b p r e s e n t t h e r e l a t i v e abundance o f s i z e c a t e g o r i e s w i t h i n t h i s l e v e l . Lake 1 c o n t a i n e d a wide range o f s i z e forms b u t as s a l i n i t y i n c r e a s e d , o n l y s m a l l s i z e c l a s s e s were r e p r e s e n t e d . 60 F i g . 1 1 . Hemiptera c o l l e c t e d i n l i g h t t r a p s a m p l e s . (See p g . 49 f o r l e g e n d ; see Appendix B.2 f o r n u m e r i c a l v a l u e s ) . F i g . 1 2 . L i t t o r a l Hemiptera c o l l e c t e d i n sweep n e t s . (See p g . 49 f o r l e g e n d ; see Appendix B . 3 f o r n u m e r i c a l v a l u e s ) . 62 COMMUNITY PARAMETERS Community s t r u c t u r e i n t h e 7 sample s e t s was n u m e r i c a l l y c h a r a c t e r i z e d a c c o r d i n g t o 13 community parameters i n each sample s e t , and t h e s e are p r e s e n t e d i n T a b l e 8 . Important f e a t u r e s o f t h i s t a b l e a r e as f o l l o w s : (1) E u c l i d e a n d i s t a n c e s a r e a measure o f d i s s i m i l a r i t y so v a l u e s i n c r e a s e f o r more d i s s i m i l a r c o m m u n i t i e s . (2) In g e n e r a l , Lake 1 had the l a r g e s t number o f s p e c i e s and e c o l o g i c a l c a t e g o r i e s y e t the l o w e s t d e n s i t y . N o t a b l e e x c e p t i o n s were i n both l i m n e t i c and l i g h t t r a p z o o p l a n k t o n samples where maximum v a l u e s f o r most community parameters o c c u r r e d i n t h e m o d e r a t e l y s a l i n e Lake 4 . (3) Entomostracans made up a p p r o x i m a t e l y 95% o f a l l i n d i v i d u a l s c o l l e c t e d i n l i g h t t r a p s . (4) T o t a l s p e c i e s d i v e r s i t y was g e n e r a l l y l o w , never e x c e e d i n g 1 . 9 6 . (5) The d e n s i t y o f b e e t l e s i n sweep samples was v e r y l o w . (6) The super community i n d e x Q j ( s ) never a c h i e v e d the maximum v a l u e o f 1 . 0 0 , and Q j ( t i ) r a r e l y d i d . T a b l e 9 summarizes r e l a t i o n s h i p s between community parameters o f z o o p l a n k t o n and Hemiptera s e t s . In g e n e r a l , parameters f o r l i m n e t i c z o o p l a n k t o n a r e p o s i t i v e l y c o r r e l a t e d w i t h t h o s e i n l i g h t t r a p Entomostraca c o m m u n i t i e s , and parameters f o r sweep Hemiptera a r e c o r r e l a t e d w i t h l i g h t t r a p H e m i p t e r a . No l i g h t t r a p and sweep c o l e o p t e r a n community parameters a r e c o r r e l a t e d . Each f a u n a l community had d i s t i n c t l y d i f f e r e n t p a r a m e t e r s . F i g . 13 shows t h e mean and v a r i a t i o n o f l i m n e t i c z o o p l a n k t o n d i v e r s i t y i n t h r e e l a k e s , r e p r e s e n t a t i v e o f the whole s e r i e s . The 48 samples o f each l a k e were grouped i n t o f o u r groups o f f o u r a d j a c e n t sample t i m e s , each c o n s i s t i n g o f 12 i n d i v i d u a l s a m p l e s . Each l a k e i s undoubtedly d i f f e r e n t from the o t h e r s . Water c h e m i s t r y appears t o be the b e s t a b i o t i c v a r i a b l e f o r p r e d i c t i n g 63 Table 8. Numerical values for faunal community parameters. Maximum values are in bold type. (See F i g . 1 for lake names; see Table 6 for explanation of symbols). Community parameter lake D s t i H'(s) H" ( t i ) H'(t) H' t(s) H'ti<s) H' t(i) Qj(s) Q j ( t i ) 0d(s) Qd(ti) WATER BOTTLE - ZOOPLANKTON 1 41.3 13 7 1.30 1.13 0.52 0.78 0.17 0.61 . 5 9 1 .700 9 . 4 8 8 6.818 2 21.6 9 6 0.94 0.89 0.56 0.38 0.05 0.33 .409 .600 12.147 8.310 3 37 .2 7 5 0.31 0.29 0.25 0.05 0.01 0.04 .318 .500 12.021 8.285 4 1 5 8 . 5 12 8 1 . 7 8 1 . 3 6 0 . 5 8 1 . 2 0 0 . 4 2 0 . 7 9 .545 . 8 0 0 9.761 5 . 5 4 3 5 86.3 10 8 0.78 0.66 0.48 0.30 0.12 0.18 .455 . 8 0 0 11.321 6.949 6 26.3 3 3 0.16 0.49 0.00 0.49 0.00 0.65 .136 .300 12.100 7.887 7 74.7 5 4 0.54 0.53 0.08 0.46 0.01 0.45 .227 .400 12.140 7.796 8 47.4 4 4 0.75 0.75 0.04 0.71 0.00 0.71 .182 .400 12.080 8.276 SWEEP - COLEOPTERA 1 11.4 8 6 1.26 0.98 0.64 0.62 0.28 0.33 .296 . 6 0 0 12.202 6.458 2 2 4 . 9 10 6 1.61 1.34 0.67 0.94 0.27 0 . 6 7 .370 . 6 0 0 1 2 . 0 3 1 5 . 1 1 2 3 3.0 10 6 1.46 1.31 0.68 0.83 0.15 0.63 .370 . 6 0 0 13.582 7.643 4 6.3 5 4 0.85 0.62 0.43 0.66 0.23 0.19 .185 .401 13.785 7.346 5 8.2 9 6 1.77 1.28 0.68 1.17 0.49 0.60 .333 . 6 0 0 12.780 6.601 6 3.2 11 6 1 . 9 6 1.31 0 . 6 9 1 . 2 7 0 . 6 5 0.62 . 4 0 7 . 6 0 0 12.767 7.237 7 2.1 4 3 0.67 0.62 0.50 0.05 0.05 0.12 .148 .300 14.101 7.798 8 4.1 7 6 1.70 1 . 6 9 0.56 1.14 0.01 1.13 .259 . 6 0 0 13.312 6.461 SWEEP - HEMIPTERA 1 31.5 5 3 1 . 3 8 1 . 0 7 0.32 .625 1 . 0 0 6 . 0 7 3 3.593 2 49.8 6 3 1.17 0.93 0.25 . 7 5 0 1 . 0 0 6.150 3 . 0 7 1 3 54.5 5 3 0.69 0.56 0.13 .625 1 . 0 0 7.213 3.936 4 88.1 4 3 0.34 0.32 0.02 .500 1 . 0 0 7.313 3.905 5 41.0 5 3 0.87 0.76 0.11 .625 1 . 0 0 7.267 3.911 6 259.3 5 3 0.43 0.05 0.38 .625 1 . 0 0 6.666 2.903 7 9.6 3 1 0.47 0.00 0.47 .375 .333 7.698 4.742 8 5 0 6 . 4 3 2 0.69 0.01 0 . 6 9 .375 .667 6.896 3.810 Table 8. CONT. 64 Community parameter lake D s t i H'(s) H'(ti) H'(t) H' t(s) H' t 1(s) H' t(i) Q j(s) Qj ( t i ) Q d(s) Q d ( t i ) LIGHT TRAP - ALL SPECIES 1 1191 51 25 1.17 2 11551 36 21 0.55 3 5 4 3 5 6 24 17 0.11 4 33770 28 20 1.17 5 17603 24 18 0.73 6 16988 23 15 0.40 7 20280 17 13 0.64 8 10882 16 12 1 . 5 1 LIGHT TRAP - ENTOMOSTRACA 1 1031 9 6 0.56 2 10859 9 6 0.26 3 5 3 7 5 8 8 5 0.04 4 33239 11 7 1.09 5 17279 6 6 0.62 6 16812 6 5 0.33 7 20124 3 3 0.58 8 9347 5 4 1 . 1 0 LIGHT TRAP - COLEOPTERA 1 27.4 14 8 1 . 8 2 2 56.5 10 6 0.88 3 25.8 3 3 0.64 4 28.8 3 3 0.41 5 63.2 4 4 0.76 6 31.6 5 4 1.03 7 90.2 4 3 0.06 8 3 6 9 . 0 1 1 0.00 LIGHT TRAP - HEMIPTERA 1 41.6 6 3 1 . 4 2 2 93.4 6 3 1.41 3 179.0 4 3 0.75 4 312.0 5 3 0.60 5 102.2 4 3 0.71 6 169.8 4 2 1.08 7 153.2 3 1 1.00 8 3 4 7 . 6 3 1 0.78 1.10 0 . 6 8 0.50 0.53 0.29 0.26 0.10 0.07 0.04 1.03 0.18 0.99 0.73 0.25 0.49 0.39 0.06 0.33 0.63 0.05 0.59 1 . 4 6 0.45 1 . 0 7 0.53 0.16 0.41 0.26 0.03 0.23 0.02 0.01 0.03 0 . 9 4 0.09 1 . 0 0 0.62 0.15 0.47 0.32 0.31 0.02 0.58 0 . 5 3 0.05 0.70 0.44 0.66 1 . 5 8 0 . 6 7 1 . 1 6 0.68 0.41 0.47-0.64 0.55 0.09 0.41 0.35 0.06 0.76 0.65 0.11 1.01 0.25 0.78 0.03 0.03 0.03 0.00 0.00 0.00 0.85 0 . 8 7 0.67 0.50 0.62 0.04 0.00 0.00 0.07 0.43 . 7 2 9 0.02 0.24 .514 0.01 0.03 .343 0 . 1 4 0.86 .400 0.01 0.48 .343 0.01 0.32 .329 0.01 0.58 .243 0.06 1 . 0 1 .229 0.03 0.38 .563 0.01 0.23 .563 0.01 0.02 .500 0.14 0 . 8 6 . 6 8 8 0.00 0.47 .375 0.01 0.01 .375 0.00 0.05 .188 0 . 4 0 0.26 .313 0 . 2 5 0.91 . 7 7 8 0.20 0.27 .556 0.00 0 . 9 3 .167 0.00 0.06 .167 0.00 0.11 .222 0.02 0.76 .278 0.03 0.01 .222 0.00 0.00 .056 0.57 . 7 5 0 0.54 . 7 5 0 0.09 .500 0.10 .625 0.09 .500 1 . 0 5 .500 1.00 .375 0.78 .375 . 8 6 2 1 6 . 6 0 5 11.425 .724 19.262 13.278 .586 20.561 12.679 .690 19.391 1 1 . 2 6 2 .621 20.35 12.968 .517 21.450 13.810 .448 21.498 13.813 .414 21.024 12.880 .750 9.376 7.214 .750 10.014 7.088 .625 9.399 7.140 . 8 7 5 7 . 4 3 0 4 . 4 5 0 .750 9.513 6.125 .500 10.338 7.265 .375 10.144 7.001 .500 9.762 7.446 1 . 0 0 6 . 8 6 0 5 . 3 0 2 .750 9.307 5.941 .375 10.870 6.979 .375 10.518 6.390 .500 10.408 6.623 .500 10.518 6.720 .375 10.705 7.384 .125 10.995 7.271 1 . 0 0 6.815 4.577 1 . 0 0 6 . 0 4 2 3.721 1 . 0 0 6.494 3.157 1 . 0 0 6.265 2 . 7 9 7 1 . 0 0 6.755 4.062 .667 6.890 4.418 .333 7.031 4.513 .333 6.648 4.120 65 Table 9. Summary of relationships between community parameters, based on Pearson's product-moment correlation coefficient. - = no association. Positive associations: + = p<0.10; ++ = p<0.05; +++ = p<0.01. Negative associations: ** = p<0.05. (See Table 6 for symbol description; Appendix C for numerical values). WATER BOTTLE ZOOPLANKTON '—' -—' * r — (/) " r — ••—' •—* - f — . — 'r-</> 4-> 4-> ^ « — ^ in 4-> 10 4 J 1 — - - - - - - i - 3 i-g "O X 3 Q W * J l 3 T 3 : i 3 : 3 : 0 ' O r O r O ' D s ++ ti +++ H'(s) + H'(t) ** LIGHT H'(ti) + TRAP H' t(s) ++ ENTOMOSTRACA H' t(i) H' t 1(s) Qj(s) ++ Qj (ti) +++ Qd(s) ++ Qd(ti) +++ SWEEP HEMIPTERA •~3 '-3 "O "O o- o- o- o-D + S ++ ti +++ LIGHT H'(s) ++ TRAP H'(ti) +++ HEMIPTERA H'ti(s) ++ Qj(s) Qj(ti) Qd(s) Qd(ti) ++ +++ 66 1.5 1.0 • I— > 0.5' 0 r i 5 2 3 Time F i g . 1 3 . Mean and s t a n d a r d e r r o r o f d i v e r s i t y vs time i n l i m n e t i c z o o p l a n k t o n samples i n t h r e e l a k e s . ^ = Lake 3 , # = Lake 4, O = Lake 6 . (See F i g . 1 f o r l a k e names). 67 Table 10. Summary of relationships between community parameters and physiochemical variables based on Pearson's product-moment c o r r e l a t i o n c o e f f i c i e n t . Negative associations: * = p<0.10; ** = p<0.05; *** = p<0.01; pos i t i v e associations: + = p<0.10; ++ = p<0.05; +++ = p<0.01. See Table 6 for description of community parameter symbols; k 25 = conductivity; z = mean depth. (See Appendix D for numerical parameters). Community parameter Variable D s t i H'(s) H'(t) H'(ti) H' t(s) H' t(1) H' t i(s) Qj(s) Q j ( t i ) Qd(s) Qd(ti) WATER 80TTLE - ZOOPLANKTON l^2j ** * *** - - _ _ * * logk25 - * * - - * - - - - * * PCI _ * * * _ * . _ _ _ * * PC2 - - - - - - - - - -z **• oLA - - - - • SWEEP - COLEOPTERA k25 logk 25 -PCI PC2 z * °LA SWEEP - HEMIPTERA k25 logk 25 PCI PC2 z °LA ** ** ** ** ** +++ *** *** *** **• +++ ** ** 68 T a b l e 10. CONT. Community parameter V a r i a b l e 0 s t i H'(s) H ' ( t ) H ' ( t i ) H ' t ( s ) H ' t H) H ' t i ( s ) Q j ( s ) O j ( t i ) Qd(s) LIGHT TRAP - ALL SPECIES k 2 5 - ** *** - - - - - #* *** ++ -l o g k 2 5 - *** *** - * - - - *** *** +++ PCI - ** *** - - - + - ** **• + -PC2 - - - - - - - - - -z - ** *** - * - - - ** ** +++ ++ °LA - + + - - - - - + + -LIGHT TRAP - ENTOMOSTRACA k 2 5 - ** ** - +++ - - - ** ** -l o g k 2 5 - * - - - - - * - -PCI - ** * - + - - - ** -PC2 - - - - - - - - - -z - - ++ - - - ** *** -D L A - - - - - - - - - -LIGHT TRAP - COLEOPTERA k 2 5 ++ * ** * *** * - - * ** ++ l o g k 2 5 - *** *** ** ** ** * * ** *** *** +++ ++• PCI ++ * * *** * - - - * ++ PC2 - - - - - - - - - -z - * * - ** - - * * * + ++ \ A *** + + - + - - + + + * LIGHT TRAP - HEMIPTERA k 2 5 - *** *** - *** *** -l o g k 2 5 + *** * - ** - *** * -PCI - ** *** - *** + ** *** -PC2 - - - - - - - -z - ** ** - *** + ** -°LA * + + - ++ - + + -69 community p a r a m e t e r s , as both c o n d u c t i v i t y and PCI show s i g n i f i c a n t c o r r e l a t i o n s o r t r e n d s w i t h s e v e r a l p a r a m e t e r s ; PC2 i s n o t a s s o c i a t e d w i t h any p a r a m e t e r s . A l t h o u g h mean depth i s a s s o c i a t e d w i t h s e v e r a l p a r a m e t e r s , t h e s i g n o f o b s e r v e d r e l a t i o n s h i p s i s c o n t r a r y t o p r e d i c t i o n s . T a b l e 10 summarizes t h e r e l a t i o n s h i p s between community parameters ( T a b l e 8) and a b i o t i c v a r i a b l e s ( T a b l e s 2 , 3 and 4 ) . Mean depth i s n e g a t i v e l y c o r r e l a t e d w i t h s e v e r a l parameters and D|_^  o f t e n shows a p o s i t i v e t r e n d w i t h community p a r a m e t e r s . In a l l b u t one sample s e t , i n c r e a s i n g s a l i n i t y i s accompanied by a d e c r e a s e i n the a b s o l u t e number o f s p e c i e s [ s ] and e c o l o g i c a l c a t e g o r i e s [ t i ] , and i n t h e r e l a t i v e number o f s p e c i e s [ Q j ( s ) ] and e c o l o g i c a l c a t e g o r i e s [ Q j ( t i ) ] , w i t h r e s p e c t t o the t o t a l number a v a i l a b l e f o r c o l o n i z a t i o n . The s o l e e x c e p t i o n i s found i n the s e t o f C o l e o p t e r a sampled i n the l i t t o r a l zone w i t h sweep n e t s . Other a s s o c i a t i o n s between p h y s i o c h e m i c a l v a r i a b l e s and community parameters v a r y depending on the sample s e t . L i m n e t i c z o o p l a n k t o n show a s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n between s a l i n i t y and t r o p h i c l e v e l d i v e r s i t y , H ' ( t ) . C u r i o u s l y , t h i s a s s o c i a t i o n i s p o s i t i v e i n l i g h t t r a p Entomostraca s a m p l e s , and t h i s c o n t r a d i c t i o n i s a t t r i b u t a b l e t o the d i f f e r e n t i a l s a m p l i n g o f p r e d a t o r s by the two t e c h n i q u e s . In l i m n e t i c s a m p l e s , the m a j o r i t y o f p r e d a t o r s were found i n f r e s h w a t e r l a k e s , whereas l i g h t t r a p s c o l l e c t e d more i n s a l i n e l a k e s . When a l l s p e c i e s i n l i g h t t r a p c o l l e c t i o n s were used t o c a l c u l a t e community p a r a m e t e r s , the c o m p l e x i t y o f sample c o m m u n i t i e s , r e l a t i v e t o the maximum c o m p l e x i t y p o s s i b l e , d e c r e a s e s w i t h i n c r e a s i n g s a l i n i t y . None o f t h e t r a d i t i o n a l measures o f s p e c i e s d i v e r s i t y a r e a s s o c i a t e d w i t h s a l i n i t y , but t h e new super community i n d e x , Q d ( s ) , i s s i g n i f i c a n t l y c o r r e l a t e d , 70 and Q d ( t i ) shows a t r e n d . There i s a t r e n d f o r d e c r e a s i n g t r o p h i c l e v e l d i v e r s i t y w i t h i n c r e a s i n g s a l i n i t y , as seen i n the l i m n e t i c z o o p l a n k t o n . The r e l a t i o n s h i p s between community parameters and s a l i n i t y f o r the e n t i r e l i g h t t r a p c o l l e c t i o n a r e more s i m i l a r t o t h e e n t o m o s t r a c a n s u b s e t , than C o l e o p t e r a o r H e m i p t e r a . Where l i g h t t r a p and sweep n e t C o l e o p t e r a and Hemiptera communities were c o n s i d e r e d s e p a r a t e l y , t h e r e a r e many s i g n i f i c a n t r e l a t i o n s h i p s between s a l i n i t y and community p a r a m e t e r s . A g a i n , sweep n e t C o l e o p t e r a communities a r e anomalous showing v i r t u a l l y no a s s o c i a t i o n s between a b i o t i c v a r i a b l e s and community p a r a m e t e r s . F o r both C o l e o p t e r a and H e m i p t e r a , i n c r e a s i n g s a l i n i t y i s accompanied by i n c r e a s i n g d e n s i t y o f i n d i v i d u a l s , and d e c r e a s i n g d i v e r s i t y i n terms o f both t r a d i t i o n a l d i v e r s i t y i n d i c e s p l u s the new super community i n d i c e s . There a r e some s i g n i f i c a n t a s s o c i a t i o n s between D|_/\ and community parameters i n sweep s a m p l e s . CLASSIFICATION R e s u l t s o f the n u m e r i c a l c l a s s i f i c a t i o n o f taxonomic and e c o l o g i c a l s p e c i e s d a t a a r e shown i n F i g s . 14 - 2 0 . Most dendrograms a r e c o n s i d e r e d adequate r e p r e s e n t a t i o n s o f the o r i g i n a l d a t a as c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s a r e g r e a t e r than t h e c r i t i c a l l e v e l o f a c c e p t a n c e . The e x c e p t i o n s , F i g s . 17d, 1 8 b , 1 9 c , were o m i t t e d from f u r t h e r a n a l y s i s . C l u s t e r a n a l y s i s o f a l l sample s e t s c a l c u l a t e d from t h e p r e s e n c e o r absence o f s p e c i e s and e c o l o g i c a l c a t e g o r i e s w i t h J a c c a r d ' s c o e f f i c i e n t o f s i m i l a r i t y ( p a r t s a & b o f F i g s . 1 4 - 2 0 , 18b o m i t t e d ) produced dendrograms c l o s e l y r e l a t e d t o s a l i n i t y . In most c a s e s , dendrograms show a major dichotomy o f l a k e t y p e s w i t h one branch c o n t a i n i n g s a l i n e Lakes 6 - 8 and t h e o t h e r c o n t a i n i n g the more f r e s h w a t e r Lakes 1 - 5 , a p a t t e r n s i m i l a r t o 71 F i g . 14. C l u s t e r a n a l y s i s o f study l a k e s based on l i m n e t i c z o o p l a n k t o n : (a) s i m i l a r i t y o f s p e c i e s c o m p o s i t i o n , r=0.956 (b) s i m i l a r i t y o f e c o l o g i c a l c o m p o s i t i o n , r=0.977 ( c ) d i s s i m i l a r i t y o f s p e c i e s r e l a t i v e abundance, r=0.965 (d) d i s s i m i l a r i t y o f e c o l o g i c a l r e l a t i v e abundance, r=0.914 (See F i g . 1 f o r l a k e names). F i g . 1 5 . C l u s t e r a n a l y s i s o f study l a k e s based on l i g h t t r a p E n t o m o s t r a c a : (a) s i m i l a r i t y o f s p e c i e s c o m p o s i t i o n , r=0.923 (b) s i m i l a r i t y o f e c o l o g i c a l c o m p o s i t i o n , r=0.944 ( c ) d i s s i m i l a r i t y o f s p e c i e s r e l a t i v e abundance, r=0.891 (d) d i s s i m i l a r i t y o f e c o l o g i c a l r e l a t i v e abundance, r=0.896 (See F i g . 1 f o r l a k e names). 72 - 7 - 8 - 6 - 3 - 2 - 5 -4 - 1 ® 4 5 S 7 Lake 6 3 2 •© 0 . 4 0.6 Similarity ® Lake 6 4 Dissimilarity - 8 - 7 - 6 - 5 - 4 - 3 - 2 ® - 8 - 7 - 6 - 5 - 4 0 . 4 0.6 Similarity Lake © 6 4 Dissimilarity Lake c - „ ® 73 F i g . 1 6 . C l u s t e r a n a l y s i s o f study l a k e s based on a l l s p e c i e s i n l i g h t t r a p s : (a) s i m i l a r i t y o f s p e c i e s c o m p o s i t i o n , r=0.894 (b) s i m i l a r i t y o f e c o l o g i c a l c o m p o s i t i o n , r=0.859 ( c ) d i s s i m i l a r i t y o f s p e c i e s r e l a t i v e abundance, r=0.979 (d) d i s s i m i l a r i t y of e c o l o g i c a l r e l a t i v e abundance, r=0.924 (See F i g . 1 f o r l a k e names). 8 4 3 2 1 16 -\v-8 ^ — 7 2 Lake 10 0.4 0.6 Similarity 0.8 1.0 8 7 6 5 4 3 2 1 5^  10 6 4 Dissimilarity 4 •8 7 6 •3 5 -2 1 Lake 75 Fig. 17. Cluster analysis of study lakes based on light trap Coleoptera: (a) similarity of species composition, r=0.893 (b) similarity of ecological composition, r=0.902 (c) dissimilarity of species relative abundance, r=0.973 (d) dissimilarity of ecological relative abundance, r=0.789 (See Fig. 1 for lake names). Fig. 18. Cluster analysis of study lakes based on sweep net Coleoptera: (a) similarity of species composition, r=0.907 (b) similarity of ecological composition, r=0.627 (c) dissimilarity of species relative abundance, r=0.935 (d) dissimilarity of ecological relative abundance, r=0.936 (See Fig. 1 for lake names). 76 Lake © 0.4 0.6 Similarity -8 -7 -6 -4 -5 -3 -2 © 6 4 Dissimilarity Lake - o © - 2 -8 -6 -5 -4 -3 © Lake © 0.4 06 Similarity -5 -8 -8 -4 -7 -2 -3 6 4 Dissimilarity Lake I ® 77 F i g . 1 9 . C l u s t e r a n a l y s i s o f study l a k e s based on l i g h t t r a p H e m i p t e r a : (a) s i m i l a r i t y o f s p e c i e s c o m p o s i t i o n , r=0.978 (b) s i m i l a r i t y o f e c o l o g i c a l c o m p o s i t i o n , r=0.990 ( c ) d i s s i m i l a r i t y o f s p e c i e s r e l a t i v e abundance, r=0.800 (d) d i s s i m i l a r i t y o f e c o l o g i c a l r e l a t i v e abundance, r=0.886 (See F i g . 1 f o r l a k e names). F i g . 2 0 . C l u s t e r a n a l y s i s o f study l a k e s based on sweep n e t H e m i p t e r a : (a) s i m i l a r i t y o f s p e c i e s c o m p o s i t i o n , r=0.901 (b) s i m i l a r i t y o f e c o l o g i c a l c o m p o s i t i o n , r=0.994 ( c ) d i s s i m i l a r i t y o f s p e c i e s r e l a t i v e abundance, r=0.913 (d) d i s s i m i l a r i t y o f e c o l o g i c a l r e l a t i v e abundance, r=0.839 (See F i g . 1 f o r l a k e names). 78 C - ® 0.4 0 . 6 Similarity 0 . 8 c 6 p 4 - 3 -2 -5 '— 1 ® Lake Lake ® Dissimilarity -c ® 0 4 0 . 6 Similarity 0 . 8 . -7 -8 1 — 5 •4 — 3 — 2 — 6 •1 1.0 ® Lake 6 4 Dissimilarity HI Lake H I ; -„® 79 p h y s i o c h e m i c a l dendrograms ( F i g . 4 ) . D e t a i l s o f the c l u s t e r i n g o f Lakes 1-5 i s dependent on s a m p l i n g t e c h n i q u e and whether taxonomic s p e c i e s o r e c o l o g i c a l c a t e g o r i e s a r e employed. E x c e p t i o n s t o t h i s p a t t e r n are seen i n C o l e o p t e r a communities where dendrograms ( F i g s . 1 7 a , 17b, 18a) a r e c l e a r l y r e l a t e d t o s a l i n i t y , a l t h o u g h not i n the same manner. C l u s t e r diagrams d e r i v e d from E u c l i d e a n d i s t a n c e s between l a k e s t e n d to be d i f f e r e n t from t h o s e based on J a c c a r d ' s c o e f f i c i e n t owing t o the i n f l u e n c e o f r e l a t i v e s p e c i e s abundance, and a r e n o t o b v i o u s l y r e l a t e d t o t h o s e drawn from p h y s i o c h e m i c a l d a t a . E u c l i d e a n based dendrograms f a l l i n t o t h r e e g r o u p s . Dendrograms i n t h e f i r s t group i n c l u d e l i m n e t i c z o o p l a n k t o n ( F i g s . 1 4 c ; 1 4 d ) , l i g h t t r a p Entomostraca ( F i g s . 1 5 c ; 15d) and a l l s p e c i e s i n l i g h t t r a p s ( F i g s . 1 6 c ; 1 6 d ) . Lake 1 and/or Lake 4 i s l a s t t o j o i n t h e c l u s t e r i n t h e s e f i g u r e s , r e f l e c t i n g t h e unique s p e c i e s c o m p o s i t i o n and low d e n s i t y o f Lake 1 , and t h e e x t r a o r d i n a r i l y h i g h d e n s i t y and d i v e r s i t y o f Lake 4 . Below t h i s p o i n t , f i g u r e s g e n e r a l l y show a dichotomy between h i g h and low s a l i n i t y l a k e s . The second group i s r e p r e s e n t e d by t h e dendrogram o f l i g h t t r a p b e e t l e s p e c i e s ( F i g . 17c) and i s c l e a r l y r e l a t e d t o s a l i n i t y , a l t h o u g h not c l o s e l y r e l a t e d t o t h o s e produced u s i n g J a c c a r d ' s c o e f f i c i e n t ( F i g s . 17a; 1 7 b ) , nor t o t h o s e produced from p h y s i o c h e m i c a l d a t a ( F i g . 4 ) . The f i n a l group i n c l u d e s c l u s t e r diagrams o f sweep C o l e o p t e r a ( F i g s . 1 8 c ; 18d) and Hemiptera ( F i g s . 19d; 2 0 c ; 20d) t h a t a r e c o n f u s i n g and not r e a d i l y i n t e r p r e t a b l e i n any o b v i o u s way. C o p h e n e t i c c o r r e l a t i o n s between p h y s i o c h e m i c a l and f a u n a l dendrograms ( T a b l e 11) p r o v i d e s t a t i s t i c a l e v i d e n c e t o s u p p o r t the p a t t e r n s mentioned a b o v e . Most f a u n a l dendrograms based on J a c c a r d ' s c o e f f i c i e n t a r e c o r r e l a t e d w i t h p h y s i o c h e m i c a l o n e s , e x c e p t C o l e o p t e r a . None o f t h e f a u n a l 80 T a b l e 11 . C o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s between p h y s i o c h e m i c a l and f a u n a l dendrograms. * i n d i c a t e s s i g n i f i c a n t r e l a t i o n s h i p s . N . B . F i g s . 17d, 18b and 19c a r e o m i t t e d , see t e x t f o r e x p l a n a t i o n . Faunal Dendrogram A b i o t i c Dendrogram c h e m i c a l p h y s i o c h e m i c a l F i g . 4a F i g . 4b WATER BOTTLE ZOOPLANKTON F i g . 14a 0 . 6 6 6 F i g . 14b 0 . 6 8 7 F i g . 14c 0 . 0 3 0 F i g . 14d 0 . 1 8 5 LIGHT TRAPS Entomostraca F i g . 15a 0 . 8 7 3 * F i g . 15b 0 . 7 2 0 F i g . 15c 0 . 0 5 8 F i g . 15d 0.171 A l l s p e c i e s F i g . 16a 0 . 7 4 3 F i g . 16b 0 . 8 5 5 * F i g . 16c 0.017 F i g . 16d 0 . 0 0 3 C o l e o p t e r a F i g . 17a 0 . 3 0 1 F i g . 17b 0 . 3 5 3 F i g . 17c 0.100 Hemiptera F i g . 19a 0 . 8 0 0 * F i g . 19b 0 . 4 8 9 F i g . 19d 0 . 0 4 0 SWEEP SAMPLES C o l e o p t e r a F i g . 18a 0 . 2 5 4 F i g . 18c 0 . 3 0 0 F i g . 18d 0 . 1 2 3 Hemiptera F i g . 20a 0 . 6 4 6 F i g . 20b 0 . 2 0 5 F i g . 20c 0 . 1 0 3 F i g . 20d 0 . 1 6 3 0 . 8 2 9 * 0 . 8 4 1 * 0 . 0 3 2 0.114 0 . 9 7 2 * 0 . 8 7 9 * 0 . 1 5 5 0 . 3 2 5 0 . 8 7 3 * 0 . 8 6 7 * 0 . 0 4 6 0 . 0 5 3 0.377 0 . 4 3 4 0.134 0 . 9 2 4 * 0 . 6 3 9 0 . 1 3 3 0 . 2 9 0 0 . 3 8 8 0.207 0 . 8 1 4 * 0 . 2 9 6 0.114 0.171 81 E u c l i d e a n dendrograms are c o r r e l a t e d w i t h p h y s i o c h e m i c a l o n e s . The a b i o t i c c l u s t e r s based on both morphometric and c h e m i c a l d a t a a r e more c l o s e l y r e l a t e d t o f a u n a l dendrograms than the one based on o n l y c h e m i c a l d a t a . Discussion In t o t a l , 84 t a x a o f a q u a t i c a r t h r o p o d s were found i n t h e e i g h t B e c h e r ' s P r a i r i e l a k e s ( T a b l e 7) and s p e c i e s c h a r a c t e r i s t i c o f h i g h , moderate o r low s a l i n i t i e s , o r t o l e r a n t o f a l l s a l i n i t i e s were p r e s e n t i n t h e s e r i e s ( F i g . 5 ) . My use o f t h e s e terms does not i m p l y a n y t h i n g about the n a t u r e o f mechanisms r e s t r i c t i n g s p e c i e s t o p a r t i c u l a r w a t e r s because many mechanisms a r e p o s s i b l e , and some a r e c o n s i d e r e d i n t h e d i s c u s s i o n t o f o l l o w . Not a l l a r t h r o p o d s p e c i e s found i n the l a k e s were c e n s u s e d , o n l y t h o s e p r e d i s p o s e d t o c a p t u r e w i t h t h e t e c h n i q u e s u s e d . F o r e x a m p l e , Odonata and G e r r i d a e are common i n the a r e a ( S c u d d e r , 1971; Cannings e t a l . , 1980; Spence & S c u d d e r , 1980; Cannings & C a n n i n g s , 1 9 8 5 ) , b u t i n my sample s e t s they were i n f r e q u e n t o r a b s e n t . For t h e most p a r t , o b s e r v e d s p e c i e s d i s t r i b u t i o n s c o n c u r r e d w i t h t h o s e found p r e v i o u s l y i n the same l a k e s ( S c u d d e r , 1969a; Cannings & S c u d d e r , 1978; R e y n o l d s , 1979; Cannings e t j a K , 1980; Cannings & C a n n i n g s , 1 9 8 5 ) . Some e x c e p t i o n s i n c l u d e Enochrus  d i f f u s u s , Rhantus f r o n t a l i s and Aedes f i t c h i t h a t Scudder (1969a) r e p o r t s i n a l m o s t a l l t h e s e study l a k e s whereas my d a t a showed more l i m i t e d d i s t r i b u t i o n s . These d i s c r e p a n c i e s a r e owing p r i m a r i l y t o the s a m p l i n g program i n t h i s study which was not e x h a u s t i v e . F u r t h e r m o r e , d i s t r i b u t i o n s p r o v i d e d by Scudder (1969a) a r e based on d a t a o b t a i n e d o v e r a t e n y e a r p e r i o d , and t h e s e p a t t e r n s a r e n o t c o n s t a n t . Each study l a k e i n the s e r i e s s u p p o r t e d a d i s t i n c t l y d i f f e r e n t f a u n a l 82 a s s e m b l a g e , d e s p i t e the f a c t t h a t a l l s p e c i e s a r e c a p a b l e o f d i s p e r s i n g t o a l l l a k e s ( S c u d d e r , 1 9 6 9 b ) . These d i s t r i b u t i o n p a t t e r n s were c l o s e l y r e l a t e d t o s a l i n i t y ( F i g s . 6 - 1 2 ) . A marked d i f f e r e n c e i n s p e c i e s c o m p o s i t i o n among l a k e s i n a s a l i n e l a k e s e r i e s has been seen i n o t h e r s u r v e y s ( B e a d l e , 1943; Rawson & Moore, 1944; B a y l y & W i l l i a m s , 1966; S c u d d e r , 1969a; Timms, 1981; and o t h e r s ) . C l u s t e r a n a l y s e s i n t h i s study a r r a n g e d l a k e s i n h i e r a r c h i c a l dendrograms based on t h e p r e s e n c e o r absence o f animal s p e c i e s and e c o l o g i c a l c a t e g o r i e s ( p a r t s a & b o f F i g s . 1 4 - 2 0 ) . T y p i c a l l y , t h e s e dendrograms show one major dichotomy between l a k e s w i t h c o n d u c t i v i t i e s above and below 5000 u S . T h i s p a t t e r n i s v e r y s i m i l a r t o arrangments o f l a k e s based on t h e i r p h y s i o c h e m i c a l p r o p e r t i e s ( F i g . 4 ) , and i n most c a s e s , s t a t i s t i c a l l y s i g n i f i c a n t c o r r e l a t i o n s e x i s t between l a k e dendrograms based on f a u n a l c o m p o s i t i o n and on p h y s i o c h e m i c a l p r o p e r t i e s ( T a b l e 1 1 ) . The one n o t a b l e e x c e p t i o n t o t h i s p a t t e r n i s seen among c o l e o p t e r a n s where the arrangement o f communities among l a k e s i s c l e a r l y r e l a t e d t o s a l i n i t y ( F i g s . 17a; 1 7 b ) , b u t not s t a t i s t i c a l l y c o r r e l a t e d w i t h the p h y s i o c h e m i c a l c l u s t e r s ( T a b l e 1 1 ) . T h i s d i s p a r i t y i n d i c a t e s t h a t i n o r d e r t o d i s c e r n p a t t e r n s produced by m u l t i v a r i a t e c l a s s i f i c a t i o n , c l u s t e r diagrams s h o u l d be v i s u a l l y examined as w e l l as s t a t i s t i c a l l y compared w i t h p r e d i c t e d o r t h e o r e t i c a l dendrograms. Those f a u n a l dendrograms ( z o o p l a n k t o n , H e m i p t e r a , a l l s p e c i e s ) t h a t a r e c o r r e l a t e d w i t h p h y s i o c h e m i c a l o n e s , show s l i g h t l y s t r o n g e r c o r r e l a t i o n s w i t h dendrograms based on c h e m i c a l p l u s morphometric f e a t u r e s , than t h o s e based o n l y on w a t e r c h e m i s t r y . T h i s s u g g e s t s t h a t most o f the v a r i a t i o n i n t h e s e f a u n a l communities among l a k e s was r e l a t e d t o w a t e r c h e m i s t r y , and morphometric c h a r a c t e r i s t i c s a r e l e s s i m p o r t a n t . In c o m p a r i s o n s between p h y s i o c h e m i c a l v a r i a b l e s and community 83 p a r a m e t e r s , w a t e r c h e m i s t r y appeared t o be the most i m p o r t a n t a b i o t i c v a r i a b l e i n f l u e n c i n g b i o t i c communities and l i t t l e e v i d e n c e was found o f morphometric c o r r e l a t i o n s . Mean d e p t h , a measure o f l a k e s i z e , was i n c l u d e d t o t e s t the s p e c i e s / a r e a h y p o t h e s i s e x p l a i n e d i n C h a p t e r 1 . I s l a n d biogeography (MacArthur & W i l s o n , 1967) p r e d i c t s p o s i t i v e r e l a t i o n s h i p s between community parameters and l a k e s i z e , t h e r e f o r e , t h e o b s e r v e d n e g a t i v e a s s o c i a t i o n s ( T a b l e 10) a r e owing t o the c o i n c i d e n t a l c o r r e l a t i o n o f mean depth w i t h s a l i n i t y i n t h e study l a k e s ( C h a p t e r 1 ) . I t i s not c l e a r i f o b s e r v e d p o s i t i v e t r e n d s between t h e p o t e n t i a l e f f e c t s o f l i t t o r a l p r o c e s s e s on t h e whole l a k e (D|_/\) and community parameters ( T a b l e 10) a r e secondary a s s o c i a t i o n s , p r i m a r i l y a t t r i b u t a b l e t o t h e chance a s s o c i a t i o n o f D[_/\ w i t h s a l i n i t y i n t h e study l a k e s ( C h a p t e r 1 ) , o r i f l i t t o r a l p r o c e s s e s do a c t u a l l y p l a y a s i g n i f i c a n t r o l e i n community s t r u c t u r e . Of the t h r e e ways of measuring s a l i n i t y (mean c o n d u c t i v i t y , l o g mean c o n d u c t i v i t y , f i r s t p r i n c i p a l components s c o r e s ) compared w i t h community p a r a m e t e r s , no one c o n s i s t e n t l y showed s t r o n g e r o r more f r e q u e n t c o r r e l a t i o n s w i t h community parameters ( T a b l e 1 0 ) . T h i s m e r e l y i n d i c a t e s t h a t the m a t h e m a t i c a l n a t u r e o f r e l a t i o n s h i p s between community parameters and s a l i n i t y a r e not the same f o r a l l f a u n a l groups o r t y p e s o f p a r a m e t e r s . A l l t h r e e m e a s u r e s , however, were n e c e s s a r y t o r e v e a l a l l the a s s o c i a t i o n s between b i o t a and a b i o t a . To a n a l y z e community s t r u c t u r e , t h i s study used two schemes o f c l a s s i f i c a t i o n (taxonomic and e c o l o g i c a l ) , m u l t i v a r i a t e c l a s s i f i c a t i o n t e c h n i q u e s , and 13 n u m e r i c a l p a r a m e t e r s . No one method was s u f f i c i e n t t o summarize the r e l a t i o n s h i p between community s t r u c t u r e and e n v i r o n m e n t a l s e v e r i t y . R a t h e r , a l l c o n t r i b u t e d some i n f o r m a t i o n t o c h a r a c t e r i z a t i o n s and h y p o t h e s e s , and none were u s e l e s s . The n a t u r e o f t h e r e l a t i o n s h i p 84 between s a l i n i t y and community s t r u c t u r e i s v e r y complex and each d a t a s e t must be examined s e p a r a t e l y . Data from the 7 sample s e t s examined i n t h i s s t u d y s u p p o r t the h y p o t h e s i s t h a t s a l i n e h a b i t a t s have l e s s d i v e r s e communities than f r e s h w a t e r o n e s , when d i v e r s i t y i s d e f i n e d as the a b s o l u t e o r r e l a t i v e number o f s p e c i e s o r e c o l o g i c a l c a t e g o r i e s i n a l a k e . These a s s o c i a t i o n s demonstrate t h a t an i n c r e a s e i n s a l i n i t y i s accompanied by a d e c r e a s e i n the number o f s p e c i e s o r c a t e g o r i e s c a p a b l e o f s u r v i v i n g i n such c o n d i t i o n s , and i n the number o f s p e c i e s o r c a t e g o r i e s a b l e t o c o l o n i z e a l a k e r e l a t i v e t o the t o t a l number a v a i l a b l e f o r c o l o n i z a t i o n . Most s u r v e y s of s a l i n e l a k e s e r i e s ( B e a d l e , 1943; Rawson & M o o r e , 1944; Moore, 1952; B a y l y & W i l l i a m s , 1966; S c u d d e r , 1969a; Hammer e t j f k , 1975; W i l l i a m s , 1978; R e y n o l d s , 1979; W i e r d e r h o l m , 1980; Geddes e t a l _ . , 1981) have s u g g e s t e d t h i s i n v e r s e r e l a t i o n s h i p between s p e c i e s r i c h n e s s and s a l i n i t y , but few have performed r i g o r o u s s t a t i s t i c a l t e s t s o r attempted t o q u a n t i f y community s t r u c t u r e beyond s i m p l e s p e c i e s c o u n t s . In a study o f t h r e e A u s t r a l i a n l a k e s , Timms (1981) found an i n v e r s e a s s o c i a t i o n between s a l i n i t y and s p e c i e s r i c h n e s s , b u t q u e s t i o n e d t h e u s e f u l n e s s o f d i v e r s i t y i n d i c i e s as he found t h a t they d i d not always r e f l e c t a d e c r e a s e i n d i v e r s i t y w i t h i n c r e a s i n g s a l i n i t y . My r e s u l t s a l s o i n d i c a t e d t h a t d i v e r s i t y i n d i c i e s d i d not always d e c r e a s e w i t h i n c r e a s i n g s a l i n i t y , however, I do not a t t r i b u t e t h i s s o l e l y t o the i n a d e q u a c i e s o f d i v e r s i t y i n d i c e s . I n s t e a d , when measures o f community s t r u c t u r e i n v o l v e t h e r e l a t i v e abundance o f s p e c i e s , p a r t i c u l a r groups o f a n i m a l s must be examined s e p a r a t e l y as the s t r u c t u r e o f t h e s e subcommunities i s a f f e c t e d d i f f e r e n t l y by s a l i n i t y . In the d i s c u s s i o n t o f o l l o w , community c o m p o s i t i o n and s t r u c t u r e o f 85 the t h r e e taxonomic groups ( z o o p l a n k t o n , C o l e o p t e r a , Hemiptera) a r e c o n s i d e r e d s e p a r a t e l y , and then drawn t o g e t h e r i n a c o n s i d e r a t i o n o f t h e e n t i r e f a u n a l community. ZOOPLANKTON COMMUNITIES Of t h e t h r e e s a m p l i n g t e c h n i q u e s employed t o c o l l e c t a n i m a l s i n t h i s study (van Dorn b o t t l e s , sweep n e t s , submerged l i g h t t r a p s ) , a l l c o l l e c t e d z o o p l a n k t o n , b u t van Dorn b o t t l e s b e s t r e p r e s e n t a f u n c t i o n a l z o o p l a n k t o n community. L i t t o r a l sweep n e t s were n o t s u i t a b l e as i t was i m p r a c t i c a l t o enumerate t h e enormous number o f s m a l l c r u s t a c e a n s g a t h e r e d . L i g h t t r a p c o l l e c t i o n s were n u m e r i c a l l y f e a s i b l e t o work w i t h , b u t they do not n e c e s s a r i l y r e p r e s e n t f u n c t i o n a l e c o l o g i c a l communities so r e s u l t s must be i n t e r p r e t t e d w i t h c a u t i o n . A c t i v e l y swimming a n i m a l s w i t h p o s i t i v e p h o t o t a x i c r e s p o n s e s a r e s e l e c t i v e l y sampled i n l i g h t t r a p s , so o b s e r v e d r e l a t i v e abundances may not be r e a l i s t i c . The number o f a n i m a l s c o l l e c t e d i n the l i m n e t i c zone w i t h van Dorn b o t t l e s was s u i t a b l e f o r e n u m e r a t i o n , and more r e p r e s e n t a t i v e o f t h e t r u e d e n s i t i e s and r e l a t i v e abundances o f a n i m a l s i n t h e community. Even though a q u a t i c e n v i r o n m e n t s are h i g h l y v a r i a b l e i n time and s p a c e , and sample r e p l i c a t e s were p r o b a b l y not numerous enough t o show s e a s o n a l p o p u l a t i o n c h a n g e s , t h e s e samples were adequate t o measure z o o p l a n k t o n community s t r u c t u r e i n each l a k e over the e n t i r e s e a s o n . C l a d o c e r a , Copepoda and R o t i f e r a are commonly c o n s i d e r e d t h e dominant components o f f r e s h w a t e r z o o p l a n k t o n ( W e t z e l , 1 9 7 5 ) , y e t i n a n a l y z i n g the l i m n e t i c z o o p l a n k t o n I i n c l u d e d the d i p t e r a n l a r v a e Chaoborus a m e r i c a n u s , the o n l y s p e c i e s o f phantom midge f o u n d , and c h i r o n o m i d s . These l a r v a e o f t e n o c c u r r e d i n the l i m n e t i c zone i n h i g h d e n s i t i e s so I deem them 86 i m p o r t a n t members o f the f u n c t i o n i n g community. In g e n e r a l , h i g h l y predaceous Chaoborus l a r v a e e x h i b i t d i u r n a l m i g r a t i o n p a t t e r n s ; r e m a i n i n g a t l a k e bottom d u r i n g the day and a s c e n d i n g t o t h e s u r f a c e t o prey on z o o p l a n k t e r s a t n i g h t ( N o r t h c o t e , 1964; LaRow, 1968; G o l d s p i n k & S c o t t , 1971) , b u t t h i s p a t t e r n does n o t always h o l d t r u e . Fedorenko & S w i f t (1972) r e p o r t e d the o c c u r r e n c e o f a l l f o u r i n s t a r s o f C. americanus a t o r near the s u r f a c e a l l d a y , i . e . above 5 m. A l t h o u g h c h i r o n o m i d s a r e n o r m a l l y c o n s i d e r e d members o f t h e b e n t h o s , i t i s r e a s o n a b l e t o i n c l u d e them i n t h e z o o p l a n k t o n community as t h e i r r e g u l a r appearance and a c t i v i t i y i n the l i m n e t i c zone has been r e p o r t e d ( M u n d i e , 1959; D a v i e s , 1974; 1 9 7 6 ) . D i p t e r a n s were not i n c l u d e d w i t h l i g h t t r a p Entomotraca as l i g h t t r a p c o l l e c t i o n s do not n e c e s s a r i l y r e p r e s e n t a f u n c t i o n a l community, and i t i s i m p o s s i b l e t o d e t e r m i n e w h i c h , o r how many, d i p t e r a n s c o l l e c t e d i n t r a p s a c t u a l l y i n t e r a c t e d w i t h c r u s t a c e a n s . In a d d i t i o n , because the study l a k e s a r e r e l a t i v e l y s m a l l and s h a l l o w , c l a d o c e r a n s p e c i e s such as A l o n a and C h y d o r u s , u s u a l l y d e s i g n a t e d i n h a b i t a n t o f the l i t t o r a l zone ( C h e n g a l a t h , 1 9 8 2 ) , c o u l d not be o m i t t e d from a n a l y s i s o f l i m n e t i c c o m m u n i t i e s . Z o o p l a n k t o n community c o m p o s i t i o n d i f f e r e d markedly among l a k e s ( F i g s 6 ; 7 ) . Lake 1 showed a f r e s h w a t e r s p e c i e s assemblage dominated by Daphnia  r o s e a and D. c a t a w b a . M o d e r a t e l y s a l i n e l a k e s 2-5 a l l had a s i m i l a r c o m p o s i t i o n dominated by D. p u l e x / s c h ^ d l e r i . A p e c u l i a r c o - o c c u r r e n c e o f a l a r g e c l a d o c e r a n , Daphnia s i m i l i s , w i t h a l a r g e and s m a l l d i a p t o m i d , Diaptomus n e v a d e n s i s and D. s i c i l i s , o c c u r r e d i n l a k e s w i t h c o n d u c t i v i t i e s o v e r 5000 uS and i s c h a r a c t e r i s t i c o f extreme c o n d i t i o n s around the w o r l d ( H u t c h i n s o n , 1937; Moore, 1952; A n d e r s o n , 1970; R e y n o l d s , 1 9 7 9 ) . To d a t e , no one has examined t h i s phenomenon o r s p e c u l a t e d on i t s e x i s t e n c e . Moina h u t c h i n s o n i was found o n l y i n t h e most s a l i n e l a k e , i n a c c o r d a n c e w i t h 87 f i n d i n g s o f o t h e r s ( H u t c h i n s o n , 1937; Moore, 1952; R e y n o l d s , 1 9 7 9 ) . V i r t u a l l y no e x p e r i m e n t a l e v i d e n c e i s a v a i l a b l e on t h e s a l i n i t y t o l e r a n c e s o f s p e c i e s found i n the study l a k e s , a l t h o u g h s p e c i e s c o u l d be l i m i t e d by s i m p l e o s m o r e g u l a t o r y s t r e s s as shown by Brand (1981) f o r C a l a m o e c i a  c l i t e l l a t a , a p l a n k t o n i c copepod endemic t o A u s t r a l i a n a t h a l a s s i c s a l i n e w a t e r s . When measures o f d i v e r s i t y i n c l u d e the r e l a t i v e abundance o f s p e c i e s o r e c o l o g i c a l c a t e g o r i e s , t h e r e i s v i r t u a l l y no e v i d e n c e t h a t t h e d i v e r s i t y o f z o o p l a n k t o n s p e c i e s o r c a t e g o r i e s d e c r e a s e d w i t h i n c r e a s i n g s a l i n i t y . F o r t h e most p a r t , d i v e r s i t y parameters f o r l i m n e t i c and l i g h t t r a p samples are p o s i t i v e l y c o r r e l a t e d w i t h each o t h e r ( T a b l e 9 ) , i n d i c a t i n g t h a t both s a m p l i n g t e c h n i q u e s p r o v i d e a good r e p r e s e n t a t i o n o f the z o o p l a n k t o n community. One f a c t o r d i s r u p t i n g t h e p r e d i c t e d a s s o c i a t i o n between s a l i n i t y and d i v e r s i t y was the e x t r e m e l y h i g h d e n s i t y and d i v e r s i t y o f z o o p l a n k t o n i n the m o d e r a t e l y s a l i n e Lake 4 . I t i s not s i m p l y the case t h a t t h i s h i g h d i v e r s i t y i s a f u n c t i o n o f the number o f i n d i v i d u a l s sampled because Lake 1 had low d e n s i t i e s and r e l a t i v e l y h i g h d i v e r s i t y . Dendrograms c l u s t e r i n g l a k e s on t h e b a s i s o f the r e l a t i v e abundance o f z o o p l a n k t o n s p e c i e s o r c a t e g o r i e s a l l show t h i s odd l a k e as t h e l a s t o r p e n u l t i m a t e one t o j o i n the c l u s t e r ( F i g s . 14; 1 5 ) . Other than t h i s one a b e r r a t i o n , the arrangement o f l a k e s i n the dendrograms i s r e l a t e d t o s a l i n i t y . Why Lake 4 was so unusual i s a m y s t e r y . A h i g h l y s i g n i f i c a n t i n v e r s e a s s o c i a t i o n e x i s t s between s a l i n i t y and t h e t r o p h i c l e v e l d i v e r s i t y o f l i m n e t i c z o o p l a n k t o n ( T a b l e 1 0 ) . The c o n t r a d i c t o r y p o s i t i v e a s s o c i a t i o n i n d i c a t e d by l i g h t t r a p samples i s a d i s t o r t i o n owing t o the d i f f e r e n t i a l s a m p l i n g o f p r e d a t o r s by the two t e c h n i q u e s . P r e d a t o r y d i a p t o m i d copepods i n h a b i t i n g s a l i n e l a k e s were 88 c o l l e c t e d i n l a r g e numbers by l i g h t t r a p s , b u t were much l e s s numerous i n l i m n e t i c b o t t l e s a m p l e s . Most l i k e l y , t h i s p r e d a t o r was a t t r a c t e d t o l i g h t o r to the abundant prey a t t r a c t e d t o l i g h t , and hence appeared i n much h i g h e r d e n s i t i e s than n o r m a l . T h e r e f o r e , the p o s i t i v e a s s o c i a t i o n between t r o p h i c l e v e l d i v e r s i t y and s a l i n i t y i n d i c a t e d by l i g h t t r a p samples i s p r o b a b l y an a r t e f a c t , and the n e g a t i v e r e l a t i o n s h i p s u g g e s t e d by w a t e r b o t t l e samples r e p r e s e n t s the r e a l s i t u a t i o n . T h i s i n v e r s e a s s o c i a t i o n s u g g e s t s t h a t s a l i n i t y may be i m p o r t a n t i n s t r u c t u r i n g z o o p l a n k t o n communities t h r o u g h i t s e f f e c t s on f o o d q u a n t i t y o r q u a l i t y , r a t h e r than s i m p l e p h y s i o l o g i c a l c o n s t r a i n t s . S h i f t s i n s p e c i e s c o m p o s i t i o n and e c o l o g i c a l c a t e g o r i e s o f z o o p l a n k t o n from s a l i n e t o f r e s h w a t e r s a r e a n a l o g o u s t o changes seen w i t h e u t r o p h i c a t i o n . T a x o n o m i c a l l y , c l a d o c e r a n s were abundant i n a l l study l a k e s , c a l a n o i d copepods were abundant o n l y i n s a l i n e l a k e s , and c y c l o p o i d s were found o n l y i n f r e s h t o moderate s a l i n i t i e s . S i m i l a r l y , o l i g o t r o p h i c systems a r e t y p i f i e d by p o p u l a t i o n s o f c a l a n o i d c o p e p o d s , whereas c l a d o c e r a n s and c y c l o p o i d copepods a r e r e l a t i v e l y more abundant i n e u t r o p h i c c o n d i t i o n s ( P a t a l a s , 1972; McNaught, 1975; A l l a n , 1976; G l i w i c z , 1977; Gannon & S t e m b e r g e r , 1978; F r y & O s b o r n e , 1980; B l a n c h e r , 1984; R i c h a r d et , 1 9 8 5 ) . P r e v a l e n t e x p l a n a t i o n s f o r t h i s change a r e t h a t the type and c o n c e n t r a t i o n o f f o o d i n e u t r o p h i c c o n d i t i o n s may be adequate f o r s m a l l c l a d o c e r a n s , b u t n o t f o r l a r g e C l a d o c e r a o r copepods which a r e b e t t e r adapted f o r o l i g o t r o p h i c c o n d i t i o n s . F u r t h e r m o r e , Gannon & Stemberger (1978) r e p o r t t h a t z o o p l a n k t e r s p r i m a r i l y c o n s i d e r e d l i t t o r a l s p e c i e s o f t e n become more abundant i n t h e l i m n e t i c zone o f e u t r o p h i c w a t e r s . T h i s p a t t e r n was a l s o o b s e r v e d i n t h e l i m n e t i c zone o f t h e more f r e s h w a t e r l a k e s . A l t h o u g h our u n d e r s t a n d i n g o f t h i s phenomenon i s l i m i t e d , here i t 89 may s i m p l y be because f r e s h w a t e r l a k e s happen t o be r e l a t i v e l y s m a l l and s h a l l o w . E c o l o g i c a l l y , s a l i n e l a k e s were t y p i c a l l y p o p u l a t e d by l a r g e h e r b i v o r e s and c a r n i v o r e s , whereas f r e s h w a t e r l a k e s had p r o p o r t i o n a t e l y more s m a l l h e r b i v o r e s and p r e d a t o r s . Both Gannon & Stemberger (1978) and R i c h a r d e t al_. (1985) r e p o r t t h a t under c o n d i t i o n s o f n u t r i e n t e n r i c h m e n t , t h e average s i z e o f z o o p l a n k t e r s o f t e n d e c r e a s e s as s m a l l e r s p e c i e s w i t h s i m p l e r l i f e h i s t o r i e s and more r a p i d r a t e s o f r e p r o d u c t i o n a p p e a r . S p r u l e s & H o l t b y (1979) found t h a t t h e most i m p o r t a n t v a r i a t i o n i n the e c o l o g i c a l s t r u c t u r e o f l i m n e t i c z o o p l a n k t o n , i n a s e r i e s o f O n t a r i o l a k e s , was from a predominance o f s m a l l h e r b i v o r e s t o l a r g e h e r b i v o r e s and c a r n i v o r e s . F u r t h e r m o r e , they c o r r e l a t e d t h i s p a t t e r n w i t h morphometric i n d i c a t o r s o f l a k e p r o d u c t i v i t y . The s u c c e s s o f c a l a n o i d s o r c l a d o c e r a n s , and l a r g e o r s m a l l h e r b i v o r e s and p r e d a t o r s , i n an environment u l t i m a t e l y depends on t h e . a b u n d a n c e and s e a s o n a l i t y o f the f o o d s u p p l y and the a b i l i t y o f s p e c i e s t o s u r v i v e such c o n d i t i o n s . T o p p i n g (1975) s u g g e s t s t h a t p r i m a r y p r o d u c t i v i t y d e c r e a s e s w i t h i n c r e a s i n g s a l i n i t y i n t h e s e C h i l c o t i n l a k e s , t h e r e b y i n d i c a t i n g reduced f o o d s u p p l y i n s a l i n e l a k e s t h a t may a c c o u n t f o r t h e o b s e r v e d z o o p l a n k t o n d i s t r i b u t i o n p a t t e r n . A l t h o u g h z o o p l a n k t o n employ a v a r i e t y o f f e e d i n g mechanisms and e a t many t y p e s o f f o o d , p h y t o p l a n k t o n p r o d u c t i v i t y can be used as an i n d i c a t o r o f f o o d s u p p l y ( P a t a l a s , 1 9 7 2 ) . The m a j o r i t y o f l i m n e t i c z o o p l a n k t e r s a r e h e r b i v o r e s f e e d i n g on suspended f i n e p a r t i c u l a t e o r g a n i c m a t t e r and t h e s e f i l t e r f e e d e r s , i n t u r n , a r e p r e y e d upon by p r e d a t o r y s p e c i e s . Some z o o p l a n k t o n l i f e h i s t o r y c h a r a c t e r i s t i c s i n v o l v e d i n p r o d u c i n g t h e o b s e r v e d d i s t r i b u t i o n p a t t e r n s i n c l u d e f e e d i n g a b i l i t y and c o m p e t i t i o n , p l u s p r e d a t o r escape p o t e n t i a l (McNaught, 1975; A l l a n , 1976; Gannon & 90 S t e m b e r g e r , 1978; B l a n c h e r , 1984; R i c h a r d e t a K , 1 9 8 5 ) . A p o s s i b l e e x p l a n a t i o n f o r t h e phenomenon o b s e r v e d i n t h e study l a k e s i s as f o l l o w s . C a l a n o i d copepods predominate i n s a l i n e o r o l i g o t r o p h i c l a k e s because o f t h e i r s u p e r i o r f i l t e r i n g c a p a c i t y and h i g h i n g e s t i o n r a t e a t low c e l l d e n s i t i e s , and h i g h i n g e s t i o n e f f i c i e n c y a t s m a l l c e l l s i z e , whereas c l a d o c e r a n s a r e more e f f i c i e n t i n f r e s h w a t e r o r e u t r o p h i c c o n d i t i o n s because o f t h e i r f e e d i n g e f f i c i e n c y on s m a l l and l a r g e c e l l s a l i k e (McNaught, 1 9 7 5 ) . Small h e r b i v o r e s a r e r e s t r i c t e d t o f r e s h e r w a t e r s by t h e i r f e e d i n g r e q u i r e m e n t s (Gannon & S t e m b e r g e r , 1 9 7 8 ) , and s m a l l p r e d a t o r s a r e r e s t r i c t e d t o t h e same l a k e s as t h i s i s where t h e i r p o t e n t i a l prey a r e . Large f i l t r a t o r s do w e l l i n a l l l a k e s as t h e r e a r e no v e r t e b r a t e p r e d a t o r s and s i z e makes them l e s s v u l n e r a b l e t o i n v e r t e b r a t e p r e d a t o r s ( Z a r e t , 1 9 8 0 ) . L a r g e h e r b i v o r e s , however, t e n d t o be b i g g e r and more abundant i n s a l i n e o r o l i g o t r o p h i c l a k e s as they a r e b e t t e r adapted t o f o o d c o n d i t i o n s t h e r e i . e . c o l o n i a l and f i l a m e n t o u s b l u e - g r e e n a l g a e they a r e known t o a v o i d are l e s s abundant ( W e t z e l , 1 9 7 5 ) , and a r e not s u b j e c t t o c o m p e t i t i o n from s m a l l e r f o r m s . In summary, changes i n t h e taxonomic and e c o l o g i c a l c o m p o s i t i o n o f z o o p l a n k t o n c o m m u n i t i e s w i t h d e c r e a s i n g s a l i n i t y i n t h i s s e r i e s o f l a k e s are a n a l o g o u s t o t h o s e r e p o r t e d w i t h i n c r e a s i n g e u t r o p h y . T h i s s u g g e s t s t h a t t h e mechanisms s h a p i n g z o o p l a n k t o n community s t r u c t u r e a r e p r i m a r i l y r e l a t e d t o f o o d s u p p l y and s p e c i e s ' n u t r i t i o n a l r e q u i r e m e n t s and s e c o n d a r i l y t o o s m o r e g u l a t o r y s t r e s s , a l t h o u g h s a l i n i t y may u l t i m a t e l y a f f e c t t h e t r o p h i c s t a t u s o f l a k e s . Because most o f t h e e v i d e n c e t o s u p p o r t t h i s h y p o t h e s i s i s c i r c u m s t a n t i a l , f u r t h e r i n v e s t i g a t i o n s o f s a l i n i t y t o l e r a n c e s and food r e q u i r e m e n t s o f i n h a b i t i n g z o o p l a n k t e r s , and the e f f e c t s o f s a l i n i t y on f o o d a v a i l a b i l i t y a r e now n e c e s s a r y . 91 COLEOPTERAN COMMUNITIES A t o t a l o f 28 a q u a t i c C o l e o p t e r a s p e c i e s were found i n the s e r i e s o f e i g h t study l a k e s . A n a l y s i s o f community s t r u c t u r e was l i m i t e d to a d u l t forms as t h e r e i s no good key f o r l a r v a l f o r m s . W i t h o u t a good key t o the l a r v a e o r an i n - d e p t h study o f t h e b e e t l e s , i t i s i m p o s s i b l e t o be s u r e i f d i s t r i b u t i o n r e c o r d s f o r a d u l t s i n d i c a t e t h a t s p e c i e s were b r e e d i n g i n the v a r i o u s l a k e s o r were s i m p l y temporary i n h a b i t a n t s s i n c e many C o l e o p t e r a are known t o be s t r o n g f l i e r s . L a r s o n ' s (1985) work on predaceous d i v i n g b e e t l e communities i n d i c a t e s t h a t a l l d y t i s c i d s e n c o u n t e r e d i n t h i s study are t y p i c a l i n h a b i t a n t s o f g r a s s l a n d and p a r k l a n d p o n d s . T h e r e f o r e , even though t h e r e i s no e v i d e n c e o f b r e e d i n g , i t i s l i k e l y t h a t a l l t h e s e s p e c i e s a r e i n d i g e n o u s t o the aspen p a r k l a n d ponds found on B e c h e r ' s P r a i r i e . In t h i s s t u d y , a q u a t i c C o l e o p t e r a were c o l l e c t e d w i t h both submerged l i g h t t r a p s and sweep n e t s . L i g h t t r a p s a t t r a c t e d l a r g e numbers o f the f r e e swimming, predaceous D y t i s c i d a e , t h a t e x h i b i t p o s i t i v e p h o t o t a x i c r e s p o n s e s . They d i d n o t , however, w e l l r e p r e s e n t the h e r b i v o r o u s h a l i p l i d s nor c a t c h any h e r b i v o r o u s h y d r o p h i l i d s and c u r c u l i o n i d s as were found i n sweep s a m p l e s , as t h e s e s p e c i e s t e n d t o be poor swimmers and remain c l o s e l y a s s o c i a t e d w i t h the macrophytes they f e e d upon. Sweep n e t samples i n c l u d e d a l l b u t one o f t h e s p e c i e s c o l l e c t e d i n l i g h t t r a p s . They caught r e l a t i v e l y more h e r b i v o r e s than l i g h t t r a p s and c o l l e c t e d t e n a d d i t i o n a l s p e c i e s i n c l u d i n g s e v e r a l r a r e predaceous d y t i s c i d s (Graphoderus s p p . ) , h e r b i v o r o u s c u r c u l i o n i d s ( L i t o d a c t y l u s g r i s e o m i c a n s , L i x e l l u s f i l i f o r m i s ) and h y d r o p h i l i d s (Enochrus d i f f u s u s , L a c c o b i u s s p p . ) . A l t h o u g h sweep n e t s c o l l e c t e d more b e e t l e s p e c i e s than l i g h t t r a p s , any g e n e r a l i z a t i o n s drawn about the community from t h e d a t a s e t a r e 92 q u e s t i o n a b l e because t o t a l d e n s i t i e s and r e l a t i v e abundances were ver y v a r i a b l e . A i k e n & W i l k i n s o n (1985) a l s o found sweep n e t t i n g u n s a t i s f a c t o r y f o r c o l l e c t i n g q u a n t i t a t i v e samples o f a q u a t i c C o l e o p t e r a . The h i g h l y v a r i a b l e n a t u r e o f sweep n e t samples i s r e f l e c t e d by dendrograms and community p a r a m e t e r s : no p a t t e r n i s a p p a r e n t i n c l u s t e r diagrams o f l a k e s based on b e e t l e s c a u g h t i n sweep n e t s ( F i g . 1 8 ) , no community parameters are c o r r e l a t e d w i t h parameters c a l c u l a t e d from l i g h t t r a p s a m p l e s , and v i r t u a l l y none o f t h e community parameters shows an a s s o c i a t i o n o r t r e n d w i t h a b i o t i c v a r i a b l e s ( T a b l e 1 0 ) . The o n l y e x c e p t i o n i s where the c o m p l e x i t y o f b e e t l e communities r e l a t i v e t o the t h e o r e t i c a l maximum i s n e g a t i v e l y a s s o c i a t e d w i t h t h e p o t e n t i a l f o r l i t t o r a l p r o c e s s e s t o a f f e c t t h e whole l a k e . T h i s may i n d i c a t e t h e i m p o r t a n c e o f l i t t o r a l p r o c e s s e s i n s t r u c t u r i n g C o l e o p t e r a c o m m u n i t i e s , o r i t may be an a r t e f a c t o f s a m p l i n g t e c h n i q u e . Sweep n e t s a r e o b v i o u s l y a u s e f u l s a m p l i n g d e v i c e as they appeared t o c o l l e c t a l l , o r m o s t , o f the s p e c i e s i n h a b i t i n g a l a k e , but a much more e x t e n s i v e s a m p l i n g program would be r e q u i r e d t o p r o v i d e r e l i a b l e n u m e r i c a l d a t a . C o n s e q u e n t l y , much o f the f o l l o w i n g d i s c u s s i o n i s based on t h e n u m e r i c a l l y more r e a l i s t i c d a t a p r o v i d e d by submerged l i g h t t r a p s . The c o m p o s i t i o n o f a q u a t i c c o l e o p t e r a n communities i n the study l a k e s i s c l e a r l y r e l a t e d t o s a l i n i t y . The e i g h t l a k e s f a l l i n t o t h r e e groups based on t h e r e l a t i v e abundance o f s p e c i e s i n each community, as shown by r e l a t i v e abundance c h a r t s and c l u s t e r diagrams ( F i g s . 4 a ; 1 7 c ) . The most f r e s h w a t e r Lake 1 was unique i n the s e r i e s . I t had the most s p e c i e s ; i t s dominant s p e c i e s , H a l i p l u s i m m a c u l i c o l l i s , was found i n a l l l a k e s b u t i s abundant o n l y i n t h i s one; and s e v e r a l c o - d o m i n a n t s p e c i e s , namely H.  l e e c h i and Hydroporus g r i s e o s t r i a t u s , were unique t o t h i s l a k e . The second group i s composed o f t h e f r e s h t o m o d e r a t e l y s a l i n e Lakes 2 - 5 t h a t were 93 c h a r a c t e r i z e d by l a r g e p o p u l a t i o n s o f H a l i p i us s t a g n i n u s and Rhantus  f r o n t a l i s . High s a l i n i t y Lakes 6 - 8 , w i t h c o n d u c t i v i t e s o v e r 5000 u S , had few s p e c i e s and were dominated by Hygrotus m a s c u l i n u s . L i t t l e i n f o r m a t i o n i s a v a i l a b l e on t h e s a l i n i t y t o l e r a n c e ranges o f a q u a t i c b e e t l e s , a l t h o u g h H. m a s c u l i n u s i s known to be a t y p i c a l i n h a b i t a n t o f s a l i n e ponds ( H a t c h , 1953; S c u d d e r , 1969a; A n d e r s o n , 1983; L a r s o n , 1 9 8 5 ) . The s u c c e s s i o n a l sequence o f Hygrotus s p e c i e s seen w i t h i n c r e a s i n g s a l i n i t y i n t h e s e l a k e s , H. l u t e s c e n s , H. u n g u i c u l a r i s , H. s a y i , H. i m p r e s s o p u n c t a t u s , H.  m a s c u l i n u s , i s i n a c c o r d a n c e w i t h t h e p a t t e r n found by L a r s o n (1985) i n A l b e r t a p o n d s , a l t h o u g h H. l u t e s c e n s i s not known t o o c c u r i n A l b e r t a ( A n d e r s o n , 1 9 8 3 ) . C l e a r l y , more documentation on t h e s a l i n i t y t o l e r a n c e s o f C o l e o p t e r a i s r e q u i r e d . Three groups o f l a k e s , e q u i v a l e n t t o t h o s e mentioned a b o v e , a r e seen i n a n a l y s i s o f t h e r e l a t i v e abundance o f e c o l o g i c a l c a t e g o r i e s i n each b e e t l e community ( F i g s . 9 b ; 1 7 d ) . Lake 1 had a wide s i z e range o f predaceous D y t i s c i d a e o c c u r r i n g w i t h more o r l e s s equal abundance, Lakes 2-5 a l s o had a wide range o f s i z e s b u t were dominated by medium-si zed p r e d a t o r s , and h i g h s a l i n i t y Lakes 6 - 8 were p o p u l a t e d a l m o s t e x c l u s i v e l y by s m a l l p r e d a t o r s . Small and l a r g e h e r b i v o r e s were abundant i n Lake 1 , o n l y s m a l l h e r b i v o r e s were p r e s e n t and were abundant i n Lake 2 - 5 , and s m a l l forms were p r e s e n t b u t r e l a t i v e l y r a r e i n s a l i n e l a k e s . Body s i z e may be r e l a t e d t o t h e p o t e n t i a l o s m o r e g u l a t o r y c a p a c i t y o f C o l e o p t e r a as o n l y r e l a t i v e l y s m a l l s p e c i e s appear t o l e r a n t o f a l l s a l i n i t i e s o r a r e found a t h i g h s a l i n i t i e s . A l t e r n a t i v e l y , L a r s o n (1985) s u g g e s t s t h a t s p e c i e s - r i c h c o l e o p t e r a n faunas w i t h a v a r i e t y o f abundant s i z e groups a r e t y p i c a l o f s e a s o n a l h a b i t a t s o r s h a l l o w v e g e t a t i o n - r i c h s i t e s w i t h s t r o n g s e a s o n a l n u t r i e n t and p r o d u c t i o n p u l s e s . I f s o , then macrophyte faunas and p r i m a r y 94 p r o d u c t i o n may a f f e c t c o l e o p t e r a n community s t r u c t u r e i n c o n c e r t w i t h s a l i n i t y . T h i s study showed i n c r e a s e d d e n s i t i e s o f C o l e o p t e r a w i t h i n c r e a s e d s a l i n i t y . One p o s s i b l e e x p l a n a t i o n o f t h i s phenomenon s u g g e s t s t h a t few organisms are adapted t o extreme s a l i n i t i e s , b u t t h o s e few a r e o f t e n found i n enormous numbers owing t o l a c k o f c o m p e t i t i o n ( B e a d l e , 1 9 4 3 ) . F u r t h e r m o r e , S i m b e r l o f f & W i l s o n found t h a t i s l a n d s w i t h r e l a t i v e l y few s p e c i e s ( i n t h e i r c a s e owing t o d i s p e r s a l l i m i t a t i o n s ) , have a b n o r m a l l y l a r g e p o p u l a t i o n s o f t h o s e s p e c i e s owing t o absence o f c o m p e t i t o r s and p r e d a t o r s [ s e e S i m b e r l o f f (1974) f o r summary]. T h e r e f o r e , c o m p e t i t i o n and p r e d a t i o n may be f a c t o r s i m p o r t a n t i n s t r u c t u r i n g C o l e o p t e r a communities i n f r e s h w a t e r l a k e s . C o l e o p t e r a community p a r a m e t e r s , from l i g h t t r a p s , s u p p o r t the h y p o t h e s i s t h a t s a l i n e l a k e s have l e s s d i v e r s e communities than f r e s h w a t e r o n e s . A l l t r a d i t i o n a l d i v e r s i t y i n d i c e s and the new super community i n d i c e s show i n v e r s e t r e n d s o r s i g n i f i c a n t i n v e r s e c o r r e l a t i o n s w i t h s a l i n i t y i n terms o f taxonomic s p e c i e s , e c o l o g i c a l c a t e g o r i e s , and t r o p h i c l e v e l s ( T a b l e 1 0 ) . Super community i n d i c e s demonstrate t h a t w i t h i n c r e a s i n g s a l i n i t y , t h e c o m p l e x i t y o f a q u a t i c b e e t l e communities d e c r e a s e s r e l a t i v e t o the maximum c o m p l e x i t y p o s s i b l e , i n terms o f both s p e c i e s and e c o l o g i c a l c a t e g o r i e s . The h i e r a r c h i c a l d i v i s i o n o f t r a d i t i o n a l d i v e r s i t y i n d i c e s r e v e a l e d a h i g h l y s i g n i f i c a n t d e c r e a s e i n t r o p h i c l e v e l d i v e r s i t y w i t h i n c r e a s i n g s a l i n i t y , b u t o n l y a t r e n d o f d e c r e a s i n g s p e c i e s d i v e r s i t y w i t h i n t r o p h i c l e v e l s . T h i s s u g g e s t s t h a t C o l e o p t e r a community s t r u c t u r e i s governed t o some e x t e n t by p h y s i o l o g i c a l c o n s t r a i n t s , b u t food r e s o u r c e s p l a y a much more i m p o r t a n t r o l e , even though they a r e p r o b a b l y r e l a t e d t o s a l i n i t y . F u r t h e r e x a m i n a t i o n o f f o o d r e s o u r c e s s h o u l d i n c l u d e macrophytes 95 f o r h e r b i v o r o u s s p e c i e s and p o t e n t i a l prey forms f o r p r e d a t o r s . HEMIPTERAN COMMUNITIES The d i s t r i b u t i o n p a t t e r n o f Hemiptera i n the B e c h e r ' s P r a i r i e l a k e s e r i e s was t h a t o f a p r i m a r i l y f r e s h w a t e r group c o n t a i n i n g a few t a x a t h a t can t o l e r a t e moderate o r h i g h s a l i n i t i e s . Such a p a t t e r n was a l s o found w i t h the Odonata (Cannings & C a n n i n g s , 1 9 8 5 ) . One s p e c i e s ( C e n o c o r i x a  b i f i d a ) o c c u r r e d i n a l l l a k e s , two s p e c i e s ( C . e x p l e t a and D a s y c o r i x a  r a w s o n i ) o c c u r r e d i n o n l y s a l i n e l a k e s , and were r e p l a c e d by s e v e r a l s p e c i e s (Cymatia a m e r i c a n a , C a l l i c o r i x a a u d e n i , H e s p e r o c o r i x a l a e v i g a t a , N o t o n e c t a k i r b y i and N. u n d u l a t a ) i n more f r e s h w a t e r l a k e s ( F i g s . 11a; 1 2 a ) . A l l s p e c i e s were i n d i g e n o u s t o l a k e s they were found i n , e x c e p t s i n g l e r e c o r d s o f H. l a e v i g a t a and C. americana i n Lakes 6 and 5 r e s p e c t i v e l y , and s p e c i e s are not known t o breed i n o t h e r l a k e s w i t h i n the s e r i e s ( S c u d d e r , 1 9 6 9 a ) . The range o f s a l i n i t i e s i n h a b i t e d by v a r i o u s Hemiptera can be d e f i n e d w i t h some p r e c i s i o n , b u t the n a t u r e o f p o s s i b l e c a u s e s d e t e r m i n i n g range l i m i t s i s l e s s c e r t a i n . I t i s p r o b a b l e t h a t the i n h i b i t o r y e f f e c t s o f s a l i n i t y on a d u l t s ( S c u d d e r , 1969a; 1969b; Scudder et , 1972; Knowles & W i l l i a m s , 1973; Tones & Hammer, 1975) o r eggs ( B a n k s , 1949; D a v i s , 1966) d e t e r m i n e the upper l i m i t s o f s a l i n i t y i n h a b i t e d by t h e v a r i o u s s p e c i e s , whereas l o w e r l i m i t s , i f a n y , are o f t e n a t t r i b u t e d t o b i o l o g i c a l f a c t o r s . Perhaps the b e s t documented example i s a s e r i e s o f s t u d i e s on the d i s t r i b u t i o n o f two c l o s e l y r e l a t e d c o r i x i d s , C e n o c o r i x a b i f i d a and C. e x p l e t a , i n t h e s t u d y l a k e s e r i e s [ s e e Scudder (1983) f o r r e v i e w ] . These s p e c i e s d i f f e r p h y s i o l o g i c a l l y i n t h e i r a b i l i t y t o t o l e r a t e h i g h s a l i n i t y , C . e x p l e t a o c c u r s a t much h i g h e r s a l i n i t i e s than C. b i f i d a . A l t h o u g h both 96 s p e c i e s a r e a b l e t o l i v e a t low s a l i n i e s , C . e x p l e t a does n o t o c c u r below 5000 uS as i t appears unable t o s u r v i v e m i t e p a r a s i t i s m . There a r e numerous o t h e r r e c o r d s o f e c t o p a r a s i t i c m i t e s on c o r i x i d s ( D a v i d s , 1973; H a r r i s & H a r r i s o n , 1974; M a r t i n , 1 9 7 5 ) . Other p o s s i b l e f a c t o r s a f f e c t i n g the c o m p o s i t i o n and s t r u c t u r e o f hemipteran communities i n the study l a k e s i n c l u d e i n t e r s p e c i f i c c o m p e t i t i o n and temporal p a r t i t i o n i n g o f b r e e d i n g ( I s t o c k , 1 9 7 3 ) , the amount and v a r i e t y o f v e g e t a t i o n c o v e r (Macan, 1938; 1962; S a v a g e , 1971; van V i e r s s e n & V e r h o e v e n , 1 9 8 3 ) , egg c a n n i b a l i s m ( C r i s p , 1960; P a j u n e n , 1970; S c u d d e r , 1 9 7 6 ) , v e r t e b r a t e p r e d a t i o n (Macan, 1 9 6 5 ) , and i n v e r t e b r a t e p r e d a t i o n . A l t h o u g h i t i s known t h a t i n v e r t e b r a t e s such as l a r v a l D y t i s c i d a e prey on H e m i p t e r a , t h e r e has been no i n t e n s i v e study o f i n v e r t e b r a t e p r e d a t o r s . E c o l o g i c a l l y , a l l a q u a t i c Hemiptera b e l o n g t o t h e same t r o p h i c l e v e l and d i f f e r o n l y i n s i z e . In t h i s s t u d y , v a r i o u s l y s i z e d Hemiptera o c c u r r e d i n f r e s h t o m o d e r a t e l y s a l i n e l a k e s and s m a l l forms o c c u r r e d i n a l l l a k e s , b u t o n l y s m a l l forms were found w i t h i n c r e a s i n g s a l i n i t y ( F i g s , l i b ; 1 2 b ) . A q u a t i c hemipteran communities i n E n g l i s h s a l i n e l a k e s ( S a v a g e , 1971) and Dutch s u p r a - l i t t o r a l p o o l s (van V i e r s s e n & V e r h o e v e n , 1983) have s i m i l a r p a t t e r n s o f community c o m p o s i t i o n w i t h v a r i o u s c o n d i t i o n s o f w a t e r c h e m i s t r y . Savage r e p o r t s the o c c u r r e n c e o f S i g a r a d o r s a l i s (mean l e n g t h 7 mm) over a wide range o f s a l i n i t i e s , and an accompanying s u c c e s s i o n o f p r o g r e s s i v e l y s m a l l e r s p e c i e s w i t h i n c r e a s i n g s a l i n i t y : S . f a l l e n i ( 7 . 5 mm), S . c o n c i n n a ( 7 . 3 mm), S . s t a g n a l i s ( 6 . 5 mm). Van V i e r s s e n & Verhoeven (1983) r e p o r t two s m a l l s p e c i e s , S . l a t e r a l i s ( 5 . 8 mm) and S . s t a g n a l i s ( 6 . 5 mm), o c c u r r i n g o v e r a wide range o f c h l o r i n i t i e s , and c o - o c c u r r i n g w i t h a v a r i e t y o f s p e c i e s i n c l u d i n g C a l l i c o r i x a c o n c i n n a (7 mm), H e s p e r o c o r i x a l i n n e i ( 7 . 5 mm), C o r i x a a f f i n i s (9 mm) and C. p u n c t a t a (14 97 mm) a t low c h l o r i n i t i e s . I n c r e a s e d d e n s i t i e s o f Hemiptera were o b s e r v e d w i t h i n c r e a s i n g s a l i n i t y , as a l s o seen i n t h e c o l e o p t e r a n communities a b o v e . T h i s a s s o c i a t i o n , c o u p l e d w i t h the i n v e r s e a s s o c i a t i o n between the number o f s p e c i e s o r c a t e g o r i e s and s a l i n i t y , s u g g e s t s t h a t the few Hemiptera adapted to h i g h s a l i n i t i e s o c c u r i n enormous numbers owing t o l a c k o f c o m p e t i t i o n and p r e d a t i o n ( B e a d l e , 1943; S i m b e r l o f f , 1 9 7 4 ) . Hemiptera community parameters s u p p o r t the h y p o t h e s i s t h a t l e s s d i v e r s e communities a r e found i n more s a l i n e h a b i t a t s , when measures o f d i v e r s i t y i n c o r p o r a t e t h e r e l a t i v e abundance o f d i f f e r e n t a n i m a l s . For the most p a r t , community parameters f o r Hemiptera c a u g h t i n l i g h t t r a p s and sweep n e t s are p o s i t i v e l y c o r r e l a t e d w i t h each o t h e r ( T a b l e 9 ) , i n d i c a t i n g t h a t a good r e p r e s e n t a t i o n o f t h e hemipteran community i s p r o v i d e d by both t e c h n i q u e s . Of the t r a d i t i o n a l d i v e r s i t y i n d i c e s , t h e d i v e r s i t y o f e c o l o g i c a l c a t e g o r i e s shows a much s t r o n g e r n e g a t i v e a s s o c i a t i o n w i t h s a l i n i t y than the u s u a l s p e c i e s d i v e r s i t y ( T a b l e 1 0 ) . T h i s s u g g e s t s t h a t an e c o l o g i c a l c l a s s i f i c a t i o n o f a n i m a l s may b e t t e r d e s c r i b e community s t r u c t u r e than o r d i n a r y taxonomy. The i n v e r s e a s s o c i a t i o n between s a l i n i t y and t h e d i v e r s i t y o f e c o l o g i c a l c a t e g o r i e s r e f l e c t s t h e f a c t t h a t v a r i o u s l y s i z e d forms were found i n f r e s h t o m o d e r a t e l y s a l i n e l a k e s , s m a l l forms o c c u r r e d i n a l l l a k e s , b u t o n l y s m a l l forms were found w i t h i n c r e a s i n g s a l i n i t y . The p o s i t i v e a s s o c i a t i o n between s a l i n i t y and mean s p e c i e s d i v e r s i t y per e c o l o g i c a l c a t e g o r y demonstrates t h a t a l t h o u g h t h e r e was a w i d e r range o f s i z e s i n f r e s h w a t e r l a k e s , fewer s p e c i e s b e l o n g e d t o each s i z e g r o u p . One p o s s i b l e e x p l a n a t i o n o f the mechanisms c o n t r o l l i n g the o b s e r v e d s t r u c t u r e o f Hemiptera communities i n the study l a k e s i s as f o l l o w s . 98 Because a l l s p e c i e s found a r e t y p i c a l f r e s h w a t e r i n s e c t s , the upper l i m i t s o f s p e c i e s d i s t r i b u t i o n s a r e p r o b a b l y d e t e r m i n e d p h y s i o l o g i c a l l y , and o n l y 3 o f the s p e c i e s e n c o u n t e r e d a r e w e l l adapted t o s u r v i v e the h i g h s a l i n i t i e s i n t h i s l a k e s e r i e s . I t i s known t h a t C e n o c o r i x a e x p l e t a i s e l i m i n a t e d from low s a l i n i t y l a k e s by m i t e p a r a s i t i s m ( S c u d d e r , 1 9 8 3 ) , b u t v i r t u a l l y n o t h i n g i s known about t h e b i o l o g y o f D a s y c o r i x a rawsoni and why i t o c c u r s o n l y a t h i g h s a l i n i t i e s . As s u g g e s t e d above f o r C o l e o p t e r a , body s i z e may be r e l a t e d t o t h e p o t e n t i a l o s m o r e g u l a t o r y c a p a c i t y o f Hemiptera as o n l y r e l a t i v e l y s m a l l s p e c i e s appear t o l e r a n t o f a l l s a l i n i t i e s , o r a r e found a t h i g h s a l i n i t i e s . The f a c t t h a t h e m i p t e r a n s i n h a b i t i n g f r e s h t o m o d e r a t e l y s a l i n e w a t e r s c o v e r a wide range o f s i z e s w i t h r e l a t i v e l y fewer s p e c i e s per s i z e c a t e g o r y s u g g e s t s t h a t c o m p e t i t i o n may p l a y , o r have p l a y e d , a r o l e i n s t r u c t u r i n g communities i n t h e s e l a k e s . T h i s was a l s o s u g g e s t e d by t h e p o s i t i v e a s s o c i a t i o n between Hemiptera d e n s i t y and s a l i n i t y . Assuming t h a t t h e e c o l o g i c a l n i c h e o f an animal i s i n d i c a t e d by body s i z e , t h e wide s i z e range w i t h r e l a t i v e l y few s p e c i e s per s i z e group s u g g e s t s t h a t s p e c i e s have minimal n i c h e o v e r l a p , hence r e d u c i n g t h e p o s s i b i l i t y o f c o m p e t i t i o n . In h i g h s a l i n i t i e s , i n t e r s p e c i f i c c o m p e t i t i o n i s n o t a problem so r e l a t i v e l y more s p e c i e s can occupy one s i z e g r o u p . Much o f t h i s argument i s p u r e l y s p e c u l a t i v e , b u t b e f o r e one can e l u c i d a t e the mechanisms c o n t r o l l i n g community s t r u c t u r e i n t h i s s a l i n e l a k e s e r i e s , more d e t a i l e d a u t e c o l o g i c a l s t u d i e s o f a q u a t i c H e m i p t e r a a r e r e q u i r e d . ENTIRE FAUNAL COMMUNITY Of the t h r e e s a m p l i n g t e c h n i q u e s used i n t h i s s t u d y , submerged l i g h t t r a p s p r o v i d e the b e s t o p p o r t u n i t y t o examine t h e s t r u c t u r e o f the e n t i r e f a u n a l community as they c o l l e c t e d the most s p e c i e s and e c o l o g i c a l 99 c a t e g o r i e s , and they were p r a c t i c a l t o work w i t h . Sweep n e t samples c o l l e c t e d more s p e c i e s , but i n such enormous numbers t h a t they were i m p o s s i b l e t o work w i t h . L i g h t t r a p s samples do not n e c e s s a r i l y r e p r e s e n t f u n c t i o n i n g communities as a c t i v e l y swimming a n i m a l s w i t h p o s i t i v e p h o t o t a x i c r e s p o n s e s a r e s e l e c t i v e l y s a m p l e d , so r e s u l t s must be t r e a t e d w i t h c a u t i o n . The r e l a t i v e abundance o f s p e c i e s and e c o l o g i c a l c l a s s e s i n t h e f a u n a l community d i f f e r e d markedly among l a k e s ( F i g . 8 ) , as seen i n o t h e r d a t a s e t s above. A l l l a k e s were n u m e r i c a l l y dominated by s p e c i e s o f C l a d o c e r a and Copepoda, and e c o l o g i c a l l y by l a r g e s i z e d f i l t e r f e e d e r s . These g r o u p s , t h e i r i n f l u e n c e on the arrangement of l a k e s i n dendrograms, and the mechanisms c o n t r o l l i n g t h e i r community s t r u c t u r e , a r e d i s c u s s e d above i n the s e c t i o n on z o o p l a n k t o n c o m m u n i t i e s . Members o f a l l t r o p h i c l e v e l s were p r e s e n t i n each l a k e , and Lake 1 had t h e w i d e s t range o f s i z e groups i n each l e v e l . As s a l i n i t y i n c r e a s e d , fewer s i z e c a t e g o r i e s were r e p r e s e n t e d i n each t r o p h i c l e v e l . Perhaps the most i m p o r t a n t c o n c l u s i o n drawn from a n a l y s i s o f the l i g h t t r a p samples o f t h e e n t i r e fauna i s t h a t o b s e r v a t i o n s o f the e n t i r e fauna p r e s e n t a d i f f e r e n t p i c t u r e than t h o s e o f i t s component s u b g r o u p s . T h i s s t u d y shows t h a t n u m e r i c a l l y dominant subgroups can d i c t a t e p a t t e r n s o b s e r v e d i n the e n t i r e community and mask i m p o r t a n t p a t t e r n s i n o t h e r s u b g r o u p s . P a t t e r n s o b s e r v e d f o r the e n t i r e community appeared much the same as t h o s e o f the e n t o m o s t r a c a n subcommunity, and p a t t e r n s seen i n C o l e o p t e r a and Hemipetra communities were h i d d e n . Dendrograms i l l u s t r a t i n g E u c l i d e a n d i s t a n c e s between l a k e s based on the e n t i r e fauna ( F i g . 1 6 ) , are much t h e same as t h o s e drawn from z o o p l a n k t o n communities ( F i g s . 14; 1 5 ) . The most f r e s h w a t e r Lake 1 i s l a s t t o j o i n the c l u s t e r r e f l e c t i n g i t s 100 u n i q u e , s p e c i e s r i c h c o m p o s i t i o n and low d e n s i t y ; Lake 4 p e n u l t i m a t e l y j o i n s the c l u s t e r r e f l e c t i n g i t s e x t r e m e l y h i g h d e n s i t y and d i v e r s i t y ; t h e r e m a i n i n g l a k e s are s p l i t i n t o two groups of h i g h and low s a l i n i t y l a k e s . A s s o c i a t i o n s between a b i o t i c and b i o t i c parameters o f t h e e n t i r e fauna are q u i t e d i f f e r e n t from t h o s e found i n i t s component subcommunities ( T a b l e 1 0 ) . Community parameters c a l c u l a t e d from l i g h t t r a p samples o f the e n t i r e fauna s u p p o r t t h e h y p o t h e s i s t h a t h a b i t a t s o f i n c r e a s i n g s a l i n i t y s u p p o r t communities o f d e c r e a s i n g d i v e r s i t y , when measures o f d i v e r s i t y i n c o r p o r a t e t h e r e l a t i v e abundance o f a n i m a l s . I n v e r s e a s s o c i a t i o n s were found between s a l i n i t y and the new super community i n d i c e s i n d i c a t i n g t h a t w i t h i n c r e a s i n g s a l i n i t y , the c o m p l e x i t y o f f a u n a l communities d e c r e a s e s r e l a t i v e t o the maximum c o m p l e x i t y p o s s i b l e . None o f t h e h i e r a r c h i c a l d i v e r s i t y i n d i c e s were c o r r e l a t e d w i t h a b i o t i c v a r i a b l e s t h e r e b y p r o v i d i n g no c l u e s t o c o n t r o l l i n g mechanisms. Summary T h i s second c h a p t e r examines the r e l a t i o n s h i p between w a t e r s a l i n i t y and f a u n a l community s t r u c t u r e , and t e s t s the d i v e r s i t y - s t a b i l i t y h y p o t h e s i s t h a t s a l i n e h a b i t a t s have l e s s d i v e r s e communities than f r e s h w a t e r o n e s . Three d i f f e r e n t s a m p l i n g t e c h n i q u e s , van Dorn b o t t l e s , submerged l i g h t t r a p s and sweep n e t s , were used t o c o l l e c t a q u a t i c a r t h r o p o d s i n t h e l i m n e t i c and l i t t o r a l zones o f a s a l i n e l a k e s e r i e s . In t o t a l , 84 t a x a o f a q u a t i c a r t h r o p o d s were found i n the e i g h t l a k e s and s p e c i e s c h a r a c t e r i s t i c o f h i g h s a l i n i t i e s (>5000 u S ) , moderate o r low s a l i n i t i e s (<5000 u S ) , o r t o l e r a n t o f a l l s a l i n i t i e s were p r e s e n t i n the 101 s e r i e s . Each study l a k e s u p p o r t e d a d i s t i n c t l y d i f f e r e n t f a u n a l assemblage and t h e s e d i s t r i b u t i o n p a t t e r n s were c l o s e l y r e l a t e d t o s a l i n i t y . The s t r u c t u r e o f the e n t i r e f a u n a l community and i t s e n t o m o s t r a c a , c o l e o p t e r a n and hemipteran s u b s e t s were c h a r a c t e r i z e d u s i n g two schemes o f c l a s s i f i c a t i o n (taxonomic and e c o l o g i c a l ) , m u l t i v a r i a t e c l a s s i f i c a t i o n t e c h n i q u e s , and 13 n u m e r i c a l parameters i n c l u d i n g d e n s i t y , r i c h n e s s , d i v e r s i t y , h i e r a r c h i c a l d i v e r s i t y , and new super community i n d i c e s . No one method was s u f f i c i e n t t o summarize r e l a t i o n s h i p s between s a l i n i t y and communitiy s t r u c t u r e . I n s t e a d , a l l c o n t r i b u t e d some i n f o r m a t i o n t o community c h a r a c t e r i z a t i o n s and hypotheses about c o n t r o l l i n g mechanisms. Water c h e m i s t r y appeared t o be the most i m p o r t a n t a b i o t i c v a r i a b l e i n f l u e n c i n g f a u n a l community s t r u c t u r e and l i t t l e e v i d e n c e was found f o r m o r p h o l o g i c a l c o r r e l a t i o n s . In a l l sample s e t s , i n c r e a s e d s a l i n i t y was accompanied by a d e c r e a s e i n t h e number o f s p e c i e s o r e c o l o g i c a l c a t e g o r i e s c a p a b l e o f s u r v i v i n g i n such c o n d i t i o n s , and i n t h e number o f s p e c i e s o r e c o l o g i c a l c a t e g o r i e s r e l a t i v e t o the t o t a l number a v a i l a b l e f o r c o l o n i z a t i o n . When measures o f community s t r u c t u r e i n c o r p o r a t e d r e l a t i v e a b u n d a n c e s , each d a t a s e t had t o be examined s e p a r a t e l y as the s t r u c t u r e o f t h e s e subgroups showed d i f f e r e n t p a t t e r n s o f a s s o c i a t i o n w i t h s a l i n i t y . ZOOPLANKTON. Both w a t e r b o t t l e and l i g h t t r a p samples p r e s e n t e d s i m i l a r p a t t e r n s of z o o p l a n k t o n community s t r u c t u r e . E v i d e n c e s u g g e s t s t h a t mechanisms s h a p i n g z o o p l a n k t o n community s t r u c t u r e a r e p r i m a r i l y r e l a t e d t o a v a i l a b l e f o o d s u p p l y and s p e c i e s ' n u t r i t i o n a l r e q u i r e m e n t s , and s e c o n d a r i l y t o o s m o r e g u l a t o r y s t r e s s , a l t h o u g h s a l i n i t y may u l t i m a t e l y a f f e c t t h e t r o p h i c s t a t u s o f l a k e s . Changes i n the taxonomic and e c o l o g i c a l c o m p o s i t i o n o f z o o p l a n k t o n communities w i t h d e c r e a s i n g s a l i n i t y were a n a l o g o u s t o t h o s e r e p o r t e d w i t h i n c r e a s i n g e u t r o p h i c a t i o n . When 102 i n c o r p o r a t i n g r e l a t i v e abundances o f a n i m a l s , t h e o n l y e v i d e n c e found t o i n d i c a t e t h a t z o o p l a n k t o n d i v e r s i t y d e c r e a s e d w i t h i n c r e a s i n g s a l i n i t y , was an i n v e r s e a s s o c i a t i o n between s a l i n i t y and t r o p h i c l e v e l d i v e r s i t y . COLEOPTERA. Sweep n e t s were i n a d e q u a t e t o q u a n t i t a t i v e l y sample a q u a t i c C o l e o p t e r a , so l i g h t t r a p samples were p r i m a r i l y used t o c h a r a c t e r i z e communites. S a l i n i t y , c o m p e t i t i o n and f o o d s u p p l y c o u l d a l l be i m p o r t a n t mechanisms c o n t r o l l i n g the s t r u c t u r e o f C o l e o p t e r a c o m m u n i t i e s . S p e c i e s r i c h communities c o v e r i n g a wide range o f s i z e groups and t r o p h i c l e v e l s , were found i n f r e s h w a t e r l a k e s , b u t o n l y a few r e l a t i v e l y s m a l l s p e c i e s were found i n s a l i n e l a k e s , and o n l y s m a l l s p e c i e s were found i n a l l s a l i n i t i e s . T h i s may i n d i c a t e t h a t body s i z e i s r e l a t e d t o t h e p o t e n t i a l o s m o r e g u l a t o r y c a p a c i t y o f C o l e o p t e r a . A d d i t i o n a l l y , a wide s i z e range o f s p e c i e s may i n d i c a t e minimal n i c h e o v e r l a p a t low s a l i n i t i e s , hence r e d u c i n g t h e p o s s i b i l i t y o f c o m p e t i t i o n . Decreased t r o p h i c l e v e l d i v e r s i t y w i t h i n c r e a s i n g s a l i n i t y may i n d i c a t e t h a t f o o d s u p p l y i s more v a r i e d i n f r e s h w a t e r l a k e s . C o l e o p t e r a n d e n s i t y i n c r e a s e d w i t h i n c r e a s i n g s a l i n i t y , p o s s i b l y because the few organisms adapted t o extreme s a l i n i t i e s a r e o f t e n found i n enormous numbers owing t o l a c k o f c o m p e t i t i o n and p r e d a t i o n . HEMIPTERA. Sweep n e t and l i g h t t r a p samples p r o v i d e d s i m i l a r r e p r e s e n t a t i o n s o f t h e l i t t o r a l H e m i p t e r a . D i s t r i b u t i o n p a t t e r n s o f hemipteran s p e c i e s were o f a p r i m a r i l y f r e s h w a t e r group c o n t a i n i n g a few t a x a t h a t can t o l e r a t e moderate o r h i g h s a l i n i t i e s . Upper l i m i t s o f d i s t r i b u t i o n were p r o b a b l y d e t e r m i n e d p h y s i o l o g i c a l l y , and s p e c i e s a p p e a r i n g o n l y i n h i g h s a l i n i t y l a k e s were p r o b a b l y e l i m i n a t e d from low s a l i n i t i e s by b i o l o g i c a l f a c t o r s . Body s i z e may be r e l a t e d t o p o t e n t i a l o s m o r e g u l a t o r y c a p a c i t y as o n l y r e l a t i v e l y s m a l l s p e c i e s appeared t o be 103 t o l e r a n t o f a l l s a l i n i t i e s o r were found a t h i g h s a l i n i t i e s . E v i d e n c e s u g g e s t s t h a t c o m p e t i t i o n may p l a y , o r have p l a y e d , a r o l e i n s t r u c t u r i n g hemipteran communities i n f r e s h w a t e r l a k e s , but n o t s a l i n e l a k e s . The wide s i z e range o f Hemiptera and r e l a t i v e l y few s p e c i e s per s i z e group a t low s a l i n i t i e s s u g g e s t s t h a t s p e c i e s have minimal n i c h e o v e r l a p , hence r e d u c i n g the p o s s i b i l i t y o f c o m p e t i t i o n . I n c r e a s e d d e n s i t y w i t h i n c r e a s i n g s a l i n i t y s u g g e s t e d t h a t t h e few Hemiptera adapted t o extreme s a l i n i t i e s were found i n enormous numbers owing t o l a c k o f c o m p e t i t i o n and p r e d a t i o n a t h i g h s a l i n i t i e s . ENTIRE FAUNAL COMMUNITY. With i n c r e a s e d s a l i n i t y , t h e c o m p l e x i t y o f the e n t i r e f a u n a l community d e c r e a s e d r e l a t i v e to t h e maximum c o m p l e x i t y p o s s i b l e . No i n s i g h t i n t o p o s s i b l e c o n t r o l l i n g mechanisms was f o u n d . O b s e r v a t i o n s o f t h e e n t i r e fauna p r e s e n t e d a d i f f e r e n t p i c t u r e than t h o s e o f i t s component s u b g r o u p s , i n d i c a t i n g t h a t n u m e r i c a l l y dominant subgroups can d i c t a t e p a t t e r n s o b s e r v e d i n t h e e n t i r e community and mask i m p o r t a n t p a t t e r n s i n o t h e r s u b g r o u p s . 104 CHAPTER 3: MACROPHYTE COMMUNITIES Introduction The aim o f t h i s c h a p t e r i s t o examine and q u a n t i f y t h e r e l a t i o n s h i p between w a t e r s a l i n i t y and a q u a t i c macrophyte communities i n a s a l i n e l a k e s e r i e s . The main o b j e c t i v e o f t h i s study was t o i n v e s t i g a t e t h e r e l a t i o n s h i p between s a l i n i t y and a r t h r o p o d communities ( C h a p t e r 2 ) , b u t because t h e fauna i s c l o s e l y r e l a t e d w i t h the f l o r a , I c o n s i d e r e d i t n e c e s s a r y t o a l s o i n v e s t i g a t e the macrophyte community. The r e l a t i o n s h i p s between f a u n a l and f l o r a l communities w i l l be examined i n C h a p t e r 4 . S t u d i e s o f s a l i n e l a k e f l o r a (Rawson & Moore, 1944; Hammer e t a l . , 1975; Reynolds & R e y n o l d s , 1975; T o p p i n g , 1975; B r o c k , 1981; Timms, 1981; Brock & L a n e , 1983; Brock & S h i e l , 1983; Hammer e t j a K , 1983; L i e f f e r s & Shay, 1983) p r o v i d e some e v i d e n c e t o s u p p o r t the h y p o t h e s i s t h a t s a l i n e l a k e s s u p p o r t fewer and l e s s p r o d u c t i v e s p e c i e s than f r e s h e r o n e s . I t has l o n g been known t h a t w a t e r c h e m i s t r y i s perhaps t h e most i m p o r t a n t f a c t o r i n f l u e n c i n g t h e d i s t r i b u t i o n o f a q u a t i c p l a n t s p e c i e s w i t h i n t h e i r t o l e r a n c e ranges ( M o y l e , 1945; Seddon, 1 9 7 2 ) . Y e t , t h e r e i s no study p r o v i d i n g a comprehensive q u a n t i t a t i v e a n a l y s i s o f macrophyte community s t r u c t u r e i n a s a l i n e l a k e s e r i e s f r e e o f c o n f o u n d i n g a b i o t i c f a c t o r s . In t h i s s t u d y , t h e q u e s t i o n o f how a q u a t i c p l a n t s a r e a f f e c t e d by s a l i n i t y was viewed i n terms o f two h y p o t h e s e s : t h e d i v e r s i t y - s t a b i l i t y h y p o t h e s i s , and a l e s s c o m p l i c a t e d p r o d u c t i v i t y - s a l i n i t y h y p o t h e s i s . As d e f i n e d i n the General I n t r o d u c t i o n , t h i s f i r s t h y p o t h e s i s s t a t e s t h a t e n v i r o n m e n t a l l y s t a b l e h a b i t a t s have more d i v e r s e communities than l e s s s t a b l e o n e s , where s a l i n i t y d e f i n e s e n v i r o n m e n t a l s t a b i l i t y i n terms o f s e v e r i t y ( C h a p t e r 1 ) . The second h y p o t h e s i s s i m p l y p r e d i c t s reduced 105 p r o d u c t i v i t y o f macrophytes i n more s a l i n e l a k e s , as e x c e s s i v e s a l i n i t y d i s r u p t s normal growth and m e t a b o l i s m o f p l a n t s so t h a t s p e c i e s a r e unable t o s u r v i v e o r a t l e a s t e x p e r i e n c e r e d u c e d p r o d u c t i v i t y ( W a i s e l , 1 9 7 2 ) . Topping (1975) found t h a t p h y t o p l a n k t o n p r o d u c t i v i t y d e c r e a s e d a t h i g h e r s a l i n i t i e s and W a i s e l (1972) s u g g e s t s t h e same f o r m a c r o p h y t e s , b u t t h i s i s a much n e g l e c t e d a r e a o f s t u d y . As t h e study l a k e s a r e s m a l l and macrophytes may s i g n i f i c a n t l y c o n t r i b u t e t o t o t a l l a k e p r o d u c t i v i t y ( W e s t l a k e , 1963; 1965; McNaught, 1975; W e t z e l , 1975; C a n f i e l d e t a l ^ . , 1 9 8 3 ) , i t may be i n f o r m a t i v e t o c h a r a c t e r i z e t h e i r macrophyte c o m m u n i t i e s . W i t h o u t m a s s i v e i n v e s t m e n t o f e f f o r t o r t i m e , macrophyte p r o d u c t i v i t y can be d e t e r m i n e d by temporal d i f f e r e n c e s i n s t a n d i n g c r o p . I t i s a t b e s t a c o n s e r v a t i v e e s t i m a t e , i . e . i t w i l l u n d e r e s t i m a t e d i f f e r e n c e s among s i t e s , b u t t h i s i s s u f f i c i e n t f o r t h e aims of t h i s c h a p t e r . Biomass may be s y n t h e s i z e d and p o p u l a t i o n s r e p l a c e d w i t h o u t any change i n s t a n d i n g c r o p , b u t d i f f e r e n c e s i n s t a n d i n g c r o p can o n l y be a t t r i b u t e d t o p r o d u c t i v i t y ( T o p p i n g , 1 9 7 5 ) . T h i s method o f d e t e r m i n i n g annual p r o d u c t i v i t y i s p a r t i c u l a r l y s u i t e d t o communities showing marked annual f l u c t u a t i o n s o f biomass and s u b j e c t t o few l o s s e s d u r i n g t h e p e r i o d o f growth ( W e s t l a k e , 1 9 6 3 ) . In temperate r e g i o n s , l i k e the C h i l c o t i n , l o s s e s due t o n a t u r a l death a r e p r o b a b l y v e r y s m a l l d u r i n g the growing s e a s o n , a t l e a s t u n t i l maximum biomass i s a t t a i n e d ( S c u l t h o r p e , 1 9 6 7 ) , so temporal d i f f e r e n c e s i n s t a n d i n g c r o p a r e n o t an u n r e a s o n a b l e way t o e s t i m a t e r e l a t i v e p r o d u c t i v i t y . As i n C h a p t e r 2 , measures o f l a k e morphometry a r e a l s o compared t o macrophyte community s t r u c t u r e t o t e s t f o r the p o s s i b l e e f f e c t s o f o t h e r p r o c e s s e s such as the s p e c i e s / a r e a phenomenon ( s e e C h a p t e r 1 f o r f u r t h e r d i s c u s s i o n ) . 106 Materials and Methods To i n v e s t i g a t e the r e l a t i o n s h i p between s a l i n i t y and macrophyte c o m m u n i t i e s , t h e s e r i e s o f e i g h t l a k e s was c h a r a c t e r i z e d a b i o t i c a l l y a c c o r d i n g t o w a t e r c h e m i s t r y and l a k e morphometry ( C h a p t e r 1 ) , and b i o t i c a l l y a c c o r d i n g t o macrophyte s p e c i e s d i s t r i b u t i o n , r i c h n e s s , abundance, d i v e r s i t y , h i e r a r c h i c a l d i v e r s i t y , super community i n d i c e s , and p r o d u c t i v i t y . In a d d i t i o n , l a k e s were c l a s s i f i e d i n t o h i e r a r c h i c a l c l u s t e r diagrams on t h e b a s i s of t h e i r macrophyte communities and compared t o s i m i l a r dendrograms produced from a b i o t i c f a c t o r s . THE DATA. S p e c i e s d i s t r i b u t i o n and abundance d a t a used i n t h i s s e c t i o n were k i n d l y p r o v i d e d by t h e Canadian W i l d l i f e S e r v i c e (CWS) from t h e i r 1983 study o f t h e C h i l c o t i n w e t l a n d s . Data i n c l u d e r e l a t i v e abundances o f each macrophyte s p e c i e s , e s t i m a t e d on the B r a u n - B l a n q u e t s c a l e ( B r a u n - B l a n q u e t , 1964) a t mid-summer, i n each o f s e v e r a l l a k e zones c l a s s i f i e d a c c o r d i n g t o the scheme o f Runka & L e w i s ( 1 9 8 1 ) . Zones a r e d e f i n e d w i t h r e s p e c t t o w a t e r d e p t h , w a t e r l e v e l f l u c t u a t i o n s , and p r o p o r t i o n o f emergent p l a n t c o v e r . The o r i g i n a l CWS s u r v e y c o v e r e d many w a t e r b o d i e s i n the C h i l c o t i n , my a n a l y s i s was r e s t r i c t e d t o the e i g h t l a k e s on B e c h e r ' s P r a i r i e used i n my f a u n a l s t u d i e s . A l l t h e s e raw d a t a are p r e s e n t e d i n Appendix F. To measure p r o d u c t i v i t y I c o l l e c t e d t r i p l i c a t e l i t t o r a l p l a n t samples from each o f the e i g h t l a k e s , once a month between May and September 1984. In o r d e r t h a t r e s u l t s be comparable w i t h f a u n a l community p a r a m e t e r s , samples were t a k e n from the same p a r t o f the l i t t o r a l zone t h a t a n i m a l s were c o l l e c t e d i n 1978. One sample c o n s i s t e d o f a l l t h e a q u a t i c p l a n t s w i t h i n a 0 . 1 m2 q u a d r a t a t 20-30 cm d e p t h . Dry w e i g h t s were d e t e r m i n e d a f t e r washing and d r y i n g t h e v e g e t a t i o n a t 100 ° C f o r 24 h o u r s . 107 A b i o t i c parameters o f the l a k e s were c a l c u l a t e d i n the manner o u t l i n e d i n C h a p t e r 1 . S a l i n i t y parameters were r e c a l c u l a t e d f o r 1983 and 1984 as annual v a r i a t i o n s i n s a l i n i t y a r e common i n the study l a k e s and t h e s e changes may a f f e c t t h e b i o t a . CWS p r o v i d e d c o n d u c t i v i t y measures f o r 1983 and I measured c o n d u c t i v i t y monthly w i t h a Radiometer c o n d u c t i v i t y meter i n 1984. V a l u e s f o r morphometric v a r i a b l e s were t a k e n from Topping & Scudder as i n C h a p t e r 1 . COMMUNITY PARAMETERS. From the CWS d a t a I was a b l e t o c a l c u l a t e s p e c i e s r i c h n e s s , p e r c e n t c o v e r , s p e c i e s d i v e r s i t y , h i e r a r c h i c a l d i v e r s i t y , and two super community i n d i c e s . F o r a d e t a i l e d d i s c u s s i o n o f t h e s e terms see C h a p t e r 2 . H i e r a r c h i c a l d i v e r s i t y was used t o t e a s e o u t t h e c o n f o u n d i n g e f f e c t s o f b a s i n m o r p h o l o g y . One would e x p e c t the unique b a s i n shape o f each l a k e t o i n f l u e n c e the number and v a r i e t y o f s p e c i e s t h a t can e s t a b l i s h and s u r v i v e , i r r e s p e c t i v e o f w a t e r c h e m i s t r y . Through t h i s t e c h n i q u e , d i v e r s i t y o f the whole community was d i v i d e d i n t o zone d i v e r s i t y , an a b i o t i c c h a r a c t e r o f b a s i n m o r p h o l o g y , and mean w i t h i n - z o n e s p e c i e s d i v e r s i t y averaged o v e r a l l zones such t h a t : H ' ( s ) = H ' ( z ) + H ' z ( s ) where H ' ( s ) = t o t a l s p e c i e s d i v e r s i t y H ' ( z ) = zone d i v e r s i t y H ' z ( s ) = mean w i t h i n - z o n e s p e c i e s d i v e r s i t y . One would p r e d i c t t h a t by s u b t r a c t i n g t h e a b i o t i c measure o f b a s i n m o r p h o l o g y , any o b s c u r e d r e l a t i o n s h i p between d i v e r s i t y and s a l i n i t y would become more o b v i o u s . S i m i l a r l y , t o t a l d i v e r s i t y was d i v i d e d i n t o h i e r a r c h i c a l components based on growth form (submerged, f l o a t i n g , e m e r g e n t ) . 108 Super community i n d i c e s were c a l c u l a t e d from s p e c i e s p r e s e n c e / a b s e n c e d a t a u s i n g J a c c a r d ' s c o e f f i c i e n t o f s i m i l a r i t y and from c o v e r - a b u n d a n c e d a t a u s i n g E u c l i d e a n d i s t a n c e s . CLASSIFICATION. The method used t o c l u s t e r t h e e i g h t study l a k e s was UPGMA, as d e s c r i b e d i n C h a p t e r 1 . The s i m i l a r i t y i n d i c e s used and methods o f c o m p a r i s o n were t h e same as t h o s e i n C h a p t e r 2 . Results PHYSIOCHEMICAL FEATURES. The e i g h t l a k e s were c h a r a c t e r i z e d a c c o r d i n g t o f i v e a b i o t i c v a r i a b l e s : mean c o n d u c t i v i t y , two p r i n c i p a l component axes based on i o n i c c o m p o s i t i o n , mean d e p t h , and the r a t i o o f s h o r e l i n e development t o a r e a . Morphometric v a r i a b l e s were t h e same as t h o s e i n C h a p t e r 1 ( T a b l e 4 ) , and o t h e r than minor n u m e r i c a l d i f f e r e n c e s , p h y s i o c h e m i c a l f e a t u r e s were much t h e same i n 1978, 1983 and 1984. F i g . 21 p r e s e n t s s a l i n i t y d a t a ; F i g . 22 shows dendrograms. GENERAL DESCRIPTION OF LAKES. A l l l a k e s i n t h e s e r i e s ( e x c e p t Lakes 1 and 7) were s u r r o u n d e d by s t a n d s o f J u n c u s and S c i r p u s , and more f r e s h w a t e r l a k e s d e v e l o p e d heavy a l g a l blooms ( P l a t e 4 ) . A l l l a k e s had l i t t l e o r no v e g e t a t i o n e a r l y i n the season ( P l a t e 5 ) , b u t Lakes 1-5 d e v e l o p e d t h i c k mats o f submerged v e g e t a t i o n by mid-summer: Potamogeton natans i n Lake 1 ( P l a t e 6 ) , M y r i o p h y l l u m e x a l b e s c e n s i n Lake 2 ( P l a t e 7 ) , and a c o m b i n a t i o n o f Potamogeton p e c t i n a t u s and Ruppia o c c i d e n t a l i s i n Lakes 3 - 5 ( P l a t e 8 ) . In 1984 t h e submerged v e g e t a t i o n o f Lake 3 s u f f e r e d c o n s i d e r a b l e damage between m i d - A u g u s t and m i d - S e p t e m b e r , p r o b a b l y by w a t e r fowl o r m u s k r a t s t h a t f a v o u r t h i s l a k e and use h y d r o p h y t e s f o r f o o d and house b u i l d i n g (Munro, 1945; K r u l l , 1970; D a n e l l , 1978; 1 9 7 9 ) . 109 F i g . 2 1 . Seasonal c o n d u c t i v i t y (JJS c m - 1 , 25 ° C ) i n each l a k e i n o r d e r o f i n c r e a s i n g s a l i n i t y (a) f o r 1 9 8 3 , and (b) f o r 1984. # = maximum, O = mean, ^ = r a n g e . (See F i g . 1 f o r l a k e names; see Appendix E f o r n u m e r i c a l v a l u e s ) co Log conductivity ro co Log conductivity ro co CO • c* CD CD cn • C i 05 • o» I l l F i g . 2 2 . C l u s t e r a n a l y s i s o f study l a k e s based on d i s s i m i l a r i t y o f (a) 1983 p r e d i c t e d i o n i c c o m p o s i t i o n , r=0.826 (b) 1983 p r e d i c t e d i o n i c c o m p o s i t i o n p l u s morphometric c h a r a c t e r s , r=0.881 ( c ) 1984 p r e d i c t e d i o n i c c o m p o s i t i o n , r=0.786 (d) 1984 p r e d i c t e d i o n i c c o m p o s i t i o n p l u s morphometric c h a r a c t e r s , r=0.866 (See F i g . 1 f o r l a k e names). 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 Dissimilarity i 8 | 7 I 6 | 5 Lake I 4 I 3 • 2 1 © I 8 ' I 7 6 5 Lake I 4 I 3 J 2 1 6 4 2 0 W Dissimilarity 113 114 P l a t e 7 . 1 3 . v i . 8 4 . Lake 2 ( B a r k l e y L . ) w i t h dense submerged M y r i o p h y l l u m  e x a l b e s c e n s e a r l y i n the s e a s o n , emergent J u n c u s b a l t i c u s i s i n the f o r e g r o u n d . P l a t e 8 . 7 . v i i . 8 4 . Lake 4 (Rock L . ) : c l o s e - u p o f submerged v e g e t a t i o n . Length a c r o s s bottom o f p h o t o g r a p h i s a p p r o x i m a t e l y 1 . 5 m. P l a t e 9 . 1 2 . v i i i . 8 4 . Lake 8 (Barnes L . ) w i t h m a r g i n o f emergent J u n c u s b a l t i c u s , s t a n d i n g 50 cm above w a t e r s u r f a c e . 116 In g e n e r a l , the t h r e e h i g h l y s a l i n e l a k e s had no submerged o r f l o a t i n g v e g e t a t i o n and no heavy a l g a l blooms t y p i c a l o f f r e s h e r w a t e r s . Lakes 6 and 8 had w e l l e s t a b l i s h e d m a r g i n s o f the p e r e n n i a l J u n c u s and showed r e l a t i v e l y few changes i n the l i t t o r a l zone w i t h season ( P l a t e 9 ) . In t h e s e l a k e s J u n c u s was r o o t e d below t h e w a t e r l e v e l t h r o u g h o u t the season whereas i n o t h e r s i t u s u a l l y o c c u r r e d a t o r above w a t e r l e v e l . I t i s not c l e a r why t h e r e was no v e g e t a t i o n i n Lake 7 , i t i s not s i m p l y owing t o w a t e r c h e m i s t r y as h e a l t h y macrophyte growth was found i n more s a l i n e l a k e s . SPECIES DISTRIBUTION. Each l a k e had a unique assemblage o f macrophyte s p e c i e s , and a l t h o u g h t h e r e was some o v e r l a p , no s p e c i e s o c c u r r e d i n a l l l a k e s and many (14) s p e c i e s i n o n l y one l a k e . A t o t a l o f 26 p l a n t s p e c i e s was found i n h a b i t i n g the e i g h t l a k e s ( T a b l e 1 2 ) . Three p r i n c i p a l groups o f s p e c i e s , t h o s e r e s t r i c t e d t o s a l i n e l a k e s , t o f r e s h w a t e r l a k e s , and t h o s e o c c u r r i n g a t moderate s a l i n i t i e s o r t o l e r a n t o f a wide range o f s a l i n i t i e s , were r e v e a l e d when m u l t i v a r i a t e c l a s s i f i c a t i o n c l u s t e r e d s p e c i e s a c c o r d i n g t o w h i c h l a k e s they o c c u r i n ( F i g . 2 3 ) . A t t h e top o f F i g . 23 i s a s m a l l g r o u p , A , o f s p e c i e s i n c l u d i n g D i s t i c h ! i s s t r i c t a , a t y p i c a l h a l o p h y t e , o c c u r r i n g o n l y i n t h e most s a l i n e l a k e . Group B , w i t h two s u b g r o u p s , c o n t a i n s s p e c i e s t h a t o c c u r r e d a t moderate s a l i n i t i e s o r o v e r a wide range o f s a l i n i t i e s . Subgroup B l c o n t a i n s s p e c i e s such as Potamogeton p e c t i n a t u s found i n m o d e r a t e l y s a l i n e l a k e s , and t h e most w i d e s p r e a d s p e c i e s , J u n c u s  b a l t i c u s and S c i r p u s l a s c u s t r i s , found i n s i x o f t h e e i g h t l a k e s . In subgroup B2 a r e s p e c i e s found o n l y i n Lake 2 , i n c l u d i n g M y r i o p h y l l u m  e x a l b e s c e n s , C e r a t o p h y l l u m demersum and Beckmannia s z y i g a c h n e . Group C, a t the bottom o f the dendogram, c o n t a i n s t y p i c a l l y f r e s h w a t e r s p e c i e s , i n c l u d i n g Potamogeton n a t a n s , G l y c e r i a b o r e a l i s , U t r i c u l a r i a v u l g a r i s and 117 T a b l e 1 2 . D i s t r i b u t i o n o f a q u a t i c p l a n t s r e c o r d e d by CWS. S = submerged; F = f l o a t i n g ; E = emergent. (See F i g . 1 f o r l a k e names) growth Number form s p e c i e s l a k e 1 2 3 4 5 6 7 8 1 S F i l a m e n t o u s a l g a e s p . o o o o o 2 S D r e p a n o c l a d u s s p . o 3 S Aphanozomenon f l o s a q u a t i s o o 4 E Polygonum amphibium L. o o 5 F C e r a t o p h y l l u m demersum L. o 6 S M y r i o p h y l l u m e x a l b e s c e n s ( F e r n . ) J e p s . o o 7 F U t r i c u l a r i a v u l g a r i s L. o 8 E S a g i t t a r i a c u n e a t a S h e l d . o 9 S Potamogeton p e c t i n a t u s L. o o o o 10 S P^ . p u s i l l u s L . / b e r c h t o l d i F i e b . o o 11 S P_. r i c h a r d s o n i ( B e n n e t t ) Rydb. o 12 F P_. natans L. o 13 S Ruppia o c c i d e n t a l i s L . o o 14 E J u n c u s b a l t i c u s W i l l d . o o o o o 15 E Carex a t h e r o d e s S p r e n g . o 16 E C. r o s t r a t a S t o k e s o 17 E C. l a n u g i n o s a M i c h x . o 18 E E l e o c h a r i s p a l u s t r i s ( L . ) R. & S . o o o 19 E S c i r p u s americanus P e r s . o 20 E _S. l a c u s t r i s V a h l . o o o o o 21 E Beckmannia s z y i g a c h n e ( S t e n d . ) F e r n . o 22 E D i s t i c h ! i s s t r i c t a ( T o r r . ) Rydb. 23 E G l y c e r i a b o r e a l i s (Nash) B a t c h . o 24 E Hordeum jubatum L. 25 S Sparganium s p . o 26 F Lemna minor L. o o o 118 0 B 1 B B 2 0.2 0.4 0.6 Similarity 0.8 J 2 4 I — 22 19 13 20 14 1 9 3 ' — 1 7 r-io >— 6 11 26 5 21 18 4 16 8 2 25 7 23 12 1.0 Species Fig. 23. Cluster analysis of aquatic macrophyte species based on similarities of lakes occupied, r=0.911. Principal subgroups, designated by stem letters, are discussed in the text. (See Table 12 for species names). 119 S a g g i t a r i a c u n e a t a , t h a t were found o n l y i n Lake 1 . F l o a t i n g - l e a v e d forms were found o n l y i n the two most f r e s h w a t e r l a k e s whereas emergent and submerged forms o c c u r r e d i n a l l l a k e s , as shown i n F i g . 24 d i s p l a y i n g the r e l a t i v e p r o p o r t i o n o f each l a k e c o v e r e d by emergent, submerged o r f l o a t i n g m a c r o p h y t e s . The f i g u r e s u g g e s t s t h a t the r e l a t i v e p r o p o r t i o n o f emergent p l a n t s d e c r e a s e d w i t h i n c r e a s i n g s a l i n i t y . COMMUNITY PARAMETERS. V a l u e s f o r community parameters v a r i e d c o n s i d e r a b l y among l a k e s ( T a b l e 1 3 ) . A l l parameters had z e r o v a l u e s i n Lake 7 , as t h i s l a k e had no v e g e t a t i o n . Maximum v a l u e s f o r s p e c i e s r i c h n e s s , d i v e r s i t y , mean w i t h i n - z o n e d i v e r s i t y , and b o t h super commmunity i n d i c e s o c c u r r e d i n Lake 2 . Lake 4 had t h e h i g h e s t p e r c e n t c o v e r w i t h an e s t i m a t e d 94% o f the l a k e a r e a c o v e r e d by a q u a t i c m a c r o p h y t e s . Water c h e m i s t r y appears t o be the most i m p o r t a n t v a r i a b l e f o r p r e d i c t i n g community p a r a m e t e r s : T a b l e 14 summarizes t h e r e l a t i o n s h i p s between p h y s i o c h e m i c a l v a r i a b l e s and community parameters ( T a b l e 1 3 ) . C o n d u c t i v i t y and PCI both show s i g n i f i c a n t a s s o c i a t i o n s w i t h f i v e parameters and t r e n d s w i t h two more. Of the r e m a i n i n g a b i o t i c v a r i a b l e s e x a m i n e d , PC2 shows no a s s o c i a t i o n w i t h any p a r a m e t e r s ; mean depth i s c o r r e l a t e d w i t h s e v e r a l parameters b u t t h e s i g n ( n e g a t i v e ) o f the o b s e r v e d r e l a t i o n s h i p s i s c o n t r a r y t o p r e d i c t i o n s and a t t r i b u t e d t o the chance c o r r e l a t i o n o f mean depth w i t h s a l i n i t y ( T a b l e 5 ) . T h i s c o i n c i d e n t a l r e l a t i o n o f community parameters w i t h l a k e s i z e was a l s o seen i n comparison w i t h f a u n a l communities ( C h a p t e r 2 ) . DL/\ 1 S a s s o c i a t e d w i t h some p a r a m e t e r s , b u t i n each c a s e s a l i n i t y measures show a s t r o n g e r c o r r e l a t i o n w i t h the same parameter so t h i s phenomenon i s l i k e l y owing t o the chance c o r r e l a t i o n o f DL/\ w i t h s a l i n i t y ( T a b l e 5 ) , a l t h o u g h some o t h e r e x p l a n a t i o n c a n n o t be r u l e d o u t . 120 100 > O o c CD O k_ 0) CL Floating Submerged Emergent »B8BX 8 F i g . 2 4 . R e l a t i v e p r o p o r t i o n o f f l o a t i n g , submerged and emergent macrophytes i n each l a k e s . Maximum h e i g h t o f b a r s r e p r e s e n t s p e r c e n t o f l a k e a r e a c o v e r e d by a l l m a c r o p h y t e s ; v a r i o u s l y shaded s e c t i o n s r e p r e s e n t p e r c e n t o f l a k e a r e a c o v e r e d by each growth f o r m . (See F i g . 1 f o r l a k e names). 121 T a b l e 1 3 . A q u a t i c macrophyte community p a r a m e t e r s , maximum v a l u e s a r e i n b o l d t y p e . (See F i g . 1 f o r l a k e names; see t e x t e x p l a n a t i o n o f s y m b o l s ) . community parameter Lake s % c o v e r H ' ( s ) H ' ( z ) H ' 7 ( s ) H ' ( f ) H ' f ( s ) Q.i Qri 1 9 45 1 . 6 2 0 . 6 9 0 . 9 3 0.96 0 . 6 6 0 . 3 5 11.39 2 12 89 1.82 0 . 2 2 1.06 0 . 3 6 0 . 9 2 0.46 11.15 3 10 14 1.41 0 . 5 5 0 . 8 6 0 . 5 5 0 . 8 6 0 . 3 9 12.69 4 6 94 1 . 0 0 0 . 3 3 0 . 6 8 0 . 1 2 0 . 8 8 0 . 2 3 12.91 5 6 40 1 . 0 9 0 . 8 3 0 . 2 6 0 . 1 0 0.99 0 . 2 3 13.25 6 3 30 0 . 2 8 0 . 0 1 0 . 2 7 0 . 1 4 0 . 1 4 0 . 1 2 13.95 7 0 0 0 . 0 0 0 . 0 0 0 . 0 0 0 . 0 0 0 . 0 0 0 . 0 0 14.05 8 5 70 1 . 0 5 0.95 0 . 1 0 0 . 4 2 0 . 6 3 0 . 1 9 1 3 . 2 0 T a b l e 14. Summary o f r e l a t i o n s h i p s between p h y s i o c h e m i c a l v a r i a b l e s and a q u a t i c macrophyte community parameters based on P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t . N e g a t i v e a s s o c i a t i o n s : * = p<0.10; * * = p < 0 . 0 5 ; * * * = p < 0 . 0 1 . P o s i t i v e a s s o c i a t i o n s : + = p<0.10; ++ = p < 0 . 0 5 ; +++ = p < 0 . 0 1 . (See t e x t f o r e x p l a n a t i o n o f s y m b o l s ; see Appendix G f o r n u m e r i c a l v a l u e s ) . community parameter s % c o v e r H ' ( s ) H ' ( z ) H ' 7 ( s ) H ' ( f ) H ' f ( s ) Qj Q H ^25 * * * * * * * * " * * * ++ logk25 * - * * * * * * * +++ PQl * • * • * * * * _ * * * ++ PC2 - - - - - - - - -z *** ** ** _ *** _ ** *** +++ Di A ++ ++ + - + ++ * * 122 Of t h e b i o t i c v a r i a b l e s e x a m i n e d , s p e c i e s r i c h n e s s , H ' ( s ) , H ' z ( s ) , Qj and Q j , a l l show s i g n i f i c a n t a s s o c i a t i o n s w i t h w a t e r c h e m i s t r y . When d i v e r s i t y was e x p r e s s e d i n a h i e r a r c h i c a l form t o c o n t r o l f o r m o r p h o l o g i c a l l y d i f f e r e n t b a s i n s h a p e s , i . e . by s u b t r a c t i n g H ' ( z ) from H ' ( s ) , the a s s o c i a t i o n i s much s t r o n g e r . As e x p e c t e d , t h e r e i s no a s s o c i a t i o n between H ' ( z ) and w a t e r c h e m i s t r y . A t r e n d i s i n d i c a t e d f o r d e c r e a s i n g p e r c e n t c o v e r and H ' f ( s ) w i t h i n c r e a s i n g c o n d u c t i v i t y and P C I . CLASSIFICATION. Dendrograms produced by m u l t i v a r i a t e c l a s s i f i c a t i o n o f l a k e s a c c o r d i n g t o t h e i r s p e c i e s c o m p o s i t i o n show an arrangement o f l a k e s c l e a r l y r e l a t e d t o s a l i n i t y ( F i g . 2 5 ) . Both dendrograms have a c c e p t a b l e c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s . In t h e dendrogram based s o l e l y on s p e c i e s p r e s e n c e / a b s e n c e ( F i g . 2 5 a ) , Lake 1 i s l a s t t o j o i n the c l u s t e r owing t o i t s unique f r e s h w a t e r a s s e m b l a g e , and the remainder a r e j o i n e d i n p a i r s o f l a k e s a d j a c e n t t o each o t h e r on the s a l i n i t y s c a l e . When s p e c i e s r e l a t i v e abundances were c o n s i d e r e d ( F i g . 2 5 b ) , s a l i n e Lakes 6 and 7 a r e c o n s i d e r e d l e a s t d i s s i m i l a r and the r e m a i n i n g l a k e s a r e s e q u e n t i a l l y added t o the c l u s t e r , more o r l e s s i n o r d e r o f d e c r e a s i n g s a l i n i t y . A l t h o u g h both dendrograms show p a t t e r n s r e l a t e d t o s a l i n i t y , they a r e n o t c l o s e l y r e l a t e d t o each o t h e r o r t o dendrograms produced from p h y s i o c h e m i c a l d a t a ( F i g . 4) as c o p h e n e t i c c o r r e l a t i o n s between dendrograms a r e not s i g n i f i c a n t . The s i m p l e m a t c h i n g c o e f f i c i e n t was used t o c l u s t e r b i n o m i a l d a t a ( F i g . 25a) as i t i s n o t a l g e b r a i c a l l y p o s s i b l e t o use J a c c a r d ' s c o e f f i c i e n t when a sample (Lake 7) i n t h e s e r i e s has no s p e c i e s . The one a b e r r a t i o n i n F i g . 25b i s the d i s p l a c e m e n t o f Lake 4 , p r o b a b l y owing t o i t s e x t r e m e l y h i g h p e r c e n t c o v e r ( T a b l e 1 3 ) . PRODUCTIVITY. The dominant s p e c i e s , and i n some c a s e s growth f o r m s , 123 F i g . 2 5 . C l u s t e r a n a l y s i s o f study l a k e s based on (a) s i m i l a r i t y o f macrophyte s p e c i e s c o m p o s i t i o n , r=0.899 (b) d i s s i m i l a r i t y o f s p e c i e s r e l a t i v e abundance, r=0.968 (See F i g . 1 f o r l a k e names). 124 8 7 6 5 4 3 Lake o 0.2 0.4 0.6 Similarity _1 L_ 0.8 1.0 ® 8 10 8 6 4 Dissimilarity - 7 - 6 — 5 — 3 — 2 — 1 Lake o ® 125 c o l l e c t e d i n sample q u a d r a t s d i f f e r e d among l a k e s . Samples from l a k e s w i t h c o n d u c t i v i t i e s l e s s than 5000 JJS (Lakes 1-5) were dominated by mats o f f l o a t i n g and/or submerged v e g e t a t i o n : Potamogeton natans i n Lake 1 , M y r i o p h y l l u m e x a l b e s c e n s i n Lake 2 , and a c o m b i n a t i o n o f Potamogeton  p e c t i n a t u s , Ruppia o c c i d e n t a l i s p l u s f i l a m e n t o u s a l g a e i n Lakes 3 , 4 and 5 . The l i t t o r a l zones o f Lakes 6 and 8 had n o , o r v i r t u a l l y n o , submerged v e g e t a t i o n , i n s t e a d they were dominated by the w i d e l y spaced t h i c k emergent stems o f J u n c u s b a l t i c u s . J . b a l t i c u s was p r e s e n t around the f r e s h e r l a k e s , b u t n o t u s u a l l y i n the w a t e r so i t never e n t e r e d the s a m p l i n g a r e a , whereas i n Lakes 6 and 8 i t was p a r t i a l l y submerged a l l s e a s o n . No v e g e t a t i o n was found i n Lake 7 . Macrophytes i n t h e f i r s t f i v e l a k e s e x h i b i t e d t y p i c a l growth c u r v e s : low o r no biomass e a r l y i n t h e s e a s o n , i n c r e a s i n g t o a maximum l e v e l by mid o r l a t e summer, whereas no p a t t e r n was e v i d e n t i n t h e more s a l i n e l a k e s . T h i s i s i l l u s t r a t e d i n F i g . 26 showing t h e s t a n d i n g c r o p o f a q u a t i c macrophytes i n each l a k e i n r e l a t i o n t o t i m e . The d r a m a t i c drop i n biomass o f Lake 3 i n September r e f l e c t s damage done by m u s k r a t s o r w a t e r f o w l . No growth p a t t e r n was e v i d e n t f o r the two more s a l i n e Lakes 6 and 8 owing t o h i g h l y v a r i a b l e d a t a . I t may be t h a t t h e s a m p l i n g t e c h n i q u e used was not s e n s i t i v e enough f o r t h e type o f p l a n t s p r e s e n t i n t h e s e l a k e s . One can s a y , however, t h a t d e s p i t e h i g h v a r i a t i o n , t h e s t a n d i n g c r o p o f Lake 6 was h i g h e r than t h a t o f the more s a l i n e Lake 8 (F=39.49; d f = l , 2 8 ; p < 0 . 0 1 ) . I t i s d i f f i c u l t t o a n a l y z e t h e s e d a t a i n terms o f p r o d u c t i v i t y as t h e dominant macrophyte s p e c i e s d i f f e r e d among l a k e s and s p e c i e s d i f f e r i n t h e i r l i f e c y c l e and biomass d y n a m i c s . In an attempt t o make meaningful c o m p a r i s o n s among l a k e s , the d a t a were r e s c a l e d and p u t on a more even f o o t i n g . F i g . 27 shows s t a n d i n g c r o p v a l u e s o f each l a k e a f t e r d a t a were 126 F i g . 2 6 . Mean and s t a n d a r d e r r o r o f macrophyte s t a n d i n g c r o p i n the l i t t o r a l zone o f each l a k e . ( # ) = l a k e number. Note : no graph shown f o r Lake 7 . (See F i g . 1 f o r l a k e names). Time (days) Time (days) Time (days) 128 F i g . 2 7 . Mean and s t a n d a r d e r r o r , i n s t a n d a r d i z e d u n i t s , o f macrophyte s t a n d i n g c r o p i n t h e l i t t o r a l zone of each l a k e . (T) = l a k e number. Note : no graph shown f o r Lake 7 . (See F i g . 1 f o r l a k e names). 130 c e n t e r e d and s t a n d a r d i z e d by s t a n d a r d d e v i a t i o n ( N o y - M e i r e t a l _ . , 1 9 7 5 ) . Macrophyte p r o d u c t i v i t y shows a s i g n i f i c a n t i n v e r s e a s s o c i a t i o n w i t h c o n d u c t i v i t y , P C I , and mean depth ( T a b l e 1 5 ) . P r o d u c t i v i t y was e s t i m a t e d as t h e d i f f e r e n c e between maximum and minimum s t a n d i n g c r o p when e x p r e s s e d i n s t a n d a r d i z e d u n i t s . P r o d u c t i v i t y measured i n t h i s way has no a b s o l u t e v a l u e , b u t i t does g i v e an i n d i c a t i o n o f r e l a t i v e p r o d u c t i v i t y . I t i s u n r e a l i s t i c t o c a l c u l a t e p r o d u c t i v i t y v a l u e s f o r Lakes 6 o r 8 because the d a t a were so v a r i a b l e t h a t t h e r e was no o b v i o u s s e a s o n a l maximum o r minimum. However, i t i s not u n r e a s o n a b l e t o s u g g e s t t h a t t h e J u n c u s found i n t h e s e l a k e s m a i n t a i n e d a r e l a t i v e l y c o n s t a n t s t a n d i n g c r o p w i t h o u t any a p p r e c i a b l e i n c r e a s e o v e r the s e a s o n , as the r e s u l t s i n d i c a t e , i n which c a s e n e t s e a s o n a l p r o d u c t i v i t y must be z e r o . A g a i n , t h e a s s o c i a t i o n w i t h mean depth i s c o n t r a r y t o p r e d i c t i o n s and p r o b a b l y an i n c i d e n t a l o c c u r r e n c e . Discussion In t h i s s t u d y , s a l i n i t y i s i n v e r s e l y c o r r e l a t e d w i t h a b s o l u t e and r e l a t i v e s p e c i e s r i c h n e s s , abundance, d i v e r s i t y , super community c o m p l e x i t y and p r o d u c t i v i t y o f a q u a t i c m a c r o p h y t e s , t h e r e f o r e s u p p o r t i n g both t h e d i v e r s i t y - s t a b i l i t y and p r o d u c t i v i t y - s a l i n i t y h y p o t h e s e s . The s e r i e s o f e i g h t l a k e s was c h a r a c t e r i z e d a b i o t i c a l l y a c c o r d i n g t o s a l i n i t y t o t e s t t h e s e h y p o t h e s e s , and a c c o r d i n g t o l a k e morphometry t o c o n t r o l f o r p o s s i b l e e f f e c t s o f o t h e r p r o c e s s e s . PROBLEMS. Even though the g e n e r a l c o n c l u s i o n s o f t h i s study a r e v a l i d , t h e r e were a number o f d i f f i c u l t i e s a s s o c i a t e d w i t h the d a t a , as w i t h any o t h e r s t u d y . The main drawback o f the d a t a p r o v i d e d by CWS i s 131 T a b l e 1 5 . A q u a t i c p l a n t p r o d u c t i v i t y measured i n 1984 and i t s r e l a t i o n s h i p t o a b i o t i c v a r i a b l e s , based on P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t . A l l a s s o c i a t i o n s a r e n e g a t i v e : * = p<0.10; * * = p < 0 . 0 5 ; * * * = p < 0 . 0 1 . (See F i g . 1 f o r l a k e names). Lake p r o d u c t i v i t y 1 2 . 0 2 4 2 2.879 3 2 . 6 5 1 4 2 .259 5 2 . 3 0 8 6 0 . 0 7 0 . 0 8 0 . 0 K 2 5 l o g k 2 5 * PCI * * * PC2 z * * * DLA 132 t h a t they r e f l e c t the c o n d i t i o n o f the l a k e s a t o n l y one p o i n t i n t i m e (mid-summer), and a r e not n e c e s s a r i l y r e p r e s e n t a t i v e o f t h e e n t i r e s e a s o n . From my own v i s i t s t o B e c h e r ' s P r a i r i e , i t i s e v i d e n t t h a t macrophyte communities do change d r a m a t i c a l l y o v e r t i m e . I t i s l i k e l y t h a t t h e r e would n o t be l a r g e changes i n s p e c i e s r i c h n e s s b u t t o t a l c o v e r , r e l a t i v e abundance and hence d i v e r s i t y c o u l d change c o n s i d e r a b l y . In a d d i t i o n , t h e r e a r e some weaknesses a s s o c i a t e d w i t h e s t i m a t e s o f abundance on t h e B r a u n - B l a n q u e t s c a l e : p e r c e n t a r e a l c o v e r may be h i g h , b u t dry w e i g h t biomass per u n i t a r e a i s o f t e n s m a l l ( W e s t l a k e , 1963; S c u l t h o r p e , 1 9 6 7 ) , or a l t e r n a t i v e l y , many p l a n t p a r t s such as r o o t s and rhizomes are not v i s u a l l y a p p a r e n t so c o v e r may be u n d e r e s t i m a t e d . G e n e r a l l y s p e a k i n g , the method used t o d e t e r m i n e r e l a t i v e p r o d u c t i v i t y was a p p r o p r i a t e ( W e s t l a k e , 1 9 6 3 ) , b u t some problems a r o s e d u r i n g s a m p l i n g . The dominant p l a n t s p e c i e s , and i n some c a s e s growth f o r m , c o l l e c t e d i n sample q u a d r a t s d i f f e r e d among l a k e s . As a r e s u l t , not a l l l a k e s were sampled w i t h the same degree o f a c c u r a c y , and i t was d i f f i c u l t t o compare l a k e s w i t h o u t r e s c a l i n g t h e d a t a on a somewhat a r b i t r a r y s c a l e . In a d d i t i o n , t h e d a t a do not n e c e s s a r i l y r e p r e s e n t p r o d u c t i v i t y o f the whole l a k e , o n l y o f a s m a l l s t a n d . Many o f t h e s e problems a r e i n s u r m o u n t a b l e b u t one must be aware o f them. N e v e r t h e l e s s , t h e s e methods a r e p r o b a b l y adequate t o r e v e a l r e l a t i v e d i f f e r e n c e s among l a k e s w i t h a degree o f a c c u r a c y s u f f i c i e n t f o r the o b j e c t i v e s o f t h i s s t u d y . DISTRIBUTION AND COMMUNITY COMPOSITION. In t o t a l , 26 a q u a t i c macrophyte s p e c i e s were found i n h a b i t i n g the e i g h t study l a k e s ( T a b l e 1 2 ) , and s p e c i e s c h a r a c t e r i s t i c o f h i g h , low o r moderate s a l i n i t i e s , o r t o l e r a n t o f a l l s a l i n i t i e s , were p r e s e n t i n t h e s e r i e s ( F i g . 2 3 ) . There i s some c o n f l i c t between s e v e r a l o f t h e s p e c i e s names found by CWS and t h o s e 133 p u b l i s h e d p r e v i o u s l y by Reynolds & R e y n o l d s ( 1 9 7 5 ) , b u t t h e s e are m a i n l y taxonomic i d i o s y n c r a c i e s . F o r example: (1) S c i r p u s l a c u s t r i s vs S . v a l i d i u s : t y p i c a l S . l a c u s t r i s i s a E u r a s i a n p l a n t , b u t i n N o r t h America i t i s c o n s i d e r e d a s p e c i e s - c o m p l e x w i t h S . v a l i d u s one o f i t s v a r i a t i o n s ( H i t c h c o c k eit a l _ . , 1 9 6 9 ) . (2) M y r i o p h y l l u m e x a l b e s c e n s vs M. s p i c t a t u m : a c c o r d i n g t o McGaha (1952) t h e s e a r e t h e same s p e c i e s , b u t more r e c e n t l y they have been d e s c r i b e d as v a r i a t i o n s o f the same s p e c i e s ( H i t c h c o c k & C r o n q u i s t , 1 9 7 3 ) . (3) Ruppia o c c i d e n t a l i s vs R. m a r i t i m a : a g a i n , t h e s e a r e c o n s i d e r e d v a r i a t i o n s o f t h e same s p e c i e s ( H i t c h c o c k & C r o n q u i s t , 1 9 7 3 ) . A l m o s t a l l the s p e c i e s a r e c o s m o p o l i t a n o r c i r c u m b o r e a l i n d i s t r i b u t i o n , and many have been noted t o o c c u r i n b r a c k i s h w a t e r ( H i t c h c o c k e t a l . , 1 9 6 9 ) . Macrophyte s p e c i e s d i s t r i b u t i o n s were a p p a r e n t l y d e t e r m i n e d p r i m a r i l y by upper and l o w e r l i m i t s o f t o l e r a n c e t o s a l i n i t y , w h i l e t h e p r e s e n c e o r absence o f a p a r t i c u l a r s p e c i e s w i t h i n t h a t range was owing t o some o t h e r f a c t o r . Each l a k e had a unique s p e c i e s assemblage a n d / o r dominant s p e c i e s , and a l t h o u g h t h e r e was some o v e r l a p , no s p e c i e s o c c u r r e d i n a l l l a k e s and many s p e c i e s o c c u r r e d i n o n l y one l a k e ( T a b l e 1 2 ) . S i m i l a r r e s u l t s were found by Reynolds & Reynolds (1975) i n a study t h a t i n c l u d e d t h e s e e i g h t l a k e s , and by Seddon (1972) i n a s e r i e s o f Welsh l a k e s . O b j e c t i v e , m u l t i v a r i a t e c l a s s i f i c a t i o n methods a r r a n g e d l a k e s i n h i e r a r c h i c a l dendrograms on t h e b a s i s o f t h e i r s p e c i e s c o m p o s i t i o n and r e l a t i v e abundance ( F i g . 2 5 ) . These dendrograms show an arrangement o f l a k e s c l e a r l y r e l a t e d t o s a l i n i t y , b u t n o t the same as p a t t e r n s i n the p h y s i o c h e m i c a l c l u s t e r s ( F i g . 4 ) . The i o n s N a , H C O 3 , C O 3 , CI and K a r e l i k e l y t o be i m p o r t a n t l i m i t i n g f a c t o r s f o r macrophyte s u r v i v a l i n t h e study l a k e s , a l t h o u g h i t 134 was not p o s s i b l e t o d i s t i n g u i s h between the i n f l u e n c e o f t o t a l s a l i n i t y or i n d i v i d u a l i o n s . C h l o r i d e s a l t s a r e c o n s i d e r e d the most t o x i c i o n s t o p l a n t s , and most g l y c o p h y t e s (non s a l t t o l e r a n t p l a n t s ) a r e p h y s i o l o g i c a l l y l i m i t e d a t c o n c e n t r a t i o n s o f NaCl g r e a t e r than 50 mM ( W a i s e l , 1 9 7 2 ) . None o f t h e l a k e s i n t h i s study had CI c o n c e n t r a t i o n s t h i s h i g h ( T a b l e 2) so s p e c i e s d i s t r i b u t i o n s were p r o b a b l y n o t governed s i m p l y t o t h e i n f l u e n c e o f a s i n g l e i o n , b u t r a t h e r t o t o t a l s a l i n i t y o r t h e s y n e r g i s t i c e f f e c t s o f s e v e r a l i o n s . Macrophyte s p e c i e s need not be l i m i t e d o n l y by a p h y s i o l o g i c a l i n t o l e r a n c e t o s a l i n i t y . Other f a c t o r s such as c o m p e t i t i o n may p l a y an i m p o r t a n t r o l e where p l a n t s a r e s u b j e c t t o l e s s than o p t i m a l s a l i n i t i e s . In a d i s c u s s i o n o f t o l e r a n c e ranges i n t h e s e C h i l c o t i n l a k e s as compared t o o t h e r s a l i n e w a t e r b o d i e s , Reynolds & Reynolds (1975) c o n c l u d e d t h a t , a t t h e g l o b a l l e v e l , t h e r e are no c l e a r c o r r e l a t i o n s o f p l a n t d i s t r i b u t i o n w i t h t o t a l c o n d u c t i v i t y as t h e p a r t i c u l a r i o n c o m p o s i t i o n and o t h e r e n v i r o n m e n t a l v a r i a b l e s , such as t e m p e r a t u r e , appear t o be i m p o r t a n t . More i n f o r m a t i o n on the r e l a t i v e s i g n i f i c a n c e o f s a l i n i t y , and a l l i t s a s s o c i a t e d f a c t o r s , t o s p e c i f i c p l a n t s i s n e c e s s a r y b e f o r e s p e c i e s assemblages i n d i f f e r e n t w a t e r s can be f a i r l y compared ( S c u l t h o r p e , 1 9 6 7 ) . However, because t h e s e C h i l c o t i n l a k e s were a b i o t i c a l l y s i m i l a r i n a l m o s t e v e r y r e s p e c t e x c e p t t o t a l s a l i n i t y , i t i s r e a s o n a b l e t o s u g g e s t t h a t w i t h i n t h i s s e r i e s , s a l i n i t y p l a y e d a major r o l e i n l i m i t i n g the d i s t r i b u t i o n o f s p e c i e s . The d i s t r i b u t i o n o f growth forms a l s o appeared t o be a f f e c t e d by s a l i n i t y ( F i g . 2 4 ) : f l o a t i n g - l e a v e d macrophytes were found o n l y i n the two most f r e s h w a t e r l a k e s ( p r i m a r i l y i n Lake 1 ) , the more s a l i n e l a k e s ( o v e r 5000 uS) had v i r t u a l l y no submerged f o r m s , and emergent p l a n t s o c c u r r e d 135 t h r o u g h o u t the range o f s a l i n i t y , but tended t o d e c r e a s e i n abundance w i t h i n c r e a s i n g s a l i n i t y . Brock (1981) s u g g e s t s t h a t more emergent than f l o a t i n g o r submerged macrophytes a r e t o l e r a n t o f s a l i n i t y , y e t o t h e r f a c t o r s such as wind a c t i o n can p r e v e n t p l a n t s w i t h f l o a t i n g l e a v e s from f l o u r i s h i n g ( A r b e r , 1 9 2 0 ) . The f l o a t i n g - l e a v e d Potamogeton natans dominated t h e macrophyte community i n the most f r e s h w a t e r l a k e , b u t t h i s l a k e was a l s o w e l l p r o t e c t e d from p r e v a i l i n g w i n d s , perhaps more so than any o t h e r l a k e i n the s e r i e s . A r b e r (1920) s t a t e s t h e P . natans o f t e n dominates calm w a t e r s , b u t i n l a k e s s u b j e c t t o much wind and wave a c t i o n i t may be o u t - c o m p e t e d by M y r i o p h y l l u m , whose h i g h l y d i v i d e d f o l i a g e i s not so s u s c e p t i b l e t o m e c h a n i c a l damage. As t h i s e x p l a n a t i o n i s i n k e e p i n g w i t h c o n d i t i o n s o b s e r v e d on B e c h e r ' s P r a i r i e , i t i s n o t e n t i r e l y c l e a r i f s a l i n i t y i s the o n l y f a c t o r a f f e c t i n g the d i s t r i b u t i o n o f f l o a t i n g - l e a v e d f o r m s . COMMUNITY PARAMETERS. The r e s u l t s s u p p o r t t h e h y p o t h e s i s t h a t s t a b l e h a b i t a t s have more d i v e r s e communities than l e s s s t a b l e o n e s , where s a l i n i t y d e f i n e s e n v i r o n m e n t a l s t a b i l i t y i n terms o f s e v e r i t y ( T a b l e 1 4 ) . L i t t l e e v i d e n c e was found t o s u p p o r t hypotheses t h a t b a s i n morphometry a f f e c t s community s t r u c t u r e . The i n v e r s e a s s o c i a t i o n o f p l a n t s p e c i e s r i c h n e s s w i t h s a l i n i t y i n d i c a t e s t h a t fewer s p e c i e s were c a p a b l e o f s u r v i v i n g i n h i g h s a l i n i t y l a k e s . S p e c i e s d i v e r s i t y i s i n v e r s e l y c o r r e l a t e d w i t h s a l i n i t y and t h e h i e r a r c h i c a l d i v e r s i t y f o r m u l a ( P i e l o u , 1974; 1975) proved u s e f u l t o c o n t r o l f o r d i f f e r e n c e s i n b a s i n morphology among l a k e s and hence r e v e a l e d an even s t r o n g e r c o r r e l a t i o n . The i n v e r s e a s s o c i a t i o n between the two new super community i n d i c e s and s a l i n i t y i n d i c a t e s t h a t a l t h o u g h s p e c i e s were c a p a b l e o f d i s p e r s i n g t o a l l l a k e s , s a l i n i t y p l a y e d a s i g n i f i c a n t r o l e i n d e t e r m i n i n g which s p e c i e s , how many 136 s p e c i e s , and t h e i r r e l a t i v e abundance, a c t u a l l y e s t a b l i s h e d i n a p a r t i c u l a r l a k e . The g e n e r a l c o m p l e x i t y o f communities d e c r e a s e d w i t h i n c r e a s i n g s a l i n i t y , as compared t o the maximum c o m p l e x i t y p o s s i b l e . PRODUCTIVITY. The d a t a i n t h i s s t u d y i n d i c a t e t h a t i n c r e a s i n g s a l i n i t y , was accompanied by an o v e r a l l d e c r e a s e i n l a k e p r o d u c t i v i t y ( T a b l e 1 5 ) . F r e s h w a t e r l a k e s d i s p l a y e d l a r g e r changes i n macrophyte s t a n d i n g c r o p biomass than s a l i n e l a k e s . The o b s e r v e d d e c r e a s e i n p e r c e n t c o v e r o f a q u a t i c macrophytes w i t h i n c r e a s i n g s a l i n i t y a l s o i n d i c a t e s d e c r e a s i n g e u t r o p h i c a t i o n ( W e s t l a k e , 1963; 1965; McNaught, 1975; W e t z e l , 1975; C a n f i e l d et , 1 9 8 3 ) . In a d d i t i o n , t h e absence o f a l g a l blooms and macrophyte growth i n more s a l i n e l a k e s i n d i c a t e s t h e i r poor t r o p h i c s t a t e as Gannon & Stemberger (1978) s u g g e s t . Summary T h i s t h i r d c h a p t e r examines r e l a t i o n s h i p s between s a l i n i t y and t h e a q u a t i c macrophyte community i n terms o f the d i v e r s i t y - s t a b i l i t y h y p o t h e s i s and a p r o d u c t i v i t y - s t a b i l i t y h y p o t h e s i s . In t o t a l , 26 s p e c i e s were found and s p e c i e s were c h a r a c t e r i s t i c o f h i g h (>5000 u S ) , moderate o r low s a l i n i t i e s , o r t o l e r a n t o f a l l s a l i n i t i e s . S p e c i e s d i s t r i b u t i o n was a p p a r e n t l y d e t e r m i n e d p r i m a r i l y by upper and l o w e r l i m i t s o f t o l e r a n c e t o s a l i n i t y , w h i l e the p r e s e n c e o r absence o f a p a r t i c u l a r s p e c i e s w i t h i n t h a t range was owing t o some o t h e r f a c t o r . The d i s t r i b u t i o n o f growth forms may be a f f e c t e d by s a l i n i t y as f l o a t i n g l e a v e d forms o c c u r r e d o n l y i n f r e s h w a t e r l a k e s , v i r t u a l l y no submerged forms o c c u r r e d i n s a l i n e l a k e s , and emergent forms were found t h r o u g h o u t b u t tended t o d e c r e a s e i n abundance w i t h i n c r e a s e d s a l i n i t y . Each l a k e was c h a r a c t e r i z e d a b i o t i c a l l y 137 a c c o r d i n g t o s a l i n i t y a n d b a s i n m o r p h o m e t r y , a n d b i o t i c a l l y a c c o r d i n g t o m a c r o p h y t e s p e c i e s r i c h n e s s , a b u n d a n c e , d i v e r s i t y , h i e r a r c h i c a l d i v e r s i t y , s u p e r c o m m u n i t y i n d i c e s a n d p r o d u c t i v i t y . S a l i n i t y a p p e a r e d t o be t h e m o s t i m p o r t a n t a b i o t i c f a c t o r i n a s s o c i a t i o n w i t h c o m m u n i t y p a r a m e t e r s , a n d l i t t l e e v i d e n c e was f o u n d o f m o r p h o m e t r i c c o r r e l a t i o n s . I n v e r s e a s s o c i a t i o n s o f s a l i n i t y w i t h a b s o l u t e a n d r e l a t i v e s p e c i e s r i c h n e s s , d i v e r s i t y , h i e r a r c h i c a l d i v e r s i t y a n d s u p e r c o m m u n i t y i n d i c e s , s u p p o r t t h e h y p o t h e s i s t h a t s a l i n e e n v i r o n m e n t s h a v e l e s s d i v e r s e c o m m u n i t i e s t h a n f r e s h w a t e r o n e s . I n v e r s e a s s o c i a t i o n s o f s a l i n i t y w i t h p r o d u c t i v i t y i n t e r m s o f s e a s o n a l b i o m a s s c h a n g e s a n d p e r c e n t v e g e t a t i o n c o v e r , s u p p o r t t h e h y p o t h e s i s t h a t s a l i n e h a b i t a t s h a v e l e s s p r o d u c t i v e m a c r o p h y t e c o m m u n i t i e s t h a n f r e s h w a t e r o n e s . 138 CHAPTER 4: RELATIONSHIPS BETWEEN FAUNAL AND FLORAL COMMUNITIES Introduction S e v e r a l s t u d i e s e x a m i n i n g the fauna o f s a l i n e l a k e s e r i e s have acknowledged the need t o i n t e r p r e t the o b s e r v e d s t r u c t u r e o f animal communities i n terms o f t h e p l a n t community as w e l l as s a l i n i t y ( R e y n o l d s & R e y n o l d s , 1975; Cannings e t a l _ . , 1980; Timms, 1981; Brock & S h i e l , 1983; van V i e r s s e n & V e r h o e v e n , 1 9 8 3 ; Cannings & C a n n i n g s , 1 9 8 5 ) . E v i d e n c e p r e s e n t e d i n C h a p t e r 2 showed t h a t t h e r e i s a r e l a t i o n s h i p between s a l i n i t y and t h e s t r u c t u r e o f f a u n a l c o m m u n i t i e s , b u t t h e n a t u r e o f t h e a s s o c i a t i o n i s q u i t e c o m p l e x . I t may be p o s s i b l e t o r e s o l v e some o f t h i s c o m p l e x i t y by comparing t h e s t r u c t u r e o f f a u n a l communities ( C h a p t e r 2) w i t h t h e f l o r a l communities ( C h a p t e r 3) p r e s e n t i n t h e study l a k e s . A q u a t i c macrophytes p l a y many v a r i e d and i n t e r r e l a t e d r o l e s i n a q u a t i c ecosystems and t h e i r i n f l u e n c e can d i r e c t l y o r i n d i r e c t l y a f f e c t t h e l i v e s o f o t h e r o r g a n i s m s . P l a n t s a r e c a p a b l e o f a l t e r i n g t h e p h y s i c a l and c h e m i c a l e n v i r o n m e n t , t h e r e b y i n d i r e c t l y i n f l u e n c i n g t h e d i s t r i b u t i o n and s u r v i v a l o f t h e f a u n a . P h y s i c a l l y they can a l t e r l i g h t p e n e t r a t i o n , wave a c t i o n , c u r r e n t v e l o c i t y and d i r e c t i o n , and r a t e o f s i l t i n g , t h e l a t t e r two b e i n g more i m p o r t a n t i n r u n n i n g w a t e r than l a k e s . Macrophyte s h a d i n g can i n h i b i t p h y t o p l a n k t o n development ( G o u l d e r , 1 9 6 9 ) , and a l t e r l o c a l d i s t r i b u t i o n s o f p h o t o t a x i c i n s e c t s (Lyman, 1956; Hughes, 1966; Hynes, 1970) and l i m n e t i c z o o p l a n k t o n ( S i e b e c k & R i n g e l b e r g , 1 9 6 9 ) . Through the m e t a b o l i c p r o c e s s e s o f p h o t o s y n t h e s i s and r e s p i r a t i o n , macrophytes can a f f e c t c o n c e n t r a t i o n s o f d i s s o l v e d O 2 , CO2 and N H 4 , m i n e r a l n u t r i e n t s , and pH ( S t r a s k r a b r a , 1965; S c u l t h o r p e , 1967; W e t z e l , 1 9 7 5 ) . A q u a t i c p l a n t s s e c r e t e d i s s o l v e d o r g a n i c compounds ( W e t z e l , 1969; Wetzel & 139 Manny, 1972; Hough & W e t z e l , 1975) t h a t can enhance p e r i p h y t o n p r o d u c t i v i t y ( W e t z e l , 1975) o r a c t as r e p e l l e n t s o r a t t r a c t a n t s t o c e r t a i n a n i m a l s (Pennak, 1973; H u t c h i n s o n , 1975; L l o y d , 1 9 7 6 ) . More d i r e c t l y , macrophytes p r o v i d e a s u b s t r a t e f o r a n i m a l s t o c o l o n i z e , l a y e g g s , p u p a t e , seek r e f u g e , hunt f o r f o o d , and use as b u i l d i n g m a t e r i a l s ( M i n s h a l l , 1 9 8 4 ) . The use o f s u b s t r a t e changes t h r o u g h o u t the a n i m a l s ' l i f e c y c l e , and the degree o f dependence v a r i e s from o b l i g a t e t o f a c u l t a t i v e ( S o s z k a , 1975b). Many i n s e c t s o v i p o s i t i n o r on macrophytes b u t d i f f e r i n the e x t e n t o f t h e i r dependence: c o r i x i d s f r e q u e n t l y o v i p o s i t on p l a n t s ( H u n g e r f o r d , 1 9 4 8 ) ; some Odonata d e p o s i t eggs among t h i c k v e g e t a t i o n ( W o l f e , 1953) w h i l s t t h o s e w i t h o v i p o s i t o r s l a y eggs w i t h i n p l a n t t i s s u e s ( C o r b e t , 1962; Cannings & S t u a r t , 1977); c h r y s o m e l i d s o f t h e D o n a c i i n a e o v i p o s i t and pupate w i t h i n p l a n t t i s s u e s ( H o u l i h a n , 1969; 1970; C r o w s o n , 1981; O t t o , 1985) whereas some a q u a t i c w e e v i l s complete t h e i r l i f e c y c l e from egg t o a d u l t w i t h i n p l a n t t i s s u e s (McGaha, 1954a; G a e v s k a y a , 1966; DeLoach e t j i K , 1976; Cordo e t ^ [ . , 1978; 1981; 1982; Forno e t a l _ . , 1 9 8 3 ) . S i m i l a r l y , t h e T r i c h o p t e r a and P y r a l i d a e b u i l d p r o t e c t i v e c a s e s w i t h p l a n t m a t e r i a l (McGaha, 1954b) whereas some c r u s t a c e a n s s i m p l y h i d e among l i t t o r a l v e g e t a t i o n t o a v o i d p r e d a t i o n ( D a v i e s , 1 9 8 5 ) . The l a c u n a l system o f some a q u a t i c p l a n t s can even be used as an oxygen s o u r c e f o r i n s e c t r e s p i r a t i o n ( H o u l i h a n , 1969; 1970; O t t o , 1 9 8 5 ) . A q u a t i c macrophytes can e n t e r t h e t r o p h i c system i n d i r e c t l y as a s u b s t r a t e f o r p e r i p h y t o n communities which many h e r b i v o r e s g r a z e u p o n , o r as a d i r e c t f o o d s o u r c e . A major p a r t o f the t o t a l p r i m a r y p r o d u c t i o n i n a l a k e o c c u r s i n t h e l i t t o r a l v e g e t a t i o n where p e r i p h y t o n grows on t h e macrophytes ( W e s t l a k e , 1963; 1965; McNaught, 1975; C a n f i e l d , e t a l _ . , 1 9 8 3 ) . The a q u a t i c fauna f e e d i n g d i r e c t l y on p l a n t s c o n s i s t o f o b l i g a t e 140 phytophages such as w e e v i l s (McGaha, 1954a; G a e v s k a y a , 1966; DeLoach e t a l _ . , 1976; Cordo e t ^ L , 1978; 1981; 1982; Forno e t a l _ . , 1 9 8 3 ) , D o n a c i i n a e (Crowson, 1981; O t t o , 1 9 8 5 ) , P y r a l i d a e (McGaha, 1954b; Hynes, 1 9 8 4 ) , some c h i r o n o m i d s and e p h y d r i d s ( B e r g , 1949; M i n s h a l l , 1 9 8 4 ) , and f a c u l t a t i v e phytophages such as c o r i x i d s ( R e y n o l d s , 1 9 7 5 ) , some D y t i s c i d a e ( G a e v s k a y a , 1 9 6 6 ) , and amphipods ( S t r o i k i n a , 1957 c i t e d by G a e v s k a y a , 1 9 6 6 ) . Some a q u a t i c p l a n t s a r e t h e m s e l v e s c a r n i v o r e s ( L l o y d , 1976; M e y e r s , 1 9 8 2 ) . These s p e c i f i c p l a n t - a n i m a l r e l a t i o n s h i p s a r e v e r y complex and many o f them are i n t e r r e l a t e d t o form a network o f r e l a t i o n s h i p s , each o f which can i n f l u e n c e many o t h e r s . I t i s v i r t u a l l y i m p o s s i b l e t o examine any one community f o r a l l t h e s e f a c t o r s and t h i s study does not a t t e m p t t o , b u t the sum o f a l l i n d i v i d u a l p l a n t - a n i m a l i n t e r a c t i o n s can be summarized a t an e c o l o g i c a l l e v e l . Many e c o l o g i c a l s t u d i e s have shown d i s t i n c t a s s o c i a t i o n s between a q u a t i c p l a n t and animal communities (Macan, 1938; K r e c k e r , 1939; B e r g , 1949; McGaha, 1952; S m y l y , 1952; 1953; R o s i n e , 1955; G e r k i n g , 1957; S m y l y , 1957; H a r r o d , 1964; S t r a s k r a b a , 1965; W h i t e s i d e & Harmsworth, 1967; P e t r , 1968; Quade, 1969; K r u l l , 1970; S o s z k a , 1975a; 1975b; S h i e l , 1976; F r y & O s b o r n e , 1980; P a l m e r , 1981; Brock & S h i e l , 1983; van V i e r s s e n & V e r h o e v e n , 1983; B l a n c h e r , 1984; M i n s h a l l , 1984; R i c h a r d et a K , 1 9 8 5 ) . R e s u l t s o f t h e s e s t u d i e s o v e r l a p a g r e a t d e a l , t h e r e f o r e , g e n e r a l i z e d r e l a t i o n s h i p s a r e summarized below w i t h o u t s p e c i f i c r e f e r e n c e s . The d i s t r i b u t i o n o f macrophyte s p e c i e s and growth forms i s i m p o r t a n t to animal communities as d i f f e r e n t p l a n t s a r e a s s o c i a t e d w i t h d i f f e r e n t animal s p e c i e s and/or d e n s i t i e s . E v i d e n c e i n d i c a t e s t h a t t h e number and v a r i e t y o f a n i m a l s a s s o c i a t e d w i t h macrophytes are c o r r e l a t e d w i t h t h e m o r p h o l o g i c a l form o f the p l a n t s : p l a n t s w i t h f i n e l y d i v i d e d l e a v e s p o s s e s s l a r g e r and more 141 v a r i e d animal p o p u l a t i o n s than t h o s e w i t h s i m p l e , e n t i r e l e a v e s . The abundance a n d / o r p r o d u c t i v i t y o f a q u a t i c macrophytes i n a l a k e has been shown t o a f f e c t the c o m p o s i t i o n , abundance, r i c h n e s s and d i v e r s i t y o f animal c o m m u n i t i e s . With l a r g e r a r e a s o f p l a n t c o v e r and/or more p r o d u c t i v e c o m m u n i t i e s , p l a n t s have more i n f l u e n c e on a l l p h y s i c a l , c h e m i c a l and b i o l o g i c a l p r o c e s s e s t a k i n g p l a c e i n t h e l a k e . I t has been found t h a t more s p e c i e s r i c h o r d i v e r s e f l o r a l assemblages s u p p o r t more s p e c i e s r i c h o r d i v e r s e f a u n a l a s s e m b l a g e s , and presumably t h e s e phenomena a r e r e l a t e d t o a s p e c t s o f s p a t i a l and s u b s t r a t e h e t e r o g e n e i t y . In a d d i t i o n , a c o n t a g i o u s ( p a t c h y ) d i s t r i b u t i o n o f a n i m a l s i s a common f e a t u r e o f a q u a t i c (and t e r r e s t r i a l ) h a b i t a t s and p r o b a b l y f r e q u e n t l y i s a r e s u l t o f a patchy d i s t r i b u t i o n o f p l a n t s i n t h e e n v i r o n m e n t . T e s t s f o r e c o l o g i c a l r e l a t i o n s h i p s between f l o r a l and f a u n a l communities a r e Group 2 t y p e hypotheses o f t h e d i v e r s i t y - s t a b i l i t y c o n c e p t (see General I n t r o d u c t i o n ) . S p e c i f i c a l l y , they t e s t t h e h y p o t h e s i s t h a t more a b u n d a n t , r i c h and d i v e r s e p l a n t communities s u p p o r t more abundant , r i c h and d i v e r s e animal c o m m u n i t i e s . T h i s h y p o t h e s i s was t e s t e d w i t h the f a u n a l and f l o r a l communities i n t h e B e c h e r ' s P r a i r i e study l a k e s . Any p a t t e r n s r e v e a l e d t h r o u g h t h i s a n a l y s i s may h e l p e x p l a i n o b s e r v e d p a t t e r n s between f a u n a l communities and s a l i n i t y ( C h a p t e r 2 ) . Materials and Methods S p e c i e s d i s t r i b u t i o n p a t t e r n s , community parameters and dendrograms, o f f a u n a l and f l o r a l communities p r e s e n t e d i n C h a p t e r s 2 and 3 , were compared. Numerical parameters were s t a t i s t i c a l l y compared u s i n g P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t , and dendrograms were compared w i t h 142 c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s (see p r e v i o u s c h a p t e r s f o r d e t a i l s ) . A l l a s s o c i a t i o n s between p l a n t and animal communities were f u r t h e r summarized w i t h r e f e r e n c e t o t h e i r r e l a t i o n s h i p w i t h s a l i n i t y . No new d a t a a r e p r e s e n t e d . Results T a b l e 16 summarizes t h e a s s o c i a t i o n s between f l o r a l and f a u n a l community p a r a m e t e r s , and T a b l e 17 i l l u s t r a t e s how f a u n a l community parameters r e l a t e t o both macrophyte communities and s a l i n i t y . The s i g n ( p o s i t i v e o r n e g a t i v e ) o f a l l c o r r e l a t i o n s and t r e n d s i n T a b l e 16 i n d i c a t e t h a t more d i v e r s e p l a n t communities a r e a s s o c i a t e d w i t h more d i v e r s e animal c o m m u n i t i e s , w i t h one e x c e p t i o n . T r o p h i c l e v e l d i v e r s i t y [ H ' ( t ) ] o f e n t o m o s t r a c a n s c a u g h t i n l i g h t t r a p s shows an i n v e r s e c o r r e l a t i o n w i t h f l o r a l community p a r a m e t e r s . T h i s parameter was r e j e c t e d i n C h a p t e r 2 as b e i n g b i a s e d by s a m p l i n g t e c h n i q u e and hence not r e p r e s e n t a t i v e o f t h e t r u e community, t h e r e f o r e , t h i s i n v e r s e a s s o c i a t i o n i s i g n o r e d and t h e parameter i s n o t i n c l u d e d i n T a b l e 17. The p l a n t community parameter H ' ( z ) i s n o t c o r r e l a t e d w i t h any f a u n a l parameters ( T a b l e 16) and a l s o has been o m i t t e d from T a b l e 17. T h i s parameter i s r e p r e s e n t a t i v e o f the a b i o t i c environment r a t h e r than o f macrophyte community s t r u c t u r e , and was used i n the h i e r a r c h i c a l d i v e r s i t y f o r m u l a t o remove the c o n f o u n d i n g e f f e c t s o f b a s i n morphometry from measures o f macrophyte s p e c i e s d i v e r s i t y ( C h a p t e r 3 ) . T a b l e 18 p r e s e n t s c o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l and f l o r a l dendrograms, and i l l u s t r a t e s how f a u n a l community dendrograms r e l a t e t o both macrophytes and s a l i n i t y . In both w a t e r b o t t l e and l i g h t t r a p samples o f z o o p l a n k t o n 143 T a b l e 1 6 . Summary o f r e l a t i o n s h i p s between f l o r a l and f a u n a l community p a r a m e t e r s based on P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t . N e g a t i v e a s s o c i a t i o n s : * = p<0.10; * * = p < 0 . 0 5 ; * = p < 0 . 0 1 ; p o s i t i v e a s s o c i a t i o n s : + = p<0.10; ++ = p<0.05; +++ = p < 0 . 0 1 ; - = no a s s o c i a t i o n . See T a b l e 6 f o r d e s c r i p t i o n o f s y m b o l s . See Appendix H f o r n u m e r i c a l v a l u e s . P l a n t Community F a u n a l Community p a r a m e t e r P a r a m e t e r D s t i H ' ( s ) H ' ( t ) H ' ( t i ) H ' t ( s ) H ' t ( i ) H ' t 1 ( s ) Q j ( s ) Q j ( t i ) Q d ( s ) Q d ( t i ) WATER BOTTLE - ZOOPLANKTON c - + + + + + + - + + + - + + - - . . H ' ( s ) - + - - + . - - . + - , . H ' ( z ) -H ' z ( s ) - + - - + + - - - . + . . . H ' ( f ) H ' f ( s ) + ++ ++ - - - + ++ Qj -Q d - * - - * . - . . * . . . P - + + + - + + + - - - - + + + + - -SWEEP - COLEOPTERA s + + - + - - _ - _ _ _ + * * c + + - - - - . _ _ . . _ . * H ' ( s ) + - + . . . _ . . . + * * H ' ( z ) -H ' 2 ( s ) + - - - - - - _ _ _ _ _ _ H ' ( f ) H ' f ( s ) -Qj + + - + - - _ • - _ _ _ + * * Qd * * . _ . + . + SWEEP - HEMIPTERA s - ++ + + ++ _ + + + * * c - * _ - . * H ' ( s ) - + + ++ ++ _ + + * * H ' ( z ) - - - - . H ' z ( s ) ++ + ++ _ + + + * * H ' ( f ) - - - ++ - - - - * . H ' f ( s ) - - + - + . . + . * Qj - ++ + + ++ ++ + * Qd - * * * * * * * * ++ ++ P - + + - ++ * * + + . . *** 144 Table 16. CONT Pla n t Community Faunal Community parameter Parameter 0 s t i H'(s) H'(t) H ' ( t i ) H' t(s) H ' t ( i ) H ' t i ( s ) Qj(s) Q j ( t i ) Qd(s) Qd(ti) LIGHT TRAP - ALL SPECIES s + + - - - + + - -c - ++ - _ - - - - -H'(s) + + - - - + + * -H'(z) - - + - - - - -H' z(s) - ++ - - - ++ ++ * H'(f) ++ - ++ _ - ++ - ** -H'f(s) - - - - - - - - - -Qj + + - - - + + - -Od *** ** * - *** ** ++ -P - ++ - - - - ++ - -LIGHT TRAP - ENTOMOSTRACA s ++ + *** - ++ + - -c ++ - ++ + - + + - -H'(S) + + ** - - + + - -H'(z) - - - - - - - - -H'Z(S) - +++ + *** - +++ - -H'(f) - - - . . . - - - - -H' f(s) - + ++ ** . . . - + ++ - -Qj ++ + _ - ++ + - -Od * - + - - * * - -P ++ ++ *** - - ++ ++ - -LIGHT TRAP - COLEOPTERA s - - + _ - - - - * c - - - - - - - -H'(s) - - • + - - - - - * H'(z) - - - - - - - -H' z(s) - + + + + + -H'{f) + - + + + + - ** -H'f(s) - - - + _ - - - - -Qj - - + - - - - - * Qd ** ** - *** ** ** ++ p - - ++ - - - - - * LIGHT TRAP - HEMIPTERA s ++ ++ - +++ - ++ ++ ** -c ++ + - + - - - ** -H'(s) ++ - +++ - ++ + * -H'(z) - - - - - - - - -H' z(s) - +++ - +++ - +++ * -H'(f) - - - - - - - - -H'f(s) - - ++ - ++ *** - ++ ** * Qj ++ ++ - +++ - ++ ++ -Qd *** * - *** - *** * + -p + +++ _ +++ *** + +++ * -145 T a b l e 17. Summary o f r e l a t i o n s h i p s between f l o r a l and f a u n a l community parameters and s a l i n i t y , t = both f a u n a l and f l o r a l parameters a s s o c i a t e d w i t h s a l i n i t y and each o t h e r ; • = f a u n a l parameter a s s o c i a t e d w i t h f l o r a b u t not s a l i n i t y ; 0 = fauna a s s o c i a t e d w i t h s a l i n i t y b u t not f l o r a ; - = no a s s o c i a t i o n s . See T a b l e 6 f o r d e s c r i p t i o n o f p a r a m e t e r s . P l a n t C o m m u n i t y F a u n a l C o m m u n i t y p a r a m e t e r P a r a m e t e r D s t i H ' ( s ) H ' ( t ) H ' ( t i ) H ' t ( s ) H ' t ( i ) H ' t i ( s ) Q j ( s ) Q j ( t i ) Q d ( s ) Q d ( t i ) WATER B O T T L E - Z O O P L A N K T O N s - 0 0 - t - 0 0 0 -c - t t 1 0 1 • • 0 0 0 -H'(S) - t 0 - t - t 0 0 -H ' z ( s ) - t 0 - t - t 0 0 -H ' ( f ) - 0 0 - 0 - 0 0 0 -H ' f ( s ) - t t - t - t t 0 -Q j - 0 0 - t _ - 0 0 0 -Q d - t 0 - t - • t 0 0 -p - t t - t - - t t 0 -SWEEP - C O L E O P T E R A s • - I - - - - 1 I 1 c I - - - - - - - - - I H ' ( s ) 1 - 1 - - - - 1 1 1 H ' z ( s ) • - - - - - - - - -H ' ( f ) - - - - - - - - - -H ' f ( s ) - - - - - - - - - -Oj I - 1 - - - - - I 1 I Q d 1 - - - - - • - - - 1 I P - - - - - - - - - - -SWEEP - H E M I P T E R A s 0 t t t t 0 t t t 1 c 0 0 0 0 0 t 0 0 0 I H ' ( s ) 0 t t t t 0 t t t 1 H ' z ( s ) 0 t t 0 t 0 t t t I H ' ( f ) 0 0 0 t 0 0 0 0 t -H ' f ( s ) 0 0 t 0 t 0 0 t 0 1 Q j 0 t t t t 0 t t t I Q d 0 t 0 t t 0 t 0 t I P 0 t t 0 t t t t 0 -146 Table 17. CONT. Plant Community Faunal Community parameter Parameter D s t i H'(s) H'(t) H'(ti) H't(s) H' t(i) H' t i(s) Qj(s) Qj(ti)Qd(s) Qd(ti) LIGHT TRAP - ALL SPECIES s - t t - 0 - - t t 0 0 c - 0 t - 0 - - 0 0 0 0 H'(S) - t t - 0 - - t t t 0 H'z(s) - t t - 0 - - t t t 0 H'(f) - t 0 - t - - t 0 t - 0 H'f(s) - 0 0 - 0 - - 0 0 0 0 Qj - t t - 0 - - t t 0 0 Od - t t - t - - t t t 0 p - 0 t - 0 - - 0 t 0 0 LIGHT TRAP - ENTOMOSTRACA s - t t - - - - t t - -c - t t - - 1 I - t t - -H'(s) - t t - - - - t t - -H'Z(S) - t t - - - - t t - -H'(f) - 0 0 - - - - 0 0 - -H'fts) - t t - - - - t t - -Qj - t t - - - - t t - -Od - t 0 - - - - t t - -p - t t - - - - t t - -LIGHT TRAP - COLEOPTERA s 0 0 0 0 t 0 0 0 0 0 0 0 t c 0 0 0 0 0 0 0 0 0 0 0 0 0 H'(S) 0 0 0 0 t 0 0 0 0 0 0 0 t H' z(s) 0 t t t t 0 0 0 t t t 0 t H'(f) 0 t 0 t 0 t 0 0 t t 0 t 0 H'f(s) 0 0 0 0 t 0 0 0 0 0 0 0 0 Qj 0 0 0 0 t 0 0 0 0 0 0 0 t Qd 0 t t 0 0 0 0 0 t t t t t p 0 0 0 0 t 0 0 0 0 0 0 0 t LIGHT TRAP - HEMIPTERA • s 0 t t - t 0 t t 1 -c 0 t t - t 0 0 0 I -H'(s) 0 t t - t 0 t t 1 -H' Z(S) 0 t t - t 0 t t 1 -H'(f) 0 0 0 - 0 0 0 0 - -H'f(s) 0 0 t - t t 0 t I 1 Qj 0 t t - t 0 t t 1 -Qd 0 t t - t 0 t t 1 -p 0 t t - t t t t 1 -147 T a b l e 1 8 . C o p h e n e t i c c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l and f l o r a l dendrograms, and t h e i r r e l a t i o n s h i p w i t h s a l i n i t y . * i n d i c a t e s s i g n i f i c a n t r e l a t i o n s h i p s ; o t h e r symbols are as i n T a b l e 17. N . B . F i g s . 17d, 18b and 19c a r e o m i t t e d , see t e x t f o r e x p l a n a t i o n . Faunal Dendrogram F l o r a l dendrogram p r e s e n c e / a b s e n c e r e l a t i v e abundance F i g . 24a F i g . 24b WATER BOTTLE Z o o p l a n k t o n F i g . 14a 0 . 1 6 2 0 F i g . 14b 0 . 0 4 9 0 F i g . 14c 0 . 5 0 5 -F i g . 14d 0.114 -LIGHT TRAPS Entomostraca F i g . 15a 0.130 0 F i g . 15b 0 . 2 0 9 -F i g . 15c 0 . 0 0 5 F i g . 15d 0.147 -A l l s p e c i e s F i g . 16a 0 . 0 3 4 F i g . 16b 0 . 1 6 6 0 F i g . 16c 0 . 8 0 4 * • F i g . 16d 0 . 5 4 9 -C o l e o p t e r a F i g . 17a 0 . 0 3 3 -F i g . 17b 0 . 2 0 4 -F i g . 17c 0 . 8 2 5 * 1 Hemiptera F i g . 19a 0 . 0 7 0 0 F i g . 19b 0.257 -F i g . 19d 0 . 2 0 1 -SWEEP SAMPLES C o l e o p t e r a F i g . 18a 0 . 4 5 1 -F i g . 18c 0 . 6 8 1 -F i g . 18d 0 . 4 0 9 -Hemiptera F i g . 20a 0 . 1 3 9 -F i g . 20b 0 . 3 0 3 -F i g . 20c 0.514 -F i g . 20d 0 . 0 9 8 -0.087 0.007 0 . 5 4 8 0.227 0.107 0 . 2 3 5 0 . 2 0 6 0.087 0 . 0 8 6 0 . 1 5 9 0.777-0 . 5 8 8 0 . 2 2 9 0 . 0 4 1 0.772-0 . 0 5 6 0 . 3 3 9 0 . 0 4 6 0 . 2 9 2 0.775 0.721 0.114 0 . 3 8 9 0.576 0 . 1 8 4 0 0 0 0 0 0 148 c o m m u n i t i e s , v i r t u a l l y a l l f a u n a l community parameters t h a t a r e c o r r e l a t e d w i t h s a l i n i t y a r e a l s o c o r r e l a t e d w i t h s e v e r a l p l a n t community p a r a m e t e r s , namely s , t i , H ' ( t ) , Qj(s) and Q j ( t i ) ( T a b l e 1 7 ) . Only the super community i n d e x Qrj(s) i n t h e l i m n e t i c samples i s a s s o c i a t e d w i t h s a l i n i t y and n o t t h e f l o r a l community. A d d i t i o n a l l y , v a r i o u s measures o f z o o p l a n k t o n d i v e r s i t y [ H ' ( s ) , H ' ( t ) , H ' t ( s ) , H ' t i ( s ) , H ' t ( i ) ] a r e a s s o c i a t e d w i t h t h e amount o f a q u a t i c p l a n t c o v e r , b u t not s a l i n i t y . As shown i n T a b l e 1 8 , c l u s t e r diagrams o f l a k e s based on z o o p l a n k t o n communities a r e n o t s i g n i f i c a n t l y c o r r e l a t e d w i t h t h o s e based on m a c r o p h y t e s , b u t t h o s e based on t h e p r e s e n c e o r absence o f z o o p l a n k t o n s p e c i e s o r e c o l o g i c a l c a t e g o r i e s a r e c o r r e l a t e d w i t h s a l i n i t y . When a l l s p e c i e s i n l i g h t t r a p samples were c o n s i d e r e d , v i r t u a l l y a l l f a u n a l community parameters t h a t a r e c o r r e l a t e d w i t h s a l i n i t y [ s , t i , H ' ( t ) , Q j ( s ) , Q j ( t i ) , Qrj(s)] a r e a l s o c o r r e l a t e d w i t h s e v e r a l p l a n t community parameters ( T a b l e 1 7 ) . Only t h e super community i n d e x Qd ( t i ) i s c o r r e l a t e d w i t h s a l i n i t y and not p l a n t s . The c l u s t e r diagram o f animal s p e c i e s abundance i s s i g n i f i c a n t l y c o r r e l a t e d w i t h t h e one based on t h e p r e s e n c e o r absence o f a q u a t i c p l a n t s p e c i e s , b u t no o t h e r s a r e a s s o c i a t e d ( T a b l e 1 8 ) . L i g h t t r a p and sweep n e t samples o f C o l e o p t e r a p r e s e n t q u i t e d i f f e r e n t p a t t e r n s o f a s s o c i a t i o n w i t h macrophyte communities and s a l i n i t y . T a b l e 17 shows t h a t parameters c a l c u l a t e d f o r b e e t l e communities sampled i n l i g h t t r a p s a r e a l l a s s o c i a t e d w i t h s a l i n i t y , and s e v e r a l show p o s i t i v e t r e n d s w i t h p l a n t community p a r a m e t e r s . The d e n s i t y o f C o l e o p t e r a caught i n l i g h t t r a p s i s c o r r e l a t e d w i t h s a l i n i t y but not w i t h any a s p e c t s o f the macrophyte community. Only the dendrogram based on C o l e o p t e r a s p e c i e s p r e s e n c e o r absence i s c o r r e l a t e d w i t h t h e p l a n t community, and none are 149 c o r r e l a t e d w i t h s a l i n i t y ( T a b l e 1 8 ) . Community parameters c a l c u l a t e d from sweep n e t samples o f a q u a t i c b e e t l e s show no c o r r e l a t i o n s w i t h s a l i n i t y , but s e v e r a l parameters a r e a s s o c i a t e d w i t h macrophyte community parameters ( T a b l e 1 7 ) . S p e c i f i c a l l y , t h e d e n s i t y , r i c h n e s s , and d i v e r s i t y o f p l a n t communities a r e p o s i t i v e l y a s s o c i a t e d w i t h the d e n s i t y , a b s o l u t e and r e l a t i v e number o f e c o l o g i c a l c a t e g o r i e s , and super community c o m p l e x i t y measures o f c o l e o p t e r a n c o m m u n i t i e s . Dendrograms drawn from sweep n e t C o l e o p t e r a a r e n o t c o r r e l a t e d w i t h t h o s e drawn from macrophyte assemblages o r p h y s i o c h e m i c a l p r o p e r t i e s ( T a b l e 1 8 ) . H e m i p t e r a communities c o l l e c t e d i n sweep n e t s and l i g h t t r a p s show s i m i l a r p a t t e r n s o f a s s o c i a t i o n w i t h macrophyte communities and s a l i n i t y ( T a b l e 1 7 ) . Hemipteran d e n s i t y i s n o t c o r r e l a t e d w i t h a s p e c t s o f the p l a n t community, a l t h o u g h i t i s c o r r e l a t e d w i t h s a l i n i t y . Super community i n d i c e s o f community c o m p l e x i t y a r e c o r r e l a t e d w i t h macrophyte community p a r a m e t e r s , b u t n o t w i t h s a l i n i t y . The r e m a i n i n g parameters are r e l a t e d t o both s a l i n i t y and t h e f l o r a l community. The r e s u l t s p r e s e n t e d i n T a b l e 18 show t h a t no c l u s t e r diagrams based on Hemiptera assemblages a r e s i g n i f i c a n t l y c o r r e l a t e d w i t h t h o s e based on m a c r o p h y t e s . Discussion In C h a p t e r s 2 and 3 , both animal and p l a n t s p e c i e s were d e s c r i b e d as c h a r a c t e r i s t i c o f h i g h s a l i n i t i e s (>5000 JJS ) , o f moderate o r low s a l i n i t i e s (<5000 u S ) , o r t o l e r a n t o f a l l s a l i n i t i e s , and the d i s t r i b u t i o n p a t t e r n s o f organisms among l a k e s was c l o s e l y r e l a t e d t o s a l i n i t y . I t i s p o s s i b l e t h a t f a u n a l and f l o r a l s p e c i e s c o u l d have s i m i l a r d i s t r i b u t i o n p a t t e r n s w i t h r e s p e c t t o s a l i n i t y , and/or p l a n t s c o u l d d i r e c t l y i n f l u e n c e the 150 d i s t r i b u t i o n o f a n i m a l s . P r e v i o u s s t u d i e s o f the fauna i n t h e s e C h i l c o t i n l a k e s (Scudder & Mann, 1968; S c u d d e r , 1969a; 1969b; Cannings & S c u d d e r , 1978; R e y n o l d s , 1979; Cannings e t a l _ . , 1980; S c u d d e r , 1983; Cannings & C a n n i n g s , 1985) e s t a b l i s h e d t h a t t h e s a l i n i t y g r a d i e n t i n f l u e n c e s f a u n a l d i s t r i b u t i o n , b u t none have examined f a u n a l d i s t r i b u t i o n s or community dynamics w i t h r e s p e c t t o macrophyte c o m m u n i t i e s . The marked d i f f e r e n c e i n communities above and below 5000 /iS may r e p r e s e n t a c r i t i c a l p o i n t i n the p h y s i o l o g i c a l t o l e r a n c e l e v e l s o f both f l o r a and f a u n a , o r i t c o u l d i n d i c a t e t h a t a n i m a l s a r e p a r t i a l l y dependent upon the d i s t r i b u t i o n o f p l a n t s , which a r e p h y s i o l o g i c a l l y c o n s t r a i n e d by s a l i n i t i e s above t h i s p o i n t . The e v i d e n c e demonstrates t h a t f a u n a l abundance, r i c h n e s s and d i v e r s i t y a r e f r e q u e n t l y , b u t not a l w a y s , a s s o c i a t e d w i t h f l o r a l abundance, r i c h n e s s and d i v e r s i t y ( T a b l e s 16; 1 8 ) . F u r t h e r m o r e , t h e s e parameters a r e f r e q u e n t l y , b u t not a l w a y s , a s s o c i a t e d w i t h s a l i n i t y ( T a b l e s 17; 1 8 ) . Four t y p e s o f a s s o c i a t i o n s among f a u n a l c o m m u n i t i e s , f l o r a l communities and s a l i n i t y were o b s e r v e d . (1) Where f a u n a l communities a r e not a s s o c i a t e d w i t h f l o r a l communities o r s a l i n i t y , the o b s e r v e d p a t t e r n i s presumably a t t r i b u t e d t o a f a c t o r o r c o m b i n a t i o n o f f a c t o r s not used i n t h i s s t u d y . (2) A s s o c i a t i o n s o f animal communities w i t h s a l i n i t y b u t not p l a n t c o m m u n i t i e s , i n d i c a t e t h a t w a t e r c h e m i s t r y may be o f p r i m a r y importance d e t e r m i n i n g the s t r u c t u r e o f animal c o m m u n i t i e s . (3) In some i n s t a n c e s , f a u n a l communities a r e a s s o c i a t e d w i t h f l o r a l c o m m u n i t i e s , b u t not w i t h s a l i n i t y . T h i s i m p l i e s t h a t macrophyte c o m m u n i t i e s , b u t not s a l i n i t y , may be i m p o r t a n t f a c t o r s c o n t r o l l i n g t h e s t r u c t u r e o f a r t h r o p o d c o m m u n i t i e s . (4) Where b o t h f a u n a l and f l o r a l communities a r e a s s o c i a t e d w i t h s a l i n i t y and w i t h each o t h e r , i t i s i m p o s s i b l e to d e t e r m i n e i f the s t r u c t u r e o f 151 animal communities i s a f f e c t e d p r i m a r i l y by s a l i n i t y , by macrophyte communities which a r e t h e m s e l v e s i n f l u e n c e d by s a l i n i t y , o r by t h e combined e f f e c t s o f b o t h . T h i s study used s e v e r a l schemes o f c l a s s i f i c a t i o n , m u l t i v a r i a t e t e c h n i q u e s , and n u m e r i c a l parameters t o c h a r a c t e r i z e and compare the s t r u c t u r e o f f a u n a l c o m m u n i t i e s , f l o r a l c o m m u n i t i e s , and s a l i n i t y . No one method o f was s u f f i c i e n t t o summarize t h e r e l a t i o n s h i p s , r a t h e r , a l l c o n t r i b u t e d some i n f o r m a t i o n t o c h a r a c t e r i z a t i o n s and a l l were n e c e s s a r y t o p r o v i d e a complete p i c t u r e o f t h e a s s o c i a t i o n s . P a r t i c u l a r groups o f a n i m a l s showed d i f f e r e n t p a t t e r n s o f a s s o c i a t i o n w i t h p l a n t communities and s a l i n i t y t h e r e f o r e , t h e s e subcommunities must be examined s e p a r a t e l y . In the d i s c u s s i o n t o f o l l o w , t h e r e l a t i o n s h i p s o f the f o u r f a u n a l groups ( z o o p l a n k t o n , C o l e o p t e r a , H e m i p t e r a , a l l s p e c i e s ) w i t h f l o r a l communities and s a l i n i t y , a r e c o n s i d e r e d s e p a r a t e l y . Some p o s s i b l e mechanisms p r o d u c i n g t h e o b s e r v e d p a t t e r n s a r e h y p o t h e s i z e d . One must remember, however, t h a t f i e l d s t u d i e s can i n d i c a t e c o r r e l a t i o n s between t h e b i o t a and a b i o t a , and c o n t r o l l i n g mechanisms can be h y p o t h e s i z e d , but d e t a i l e d i n v e s t i g a t i o n s o f c a u s a l r e l a t i o n s h i p s r e q u i r e an e x p e r i m e n t a l a p p r o a c h . ZOOPLANKTON COMMUNITIES A s s o c i a t i o n s between f a u n a l and f l o r a l community parameters demonstrate t h a t z o o p l a n k t o n r i c h n e s s and d i v e r s i t y d e c r e a s e d w i t h d e c r e a s i n g macrophyte abundance, r i c h n e s s and d i v e r s i t y . Other s t u d i e s have r e p o r t e d s i m i l a r p a t t e r n s i n z o o p l a n k t o n communities ( S m y l y , 1952; 1953; 1957; W h i t e s i d e & Harmsworth, 1967; Quade, 1969; S h i e l , 1976; F r y & O s b o r n e , 1980; B l a n c h e r , 1984; R i c h a r d e t a l . , 1 9 8 5 ) , b u t many a u t h o r s do 152 not e x p l a i n p o s s i b l e c a u s e s o f t h e p a t t e r n s and t h e l i t e r a t u r e on the s u b j e c t a r e f r e q u e n t l y c o n t r a d i c t o r y . My d a t a s u p p o r t the h y p o t h e s i s , proposed i n C h a p t e r 2 , t h a t mechanisms c o n t r o l l i n g z o o p l a n k t o n community s t r u c t u r e i n t h e B e c h e r ' s P r a i r i e l a k e s , a r e r e l a t e d t o the a v a i l a b l e f o o d s u p p l y and n u t r i t i o n a l r e q u i r e m e n t s o f i n h a b i t i n g s p e c i e s . Changes i n t h e c o m p o s i t i o n and s t r u c t u r e o f z o o p l a n k t o n communities o b s e r v e d w i t h d e c r e a s i n g s a l i n i t y i n the study l a k e s are analogous t o t h o s e r e p o r t e d w i t h i n c r e a s i n g e u t r o p h i c a t i o n ( P a t a l a s , 1972; McNaught, 1975; A l l a n , 1976; G l i w i c z , 1977; Gannon & S t e m b e r g e r , 1978; F r y & O s b o r n e , 1980; R i c h a r d e t a]_., 1985) ( f o r f u r t h e r d i s c u s s i o n see C h a p t e r 2 ) . The e v i d e n c e t h a t l a k e p r o d u c t i v i t y d e c r e a s e d w i t h i n c r e a s i n g s a l i n i t y ( C h a p t e r 3 ) , and t h a t the same z o o p l a n k t o n community parameters t h a t were n e g a t i v e l y c o r r e l a t e d w i t h s a l i n i t y a r e p o s i t i v e l y c o r r e l a t e d w i t h the abundance, r i c h n e s s and d i v e r s i t y o f macrophyte communities ( T a b l e 16; 1 7 ) , f u r t h e r s u p p o r t t h i s h y p o t h e s i s . A l t h o u g h my r e s u l t s are c o n s i s t e n t w i t h the h y p o t h e s i s , the e v i d e n c e i s l a r g e l y c i r c u m s t a n t i a l and a r i g o r o u s e x p e r i m e n t a l approach i s r e q u i r e d t o d e f i n i t i v e l y t e s t t h e mechanisms c o n t r o l l i n g z o o p l a n k t o n community s t r u c t u r e . A d d i t i o n a l l y , t h e r e i s some e v i d e n c e t h a t h a b i t a t p r e f e r e n c e may p l a y an i m p o r t a n t r o l e i n s t r u c t u r i n g z o o p l a n k t o n c o m m u n i t i e s . The p e r c e n t o f each l a k e c o v e r e d by a q u a t i c v e g e t a t i o n i s p o s i t i v e l y a s s o c i a t e d w i t h the a b s o l u t e and r e l a t i v e number o f z o o p l a n k t o n s p e c i e s and e c o l o g i c a l c a t e g o r i e s , and w i t h v i r t u a l l y a l l d i v e r s i t y measures ( T a b l e s 16; 1 7 ) . A l t h o u g h p e r c e n t c o v e r i s n e g a t i v e l y a s s o c i a t e d w i t h s a l i n i t y (Chapter 3 ) , s e v e r a l o f t h e s e f a u n a l parameters a r e n o t . T h i s s u g g e s t s t h a t the amount o f p l a n t c o v e r may a f f e c t some a s p e c t s o f z o o p l a n k t o n community s t r u c t u r e 153 t h a t s a l i n i t y does n o t , a l t h o u g h s a l i n i t y may u l t i m a t e l y be r e s p o n s i b l e f o r s t r u c t u r i n g a q u a t i c macrophyte c o m m u n i t i e s . There a r e many ways i n w h i c h a q u a t i c p l a n t communities c o u l d i n f l u e n c e z o o p l a n k t o n c o m m u n i t i e s . In t h e study l a k e s , l i t t o r a l s p e c i e s o f C l a d o c e r a , such as Chydorus  s p h a e r i c u s , S c a p h o l e b e r i s k i n g i and A l o n a s p p . , were more common i n f r e s h w a t e r l a k e s than s a l i n e o n e s . T h i s may be a phenomenon a t t r i b u t a b l e to i n c r e a s e d e u t r o p h i c a t i o n i n f r e s h w a t e r l a k e s r e l a t i v e t o s a l i n e ones (Gannon & S t e m b e r g e r , 1 9 7 8 ) , o r i t may be because f r e s h w a t e r l a k e s have r e l a t i v e l y more macrophyte c o v e r than s a l i n e o n e s . I t i s w e l l known t h a t l i t t o r a l s p e c i e s , such as t h e C h y d o r i d a e , a r e p r o f o u n d l y a f f e c t e d by the c o m p o s i t i o n and dynamics o f l i t t o r a l macrophyte communities ( W h i t e s i d e & Harmsworth, 1967; Quade, 1969; G o u l d e n , 1971; S h i e l , 1976; W h i t e s i d e e t a l . , 1 9 7 8 ) . Most c h y d o r i d s a r e poor swimmers and remain i n c l o s e c o n t a c t w i t h t h e s u b s t r a t e , hence they seldom o c c u r where t h e r e i s no s u b s t r a t e (animate o r i n a n i m a t e ) . Chydorus s p h a e r i c u s , the most w i d e s p r e a d c h y d o r i d , i s t h e o n l y s p e c i e s showing c o n s i s t e n t swimming b e h a v i o u r and i s o f t e n found among t h e o f f - s h o r e p l a n k t o n , b u t even i t shows a p r e f e r e n c e f o r v e g e t a t e d h a b i t a t s ( W h i t e s i d e et _ a l _ . , 1 9 7 8 ) . Not a l l l i t t o r a l s p e c i e s a r e r e s t r i c t e d by s i m p l e s u b s t r a t e r e q u i r e m e n t s . F o r e x a m p l e , S c a p h o l e b e r i s  k i n g i f e e d s on t h e neuston [ m i c r o s c o p i c components o f the i n t e r f a c e h a b i t a t between a i r and w a t e r ( W e t z e l , 1975)] which i s most e x t e n s i v e i n s h e l t e r e d , q u i e t w a t e r s common i n l i t t o r a l v e g e t a t i o n (Quade, 1 9 6 9 ) . In the study l a k e s , S . k i n g i was r e l a t i v e l y more abundant i n l i g h t t r a p s s e t i n the l i t t o r a l , than i n van Dorn b o t t l e s s e t i n the l i m n e t i c z o n e , and was found o n l y i n l a k e s w i t h e x t e n s i v e submerged v e g e t a t i o n . 154 COLEOPTERAN COMMUNITIES The d i s t r i b u t i o n o f C o l e o p t e r a s p e c i e s e n c o u n t e r e d i n t h e study l a k e s c o r r e s p o n d e d t o t h e i r h a b i t a t p r e f e r e n c e i n r e l a t i o n t o macrophyte c o m m u n i t i e s . There a r e few s t u d i e s on the e c o l o g y o f a q u a t i c c o l e o p t e r a n communities i n N o r t h A m e r i c a , and most o f t h e i n f o r m a t i o n i s c o n t a i n e d i n p r i m a r i l y s y s t e m a t i c t r e a t m e n t s o f v a r i o u s t a x a ( W a l l i s , 1933; H a t c h , 1953; 1965; 1971; A n d e r s o n , 1971; L a r s o n , 1975; A n d e r s o n , 1976; 1 9 8 3 ) . The a v a i l a b l e d a t a , however, s u g g e s t t h a t a l l the s p e c i e s e n c o u n t e r e d i n t h i s study were found i n l a k e s t y p i c a l o f t h e i r p r e f e r r e d h a b i t a t . F o r e x a m p l e , L a c c o b i u s b i g u t t a t u s , Hygrotus s a y i , H. l u t e s c e n s , I l y b i u s s p p . and Graphoderus s p p . a r e t y p i c a l i n h a b i t a n t s o f v e g e t a t e d ponds ( L a r s o n , 1975; 1 9 8 5 ) , and were found o n l y i n the more f r e s h w a t e r l a k e s which s u p p o r t e x t e n s i v e macrophyte c o v e r . C o n v e r s e l y , Hygrotus m a s c u l i n u s shows a p r e f e r e n c e f o r s a l i n e ponds w i t h bare bottoms and w i t h o u t v e g e t a t i o n ( L a r s o n , 1975; 1 9 8 5 ) , and was found o n l y i n more s a l i n e l a k e s w h i c h s u p p o r t r e l a t i v e l y l i t t l e v e g e t a t i o n . The c u r c u l i o n i d , L i t o d a c t y l u s g r i s e o m i c a n s , was abundant i n Lake 2 and one specimen was found i n Lake 3 . T h i s s p e c i e s i s p r o b a b l y r e s t r i c t e d by the d i s t r i b u t i o n o f i t s h o s t p l a n t M y r i o p h y l l u m ( H a t c h , 1971) which o c c u r r e d i n e x t e n s i v e mats i n Lake 2 and i n v e r y s m a l l amounts i n Lake 3 , b u t i n no o t h e r l a k e o f the s e r i e s ( T a b l e 1 2 ) . In a d d i t i o n , dendrograms a r r a n g i n g l a k e s on t h e b a s i s o f the r e l a t i v e abundance o f b e e t l e s p e c i e s c o l l e c t e d i n l i g h t t r a p s a r e s i g n i f i c a n t l y c o r r e l a t e d w i t h t h o s e based on the p r e s e n c e o r absence o f macrophyte s p e c i e s ( T a b l e 1 8 ) . These o b s e r v a t i o n s may r e f l e c t t h e i n f l u e n c e o f p l a n t d i s t r i b u t i o n s on b e e t l e d i s t r i b u t i o n s , o r s i m p l y t h a t b e e t l e s and p l a n t s have s i m i l a r d i s t r i b u t i o n p a t t e r n s w i t h r e s p e c t t o some o t h e r f a c t o r such as s a l i n i t y . 155 The C o l e o p t e r a c o l l e c t e d i n sweep n e t s and l i g h t t r a p s p r e s e n t q u i t e d i f f e r e n t p a t t e r n s o f a s s o c i a t i o n w i t h macrophyte communities and s a l i n i t y . No community parameters c a l c u l a t e d from sweep n e t samples are c o r r e l a t e d w i t h s a l i n i t y , b u t t h e d e n s i t y , a b s o l u t e and r e l a t i v e number o f e c o l o g i c a l c l a s s e s , and super community c o m p l e x i t y measures a r e p o s i t i v e l y c o r r e l a t e d w i t h s e v e r a l macrophyte community parameters ( T a b l e s 16; 1 7 ) . B u t , g e n e r a l i z a t i o n s drawn from sweep n e t samples o f C o l e o p t e r a a r e q u e s t i o n a b l e because t o t a l d e n s i t y and r e l a t i v e abundance o f b e e t l e s were low and v e r y v a r i a b l e i n t h e s e samples ( C h a p t e r 2 ) . T h e r e f o r e , a l t h o u g h sweep samples s u g g e s t t h a t t h e s t r u c t u r e o f b e e t l e communities may be i n f l u e n c e d by macrophyte c o m m u n i t i e s , no d e f i n i t e c o n c l u s i o n s can be drawn from sweep n e t samples w i t h o u t more r e l i a b l e d a t a . E v i d e n c e i n d i c a t e s t h a t s a l i n i t y may be o f p r i m a r y i m p o r t a n c e i n c o n t r o l l i n g c o l e o p t e r a n community s t r u c t u r e , and macrophytes may have some secondary i n f l u e n c e . A l l community parameters c a l c u l a t e d from l i g h t t r a p c o l l e c t i o n s o f C o l e o p t e r a a r e a s s o c i a t e d w i t h s a l i n i t y , and some a r e a s s o c i a t e d w i t h macrophyte community parameters ( T a b l e s 16; 1 7 ) . T h i s i s c o n t r a r y t o o b s e r v a t i o n s o f Cuppen (1983) and van V i e r s s e n & Verhoeven (1983) t h a t h a b i t a t s t r u c t u r e and the p r e s e n c e of p l a n t s p l a y a g r e a t e r r o l e than c h e m i c a l f a c t o r s i n i n f l u e n c i n g a q u a t i c b e e t l e c o m m u n i t i e s . I f macrophytes d i d a f f e c t t h e s t r u c t u r e o f C o l e o p t e r a communities i n t h e s e study l a k e s , i t was i n such a way t h a t c o l e o p t e r a n r i c h n e s s and d i v e r s i t y i n c r e a s e d w i t h i n c r e a s i n g macrophyte d i v e r s i t y ( T a b l e 1 7 ) . W i l s o n (1923) s u g g e s t s t h a t t h i s a s s o c i a t i o n e x i s t e d i n Iowa f i s h p o n d s , b u t no study has c l o s e l y examined the e c o l o g i c a l r e l a t i o n s h i p s between a q u a t i c macrophytes and C o l e o p t e r a . C o n t r a r y t o p r e d i c t i o n s , c o l e o p t e r a n d e n s i t y i n l i g h t t r a p c o l l e c t i o n s 156 o f t h i s study i s n o t c o r r e l a t e d w i t h p e r c e n t a g e macrophyte c o v e r . There a r e two o p p o s i n g hypotheses o f how t h e p e r c e n t a g e v e g e t a t i o n c o v e r p r e s e n t i n a l a k e can i n f l u e n c e the d e n s i t y o f a q u a t i c C o l e o p t e r a . (1) W i l s o n (1923) and A i k e n & W i l k i n s o n (1985) s u g g e s t t h a t t h e g r e a t e s t d e n s i t y o f d i v i n g b e e t l e s s h o u l d o c c u r i n t h e absence o f a q u a t i c p l a n t growth because v e r y dense v e g e t a t i o n makes swimming and s u r f a c i n g t o b r e a t h e very d i f f i c u l t f o r t h e s e a n i m a l s . (2) A l t e r n a t i v e l y , W i l s o n (1923) o b s e r v e d t h a t c o l e o p t e r a n d e n s i t y i n c r e a s e d w i t h i n c r e a s i n g macrophyte c o v e r , and a t t r i b u t e d t h i s t o i n c r e a s e d h a b i t a t h e t e r o g e n e i t y . C o l e o p t e r a n d e n s i t y i n l i g h t t r a p samples o f t h i s s t u d y i s not c o r r e l a t e d w i t h macrophyte c o v e r ( T a b l e s 16; 1 7 ) , a l t h o u g h i t i s p o s i t i v e l y r e l a t e d t o s a l i n i t y and t h e r e i s a t r e n d f o r d e c r e a s i n g macrophyte abundance w i t h i n c r e a s i n g s a l i n i t y . I t i s p o s s i b l e t h a t the two o p p o s i n g p r o c e s s e s , mentioned a b o v e , were b o t h o p e r a t i n g i n t h e study l a k e s , w i t h t h e n e t r e s u l t t h a t t h e r e i s no a p p a r e n t a s s o c i a t i o n between macrophyte c o v e r and b e e t l e d e n s i t y . A l t e r n a t i v e l y , v e g e t a t i o n c o v e r may have no i n f l u e n c e on a q u a t i c b e e t l e c o m m u n i t i e s . I t may s i m p l y be t h a t t h e few C o l e o p t e r a s p e c i e s adapted t o h i g h s a l i n i t i e s o c c u r r e d i n enormous numbers owing t o l a c k o f c o m p e t i t i o n and p r e d a t i o n ( B e a d l e , 1943; S i m b e r l o f f & W i l s o n , 1974) as s u g g e s t e d i n C h a p t e r 2 . HEMIPTERAN COMMUNITIES The r e s u l t s s u g g e s t t h a t both s a l i n i t y and macrophyte community s t r u c t u r e may have i n f l u e n c e d t h e s t r u c t u r e o f h e m i p t e r a n c o m m u n i t i e s . S i m i l a r p a t t e r n s o f hemipteran community s t r u c t u r e were p r o v i d e d i n both l i g h t t r a p and sweep n e t samples ( T a b l e s 16; 17; 1 8 ) . A marked d i f f e r e n c e was seen i n hemipteran community c o m p o s i t i o n beween l a k e s w i t h c o n d u c t i v i t i e s above and below 5000 uS ( C h a p t e r 2 ) . T h i s may r e p r e s e n t a 157 c r i t i c a l p o i n t o f s a l i n i t y t o l e r a n c e s f o r H e m i p t e r a , as s u g g e s t e d a b o v e , or i t may be because Hemiptera were i n f l u e n c e d by t h e macrophyte community which changed d r a m a t i c a l l y a t t h i s p o i n t ( C h a p t e r 3 ) . A d i s t i n c t e c o l o g i c a l s u c c e s s i o n o f c o r i x i d s p e c i e s w i t h d e c r e a s i n g s a l i n i t y , and i n c r e a s i n g v e g e t a t i o n c o v e r and a c c u m u l a t i o n o f o r g a n i c m a t t e r has been o b s e r v e d i n Europe (Macan, 1938; S a v a g e , 1971; van V i e r s s e n & V e r h o e v e n , 1 9 8 3 ) , and a l t h o u g h a s u c c e s s i o n i s s u g g e s t e d i n t h i s study ( C h a p t e r 2 ) , none has p r e v i o u s l y been r e c o r d e d i n N o r t h A m e r i c a . A q u a t i c H e m i p t e r a , e s p e c i a l l y C o r i x i d a e , a r e t y p i c a l i n h a b i t a n t s o f t h e l i t t o r a l zone and a r e dependent on i t s p h y s i c a l s t r u c t u r e . T h e i r e x t e r n a l a i r s t o r e s used f o r r e s p i r a t i o n make them e x t r e m e l y buoyant and t h e r e f o r e they must c l i n g t o v a r i o u s submerged o b j e c t s ( s u c h as v e g e t a t i o n ) t o p r e v e n t from bobbing t o t h e s u r f a c e ( S c u d d e r , 1 9 7 6 ) . T h e i r dependence on e x t e r n a l a i r s t o r e s , w h i c h need t o be renewed p e r i o d i c a l l y , r e s t r i c t s them t o r a t h e r s h a l l o w w a t e r s ( S c u d d e r , 1 9 7 6 ) . C o n s e q u e n t l y , a p o s i t i v e c o r r e l a t i o n between p e r c e n t a g e v e g e t a t i o n c o v e r and hemipteran d e n s i t y i s p r e d i c t e d because a more e x t e n s i v e a r e a o f s u i t a b l e h a b i t a t would p o t e n t i a l l y s u p p o r t more i n d i v i d u a l s . No such c o r r e l a t i o n was found i n t h i s s t u d y , perhaps because macrophyte abundance never dropped below a c r i t i c a l p o i n t a t which i t was l i m i t i n g , and/or because enough i n a n i m a t e s u b s t r a t e were a v a i l a b l e . D e n s i t y i s , however, n e g a t i v e l y r e l a t e d t o s a l i n i t y w h i c h s u g g e s t s t h a t t h e few s p e c i e s adapted t o h i g h s a l i n i t i e s o c c u r r e d i n enormous numbers owing t o l a c k o f c o m p e t i t i o n and p r e d a t i o n ( B e a d l e , 1943; S i m b e r l o f f & W i l s o n , 1974) as was s u g g e s t e d i n Chapter 2 . I n c r e a s e d macrophyte d i v e r s i t y may have c o n t r i b u t e d t o i n c r e a s e d h e m i p t e r a n r i c h n e s s and d i v e r s i t y i n t h e study l a k e s , as a l l parameters o f hemipteran community s t r u c t u r e a r e c o r r e l a t e d w i t h t h e macrophyte community 158 ( T a b l e 1 6 ) . I t i s p o s s i b l e t h a t s p e c i e s r i c h o r d i v e r s e hemipteran communities were found i n d e n s e , r i c h o r d i v e r s e p l a n t communities because (1) prey organisms were more abundant i n such h a b i t a t s , (2) p l a n t s p r o v i d e d p r o t e c t i o n from p r e d a t o r s (Macan, 1 9 6 5 ) , o r (3) a more d i v e r s e s u b s t r a t e was a v a i l a b l e f o r h o l d i n g on t o . T h i s l a t e r s u g g e s t i o n may a c c o u n t f o r t h e wide v a r i e t y o f hemipteran s i z e groups i n l a k e s w i t h d i v e r s e p l a n t assemblages i f body s i z e i s an i m p o r t a n t f a c t o r i n s u b s t r a t e p r e f e r e n c e . My d a t a , however, i n d i c a t e c o r r e l a t i o n s between hemipteran communities and both macrophyte communities and s a l i n i t y . Thereby making i t i m p o s s i b l e to d i s t i n g u i s h between c a u s a l mechanisms r e l a t e d t o p l a n t community s t r u c t u r e ( a b o v e ) , o r s a l i n i t y ( C h a p t e r 2 ) . More d e t a i l e d i n v e s t i g a t i o n s are r e q u i r e d t o d i s t i n g u i s h between the p r o c e s s e s and examine c a u s a l r e l a t i o n s h i p s . ENTIRE FAUNAL COMMUNITY My d a t a i n d i c a t e t h a t the s t r u c t u r e o f the e n t i r e f a u n a l community, as r e p r e s e n t e d by a l l a n i m a l s c a u g h t i n l i g h t t r a p s , i s r e l a t e d t o both s a l i n i t y and t h e macrophyte community. The r e l a t i v e abundance o f animal s p e c i e s d i f f e r e d markedly among l a k e s i n r e l a t i o n t o s a l i n i t y ( F i g . 8 a ) , and t h e dendrogram a r r a n g i n g l a k e s on the b a s i s o f animal s p e c i e s r e l a t i v e abundance i s s i g n i f i c a n t l y c o r r e l a t e d w i t h t h e dendrogram based on p r e s e n c e o r absence o f p l a n t s p e c i e s ( T a b l e 1 8 ) . F o r the most p a r t , the same f a u n a l community parameters t h a t were n e g a t i v e l y c o r r e l a t e d w i t h s a l i n i t y a r e p o s i t i v e l y c o r r e l a t e d w i t h t h e abundance, r i c h n e s s and d i v e r s i t y o f macrophyte communities ( T a b l e s 16; 1 7 ) . These p a t t e r n s o f a s s o c i a t i o n a r e v e r y s i m i l a r t o t h o s e o f t h e e n t o m o s t r a c a n subcommunity, b u t t h o s e o f t h e C o l e o p t e r a and Hemiptera were h i d d e n . T h i s demonstrates t h a t n u m e r i c a l l y 159 dominant subgroups can d i c t a t e p a t t e r n s o b s e r v e d f o r t h e e n t i r e community and mask i m p o r t a n t p a t t e r n s i n o t h e r s i b g r o u p s , as was a l s o seen i n C h a p t e r 2 . Other s t u d i e s have r e p o r t e d s i m i l a r p a t t e r n s o f a s s o c i a t i o n between f l o r a l communities and the e n t i r e f a u n a l community ( K r e c k e r , 1939; R o s i n e , 1955; H a r r o d , 1964; P e t r , 1968; K r u l l , 1970; S o s z k a , 1975a; 1975b; Brock & S h i e l , 1 9 8 3 ) , b u t because t h e o b s e r v e d p a t t e r n s a r e a l s o r e l a t e d t o s a l i n i t y , i t i s i m p o s s i b l e t o d e t e r m i n e whether s a l i n i t y and/or p l a n t communities may be of p r i m a r y i m p o r t a n c e i n s t r u c t u r i n g t h e e n t i r e f a u n a l community. Summary T h i s f o u r t h c h a p t e r b r i e f l y d i s c u s s e s some o f t h e many ways i n w h i c h a q u a t i c macrophytes can d i r e c t l y o r i n d i r e c t l y i n f l u e n c e t h e d i s t r i b u t i o n and s u r v i v a l o f a q u a t i c f a u n a . E c o l o g i c a l r e l a t i o n s h i p s between f a u n a l and f l o r a l communities were t e s t e d f o r i n t h e B e c h e r ' s P r a i r i e s t u d y l a k e s by comparing the f a u n a l and f l o r a l communities c h a r a c t e r i z e d i n C h a p t e r s 2 and 3 r e s p e c t i v e l y , and summarizing t h e i r r e l a t i o n s h i p s w i t h r e f e r e n c e t o s a l i n i t y . E v i d e n c e i n d i c a t e s t h a t both s a l i n i t y and macrophyte communities may have p l a y e d a r o l e i n s t r u c t u r i n g z o o p l a n k t o n , c o l e o p t e r a n , h e m i p t e r a n , and the e n t i r e f a u n a l community. P a r t i c u l a r groups o f a n i m a l s show d i f f e r e n t p a t t e r n s o f a s s o c i a t i o n w i t h p l a n t communities and s a l i n i t y t h e r e f o r e , t h e s e subcommunities must be examined s e p a r a t e l y . Z o o p l a n k t o n r i c h n e s s and d i v e r s i t y d e c r e a s e d w i t h d e c r e a s i n g macrophyte abundance, r i c h n e s s and d i v e r s i t y . E v i d e n c e suppors t h e h y p o t h e s i s t h a t mechanisms c o n t r o l l i n g z o o p l a n k t o n community s t r u c t u r e a r e r e l a t e d t o t h e a v a i l a b l e f o o d s u p p l y and n u t r i t i o n a l r e q u i r e m e n t s o f i n h a b i t i n g s p e c i e s . There i s 160 a l s o some e v i d e n c e t h a t h a b i t a t p r e f e r e n c e may p l a y a r o l e i n s t r u c t u r i n g z o o p l a n k t o n c o m m u n i t i e s . S a l i n i t y may be o f p r i m a r y i m p o r t a n c e i n c o n t r o l l i n g c o l e o p t e r a n community s t r u c t u r e , and macrophytes may have some secondary i n f l u e n c e . C o n t r a r y t o p r e d i c t i o n s , c o l e o p t e r a n d e n s i t y i s n o t c o r r e l a t e d w i t h p e r c e n t macrophyte c o v e r . 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A r e v i e w w i t h s p e c i a l r e l e v a n c e t o a q u a t i c e c o s y s t e m s . Water R e s . 18: 6 5 3 - 6 9 4 . W e s t l a k e , D . F . 1963. Comparisons o f p l a n t p r o d u c t i v i t y . B i o l . R e v . 3 8 : 3 8 5 - 4 2 5 . W e s t l a k e , D . F . 1 9 6 5 . Some b a s i c data f o r i n v e s t i g a t i o n s o f the p r o d u c t i v i t y o f a q u a t i c m a c r o p h y t e s . M e m . I s t . I t a l . I d r o b i o l . 1 8 ( S u p p l . ) : 2 2 9 - 2 4 8 . W e t z e l , R . G . 1969. E x c r e t i o n o f d i s s o l v e d o r g a n i c compounds by a q u a t i c m a c r o p h y t e s . B i o s c i e n c e 19: 5 3 9 - 5 4 0 . W e t z e l , R . G . 1975. L i m n o l o g y . S a u n d e r s , P h i l a d . . 743 p p . W e t z e l , R . G . & B . A . Manny. 1972. S e c r e t i o n o f d i s s o l v e d o r g a n i c carbon and n i t r o g e n by a q u a t i c m a c r o p h y t e s . V e r h . I n t . V e r . L i m n o l . 18: 175 162-170. W h i t e s i d e , M . C . & R . V . Harmsworth. 1967. S p e c i e s d i v e r s i t y i n c h y d o r i d ( C l a d o c e r a ) c o m m u n i t i e s . E c o l o g y 4 8 : 6 6 4 - 6 6 7 . W h i t e s i d e , M . C , J . B . W i l l i a m s & C P . W h i t e . 1978. S e a s o n a l abundance and p a t t e r n o f c h y d o r i d C l a d o c e r a i n mud and v e g e t a t i v e h a b i t a t s . E c o l o g y 5 9 : 1177-1188. W i e d e r h o l m , T. 1980. E f f e c t s o f d i l u t i o n on t h e benthos o f an a l k a l i n e l a k e . H y d r o b i o l o g i a 6 8 : 1 9 9 - 2 0 7 . W i g g i n s , G . B . 1977. L a r v a e o f t h e N o r t h American c a d d i s f l y genera ( T r i c h o p t e r a ) . U n i v . T o r o n t o P r e s s , T o r o n t o . 401 p p . W i l l i a m s , W.D. 1967. The c h e m i c a l c h a r a c t e r i s t i c s o f l e n t i c s u r f a c e w a t e r s i n A u s t r a l i a . I n : W e a t h e r l y , A . H . ( e d . ) . A u s t r a l i a n i n l a n d w a t e r s and t h e i r f a u n a : e l e v e n s t u d i e s . A u s t r a l i a n N a t i o n a l U n i v e r s i t y P r e s s , C a n b e r r a , p p . 18-77. W i l l i a m s , W.D. 1978. Limnology of V i c t o r i a n s a l t l a k e s . V e r h . I n t . V e r . L i m n o l . 2 0 : 1165-1174. W i l l i a m s , W.D. 1981a. I n l a n d s a l t l a k e s : An i n t r o d u c t i o n . H y d r o b i o l o g i a 8 1 / 8 2 : 1 - 1 4 . W i l l i a m s , W.D. 1981b. The l i m n o l o g y o f s a l i n e l a k e s i n Western V i c t o r i a . H y d r o b i o l o g i a 8 2 : 2 3 3 - 2 5 9 . W i l s o n , C B . 1923. Water b e e t l e s i n r e l a t i o n t o p o n d f i s h c u l t u r e w i t h l i f e h i s t o r i e s o f t h o s e found i n f i s h p o n d s a t F a i r p o r t , Iowa. B u l l . U . S . B u r . F i s h e r i e s 3 9 : 2 3 1 - 3 4 5 . W i l s o n , M . S . 1959. C a l a n o i d a . I n : Edmondson, W.T. ( e d . ) . Ward and W h i p p l e ' s f r e s h w a t e r b i o l o g y , 2 n d e d . John W i l e y & S o n s , N.Y. p p . 738-794. W o l f e , L . S . 1953. A study o f t h e genus U r o p e t a l a S e l y s (Order Odonata) from New Z e a l a n d . T r a n s . r o y . S o c . N . Z . 8 0 : 2 4 5 - 2 7 5 . Yeatman, H . C 1959. C y c l o p o i d a . I n : Edmondson, W.T. ( e d . ) . Ward and W h i p p l e ' s f r e s h w a t e r b i o l o g y , 2 n d e d . John W i l e y & S o n s , N.Y. p p . 7 9 5 - 8 1 5 . Z a h l , S . 1977. J a c k k n i f i n g an i n d e x o f d i v e r s i t y . E c o l o g y 5 8 : 9 0 7 - 9 1 3 . Z a r e t , T . M . 1980. P r e d a t i o n and f r e s h w a t e r c o m m u i t i e s . Y a l e U n i v e r s i t y P r e s s . 187 p p . Z a r e t , T . M . 1982. The s t a b i l i t y / d i v e r s i t y c o n t r o v e r s y : A t e s t o f h y p o t h e s e s . E c o l o g y 6 3 : 721-731. 176 APPENDIX A S e a s o n a l c o n d u c t i v i t y (uS c m - 1 , 25 ° C ) a t 1 m depth i n the s t u d y l a k e s i n 1978. (See F i g . 1 f o r l a k e names). Lakes Date 1 2 3 4 5 6 7 8 6 - 8 May 72 913 1253 2233 3706 6335 7356 7629 5-7 June 58 980 1362 2589 4441 7761 9945 11989 5-7 J u l y 57 913 1457 2852 4564 8446 10490 13214 4 - 5 A u g . 53 933 1501 2866 4777 8956 11420 14852 3 - 5 S e p t . 49 918 1568 2986 4881 9106 11449 15524 14-15 O c t . 45 933 1483 3027 4892 9083 11532 15481 mean 56 932 1437 2759 4544 8281 10365 13115 range 27 67 315 794 1186 2771 4176 7895 maximum 72 980 1568 3027 4892 9106 11532 15524 177 APPENDIX B B . l Abundance o f z o o p l a n k t o n s p e c i e s and e c o l o g i c a l c a t e g o r i e s i n Van Dorn b o t t l e s a m p l e s , (#/2 1 summed o v e r e n t i r e s e a s o n ) . (See F i g . 1 f o r l a k e names; T a b l e 7 f o r s p e c i e s names; t e x t f o r c a t e g o r y d e s c r i p t i o n ) . 1 2 3 4 Lake 5 6 7 8 SPECIES 2 - - - 76 36 - - -3 - - - - - 356 406 179 4 860 - - - - - - -5 - 499 1105 1155 2180 - - -6 94 - - - - - - -7 9 - - 1 2 - - -8 1 - - - - - - -9 21 71 1 1645 25 - 1 -10 - - - - - - - 179 12 11 - - - - - - -13 4 2 1 12 - - - -14 31 1 - 146 1 - - -17 17 4 1 - - - - -18 - - - - - 69 37 10 19 - - - 1069 - 1376 1946 1147 20 - 39 - 386 - - - -21 161 - - 229 231 - - -22 - - - 131 251 - - -23 8 1 - - 3 - - -# - - 18 - - - - -77 105 74 63 1 31 - - -79 11 3 1 121 1 - 1 -ECOLOGICAL CATEGORIES b l 35 2 1 258 1 - - -b3 126 71 1 1714 25 1376 1946 1147 b4 877 513 1106 1155 2180 - - 179 b5 - - - - - 356 406 179 b6 9 - - 1 2 - - -b7 - - - 76 36 - - -c l - 39 - 386 - - - -e3 161 - 18 360 482 - - -e4 8 1 - - 3 - 1 -e6 - - - - - 69 37 10 e8 116 77 64 122 32 - - -178 B . 2 Abundance o f s p e c i e s and e c o l o g i c a l c a t e g o r i e s i n submerged l i g h t t r a p s , (#/5 t r a p n i g h t s ) . (See F i g . 1 f o r l a k e names; T a b l e 7 f o r s p e c i e s names; t e x t f o r c a t e g o r y d e s c r i p t i o n ) . 1 2 3 4 l a k e 5 6 7 8 SPECIES 1 - - - - - - 36 24 2 - - - 54476 7072 - - -3 - - - - - 243753 247616 71960 4/6 14453 - - - - - - -5 - 163662 856252 356416 234161 - - -7 795 737 272 2788 3596 16 - -8 13 100 868 48 - - - -9 32 8359 1044 70116 22415 8 - -10 - - - - - - - 3480 11 - - 56 1268 - - - -13 58 6 - 20 - - - -14 146 181 244 2418 - - - -15 583 - - 52 - - - - -16 95 11 16 - - - - -17 396 14 1148 - - - - -18 - - - - - 24480 71040 24093 19 - - - 35327 - 720 3320 50431 21/22 52 155 244 8912 8641 16 - 20 23 547 536 - 36 580 - - -24 - 800 134 3628 1781 - - -25 - 443 35 - 79 - - -26 1 - - - - - - -27 1 - - - - - - -28 2 - - - - - - -29 15 31 32 88 9 45 11 -30 3 11 - - 25 1 - -31 8 - 16 - - - - -32 27 160 436 464 83 65 4 64 33 1 - - - - - - -34 1 - - - - - - -35 3 - - - - - - 1 36 34 82 154 8 22 - - -37 3 3 - - - - - -38 5 331 27 4 - - - -39 - - - - - 942 319 168 40 139 22 - 40 103 - - -41 56 217 79 509 95 5 - -42 166 179 1048 2104 656 762 620 3206 43 - - - - - 636 925 15571 44 62 2 - - - - - -179 B . 2 CONT. 1 2 3 4 Lake 5 6 7 8 45 1 2 - - - - 1 -46 - 28 98 128 I l l 11 1 -47 21 - - - - - - -48 5 - - - - - - -49 2 - - - - - - -50 2 13 5 12 4 2 - -51 17 2 - 4 - - - -52 - - - - - 65 458 1861 55 16 - - - - - - -56 - - - - - 3 2 -57 29 1 - - - 77 - -59 7 - - - 3 - - -60 3 3 - - - - - -61 5 7 - - - - - -62 2 294 51 - 309 - - -63 2 - - - - - - -64 - 5 - - - - - -72 1 - - - - - - -73 4 4 - 196 - 107 15 -74 - - - - - 32 - 2000 75 - - - - 35 - - -76 - - - - 12 - - -77 954 8100 4700 48 311 - - -78 26 84 - - - 32 52 20 79 12 - - 7 - - - -80 79 214 2346 943 1124 18 34 1196 81 1 16 - - - - 18 -82 2 - 404 255 427 16 - 20 83 149 - - - - - - -84 16 - - - - - - -ALL ECOLOGICAL CATEGORIES a5 63 32 98 128 I l l 11 2 -a6 21 - - - - - - -a8 8 4 - 196 - 107 15 -b l 204 187 244 2438 - - - -b2 13 100 924 1316 - - - -b3 14485 8359 1044 105443 22415 728 3320 50431 b4 396 163676 857400 356416 234161 - - 3480 b5 795 737 272 2788 3596 243769 247616 71960 b6 - - - 54476 7072 - - -b8 - - - - 47 32 - 2000 blO - - - - - - 36 24 180 B . 2 CONT. 1 2 3 4 Lake 5 6 7 8 c2 1 - - - - - - -c3 678 1 16 52 - - - -c6 1 - - - - - - -c7 15 831 166 3716 1790 45 11 -c8 82 230 2750 1198 1551 34 52 1216 c9 2 - - - - - - -clO - 443 35 - 79 - - -e3 52 155 244 8912 8641 16 - 20 e4 547 536 - 36 580 - - -e5 19 2 - 4 - - - -e6 23 13 5 12 4 24547 71498 25954 e7 201 1 - - 3 80 2 -e8 1005 8488 4751 55 620 35 52 20 e9 1 - - - - - - -elO 42 176 452 464 108 66 4 64 f7 310 532 1075 2148 759 2340 1864 18945 f 8 56 217 79 509 95 5 - -f 9 37 85 154 8 22 - - -ENTOMOSTRACAN ECOLOGICAL CATEGORIES b l 204 187 244 2438 - - - -b3 14498 8459 1968 106759 22415 728 3320 50431 b4 396 163676 857400 356416 234161 - - 3480 b5 - - - - - 243753 247616 71960 b6 795 737 272 2788 3596 16 - -b7 - - - 54476 7072 - - -e3 52 155 244 8912 8641 16 - 20 e4 547 536 - 36 580 - - -e6 - - - - - 24480 71040 24093 COLEOPTERAN ECOLOGICAL CATEGORIES a l 63 32 98 128 I l l 11 2 -a2 21 - - - - - - -e l 11 1 - 4 - - - -e2 11 - - - - 65 447 1845 e3 1 8 4 12 4 5 2 -e4 21 1 - - 3 77 - -e5 8 181 27 - 198 - - -e8 1 3 - - - - - -181 B.2 CONT. Lake 1 2 3 4 5 6 7 8 HEMIPTERAN ECOLOGICAL CATEGORIES f4 141 309 689 1276 403 844 766 1738 f5 30 73 52 276 86 5 f6 37 85 154 8 22 182 B . 3 Abundance o f a d u l t Hempitera and C o l e o p t e r a i n sweep n e t s a m p l e s , (#/10 s t a n d a r d sweeps summed o v e r e n t i r e s e a s o n ) . (See F i g . 1 l a k e names; T a b l e 7 f o r s p e c i e s names ; t e x t f o r c a t e g o r y d e s c r i p t i o n ) . Lake 1 2 3 4 5 6 7 8 SPECIES 36 79 467 54 2 21 33 2 37 32 3 - - - -38 - 161 6 3 3 - -39 - - - - 6 1 40 155 15 17 - 12 - -41 202 98 92 133 211 3 -42 36 54 704 1270 408 3601 128 4247 43 - - - - 506 24 3854 44 114 5 1 7 28 19 1 12 45 - 9 3 - 4 3 2 46 - 11 20 77 27 - 1 47 8 - - - - -48 4 20 - - - -49 21 3 - - 3 -50 - 1 9 - - -51 25 3 2 3 - -52 - - - - 2 27 24 53 - 3 - - - -54 - - - - 1 -55 7 - - - - -56 - - - - 1 8 57 - - - - 3 -58 - - - - 2 6 59 - - - 2 3 -60 - 7 - - - -61 - - - 4 - -62 - 120 9 7 44 4 3 64 - 7 - 7 - -65 2 - - - - -66 2 - - - - -67 - 3 - - - -68 - - - - 10 5 69 - - - 12 - 9 70 - 141 2 - - - -71 - 76 2 - - - -COLEOPTERAN ECOLOGICAL CATEGORIES a l 114 111 26 83 58 32 7 17 a2 3 141 2 - - - -183 B . 3 CONT. 1 2 3 4 Lake 5 6 7 8 a3 - - - 12 - - 9 e l 46 - 7 2 3 3 - -e2 11 20 3 - - 3 27 24 e3 - 1 9 - 1 - 8 e4 - - - 2 8 - 7 e5 2 127 9 7 32 19 1 12 e6 2 3 - - - - - -e8 7 - - 7 - - -HEMIPTERAN ECOLOGICAL CATEGORIES f4 191 229 727 1274 424 4113 153 8101 f 5 202 98 92 133 211 3 - -f6 111 470 54 2 21 33 - 2 184 APPENDIX C P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l community p a r a m e t e r s . (See T a b l e 6 f o r symbol d e s c r i p t i o n ) . WATER BOTTLE ZOOPLANKTON •—• . — t o I I I 4 J -t-> — — ^— ~_ T 3 "O "O I I o- o- o- O" LIGHT TRAP ENTOMOSTRACA D s t i H ' ( s ) H ' ( t ) H ' ( t i ) H ' t ( s ) H'td) H ' t i ( s ) Q j ( s ) Q j ( t i ) Qd<s) Q d ( t i ) 264 .744 .897 .600 .785 .674 .801 .498 .047 .743 .897 .731 .866 SWEEP HEMIPTERA LIGHT TRAP HEMIPTERA "-3 R O " O X ) Cr cr O- cr D S t i H ' ( s ) H ' ( t i ) H't1<s> Q j ( s ) Q j ( t i ) Qd(s) Q d ( t i ) .686 .731 .865 .706 .961 .812 .731 .865 .298 .197 185 appendix d P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f a u n a l community p a r a m e t e r s and p h y s i o c h e m i c a l v a r i a b l e s . See T a b l e 6 f o r d e s c r i p t i o n o f community parameter symbols; k25 = c o n d u c t i v i t y ; z = mean d e p t h . Community p a r a m e t e r V a r i a b l e D s t i H'(s) H ' ( t ) H ' ( t l ) H ' t ( s ) H ' t ( 1 ) H ' t i ( s ) Q j ( s ) Q j ( t i ) Qd(s) Q d ( t i ) WATER BOTTLE - ZOOPLANKTON K 2 5 .037 -.792 -.660 -.374 -.848 -.321 .052 .316 -.454 -.792 -.660 .528 .335 l o g k 2 5 .270 -.749 - . 4 8 9 " -.393 -.651 -.409 -.102 .029 -.309 -.751 -.496 .647 .246 P C I .021 -.789 -.696 -.322 -.627 -.259 .010 .297 -.432 -.789 -.696 .489 .551 PC2 .058 .085 .364 -.234 .072 -.276 -.357 -.423 -.106 .087 .364 .132 -.027 z .048 -.880 -.780 -.548 -.848 - . 5 3 3 -.182 .033 -.517 -.880 -.780 .616 .351 DLA -.478 .538 .509 .050 .623 .084 -.337 -.432 -.038 .539 .509 -.118 .123 SWEEP -• COLEOPTERA K 2 5 -.559 -.338 -.265 .068 -.286 .217 .041 .341 -.232 -.338 -.265 .463 .285 1ogk 25 -.505 -.209 -.317 .106 -.266 .160 .164 .169 -.055 -.232 -.345 .584 .352 PCI -.546 -.357 -.272 .036 -.328 .202 .014 .336 -.274 -.357 -.272 .455 .276 PC2 -.019 .098 .229 .335 .292 .296 .326 .257 ' .190 .098 .229 -.092 -.148 z -.685 - . 1 1 5 - . 3 1 3 .085 -.095 .049 .009 .086 .093 - . 1 1 5 - . 3 1 3 .513 .564 DLA .814 .452 .553 .316 .569 .302 .212 .179 .142 .452 .553 -.779 -.784 SWEEP -• HEMIPTERA K 2 5 .699 -.774 -.725 -.544 -.867 .786 -.774 -.725 .429 .551 l o g k 2 5 .490 -.557 -.500 -.790 -.850 .343 -.572 -.528 .668 .523 PCI .737 -.790 -.724 -.535 -.879 .825 -.790 -.724 .365 .516 PC2 -.049 .028 .015 .151 .185 -.110 .028 .015 .285 .084 z .418 - . 5 3 3 -.574 - . 7 2 3 -.884 .520 - . 5 3 3 -.574 .518 .690 °LA -.390 .710 .451 .894 .906 -.277 .710 .451 -.595 -.703 186 APPENDIX D CONT. Community parameter Variable D s t i H'(s) H'(t) H'(ti) H' t(s) H' t(i) H' ti(s) Qj(s) Q j ( t i ) Qd(s) Qd(ti) LIGHT TRAP - ALL S P E C I E S K 2 5 -.195 -.781 -.901 .282 - . 2 1 2 .324 .505 .581 -.205 -.780 -.901 .712 .550 logk 25 .208 -.963 - . 9 1 5 -.057 -.643 -.032 .325 .391 -.272 -.964 - . 9 1 9 .938 .622 PCI - . 2 1 3 -.731 -.872 .326 -.166 .363 .535 .603 -.131 -.730 -.872 .662 .499 PC2 -.087 -.254 -.140 .023 .041 .064 .005 .059 -.374 -.249 -.137 .171 .178 z .086 -.788 -.874 - . 2 1 3 -.605 -.184 .091 .160 -.420 -.788 -.875 .837 .716 OLA -.328 .625 .645 -.080 .514 -.061 -.419 -.424 -.229 .625 .645 -.539 -.128 LIGHT TRAP - ENTOMOSTRACA K 2 5 -.205 - . 8 1 3 -.764 .439 .906 .302 -.031 -.312 .554 -.812 -.789 .388 .270 logk 25 .200 -.634 -.526 .280 .580 .201 -.024 -.195 .336 -.651 -.587 .196 -.063 P C I -.223 -.760 -.635 .459 .695 .307 -.103 -.366 .599 -.760 -.789 .364 .387 PC2 -.091 -.342 .025 .088 .015 .128 .108 .143 -.025 -.346 .092 .123 -.072 z .088 -.786 - . 7 3 3 .026 .764 - . 0 1 2 -.396 - . 5 3 3 .093 -.787 -.848 .473 .259 DLA -.329 .324 .432 -.356 -.577 -.314 -.065 .078 -.309 .324 .515 .154 .191 LIGHT TRAP - COLEOPTERA K 2 5 .736 -.626 - . 7 1 5 -.680 -.863 -.663 -.409 -.346 -.558 -.626 - . 7 1 5 .587 .790 l o g k 2 5 .465 -.868 -.866 -.832 -.727 -.781 -.700 -.634 -.832 -.861 -.861 .913 .867 PCI .751 -.583 -.692 -.656 -.900 -.646 -.354 -.294 -.502 -.583 -.692 .539 .751 PC2 .179 -.238 -.145 -.127 .281 -.088 -.344 -.328 -.287 -.239 -.145 .195 .177 z .276 -.602 - . 6 1 3 - . 5 1 6 -.707 -.460 -.278 -.182 -.639 -.602 - . 6 1 3 .654 .798 DLA -.995 .645 .666 .537 .676 .477 .326 .215 .673 .645 .666 -.581 -.654 LIGHT TRAP - HEMIPTERA K 2 5 .548 -.852 -.944 -.314 -.946 .645 -.852 -.944 .523 .415 l o g k 2 5 .607 -.837 -.663 -.598 - . 8 1 5 .297 -.844 -.679 .216 -.016 PCI .584 -.806 -.960 -.262 -.951 .691 -.806 -.960 .493 .406 PC2 -.174 -.289 .076 -.348 .082 -.352 -.289 .076 .199 .157 z .331 -.829 -.777 -.286 -.926 .648 -.829 -.777 .627 .369 \A -.675 .642 .602 .514 .824 -.372 .642 .602 -.394 .068 187 APPENDIX E Mean c o n d u c t i v i t y (uS c m - 1 , 25 ° C ) o f each s t u d y l a k e i n 1983. (See F i g . 1 f o r l a k e names). Lake 1 2 3 4 5 6 7 8 C o n d u c t i v i t y 42 740 1443 2723 4443 8067 10667 12117 Seasonal c o n d u c t i v i t y (uS c m - 1 , 25 ° C ) a t 1 m depth i n t h e study l a k e s i n 1984 . (See F i g . 1 f o r l a k e names) • Lake Date 1 2 3 4 5 6 7 8 12 May 90 942 1594 2681 4638 8406 10870 13478 13 June 67 913 1638 2826 4812 8696 11449 13913 7 J u l y 36 1014 2029 3130 5145 9130 12174 14928 12 August 101 1014 1812 3478 5406 9783 12899 15797 14 September 29 899 1739 3072 5072 10724 12319 14782 mean 65 956 1762 3038 5014 9348 11942 14580 range 72 115 435 797 768 2318 2029 2319 maximum 101 1014 2029 3478 5406 10724 12899 15797 188 APPENDIX F R e l a t i v e abundance o f macrophyte s p e c i e s , e s t i m a t e d on the B r a u n - B l a n q u e t s c a l e , a t mid-summer, i n each o f s e v e r a l l a k e zones c l a s s i f i e d a c c o r d i n g t o the scheme o f Runka & Lewis ( 1 9 8 1 ) . B r a u n - B l a n q u e t c l a s s e s o f c o v e r : + = 0 - 1 % 3 = 2 5 - 5 0 % 1 = 1 - 5 % 4 = 5 0 - 7 5 % 2 = 5 - 2 5 % 5 = 7 5 - 1 0 0 % Lake z o n e s : SOW = Sh a l l o w open water MAR = Marsh LAKE 1 (Box 2 7 ) zone S p e c i e s SOW 1 MAR 1 D r e p a n o c l a d u s s p . 2 Potamogeton n a t a n s 3 2 Polygonum amphibium + + S a g i t t a r i a c u n e a t a 1 Sparganium sp. + U t r i c u l a r i a v u l g a r i s + Carex r o s t r a t a + E l e o c h a r i s p a l u s t r i s 1 G l y c e r i a b o r e a l i s 2 A r e a (m 2) 1 1 1 6 0 1 0 8 6 8 LAKE 2 ( B a r k l e y L.) zone S p e c i e s SOW 1 MAR 1 C e r a t o p h y l l u m demersum 1 F i l a m e n t o u s a l g a e + Lemna mi nor + + Myriophyl 1um e x a l b e s c e n s 4 Potamogeton r i c h a r d s o n i + V_. p u s i l l u s / b e r c h t o l d i 2 P_. p e c t i n a t u s 2 Polygonum amphibium 1 Beckmannia s z y i g a c h n e 1 E l e o c h a r i s p a l u s t r i s 2 J u n c u s b a l t i c u s + Sc i r p u s l a c u s t r i s 2 Area (m 2) 2 5 1 7 3 3 8 8 5 LAKE 3 (Near O p p o s i t e C r e s c e n t ) LAKE 4 (Rock L.) S p e c i e s SOW 1 zone SOW 2 MAR 1 S p e c i e s SOW s zone SOW 1 SOW 2 MAR 1 Aphanozomenon f l o s a q u a t i s 2 F i l a m e n t o u s a l g a e sp 2 2 F i l a m e n t o u s a l g a e s p . + Potamogeton p e c t i n a t u s + 3 + M y r i o p h y l l u m e x a l b e s c e n s + Ruppia o c c i d e n t a l i s 4 2 4 Potamogeton p e c t i n a t u s 3 J u n c u s b a l t i c u s + P. p u s i l l u s / b e r c h t o l d i 1 S c i r p u s l a c u s t r i s 3 Carex l a n u g i n o s a + S. americanus 1 C. a t h e r o d e s + E l e o c h a r i s p a l u s t r i s 1 A r e a (m 2) 5 5 1 6 1 2 2 0 8 2 3 7 2 2 9 1 6 7 8 2 J u n c u s b a l t i c u s S c i r p u s l a c u s t r i s A rea (m 2) 4 6 7 0 1 8 7 8 4 2 3 1 4 4 4 189 APPENDIX F CONT. LAKE 5 ( J a c k s o n L.) LAKE 6 ( L . Lye) zone S p e c i e s SOW S SOW 1 SOW 2 MAR 1 S p e c i e s SOW S SOW 1 MAR 1 Aphanozomenon f l o s a q u a t i s F i l a m e n t o u s a l g a e sp 3 Potamogeton p e c t i n a t u s 1 Ruppia o c c i d e n t a l i s 1 J u n c u s b a l t i c u s  S c i r p u s l a c u s t r i s F i l a m e n t o u s a l g a e s p . J u n c u s b a l t i c u s  S c i r p u s l a c u s t r i s A r e a (m 2) 1 1 2 + 10638 334292 2131 Ar e a (m 2) 641 26866 28890 1116 LAKE 7 (Round-Up L.) LAKE 8 ( B a r n e s L.) zone zone S p e c i e s SOW S SOW 1 S p e c i e s SOW S SOW 1 SOW 2 MAR 1 Ruppia o c c i d e n t a l i s 2 2 Ar e a (m 2) 408 220888 D i s t i c h l i s s t r i c t a 2 Hordeum jubatum + J u n c u s b a l t i c u s 3 S c i r p u s l a c u s t r i s + A r e a (m 2) 8632 18834 150516 3362 190 APPENDIX G P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between a q u a t i c macrophyte community p a r a m e t e r s . See t e x t f o r e x p l a n a t i o n o f s y m b o l s . community parameter s % c o v e r H' ( s ) H ' ( z ) H1 ' z ( s ) H ' ( f ) H ' f ( s ) Qj Qd k 2 5 - . 7 9 1 - . 6 7 8 - . 7 2 0 - . 0 2 5 - . 9 1 3 - . 4 7 8 - . 6 2 5 - . 8 2 5 .782 l o g k 2 5 - . 6 8 9 - . 1 6 9 - . 7 1 5 - . 1 9 4 - . 8 1 0 - . 8 3 0 - . 3 8 0 - . 6 9 4 .847 PCI - . 7 6 8 - . 6 4 6 - . 7 3 4 - . 0 5 1 - . 8 6 3 - . 4 1 1 - . 6 5 2 - . 7 5 7 .730 PC2 - . 0 6 7 - . 1 0 1 .041 .550 - . 3 6 5 - . 2 5 7 .355 .078 - . 0 2 5 z - . 8 4 8 - . 7 6 6 - . 9 1 1 - . 4 0 8 - . 8 3 8 - . 6 1 2 - . 8 0 2 - . 8 4 8 .910 D L A .763 .458 .797 .366 .602 .460 .635 .764 - . 7 9 5 191 APPENDIX H P e a r s o n ' s product-moment c o r r e l a t i o n c o e f f i c i e n t s between f l o r a l and f a u n a l community parameter See T a b l e 6 f o r d e s c r i p t i o n o f symbols. P l a n t Community Faunal Community parameter Parameter D s t i H'(s) H ' ( t ) H ' ( t i ) H ' t ( s ) H ' t ( i ) H ' t i ( s ) Q j ( s ) Q j ( t i ) Q d ( s ) Q d ( t i ) WATER BOTTLE - ZOOPLANKTON s -.393 .537 .442 .173 .639 .177 -.185 -.322 .144 .537 .442 -.214 .086 c .357 .762 .759 .773 .568 .748 .602 .509 .740 .421 .463 -.361 -.348 H ' ( S ) -.341 .621 .540 .277 .652 .290 -.054 -.183 .215 .621 .540 -.330 -.004 H'(z) -.100 .285 .383 .061 .094 .052 .020 -.009 .077 .286 .383 -.260 -.005 H ' z ( s ) -.237 .642 .453 .351 .726 .344 -.004 -.180 .327 .642 .453 -.403 -.115 H ' ( f ) -.528 .395 .138 .115 .222 .166 .008 .024 -.016 .395 .138 -.414 .094 H ' f ( s ) .085 .648 .753 .342 .701 .283 .002 -.234 -.411 .649 .753 -.343 -.262 Qj -.392 .537 .442 .173 .635 .175 -.191 -.328 .144 .535 .436 -.215 .088 Qd .384 -.659 -.477 -.378 -.694 -.423 -.056 .043 -.224 -.659 -.477 .391 .028 p -.033 .724 .639 .346 .841 .289 -.132 -.417 .438 .765 .758 -.384 -.280 SWEEP - COLEOPTERA s .709 .527 .615 .277 .438 .333 .286 .256 .006 .527 .615 -.606 -.626 c .714 -.051 -.018 -.192 -.221 -.275 .002 -.253 .072 -.027 .179 -.342 -.641 H'(s) .699 .395 .609 .240 .347 .343 .270 .295 -.090 .395 .609 -.613 -.683 H'(z) -.025 .072 .522 .313 .165 .506 .381 .541 -.219 .072 .522 -.170 -.253 H ' z ( s ) .665 .385 .364 .003 .264 -.026 .022 -.111 .052 .385 .364 -.520 -.445 H ' ( f ) .262 .282 .540 .122 .343 .246 .032 .183 -.172 .282 .540 -.491 -.308 H ' f ( s ) .488 .261 .458 .211 .170 .262 .372 .255 -.010 .261 .458 -.328 -.479 Qj .709 .527 .614 .276 .437 .332 .285 .255 .005 .536 .619 -.606 -.616 Qd -.827 -.286 -.435 -.057 -.263 -.122 -.034 -.062 .091 -.286 -.434 .693 .731 P .593 .293 .287 -.009 .234 -.061 .068 -.143 .086 .293 .287 -.365 -.376 SWEEP - HEMIPTERA s -.241 .739 .697 .685 .809 -.438 .738 .697 -.625 -.845 c -.379 .450 .521 .289 .569 -.629 .180 .413 -.413 -.697 ri'(s) -.160 .609 .629 .761 .827 -.345 .609 .629 -.631 -.838 H'(z) .331 -.081 .207 .407 .307 .081 .081 ,.208 -.111 -.257 H ' z ( s ) -.450 .736 .683 .585 .786 -.559 .736 .683 -.615 -.729 H ' ( f ) -.007 .307 .349 .744 .598 .076 .307 .350 -.678 -.492 H ' f ( s ) -.166 .475 .659 .417 .662 -.597 .475 .659 -.215 -.639 Qj -.242 .739 .697 .684 .809 -.439 .744 .703 -.627 -.841 Qd .299 -.621 -.509 -.841 -.855 .266 -.622 -.509 .765 .822 p -.567 .666 .646 .468 .780 -.742 .697 .681 -.258 -.576 Appendix H CONT. 192 P l a n t Community Fa u n a l Community parameter P a r a m e t e r D s t i H'(s) H ' ( t ) H ' ( t i ) H ' t ( s ) H ' t ( i ) H ' t 1 ( s ) Q j ( s ) Q j ( t i ) Q d ( s ) Q d ( t i ) LIGHT TRAP - ALL SPECIES s .099 .630 .687 -.128 .397 - .148 -.415 -.468 .099 .630 .687 -.569 -.408 c -.054 .535 .710 .201 .227 .156 .126 .058 .554 .286 .377 -.342 -.471 H ' ( S ) -.049 .659 .702 .113 .592 .098 -.217 -.267 .212 .659 .702 -.666 -.521 H'(z) -.121 .100 .110 .522 .639 .538 .297 .296 .195 .100 .111 -.312 -.432 H ' z ( s ) .142 .776 .830 -.191 .308 - .231 -.443 -.520 .255 .776 .829 -.690 -.519 H ' ( f ) -.200 .725 .579 .205 .761 .198 -.200 -.247 .199 .726 .578 -.754 -.520 H ' f ( s ) .204 .339 .530 .124 .320 .101 -.034 -.080 .296 .338 .531 -.425 -.549 Qj .100 .630 .687 -.129 .396 - .149 -.416 -.468 .099 .634 .689 -.571 -.408 Qd .247 -.834 -.817 -.117 -.638 - .101 .241 .296 -.228 -.834 -.817 .786 .486 P .301 .560 .751 -.225 .154 - .259 -.392 -.453 .170 .559 .751 -.544 -.502 LIGHT TRAP - ENTOMOSTRACA s .099 .630 .609 -.128 -.860 - .148 .067 .147 -.122 .719 .667 -.181 .049 c -.054 .825 .642 .178 -.383 .282 .744 .687 .190 .649 .662 -.512 -.455 H'(s) -.058 .686 .607 -.172 -.770 - .245 .241 .281 .041 .687 .701 -.241 .021 H'(z) -.138 .076 .170 .354 -.147 .200 .465 .307 .536 .076 .288 -.195 .047 H ' z ( s ) .144 .849 .671 -.416 -.866 - .388 .032 .199 -.319 .849 .699 -.308 -.088 H ' ( f ) -.203 .395 .204 -.194 -.344 - .296 -.014 -.057 .084 .396 .257 -.005 .407 H ' f ( s ) .193 .671 .729 .046 -.805 .011 .495 .560 -.109 .670 .829 -.519 -.388 Qj .094 .718 .608 -.380 -.863 - .438 .055 .138 -.123 .719 .663 -.177 .055 Qd .249 -.683 -.557 .214 .666 .227 -.137 -.227 .109 -.684 -.648 .153 .080 p .302 .762 .757 -.315 -.941 - .229 .181 .410 -.374 .761 .840 -.455 -.367 LIGHT TRAP - COLEOPTERA s -.234 .490 .498 .487 .659 .444 .268 .175 .554 .491 .498 -.452 -.654 c -.349 .369 .405 .237 .403 .189 .080 -.011 .406 .120 .078 -.150 -.465 H'(s) -.075 .500 .487 .464 .639 .413 .249 .154 .581 .500 .487 -.523 -.673 H'(z) .501 -.079 -.097 .049 .318 .061 -.126 -.115 -.028 -.079 -.097 -.132 -.067 H ' z ( s ) -.512 .634 .652 .607 .661 .561 .431 .343 .653 .635 .652 -.582 -.776 H ' ( f ) .002 .630 .557 .645 .474 .601 .596 .558 .664 .631 .557 -.741 -.570 H ' f ( s ) -.075 .090 .153 .172 .639 .170 -.151 -.205 .133 .091 .153 -.144 -.438 Qj -.234 .490 .498 .486 .659 .443 .267 .174 .554 .495 .504 -.456 -.655 Qd .202 -.755 -.712 -.588 -.563 - .504 -.465 -.344 -.835 -.756 -.713 .737 .824 P -.529 .373 .467 .403 .807 .387 .063 -.013 .357 .373 .466 -.340 -.614 LIGHT TRAP - HEMIPTERA s -.311 .738 .757 .332 .879 -.568 .738 .757 -.738 -.424 c -.072 .782 .684 .130 .679 -.538 .525 .314 -.773 -.450 H ' ( S ) -.259 .716 .695 .301 .864 -.578 .716 .694 -.683 -.349 H'(z) .153 -.047 .141 -.280 .250 -.457 -.047 .140 -.034 -.042 H ' z ( s ) -.382 .880 .810 .438 .884 -.488 .880 .810 -.691 -.444 H ' ( f ) -.316 .513 .334 .485 .541 -.128 .513 .334 -.086 .119 H ' f ( s ) -.009 .487 .745 -.198 .760 -.873 .487 .745 -.719 -.626 Qj -.311 .738 .757 .332 .880 -.569 .739 .760 -.729 -.421 Qd .429 -.870 -.632 -.600 - .859 .338 -.870 -.633 .624 .168 p -.369 .706 .923 .068 .945 -.838 .706 .922 -.692 -.597 

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