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An ecological study of some of the chironomidae inhabiting a series of saline lakes in central British… Cannings, Robert Alexander 1973

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AN ECOLOGICAL STUDY OF SOME OF THE CHIRONOMIDAE INHABITING A SERIES OF SALINE LAKES IN CENTRAL BRITISH COLUMBIA WITH SPECIAL REFERENCE TO CHIRONOMUS TENTANS FABRICIUS by Robert A l e x a n d e r  Cannings  BSc. Hons., U n i v e r s i t y o f B r i t i s h Columbia, 1970  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n t h e 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 t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA May, 1973  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r  an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y  a v a i l a b l e f o r r e f e r e n c e and  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e f o r s c h o l a r l y purposes may by h i s r e p r e s e n t a t i v e s .  study.  c o p y i n g of t h i s  be g r a n t e d by the Head of my  Department or  I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n  of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t written permission.  Department o f The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  Date  thesis  my  ii ABSTRACT  T h i s t h e s i s i s concerned w i t h a study o f the Chironomidae o c c u r i n g B r i t i s h Columbia. of s p e c i e s ,  i n a s a l i n e lake series i n c e n t r a l  I t describes  the e c o l o g i c a l d i s t r i b u t i o n  t h e i r abundance, phenology and i n t e r a c t i o n , w i t h  p a r t i c u l a r a t t e n t i o n b e i n g p a i d t o Chironomus t e n t a n s . Emphasis i s p l a c e d on the s p e c i e s  o f Chironomus t h a t  coexist  i n t h e s e l a k e s and a f u r t h e r a n a l y s i s i s made o f the chromosome i n v e r s i o n f r e q u e n c i e s i n C. t e n t a n s . Of the t h i r t y - f o u r s p e c i e s  r e p r e s e n t e d by i d e n t i f i a b l e  a d u l t s i n the s t u d y , e l e v e n s p e c i e s have n o t been reported and  previously  i n B r i t i s h Columbia, f i v e a r e new r e c o r d s f o r Canada  seven s p e c i e s  a r e new t o s c i e n c e .  The c h i r o n o m i d f a u n a o f the l a k e s e r i e s i s d i v i d e d dominant a s s o c i a t i o n s whose e x i s t e n c e s a l i n i t y and p r o d u c t i v i t y l e v e l s . Procladius  while  seems t o depend on  A Cricotopus albanus -  b e l l u s - Ablabesmyia p e l e e n s i s  v a i l s i n the l o w e s t s a l i n i t i e s  into  association  pre-  (40 t o 80 jumho/cm c o n d u c t i v i t y )  i n c o n d u c t i v i t i e s between 400 and 2800 jumho/cm a  G l y p t o t e n d i p e s b a r b i p e s - E i n f e l d i a pagana a s s o c i a t i o n dominates.  I n the most s a l i n e l a k e s  jumho/cm) a C a l o p s e c t r a  ( c o n d u c t i v i t y 4100 t o 12000  g r a c i l e n t a - Cryptotendipes a r i e l  association i s characteristic. A n a l y s i s o f p h y s i c a l and c h e m i c a l f a c t o r s i n f l u e n c i n g t h e l i f e c y c l e o f C. t e n t a n s i n d i c a t e s t h a t c o n d i t i o n s  associated  w i t h h i g h l e v e l s o f o r g a n i c carbon promote l a r g e numbers o f l a r v a e and g r e a t e r emergence s u c c e s s .  The r e s u l t s  suggest  t h a t c o m p e t i t i o n between C. t e n t a n s and o t h e r Chironomus species i s reduced  through  s p a t i a l s e p a r a t i o n due t o d i f f e r e n t  preferences f o r s a l i n i t y or r e l a t e d factors. temporal  Furthermore,  s e p a r a t i o n among these and o t h e r abundant s p e c i e s  such as G. b a r b i p e s and E. pagana o c c u r s as a r e s u l t o f staggered generation times. The i n v e r s i o n f r e q u e n c y  i n chromosome 1 o f C. t e n t a n s 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 o r g a n i c c a r b o n l e v e l s and p o s i t i v e l y c o r r e l a t e d w i t h d i s s o l v e d oxygen and the abundance o f Glyptotendipes barbipes.  Since the i n v e r s i o n frequency i s  l o w e s t i n h a b i t a t s where competing s p e c i e s a r e few and where C. t e n t a n s i s most s u c c e s s f u l , i t i s suggested  that the i n v e r -  s i o n governs a mechanism r e d u c i n g c o m p e t i t i o n . A major c o n t r i b u t i o n o f t h i s work i s t h e r e v i s i o n o f t h e d i s t r i b u t i o n o f many o f t h e c h i r o n o m i d tion.  s p e c i e s under c o n s i d e r a -  I n t h e p a s t , l i t t l e r e s e a r c h has been done on p o p u l a -  t i o n s of chironomids  i n a saline lake series.  study, i n attempting to f i l l  The p r e s e n t  t h i s gap i n e n t o m o l o g i c a l r e s e a r c h ,  shows t h a t a s p e c i e s ' l i f e h i s t o r y and p o p u l a t i o n s t r u c t u r e can v a r y r a d i c a l l y i n c l o s e l y a s s o c i a t e d l a k e s o f d i f f e r i n g c h e m i c a l and b i o l o g i c a l  constitution.  IV  TABLE OF CONTENTS Page T i t l e Page  i  Abstract  ii  T a b l e of C o n t e n t s  iv  L i s t of Tables  vi  L i s t of Figures  viii  L i s t of Plates  xi  Acknowledgements  xii  I  INTRODUCTION  1  II  THE LAKE ENVIRONMENTS  4  A.  THE  4  B.  THE PHYSICAL AND OF THE LAKES  III  STUDY AREA CHEMICAL PROPERTIES  8  SPECIES DIVERSITY AND THE CHIRONOMID COMPLEX IN THE LAKE SERIES  17  A.  MATERIALS AND METHODS  17  1. 2.  Temperature Records B i o l o g i c a l Sampling Methods a) L a r v a l Sampling b) A d u l t Sampling  17 17 17 19  3. 4.  R e a r i n g o f Specimens P r e p a r a t i o n and I d e n t i f i c a t i o n of Specimens A n a l y s i s o f the Data S t o r a g e o f the Data f o r F u r t h e r Study  23  5. 6.  B.  24 24 24  RESULTS  26  1. 2. 3  26 30  Water Temperatures i n the Lake S e r i e s Chemical Data The O c c u r r e n c e o f S p e c i e s i n the Lakes  30  4. 5.  Species Considered i n D e t a i l The Chironomid Complex and t h e Lake S e r i e s a) b) c)  C.  85  85 86 88  DISCUSSION 1. 2.  The Chironomidae and the Lake S e r i e s Chironomus t e n t a n s and the Lake Series a) b)  IV  The C r i c o t o p u s a l b a n u s P r o c l a d i u s b e l l u s - Ablabesmyia peleensis association The G l y p t o t e n d i p e s b a r b i p e s E i n f e l d i a pagana a s s o c i a t i o n The C a l o p s e c t r a g r a c i l e n t a Cryptotendipes a r i e l association  33  P h y s i c a l and Chemical Influences Biotic Interactions  91 102 102 106  CHIRONOMUS TENTANS AND SOME BIOTIC FACTORS AFFECTING CHROMOSOME INVERSION  113  A.  MATERIALS AND METHODS  113  B.  RESULTS  115  C.  DISCUSSION  121  r  V  CONCLUSION  Literature Appendix  Cited  125 129 140  vi LIST OF TABLES Page TABLE I  P h y s i c a l and c h e m i c a l of t h e l a k e s .  TABLE I I  Average w a t e r temperature lake series.  properties i n the  TABLE I I I The d i s t r i b u t i o n o f c h i r o n o m i d s i n t h e one meter depth zone i n the l a k e s .  10 27  31  TABLE I V  The d i s t r i b u t i o n o f l a r v a e u n i d e n t i f i e d to species.  32  TABLE V  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and t h e amount o f emergence o f c e r t a i n s p e c i e s .  76  The c o r r e l a t i o n between emergence h i s t o g r a m d i s p e r s i o n and e n v i r o n m e n t a l factors.  77  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g r e l a t i o n s h i p s between e n v i r o n m e n t a l f a c t o r s and s p e c i e s abundance.  78  TABLE V I I I Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and s p e c i e s per c e n t c o m p o s i t i o n .  79  TABLE V I  TABLE V I I  TABLE IX  TABLE X  TABLE X I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and t h e amount of emergence.  80  Summary o f t h e c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and t h e number of emergence peaks f o r v a r i o u s s p e c i e s .  81  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and t h e times o f m a j o r emergence i n s e v e r a l s p e c i e s .  82  VIX  TABLE X I I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between l a r v a l abundance, numbers o f emerging a d u l t s , number o f emergence peaks and emergence time.  83  The d e v e l o p m e n t a l r a t e s o f C. t e n t a n s i n various lakes.  84  The p e r c e n t a g e c o m p o s i t i o n o f s p e c i e s i n t h e l a k e s based on t h e t o t a l a d u l t emergence, May - August, 1970.  90  TABLE XV  I n v e r s i o n f r e q u e n c i e s i n chromosome 1 of C. t e n t a n s .  116  TABLE XVI  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and some environmental f a c t o r s .  117  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and the abundance o f some c h i r o n o m i d s .  118  TABLE X I I I TABLE XIV  TABLE X V I I  TABLE X V I I I Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and t h e p e r c e n t c o m p o s i t i o n o f some c h i r o n o m i d s , TABLE X I X  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and some emergence v a r i a b l e s .  119  120  viii LIST OF FIGURES Page FIGURE 1  The s t u d y a r e a ; Springhouse r e g i o n .  5  FIGURE 2  The s t u d y a r e a ; w a t e r b o d i e s i n the Chilcotin region.  6  FIGURE 3  D e t a i l s o f t h e emergence t r a p .  22  FIGURE 4  D a i l y temperature range i n some o f the l a k e s where Chironomus t e n t a n s i s abundant.  28  C u m u l a t i v e day degrees measured a t the mud s u r f a c e a t a depth o f 1 meter i n some o f the l a k e s where Chironomus t e n t a n s i s abundant.  29  The emergence o f a d u l t s o f P r o c l a d i u s b e l l u s (Loew) and P r o c l a d i u s f r e e m a n i S u b l e t t e from t h e one meter depth zone o f s e v e r a l l a k e s .  35  The emergence o f a d u l t s o f P r o c l a d i u s dentus Roback from the one meter depth zone o f s e v e r a l l a k e s .  37  The emergence o f a d u l t s o f P r o c l a d i u s c l a v u s Roback and A b l a b e s m y i a p e l e e n s i s ( W h a l l e y ) from the one meter depth zone o f s e v e r a l l a k e s .  40  The emergence o f a d u l t s o f C r i c o t o p u s f l a v i b a s i s M a l l o c h and C r i c o t o p u s a l b a n u s C u r r a n from the one meter depth zone o f s e v e r a l l a k e s .  43  The emergence o f a d u l t s o f P s e c t r o c l a d i u s barbimanus (Edwards) from the one meter depth zone o f several lakes.  45  The emergence of a d u l t s o f C r y p t o t e n d i p e s a r i e l ( S u b l e t t e ) and C a l o p s e c t r a g r a c i l e n t a (Holmgren) from the one meter depth zone o f several lakes.  47  FIGURE 5  FIGURE 6  FIGURE 7  FIGURE 8  FIGURE 9  FIGURE 10  FIGURE 11  ix FIGURE 12  FIGURE 13  FIGURE 14  FIGURE 15  FIGURE 16  FIGURE 17  FIGURE 18  FIGURE 19  FIGURE 20  FIGURE 21  FIGURE 22  FIGURE 23  L a r v a l abundance and a d u l t emergence of Perotanypus a l a s k e n s i s ( M a l l o c h ) i n L. L y e , B o i t a n o L. and L. J a c k s o n .  50  L a r v a l abundance and a d u l t emergence of Derotanypus a l a s k e n s i s ( M a l l o c h ) i n Rock L., Sorenson L. and E a s t L.  51  L a r v a l abundance and a d u l t emergence of E i n f e l d i a pagana Meigen i n L. J a c k s o n , Rock L. and W e s t w i c k L.  55  L a r v a l abundance and a d u l t emergence of E i n f e l d i a pagana Meigen i n Near O p p o s i t e C r e s c e n t , B a r k l e y L. and E a s t L.  56  L a r v a l abundance and a d u l t emergence of G l y p t o t e n d i p e s b a r b i p e s ( S t a e g e r ) i n L. J a c k s o n , Westwick L. and Sorenson L.  58  L a r v a l abundance and a d u l t emergence of G l y p t o t e n d i p e s b a r b i p e s ( S t a e g e r ) i n Rock L., B a r k l e y L. and E a s t L.  59  L a r v a l abundance and a d u l t emergence of Chironomus a n t h r a c i n u s Z e t t e r s t e d t i n B o i t a n o L., L. J a c k s o n and Rock L.  62  L a r v a l abundance and a d u l t emergence o f Chironomus a n t h r a c i n u s Z e t t e r s t e d t i n Sorenson L., B a r k l e y L. and E a s t L.  63  L a r v a l abundance and a d u l t emergence o f Chironomus n.sp. i n Barnes L., B o i t a n o L. and L. J a c k s o n  66  L a r v a l abundance and a d u l t emergence of Chironomus n.sp. i n Rock L. and Sorenson L.  67  L a r v a l abundance and a d u l t emergence of Chironomus n.sp. i n B a r k l e y L. and E a s t L.  68  L a r v a l abundance and a d u l t emergence of Chironomus t e n t a n s F a b r i c i u s i n L. J a c k s o n , Westwick L. and Sorenson L.  74  FIGURE 24  L a r v a l abundance and a d u l t emergence of Chironomus t e n t a n s F a b r i c i u s i n Rock L., B a r k l e y L. and E a s t L.  FIGURE 25  C h i r o n o m i d l a r v a l biomass and i n d e x o f d i v e r s i t y f o r t h e l a r v a l complexes a t 1.0 m i n the l a k e s e r i e s  FIGURE 26  Graph showing t h e r e l a t i o n s h i p between . oxygen l e v e l s and o r g a n i c c a r b o n i n the l a k e s .  FIGURE 27  S a l i n i t y tolerances of the i d e n t i f i e d s p e c i e s o f the one meter depth zone i n the lake s e r i e s .  FIGURE 28  Examples o f t h e s p a c i n g o f emergence times o f Chironomus t e n t a n s and t h r e e coexisting species.  FIGURE 29  Seasonal v a r i a t i o n i n the f r e q u e n c i e s o f i n v e r s i o n s o f chromosome 1.  LIST OF PLATES  Page PLATE 1 A B  PLATE 2 A B  PLATE 3 A B  PLATE 4 A B  PLATE 5 A B  PLATE 6 A B  PLATE 7  11  Box 27 Box 27; v e g e t a t i o n  12  B a r k l e y L. B a r k l e y L.; M y r i o p h y l l u m  13  Near P h a l a r o p e Near O p p o s i t e C r e s c e n t  14  L. Greer L. J a c k s o n  15  L. Lye Round-up L.  16  Barnes L. Barnes L.; p r e c i p i t a t e d  The emergence t r a p  salts  21  xii ACKNOWLEDGEMENTS  I t i s a p l e a s u r e t o express my g r a t i t u d e t o P r o f e s s o r G.G.E. Scudder who, as my r e s e a r c h s u p e r v i s o r , g u i d e d me t h r o u g h t h i s work. The time and energy he spent a r e much appreciated. Dr. T.G. N o r t h c o t e s c r i t i c i s m was i n v a l u a b l e d u r i n g t h e w r i t i n g o f t h e t h e s i s . I a l s o thank Dr. A.B. A c t o n f o r r e a d i n g the m a n u s c r i p t . Dr. M.S. Topping, whose PhD. t h e s i s s e r v e d as the b a s i s f o r t h e p r e s e n t s t u d y , i s e s p e c i a l l y thanked f o r h i s e n t h u s i a s m , support and p e r m i s s i o n t o u s e much o f h i s unpubl i s h e d data. 1  G l e n Jamieson, Tony Dixon and Ken Bowler somehow put up w i t h my innumerable q u e s t i o n s about computer programming. W i t h o u t t h e i r h e l p t h e d a t a a n a l y s i s w o u l d have resembled an i n f i n i t e l o o p , o r w o r s e , w o u l d have c r a s h e d t h e system. J u l i a n R e y n o l d s , i n between s n i c k e r s , d i d a l l s o r t s o f things to help. I am i n d e b t e d t o Dr. J.E. S u b l e t t e ( E a s t e r n New Mexico U n i v e r s i t y ) and Dr. D.R. O l i v e r (Canada A g r i c u l t u r e , Ottawa) f o r t h e i r help w i t h the determinations. Dr. A.M. Hutson ( B r i t i s h Museum: N a t u r a l H i s t o r y ) k i n d l y s u p p l i e d a u t h e n t i c specimens o f E i n f e l d i a pagana and P s e c t r o c l a d i u s barbimanus f o r i d e n t i f i c a t i o n purposes. The r e s e a r c h was c a r r i e d o u t w h i l e i n r e c e i p t o f a N a t i o n a l Research C o u n c i l o f Canada P o s t g r a d u a t e S c h o l a r s h i p and was f u r t h e r a i d e d through an NRC g r a n t t o Dr. Scudder.  ERRATA 1.  Where " A p h a n o z o m e n o n "  2.  Page 2 6 , "31°  l i n e 18.  i n Barkley  appears,  read  "Aphanizomenon".  "31° i n L. Jackson" should L.".  3.  Page 6 1 ,  l i n e 15.  " u n i v o l t i v e " should read  4.  Page 8 8 ,  l i n e 17.  "12000  5.  Page 1 0 2 , l i n e "no r e a l  6.  Page 1 2 6 ,  18.  read  "univoltine".  umho/cm".  "not r e a l  trend" should  "eighteen  s p e c i e s new t o  read  trend". l i n e 2.  B.C.,  t w e l v e s p e c i e s new t o Canada and s e v e n s p e c i e s to  science".  new  1 I  INTRODUCTION T h i s t h e s i s i s an e c o l o g i c a l study o f some o f the  Chironomidae i n h a b i t i n g a s a l i n e l a k e s e r i e s i n the C h i l c o t i n and C a r i b o o r e g i o n s of B r i t i s h Columbia.  The  complex of a s a l i n e l a k e s e r i e s has n e v e r been examined b e f o r e .  chironomid thoroughly  Rawson and Moore (1944) and L a u e r  have mentioned c h i r o n o m i d s  (1969)  i n c o n n e c t i o n w i t h work on  w a t e r s , and o t h e r s have r e c o r d e d and  saline  studied various species  i n w a t e r s o f d i f f e r i n g s a l i n i t i e s throughout the w o r l d (Remmert, 1955;  S u t c l i f f e , 1960;  Palmen, 1962;  Bayly  and  W i l l i a m s , 1966), but l i t t l e i n f o r m a t i o n has been g a t h e r e d how  chironomid  varying  on  p o p u l a t i o n s d i f f e r i n a s e r i e s of l a k e s of  salinity.  T h i s type of study i s p a r t i c u l a r l y i n t e r e s t i n g s i n c e i t i s w e l l known t h a t c h i r o n o m i d s  d i s p l a y e x t e n s i v e a d a p t a t i o n to  a wide v a r i e t y o f environments (Thienemann, 1954;  Brundin,  and a r e o f t e n a b l e to t h r i v e where many o t h e r a n i m a l s  1966)  cannot.  The b r o a d s a l i n i t y t o l e r a n c e of the Chironomidae g i v e s them s p e c i a l prominence i n s a l i n e h a b i t a t s .  T h i s f a c t , i n con-  j u n c t i o n w i t h t h e i r u s u a l g r e a t abundance and wide d i v e r s i t y , makes c h i r o n o m i d s  u s e f u l organisms w i t h w h i c h to study changes  i n the s t r u c t u r e of s p e c i e s complexes t h a t o c c u r w i t h v a r i a t i o n s i n 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 c o n d i t i o n s . The  d a t a o b t a i n e d by Topping (1969) on t h i s l a k e s e r i e s  i n c e n t r a l B r i t i s h Columbia showed t h a t i n the d i p t e r a n  2 Chironomus t e n t a n s F a b r i c i u s t h e r e was a s i g n i f i c a n t c o r r e l a t i o n between the f r e q u e n c y o f l a r v a l chromosome i n v e r s i o n 1 Rad and the t o t a l number o f o t h e r c h i r o n o m i d s p r e s e n t i n the habitat.  S i n c e the s e l e c t i v e v a l u e o f i n v e r s i o n s  i n w i l d pop-  u l a t i o n s i s n o t c l e a r l y u n d e r s t o o d , and as t h e r e have been few c o r r e l a t i o n s of t h i s s o r t , f u r t h e r i n v e s t i g a t i o n o f t h i s problem  i s considered  valuable.  A l t h o u g h Topping was a b l e t o show t h i s c o r r e l a t i o n between i n v e r s i o n f r e q u e n c y and l a r v a l abundance, most emphasis was p l a c e d on the c h e m i c a l c o m p o s i t i o n o f the environments and l i t t l e a t t e n t i o n was d i r e c t e d t o the b i o t i c f a c t o r s  involved.  Thus, one o f the main aims o f t h i s t h e s i s was t o a s c e r t a i n the e f f e c t s o f some b i o t i c f a c t o r s on the abundance o f Chironomus t e n t a n s and the i m p l i c a t i o n s o f these f a c t o r s on the r e g u l a t i o n of i n v e r s i o n f r e q u e n c y . In p a r t i c u l a r , i t was c o n s i d e r e d n e c e s s a r y t o know more about the o t h e r c h i r o n o m i d s p e c i e s  t h a t c o e x i s t w i t h C. t e n t a n s  i n t h i s l a k e s e r i e s , t h e i r numbers and t h e i r l i f e characteristics.  cycle  Only a f t e r d e t e r m i n i n g the v a r i a t i o n s i n the  s t r u c t u r e of the c h i r o n o m i d complex throughout the l a k e is i t possible perspective species  series  t o p l a c e the p o p u l a t i o n s o f C. t e n t a n s i n p r o p e r  and t o i n v e s t i g a t e the i n f l u e n c e o f the v a r i o u s  on C. t e n t a n s .  I n i t i a l l y , a t t e n t i o n i s d i r e c t e d t o the l a k e environments t h e m s e l v e s ; t h e i r p h y s i c a l and c h e m i c a l c h a r a c t e r i s t i c s a r e outlined.  This information,  i n conjunction  with  extensive  3 d a t a c o l l e c t e d on l a r v a l numbers and emergence p a t t e r n s , i s u s e d i n an e x a m i n a t i o n o f the major s p e c i e s of the one meter depth zone.  Questions  such as the e f f e c t o f l a k e  environments  on the d i s t r i b u t i o n and phenology o f these s p e c i e s a r e d i s cussed as a r e the p o s s i b l e i n t e r a c t i o n s between the more dominant species present. The p h y s i c a l and c h e m i c a l d a t a a r e then i n t e g r a t e d w i t h i n f o r m a t i o n on c h i r o n o m i d s and thus a d e s c r i p t i o n of a number o f s p e c i e s a s s o c i a t i o n s i s advanced.  These a s s o c i a t i o n s , v a r y -  i n g throughout  form the b a s i s f o r the  the l a k e environments,  e x a m i n a t i o n o f the r e l a t i o n s h i p between C. t e n t a n s and  the  other species. W i t h these d a t a a t hand the p o t e n t i a l e f f e c t o f the b i o t i c f a c t o r s on the chromosome i n v e r s i o n f r e q u e n c y i n C. may  be more c l o s e l y a n a l y z e d .  c a l c u l a t e d t o determine  tentans  C o r r e l a t i o n c o e f f i c i e n t s are  the types o f i n t e r a c t i o n s t h a t may  prove i m p o r t a n t I n t h i s r e s p e c t . A p a r t i c u l a r l y i n t e r e s t i n g problem  t h a t a r i s e s from  study o f i n t e r s p e c i f i c i n t e r a c t i o n s i s the apparent  the  coexistence  w i t h C. t e n t a n s o f two o t h e r v e r y s i m i l a r Chironomus s p e c i e s , C. a n t h r a c i n u s Z e t t e r s t e d t and C ^ n . s p . (near a t r i t i b i a M a l l o c h ) . A t t e n t i o n i s f o c u s s e d on t h i s c o n g e n e r i c i n t e r a c t i o n and comp e t i t i v e e x c l u s i o n ( H a r d i n , 1960)  i s discussed i n t h i s context.  4 II  THE LAKE ENVIRONMENTS  A.  THE STUDY AREA The study was u n d e r t a k e n i n t h e C a r i b o o and C h i l c o t i n  a r e a s o f c e n t r a l B r i t i s h Columbia.  The f i f t e e n w a t e r b o d i e s  examined a r e s i t u a t e d i n two d i s t i n c t b u t a d j a c e n t a r e a s : the S p r i n g h o u s e a r e a southwest o f W i l l i a m s Lake e a s t o f t h e F r a s e r R i v e r ; and Becher's P r a i r i e n e a r R i s k e Creek on t h e w e s t e r n ( C h i l c o t i n ) s i d e o f t h e F r a s e r ( F i g s . 1, 2 ) . Those named as l a k e s can be found on maps w h i l e t h e o t h e r s have names used f o r t h e convenience o f z o o l o g i s t s . include:  a ) Springhouse a r e a :  and B o i t a n o Lake Lake  Sorenson Lake, Westwick  b) Becher's P r a i r i e  (Box 4 ) , Round-up Lake  The w a t e r b o d i e s  (Chilcotin Area):  Lake Barnes  ( P h a l a r o p e ) , Lake L y e (Box 20-21),  Lake J a c k s o n (Near O p p o s i t e Box 4 ) , Lake Greer (Box 89), Rock Lake, Near P h a l a r o p e , Near O p p o s i t e C r e s c e n t , Box 17, B a r k l e y Lake  ( O p p o s i t e Box 4 ) , E a s t Lake  ( R a c e t r a c k ) and Box 27.  FIGURE 1  The Study A r e a : The t h r e e l a k e s i n the S p r i n g h o u s e region. I n s e t s : The F r a s e r P l a t e a u and i t s l o c a t i o n i n the p r o v i n c e of B r i t i s h Columbia.  5  FIGURE 2  The Study A r e a :  water bodies i n  the C h i l c o t i n r e g i o n  7 The l a k e s a r e c o n t a i n e d i n the C h i l c o t i n and C a r i b o o p a r k l a n d s b i o t i c a r e a s (Munro, 1945; Munro and Cowan, 1947) a t an e l e v a t i o n o f about 1000 meters.  The t e r r a i n i s a r o l l i n g  savanna-type u p l a n d c h a r a c t e r i z e d by Agropyron  (bunchgrass)  and s t a n d s o f Populus t r e m u l o i d e s , Pseudotsuga m e n z i e s i i and Pinus contorta. 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 average a n n u a l temperatures (the means f o r January and J u l y a t B i g o o Creek b e i n g -10.6 C and 13.3 C r e s p e c t i v e l y ) , l a r g e f l u c t u a t i o n s i n s e a s o n a l and d a i l y temperatures and low p r e c i p i t a t i o n (12.66 i n c h e s a t B i g Creek a n n u a l l y ) (Scudder and Mann, 1968; Topping, 1971). late April.  The l a k e s a r e i c e c o v e r e d from mid October t o  8 B.  THE PHYSICAL AND CHEMICAL PROPERTIES OF THE LAKES The w a t e r b o d i e s were chosen so a s t o o b t a i n as wide a  range o f s a l i n i t y a s p o s s i b l e w i t h r e s p e c t t o t h e o c c u r r e n c e of c h i r o n o m i d s .  I n p a r t i c u l a r , the lake s e r i e s contains the  e n t i r e gamut o f w a t e r c h e m i s t r y tentans  (Topping,  1971).  t o l e r a t e d by Chironomus  W h i l e s a l i n i t y v a r i e d , t h e use o f  t h i s p a r t i c u l a r l a k e s e r i e s kept o t h e r e n v i r o n m e n t a l  para-  meters such a s p h y s i c a l l o c a t i o n and c l i m a t e as s i m i l a r a s possible.  I n a d d i t i o n , the w a t e r s l a c k i n l e t and o u t l e t  streams, l a c k f i s h p r e d a t o r s and a r e s u b j e c t t o d i s t u r b a n c e by c a t t l e The  (Scudder, 1969 A ) . l a k e s v a r y b o t h i n s i z e and c h a r a c t e r ; the 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 NaHCO^ w h i l e i n the s m a l l e r , f r e s h e r ones MgCO^ p r e v a i l s .  T h i s must be con-  s i d e r e d o n l y a g e n e r a l t r e n d , however, (East Lake i s a r e l a t i v e l y l a r g e , f r e s h w a t e r body w i t h sodium as t h e dominant c a t i o n w h i l e Near P h a l a r o p e i s a much s m a l l e r though more s a l i n e l a k e , dominated by t h e sodium i o n ) and t h e c h e m i c a l l y p r e v a l e n t i o n s a r e no doubt r e l a t e d t o t h e c o m p o s i t i o n  of the  u n d e r l y i n g r o c k s r a t h e r than t o t h e s i z e o f the w a t e r body (Cummings, 1940;  Topping, 1969).  Some s h o r e l i n e s a r e r e l a t i v e l y steep and f i r m w h i l e o t h e r s a r e v e r y s h a l l o w and e x t r e m e l y  soft.  The l a t t e r  c h a r a c t e r seems t o be a s s o c i a t e d w i t h c e r t a i n p r o d u c t i v i t y o r chemical  l e v e l s supporting marginal  S c i r p u s a c u t u s growth  (Sorenson L a k e , Westwick L a k e , Near P h a l a r o p e ) and heavy  9 c o n c e n t r a t i o n s o f r o o t e d a q u a t i c s such as  Myriophyllum  (Rock L., B a r k l e y L . ) , N a j a s (Sorenson L. , Westwick L.) Potamogeton (Box 27)  (Munro, 1941)  (Plates  and  1-3).  From mid-June onwards a l g a l blooms a r e common i n most l a k e s , e s p e c i a l l y f i l a m e n t o u s greens such as S p i r o g y r a and Zygnema i n Sorenson Lake and b l u e g r e e n s  such as Aphanozomenon  i n Near O p p o s i t e C r e s c e n t , L. J a c k s o n , L. Greer and E a s t Lake (Plate 4).  I n the more s a l i n e l a k e s emergent v e g e t a t i o n i s  absent as a r e heavy a l g a l blooms ( P l a t e s 5, 6 ) .  These l a k e s  u s u a l l y have r e l a t i v e l y f i r m margins r i n g e d w i t h w h i t e  salt  deposits (Plate 6). The most s t r i k i n g change i n the fauna between the low and h i g h s a l i n i t y l a k e s i s the replacement  i n the h i g h e r  s a l i n i t i e s o f the v a r i e d amphipod and c l a d o c e r a n  crustacean  fauna by g r e a t numbers o f copepod c r u s t a c e a n s . The g e n e r a l 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 the w a t e r b o d i e s a r e shown i n T a b l e I .  TABLE 1  The P h y s i c a l and Chemical P r o p e r t i e s o f the L a k e s . and Scudder  M o d i f i e d from Topping  (1969 A).  (1969)  PI rr  CO  ga  W  o X  !>r  ro  z i ro  n  o H  ro p> 01 ri  r-* ^4  ro B1ro a tl  ro  o ro o 3 13  3 01 3  o  o  In  r*  t-  po 0 n 7?  t-  O 1  t-i p>  1  ro ro n  la]  •fl 3' 01  1  t-  w o H-  1  o 7T  rr Cl 3 O  on  G > w  r  01  ro  po o c 3  to  i  01  (u H 3  ro  a  c •a  Water Body  o  ho  Nl  ON  Ui Lo  •^J  ON  CO CO  o  o Lo  o  (-*  O  I-  h-*  Ln  NO  *-J  t-*  •O  LO  1  r-*  ON  ho  to  LO  Ul  Ul  M  Lo  LO  S  Z pi  09  09  09  09 n o  •o  o o  EC  n o o o LO LO  o o  EC  n n o o Lo LO  O  33 O  O O  LO LO  1  Ln CO  1  EC O  O O  •p-  Ln  00  LO  O  LO  Lo  r-*  4>  LO  ho  Ln  O  Ul  z  •z »  Z m  a n  cc n  EC  ON  p n o  H* Ln  Lo ro  09 O  LO  CTN  o  r-»  1  Lo Lo  Ln  EC o o  o  o  CO  CO o -J o  4>  LO  o  t  ON  Ul o  CO 4>  r  t-*  r-  ro  to  to  o  •P-  ~-j  CO  ON  ho  ro  4>  Ul  LO  LO  Ul  1  K Z 09 P  Z »  1  n  o  W o  o o  EC n  o  Z P> o o  EC n  o  Mean Depth (m)  ON  j  ho  V  Max.Depth (m) Main C a t i o n  Z P o o  A r e a (Ha)  EC o o  Main Anion  o o  Highest R e c o r d e d Conductivity umho/cm  ho  Mean Conductivity umho/cm 25 C 0  T.D.S. mg/1  Ln  O  Na meq/1  •P-  ui  r-  1  *-  -o.  K O  meq/1  o  •p-  ON  to  ~J  *o  Ca meq/1 Mg meq/1  •p-  O  •P-  CO CO  CO  co  3  meq/1  ON  HCOo meq/1 o O  OT  O NS t-  1  O NS  -P«  O  O  O  t~* 4>  LO Ln  LO •p-  O ro  LO  O vD  Ln -vj  r->  LO  NS  Ln  rLO  ON h-*  O -0  •P-  LO O  NS  1  CO  Co  ro NS  ON  l_* r-  NS  00 vO  00 LO  vO VO  LO 4>  00  •P*  Ln  Ln  Ln  LO  ON  °2 mg/1 Highest R e c o r d e d pH  O  O  O  H*  VO  o vO  LO  -P«  LO  ro  o  h-'  ro  •P*  Ln  -p-  Ln  LO  ro  ro  LO  Ln  Ln  vo  LO  VO  vO  ro  00  00  LO  LO  LO  r-»  *-J  -P-  •vi  <o  O  MD  O  ^4  r-*  NS  CTv  00  00  00  4>  LO  ON  •P*  •P*  Ln  •P-  vO  CO  vO  4> LO  N>  00 LO  O  Lo  O  00  H*  O  NS  O  ro  •^1  O  o  1  Ln  vO  VO  VO  O  vO  VO  VO  VO  VO  VO  r-  H»  Ln  Ln  CO  ro  ON  LO  --J  CO  00  00  00  00  03  vO  00  VO  VO  VO  ON  CO  VO  4>  VO  ON  o  vD  ro  CO  CO  4>  H*  r-*  Ln  ON  •vj  •P-  ro  O vO  ro o  VO  ro  Cn  ro ro  VO  t-*  ro ro  Ln  1  ro  NS  o  S0 meq/1 4  -P-  I-*  VO  Cl meq/1  •P-  ^4  Mean pH Per c e n t organic carbon  PLATE 1  Box 27, the f r e s h e s t o f the l a k e s . Note the e x t e n s i v e mat o f emergent Potamogeton  natans.  A c l o s e u p o f the v e g e t a t i o n i n Box 27.  11  PLATE 2  A.  B a r k l e y Lake, a good example o f the s h a l l o w , s o f t - e d g e d type w i t h abundant M y r i o p h y l l u m .  B.  B a r k l e y Lake.  M y r i o p h y l l u m sp.  12  PLATE 3  A.  Near P h a l a r o p e .  A l a k e i n the  m i d d l e range o f s a l i n i t y c h a r a c t e r i z e d by v e r y s o f t m a r g i n s and abundant S c i r p u s a c u t u s .  B.  Near O p p o s i t C r e s c e n t .  A shallow,  f i r m e r edged l a k e o f medium s a l i n i t y .  13  PLATE 4  Lake G r e e r , a l a k e w i t h r a t h e r s t e e p , f i r m m a r g i n s , growths o f M y r i o p h y l l u m sp. and summer Aphanozomenon blooms.  Lake J a c k s o n .  Steep, f i r m m a r g i n s ,  s m a l l stands o f S c i r p u s a c u t u s and v e r y heavy mats o f Aphanozomenon. l a k e o f medium-high s a l i n i t y .  This i s a  14  PLATE 5  A.  Lake L y e .  A r i s e i n water  has k i l l e d t h e Populus  level  tremuloides  stand.  B.  Round-up Lake.  A high s a l i n i t y  lake with a firm,  gravelly  No emergent v e g e t a t i o n . precipitated  bottom.  Note  s a l t s on t h e shore.  15  PLATE 6  Barnes Lake. lakes  The most s a l i n e of t h e  studied.  Barnes Lake. precipitated  The f i r m m a r g i n w i t h salts.  16  Ill  SPECIES DIVERSITY AND THE CHIRONOMID COMPLEX IN LAKE SERIES  A.  MATERIALS AND METHODS 1.  Temperature  Throughout  THE  Records  the summer temperature p r o f i l e s were taken i n  the l a k e s a t the mud-water i n t e r f a c e (1 meter) w i t h Ryan  D-30  s u b m e r s i b l e temperature r e c o r d e r s (Ryan I n s t r u m e n t s , I n c . , Seattle). 2.  B i o l o g i c a l Sampling Methods  a)  L a r v a l Sampling  A t w e e k l y i n t e r v a l s from May  23 t o August 29,  1970,  d u p l i c a t e l a r v a l samples were t a k e n from each l a k e ( e x c e p t s i x each i n Westwick Lake and Sorenson Lake) a t a depth of one meter.  Samples were t a k e n from the 1 meter depth zone  s i n c e t h i s i s the depth a t w h i c h C. t e n t a n s i s most abundant. A 15 by 15 cm Ekman dredge was used f o r the s a m p l i n g .  I f the  dredge was brought to the s u r f a c e i n c o m p l e t e l y c l o s e d the sample was d i s c a r d e d .  Samples were then washed and  through a 0.56 mm mesh s c r e e n and the mud were s t o r e d i n g l a s s j a r s f o r f u r t h e r  seived  and l a r v a e r e t a i n e d  sorting.  S i n c e J o n a s s o n (1955) s t a t e s t h a t i t i s the head c a p s u l e w i d t h o f l a r v a l c h i r o n o m i d s t h a t d e t e r m i n e s whether o r n o t they a r e r e t a i n e d by the mesh, and s i n c e S a d l e r (1935) r e p o r t e d the head c a p s u l e d i a m e t e r o f f o u r t h i n s t a r C. t e n t a n s ranged  18 f r o m 0.71 t o 0.74 mm and  (my measurements have a mean o f 0.76 mm)  t h a t o f t h e t h i r d i n s t a r was l e s s than 0.40 mm  (my mean  measure i s 0.43), o n l y f o u r t h i n s t a r l a r v a e c o u l d be c o l l e c t e d quantitatively.  I n t h i s study, a l l the species considered i n  d e t a i l as l a r v a e have head c a p s u l e w i d t h s e x c e e d i n g 0.56 mm i n the f o u r t h i n s t a r .  I f populations  of a species  occurring  i n the d i f f e r e n t l a k e s can be assumed t o be composed o f t h e same r e l a t i v e numbers o f d e v e l o p m e n t a l s t a g e s , a l s o be assumed t h a t the e s t i m a t e s  then i t may  of f o u r t h i n s t a r larvae  r e f l e c t t h e d i f f e r e n c e s i n the abundance o f t h a t s p e c i e s i n the l a k e s .  F o r t h e purpose o f e v a l u a t i n g g e n e r a t i o n  o n l y an e s t i m a t e  of f o u r t h i n s t a r f l u c t u a t i o n s along  time, with  emergence d a t a i s n e c e s s a r y . Q u a n t i t a t i v e a n a l y s i s o f bottom fauna i s h i n d e r e d labour involved i n separating substrate.  by the  the i n s e c t s from t h e sampled  The u s u a l method o f e x t r a c t i n g c h i r o n o m i d l a r v a e  from mud and dense p l a n t m a t e r i a l i s by the benzene o r sugar f l o t a t i o n t e c h n i q u e ( S a l t and H o l l i c k , 1944; Anderson, 1951; Mundie, 1957).  These methods were c o n s i d e r e d  f o r one p e r s o n c o n t i n u o u s l y  i n the f i e l d .  impracticable  Mundie (1957)  n o t e s t h a t "core sampling w o u l d be made much more p r a c t i c a b l e i f the l a r v a e c o u l d be q u i c k l y and e f f i c i e n t l y e x t r a c t e d from the mud and counted.  P o s s i b l y only treatment of f r e s h cores  o f f e r s prospect of t h i s " .  Under t h e c i r c u m s t a n c e s ,  of f r e s h c o r e s p r e s e n t e d no problems;  analysis  p i c k i n g the e a s i l y seen  r e d and green w r i g g l i n g l a r v a e from the c o l l e c t e d samples was no more time consuming and j u s t as e f f i c i e n t as more s o p h i s t i c a t e d  19 t r e a t m e n t s o f p r e s e r v e d l a r v a e (Pask and C o s t a , 1971).  The  s o r t e d l a r v a e i n each sample were p r e s e r v e d i n 70 p e r c e n t ethanol. Mundie (1957) s t a t e s t h a t t h e t o p 5 cm o f mud usuallycon t a i n 95 p e r c e n t o f a l l l a r v a e .  I n s p e c t i o n o f t h e dredge  samples showed t h a t t h i s s e c t i o n was almost always  b)  Adult  taken.  Sampling  P u p a l and a d u l t midges were q u a n t i t a t i v e l y sampled by emergence t r a p s .  S i n c e many o f t h e specimens t r a p p e d by t h i s  method became wet o r damaged, i t was n e c e s s a r y t o p r e s e r v e them i n 70 p e r c e n t e t h a n o l .  The s o r t i n g o f l a r g e numbers o f a d u l t s  and pupae under a d i s s e c t i n g m i c r o s c o p e and t h e p r e p a r a t i o n o f microscope  s l i d e s f o r complete  demand such p r e s e r v e d m a t e r i a l .  i d e n t i f i c a t i o n o f the specimens F o r these reasons i t was  c o n s i d e r e d most u s e f u l and c o n v e n i e n t t o p r e s e r v e t r a p p e d material i n alcohol.  T h i s l i n e o f r e a s o n i n g i s f o l l o w e d by  Roback (1971) f o r even n e t t e d a d u l t s , b u t many w o r k e r s c o n s i d e r i t i m p o r t a n t t o make i n i t i a l i d e n t i f i c a t i o n s u s i n g p i n n e d specimens (Edwards, 1929) so t h a t w i n g v e n a t i o n and some s e t a l c o n f i g u r a t i o n s can be more c l e a r l y c h a r a c t e r i z e d . and S a e t h e r  S c h l e e (1966)  (1969) r a i s e i m p o r t a n t arguments i n f a v o u r o f p r e -  p a r i n g s l i d e mounted a d u l t  specimens.  The emergence t r a p samples were used t o i d e n t i f y t h e c h i r o n o m i d s i n h a b i t i n g t h e one meter depth zone o f each  lake,  t o c a l c u l a t e t h e numbers and sequences o f i n s e c t s emerging  20 per u n i t a r e a throughout the sampling p e r i o d and the l i f e c y c l e s of the more i m p o r t a n t Two  to determine  species.  t r a p s were s e t out i n the one meter depth zone of  each l a k e w i t h the e x c e p t i o n of Sorenson and Westwick Lakes where e i g h t t r a p s were used.  The  t r a p s were suspended under  the w a t e r from a wooden c r o s s d r i v e n i n t o the mud. emptied every f o u r t h day;  c a r e was  They were  t a k e n not to d i s t u r b the  s u b s t r a t e d u r i n g the emptying procedure. The  t r a p used was  H a m i l t o n (1965).  a m o d i f i c a t i o n of t h a t d e s i g n e d by  E s s e n t i a l l y i t i s a cone of c l e a r a c e t a t e  p l a s t i c w i t h an e i g h t ounce g l a s s j a r screwed i n t o the apex. A s c e n d i n g pupae e n t e r the f u n n e l and emerge as a d u l t s i n the a i r space w i t h i n the j a r . i s 0.1  The  a r e a of the mouth o f the  trap  square meter ( F i g u r e 3; P l a t e 7) (Cannings, 1972).  The  d e s i g n i s s i m i l a r to those used by B r u n d i n (1949) and Jonasson (1954) except t h a t m e t a l s c r e e n i n g has been r e p l a c e d by c l e a r p l a s t i c ; t h i s m a t e r i a l makes the t r a p more and much e a s i e r t o c l e a n .  transparent  F o r use a t one meter these t r a p s  seem i d e a l - they a r e much s i m p l e r and cheaper than the deep w a t e r models of Mundie (1956), more d u r a b l e  than the  cones u s e d by S u b l e t t e and Dendy (1959) and  l e s s a f f e c t e d by  w i n d and wave than Corbetfe Mundie (1956, 1957) i n the t r a p p i n g method.  simpler  (1965) f l o a t i n g t r a p s .  o u t l i n e s the s o u r c e s of e r r o r He  s t a t e s t h a t t r a p s may  be  inherent  considered  to sample q u a n t i t a t i v e l y i f the i n s e c t s do not a v o i d them, and  PLATE 7  The emergence t r a p .  The base o f o  the f u n n e l has an a r e a o f 0.1 m .  21  FIGURE 3 D e t a i l s o f t h e emergence t r a p . From Cannings (1972).  SETTING OF TRAP 2x2 stake ^crossbar supporting 2 traps water level  lead weight mouth of trap 12" above bottom  29.5  cm  DETAIL OF COLLECTING JAR supporting cords  C O N E / TEMPLATE  -air space 8oz. jar small plastic cone  -water level EXPLODED VIEW OF TRAP  bakelite lid  hose clamp  — \  extra strips of plastic may be wrapped around cone to prevent cracking  ends of cords \\~under clamp  23 the c a t c h may be assumed t o have come from t h e bottom d i r e c t l y below t h e t r a p i f w a t e r c u r r e n t s do n o t cause h o r i z o n t a l movements i n p u p a l a s c e n t s .  E f f o r t s were made t o make  these assumptions v a l i d . Traps were s e t about a f o o t above t h e mud i n o r d e r t o reduce t h e e f f e c t s o f w a t e r movements and were c l e a n e d o f b a c t e r i a l and a l g a l c o a t i n g s a t each emptying i n o r d e r t o m a i n t a i n maximum t r a n s p a r e n c y .  No doubt many o f t h e p r e d a -  ceous organisms caught i n t h e t r a p s a l o n g w i t h t h e midges a f f e c t the a c c u r a c y o f t h e sample.  Species of hydrachnids,  zygopterans,  n o t o n e c t i d s , c o r i x i d s and d y t i s c i d s were f r e q u e n t l y trapped i n the  jars.  3.  R e a r i n g o f Specimens  By r e a r i n g a d u l t f l i e s from l a r v a e a l l t h r e e stages o f the l i f e c y c l e can be i d e n t i f i e d .  Complete i d e n t i f i c a t i o n i s  invaluable since i t i s frequently impossible  t o determine l a r v a e  p a s t t h e g e n e r i c l e v e l whereas male a d u l t s can u s u a l l y be i d e n t i f i e d to species. Fourth  i n s t a r l a r v a e were p l a c e d i n i n d i v i d u a l  screen-  covered v i a l s or p e t r i e dishes c o n t a i n i n g d e c h l o r i n a t e d water, shredded S c o t t t i s s u e paper f o r tube c o n s t r u c t i o n , and s m a l l amounts o f f o o d i n t h e form o f n e t t l e l e a f powder and powdered milk.  The c o n t a i n e r s were k e p t a t room temperature i n a l i g h t  regime o f 16 hours l i g h t , 8 hours dark.  Rearing  p r o v e d g r e a t l y i f t h e w a t e r was c o n t i n u o u s l y  success im-  aerated.  24 4.  P r e p a r a t i o n and  I d e n t i f i c a t i o n of Specimens  The  l a r v a e were s o r t e d under a d i s s e c t i n g m i c r o s c o p e  were d i v i d e d i n t o groups of a p p a r e n t s p e c i f i c and ranks.  The  volume d i s p l a c e m e n t of each wet  as a rough measure of c h i r o n o m i d  biomass.  and  instar  sample was  taken  A d u l t samples were  t r e a t e d i n the same manner; males, females and pupae b e i n g considered  separately.  Permanent mounts o f r e p r e s e n t a t i v e  specimens were then made on m i c r o s c o p e s l i d e s i n o r d e r  that  p o s i t i v e i d e n t i f i c a t i o n o f the s o r t e d t y p e s c o u l d be made. The method f o l l o w e d t h a t of S c h l e e  (1966) and S a e t h e r  I d e n t i f i c a t i o n f o l l o w e d Edwards (1929), Townes (1945), (1960, 1963,  1964,  determinations Oliver  and  1967,  1970)  S u b l e t t e ( E a s t e r n New  The nomenclature f o l l o w s S u b l e t t e and  Sublette  Further  c r o s s c h e c k i n g were performed by Dr.  (Ottawa) and Dr. J.E.  University).  and Roback (1971).  (1969).  D.R.  Mexico Sublette  (1965) and a d d i t i o n s and r e v i s i o n s i n subsequent S u b l e t t e papers and Roback  (1971).  A f t e r the i d e n t i f i c a t i o n s were completed the c o l l e c t i o n s were s o r t e d and counted a second time.  E r r o r s due  i d e n t i f i c a t i o n of specimens and m i s c o u n t i n g  5.  A n a l y s i s o f the Data  a)  The  were thus m i n i m i z e d .  U.B.C. TRIP ( T r i a n g u l a r R e g r e s s i o n  ( B j e r r i n g and Seagreaves, 1972)  was  Package) program  u s e d to compute c o r r e l a t i o n  c o e f f i c i e n t s between s e l e c t e d v a r i a b l e s . c o r r e l a t i o n a n a l y s i s ( S i e g e l , 1956)  to i n c o r r e c t  was  The  Kendall rank  employed i n the  few  25 c o r r e l a t i o n s u s i n g o r d i n a l measurement.  These were c o r -  r e l a t i o n s u s i n g emergence d i s p e r s i o n as a v a r i a b l e . b)  F o r each l a k e a monthly and t o t a l average  d i v e r s i t y i n d e x was c a l c u l a t e d .  The f u n c t i o n u s e d i s t h e  e n t r o p y f o r m u l a as a p p l i e d t o i n f o r m a t i o n a n a l y s i s 1957; M a r g a l e f , 1968).  species  (Khinchin,  The use o f t h i s f u n c t i o n f o r e s t i m a t i n g  s p e c i e s d i v e r s i t y i n ecosystems has been w i d e s p r e a d (MacArthur and M a c A r t h u r , 1961; L a r k i n e t a l , 1970; Johnson and B r i n k h u r s t , 1971).  6.  S t o r a g e o f t h e Data f o r F u r t h e r  Study  The b a s i c d a t a c o l l e c t e d i n t h i s s t u d y , i n c l u d i n g computer programs and s p e c i m e n . c o l l e c t i o n s , have been f i l e d f o r f u t u r e use i n t h e Spencer Entomology Museum, Department o f Z o o l o g y , U.B.C.  26 B.  RESULTS 1.  Water Temperatures  i n the Lake  Series  The temperature a t the mud-water i n t e r f a c e  (1 m e t e r )  i n the l a k e s i s shown i n T a b l e I I and temperature  profiles  f o r f i v e o f the s i x C. t e n t a n s l a k e s under c o n s i d e r a t i o n a r e found i n F i g u r e 4.  Sorenson Lake r e c o r d s a r e i n c o m p l e t e . A l l  the temperature t r e n d s a r e s i m i l a r i n the l a k e s , the major d i f f e r e n c e among them b e i n g the v a r i a t i o n i n the d a i l y ature ranges.  The d i f f e r e n c e i n d a i l y temperature  temper-  fluctuation  between two l a k e s such as E a s t Lake and Lake J a c k s o n and  two  o t h e r l a k e s such as Westwick Lake and B a r k l e y Lake might  be  a t t r i b u t e d t o heavy Aphanozomenon (Cyanophyceae)  blooms over  the 1 meter depth zone i n the former w a t e r b o d i e s throughout a l l but the e a r l y p a r t of the s t u d y p e r i o d . may  Such a l g a l mats  p r e v e n t r a p i d d i u r n a l temperature f l u c t u a t i o n s i n the w a t e r . T a b l e I I shows t h a t the mean temperature over a l l the l a k e s  d u r i n g the p e r i o d was  17.8°C.  The mean temperature of a l l  t h r e e of the l a k e s was w i t h i n 1°C of t h i s v a l u e . temperature reached was  31°C  The h i g h e s t  i n L. J a c k s o n on J u l y 13.  range o f w a t e r temperature on t h i s date was  but  15°C!  The  (Figure 4).  C u m u l a t i v e day degrees f o r the s i x l a k e s a r e graphed i n F i g u r e 5.  I n the case of Sorenson L. the c u r v e up to May  18 i s  t h a t of Westwick L., chosen s i n c e the r e s t of the s l o p e i s i d e n t i c a l i n the two l a k e s . atures.  These p l o t s r e p r e s e n t mean temper-  From these graphs the number of day degrees t h a t have  accumulated between any two dates may  be r e a d .  S i n c e the  TABLE I I Average w a t e r temperatures i n the lake series.  Temperatures a t the  mud-water i n t e r f a c e (1970).  WATER BODY  MAY mean  JUNE mean  JULY mean  AUGUST mean  SUMMER mean  Barnes L.  12. 6  19. 2  21. 0  18. 3  19. 8  Round-up L.  12. 0  18. 9  20. 0  19. 5  17. 6  L. L y e  13.,1  19. 4  20. 1  19. 2  18. 0  B o i t a n o L.  13. 3  18. 6  19.,8  19. 2  17. 7  L. J a c k s o n  12.,8  1.9. 4  20.,1  19. 0  17.,8  L. Greer  12.,8  18. 6  19. 7  18. 9  17.,5  Rock L.  13.,0  18. 3  18.,5  18. 3  17.,0  Near P h a l a r o p e  10..5  16.,4  18.,2  17. 2  15.,6  Westwick L.  13..5  20.,1  21.,1  19. 3  18. 5  Sorenson L.  14.,9  18.,5  18..1  17. 8  17.,3  Near Op. C r e s c e n t  12.,7  19.,7  20..5  19. 6  18.,1  Box 17  13..2  19.,1  20..1  19. 1  17..9  B a r k l e y L.  14.,9  19.,4  21.,2  18. 3  18.,4  E a s t L.  12.,0  17..9  18.,9  18. 3  16.,8  Box 27  15..3  20.,2  20..4  19. 8  18..9  FIGURE 4  D a i l y temperature range i n some o f the l a k e s where Chironomus is  abundant.  tentans  L. Jackson  Rock L  FIGURE 5  C u m u l a t i v e day degrees measured a t the mud  s u r f a c e a t a depth o f 1 meter  i n some o f the l a k e s where Chironomus t e n t a n s i s abundant.  29  30 g e n e r a t i o n time of a s p e c i e s i s c o n s i d e r e d t o be a f u n c t i o n of the b e n t h i c temperatures (Mundie, 1957), s p e c i e s can be c h a r a c t e r i z e d by the number of day degrees needed to complete their  development.  2.  Chemical Data  P h y s i c a l and c h e m i c a l d a t a o t h e r than temperature a r e from Topping (1969) and Scudder  (1969 A) (Table I ) . These  d a t a r e p r e s e n t i n f o r m a t i o n g a t h e r e d from s u r f a c e w a t e r s o r a t a depth of 1 meter averaged o v e r the summer sampling p e r i o d . As s e a s o n a l v a r i a t i o n i n the p h y s i c o - c h e m i c a l p r o p e r t i e s i s l e s s pronounced than a r e the d i f f e r e n c e s between l a k e s (Topping, 1969) and as the c o n c e n t r a t i o n d a t a agree f a v o r a b l y w i t h the t e n y e a r averages (Scudder, 1969 B; Scudder, p e r s . comm.), i t was f e l t t h a t the use o f t h e s e d a t a i n subsequent phases o f the work would n o t a d v e r s e l y a f f e c t the r e s u l t s of the i n v e s t i gation.  F o r d e t a i l s on the c o l l e c t i o n and a n a l y s i s of t h e s e  d a t a , and f o r a more comprehensive d i s c u s s i o n of the 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 of the l a k e s , see Topping (1969).  3.  The Occurrence o f S p e c i e s i n the Lakes  T a b l e I I I shows the d i s t r i b u t i o n of s p e c i e s c o l l e c t e d a t a depth of 1 meter i n the l a k e s .  T h i s s h o u l d be c o n s i d e r e d  o n l y a p r e l i m i n a r y l i s t of the c h i r o n o m i d fauna o f t h i s depth zone.  A d u l t s r e p r e s e n t i n g 34 s p e c i e s , 15 genera and 3 sub-  f a m i l i e s were t r a p p e d and a r e l i s t e d i n F i g u r e 27 a l o n g w i t h  TABLE I I I  The d i s t r i b u t i o n o f c h i r o n o m i d s i n the one meter depth zone i n the lakes.  Both a d u l t s and i d e n t i f i e d  larvae are included.  Derotanypus n.sp.  alaskensis  Tanypus punctipennis  Derotanypus Procladius bellus Procladius nietus Procladius freemani Procladius ruris Procladius dentus Procladius clavus  n.sp.  Procladius sublettei Procladius Ablabesmyia peleensis  •  Nanocladius n.sp.  •  • e  Cricotopus albanus  a  Cricotopus .flavibasis  •  Cricotopus trifasciatus  •  Psectrocladius barbimanus  a  Acricotopus nitidellus  •  Psectrocladius zetterstedti Psectrocladius n.sp;  •  •  Chironomus anthracinus Chironomus. atrella Chironomus tentans Chironomus plumosus  •  Box 27  •  • •.  a  • a  e  •  •  •  •  • •  a  E a s t L.  •  •  Chironomus n.sp. (near atritibia)  a  •  a  n.sp.  • 6  •  •  • • •  o  Chironomus  B a r k l e y L.  • •  •  Einfeldia pagana  e  • e  e  Cryptochironomus psittacinus  •  • • a  Cryptotendipes ariel  Box 17  •  a  •  1  a  • •  •  Endochironoraus nigricans  • •  e  Polypedilum n.sp. Calopsectra gracilenta  • • •  • e  •  -•  Glyptotendipes barbipes  Calopscctra holochlorus  • s  Nr.Op.Crescent e  S o r e n s o n L. a  • •  •  W e s t w i c k L.  • •  • •  Nr.Phalarope  • • 0  • •  o  Rock L.  •  a e  • •  •  •  •  e  a  •  L. G r e e r  «  •  • e  • o  • • • • • • •  • • «  •  • •  L. J a c k s o n  •  •  •  •  • • • •  •  • o  • • o  o  Round-up L.  • •  e  e  • • • •  a  e  e  • •  e  • •  B a r n e s L. a  • • • •  •  B o i t a n o L.  • e  • o  • • •  L. L y e  • • • o a e o e  o a  9 o  TABLE IV  The  d i s t r i b u t i o n of l a r v a e  to s p e c i e s .  unidentified  Clinotanypus sp. Tanypus sp. Psectrotanypus sp.A Psectrotanypus sp.B Psectrotanypus sp.C Procladius sp.A Procladius sp.B Ablasbesmyia 1 Cricotopus ? Chaetolabis sp.A Chaetolabis sp.B Chironomus sp.A. Chironomus sp.C  Chironomus sp.B Chironomus sp.D Chironomus sp.E Cryptochironomus sp.  Box 27  0 o  Cryptotendipes ?  Box 17 e e  Cryptocladopelma sp.  East L.  0 0 «  0  Endochironomus sp.  Barkley L.  0 0 o o  Nr. Op.Crescent o  0 0 o  0 0 e  Glyptotendipes sp.A  e  0 0 0 0 0 0 • 0  Glyptotendipes sp.B Polypedilum sp.  1  Tanytarsus sp.A  8  o  • • o  e  • • o  Sorenson L. o  e  0  9  0  o  a o  Nr. Phalarope  0 0'0 0 0  •  0  Westwick L. e  Rock L. o  0 0 e  0 o 0 0 0 0 0 0 e  Parachironomus sp .  Tanytarsus sp.B Calopsectra gracilenta ?  •  0 0 0 0 0 e  e  o  O  0  e  0  0 0  o  • 0  L. Greer  0  o  0  0  0  a  o  o  ©  e  ©  e  L. Jackson  e  e  o  0  o a ©  o e  e  " r ! 1  L. Lye  ©  !  0  0 «  o  o  e  o o  «  Boitano L. e  o  Round-up L. a  0 0  0 o  0 e  e i  ©  e  Barnes L. »  0  b e  e  0 0  0  33 t h e i r range o f s a l i n i t y t o l e r a n c e .  Twelve a d u l t s were  a s s o c i a t e d w i t h t h e i r l a r v a l forms.  Other t e n t a t i v e s p e c i e s  of l a r v a e i d e n t i f i e d to genus a r e l i s t e d i n T a b l e IV.  4.  Species  In order  Considered i n D e t a i l  to d e f i n e major d i f f e r e n c e s i n the  chironomid  communities of the l a k e s i n t h i s s a l i n e s e r i e s , a number of the more d i s t i n c t i v e s p e c i e s a r e c o n s i d e r e d  i n some d e t a i l .  These a r e P r o c l a d i u s b e l l u s , P r o c l a d i u s f r e e m a n i ,  Procladius  dentus, P r o c l a d i u s c l a v u s , A b l a b e s m y i a p e l e e n s i s ,  Cricotopus  f l a v i b a s i s , Cricotopus Cryptotendipes  ariel,  albanus,  P s e c t r o c l a d i u s barbimanus,  C a l o p s e c t r a g r a c i l e n t a , Derotanypus  a l a s k e n s i s , E i n f e l d i a pagana, G l y p t o t e n d i p e s Chironomus a n t h r a c i n u s , The reference  Chironomus n. sp. and  barbipes, Chironomus  f i r s t t e n s p e c i e s w i l l be d i s c u s s e d p r i m a r i l y w i t h to c h e m i c a l  e n v i r o n m e n t a l f a c t o r s and w i l l form a  b a s i s f o r d i s c u s s i o n of the l a k e s e r i e s as a g r a d i e n t environmental conditions.  be s t r e s s e d .  of  The n e x t f i v e s p e c i e s w i l l be  s i d e r e d i n a s i m i l a r manner a l t h o u g h  biotic factors w i l l  conalso  These a r e the s p e c i e s w h i c h p o t e n t i a l l y have the  g r e a t e s t i n t e r a c t i o n w i t h C. described with reference  tentans.  C. t e n t a n s  to the l a k e s e r i e s and  w i t h o t h e r s p e c i e s t h a t may a)  tentans.  i s then  the i n t e r a c t i o n s  i n f l u e n c e i t s mode of  life.  Procladius bellus  T h i s i s a w i d e s p r e a d but not abundant s p e c i e s .  The  species  34 i s known o n l y from t r a p p e d a d u l t s , s i n c e the l a r v a e of the l a r g e P r o c l a d i u s genus were found to be l a r g e l y  inseparable.  The s p e c i e s emerges i n r e l a t i v e l y s m a l l numbers ( u s u a l l y l e s s than 10 per square meter) i n a l l l a k e s i t o c c u r s i n except i n E a s t L. and Box 27 where c o n c e r t e d emergence o v e r a two week p e r i o d amounted to 40 and 180 per square meter (Figure 6). May  respectively  I n a l l cases the emergence p e r i o d i s from l a t e  t o mid June.  P. b e l l u s appears to have o n l y one genera-  t i o n , a l t h o u g h i n Box 27 two peaks 24 days a p a r t may a second g e n e r a t i o n l a t e i n June.  indicate  B u c k l e y and S u b l e t t e  (1963)  and S u b l e t t e (1963) n o t e t h a t P. b e l l u s i s v e r y w i d e l y spread i n N o r t h A m e r i c a and tends t o be a p r o f u n d a l d w e l l e r . (1957) found i t r e a s o n a b l y abundant Lake Texoma. A p r i l o r May  Sublette  from 3 t o 15 meters i n  Most a u t h o r s s t a t e t h a t P. b e l l u s emerges from t o September or October w i t h one g e n e r a t i o n  c o n c e n t r a t e d i n a s p r i n g emergence ( S u b l e t t e , 1957).  Judd,  i n t h r e e s e p a r a t e s t u d i e s (Judd, 1953; 1957; 1961) agrees w i t h t h i s a l t h o u g h i n one of h i s emergence s t u d i e s , P. b e l l u s showed two g e n e r a t i o n s , one peak coming on May  30, the second on  August 13 (Judd, 1961). P. b e l l u s i s much more abundant  i n the f r e s h e r w a t e r s of  the s e r i e s ( F i g u r e 6 ) , b e i n g l e s s f r e q u e n t l y found i n w a t e r s above a c o n d u c t i v i t y o f 800 jumho/cm (Near O p p o s i t e C r e s c e n t ) . S m a l l emergences o c c u r i n Westwick, Rock, J a c k s o n and Round-up Lakes.  The abundance of P. b e l l u s 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 a l l i n d i c a t o r s o f c o n c e n t r a t i o n , showing a d e c i d e d p r e f e r e n c e f o r low pH v a l u e s (a c o r r e l a t i o n c o e f f i c i e n t of -.937) (Table V ) .  FIGURE 6  The emergence o f a d u l t s of P r o c l a d i u s b e l l u s (Loew) and P r o c l a d i u s  freemani  S u b l e t t e from the one meter depth zone of s e v e r a l l a k e s . logarithmic scale.  The o r d i n a t e  is a  C o l l e c t i n g began on  May 19, took p l a c e every f o u r t h day and t e r m i n a t e d on August 29, 1970.  PROCLADIUS BELLUS EAST L.  M  " J '  BOX 27  J ' A '  ' M"  1  J "'  J ' A  J  PROCLADIUS FREEMANI ROUND-UP L.  M  • J '  J  L. LYE  ' A '  ' M '  ROCK L.  J '  J  BOITANO L.  A '  ' M '  BARKLEY L.  A  M  J  EAST L.  10 J  M  J '  A  M  '  36 The o n l y p r e v i o u s r e c o r d of t h i s s p e c i e s i n B r i t i s h Columbia i s from Cranbrook (Roback, 1971).  Further discus-  s i o n o f g e n e r a l d i s t r i b u t i o n and e c o l o g y of the s p e c i e s be found i n Wurtz and Roback (1955), M o r r i s s e y Davis  may  (1950) and  (1960).  b)  Procladius  freemani  T h i s m o r p h o l o g i c a l l y v a r i a b l e s p e c i e s can most e n v i r o n m e n t a l  tolerate  c o n d i t i o n s found i n the l a k e s (Table  V)  a l t h o u g h i t i s most abundant i n the upper s a l i n i t i e s where i t s emergence d i s p l a y s s t r i k i n g d i f f e r e n c e s among the l a k e s (Figure 6).  I n Barnes L. t h e r e i s a s m a l l emergence of  4 per square meter i n l a t e May;  i n Round-up L. a l a r g e r  emergence a t t h i s time i s f o l l o w e d by another This l a t t e r p a t t e r n i s repeated  i n L. L y e . w i t h  i n e a r l y August. the a d d i t i o n of  a s u b s t a n t i a l l a t e J u n e - e a r l y J u l y emergence o f 30 per meter over 20 days. as i n Barnes L.  The  one emergence peak i n B o i t a n o L. i s  ( l a t e May)  75 per square meter.  square  but i s much l a r g e r , c o n s i s t i n g of  I n Rock Lake, a l a r g e , s i n g l e peak of  emergence o c c u r s i n l a t e J u n e - e a r l y J u l y .  E a s t Lake, the o n l y  r e l a t i v e l y f r e s h waterbody s u p p o r t i n g l a r g e numbers o f emergi n g P. f r e e m a n i has a peak i n l a t e May  and one  i n late July.  Box 17 and Greer L. show s m a l l , s i n g l e peaks i n the period;  Near O p p o s i t e  June-July  C r e s c e n t and B a r k l e y L. i n e a r l y August.  Thus i t i s seen t h a t P. Freemani emerges a t t h r e e times the sampling  p e r i o d : l a t e May,  during  l a t e J u n e - e a r l y J u l y and e a r l y  FIGURE 7  The emergence o f a d u l t s o f P r o c l a d i u s dentus Roback from the one meter depth zone o f s e v e r a l l a k e s . a logarithmic scale.  The o r d i n a t e i s C o l l e c t i n g began  on May 19, t o o k p l a c e every f o u r t h day, and  t e r m i n a t e d on August 29, 1970.  37  BARNES  L.  ROUND-UP L.  L. LYE  100  cc  Ul  p-  ui 5 in ec < o to  10  J  cc  Ul a.  1  M  J  1  J  1  A  I  M  1  1  J  J  1  I  I  1  "~1  A  M  J  J  I  A  Z  (3  CC  Ul  £  BOITANO L.  Ul  WESTWICK L.  EAST L.  100 q  3  a  < u. O cc Ul CO  10  Z  M  M  r  J  J  A  M  A  38 August.  Every c o m b i n a t i o n of t h e s e emergence t i m e s i s  r e c o r d e d e x c e p t f o r the sequence of J u n e - J u l y , e a r l y August. Why  t h e r e i s such d i s p a r i t y between the l i f e c y c l e s i n each  l a k e i s n o t e a s i l y u n d e r s t o o d ; no doubt i t i s b e s t e x p l a i n e d as the r e s u l t of v a r i a t i o n i n the i n s e c t s o r the l a k e s . The s p e c i e s has seldom been c o l l e c t e d a t the e x t r e m i t i e s o f i t s range.  The o n l y a v a i l a b l e r e c o r d from B r i t i s h Columbia  i s a s e r i e s o f t h r e e males from T e r r a c e (Roback, 1971).  c)  P r o c l a d i u s dentus  T h i s d i s t i n c t i v e s p e c i e s has n o t been p r e v i o u s l y r e p o r t e d i n B r i t i s h Columbia (Roback, 1971).  In a l l  the l a k e s i n w h i c h  i t o c c u r s i n t h i s s t u d y , P. dentus has a s i n g l e g e n e r a t i o n emerging i n l a t e May  (Figure 7).  I t has a p r e f e r e n c e f o r the  more s a l i n e l a k e s ( c o n d u c t i v i t y above 4000 jumho/cm) such as B o i t a n o L., L. L y e , Round-up L. and Barnes L.  The  o f P. dentus i s h i g h l y c o r r e l a t e d w i t h c o n d u c t i v i t y  abundance (p<,.01),  t o t a l d i s s o l v e d s o l i d s ( p < . 0 5 ) , sodium ( p < . 0 5 ) , HCO3 ( p < . 0 5 ) and S 0  4  d)  (p < .01) (Table V ) .  Procladius clavus  T h i s i s a r e c e n t l y d e s c r i b e d s p e c i e s (Roback, 1971) and i s r e c o r d e d p r e v i o u s l y o n l y from the Northwest T e r r i t o r i e s . There i s no doubt t h a t P. c l a v u s i s the most abundant o f the genus i n the l a k e s .  species  Although i t i s r e s t r i c t e d to  39  B o i t a n o L., L. Lye, Round-up L. and i s v e r y abundant. are probably  Barnes L.,  P.  clavus  I n Barnes L. most of the P r o c l a d i u s l a r v a e  of t h i s s p e c i e s , making i t the dominant  chironomid  predator of that lake. P. c l a v u s has a l i f e c y c l e c h a r a c t e r i z e d by an extended emergence p e r i o d o c c u p y i n g the e n t i r e month of June and f i r s t week i n J u l y . about 345  The  the  emergence i n t h i s p e r i o d amounts t o  per square meter ( F i g u r e 8).  Round-up L. i s a l i t t l e l e s s c o n c e r t e d  The and  emergence i n i n L. Lye a second  peak appears l a s t i n g from l a t e J u l y to the end o f August. emergence i n B o i t a n o L. o c c u r s much s m a l l e r i n s i z e .  The  i n the J u n e - J u l y  The  b a s i c p a t t e r n i n the  l a k e s suggests t h a t a l a r g e emergence of a d u l t s from o v e r w i n t e r i n g l a r v a e produce a new but w h i c h may  on the c o n d i t i o n s i n the l a k e s . emergence may  other  developing  generation  of l a r v a e  emerge e a r l y (L. Lye)  depending  A l t e r n a t i v e l y , t h i s second  be a r e s u l t of p a r t of the o v e r w i n t e r i n g  population extending alternating  p e r i o d , but i s  s i g n i f i c a n c e of the second emergence  peak i n L. Lye i s not known.  that overwinter,  The  larval  d i a p a u s e , o r even the o c c u r r e n c e of  generations.  A t any r a t e i t i s e v i d e n t t h a t P. c l a v u s i s an member of the more s a l i n e environment, and adapted to the sodium c a r b o n a t e - b i c a r b o n a t e  important  seems e n t i r e l y lake  type.  T a b l e V shows the h i g h l y s i g n i f i c a n t c o r r e l a t i o n (p < .01) abundance w i t h c o n d u c t i v i t y , T.D.S., sodium, CO^  and HCO3.  of  FIGURE 8  The emergence o f a d u l t s o f  Procladius  c l a v u s Roback and A b l a b e s m y i a  peleensis  (Whalley) from the one meter depth zone of s e v e r a l l a k e s . logarithmic scale. May  The o r d i n a t e  is a  C o l l e c t i n g began on  19, took p l a c e on every f o u r t h day  t e r m i n a t e d on August 29,  1970.  and  40  PROCLADIUS CLAVUS L LYE  ROUND-UP L.  BARNES L.  100 q  10:  CC UJ H LU  s  M  M  M  LU CC  J  J  A  < =>  (0  100 g  BOITANO L.  CC LU  a  a z  o  I  10 d  LU  w  b a <  LL.  M  o  cc  J  J  A  ABLABESMYIA  LU  OQ | 100 q z  PELEENSIS BOX 27  EAST L.  BARKLEY L.  10 J  -i  M  J  J  A  i  M  1  • — i  J  J  1  A  1  i  r  M  -I-*  1  J  J  A  1  41 e)  Ablabesmyia p e l e e n s i s  T h i s i s an uncommon, b u t d i s t i n c t i v e i n h a b i t a n t o f the fresher lakes.  I t appears t o have two g e n e r a t i o n s  i n the  v e r y f r e s h w a t e r s o f Box 27 ( c o n d u c t i v i t y 40 jumho/cm), one i n l a t e M a y - e a r l y June (30 p e r square m e t e r ) and one i n July-August  (Figure 8).  I n the most s a l i n e w a t e r s o f i t s  range ( B a r k l e y L., 600-700 umho/cm), A b l a b e s m y i a p e l e e n s i s has o n l y one emergence peak i n J u l y , w h i l e i n E a s t L. t h e peak i s i n t h e l a t e May-June p e r i o d .  The abundance o f A. p e l e e n s i s  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 a l l environmental  f a c t o r s except  d i s s s o l v e d oxygen and e s p e c i a l l y shows a d e f i n i t e r e c i p r o c a l r e l a t i o n s h i p w i t h pH (r= -.938;  p < .01) (Table V ) .  (1969) d e s c r i b e s the f o o d o f t h e l a r v a e . p r e v i o u s l y been r e c o r d e d  f)  Cricotopus  Roback  T h i s s p e c i e s has n o t  from B r i t i s h Columbia (Roback, 1971).  flavibasis  T h i s common s p e c i e s o f t h e O r t h o c l a d i i n a e r e a c h e s i t s g r e a t e s t abundance i n E a s t L., b u t i s found i n most l a k e s up to a c o n d u c t i v i t y o f about 7000 umho/cm (Round-up L . ) .  It is  the s p e c i e s d e t e r m i n e d i n Cannings (1970) a s P s e c t r o c l a d i u s f l a v u s , and i s a d e n i z e n o f a q u a t i c p l a n t s . s p e c i e s i n b e n t h i c samples i n t h e p r e s e n t  The p a u c i t y o f t h i s  study f u r t h e r c o n f i r m s  t h a t t h i s s p e c i e s o c c u r s on a q u a t i c v e g e t a t i o n .  The f a c t t h a t  the O r t h o c l a d i i n a e ( w i t h o u t haemoglobin) a r e c o n s i d e r e d  t o be  the group most s e n s i t i v e t o oxygen d e f i c i e n c y ( B r u n d i n , 1951; Buck, 1953) and t h e i r r e s u l t i n g o c c u r r e n c e  near the surface  42 p r o v i d e s a p o s s i b l e r e a s o n f o r the absence of t h i s  subfamily  i n b e n t h i c samples and the appearance of l a r v a e i n the emergence t r a p s . C r i c o t o p u s f l a v i b a s i s has i n l a t e May,  two g e n e r a t i o n s , one  the o t h e r a p p e a r i n g as a d u l t s i n l a t e  emerging June-July.  T h i s second g e n e r a t i o n i s most d i s t i n c t i n E a s t L. and Near Phalarope (Figure 9).  I n the two l a k e s r e p r e s e n t i n g the  upper ranges of i t s s a l i n i t y t o l e r a n c e (Round-up L.  and  L. L y e ) , C. f l a v i b a s i s has a n o t h e r emergence peak f r o m mid l a t e August ( F i g u r e 9 ) .  to  T h i s emergence does n o t appear i n  f r e s h e r l a k e s ; whether or n o t i t i s a r e s u l t of a d a p t a t i o n to h i g h s a l i n i t i e s i n the l a t e summer i s n o t  clear.  There i s a g r e a t p a u c i t y o f r e c o r d s f o r C. f l a v i b a s i s i n the l i t e r a t u r e . (1915) who  The  i s t h a t of M a l l o c h  d e s c r i b e d the s p e c i e s from I l l i n o i s .  C. f l a v i b a s i s i s new g)  only record available  to a t l e a s t B.C.  Thus i t seems  and perhaps Canada.  Cricotopus albanus  T h i s v e r y s m a l l s p e c i e s was lakes having conductivities  collected  l e s s than 800 ^imho/cm (Box  B a r k l e y L., E a s t L. and Box 27). seems to be more c l o s e l y  17,  T h i s d i s t r i b u t i o n , however,  a s s o c i a t e d w i t h low pH;  relation i s highly significant (Table V ) .  o n l y i n the f o u r  (p<.01), r being  the c o r -.900  C o r r e l a t i o n s w i t h a l l o t h e r s o l u t e s and measures  of s a l i n i t y a r e n o t s i g n i f i c a n t , but a r e n e g a t i v e i n s i g n .  FIGURE 9  The emergence o f a d u l t s o f f l a v i b a s i s Malloch  and  Cricotopus  Cricotopus  a l b a n u s C u r r a n from the one meter depth zone o f s e v e r a l l a k e s . a logarithmic scale.  The o r d i n a t e i s C o l l e c t i n g began  on May 19, t o o k p l a c e e v e r y f o u r t h day and t e r m i n a t e d on August 29, 1970.  43  ROUND-UP L.  100  BOITANO L.  NEAR PHALAROPE  10  LU UJ LU cc <  o  CRICOTOPUS FLAVIBASIS  EAST L.  CO 100 cc  LU Q.  BOX 27  O  z o  CC  10 J  LU 2 LU (/) b  /  CRICOTOPUS ALBANUS  ZD  a <  T  1  1  o cc  100 q  BOX 17  BARKLEY L.  EAST L.  LU ca  10 1  M  *  J  i  J  A  i  1  i  M  1  1—  J  J  A  1  r  M  J  J  ~i  A  1  44 Emergence i s v a r i a b l e .  I n Box 27 t h e r e i s a main  emergence i n l a t e May and a n o t h e r peak i n m i d June.  In  E a s t L. a s i n g l e peak i n l a t e J u n e - e a r l y J u l y o c c u r s .  As  the s a l i n i t y i n c r e a s e s emergence s h i f t s t o l a t e r i n t h e summer ( F i g u r e 9 ) . T h i s i s e x e m p l i f i e d by a s m a l l emergence i n m i d J u l y i n B a r k l e y L. and a s i m i l a r peak i n Box 17 f o l l o w e d by a much l a r g e r c a p t u r e o f a d u l t s i n l a t e August. Only one r e c o r d ( C u r r a n , 1929) o f t h i s s p e c i e s i s r e p o r t e d f o r Canada.  h)  P s e c t r o c l a d i u s barbimanus  T h i s i s t h e most common o f t h e O r t h o c l a d i i n a e i n t h e lake series.  I t v a r i e s i n s i z e and c o l o r a t i o n and i s  n o t o r i o u s l y v a r i a b l e i n other morphological 1956;  S a e t h e r , 1967).  features  (Wulker,  P. barbimanus corresponds t o  P s e c t r o c l a d i u s sp. B mentioned i n Cannings (1970).  Larvae  were found i n b e n t h i c samples, b u t much l a r g e r numbers were c a p t u r e d i n t h e emergence t r a p s a l o n g w i t h pupae and a d u l t s . T h i s s p e c i e s , e s p e c i a l l y i n L. L y e , h a b i t u a l l y b u i l t  thin  mud tubes on t h e s i d e s o f t h e emergence t r a p s . The  l i f e c y c l e appears t o c o n s i s t o f a s i n g l e  generation  emerging i n l a t e May, a l t h o u g h t h e r e a r e enough e x c e p t i o n s where a m i d J u l y emergence appears (East L., B a r k l e y L., Near P h a l a r o p e ,  B o i t a n o L.) t o c a s t doubt on t h e i d e a o f a  single generation  ( F i g u r e 10).  Indeed, t h e l a t e r emergence i n  B o i t a n o L. i s s u f f i c i e n t l y l a r g e t o foreshadow t h e immense  FIGURE 10  The emergence o f a d u l t s o f P s e c t r o c l a d i u s barbimanus (Edwards) from t h e one meter depth zone o f s e v e r a l lakes.  The o r d i n a t e i s a l o g a r i t h m i c  scale.  C o l l e c t i n g began on May 19, t o o k  p l a c e every f o u r t h day and t e r m i n a t e d August 29, 1970.  i  on  45  100  cc ui  ROUND-UP L.  q  L. LYE  BOITANO L.  10  LU LU CC <  O  ,  w cc  ,  ,  ^  .  v  . r  r-*-"  n  LU  a.  O z  o cc  LU  s LU CO  b  L. JACKSON 100  a  10  J  L. GREER  BARKLEY L.  Q < U.  O  CC LU 303 Z  M  M  M  1  46 emergences i n l a t e J u l y and August from L. Lye and Round-up L. ( F i g u r e 10).  This July-August  emergence i n L. Lye  represents  a t o t a l o f about 190 a d u l t s emerging per square meter. The h i s t o g r a m s  i n d i c a t e t h a t i n the more s a l i n e h a b i t a t s  P. barbimanus i s more abundant and tends to emerge l a t e r i n the summer. occur.  I t appears t h a t i n some l a k e s two g e n e r a t i o n s  may  That i n c r e a s e d s a l i n i t y i s a s s o c i a t e d w i t h a l e s s  s y n c h r o n i z e d emergence i s e v i d e n t from the s i g n i f i c a n t  (p<.01)  c o r r e l a t i o n (Table V I ) . P s e c t r o c l a d i u s barbimanus has been r e p o r t e d o n l y once before i n North America. pupal exuviae  A.L.  Hamilton  (Houghton, Sask., May  c o l l e c t e d 5 males and  5, 1967)  from a s a l i n e  p r a i r i e s l o u g h o f s p e c i f i c c o n d u c t i v i t y 2300 |imhos a t 7.4°C ( S a e t h e r , 1969).  T h i s r e p r e s e n t s an e q u i v a l e n t r e a d i n g of  about 3400 jumhos a t 25°C, o r a p p r o x i m a t e l y L. J a c k s o n or B o i t a n o L.  the c o n d u c t i v i t y o f  Mundie (1957) r e p o r t s P. barbimanus  as an uncommon emerger from the 1 to 3 meter zone.from l a t e A p r i l to l a t e May  i)  i n Kempton P a r k E a s t R e s e r v o i r , London.  Cryptotendipes  ariel  T h i s i s a s p e c i e s d e s c r i b e d by S u b l e t t e (1960) from Californian material.  As f a r as can be e s t a b l i s h e d , i t has  n o t been r e p o r t e d elsewhere.  C. a r i e l i s r e s t r i c t e d to the  f o u r most s a l i n e l a k e s i n the s e r i e s ( c o n d u c t i v i t y '> 4000 umho/cm) ( F i g u r e 11).  I n a l l but Barnes L. t h e r e a r e  g e n e r a t i o n s , one emerging i n l a t e May-early  two  June, the o t h e r i n  FIGURE 11  The emergence o f a d u l t s o f Cryptotendipes a r i e l Calopsectra  ( S u b l e t t e ) and  g r a c i l e n t a (Holmgren) from  the one meter depth zone o f s e v e r a l The o r d i n a t e  i s a logarithmic  lakes.  scale.  C o l l e c t i n g began on May 19, t o o k p l a c e every f o u r t h day and t e r m i n a t e d on August 29, 1970.  47  BARNES  L  ROUND-UP  L  L. LYE  100 :  10 :  CC LU UJ  1  1  r  2  Ul  cc  <  o <n cc LU a o z C5  BOITANO L.  30 10  CRYPTOTENDIPES ARIEL  BARNES L.  /  _  -  CC LU  /  / /  -  CALOPSECTRA GRACILENTA  LU  <n H _i  1  Q 400  100 z  LU CD  ROUND-UP L.  -  o rr  NU  <LL  BOITANO L  L. LYE  10:  M  — r —  i  M  J  J  A  M  J  1  J  1  A  48 August.  The numbers i n B o i t a n o L. and L. Lye a r e s m a l l , b u t  i n Round-up L. a v e r y l a r g e emergence (500 p e r square m e t e r ) appears i n l a t e J u l y through August a f t e r a s m a l l ( o v e r w i n t e r ing  p o p u l a t i o n ) a d u l t emergence i n May.  I n Barnes L. t h e  August emergence i s c o m p l e t e l y l a c k i n g and t h e c o n s i d e r a b l e l a t e May emergence c a r r i e s over w e l l i n t o June. Table V I shows t h e tendency o f t h e emergence p a t t e r n t o spread over a l o n g e r p e r i o d as t h e c o n d u c t i v i t y i n c r e a s e s (r= .914 ; p < .01).  The p o s s i b i l i t y e x i s t s t h a t t h e i n c r e a s i n g  s a l i n i t y o f Barnes L. d u r i n g t h e summer e v a p o r a t i o n p e r i o d prevents  t h e l a r v a e o f t h e summer g e n e r a t i o n from  developing  r a p i d l y enough t o emerge b e f o r e September. j)  Calopsectra gracilenta  This species of the o l d Tanytarsus  ( s e n s . l a t . ) genus i s  the most abundant s p e c i e s c o l l e c t e d i n t h e t r a p s . May-early  The l a t e  June emergence i n B o i t a n o L. a l o n e reached a d e n s i t y  o f about 1000 p e r square meter ( F i g u r e 11).  I n L. Lye t h e r e i s  a maximum o f t h r e e g e n e r a t i o n s , t h e emergences i n c r e a s i n g i n s i z e as t h e season p r o g r e s s e s .  I n B o i t a n o L. o n l y a s l i g h t  emergence o c c u r s i n e a r l y J u l y a f t e r t h e major May emergence. In Round-up L., C. g r a c i l e n t a r e p e a t s t h e L. L y e p a t t e r n w i t h out t h e J u n e - J u l y emergence.  I n Barnes L. t h e numbers a r e  v e r y s m a l l , o n l y 12 p e r square meter emerging i n v e r y l a t e June. C. g r a c i l e n t a i s a c i r c u m p o l a r s p e c i e s , i n N o r t h A m e r i c a b e i n g r e p o r t e d o n l y from E l l e s m e r e I s l a n d ( O l i v e r , 1963),  49  B a f f i n I s l a n d ( O l i v e r , 1964) ( M c A l p i n e , 1964).  The  and E l l e f Ringes I s l a n d  s p e c i e s i s a l s o known from c o n t i n e n t a l  and a r c t i c Europe ( L i n d e b e r g , 1968).  I n F i n l a n d i t has been  taken from the G u l f of B o t h n i a i n s h a l l o w b r a c k i s h w a t e r (3-4 °/oo)  but has n o t been c o l l e c t e d a t Tvarminne (6  ( L i n d e b e r g , 1968).  °/oo)  F o r comparison, Barnes L. has a s a l i n i t y of  10 / oo, so t h a t i t appears C. g r a c i l e n t a can i n h a b i t w a t e r s u  more s a l i n e Lindeberg  (and p r o b a b l y warmer) than p r e v i o u s l y r e p o r t e d .  (1968) a l s o r e p o r t s an I c e l a n d i c p o p u l a t i o n w i t h a  J u l y emergence peak.  k)  Derotanypus a l a s k e n s i s  This i s a very widespread boreal species. g i v e s no B.C.  r e c o r d s a l t h o u g h h i s map  Roback (1971)  i n d i c a t e s the range  p r o b a b l y extends over the n o r t h e r n h a l f o f the p r o v i n c e . i s the dominant m a c r o p e l o p i a n  i n the l a k e s e r i e s and  r e p r e s e n t s a l a r g e p a r t of the predaceous c h i r o n o m i d  This  probably fauna.  I n the l a k e s e r i e s D. a l a s k e n s i s has been found i n a l l l a k e s a l t h o u g h emergence was Box 27. May  n o t r e c o r d e d i n Barnes L.  or  I n a l l the l a k e s except Sorenson L. t h e r e i s a l a t e  emergence ( F i g u r e s 12, 13).  A v e r y s m a l l emergence i n  l a t e J u l y - e a r l y August i n Sorenson L. i s accompanied by a drop i n the f o u r t h i n s t a r l a r v a l numbers from 400 meter.  The  t h a t a May  to 200 per square  l a c k o f f o u r t h i n s t a r l a r v a e i n l a t e May i n d i c a t e s emergence p r o b a b l y o c c u r r e d i n Sorenson L a k e , but  took p l a c e b e f o r e May  19th when the t r a p s were put i n p l a c e .  FIGURE 12  L a r v a l abundance and a d u l t emergence of Derotanypus a l a s k e n s i s  (Malloch)  i n L. L y e , B o i t a n o L. and L. J a c k s o n .  A.  Third  (  ) and f o u r t h (  )  i n s t a r numbers p e r square meter a t weekly B.  intervals.  A d u l t emergence:  numbers p e r square  meter t a k e n every f o u r t h day. C.  The p e r c e n t a g e o f the t o t a l chironomid population  larval  represented  by D. a l a s k e n s i s l a r v a e .  o  FIGURE 13  L a r v a l abundance and a d u l t emergence o f Derotanypus a l a s k e n s i s ( M a l l o c h ) i n Rock L., Sorenson L. and E a s t L.  A.  Third (  ) and f o u r t h (  )  i n s t a r numbers per square meter at weekly B.  intervals.  A d u l t emergence:  numbers p e r  square meter taken every f o u r t h day. C.  The percentage  o f the t o t a l  larval  c h i r o n o m i d p o p u l a t i o n r e p r e s e n t e d by D.alaskensis larvae.  52 The o v e r w i n t e r i n g f o u r t h i n s t a r l a r v a e a r e no doubt accounted  f o r by t h i s u s u a l l y l a r g e emergence i n l a t e  May.  I n the more s a l i n e l a k e s ( F i g u r e 12) t h e r e i s an even l a r g e r emergence l a t e r i n the summer.  This represents  per square meter i n L. J a c k s o n from June 21 to J u l y The  100  27.  second g e n e r a t i o n emergence i s d e l a y e d i n the h i g h e r  s a l i n i t i e s perhaps owing t o c o n c e n t r a t i o n i n c r e a s e s as summer p r o g r e s s e s .  The  the  s i t u a t i o n i n B o i t a n o L. appears to  be i n t e r m e d i a t e a l t h o u g h the l a r v a l abundance curve 12) suggests a t h r e e g e n e r a t i o n s i t u a t i o n .  (Figure  I n summary,  D. a l a s k e n s i s appears to have a t l e a s t one g e n e r a t i o n per y e a r i n the f r e s h e r w a t e r s , w h i l e i n more s a l i n e l a k e s , d e f i n i t e l y two and i n a t l e a s t one case t h r e e generations occur.  (Boitano)  F i g u r e s 12 and 13 show D. A l a s k e n s i s  i s most abundant i n mid  summer, e s p e c i a l l y i n J u l y .  I n L.  Lye  i t makes up 60 per cent o f the c h i r o n o m i d community i n e a r l y J u l y , i n Sorenson L.,  25 per c e n t .  Thus i t s e f f e c t on  prey  s p e c i e s , a t l e a s t l a r g e ones, s h o u l d be g r e a t e s t a t t h i s time.  In g e n e r a l , numbers of D. a l a s k e n s i s a r e sparse i n the  fresher lakes.  1)  E i n f e l d i a pagana  T h i s i s the most abundant o f a l l the s p e c i e s c o l l e c t e d i n the l a k e s e r i e s .  I n a l l l a k e s , owing to i t s r e l a t i v e l y  l a r g e numbers ( f o u r t h i n s t a r l a r v a e a l o n e sometimes  exceeding  40,000 per square meter i n Near O p p o s i t e C r e s c e n t ) , E. pagana  53 r e p r e s e n t s a l a r g e p r o p o r t i o n of the fauna  ( F i g u r e s 14,  Numbers a r e lower i n Westwick L. and Sorenson L. 1000  15).  (500 to  per square m e t e r ) w h i l e they a r e h i g h e r i n medium-high  and medium-low s a l i n i t i e s  ( a v e r a g i n g about 10,000 to 11,000  per square m e t e r ) . The  l a r v a e p r o b a b l y o v e r w i n t e r i n the t h i r d and f o u r t h  i n s t a r s ; the f i r s t emergence o f the y e a r b e g i n n i n g i n e a r l y June.  I n F i g u r e 14 i t i s e v i d e n t t h a t these.emergences a r e  v e r y d i s c r e e t (though o c c u r r i n g over 3 or 4 weeks).  I n the  f r e s h e r l a k e s ( F i g u r e 15) a second g e n e r a t i o n emerges.  The  r e l a t i o n s h i p between c o n d u c t i v i t y and the number of emergence peaks (-.424) (Table X) s u p p o r t s t h i s f a c t .  In the v e r y f r e s h  E a s t L. the two emergence peaks a r e found on e a r l i e r a g a i n i n d i c a t i n g t h a t t h i s s p e c i e s may  dates  develop more s l o w l y i n  l a k e s of h i g h e r c o n c e n t r a t i o n .  S i m i l a r l y , T a b l e V I I I shows  t h a t the g r e a t e r the percentage  o f E. pagana p r e s e n t , the  lower  the c o n d u c t i v i t y , T.D.S. and c o n c e n t r a t i o n s of sodium, HCO3 and CO^.  I n these cases the c o e f f i c i e n t s a r e -.639, -.614,  -.658, -.645 at  p <.05  and  and  -.589  -.641  r e s p e c t i v e l y where -.514  a t p <.01.  is significant  I t i s i n t e r e s t i n g that u n l i k e  o t h e r E i n f e l d i a pagana l a r v a e ( O l i v e r , 1971  B ) , the l a r v a e o f  E. pagana c o l l e c t e d i n t h i s study l a c k v e n t r a l t u b u l e s i n a l l instars.  T h i s phenomenon i s a l s o apparent  i n some l a r v a l  types  of Chironomus, n o t a b l y C. s a l i n a r i u s where the same m o r p h o l o g i cal  s p e c i e s may  comm.).  possess or l a c k b l o o d g i l l s  S i n c e i t i s thought  (0. S a e t h e r ,  t h a t these s t r u c t u r e s a r e  pers.  54 f u n c t i o n a l i n osmotic r e g u l a t i o n (Wigglesworth,  1933;  S u t c l i f f e , 1960), i t i s p o s s i b l e t h a t the l a c k o f t u b u l e s i s an a d a p t a t i o n a l l o w i n g E. pagana t o c o l o n i z e more conc e n t r a t e d w a t e r s than i s u s u a l l y the case.  Wigglesworth  (1933), who n o t e s t h a t d i p t e r o u s s p e c i e s l i v i n g i n s a l i n e environments (both n a t u r a l l y and i n e x p e r i m e n t a l s i t u a t i o n s ) tend t o have r e d u c e d t u b u l e s , b e l i e v e s t h a t the t u b u l e s a r e the o n l y h i g h l y permeable a r e a s of the body, and thus the r e s i s t a n c e o f l a r v a e t o h i g h osmotic  p r e s s u r e s w i l l be f a v o r e d  by the r e d u c t i o n o f these s t r u c t u r e s .  P h i l l i p s and M e r e d i t h  (1969), however, have shown t h a t i n the s a l t w a t e r mosquito Aedes c a m p e s t r i s the a n a l p a p i l l a e a r e m o r p h o l o g i c a l l y  similar  t o those i n f r e s h w a t e r s p e c i e s and a r e p r o b a b l y a b l e t o a c t i v e l y t r a n s p o r t i o n s i n and o u t o f the body. I n most l a k e s the f o u r t h i n s t a r p o p u l a t i o n s a r e a t t h e i r s m a l l e s t from l a t e June t o e a r l y August.  Throughout the  summer the l a r v a l c o m p o s i t i o n o f E. pagana and b a r b i p e s shows an a l m o s t i n v e r s e r e l a t i o n s h i p 16 and 1 7 ) .  Glyptotendipes ( F i g u r e s 14, 15,  T h i s may be due t o the f a c t t h a t these two s p e c i e s  a r e adapted t o the same c o n d i t i o n s .  I n l a k e s where they a r e  abundant these two s p e c i e s make up a l m o s t 100 p e r c e n t of the i n d i v i d u a l s present.  I f the p e r c e n t a g e c o m p o s i t i o n o f one  i n c r e a s e s , the p e r c e n t a g e c o m p o s i t i o n o f the o t h e r  decreases.  That the two s p e c i e s a r e s i m i l a r l y adapted i s e v i d e n c e d  by  the c o r r e l a t i o n c o e f f i c i e n t s between t h e i r abundances (.808) (Table V I I ) and t h e i r per c e n t c o m p o s i t i o n both s i g n i f i c a n t a t p < . 0 1 .  (.645) (Table V I I I ) ,  FIGURE 14  L a r v a l abundance and a d u l t emergence of E i n f e l d i a pagana Meigen i n L.  Jackson,  Rock L. and Westwick L.  A.  Third (  ) and f o u r t h  (——)  i n s t a r numbers per square meter a t weekly B.  intervals.  A d u l t emergence:  numbers per square  meter taken every f o u r t h day. C.  The percentage  o f the t o t a l l a r v a l  c h i r o n o m i d p o p u l a t i o n r e p r e s e n t e d by E. pagana l a r v a e .  FIGURE 15  L a r v a l abundance and a d u l t emergence of E i n f e l d i a  pagana Meigen i n Near  O p p o s i t e C r e s c e n t , B a r k l e y L. and E a s t L.  A.  Third (  ) and f o u r t h ( — -  ) instar  numbers per square meter a t w e e k l y intervals. B.  A d u l t emergence: numbers per square meter taken every f o u r t h day.  C.  The percentage  o f the t o t a l  larval  c h i r o n o m i d p o p u l a t i o n r e p r e s e n t e d by E. pagana l a r v a e .  57 m)  Glyptotendipes barbipes  Found i n a l l t h e l a k e s , G. b a r b i p e s shows s p o r a d i c o c c u r r e n c e i n t h e h i g h e r s a l i n i t i e s and i s most abundant i n t h e range from 500 t o 3000 umho/cm.  In these l a k e s i t  r e a c h e s a maximum o f about 1 1 , 0 0 0 p e r square meter.  The  o v e r w i n t e r i n g l a r v a e emerge i n l a t e May i n a l l l a k e s . Rock L. and E a s t L. t h i s i n i t i a l emergence extends e a r l y June.  into  A second g e n e r a t i o n emerges a t d i f f e r e n t  i n d i f f e r e n t l a k e s , u s u a l l y i n mid o r l a t e J u l y .  In  times  The  s i t u a t i o n i n L. J a c k s o n and i n Rock L. ( t o a l e s s e r degree) i s somewhat d i f f e r e n t .  I t i s n o t t o o c l e a r whether t h e  second emergence i s a s e p a r a t e g e n e r a t i o n o r s i m p l y t h e emergence o f s l o w e r d e v e l o p i n g o v e r w i n t e r i n g f o u r t h i n s t a r l a r v a e ( F i g u r e s 16 and 17).  The s m a l l August 29 emergence  i n E a s t L. may be t h e b e g i n n i n g . o f a l a r g e r t h i r d g e n e r a t i o n emergence. That G. b a r b i p e s appears t o be more abundant and dominant i n t h e l o w e r s a l i n i t i e s emphasizes t h e f a c t t h a t t h e s p e c i e s has more g e n e r a t i o n s i n f r e s h e r w a t e r s . tion coefficients between p e r c e n t a g e  A l l correla-  (Table V I I I ) m e a s u r i n g t h e r e l a t i o n s h i p c o m p o s i t i o n and c o n d u c t i v i t y  T.D.S. (-.613), sodium (-.628), C 0 are s i g n i f i c a n t a t p<.05.  3  (-.626),  (-.543) and HCO3  (-.576)  The number o f emergence peaks 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 c o n d u c t i v i t y , T.D.S., sodium, C0o and HCOo (Table X ) .  FIGURE 16  L a r v a l abundance and a d u l t emergence of G l y p t o t e n d i p e s b a r b i p e s  (Staeger)  i n L. J a c k s o n , Westwick L. and Sorenson L.  A.  Third (  ) and f o u r t h ( — -  )  instar  numbers per square meter a t w e e k l y intervals. B.  A d u l t emergence:  numbers per  meter taken every f o u r t h C.  The percentage  square  day.  o f the t o t a l  larval  c h i r o n o m i d p o p u l a t i o n r e p r e s e n t e d by G. b a r b i p e s l a r v a e .  FIGURE 17  L a r v a l abundance and a d u l t emergence of G l y p t o t e n d i p e s b a r b i p e s  (Staeger)  i n Rock L., B a r k l e y L. and E a s t L.  A.  Third (  ) and f o u r t h ( —  )  i n s t a r numbers p e r square meter a t weekly B.  intervals.  A d u l t emergence:  numbers p e r square  meter t a k e n every f o u r t h day. C.  The percentage  of the t o t a l  larval  c h i r o n o m i d community r e p r e s e n t e d by G. b a r b i p e s l a r v a e .  Larval Composition ( % )  No. emerging per sq.m  No. larvae per sq.m  VO  60 The  time of the main emergence i s l a t e r i n f r e s h e r  waters; c o e f f i c i e n t s i n d i c a t i n g t h i s are s i g n i f i c a n t a t the 99 per c e n t l e v e l  (Table X I ) .  T h i s i s u n l i k e the  cases of E. pagana and D. a l a s k e n s i s , but may a d a p t a t i o n s to h i g h e r s a l i n i t i e s .  r e s u l t from  For example, i t may  r e f l e c t a tendency of G. b a r b i p e s p o p u l a t i o n s to complete development e a r l y to a v o i d the h i g h e r s a l i n i t i e s o f l a t e summer.  I n t h i s c o n t e x t i t s h o u l d a l s o be n o t e d t h a t i n  h i g h e r s a l i n i t i e s the synchrony  o f emergence i s g r e a t e r than i n  lower ones (-.559) (Table V I ) . On the w h o l e , G. b a r b i p e s i s most abundant i n mid summer ( J u l y ) a f t e r f o u r t h i n s t a r l a r v a e have developed the i n i t i a l May m a t i n g s .  from  Throughout the l a k e s abundance i s  v e r y s i g n i f i c a n t l y c o r r e l a t e d to the abundance o f D. a l a s k e n s i s (.785) and E. pagana (.808)  n)  Chironomus a n t h r a c i n u s  Although California  t h i s s p e c i e s has been r e c o r d e d from A l b e r t a and  (Stone e t a l , 1956), t h e r e a r e no r e c o r d s from  B r i t i s h Columbia.  T h i s i s one o f the t h r e e Chironomus s p e c i e s  commonly found i n the l a k e s e r i e s .  A t one meter o f depth  l a r v a l d e n s i t y ranges from 100 t o 1000 The  the  per square meter.  s p e c i e s i s e v i d e n t l y most c h a r a c t e r i s t i c o f  e u t r o p h i c p r o f u n d a l s (Lundbeck, 1926;  Berg, 1938)  and i s o f t e n  r e g a r d e d as an i n d i c a t o r of low oxygen c o n d i t i o n s ( B r u n d i n , 1951).  S i n c e Topping (1969), c a l l i n g i t Chironomus sp.  A,  61 showed C. a n t h r a c i n u s was  p r e v a l e n t a t depths g r e a t e r than  two meters i n the l a k e s under c o n s i d e r a t i o n , i t i s p o s s i b l e t h a t the main p o p u l a t i o n emergences were m i s s e d by  the  t r a p p i n g i n the p r e s e n t r e s e a r c h , the p o p u l a t i o n s  sampled  b e i n g p e r i p h e r a l ones.  emergence  i s recorded  I n the l a k e s where no May  i t i s p o s s i b l e t h a t emergence o c c u r r e d  the t r a p s were p l a c e d i n p o s i t i o n . i n s t a r l a r v a e i n May cate t h i s .  The  The  before  low l e v e l s of f o u r t h  i n B o i t a n o L. and Sorenson L. may  s p e c i e s i s n o t o b v i o u s i n Rock L.  i t appears t h a t C. a n t h r a c i n u s u s u a l l y has one emergence p a t t e r n s a r e e x t r e m e l y  indi-  Although  generation,  v a r i a b l e ( F i g u r e s 18 and  19).  T h i s i s i n accordance w i t h Thienemann (1951) who r e c o r d e d v a r i a t i o n s i n the time of y e a r C. a n t h r a c i n u s a t a n o r t h German l a k e .  Mundie (1957) found the  swarmed  species  u n i v o l t i v e i n S t a i n s South R e s e r v o i r , London, where A p r i l emergences predominated a l t h o u g h caught.  some September a d u l t s were  I n Lake Esrom, Denmark, Jonasson (1954) found a month-  l o n g emergence p e r i o d w i t h a mode on May  10, 1954.  I n the  lakes  s t u d i e d h e r e i n , the amount of C. an t h r a c i n u s emergence i s c o r r e l a t e d w i t h the c o n c e n t r a t i o n of magnesium ( p < . 0 1 ) (Table I X ) . I n Rock L., chironomid  C. a n t h r a c i n u s makes up a major p a r t o f  f a u n a i n J u l y and August ( F i g u r e 18).  one meter i n Westwick L. and Sorenson L. a r e low The  Levels at ( F i g u r e 19).  s p e c i e s i s most abundant i n the h a b i t a t s p r e f e r r e d by  E. pagana (Table V I I ) .  the  FIGURE 18  L a r v a l abundance and a d u l t emergence of Chironomus a n t h r a c i n u s Z e t t e r s t e d t i n B o i t a n o L., L. J a c k s o n and Rock L.  A.  F o u r t h i n s t a r numbers p e r square meter a t w e e k l y i n t e r v a l s .  B.  A d u l t emergence:  numbers p e r  square meter t a k e n every f o u r t h day. C.  The percentage  o f the t o t a l  larval  chironomid population represented by C. a n t h r a c i n u s l a r v a e .  FIGURE 19  L a r v a l abundance and a d u l t emergence o f Chironomus a n t h r a c i n u s Z e t t e r s t e d t i n Sorenson L., B a r k l e y L. and E a s t L.  A.  F o u r t h i n s t a r numbers per square meter taken a t w e e k l y  B.  A d u l t emergence:  intervals.  numbers per  square meter taken every f o u r t h day. C.  The percentage  o f the t o t a l  larval  chironomid population represented C. a n t h r a c i n u s l a r v a e .  by  Larval Composition ( / ) 0  o  No. emerging per sq.m  No. larvae per sq.m  64 o)  Chironomus n.  sp.  This i s a h i t h e r t o undescribed  s p e c i e s t h a t keys out near  C. a t r i t i b i a M a l l o c h i n the keys of Townes (1945). d e s c r i b e d by S u b l e t t e who  i s now  It w i l l  be  r e v i s i n g the N o r t h American  Chironomus u s i n g g i a n t chromosome c h a r a c t e r s .  Bassett  (1967)  c a l l e d t h i s Chironomus s p e c i e s h i s S p e c i e s V and n o t e d t h a t i t s chromosomes d i s p l a y e d e x t e n s i v e p a i r i n g between centromeres. T h i s , a l o n g w i t h o t h e r c h a r a c t e r s such as b a n d i n g p a t t e r n , separates  the new  s p e c i e s c y t o l o g i c a l l y from s i m i l a r  l i k e C. a n t h r a c i n u s  (Bassett's Species I V ) .  The  species  r e c o r d e d by Topping (1969) under Chironomus sp. B as most abundant below a depth of two m e t e r s .  species was  being  I t i s the most  common of the Chironomus s p e c i e s i n the l a k e s ; moreover, i t s t o l e r a n c e of h i g h s a l i n i t i e s  i s much g r e a t e r than t h a t of  o t h e r members of the genus c o n s i d e r e d h e r e i n .  Indeed, t h i s  s p e c i e s r e a c h e s i t s g r e a t e s t abundance i n Barnes L. 20) where i t i s by f a r the dominant nonpredaceous The  (Figure chironomid.  s p e c i e s makes up a l m o s t 100 per cent of the f o u r t h i n s t a r  chironomid  fauna i n l a t e summer.  T a b l e V I I shows the r e l a t i o n s h i p between the abundance of t h i s s p e c i e s and i o n c o n c e n t r a t i o n .  Correlations with  c o n d u c t i v i t y , T.D.S., sodium, c a r b o n a t e and concentrations are p o s i t i v e (p<.01).  The  bicarbonate correlation with  the c o n c e n t r a t i o n of s u l f a t e i s s i g n i f i c a n t a t p < . 0 5 . In most l a k e s the i n i t i a l emergence o c c u r s i n May. Sorenson L. the l a c k of f o u r t h i n s t a r l a r v a e i n May  In  suggests  65 an e a r l y emergence. well.  Here t h e r e i s an August emergence as  I n Barnes L. a l l t h e a d u l t s emerging from May t o  e a r l y J u l y p r o b a b l y a r e from t h e same o v e r w i n t e r i n g generation.  A p o r t i o n o f t h e f o u r t h i n s t a r p o p u l a t i o n may p r o l o n g  diapause  and n o t emerge u n t i l June and e a r l y J u l y .  The  r e c r u i t m e n t o f t h e new g e n e r a t i o n t h i r d i n s t a r l a r v a e i n t o the ranks o f t h e f o u r t h i n s t a r keeps t h e l e v e l o f t h e l a t t e r r i s i n g even though c o n s i d e r a b l e emergence i s o c c u r r i n g .  The  m a j o r i t y o f new g e n e r a t i o n l a r v a e a r e n o t f o u r t h i n s t a r  size  before the middle  o f J u l y , however, so t h a t emergence b e f o r e  t h i s time i s a l m o s t c e r t a i n l y due t o o v e r w i n t e r i n g a d u l t s . Thus a l l a d u l t s a p p e a r i n g a f t e r m i d J u l y a r e p r o b a b l y o f t h e new g e n e r a t i o n , and t h e drop i n f o u r t h i n s t a r l a r v a e numbers a t t h i s time  (10,000 down t o 5,000 p e r square m e t e r ) i s a r e -  s u l t o f t h i s emergence.  I t i s probable  that the remaining  f o u r t h i n s t a r l a r v a e o v e r w i n t e r a l o n e i n Barnes L. ( s i n c e i t i s u n l i k e l y t h a t another  g e n e r a t i o n o f f o u r t h i n s t a r s can be  produced d u r i n g t h e s h o r t f a l l ) o r w i t h second o r t h i r d  instars.  I f t h e s m a l l e r i n s t a r s do manage t o o v e r w i n t e r , they may be the i n d i v i d u a l s emerging t h e n e x t y e a r i n June, t h e o v e r w i n t e r i n g f o u r t h i n s t a r s emerging i n May.  I n some o f t h e l a k e s  ( B o i t a n o L., L. J a c k s o n , Rock L. and East L.) o n l y one generat i o n i s observed  ( F i g u r e s 20,21 and 2 2 ) .  As p r e v i o u s l y mentioned, t h i s new s p e c i e s o f Chironomus i s p a r t i c u l a r l y i n t e r e s t i n g because o f i t s u n i q u e  domination  of Barnes L., t h e most s a l i n e l a k e ( c o n d u c t i v i t y about 12,000 umho/cm) i n t h e study.  The o t h e r s p e c i e s o f Chironomus were  FIGURE 20  L a r v a l abundance and a d u l t emergence of Chironomus n. sp. i n Barnes L., B o i t a n o L. and L.  A.  Jackson.  F o u r t h i n s t a r numbers per meter a t w e e k l y  B.  A d u l t emergence:  intervals. numoers per  meter t a k e n e v e r y f o u r t h C.  square  square  day.  The percentage o f the t o t a l  larval  chironomid population represented by Chironomus n. sp. l a r v a e .  Larval Composition  (%)  No. emerging per sq.m  No. larvae per sq.m  FIGURE 21  L a r v a l abundance and a d u l t emergence o f Chironomus n. sp. i n Rock L. and Sorenson L.  A.  F o u r t h i n s t a r numbers p e r square meter a t w e e k l y  B.  intervals.  A d u l t emergence:  numbers p e r  square meter t a k e n every f o u r t h day. C.  The percentage  of the t o t a l  larval  chironomid population represented by Chironomus n. sp. l a r v a e .  FIGURE 22  L a r v a l abundance and a d u l t emergence of Chironomus n. sp. i n B a r k l e y L. and E a s t L.  A.  F o u r t h i n s t a r numbers p e r square meter a t w e e k l y  B.  A d u l t emergence:  intervals. numbers p e r  square meter taken every f o u r t h day. C.  The percentage o f the t o t a l l a r v a e chironomid population represented by Chironomus n. sp. l a r v a e .  69 n o t c o l l e c t e d h e r e , a l t h o u g h two u n i d e n t i f i e d l a r v a e o f d i f f e r e n t s p e c i e s , Chironomus sp. C and Chironomus sp. D o c c u r i n v e r y low numbers (Table I V ) . The g r e a t abundance and l a r g e emergence o f Chironomus s p e c i e s i n Barnes L. i s p r o b a b l y due  this to b o t h i t s  s u c c e s s f u l a d a p t a t i o n t o the c h e m i c a l l y r i g o r o u s environment and t o a c o n s i d e r a b l e r e d u c t i o n i n c o m p e t i t i o n from s i m i l a r species.  I t i s n o t a b l e t h a t the per c e n t c o m p o s i t i o n  and  abundance o f t h i s s p e c i e s a r e c o r r e l a t e d w i t h the i n d e x of diversity  (Tables V I I and V I I I ) .  The  emergence p a t t e r n  d i f f e r s from t h a t i n l a k e s where C. a n t h r a c i n u s , C. and C. plumosus o c c u r .  The  tentans  tendency f o r the emergence p a t t e r n  to spread out i n h a b i t a t s h a v i n g a h i g h i n d e x o f d i v e r s i t y i s r e f l e c t e d i n the c o r r e l a t i o n c o e f f i c i e n t -.603  (p<£.05)  (Table V I ) .  p)  Chironomus t e n t a n s  T h i s s p e c i e s i s common, but n o t abundant i n the range o f c o n d u c t i v i t i e s from 500 t o 3000 jumho/cm. i n B o i t a n o L. numbers.  middle  I t occurs  ( c o n d u c t i v i t y 4108 umho/cm) i n o n l y v e r y s m a l l  I n most l a k e s the d e n s i t y o f f o u r t h i n s t a r l a r v a e  n e v e r exceeds 300 per square meter, making the s p e c i e s o n l y a minor component of the community as f a r as p e r c e n t a g e composit i o n i s concerned ( F i g u r e s 23 and 24).  C. t e n t a n s has i t s  g r e a t e s t development a t one meter i n Sorenson L. where f o u r t h i n s t a r l a r v a e number 1000  to 1500  per square meter.  r e l a t i v e l y low d e n s i t i e s , however, a r e s u f f i c i e n t t o  These enable  70 C. t e n t a n s to comprise 35 per c e n t (Westwick L.) and 50 per  c e n t (Sorenson L.) o f t h e c h i r o n o m i d f a u n a . The amount o f emergence  i s s m a l l i n most l a k e s , u s u a l l y  under 10 per square meter and u s u a l l y o c c u r s i n l a t e  May.  In Westwick L. t h i s May emergence i s s p r e a d o v e r 28 days and r e p r e s e n t s an emergence o f about 20 a d u l t s per square meter o v e r 4 days d i r e c t l y a f t e r the t r a p s were s e t ; t h e r e f o r e t h i s may be the end o f a l a r g e r emergence earlier.  I n t h e l a t e J u l y emergence  beginning  t h i s trend i s reversed,  Westwick L. h a v i n g 2 per square meter o v e r 20 days.  The  number o f days between the medians o f the emergence peaks i n Westwick L. i s 56, i n Sorenson L. 68 and i n Rock L. 37. o  At  25 C i n the l a b o r a t o r y the i n s e c t s have been r e a r e d t o the a d u l t i n 44 days (16 h o u r s l i g h t , 8 h o u r s d a r k ) (Pat C o l l e n , p e r s . comm.) and a t the same t e m p e r a t u r e S a d l e r  (1935)  r e p o r t e d g e n e r a t i o n s o f 35 to 45 days. Chironomus t e n t a n s b e g i n s development when the w a t e r temperature r e a c h e s 10°C  ( S a d l e r , 1935; A c t o n , p e r s . comm.).  The number o f a c c u m u l a t e d degree days between the f i r s t date on w h i c h 10°C was r e c o r d e d and the d a t e o f the i n i t i a l emergence may t h u s be c a l c u l a t e d (Table X I I I ) u s i n g F i g u r e 5. o 10 C was r e a c h e d d u r i n g the l a s t days o f A p r i l and the f i r s t j  days o f May and the f i r s t r e c o r d e d emergences began i n t h e t h i r d and f o u r t h weeks o f May  (Table X I I I ) .  The a c c u m u l a t e d  day degrees f o r the development o f the o v e r w i n t e r i n g f o u r t h i n s t a r l a r v a e amount t o 249.75 i n Westwick L., 266.0 i n Sorenson L. and 441.25 i n Rock L.  The f a c t t h a t t h e second  71 emergence peak came most q u i c k l y  (37 days and 648.25 day  d e g r e e s ) i n Rock L. i s r a t h e r s u r p r i s i n g . The  i n t e r p r e t a t i o n t h a t t h e J u l y emergences i n  L. J a c k s o n , B a r k l e y L. and E a s t L. a r e due t o t h e progeny of o v e r w i n t e r i n g l a r v a e i s b e i n g t a k e n .  The low o r d e c r e a s i n g  numbers o f f o u r t h i n s t a r l a r v a e i n l a t e May i n d i c a t e t h a t emergence p r o b a b l y o c c u r r e d b e f o r e May 19.  I t i s possible  t h a t emergence i n these t h r e e l a k e s was postponed  because o f  s e r i o u s c o m p e t i t i o n o r l a c k o f f a v o r e d f o o d . There b e i n g l i t t l e o r no d i f f e r e n c e i n temperature  regimes and day l e n g t h  changes among t h e l a k e s , these v a r i a b l e s can h a r d l y be t h e cause o f d i f f e r e n c e s i n developmental  rate.  Other  factors  must be p r o d u c i n g v a r i a t i o n i n t h e l i f e c y c l e o f C. t e n t a n s . The o n l y p h y s i c o - c h e m i c a l parameters  correlating with  abundance and p e r c e n t c o m p o s i t i o n o f C. t e n t a n s a r e oxygen and o r g a n i c carbon l e v e l s .  D i s s o l v e d oxygen c o r r e l a t e d w i t h  abundance a t -.578 (Table V I I ) and w i t h p e r cent c o m p o s i t i o n a t -.651 (Table V I I I ) .  There i s a r e l a t i o n s h i p between  o r g a n i c carbon and abundance (.547) and per c e n t c o m p o s i t i o n (.648). A l t h o u g h t h e abundance o f C. t e n t a n s i s r e l a t e d t o environmental f a c t o r s i n f l u e n c i n g other species i n s i m i l a r ways, t h e r e i s no c l e a r c u t r e l a t i o n s h i p between the abundance or percentage c o m p o s i t i o n o f C. t e n t a n s and t h a t o f p o t e n t i a l competing s p e c i e s .  72 C. t e n t a n s abundance i n May, however, i s c o r r e l a t e d w i t h the May abundance o f C. a n t h r a c i n u s and G l y p t o t e n d i p e s barbipes.  T h i s may have f u r t h e r i n f l u e n c e on subsequent  s p a c i n g o f emergence p e r i o d s . There a r e t h r e e groups o f predaceous c h i r o n o m i d s  that  may a f f e c t C. t e n t a n s - the s e v e r a l P r o c l a d i u s s p e c i e s , Derotanypus a l a s k e n s i s and Cryptochironomus  psittacinus.  No s i g n i f i c a n t r e l a t i o n s h i p between these p r e d a t o r s and C. t e n t a n s ( r e g a r d i n g abundance o r per cent c o m p o s i t i o n ) i s suggested by the c o r r e l a t i o n s t u d i e s ( T a b l e s V I I and V I I I ) . As e x p e c t e d , the amount o f emergence throughout the summer i s dependent on the abundance o f the l a r v a e (.536). T h i s i s f u r t h e r c h a r a c t e r i z e d by the c o r r e l a t i o n o f the J u l y emergence w i t h the abundance (.762) and the percentage p o s i t i o n (.710) o f l a r v a e p r e s e n t i n June. amount o f May emergence determines  com-  I n a d d i t i o n , the  t h e abundance o f l a r v a e  i n June (.590) and J u l y (.670) as w e l l as the June (.841) and July  (.992) percentage  composition.  These a r e v e r y b a s i c  r e s u l t s r e f l e c t i n g the g e n e r a t i o n time o f C. t e n t a n s . The number o f emergence peaks i s c o r r e l a t e d w i t h abundance (.586) and per c e n t c o m p o s i t i o n summer. .724.  (.703) throughout the  I n May the c o e f f i c i e n t i s .589 and i n J u l y i t i s The i n i t i a l May emergence and the i n d e x o f d i v e r s i t y  f o r May a r e c o r r e l a t e d  (r.540), the emergence b e i n g much  l a r g e r i n l a k e s h a v i n g lower  diversity.  73 The emergences o f C. t e n t a n s n e v e r o c c u r a t t h e same time as those o f C. a n t h r a c i n u s and  n. sp.  I n Sorenson  L. , f o r example, where a t one meter C. t e n t a n s i s completelydominant, a l a t e May C. t e n t a n s emergence can be compared to t h e i n i t i a l emergences o f C. a n t h r a c i n u s and mid June.  I n Westwick L. t h e l a r g e C. t e n t a n s  n. sp. i n emergence  l a s t i n g from May 19 t o June 13 ( F i g u r e 23) and t h e s m a l l J u l y peak a r e t h e o n l y emergences o f t h e t h r e e s p e c i e s i n t h e l a k e . S i m i l a r i n s t a n c e s can be seen i n F i g u r e 28. T a b l e X I I shows t h a t when l a r v a l numbers o f C. t e n t a n s a r e h i g h , t h e emergence times o f C. a n t h r a c i n u s tend t o o c c u r l a t e r i n t h e summer (.566).  S i m i l a r l y , when t h e num-  b e r s o f C. a n t h r a c i n u s a r e h i g h , C. t e n t a n s emerges (.597).  later  FIGURE 23  L a r v a l abundance and a d u l t emergence of Chironomus t e n t a n s F a b r i c i u s i n L. J a c k s o n , Westwick L. and Sorenson L.  A.  F o u r t h i n s t a r numbers per meter a t w e e k l y  B.  intervals.  A d u l t emergence:  numbers per  meter taken e v e r y f o u r t h C.  square  square  day.  The percentage o f t h e t o t a l  larval  c h i r o n o m i d p o p u l a t i o n r e p r e s e n t e d by C. t e n t a n s . l a r v a e .  L. JACKSON  WESTWICK L.  SORENSON L.  FIGURE 24  L a r v a l abundance and a d u l t emergence of Chironomus t e n t a n s F a b r i c i u s i n Rock L., B a r k l e y L. and E a s t L.  A. F o u r t h i n s t a r numbers p e r square meter a t w e e k l y B. A d u l t emergence:  intervals. numbers per square  meter taken every f o u r t h day. C.  The percentage  o f the t o t a l  larval  chironomid population represented by C. t e n t a n s l a r v a e .  Larval Composition ( % )  No. emerging per sq. m  No. larvae per sq.m _  TABLE V  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g the r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and the amount of emergence o f c e r t a i n  species,  r = 0.514 i s s i g n i f i c a n t a t p=.05; r = 0.641 a t p=.01.  ConductT.D.S. ivity  Na  Mg  CO,  HCO.  SO,  p  „  % organic carbon  Procladius bellus  .302  -.292  -.247  ,388  -.193  -.345  ,291  .074  -.937  -.126  P r o c l a d i u s freemani  .179  .154  .171  .019  .022  .184  .222  .156  .221  -.094  Procladius dentus  ,652  .640  .629  .073  .491  .598  ,642  .156  .346  -.086  P r o c l a d i u s clavus  ,910  .904  .930  .288  .858  .903  .472  .257  .415  -.200  Cricotopus  flavibasis  .190  -.196  -.163  .239  -.173  -.136  .252  .019  -.101  -.139  Cricotopus  albanus  ,362  -.351  -.302  .423  -.224  -.386  .375  .171  -.900  -.169  Psectrocladius barbimanus  ,272  .230  .275  .164  .104  .381  .092  .060  .201  -.016  Cryptotendipes a r i e l  .465  :447  .473  -.171  .293  .449  .199  .151  .275  -.079  Calopsectra  .219  .199  .173  .289  .024  .167  .473  .020  ,169  .099  ,318  -.308  -.258  -.432  -.207  .345  -.325  .091  ,938  -.210  gracilenta  Ablabesmyia peleensis  TABLE VI  The c o r r e l a t i o n between emergence histogram dispersion factors.  Non p a r a m e t r i c  Significance with p and p  and e n v i r o n m e n t a l  0.01  **.  statistics.  0.05 i s marked *  CONDUCTIVITY  SPECIES  INDEX OF DIVERSITY  Derotanypus a l a s k e n s i s  -0. 310  -0. 134  E i n f e l d i a pagana  -0. 314  -0. 253  Chironomus  -0. 365  -0. 005  0. 423  -0. 603  Chironomus a n t h r a c i n u s  -0. 397  0. 075  Glyptotendipes  -0. 559  tentans  Chironomus n.sp.  barbipes  *  0. 024  0. 213  0. 021  bellus  -0. 390  0. 009  clavus  0 747  0. 267  P r o c l a d i u s dentus  0 619  0. 121  Calopsectra  0. 777  Procladius  freemani  Procladius Procladius  gracilenta  0 838  P s e c t r o c l a d i u s barbimanus  +0. 206  **  -0. 441  Ablabesmyia p e l e e n s i s  -0 .439  -0. 220  Cricotopus  flavibasis  -0 185  0. 248  Cricotopus  albanus  -  Cryptotendipes  ariel  .403  -0. 046  0 .914  -0. 025  *  TABLE V I I  Summary o f c o r r e l a t i o n  coefficients  describing relationships  between  e n v i r o n m e n t a l f a c t o r s and s p e c i e s abundance. a t p=.05;  r=0.514 i s s i g n i f i c a n t 0.641 a t .01.  T.D.S.  C03 HC0  so  3  4  °2 PH  X  0 CO  00 U u eg 00  a a  CO  I*  CU  w 0 >  cn •H cn  rt  O •t-l CQ  •r  2  Of (3,  « c  rt 61  • led W D  cn C  «  4-1 ,c  .ID  0.  cn  t J  u  tile  .O C»| 1  >H K3  ,1-1 • O S o l c M l cutu  .991 1.000  1.000 -.220 1.000  .940  .949  .955  .972  .962  .981 -.226  .933 1.000  .706  .723  .632  .555  .586  .548 1.000  .289  .316  .305 -.133  .261  .220  .309 1.000  .537  .531  .485  .412  .537  .483  -.237 -.279 -.251  .358  .497 -.274 -.260  .085 1.000  .034 -.649  .087 1.000  .048 -.399 -.202 -.189 -.362 -.163  .332 1.000  Biomass  .227 -.202 -.223 -.032 -.147 -.221 -.127 -.074  .091  T o t a l No. Chironomids  .329 -.306 -.332  .095 -.244 -.286 -.188 -.109  .133 -.112 -.486  Derotanypus alaskensis  .077 -.095 -.102  .126 -.175 -.005 -.122 -.159  .133  Einfeldia  .489 -.471 -.481 -.022 -.431 -.447 -.347  pagana  cn cn  .998 1.000  7. Organic Carbon -.186 -.203 -.246 Index o f Diversity  cn 0 u  u 1 •H  en  2  -.075 -.064 -.190  Mg  <n 0 (J  1.000  .993  Na  T.D.S.  Conduc tivity Conductivity  0•  Tl C c 0 cttXl  .005 -.433 1.000 .783 1.000  .062  .354  .309 1.000  .036 -.037 -.102 -.383  .871  .823  .134  .362 1.000  Chironomus tentans  .260 -.272 -.309  Chironomus n.sp.  .708  .563  .318  .315 -.407 -.656  .122  .066 -.161 -.134 -.162 1.000  Chironomus anthracinus  .291 -.284 -.258 -.252 -.215 -.242 •.316  .053  .061 -.192  .080  .506  .316  .035  .541 -.143 -.020 1.000  Glyptotendipes barbipes  .386 -.371 -.374 -.098 •,350 -.337 •.288  .119 -.037 -.192 -.331  .787  .785  .356  .808 -.092 -.092  Procladius Call species)  .689  .671  .709 -.340  .598  .739  .304  .235  .031 -.191  Cryptochironomus psittacinus  .378  .336  .371 -.070  .172  .395  .112 -.002  Remainder o f species  .213  .182  .204 -.041  .010  .219  .250  .740  .417 -.251 -.264 -.083 -.578  .717 -.096  .863  .681  .051  .547  .310 -.219 .208  .291  .058 -.102 -.117  .125 -.107 -.073  .045  .442 -.374 -.506 .574  .287 -.036.1.000  .208 -.091 -.365  .291 1.000  .305 -.066 -.185 1.000  .328 -.463 -.107 -.251 -.262 -.364  .458 1.000  .392 -.418 -.005 -.283 -.269 -.230 -.210 -.216 -.428  .455 1.000  ^  TABLE V I I I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and s p e c i e s per c e n t c o m p o s i t i o n .  r=0.514 i s  s i g n i f i c a n t a t p=.05;  r=0.641  a t p=.01.  3 o 3" w HH • O 3 R  2 W  LO  Ln  •p-  rt  o a  3" 3 Ha >-< m o 3 Ul o 3  ro  3  Q> M> 11 3 1t->  a.  c  wa 1 o rt ?r til 3 3 01  B> 01  ro H01  tn  g 2  ON  Conductivity  M  00  *o  H*  T.D.S.  ro  Na  LO  O  Mg  •P-  CO,  •pON  .p-  HC0-, SO,  .p•p-  pH  •P-  % Organc C.  00  ON  Index of Diversity  r—•  Biomass T o t a l no. chironomids  o ro 03  .p-  ro  LO  VO VD  00  I-* 1  oo •p-  1  1  1  ON  ON  ON  o  LO LO  Ln  ro •P-  VO  i  ro J>  ro •pLn  1  VO  LO Ln  *o  o  ro  o  . 4>  1  ro  ro ro  •P•P-  i  ON  Ul  VO  ON  i  «o •p00  M  oo  00  NO  00  00  CO  o o o  O  ro  .p-  LO  ro  Lo  ON  •  1  I-1  ro vo  O  o o o  O O  00 LO  ON  1  >-•  o  M  ON  LO  O  Co h-  1  to 4> vo  O O  o  CO •p-  1 ON  I  * J  ro  1  00  1  .  VO  LO LO  ro  1  •PLn  t—'  1  VO  00  1  1  ro  LO  •P- .  ^1  1  i>  Ln  o  O  o o o  Derotanypus alaskensis Einfeldia Parana Chironomus Chironomus n. sp.  o  Chironomus anthracinus  O  Clyptotendipes  O  O O  fr-*E-  barbipes Procladius ( a l l species)  O  Cr yptoch ironomus PKittacxnus  Remainder of species  6L  TABLE IX  Summary of c o r r e l a t i o n  coefficients  d e s c r i b i n g t h e r e l a t i o n s h i p between e n v i r o n m e n t a l f a c t o r s and t h e amount of emergence. r=0.514 i s s i g n i f i c a n t a t p=.05;  r=0.641 a t p=.01.  o  3* HM O 3 Q  2 CO  LO  M  LO  >->  3 tn X)  q  o 3 Q  cco  rt n> 3 rr (U 3  O 3"  0 3 CO Q C  rj P w Co 3  p3 t-n ro  ft) a P>  Conductivity  N>  T.D.S.  Na  Mg  CO,  HCO,  SO,  pH  o \D  O Ln h-*  r— O O  Ln Ln Lo  1  1  Co to 00.  O LO ro  o  a*  1  ro  4>  tIO LO 1  »-»  o r—  1  J> LO a*  o o o  % Organic Carbon Derotanypus alaskensis  Einfeldia pagana  Chironomus tentans  Chironomus n. sp. Chironomus anthracinus  Clyptotcndlpes barbipes  08  TABLE X  Summary o f t h e c o r r e l a t i o n c o e f f i c i e n t s describing  t h e r e l a t i o n s h i p between  e n v i r o n m e n t a l f a c t o r s and the number o f emergence peaks f o r v a r i o u s  species.  r=0.514 i s s i g n i f i c a n t a t p=.05; r=0.641 a t p=.01.  o  rr p-  H 0 :i o  3  c  cn  3  rt  tn H-  »  o  rr  O  fT <i 0» o  o  w o  3  to  o  Hi ;o  PI H*  3  cx  i  «  Conductivity  T.D.S.  1  * OJ  o  cr.  . .  OJ  *-j  Ln ON  1  1  a*  OJ  h-»  i o> ro VO  1 OJ  Cn l-»  i  *  1  cr. Cn  to to  CO ON  OJ  Ui ro  OJ  o  Na  O  H  Mg  ro CO  to to  1  r -« Oo cr>  i O Co CO  o  t  1  r  1  H»  OJ  OJ  O  CO  vo IO  o  o  Ln  . O  1  yo  o  1  i  o Cn ON  o  O  O  S0  I OJ  h-* J>  4> ON  4  .1  to  J>  o to to  to Ui CO  Io> H  o Cn Cn  to *-* o  1  1  o 00  o o  3  HCOq  J>  OJ  yD Cn  to  CO  (  C0  o  o  . . . cr>  1  -PJ>  1  to  OJ  CT. ON  .  1  Cn  PH  % Organic Carbon Derotanypus alaskensis  Einfeldia pagana  o o  00  o o o  o o o  Chironomus tentans  Chironomus n. sp.  Chironomus anthracinus  c i y p t o t endlpes  barbipes  18  TABLE X I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s describing  t h e r e l a t i o n s h i p between  e n v i r o n m e n t a l f a c t o r s and the times of major emergence i n s e v e r a l  species.  r=0.514 i s s i g n i f i c a n t a t p=.05; r=0.641 a t p=.01.  3  H« <~t O  w H' a H  I w  o 3 o g c CO  rt rD 3 rr l» 3 (A  o  rr H* H 0 3  O  CO  O m  » P 3 to  3  dia  o  Ln  o  Conductivity  T.D.S.  Na  Mg  CO,  o •p.p-  t-< 1  LO 00  h-»  o  •p-pro i  i  ro  o  o  1  o  ON  CO Ln  1  ro 00  ro  . M O  .  vO VO  ON  CO  o  t-  LO  Ln  .  o  .  L0  •p-  Ln  1  ro ON  H»  r-  1  VO VO  Lo  r* o o  (O Ln  ro  vo  HCOo  CO  SO,  cr*  i—  1  Ln  LO CO  PH  ro  % Organic Carbon  ro  I  o  Ln  • LO VO Ov  O Ln  •P-  ro o vo  Lo O  H»  O  Ln  ro  VO  1  ro t o  to  O  tLO  1  o o  .•  ro  vo  t~>  vo  LO LO  H» ro VO ON  CTN O  ON  vo I-  O O O  Derotanypus alaskensis  1  00  ro vO  Ln ON VO  •Pt-  1  VO Ln  h-> -P•P- vO  Ln Ln  4> LO Ln  I-" LO 00 ON  ro Co  ro  O O  O  o o  O O  o  Einfeldia pagana Chironomus tentans  Chironomus n. sp.  o  Chironomus anthracinus  Glyptotendipes barbipe"s  Z2  TABLE X I I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between l a r v a l abundance, numbers o f emergi n g a d u l t s , number o f emergence peaks and emergence time,  r=0.514  i s s i g n i f i c a n t a t p=.05;  r=0.641 a t  p=.01.  M> c u rt n)  < u cd > u • Itl  O.r-1  CO .  D. alaskensis no.emerging E. pagana no.emerging C. tentans no. emerging Cn. sp. no.emerging C.anthracinus no. emerging G.barbipes no.emerging T). alaskensis no.peaks E•pagana ' no.peaks C. tentans no.peaks Cn. sp. no.peaks C•anthracinus no. peaks G.barbipes no. peaTTs D. alaskensis emergence time E. pagana emergence time C.tentans emergence time C.n.sp. emergence time C.anthracinus emergence time G.barbi pes emergence time  a|co  w|oJc  1  c d  ol  ol id c  • no  a e< u  •H  0. CO  QN  wlajc  o|u  .294  .180  -.217  -.152  .355  .088  .536  -.163  -.005  .785  .360  -.079  -.194  .536  -.166  .154  -.205  -.215  -.191  -.227  .411  -.144  -.146  .165  .235  .064  .041  .052  .105  .164  .668  -.133  -.074  .790  .488  .377  .232  -.074  -.363  .029  .123  .660  .165  .364  .228  .243  .188  -.087  .722  .022  -.022  .336  .678  .203  .401  .000  .073  .058  .508  -.017  .007  .586  -.125  .492  -.085  .095  .558  .898  .250  .171  .417  -.001  .401  .347  .183  .226  .501  .001  .177  .088  .182  .092  .226  -.089  .158  .496  -.208  .022  -.090  .021  .032  .060  .281  .321  .016  .172  .537  .508  -.345  .246  .407  .036  .328  .318  .115  .287  .339  .526  .320  .259  -.424  .179  .278  .409  .198  .185  .108  .357  .267  .704  .148  .003  .259  .432  .363  .064  .591  .284  .196  .246  .470  .116  .314  .179  .188  .248  .308  .087  .763  .245  .508  .492  .803  .082  .384  .241  -.123  .597  .210  .254  .816  .615  .203 • .322  .799  .010  .368  .832  .214  .063  .424  -.054  .425  .178  .339  .457  .419  .135  .465  .070  .395  .209  .505  .046  .510  .298  .887  .445  .306  .131  .284  .566  -.191  .161  -.025  .096  .214  .024  .119  .442  .113  .472  .307  .201  .246  .873  .739  .160  .653  .368  -.332  .309  .578  .058  .381  .355  .133  .265  .406  .159  .749  .405  .459  .490  .926  .170  OO  u>  TABLE X I I I  The  d e v e l o p m e n t a l r a t e s of C.  i n various  lakes.  tentans  LAKE  Date on w h i c h 10°C was f i r s t reached  First emergence begins  Accumulated day degrees between 10°C and 1 s t emergence  Second emergence begins  Accumulated day degrees between f i r s t and second emergence  Westwick  29 A p r i l  19 May  249.75  27 J u l y  1378.75  Sorenson  29 A p r i l  21 May  266.0  19 J u l y  822.25  Jackson  30 A p r i l  -  -  3 July  2035.50  7 July  648.25  Rock  1 May  2 June  441.25  Barkley  1 May  -  -  19 J u l y  1410.0  East  3 May  -  -  21 J u l y  1296.0  85 5.  The Chironomid Complex and t h e Lake S e r i e s  In order t o c h a r a c t e r i z e the chironomid  complex i n  the s a l i n e l a k e s e r i e s and t o c l a r i f y t h e r e l a t i o n s h i p between C. t e n t a n s and o t h e r s p e c i e s , i t i s u s e f u l t o describe the chironomid according  a s s o c i a t i o n s and group t h e l a k e s  t o the dominant s p e c i e s p r e s e n t .  T a b l e X I V i t i s seen t h a t t h e c h i r o n o m i d  Referring to  a s s o c i a t i o n s can  be d i v i d e d i n t o t h r e e main groups : a)  The C r i c o t o p u s  albanus - P r o c l a d i u s b e l l u s -  Ablabesmyia p e l e e n s i s a s s o c i a t i o n I n t h e l a k e s s t u d i e d t h i s community i s r e s t r i c t e d t o Box  27 where low s a l i n i t y  (mean c o n d u c t i v i t y 40 umho/cm  and a T.D.S. l e v e l o f 15 t o 20 ppm) and low pH (6.4) a r e e s p e c i a l l y evident. bicarbonate  The f l o r a i n t h i s magnesium c a r b o n a t e -  l a k e i s dominated by emergent p l a n t s , n o t a b l y  Potamogeton n a t a n s ( P l a t e 1 ) .  I t has a v a r i e d fauna w i t h  a r e l a t i v e l y high index of d i v e r s i t y  (2.14) ( F i g u r e 2 5 ) .  Although there i s a high d i v e r s i t y , the density of larvae i s the lowest  i n the e n t i r e lake s e r i e s .  fauna i s v e r y d i s t i n c t i v e . found: and  The  chironomid  Only t h r e e emerging s p e c i e s a r e  P r o c l a d i u s b e l l u s ( 6 4 % ) , A b l a b e s m y i a p e l e e n s i s (14%)  Cricotopus  albanus (22%).  The C r i c o t o p u s  albanus l a r v a e  mine i n Potamogeton l e a v e s .  P. b e l l u s and A. p e l e e n s i s a r e  both f r e e - l i v i n g tanypodine  predators.  86 b)  The G l y p t o t e n d i p e s b a r b i p e s - E i n f e l d i a pagana  association These two s p e c i e s dominate t h e l a k e s h a v i n g mean c o n d u c t i v i t y measures r a n i n g from 488 (East L.) t o 2766 (L. J a c k s o n ) jumho/cm (Table I ) . Derotanypus a l a s k e n s i s .  The main p r e d a t o r i s  There i s c o n s i d e r a b l e v a r i e t y i n  the s p e c i e s c o m p o s i t i o n o f the w a t e r b o d i e s i n v o l v e d . F o r example, i n Near P h a l a r o p e , mud d w e l l i n g c h i r o n o m i d s  l a r g e d e n s i t i e s o f non p r e d a t o r y ,  are lacking.  The dominant s p e c i e s ,  P s e c t r o c l a d i u s barbimanus, i n h a b i t s a q u a t i c v e g e t a t i o n . Phalarope  Near  a l s o contains the l a r g e s t c o n c e n t r a t i o n of the  p r e d a t o r Tanypus sp. found i n t h e l a k e s .  The s p e c i e s i s  known o n l y from l a r v a e i n bottom samples (Table I V ) ; whether or n o t i t i s Tanypus p u n c t i p e n n i s s i n c e no a d u l t s were t r a p p e d h e r e . Phalarope  (Table I I ) i s n o t known, N e v e r t h e l e s s , Near  i s i n c l u d e d as a l a k e i n t h i s s e c t i o n because o f  i t s s i m i l a r i t i e s to the other lakes i n v o l v e d . The  group can be d i v i d e d i n t o t h r e e subgroups depending  on t h e abundance o f s p e c i e s secondary t o G. b a r b i p e s and E. pagana i n t h e f o l l o w i n g manner: (i)  C r i c o t o p u s - Chironomus a n t h r a c i n u s s u b d i v i s i o n c o n t a i n s s p e c i e s prominent i n t h r e e l a k e s (East L., B a r k l e y L., Box 17) h a v i n g  con-  d u c t i v i t i e s r a n g i n g from 488 t o 741 umho/cm and T.D.S. c o n c e n t r a t i o n s o f 372 t o 571 mg/1.  The  O r t h o c l a d i i n a e , e s p e c i a l l y t h e genus C r i c o t o p u s  87 are important.  As w e l l as b e i n g t y p i c a l o f t h e  p r o f u n d a l s o f o l i g o t r o p h i c l a k e s ( B r u n d i n , 1951) the O r t h o c l a d i i n a e a r e o f t e n dominant i n t h e l i t t o r a l s o f e u t r o p h i c w a t e r s (Sandberg, 1969). j  The  genus Chironomus, r e p r e s e n t e d e s p e c i a l l y by  C. a n t h r a c i n u s , makes an appearance.  T h i s sub-  d i v i s i o n may be c o n s i d e r e d a t r a n s i t i o n between the u n i q u e f r e s h w a t e r s p e c i e s o f Box 27 and t h e large middle  s a l i n i t y a s s o c i a t i o n dominated by  G. b a r b i p e s and E. pagana. The  Chironomus t e n t a n s s u b d i v i s i o n i n c l u d e s s p e c i e s  c h a r a c t e r i s t i c o f c o n d u c t i v i t i e s f r o m 810 t o 1500 umho/cm (Near O p p o s i t e  Crescent  to RockL.).  It  r e a c h e s i t s most d i s t i n c t i v e form i n Westwick and Sorenson L a k e s (1200 t o 1500 umho/cm) whose most i m p o r t a n t f e a t u r e s a r e h i g h l e v e l s o f o r g a n i c carbon,low oxygen t e n s i o n s , N a j a s beds i n deep mud, S c i r p u s a t t h e m a r g i n s and l a r g e mats o f S p i r o g y r a . A t 1.0 meter t h e c h a r a c t e r i s t i c c h i r o n o m i d i s C. t e n t a n s .  Chironomus n. sp. i s c h a r a c t e r i s t i c o f t h e most s a l i n e l a k e s dominated by G. b a r b i p e s and E. pagana - Lakes G r e e r and J a c k s o n w i t h an upper l i m i t o f 2766 umho/cm c o n d u c t i v i t y and 2.5°/oo s a l i n i t y . Large blue-green  a l g a l blooms (Aphanozomenon)  a r e common from June t o September.  88 The major predaceous c h i r o n o m i d  i s the large  Derotanypus a l a s k e n s i s w h i c h r e a c h e s i t s g r e a t e s t d e n s i t y i n the higher s a l i n i t i e s . t i o n concerning  The most i n t e r e s t i n g  t h e G. b a r b i p e s  observa-  - E. pagana a s s o c i a t i o n  i s t h e f a c t t h a t t h e t h r e e s p e c i e s o f Chironomus a r e found i n a l l t e n l a k e s , b u t a t 1.0 meter each i s most abundant i n a p a r t i c u l a r group o f l a k e s .  Thus  C. a n t h r a c i n u s r e a c h e s g r e a t e r p r o p o r t i o n s i n t h e f r e s h e r l a k e s , C. t e n t a n s i n t h e medium s a l i n i t i e s and C. n.sp. i n t h e most s a l i n e l a k e s dominated by G. b a r b i p e s and E. pagana.  c)  The C a l o p s e c t r a g r a c i l e n t a - C r y p t o t e n d i p e s  ariel  association Above a c o n d u c t i v i t y o f 4000 jumho/cm and a T.D.S. c o n c e n t r a t i o n o f 3000 mg/1 an e n t i r e l y new s p e c i e s composit i o n appears.  T h i s group o f s p e c i e s i s a s s o c i a t e d w i t h  c o n d u c t i v i t i e s up t o 1200 umho/cm and mean pH readings from 8.9 t o 9.3 ( B o i t a n o L., L. L y e , Round-up L. and Barnes L . ) . C a l o p s e c t r a g r a c i l e n t a i s one o f t h e dominant s p e c i e s o f the above t h r e e l e s s s a l i n e l a k e s . by C r y p t o t e n d i p e s Chironomus n.sp. chironomid  I t tends t o be r e p l a c e d  a r i e l as t h e s a l i n i t y i n c r e a s e s . i s t h e major component o f t h e Barnes L.  fauna (46%) and makes up 16 p e r c e n t o f t h e  emerging B o i t a n o L. fauna.  I t i s n o t abundant i n Round-up  L. o r L. L y e . Derotanypus a l a s k e n s i s i s most abundant i n L. L y e , b u t i s l a r g e l y r e p l a c e d by P r o c l a d i u s c l a v u s as the  main predaceous c h i r o n o m i d  i n the high s a l i n i t i e s of  Round-up and Barnes Lakes. The biomass f i g u r e s f o r t h i s a s s o c i a t i o n o f s p e c i e s w i t h a h i g h t o l e r a n c e o f s a l i n e w a t e r s a r e r e l a t i v e l y low Although  t h e r e a r e numerous s p e c i e s and l a r g e numbers o f  some s p e c i e s p r e s e n t , the l a r v a e o f these forms a r e s m a l l The i n d i c e s o f d i v e r s i t y f o r Round-up L., L. Lye and e s p e c i a l l y B o i t a n o L. (2.74) a r e h i g h .  Barnes L. has the  lowest index of a l l the l a k e s (0.90); c e r t a i n l y t i o n of the l a k e ' s h i g h s a l i n i t y .  a reflec-  The biomass i s about  16 times t h a t o f Round-up L. p r i n c i p a l l y because o f the presence o f l a r g e numbers o f Chironomus n. sp. w h i c h reaches a considerable  size.  TABLE XIV  The  percentage composition  of  species  i n the l a k e s based on the t o t a l a d u l t emergence May  - August  1970.  90 Barnes  Chironomus n.sp. Procladius clavus Cryptotendipes ariel P r o c l a d i u s dentus Others  46 30 17 4 3  Cryptotendipes a r i e l Calopsectra gracilenta Psectrocladius barbimanus Procladius clavus Others  L.  B o i t a n o L. Calopsectra gracilenta Chironomus n.sp. Procladius freemani Derotanypus alaskensis Others  71 16 4 2 7 -  Rock L. E i n f e l d i a pagana Glyptotendipes barbipes Derotanypus alaskensis P r o c l a d i u s .fr.eemani Others  Sorenson  L.  Round-up L.  L.  37 31 15 7 10  L.  Glyptotendipes barbipes Chironomus t e n t a n s E i n f e l d i a pagana PsectrocTadiiis barbimanus Others  36 18 18 18 10  47 24 6 10 13  Jackson  E i n f e l d i a pagana Glyptotendipes barbipes Derotanypus alaskensis Chironomus n.sp. Others  Psectrocladius barbimanus Calopsectra gracilenta Derotanypus a l a s k e n s i s Procladius clavus Others  L. 35 29 9 16 11  Lye  :  32 28 25 9 6  Greer  Glyptotendipes barbipes Derotanypus a l a s k e n s i s E i n f e l d i a pagana Chironomus n.sp. . Others  Near P h a l a r o p e  Westwick L.  Psectrocladius barbimanus 65 Cricotopus f l a v i b a s i s 18 Glyptotendipes barbipes 8 Derotanypus a l a s k e n s i s 5 Others 4  E i n f e l d i a pagana Chironomus t e n t a n s Glyptotendipes barbipes Psectrocladius barbimanus Others  Near Opposite Crescent  Box  Glyptotendipes barbipes 65 E i n f e l d i a pagana 31 Procladius bellus 1 Per o tanypu s~~ala s kens i s 1 Others 2  Glyptotendipes barbipes E i n f e l d i a pagana Chironomus a n t h r a c i n u s Cricotopus albanus Others  E a s t L.  Box  '22 22 20 16 20  73 19 4 2 2  17 29 23 20 14 14  f Barkley  L.  Glyptotendipes barbipes E i n f e l d i a pagana Psectrocladius barbimanus Cricotopus flavibasis Others  21 21 12 12 34  Glyptotendipes barbipes E i n f e l d i a pagana Derotanypus a l a s k e n s i s Cricotopus f l a v i b a s i s Others  29 25 23 11 12  27  Procladius bellus Cricotopus albanus Ablabesmyia p e l e e n s i s  64 22 14  91 C.  DISCUSSION  1.  The Chironomidae  and the Lake S e r i e s  I t has l o n g been known t h a t the a q u a t i c d i p t e r a (the Chironomidae  i n p a r t i c u l a r ) r e p r e s e n t one o f the most  d i v e r s e and a d a p t a b l e f r e s h w a t e r groups.  Suworow (1908)  found a s p e c i e s o f Chironomus i n Lake B u l a c k on the K i r g i z Steppe i n s a l i n i t i e s of 285 °/oo, o f the sea.  e i g h t times the  salinity  Chironomus plumosus i s known to l i v e i n n a t u r e  a t a pH of 2.3  (Harp and Campbell, 1967).  Such v e r s a t i l i t y  makes c h i r o n o m i d s i d e a l organisms w i t h w h i c h to study the e f f e c t s of v a r i a b l e c h e m i c a l c o n d i t i o n s on an assemblage o f related species. O b v i o u s l y , the c h i r o n o m i d s i n the l a k e s e r i e s a r e adapted t o t h e i r t o t a l environment.  But what a r e the main  f a c t o r s d e t e r m i n i n g the g e n e r a l d i s t r i b u t i o n p a t t e r n s described?  I n the p a s t , c h i r o n o m i d d i s t r i b u t i o n d a t a has  l a r g e l y come from s t u d i e s on the c l a s s i f i c a t i o n o f the l a k e t y p e s u s i n g the dominant p r o f u n d a l c h i r o n o m i d fauna p r e s e n t ( B r u n d i n , 1949,  1951).  An e x a m i n a t i o n of t h i s i n f o r m a t i o n  i n the c o n t e x t o f the p r e s e n t r e s e a r c h may  lead to a better  u n d e r s t a n d i n g of the f a c t o r s i n f l u e n c i n g c h i r o n o m i d d i s t r i b u t i o n i n the l a k e s . The c l a s s i f i c a t i o n of l a k e t r o p h i c types was  first  i n t r o d u c e d by Thienemann (1920) and f u r t h e r developed i n works by Lenz (1925), Lundbeck (1926) and Humphries (1936)  f o r most o f c e n t r a l and n o r t h e r n Europe.  B r u n d i n (1958)  s t u d i e d t h i s c o n c e p t on a g r e a t e r s c a l e and found t h a t the c l a s s i f i c a t i o n , w i t h r e g i o n a l v a r i a n t s i n s p e c i e s , was v a l i d t h e w o r l d over.  T h i s c l a s s i f i c a t i o n may be g e n e r a l -  i z e d i n the f o l l o w i n g manner.  Oligotrophic lakes are  u s u a l l y dominated by s p e c i e s o f t h e s u b f a m i l y These a r e s m a l l forms l a c k i n g hemoglobin. more p r o d u c t i v e  Orthocladiinae  Lakes becoming  (moderately o l i g o t r o p h i c ) a r e more and more  dominated by a T a n y t a r s u s f a u n a , m e s o t r o p h i c l a k e s  contain  p r o p o r t i o n a l l y l a r g e r profundal populations of the Chironomini  ( e s p e c i a l l y those w i t h o u t v e n t r a l t u b u l e s ) , w h i l  the p r o f u n d a l s  of eutrophic lakes contain mainly  l a r g e , hemo  g l o b i n - b e a r i n g Chironomus s p e c i e s .  These l a r g e l a r v a e have  v e n t r a l t u b u l e s and a r e r e p r e s e n t e d  by forms such as  C. a n t h r a c i n u s  and i n the most e u t r o p h i c a r e a s , C. plumosus  ( B r u n d i n , 1958).  Deevy (1942), Goulden (1964) and S t a h l  (1969) n o t e t h a t i n s t r a t i f i e d l a k e d e p o s i t s t h e f o s s i l c h i r o n o m i d s o f t e n show a s u c c e s s i o n from T a n y t a r s u s t h r o u g h t o Chironomus, c o r r e l a t e d w i t h t h e l a k e ' s e v o l u t i o n a r y sequence from o l i g o t r o p h y t o eutrophy. I n one o f h i s e a r l i e s t papers on t h e s u b j e c t , B r u n d i n (1949) n o t e d t h a t t h e a s s o c i a t i o n o f c h i r o n o m i d s and t r o p h i c l a k e type i s n o t d i r e c t , b u t i s more a f u n c t i o n o f t h e a n n u a l minimum oxygen c o n c e n t r a t i o n t h a t can be w i t h s t o o d by t h e l a r v a e . withstanding Harnish,  S i n c e hemoglobin i s known t o a i d l a r v a e i n  low oxygen c o n d i t i o n s (Walshe, 1947 A,B, 1950;  1960), t h e more hemoglobin p r e s e n t  and the l a r g e r  the s i z e o f the l a r v a , t h e l e s s d i f f i c u l t y t h e r e i s i n o v e r -  93  coming t h e m i c r o s t r a t i f i c a t i o n o f r e d u c i n g c o n d i t i o n s on t h e s u r f a c e o f t h e sediment ( B r u n d i n , 1951). The s u p p l y o f oxygen t o t h e bottom o f t h e l a k e i s a f f e c t e d by t h e volume o f the h y p o l i m n i o n and t h e d u r a t i o n of s t r a t i f i c a t i o n as w e l l as t h e amount o f decomposable organic matter i n the hypolimnion.  There i s no r i g i d connec-  t i o n between oxygen d e f i c i t and l a k e p r o d u c t i v i t y s i n c e l a k e morphometry, among o t h e r t h i n g s , c o m p l i c a t e s However, as Mundie  the s i t u a t i o n .  (1957) e x p l a i n s , " I t so happens t h a t i n  v e r y many l a k e s eutrophy i s a s s o c i a t e d w i t h a h i g h oxygen c o n c e n t r a t i o n d e f i c i t and o l i g o t r o p h y w i t h a low d e f i c i t , so t h a t a c o r r e l a t i o n between l a k e type and c h i r o n o m i d emerges".  type  A s a l i n e l a k e s e r i e s , however, has n e v e r b e f o r e  been s t u d i e d i n t h i s  context.  The s i m i l a r morphometry and t h e l a c k o f t h e r m o c l i n e formation hypolimnic  i n t h e l a k e s under study  (or a t l e a s t the l a c k of  e f f e c t on t h e depth zone under  consideration)  r e s u l t i n comparable oxygen c o n c e n t r a t i o n s lake series.  throughtout the  As oxygen w o u l d seem t o have l i t t l e  influence  on o v e r a l l d i s t r i b u t i o n p a t t e r n s , an e x a m i n a t i o n o f p r o d u c t i v i t y t r e n d s c o u l d be i n s t r u c t i v e . I t m i g h t be e x p e c t e d t h a t o r g a n i c carbon w o u l d be a s u i t a b l e measure o f g e n e r a l p r o d u c t i v i t y , w i t h oxygen l e v e l s decreasing  i n a r e a s o f abundance much i n t h e way oxygen  d e f i c i t s appear i n h i g h l y e u t r o p h i c w a t e r s .  Although  organic  94 c a r b o n and oxygen l e v e l s show an i n v e r s e r e l a t i o n s h i p ( F i g u r e 26) ( t h e c o r r e l a t i o n i s -.649, p < . 0 1 ) , t h e r e i s no i n d i c a t i o n t h a t these parameters f o l l o w the g e n e r a l trend of i n c r e a s i n g p r o d u c t i v 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 (Rawson and Moore, 1944). i n Westwick  A h i g h abundance o f  chironomids  and Sorenson L a k e s m i g h t be expected,  since  the o r g a n i c carbon l e v e l s peak t h e r e , but t h e l a r v a l dens i t y i s q u i t e low.  And i n t h i s case the low numbers a r e  due t o low d e n s i t i e s o f s p e c i e s t h a t s h o u l d be a b l e t o e a s i l y w i t h s t a n d the lower oxygen l e v e l s p r e s e n t .  No  indication  t h a t t h i s p a u c i t y was due t o i n c r e a s e d p r e d a t i o n was  found.  The p h o t o s y n t h e t i c a c t i v i t y i n the l a k e s e r i e s was n o t examined.  P r e l i m i n a r y l i g h t and d a r k b o t t l e s t u d i e s have  r e c e n t l y been i n s t i g a t e d , however, and seem t o i n d i c a t e t h a t the f r e s h and m o d e r a t e l y c o n c e n t r a t e d l a k e s d i s p l a y t h r e e t o f i v e times the p h o t o s y n t h e t i c p r o d u c t i o n o f the v e r y water bodies  (Reynolds, p e r s . comm.).  saline  The l a k e s where, the  G. b a r b i p e s - E. pagana a s s o c i a t i o n p r e v a i l s have s a l i n i t i e s r a n g i n g from 0.3 t o 2.5 °/oo.  These c o n c e n t r a t i o n s a r e n o t  so h i g h as t o a d v e r s e l y a f f e c t p r i m a r y p r o d u c t i o n and cons e q u e n t l y the l a k e s have a l a r g e p h y t o p l a n k t o n  s t o c k and i n  most cases a p e r i p h e r a l b e l t o f emergent v e g e t a t i o n .  Such  e u t r o p h i c c o n d i t i o n s a r e i d e a l f o r the l a r g e r C h i r o n o m i n i . Moreover, t h e r e i s some evidence  t h a t the f r e s h e r l a k e s a r e  l e s s p r o d u c t i v e than the m o d e r a t e l y s a l i n e ones, a c c o r d i n g t o Reynolds ( p e r s . comm.).  I n Box 27 c h i r o n o m i d s  u s u a l l y domi-  n a t i n g t h e s u b s t r a t e o f the l a k e s a r e c o n s p i c u o u s l y few,  95 w h i l e the Chironomus s p e c i e s a r e e n t i r e l y a b s e n t . probably  due  This i s  t o the l a c k of d i s s o l v e d n u t r i e n t s and a r e s u l -  t a n t low l e v e l of p h y t o p l a n k t o n .  D e t r i t u s and a l g a e a r e  main f o o d items of the l a r g e r tube d w e l l i n g  the  species.  L e l l a k (1965) and Jonasson (1954) n o t e t h a t the  production  of Chironomus s p e c i e s i s dependent on:the amount of p h y t o plankton  i n the w a t e r column.  Amounts o f d i s s o l v e d s o l i d s i n the w a t e r are o f t e n u s e d as measures o f p r o d u c t i v i t y .  I n a l a r g e r number o f  British  Columbia l a k e s N o r t h c o t e and L a r k i n (1956) found t h a t p l a n k t o n and b e n t h i c fauna i n c r e a s e d w i t h i n c r e a s i n g T.D.S., although  the c o n c e n t r a t i o n s  they c o n s i d e r e d were comparable  to o n l y the f r e s h e r l a k e s i n the p r e s e n t  study.  Rawson and  Moore (1944) examined a l a r g e number of l a k e s on  the  Saskatchewan p r a i r i e , some of w h i c h were s i m i l a r t o the i n the C a r i b o o - C h i l c o t i n a r e a .  Again, a trend of i n c r e a s i n g  abundance o f bottom fauna w i t h i n c r e a s i n g T.D.S. was up  lakes  to a c o n c e n t r a t i o n of 2250 ppm.  observed  The number of bottom  organisms 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 p a s t t h i s p o i n t . A s a l i n i t y of 2250 ppm  a p p r o x i m a t e s t h a t of L.  F i g u r e 25 shows the c h i r o n o m i d  Jackson.  l a r v a l biomass i n the  l a k e s e r i e s and r e v e a l s a s i m i l a r d e c r e a s e i n b e n t h i c above a c o n c e n t r a t i o n o f 2250 ppm. Near P h a l a r o p e , t h i s context.  The  fauna  low l e v e l s i n Rock L.,  Westwick L. and Sorenson L. a r e anomalous i n Indeed, a l i n e a r r e g r e s s i o n performed on  p o i n t s i n the graph showed the p r o b a b i l i t y o f the s l o p e  the being  FIGURE 25  Chironomid l a r v a l biomass and i n d e x of d i v e r s i t y f o r the l a r v a l a t 1.0 m i n the l a k e  series.  complexes  LARVAL BIOMASS (CM /M )  INDEX OF DIVERSITY CO  NO  b  b  o  3  o  o  o  o  o  o  2  o o  o  Barnes L. Round-up L. L. Lye Boitano L. L. Jackson L. Greer Rock L. N. Phalarope Westwick L. Sorenson L. N. Op.Cres. Box 17 Barkley L. East L. Box 27  «  FIGURE 26  Graph showing the r e l a t i o n s h i p between oxygen l e v e l s and o r g a n i c c a r b o n i n the l a k e s .  PER CENT OF ORGANIC CARBON & 0 LEVELS (MG / L) 2  rO _i  Box 27 East L. Barkley L. Box 17 N.Op. Cres. Sorenson L. Westwick L. N. Phalarope Rock L. L.Greer L.Jackson Boitano L. L. Lye Round-up L. Barnes L.  4v _i  Ol _i  o  00  i  I  -O  98 zero was  .29.  I t i s p o s s i b l e that chironomid  l a r v a l biomass  a l o n e i s a poor i n d i c a t o r of r e l a t i v e p r o d u c t i v i t y i n l a k e s and  t h a t the i n c l u s i o n of o t h e r b e n t h i c and  planktonic  organisms w o u l d a l t e r the r e l a t i v e biomass r e s u l t s . I n the l a k e s e r i e s as a w h o l e , i t w o u l d seem t h a t  the  b a s i c d i s t r i b u t i o n a l p a t t e r n i s l a r g e l y the r e s u l t of  inter-  p l a y between s a l i n i t y and p r o d u c t i v i t y .  densi-  t i e s o f l a r v a e and and  The v e r y low  the h i g h d i v e r s i t y i n Box  i n i t s chironomid  f a u n a and c h e m i s t r y  an o l i g o t r o p h i c one.  I n s a l i n i t i e s above t h a t of Box  e u t r o p h i c l a k e fauna.  i f the a r b i t r a r y f i g u r e  (1964) i s adopted, o n l y those l a k e s w i t h a  ( B o i t a n o L.)  H u t c h i n s o n (1932),  study  (1966).  the  considered  salinity  and above can be c l a s s e d as s a l i n e  e u t r o p h i c l i k e the l a k e s d e s c r i b e d by Decksbach  Williams  27  essentially a  A c t u a l l y , a l l the l a k e s  must be termed e u t r o p h i c , a l t h o u g h  o f 3 °/oo  notable,  the l a k e resembles  s p e c i e s t y p e s change m a r k e d l y and r e p r e s e n t  of W i l l i a m s  27 a r e  (1924),  Rawson and Moore (1944) and B a y l y  and  T h i s d e m a r k a t i o n a p p l i e s n i c e l y to t h i s  s i n c e the change from a c h i r o n o m i d  fauna t y p i c a l of  h i g h l y e u t r o p h i c w a t e r s to a community r a t h e r r e s t r i c t e d to o , h i g h s a l i n i t i e s o c c u r s a t t h i s 3 /oo s a l i n i t y p o i n t . The  biomass-diversity relationships i n this  are a l s o important.  Chironomid biomass i n the  transition  eutrophic,  b l u e - g r e e n a l g a e r i c h L. G r e e r and L. J a c k s o n i s h i g h , mainly  due  C^n.sp.  t o l a r g e numbers of G. b a r b i p e s , E. pagana and But because of t h i s d o m i n a t i o n the numbers of  s p e c i e s and the d i v e r s i t y a r e low.  The biomass i n the  f o u r l a k e s r e p r e s e n t i n g s a l i n i t i e s above 3 °/oo i s v e r y low w h i l e t h e d i v e r s i t i e s i n two o f these l a k e s ( B o i t a n o L . j L. L y e ) a r e h i g h e r than i n any o t h e r l a k e - perhaps due t o t h e presence  o f s p e c i e s t h a t can t o l e r a t e h i g h  s a l i n i t i e s as w e l l as moderate ones. Although  i t i s expected  that rooted plants complicate  any environment and encourage d i v e r s i t y by i n c r e a s i n g n i c h e s and s t a b i l i z i n g i n t e r a c t i o n s (Wohlschlag, 1950), the absence of r o o t e d p l a n t s i n these h i g h s a l i n i t y l a k e s does n o t seem t o have a g r e a t e f f e c t on d i v e r s i t y .  The v e r y low d i v e r s i t y i n  Barnes L. i s c e r t a i n l y a r e f l e c t i o n o f v e r y h i g h i o n i c c e n t r a t i o n s r a t h e r than t h e r e s u l t o f any reduced owing t o t h e absence o f a q u a t i c p l a n t s . i n the h i g h e r s a l i n i t i e s i s reduced.  Primary  con-  complexity production  This s i t u a t i o n , along  w i t h t h e above mentioned p r o d u c t i v i t y - d i v e r s i t y  relationship  i n L. Greer and L. J a c k s o n , r e i n f o r c e M a c A r t h u r s 1  (1965)  c o n t e n t i o n t h a t an i n c r e a s e i n p r o d u c t i v i t y i s n o t always accompanied by an i n c r e a s e i n d i v e r s i t y . i s i n c r e a s e d t h e r e i s o f t e n a decrease  Where p r o d u c t i o n  i n resource v a r i e t y  and a g r e a t e r i n e q u a l i t y o f e x i s t i n g r e s o u r c e s , t e n d i n g t o decrease  diversity.  The i n c r e a s e i n c h i r o n o m i d biomass i n Barnes L. i s due to the h i g h d e n s i t i e s o f Chironomus n.sp. w h i c h reaches a considerable size.  The low numbers o f t h i s s p e c i e s i n  Round-up L. and Lye L. a r e n o t c l e a r , b u t i t w o u l d seem t o be  100 something o t h e r than s o l u t e c o n c e n t r a t i o n .  C. n.sp.  o c c u r s i n g r e a t e s t numbers where the d i v e r s i t y i s l o w e s t ; t h i s low d i v e r s i t y does n o t seem t o be e n t i r e l y a r e s u l t of i t s owns h i g h numbers.  I n s i m i l a r s i t u a t i o n s , t h e absence  from f r e s h e r w a t e r o f a s p e c i e s adapted t o h i g h  salinities  i s n o t due t o h y p o r e g u l a t i o n d i f f i c u l t i e s , b u t i s u s u a l l y the r e s u l t o f b i o t i c i n t e r a c t i o n s l e a d i n g t o e x c l u s i o n by o t h e r s p e c i e s (Beadle, 1943; L a u e r , 1969; Scudder e t a l , 1972).  FIGURE 27  S a l i n i t y t o l e r a n c e s o f the i d e n t i f i e d s p e c i e s o f the one meter depth zone i n the l a k e  series.  Tartypus punctlpennls Derotanypus a l a s k e n s i s  —  Derotanypus n.sp. Procladius bellus Procladius nietus P r o c l a d i u s freemani  "  Procladius r u r i s  — —  —  P r o c l a d i u s dentus P r o c l a d i u s clavus  .  Procladius sublettei  ,  P r o c l a d i u s n.sp. Ablabesmyia p e l e e n s i s Nanocladius n.sp. Cricotopus albanus Cricotopus  flavibasis  Cricotopus  trifasciatus  Acricotopus  nitidellus  P s e c t r o c l a d i u s barbimanus  —;  _  -.  —  —  Psectrocladius zetterstedti P s e c t r o c l a d i u s n.sp. Chironomus anthracinus  .  Chironomus a t r e l l a  —  Chironomus tentans  .  Chironomus plumosus Chironomus n.sp.(near atritibia) Chironomus n.sp. E i n f e l d i a pagana Cryptochironomus psittacinus Cryptotendipes  ariel  Endochironomus n i g r i c a n s Glyptotendipe s barbipes  1  Polypedilum n.sp. Calopsectra gracilenta Calopsectra  holochlorus  i' 0  1  i  :  1  1  3000 '  6000  9000.  Conductivity  (umho/cm at 25°C)  1  12000  102 2.  Chironomus t e n t a n s and the Lake  Topping  Series  (1969, 1971, 1972) has c a r e f u l l y examined the  r e l a t i o n s h i p between the d i s t r i b u t i o n o f C. t e n t a n s l a r v a e and the p h y s i c a l and c h e m i c a l environment, but l i t t l e been done t o examine how  these f a c t o r s , along w i t h b i o t i c  i n t e r a c t i o n s , might a f f e c t the i n s e c t ' s l i f e a)  has  cycle.  P h y s i c a l and Chemical I n f l u e n c e s  C. t e n t a n s i n h a b i t s a s u b s t a n t i a l range of c o n d i t i o n s (Acton and Scudder, 1971).  I t has c o n s i d e r a b l e t o l e r a n c e  f o r s a l i n e w a t e r s and has been c o l l e c t e d i n the b r a c k i s h w a t e r s of the B a l t i c  (Palmen and Aho, 1966).  I n the study  a r e a i t s g r e a t e s t abundance and emergence s u c c e s s o c c u r s i n the m i d d l e o f the s a l i n i t y range, p a r t i c u l a r l y i n Westwick and Sorenson L a k e s . There i s much v a r i a t i o n i n d e v e l o p m e n t a l time among the C.tentans p o p u l a t i o n s i n h a b i t i n g the s i x l a k e s under c o n s i d e r a t i o n (Table X I I I ) .  Comparing the l e n g t h s of the  s p r i n g g e n e r a t i o n (second emergence) t h e r e i s n o t r e a l  trend,  a l t h o u g h developmental t i m e s i n Sorenson and Rock Lakes a r e s u b s t a n t i a l l y lower than the r e s t .  The r a p i d growth o f  l a r v a e i n Sorenson L. s u p p o r t s the c o n t e n t i o n t h a t t h i s i s the most f a v o r a b l e h a b i t a t f o r the s p e c i e s , b u t the s i t u a t i o n i n Rock L. i s more d i f f i c u l t t o u n d e r s t a n d .  The  brief  d e v e l o p m e n t a l time (37 days) i s c o n s i s t e n t w i t h r a t e s r e p o r t ed by S a d l e r (1935), but i s c o n s i d e r a b l y , s h o r t e r than t h a t i n  103 neighboring populations.  The postponed emergence o f  o v e r w i n t e r i n g l a r v a e c o m p l i c a t e s the s i t u a t i o n f u r t h e r , and i s p o s s i b l y a r e s u l t o f a l o n g e r w i n t e r diapause o r a m a j o r i t y o f l a r v a e o v e r w i n t e r i n g i n the t h i r d  instar.  Temperature i s u s u a l l y c o n s i d e r e d a p r i m a r y f a c t o r i n d e t e r m i n i n g developmental O l i v e r , 1969,  1971).  r a t e s ( M i l l e r , 1941; Mundie,  1957;  H i l s e n h o f f (1966) found t h a t v a r i a t i o n s  i n the development o f Chironomus plumosus i n d i f f e r e n t p a r t s o f Lake Winnebago c o u l d be a t t r i b u t e d t o w a t e r Koskinen  temperature.  (1968) a l s o r e c o r d e d s i m i l a r r e s u l t s f o r y e a r l y  v a r i a t i o n i n the emergence times o f C. s a l i n a r i u s i n n o r t h e r n Europe.  There i s no e v i d e n c e  that differences i n generation  times o f C. t e n t a n s a r e caused by e i t h e r v a r i a t i o n s i n average temperature  (Table I I ) o r d i e l temperature  range ( F i g u r e 4 ) .  C o n s i d e r a b l e work has been done on the e f f e c t o f p e r i o d on the development o f C. t e n t a n s .  photo-  Englemann and  S h a p p i r i o (1965) found t h a t diapause a t 22°C was by s h o r t day p e r i o d s ( s i x t e e n h o u r s l i g h t ) .  maintained  C l a r k (1971)  r e c o r d e d t h a t low d a y l i g h t regimes suppressed  l a r v a l devel-  opment and when such l a r v a e were s u b s e q u e n t l y  placed i n long  day l e n g t h s i t u a t i o n s , emergence success was  reduced.  Members of the same p o p u l a t i o n under i d e n t i c a l temperat u r e and l i g h t regimes may mental r a t e s .  show r a d i c a l l y d i f f e r e n t  develop-  L a r v a e h a t c h i n g from the same egg mass o f t e n  pupate two o r t h r e e weeks a p a r t  ( C o l l e n , p e r s . comm.).  Up  to  90 p e r c e n t o f f o u r t h i n s t a r s can f a i l  t o pupate and  emerge d u r i n g t h e time t h e r e s t o f t h e p o p u l a t i o n does. Numbers o f these l a r v a e w i l l emerge a l o n g w i t h t h e a d u l t s of the next generation  ( C l a r k , 1971).  S i m i l a r asynchrony  i n C. t e n t a n s p o p u l a t i o n s was e s t a b l i s h e d i n t h e e x p e r i m e n t a l pond p o p u l a t i o n s s t u d i e d by H a l l e t a l (1970) and Fagan and Enns (1966) observed  s i m i l a r effects i n populations of  G l y p t o t e n d i p e s b a r b i p e s i n sewage lagoons.  In other  insects,  d e l a y e d h a t c h i n g o f eggs has been r e p o r t e d i n t h e m a y f l y Ameletus l i n e a t u s ( G i b b s , 1971) and t h i s s p o r a d i c ,  asynchro-  nous emergence b r i n g s a l l t h e advantages t h a t a c c r u e when the development o f segments o f t h e p o p u l a t i o n i s s t a g g e r e d . These i n c l u d e t h e s u r v i v a l o f t h e p o p u l a t i o n through  periods  o f s t r e s s , t h e l e s s e n i n g o f t h e impact o f p r e d a t i o n and t h e r e d u c t i o n o f c r o w d i n g and c o m p e t i t i o n . I t must be c o n c l u d e d  t h a t s i n c e t h e r e i s l i t t l e o r no  d i f f e r e n c e i n t h e day l e n g t h changes among t h e l a k e s , t h i s f a c t o r can h a r d l y be t h e major cause o f d i f f e r e n t i a l s i n t h e developmental r a t e of the v a r i o u s populations. C. t e n t a n s i s most abundant i n h a b i t a t s a s s o c i a t e d w i t h f l o c c u l a n t muds, d e t r i t u s and stands o f S c i r p u s . c o n d i t i o n s a r e e s p e c i a l l y w e l l developed  These  i n Sorenson L. and  W e s t w i c k L. and a r e a s s o c i a t e d w i t h h i g h l e v e l s o f o r g a n i c c a r b o n (Table I ) . feeder  S i n c e C. t e n t a n s i s a d e t r i t u s and a l g a e  ( S a d l e r , 1935), Topping (1971) used o r g a n i c carbon as  a measure o f f o o d abundance i n these same l a k e s .  Anderson  105 and H i t c h c o c k (1968) and Palmen and Aho  (1966) found t h a t  the numbers o f Chironomus a t r e l l a and C. t e n t a n s r e s p e c t ively  i n c r e a s e d i n the presence  s t u d i e s on the new  of o r g a n i c m a t e r i a l .  In  V o l t a Lake P e t r (1971) a l s o n o t e d t h a t  a r e a s of h i g h o r g a n i c c o n t e n t were p o p u l a t e d most a b u n d a n t l y by Chironomus s p e c i e s .  I t i s p o s s i b l e , t h e n , t h a t the amount  of o r g a n i c carbon i n the mud food a v a i l a b i l i t y .  m i g h t be a r e a s o n a b l e measure o f  I f the g e n e r a l c o n d i t i o n s p r e s e n t i n  Sorenson L. and Westwick L. a r e a s s o c i a t e d w i t h h i g h l e v e l s of a v a i l a b l e f o o d , the c o r r e l a t i o n s between l a r v a l abundance and per c e n t c o m p o s i t i o n o f C. t e n t a n s and o r g a n i c carbon  may  be m e a n i n g f u l . In c o n t r o l l e d e x p e r i m e n t s , H a l l e t a l (1970) found developmental  time o f C. t e n t a n s l a r v a e was markedly  the  reduced  i n t r e a t m e n t s w i t h h i g h f o o d l e v e l s and t h a t i n such c o n d i t i o n s the r a t e o f emergence was  increased.  I n the p r e s e n t  study o r g a n i c carbon l e v e l s were found t o be c o r r e l a t e d w i t h the number of emerging a d u l t s and the number o f emergence peaks.  Sorenson Lake, w i t h the l a r g e s t amount o f o r g a n i c  c a r b o n , has a Chironomus t e n t a n s p o p u l a t i o n t h a t develops much more r a p i d l y than t h e average.  There i s some i n d i c a t i o n ,  t h e n , t h a t the r e s u l t s r e p o r t e d by H a l l e t a l (1970) may a p p l i e d to t h i s n a t u r a l s i t u a t i o n .  The  be  same c o n n e c t i o n between  the p r o d u c t i v i t y o f an environment and r e p r o d u c t i v e success i s a l s o r e p o r t e d i n s t u d i e s o f the w a t e r bug  Cenocorixa  b i f i d a h u n g e r f o r d i (Jansson and Scudder, 1973).  Females i n  106 h i g h l y p r o d u c t i v e l a k e s developed  eggs up t o a month a f t e r  females i n l e s s p r o d u c t i v e l a k e s ceased  reproducing.  The i n c r e a s e i n o r g a n i c carbon i s accompanied by a d e c r e a s e i n the c o n c e n t r a t i o n o f d i s s o l v e d oxygen a t the mud s u r f a c e , r e s u l t i n g i n a n e g a t i v e c o r r e l a t i o n between s o l v e d oxygen and the abundance o f C. t e n t a n s . (1945), Gerry  (1951) and P a i n e and G a u f i n  dis-  Townes  (1956) r e p o r t t h a t  C. t e n t a n s p r e f e r s low oxygen l e v e l s t o h i g h ones and c o n s i d e r the s p e c i e s a good i n d i c a t o r o f p o l l u t e d w a t e r .  b)  Biotic Interactions  The l a c k o f n e g a t i v e c o r r e l a t i o n s between the abundance o f C. t e n t a n s and p o t e n t i a l l y competing o r p r e d a t o r y  species  i n d i c a t e s t h e r e i s l i t t l e a c t i v e s e p a r a t i o n o f the p o p u l a t i o n s i n the one meter zone, e i t h e r through d i f f e r e n t i a l r e a c t i o n to p h y s i c a l and c h e m i c a l f a c t o r s o r through b e h a v i o r a l activity.  F u r t h e r , the l a c k o f p o s i t i v e c o r r e l a t i o n s suggests  t h a t s t r o n g i n t e r a c t i o n between C. t e n t a n s and c o e x i s t i n g s p e c i e s i s reduced. Nevertheless, i t i s i n t e r e s t i n g that three species of the genus Chironomus c o e x i s t i n r e l a t i v e l y l a r g e numbers i n t h e one meter zone.  The c o m p e t i t i v e e x c l u s i o n p r i n c i p l e  has been f o r m u l a t e d by many w r i t e r s i n c l u d i n g E l t o n Hutchinson  (1957) and H a r d i n  r i z e s the modern v e r s i o n :  (1960).  DeBach  (1946),  (1966) summa-  " D i f f e r e n t species having  identical  e c o l o g i c a l n i c h e s cannot e x i s t f o r l o n g i n the same h a b i t a t " .  107 I n the case of C. t e n t a n s , C. a n t h r a c i n u s and  n.sp.,  the e c o l o g i c a l n i c h e s appear somewhat d i f f e r e n t . I t has been shown t h a t t h e r e i s a g e n e r a l s e p a r a t i o n o f the t h r e e s p e c i e s w i t h r e g a r d t o the l a k e s i n w h i c h each i s dominant, the i m p l i c a t i o n b e i n g t h a t the s p e c i e s have d i f f e r e n t p r e f e r e n c e s towards s a l i n i t y o r r e l a t e d f a c t o r s . F u r t h e r , Topping (1971) has observed and  n.sp.  t h a t C.  anthracinus  i n c r e a s e i n abundance w i t h depth,  showing  g r e a t e r d e n s i t i e s i n a r e a s n o t i n h a b i t e d by C. t e n t a n s . i s not c l e a r whether t h i s i n d i c a t e s some i n t e r s p e c i f i c  It inter-  a c t i o n p r e v e n t i n g C. t e n t a n s from a c t i v e l y l i v i n g below  two  meters o r whether i t s i m p l y r e v e a l s d i f f e r e n t t o l e r a n c e s to e n v i r o n m e n t a l v a r i a t i o n w i t h depth.  A t any r a t e , i n the  meter depth zone t h e r e i s no i n d i c a t i o n o f such s t r o n g ration.  The  one  sepa-  f a c t t h a t G^_n.sp. i s so abundant i n Barnes L.  where C. t e n t a n s and C. a n t h r a c i n u s cannot e x i s t may  simply  be a r e s u l t o f the i n s e c t l i v i n g i n i t s most f a v o r a b l e h a b i t a t r a t h e r than a r e s u l t o f d e c r e a s e d or  c o m p e t i t i o n f o r food  space. But the o p p o s i t e i s suggested by o t h e r i n f o r m a t i o n .  A l t h o u g h randomness was  not t e s t e d , smaller standard d e v i a -  t i o n s and the g r e a t e r smoothness o f the abundance curve  indicate  t h a t Cj_ n.sp.  than  i s more randomly d i s t r i b u t e d i n Barnes L.  i n other lakes.  P a t e r s o n and Fernando (1971) found  that  C. a t t e n u a t u s and G. b a r b i p e s , p r o b a b l y through a b e h a v i o r a l mechanism, tended  to become randomly d i s t r i b u t e d i n a u n i f o r m  environment when p r e s e n t i n h i g h d e n s i t i e s .  This  was  assumed to be a r e s u l t o f the l a c k of v a r i a t i o n i n the biotic  ( i . e . p r e d a t i o n and c o m p e t i t i o n ) and a b i o t i c e n v i r o n -  ment.  Barnes L. i s a good example o f such a h a b i t a t and i t  i s n o t s u r p r i s i n g t h a t s i m i l a r r e s u l t s a r e found. a l s o s t r i k i n g t h a t i n Barnes L. where C ^ n . s p .  It is  reaches  numbers t e n times those i n any o t h e r l a k e , the predaceous D. a l a s k e n s i s i s v e r y s c a r c e . C^n.sp. i s completely  I n L. Lye i t i s abundant w h i l e  absent.  Whether i t i s the h i g h s a l i n i t y o r the reduced  competi-  t i o n t h a t r e s u l t s i n the asynchronous emergence of C.  n.sp.  from Barnes L. i s unknown, but the l a t t e r i s a p o s s i b i l i t y . S i m i l a r s t a g g e r i n g o f developmental  times a r e e v i d e n t i n the  case of C. t e n t a n s .  show peaks o c c u r r i n g a t  The h i s t o g r a m s  d i f f e r e n t times from those o f C. a n t h r a c i n u s and  n.sp.  a l t h o u g h the p a t t e r n s a r e n o t i d e n t i c a l i n each l a k e .  That  C. t e n t a n s , C. a n t h r a c i n u s and G. b a r b i p e s f o u r t h i n s t a r abundances were c o r r e l a t e d i n May,  but n o t a f t e r w a r d s perhaps  i n d i c a t e s t h a t a d i f f e r e n t i a l development r a t e a f t e r the  May  emergences i s o p e r a t i n g to keep the p o p u l a t i o n peaks s t a g g e r e A s p a c i n g o f the l i f e c y c l e s o f c o e x i s t i n g i n s e c t s w i l l the i n t e n s i t y o f c o m p e t i t i o n f o r a v a i l a b l e r e s o u r c e s 1935;  lilies,  1952;  C o r b e t , 1964).  (Ide,  K a j a k e t a l (1968)  showed t h a t i n e x p e r i m e n t a l s i t u a t i o n s i n c r e a s e d i n t r a i n t e r s p e c i f i c c o m p e t i t i o n reduced  reduc  and  the i n t e n s i t y of f e e d i n g ,  slowed down growth and i n c r e a s e d m o r t a l i t y .  FIGURE 28  Examples o f the s p a c i n g o f emergence times o f Chironomus t e n t a n s and t h r e e c o e x i s t i n g  species.  A.  Chironomus a n t h r a c i n u s  B.  Chironomus n.sp.  C.  Glyptotendipes  barbipes  110 Other i n t e r a c t i o n s can be i n f e r r e d from the c o r r e l a tion studies.  When the l a r v a l numbers o f C. t e n t a n s a r e  h i g h the emergence times o f C. a n t h r a c i n u s a r e d e l a y e d v i c e v e r s a ) , perhaps i n d i c a t i n g s u p p r e s s i o n o f the ment o f the s c a r c e r s p e c i e s .  develop-  A dominant s p e c i e s l i k e l y  an advantage i n o b t a i n i n g f o o d .  (and  has  The per c e n t c o m p o s i t i o n of  C. t e n t a n s i s c o r r e l a t e d w i t h an i n c r e a s i n g number o f emergence peaks, s u g g e s t i n g a more r a p i d development i n a r e a s o f g r e a t e r dominance.  C. t e n t a n s emergence i s a l s o much g r e a t e r  i n h a b i t a t s where the d i v e r s i t y o f c h i r o n o m i d l a r v a e i s reduced. The  e v i d e n c e f o r e c o l o g i c a l s e p a r a t i o n o f C.  tentans  and i t s two r e l a t i v e s i s n o t d e c i s i v e , but t h e r e seems t o be a mechanism ( i . e . d i f f e r e n c e s i n d i a p a u s e . l e n g t h ) by w h i c h emergence t i m e s , and thus maximum development p e r i o d s , a r e staggered.  That C. a n t h r a c i n u s and  n.sp.  are f u r t h e r  s e p a r a t e d from C. t e n t a n s by depth i n d i c a t e s t h i s asynchrony may  be i m p o r t a n t o n l y i n the p e r i p h e r a l p a r t s o f the h a b i t a t  where c o n t a c t i s g r e a t e s t .  The problem o f the s e p a r a t i o n o f  C. a n t h r a c i n u s and  i s even more d i f f i c u l t .  n.sp.  gence times a r e more c l o s e l y l i n k e d preferences are a l s o s i m i l a r .  Emer-  ( F i g u r e s 18 - 2 2 ) ;  Chemical  tolerances are  depth dif-  f e r e n t , but i n a r e a s o f c o e x i s t e n c e the f a c t o r s t h a t a l l o w the two s p e c i e s to l i v e t o g e t h e r a r e u n c l e a r . C o r r e l a t i o n r e s u l t s show t h a t E i n f e l d i a pagana, G l y p t o t e n d i p e s b a r b i p e s and D. a l a s k e n s i s i n h a b i t the same  type o f h a b i t a t .  Because i t i s the l a r g e s t and most abundant  predaceous c h i r o n o m i d m i g h t be expected  i n the l a k e system, D. a l a s k e n s i s  to i n f l u e n c e the abundance o f C.  Owing to the l a r g e numbers o f E. pagana and G.  tentans.  barbipes,  these s p e c i e s a r e p r o b a b l y C. t e n t a n s ' s t r o n g e s t c o m p e t i t i o n ( b e s i d e s o t h e r Chironomus s p e c i e s ) f o r f o o d and The  space.  f o u r t h i n s t a r l a r v a e o f D. a l a s k e n s i s r e a c h  peak abundance d u r i n g e a r l y July.-  T h i s i s the p e r i o d d u r i n g  w h i c h the most s e r i o u s p r e d a t i o n on the l a r g e r might be expected  to o c c u r .  their  chironomids  A t t h i s time the m a j o r i t y of  C. t e n t a n s l a r v a e a r e a l s o f o u r t h i n s t a r .  S i n c e most  litera-  t u r e on the s u b j e c t of Tanypodine f o o d s t a t e s t h a t u s u a l l y newly hatched  chironomids  or l a t e r i n s t a r s o f the s m a l l e r  genera ( T a n y t a r s u s , P a g a s t i e l l a ) a r e eaten Armitage,  1968;  Roback, 1969)  (Leathers,  1922;  perhaps the o v e r a l l p r e d a t i o n  on C. t e n t a n s i s s m a l l . The  l i f e c y c l e s of G. b a r b i p e s and E. pagana a r e  s t a g g e r e d ; t h i s enables both s p e c i e s to dominate the l a k e s o f medium s a l i n i t y . these two  I n Westwick and Sorenson L a k e s d e n s i t i e s o f  s p e c i e s a r e u n u s u a l l y low, whereas C. t e n t a n s makes  up f i f t y per c e n t of the l a t e summer c h i r o n o m i d Sorenson Lake.  fauna i n  I n the o t h e r l a k e s the l a r g e number o f  G. b a r b i p e s j E. pagana and to some e x t e n t the o t h e r Chironomus s p e c i e s c r e a t e s a more i n t r i c a t e s t r u c t u r e t h a t l i k e l y r e s t r i c t s the success o f C.  tentans.  What i s the e x p l a n a t i o n f o r the low d e n s i t i e s  of  G. b a r b i p e s and E. pagana i n Sorenson and Westwick Lakes? I f the two s p e c i e s do n o t t h r i v e i n low oxygen and h i g h o r g a n i c carbon c o n d i t i o n s , then t h i s w o u l d be s u f f i c i e n t to lower t h e i r numbers. Goulding  But G e r r y  (1951) and S t u r g e s s  and  (1968, 1969) have c o n c l u d e d t h a t G l y p t o t e n d i p e s  lobiferus  and G. b a r b i p e s a r e more t o l e r a n t o f a n a e r o b i o s i s  than Chironomus s p e c i e s .  G. b a r b i p e s can s u r v i v e a n a e r o b i -  o s i s about t e n times l o n g e r than C. r i p a r i u s G o u l d i n g , 1968)  ( S t u r g e s s and  a l t h o u g h low oxygen c o n d i t i o n s reduce i t s  growth ( K i m e r l e and Anderson, 1971).  No p e r t i n e n t i n f o r m a -  t i o n i s a v a i l a b l e f o r E. pagana, but specimens kept i n b o t t l e d mud  and w a t e r were a b l e t o s u r v i v e a t l e a s t f i v e  days w h i l e Chironomus c o l l e c t i o n s d i e d a f t e r two days.  The  r e a s o n s f o r the lower numbers o f G. b a r b i p e s and E. pagana i n Westwick and Sorenson Lakes a r e n o t u n d e r s t o o d ;  neverthe-  l e s s , the absence o f h i g h l e v e l s o f c o m p e t i t i o n seems to p l a y an i m p o r t a n t r o l e i n the e x i s t e n c e o f C. t e n t a n s i n these lakes.  113 IV  CHIRONOMUS TENTANS AND SOME BIOTIC FACTORS AFFECTING CHROMOSOME INVERSION  A.  MATERIALS AND METHODS 1.  Background  Topping  (1969) has d e s c r i b e d t h e i n v e r s i o n f r e q u e n c i e s  i n t h e s a l i v a r y chromosomes o f some o f t h e same Chironomus t e n t a n s p o p u l a t i o n s t h a t t h e p r e s e n t study has a n a l y z e d . concluded t h a t the i n v e r s i o n frequencies d i f f e r e d  He  significant-  l y i n d i f f e r e n t lakes, but d i d not d i f f e r w i t h i n lakes.  It is  very important t o note that the frequencies of the i n v e r s i o n 1 Rad ( t h e i n v e r s i o n c o n s i d e r e d i n t h i s s t u d y ) do n o t v a r y s i g n i f i c a n t l y e i t h e r s e a s o n a l l y o r a n n u a l l y (Acton, pers. comm.; Topping, 1969).  The d e t a i l s o f these and o t h e r chromo-  some a n a l y s e s may be found i n Topping  (1969).  Topping n o t e s , "The i m p l i c a t i o n o f t h e l o n g term  stability  o f i n v e r s i o n s i n chromosome 1 i s t h a t t h e i n v e r s i o n s a r e adapted t o r e l a t i v e l y s t a b l e e n v i r o n m e n t a l f a c t o r s " .  There-  f o r e he attempted t o c o r r e l a t e t h e i n v e r s i o n f r e q u e n c y w i t h p h y s i c a l and c h e m i c a l parameters.  S u r p r i s i n g l y , none o f these  rather s t a b l e environmental f a c t o r s c o r r e l a t e d w i t h i n v e r s i o n f r e q u e n c y ; t h e o n l y v a r i a b l e t o do so was a b i o l o g i c a l one the number o f o t h e r c h i r o n o m i d s i n t h e environment. The l o n g term s t a b i l i t y o f i n v e r s i o n 1 Rad enables Topping's d a t a t o be u s e d i n f u r t h e r , more d e t a i l e d tion studies.  correla-  The v a r i a b l e "number o f o t h e r c h i r o n o m i d s " c a n  114 be d i v i d e d i n t o a number o f more r e s t r i c t e d b i o t i c  para-  meters .  2.  The U.B.C. T r i a n g u l a r R e g r e s s i o n Package  was a g a i n u s e d i n the c o r r e l a t i o n a n a l y s i s .  Unfortunately  the use o f a s e r i e s o f l a k e s i n t h i s study s l i g h t l y  differ-  ent from the one examined by Topping p r e c l u d e s t h e d i r e c t comparison  of c o r r e l a t i o n s .  Topping u s e d t w e l v e l a k e s f o r  h i s a n a l y s i s ; o n l y t h e e i g h t l a k e s i n the p r e s e n t h a v i n g i n v e r s i o n d a t a a r e used h e r e .  study  115 B.  RESULTS Three e n v i r o n m e n t a l  f a c t o r s were found t o c o r r e l a t e  ( p < . 0 5 ) w i t h the i n v e r s i o n frequency  o f 1 Rad (Table X V I ) .  These a r e sodium c o n c e n t r a t i o n (.770), d i s s o l v e d oxygen (.740) and t h e amount o f o r g a n i c c a r b o n i n t h e h a b i t a t (-.796). A s i g n i f i c a n t c o r r e l a t i o n between t h e number o f G l y p t o t e n d i p e s b a r b i p e s l a r v a e and 1 Rad f r e q u e n c i e s  (.734)  was a l s o d i s c o v e r e d (Table X V I I ) . There was no s i g n i f i c a n t c o r r e l a t i o n between t h e 1 Rad f r e q u e n c i e s and t h e t o t a l number o f c h i r o n o m i d s , the i n d e x o f d i v e r s i t y .  biomass o r  TABLE XV  I n v e r s i o n f r e q u e n c i e s i n chromosome 1 of C. t e n t a n s . 1967.  Samples c o l l e c t e d i n  From Topping, 1969.  Water Body  Frequency of i n v e r s i o n Rad  Frequency of i n v e r s i o n Rade  L. J a c k s o n  79.4  20.6  364  L. Greer  81.4  18.6  220  Near P h a l a r o p e  77.3  22.7  1168  Near O p p o s i t e Crescent  74.3  25.7  214  Barkley  74.7  25.3  186  E a s t L.  78.6  21.4  220  Westwick L.  73.6  26.4  1220  Sorenson L.  74.3  25.7  2066  L.  Sample Size  TABLE X V I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and some environmental f a c t o r s . of freedom a t p=.05  W i t h 6 degrees  r = 0.707 i s s i g n i f i c a n t and r = 0.834 a t p=.01.  1 Rad 1 Rad  Conductivity.  TDS  Na  K  Ca  Mg  co  3  HC0  3  Cl  S  °4  °2  .411 1.000  T.D.S.  .434  .983 1.000  Na  .770  .872  .869 1.000  K  .668  .766  .713  .914 1.000  Ca  -.135  .747  .717  .405  .312 1.000  Mg  -.197  .774  .768  .379  .274  .849 1.000  .434  .909  .867  .824  .758  .710  HCO3  .404  .182  .056  .419  .716 -.092 -.246  .327 1.000  Cl  .556  .890  .944  .869  .700  .581  .603  .723  .196  .899  .936  .653  .434  .792  .895  .764 -.258  .858 1.000  .740  .419  .540  .620  .387 -.068  .082  .251 -.175  .729  .467 1.000  -.245  .652  .673  .328  .196  .607  .867  .507 -.313  .493  .780  -.796 -.104 -.140 -.521 -.585  .465  .394 -.152 -.510 -.316  so  3  4  °2 pH Organic Carbon T o t a l nos. chironomids Index of diversity Biomass  Total nos. Diverch i r - s i t y B i o Index mass on.  1.000  Conductivity  C0  PH  Organic Carbon  .438 -.102 -.030 -.377 -.129 -.259 .345 -.096 -.005  .275  .671 1.000  .272 -.322 -.482 -.004  .295 -.174  .343  .015  .117  .023 1.000  .281  .109 1.000  .120 -.631  .125 -.236  .351 1.000  .325 -.277 -.637 1.000  .242 -.451 -.217 -.818 -.195  .149 -.014 -.097 -.410 -.228 -.131  .222 -.092  .569 -.319  .389 -.328 -.187  .595  I-  1  TABLE X V I I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and t h e abundance o f some c h i r o n o m i d s . 6 degrees o f freedom  With  r=0.707 i s  s i g n i f i c a n t a t p=.05 and r=0.834 a t p=.01.  1 Rad  1 Rad  1.000  DegPtanypuji alaskensis.  0-415  Derotany- E i n f e l d i a pus pagana alaskensis  Chironomus Chironomus Chironomus Glyptoten- P r o c l a d i u s CryptoRest of tentans n.sp. a n t h r a c i - dipes (.all chironomus Species nus barbipes species) psittacinus  1.000  / Einfeldia  0.429  0.272  1.000  --344  0.194  -0.648  1.000  Chironomus n.sp  0-663  0.385  0.332  -0.318  1.000  Chironomus anthracinus  0.064  -0.029  0.639  -0.513  -0.071  1.000  Glyptotendipes barbipes  0.734  0.291  0.674  -0.561  0.428  0.525  1.000  Procladius ( a l l species)  0.329  0.460  0.690  -0.224  -0.051  0.453  0.278  1.000  Cryptochironomus psittacinus  "0.512  -0.217  -0.743  0.802  -0.438  -0.243  -0.441  -0.595  1.000  Rest of species  0.565  0.646  0.425  -0.057  0.156  -0.173  0.475  0.520  -0.456  pagana  Chironomus tentans  1.000  Co  TABLE X V I I I  Summary o f c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between the f r e q u e n c y o f 1 Rad and t h e p e r c e n t c o m p o s i t i o n o f some c h i r o n o m i d s . W i t h 6 degrees o f freedom  (samples  from 8 l a k e s ) r=.707 i s s i g n i f i c a n t a t p=.05 and r=.834 a t p=.01.  1 Rad  1  Rad  Derotany- E i n f e l d i a pus pagana alaskensis  Chironomus Chironomus Chironomus G l y p t o t e n - P r o c l a d i u s C r y p t o Remainder tentans n.sp. a n t h r a c i - dipes (all chironomus o f nus barbipes species) psittaSpecies cinus  1.000 .392  1.000  0.324  -.714  1.000  Chironomus tentans  -.556  .837  .828  1.000  Chironomus n. sp.  .564  .041  .262  .100  1.000  Chironomus anthracinus  .371  -.672  .109  ,489  -.258  1.000  Glyptotendipes Barbipes  .538  .644  .007  -.461  .084  .820  1.000  .213  -.004  .024  -.226  .501  .333  .085  1.000  .570  .790  .648  .863  .016  -.465  -.545  ,273  1.000  -.141  .606  -.161  ,212  -.133  .583  -.549  .428  .333  Derotanypus alaskensis Einfeldia pagana  .Procladius (.ail s p e c i e s ) Cryptochironomus psittacinus Remainder cf species  1.000  h-  1  TABLE X I X  Summary o f the c o r r e l a t i o n c o e f f i c i e n t s d e s c r i b i n g t h e r e l a t i o n s h i p between t h e f r e q u e n c y o f 1 Rad and some emergence variables.  W i t h s i x degrees o f freedom  r=0.707 i s s i g n i f i c a n t a t p=.05 and r=0.834 a t p=.01.  V a r i a b l e s used a r e  emergence numbers, number o f emergence peaks and the time of t h e main emergence.  D.  E.  aTaskensis gana nos. nos.  £L  tentans nos.  n. sp. nos.  .C*.  G.  D.  P  anth-  EITrb-  TTnqV- 7^  nos  ™ =  i p e a k s  P.alaskpnsJg  .561  1.000  .299  .553  1.000  -.632  -.335  -.164  p  « —  . p e a k s  n o  *  p e a k s  n o  p  -  £L  k s  no.  —  D.  no  —  E.  C  —  £  «~  a  t l m c  a  r  n -Cinus  s  »  ti  jpes  ^  t l m e  numbers E.pagana numDers  ^ e n ^ n s  1.000  Amber's  -  S^piflua  .324 .057 .543 -.168 .911 1.000  Snipes  .097 .391 .832 -.238  .210 .188 1.000  ^ l l g p l l ^  .535  .788  .481  -.594  .215  ^fSfrf.peaks  ^  ^  ^  -  S f f p e a k s  -  5  -°  5 ? 5  1  8  - °  9  8  7  5  '  -  S 5 6  -271  4 5 0  -  1 6 5  9 1 5  1.000  .  .315  .400  - 2 5 4 -.370 .474 -085  1.000  .445  1.000  .060  .064  -.304  -.316  1.000  -°04  -.050  -.070  .316  -.180  1.000  tTo-?em rg. peaks  *  C.anthracinus no.ernerg.peaks  -.223  -.032  -.302  -.101  -.048  .324  -.330  .257  -.086  -.026  .436  C.barbipes no.emerg. peaks  -.002  .356  -.223  .022  -.399  -.186  -.134  .565  .046  .124  -.124  D. a l a s k e n s i s emerg.time  .362  .167  .148  -.538  .380  .432  .277  .541  .101  -.288  .576  i^rfttme  '  ^  .™  -258 -.863 -.058 .230 .278 .156 1.000  .162  .i09  -230 .589  ?  C^ | f  £  f  ^  e  3 6 5  -.237 -  C ^ a g n ^ s .  fm^ifH  1 6 5  1 6 9  .744  -  -  2 9 ?  .135  -  -  2  3  8  '™  .295  2 2 3  .021  -  "-  1 7 3  2  «  3 3 4  -.170  2  1 2 2  - " ° -™  .437 -  -  8  ?  -.257  .155 -  3  °  .036  -™  .266 6  '  2  3  .713  4  .339  -.246  1. 000 .455 1.000 • •»-/.» J-.^UU .540  .319  1.000  .727  -.200  -.189  .028  -.002  -.748  1.000  .472  -.037  .852  .323  -.098  .701  -.242  .256  1.000  -.183  -.139  .018  .827  .711  .556  .437  -.177  .013  1.000  - 0 7 1 - 5 5 3 -.776 -.120 -.515 .376 -.297 .451 -.221 -.294 -.182 .151 -.413 .166 -.540 1.000  to  C.  DISCUSSION  The  s t i m u l u s f o r a t t e m p t i n g a study o f the b i o t i c  i n t e r a c t i o n s i n f l u e n c i n g C. t e n t a n s was  Topping's (1969)  f i n d i n g t h a t the f r e q u e n c y o f i n v e r s i o n s i n chromosome 1 was  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 the number of o t h e r  chironomids  i n the environment.  Thus the study up t o t h i s  p o i n t has been concerned w i t h the e x a m i n a t i o n o f e n v i r o n mental i n f l u e n c e s t h a t m i g h t a f f e c t C. t e n t a n s . C o r r e l a t i o n r e s u l t s suggest t h a t C. t e n t a n s i s p a r t i c u l a r l y s u c c e s s f u l i n Sorenson and Westwick Lakes where oxygen l e v e l s a r e low and o r g a n i c carbon l e v e l s a r e h i g h . A l s o a s s o c i a t e d w i t h these l a k e s a r e the drop i n l a r v a l abundance and the poor emergence of E. pagana and  especial-  l y G. b a r b i p e s . S i n c e oxygen l e v e l s , o r g a n i c carbon and the abundance of G. b a r b i p e s c o r r e l a t e w i t h i n v e r s i o n f r e q u e n c y , chromosome i n v e r s i o n may factors.  i n some way  the  be connected w i t h these  I n v e r s i o n f r e q u e n c i e s a r e l o w e s t i n Sorenson and  Westwick Lakes where C. t e n t a n s i s f a v o u r e d , s u g g e s t i n g the i n v e r s i o n may  c o n t r o l a mechanism r e d u c i n g c o m p e t i t i o n  w i t h G. b a r b i p e s i n a r e a s where p o t e n t i a l i n t e r a c t i o n i s greatest. I t was  p r e v i o u s l y n o t e d t h a t the abundances of  C. t e n t a n s and G. b a r b i p e s a r e c o r r e l a t e d i n May,  but n o t i n  FIGURE 29  S e a s o n a l v a r i a t i o n i n the f r e q u e n c i e s of i n v e r s i o n s o f chromosome 1. P e r c e n t a g e s e x p r e s s e d a l o n g the o r d i n a t e have been c o n v e r t e d by a r c s i n transformation.  Samples a r e from Near  P h a l a r o p e L a k e , 1967. 1969.  From Topping,  122  90 i  10  A — i  MAY  j —  JUNE  1  1  1  1  JULY  AUG.  SEPT.  OCT.  1  NOV.  123 any  subsequent months and i t was  postulated that during  the emergence of o v e r w i n t e r i n g l a r v a e or e a r l y i n the summer g e n e r a t i o n a s p a c i n g of the peak d e v e l o p m e n t a l periods occurred.  F i g u r e 29 shows t h a t the f o u r t h i n s t a r  l a r v a e c o l l e c t e d i n May  had lower i n v e r s i o n f r e q u e n c i e s  i n chromosome 1 than those c o l l e c t e d throughout the r e s t of the summer.  The  l a t e May  emergences of C. t e n t a n s  made up from o v e r w i n t e r i n g f o u r t h i n s t a r l a r v a e .  are  I f these  l a r v a e are the ones showing lower i n v e r s i o n f r e q u e n c i e s , then subsequent c o l l e c t i o n s of f o u r t h i n s t a r l a r v a e would meet w i t h o n l y o v e r w i n t e r i n g l a r v a e and  summer g e n e r a t i o n  displaying higher inversion frequencies. then the change i n i n v e r s i o n f r e q u e n c y  larvae  I f t h i s i s so,  between May  i s a s s o c i a t e d w i t h the i n i t i a l emergence of C.  and  June  tentans.  I t i s p o s s i b l e t h a t the p o r t i o n of o v e r w i n t e r i n g l a r v a e d e s t i n e d to emerge i n l a t e May itself  has l e s s tendency to  (or somehow reduce i n t e r a c t i o n ) from G.  barbipes.  T h i s b e h a v i o u r w o u l d n o t be d i s a d v a n t a g e o u s d u r i n g I n s p r i n g and  summer, when food and  the i n v e r s i o n f r e q u e n c y  segregate  diapause.  space a r e a t a premium,  i s h i g h e r and  the mechanism r e d u c i n g  i n t e r a c t i o n w o u l d become more i m p o r t a n t .  Thus the mechanism  might v a r y on a temporal as w e l l as a l a k e b a s i s ; whenever the p o t e n t i a l c o m p e t i t i o n from G. b a r b i p e s i s h i g h , frequency  of the i n v e r s i o n 1 Rad  i n v e r s i o n i n a l a r v a prolongs e v i d e n c e to support o u t l i n e d above.  i s high.  diapause.  the  Perhaps the There i s no  real  t h i s t h e o r y , but i t f i t s the p o s t u l a t e s  C l a r i f i c a t i o n o f the i n t e r a c t i o n s between C.  tentans  and o t h e r s p e c i e s and o f t h e r o l e o f t h e chromosome i n v e r s i o n i s most l i k e l y t o come from e x t e n s i v e l a b o r a t o r y e x p e r i m e n t s conducted on c o n t r o l l e d p o p u l a t i o n s of t h e species involved.  M o n i t o r i n g t h e e f f e c t s of d i f f e r e n t  s p e c i e s and d e n s i t y m i x t u r e s , food l e v e l s and l i g h t regimes on l i f e c y c l e s and i n v e r s i o n f r e q u e n c i e s s h o u l d enable more d e f i n i t e c o n c l u s i o n s t o be drawn than were p o s s i b l e i n t h i s field  study.  125 V  CONCLUSION  Mundie (1957) i n h i s comprehensive study o f t h e Chironomidae o f London r e s e r v o i r s s t a t e s , "The study o f chironomids  can be seen, h i s t o r i c a l l y , t o have f o l l o w e d  two main l i n e s w h i c h may be termed t h e l i m n o l o g i c a l and the e n t o m o l o g i c a l .  One has been concerned w i t h t h e d i s -  t r i b u t i o n o f d i f f e r e n t k i n d s of c h i r o n o m i d s  i n different  l a k e s , w i t h t h e a s s o c i a t i o n o f these w i t h l a k e t y p e s , and w i t h numbers and w e i g h t s productivity.  of chironomids  as a s p e c t s o f l a k e  The o t h e r has d e a l t w i t h t h e b i o l o g y o f  p a r t i c u l a r species, w i t h t h e i r feeding h a b i t s , r e s p i r a t i o n , voltinism, etc.  These two l i n e s converge a t one p o i n t ,  the c e n t r a l i s s u e i n e c o l o g y , i . e . , t h e problem o f t h e n a t u r a l c o n t r o l of populations". The p r e s e n t study has d e a l t w i t h b o t h o f these major lines.  The l i m n o l o g i c a l a s p e c t s o f t h e work have p l a c e d  a somewhat d i f f e r e n t emphasis on c h i r o n o m i d The  d i f f e r e n t chironomid  distribution.  a s s o c i a t i o n s d e s c r i b e d seem t o be  determined l a r g e l y by s a l i n i t y and a s s o c i a t e d p r o d u c t i v i t y l e v e l s r a t h e r than by oxygen c o n c e n t r a t i o n s as has been c l a i m e d f o r o t h e r l a k e s ( B r u n d i n , 1951). The  second avenue o f s t u d y , t h e e n t o m o l o g i c a l , p l a y s  a prominent r o l e i n t h e i n v e s t i g a t i o n .  A major c o n t r i b u t i o n  of t h e work has been a r e v i s i o n o f the d i s t r i b u t i o n o f many of t h e c h i r o n o m i d  s p e c i e s under c o n s i d e r a t i o n .  The f a c t t h a t  126 t h i s p a r t i c u l a r i n s e c t fauna has been l a r g e l y n e g l e c t e d i n B r i t i s h Columbia i s emphasized by the r e s u l t s : s p e c i e s new  to B.C.,  s p e c i e s new  to s c i e n c e  One  f i v e s p e c i e s new  eleven  t o Canada and  seven  (Appendix).  of the main h i n d r a n c e s t o advances i n e c o l o g y i s  taxonomic a m b i g u i t y  (Macan, 1963).  I f u n d e r l y i n g taxonomy  i s c o n f u s e d a l l e c o l o g i c a l d i s c u s s i o n s and c o n c l u s i o n s a r e n e c e s s a r i l y meaningless  ( L i n d e b e r g , 1967).  Great p a i n s  were taken t o make the b e s t p o s s i b l e i d e n t i f i c a t i o n o f the species.  The importance  of b e i n g aware of taxonomic prob-  lems i n d e a l i n g w i t h e c o l o g i c a l s t u d i e s cannot be o v e r emphasized. Topping  (1969) has shown t h a t the same p o p u l a t i o n s o f  C. t e n t a n s examined i n t h i s study d i s p l a y d i f f e r e n c e s i n the f r e q u e n c y o f chromosome i n v e r s i o n s . suggests t h a t these i n v e r s i o n s may  The p r e s e n t  thesis  r e g u l a t e a mechanism r e -  d u c i n g c o m p e t i t i o n between C. t e n t a n s and o t h e r s p e c i e s , e s p e c i a l l y G. b a r b i p e s .  Such a r e s u l t i s i n  accordance  w i t h g e n e t i c t h e o r y w h i c h c o n s i d e r s i n v e r s i o n s t o be  adapted  to s p e c i f i c e c o l o g i c a l c o n d i t i o n s (Swanson, 1957; F o r d ,  1964).  Such statements c o n c e r n i n g the f u n c t i o n o f i n v e r s i o n s i n p o p u l a t i o n s of C. t e n t a n s a r e l a r g e l y s p e c u l a t i v e a t t h i s time.  However, s i n c e so l i t t l e f i e l d work has been done on  s i m i l a r problems,  any i n s i g h t a t a l l i n t o the q u e s t i o n i s o f  use t o e c o l o g i c a l l y o r i e n t e d g e n e t i c s .  T h i s work may  serve  as a b a s i s f o r f u r t h e r l a b o r a t o r y s t u d i e s t e s t i n g the v a l i d i t y  of t h e c o r r e l a t i o n s p r e s e n t e d , aspects and  o r s t u d i e s examining o t h e r  o f the r e l a t i o n s h i p between t h e c h i r o n o m i d  t h e chromosome i n v e r s i o n f r e q u e n c i e s o f C.  complex  tentans.  A l t h o u g h t h e main o b j e c t i v e was t o attempt t o r e l a t e the b i o l o g y o f C. t e n t a n s  to the biology of c o e x i s t i n g  s p e c i e s , the study has thrown some l i g h t on t h e way s p e c i e s l i f e c y c l e s and s p e c i e s c o m p o s i t i o n saline lake series.  may d i f f e r w i t h i n a  The t h e s i s t h a t a s p e c i e s ' l i f e h i s t o r y  and p o p u l a t i o n s t r u c t u r e may v a r y r a d i c a l l y i n c l o s e l y a s s o c i a t e d lakes o f d i f f e r i n g chemical  and b i o l o g i c a l con-  s t i t u t i o n has never r e a l l y been t e s t e d i n t h e f i e l d The  phenology o f t h e s p e c i e s o f t e n v a r i e s c o n s i d e r a b l y  l a k e t o l a k e even though t h e l a k e s may be c l o s e and  before.  superficially similar.  from  together  D i f f e r e n c e s i n s p e c i e s composi-  t i o n and abundance w i t h i n t h e same type o f h a b i t a t a r e t o be e x p e c t e d ; environments a r e n e v e r q u i t e t h e same even when they appear t o be.  The r e s e a r c h ,  concept n o t always a p p r e c i a t e d  then, emphasizes a b a s i c  - what i s c o n s i d e r e d  a species  i s c a p a b l e o f much v a r i a t i o n i n i t s response t o v a r y i n g environmental c o n d i t i o n s . A l t h o u g h t h e u l t i m a t e o b j e c t o f any study o f n a t u r a l communities i s a d e t a i l e d u n d e r s t a n d i n g and  of the o r g a n i z a t i o n  i n t e r a c t i o n s o f component p o p u l a t i o n s ,  t a k i n g i s t o o v a s t f o r a p r e l i m i n a r y study  such an undersuch as t h i s .  Mundie (1957) n o t e s t h a t g e n e r a l s h o r t term s u r v e y s o f t h e chironomid  faunas o f l a k e s a r e l i k e l y t o prove i n s u f f i c i e n t l y  i n t e n s i v e t o add much new knowledge.  In the present case,  however, j u s t i f i c a t i o n f o r such a survey (which i s as much concerned w i t h d e f i n i n g problems as s o l v i n g them) r e s t s on t h e f a c t t h a t a s a l i n e l a k e s e r i e s has n o t been p r e v i o u s l y s t u d i e d w i t h c h i r o n o m i d s i n mind.  The t h e s i s  was u n d e r t a k e n t o add t o t h e knowledge we have o f t h e s a l i n e l a k e s i n q u e s t i o n , and i s a p a r t o f a c o n t i n u i n g e x a m i n a t i o n of how b i o l o g i c a l systems f u n c t i o n i n such environments.  129 LITERATURE CITED  A c t o n , A.B. and G.G.E. Scudder, 1971. The zoogeography and r a c e s o f Chironomus (Tendipes) t e n t a n s Fab. L i m n o l o g i c a 8:83-92. ' Anderson, J . F . and S.W. H i t c h c o c k . 1968. B i o l o g y o f Chironomus a t r e l l a i n a t i d a l cove. Ann. e n t . Soc. Am. 1968:1597-16U3~:  Anderson, R.O. 1951. 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P h i l a . 107:167-206.  APPENDIX  S p e c i e s I d e n t i f i e d i n t h e Study * New r e c o r d s f o r B r i t i s h Columbia ** New r e c o r d s f o r Canada *** S p e c i e s new t o s c i e n c e  FAMILY CHIRONOMIDAE SUBFAMILY TANYPODINAE Tribe Tanypodini Tanypus p u n c t i p e n n i s Tribe  Meigen  Macropelopiini  Subtribe  Macropelopiina  Derotanypus a l a s k e n s i s  (Malloch)*  Derotanypus n . s p . * * *  Subtribe  Procladiina  Procladius  (Psilotanypus) bellus  Procladius  ( P s i l o t a n y p u s ) n i e t u s Roback  Procladius freemani Sublette P r o c l a d i u s r u r i s Roback P r o c l a d i u s dentus Roback * P r o c l a d i u s c l a v u s Roback * P r o c l a d i u s s u b l e t t e i Roback P r o c l a d i u s n.sp. ***  (Loew)  Tribe  Pentaneurini  Ablabesmyia p e l e e n s i s  (Whalley) *  SUBFAMILY ORTHOCLADIINAE Tribe O r t h o c l a d i i n i N a n o c l a d i u s n.sp. *** Cricotopus  albanus Curran *  Cricotopus  f l a v i b a s i s Malloch  Cricotopus  trifasciatus  Acricotopus  **  (Panzer) *  n i t i d e l l u s Malloch  **  P s e c t r o c l a d i u s barbimanus (Edwards) * P s e c t r o c l a d i u s z e t t e r s t e d t i B r u n d i n ** P s e c t r o c l a d i u s n.sp. ***  SUBFAMILY CHIRONOMINAE Tribe  Chironomini  Chironomus a n t h r a c i n u s  Zetterstedt  Chironomus a t r e l l a (Townes) * Chironomus t e n t a n s F a b r i c i u s Chironomus plumosus  (Linnaeus)  Chironomus n.sp. (near a t r i t i b i a ) *** Chironomus n.sp. *** E i n f e l d i a pagana Meigen * Cryptochironomus p s i t t a c i n u s Meigen * Cryptotendipes  a r i e l ( S u b l e t t e ) **  142 Endochironomus n i g r i c a n s Johannsen Glyptotendipes  barbipes  P o l y p e d i l u m n.sp.  (Staeger)  ***  Tribe Tanytarsini C a l o p s e c t r a g r a c i l e n t a (Holmgren) * Calopsectra holochlorus  (Edwards) **  

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