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Geographic variation in courtship behaviour of the guppy, Poecilia reticulata Ballin, Peter J. 1973-12-31

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CAGEOGRAPHIC VARIATION IN COURTSHIP BEHAVIOUR OF THE GUPPY, POECILIA RETICULATA  by PETER J . BALLIN A.B., U n i v e r s i t y o f C a l i f o r n i a , B e r k e l e y , 1968  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 December, 1973  In p r e s e n t i n g t h i s t h e s i s  in p a r t i a l  f u l f i l m e n t o f the requirements  an advanced degree at the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree the L i b r a r y  s h a l l make i t f r e e l y  available for  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  r e f e r e n c e and copying o f t h i s  It  i s understood that copying or  thesis  permission.  Department of  ^  OG  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  3  or  publication  o f 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 without my written  that  study.  f o r s c h o l a r l y purposes may be granted by the Head of my Department by h i s r e p r e s e n t a t i v e s .  for  ii  ABSTRACT  T h i s t h e s i s attempts t o e l u c i d a t e some a d a p t i v e m o d i f i c a t i o n s o f behaviour i n response t o environmental i n f l u e n c e s i n g e o g r a p h i c a l l y i s o l a t e d p o p u l a t i o n s o f t h e guppy. courtship behaviour o f d  P o e c i l i a r e t i c u l a t a , P e t e r s , I examined  guppies from t h r e e T r i n i d a d streams  d i f f e r i n s e v e r a l p h y s i c a l and b i o t i c p a r a m e t e r s .  which  Males o f two head-  s t r e a m p o p u l a t i o n s ( t h e P a r i a and Upper A r i p o R i v e r s ) a r e l a r g e r and more b r i g h t l y c o l o r e d t h a n dd Headstream dd dd  o f a l o w l a n d s t r e a m ( t h e Guayamare  River).  a r e more c o n s p i c u o u s i n t h e i r c o u r t s h i p t h a n downstream  i n a one d -one  and move around the  % e n c o u n t e r : t h e y e x h i b i t more d i s p l a y b e h a v i o u r % more.  I t was c o n c l u d e d t h a t d i f f e r e n c e s i n be-  haviour are genetic. I then i n v e s t i g a t e d e f f e c t s o f d <^o*  were much more a g g r e s s i v e t h a n Upper A r i p o o r Guayamare  e n c o u n t e r i n g o t h e r dd P  dd  o f t h e same r a c e .  o c c u r r e d i n the p r e s e n c e o f  D i s p l a y b e h a v i o u r was reduced two  i n t e r a c t i o n s on c o u r t s h i p .  , suggesting that  dd were i n t r o d u c e d t o one a n o t h e r and a  dd  and t h e  £.  over  2 a f t e r an i s o l a t i o n  h a v i o u r s d e c r e a s e d w i t h the a d d i t i o n o f a t h i r d d Upper A r i p o r a c e s , b u t n o t i n t h e Guayamare.  fight  , who f o u g h t ) when  However, no d e c r e a s e was n o t e d w i t h o u t an i s o l a t i o n p e r i o d .  d i s t a n c e between dd  upon  Increased aggressiveness i n  ( e s p e c i a l l y i n P dd  generally heightened the l e v e l o f  dd  Paria  period.  D i s p l a y be-  i n t h e P a r i a and  I n c r e a s i n g t h e number o f  ^ - o r i e n t e d a c t i v i t y and r e d u c e d t h e  dd  Preferences  f o r f i s h o f the same r a c e o c c u r r e d .  one o f each r a c e , were p r e s e n t e d  to a v i r g i n 2  f o u g h t o n l y i n t h e p r e s e n c e o f P a r i a 22  22 , and Guayamare  behaviour  s i m u l t a n e o u s l y , P a r i a dd  e s p e c i a l l y from Upper  t h r u s t more a t Guayamare  .  Choice  e x p e r i m e n t s r e v e a l e d t h a t v i r g i n P a r i a and Guayamare  selectively to 22  dd  dd o f t h e i r own r a c e .  ,  , Upper A r i p o d i s p l a y s were  more s u c c e s s f u l i n e l i c i t i n g s e x u a l r e s p o n s e s , Aripo  When t h r e e dd  In another experiment,  respond Upper A r i p o  responded much more r e a d i l y t o d i s p l a y s from Upper A r i p o males.  Females seem more l i k e l y t o complete f u l l s e x u a l r e s p o n s e s w i t h dd  of  t h e i r own r a c e . I t appears t h a t r e l a t i v e l y l i g h t p r e d a t i o n and good v i s i b i l i t y have r e s u l t e d i n t h e e v o l u t i o n o f d i s p l a y i n g and f i g h t i n g as t h e p r i m a r y s t r a t e g i e s i n headstreams.  Heavy p r e d a t i o n and p o o r v i s i b i l i t y have  r e s u l t e d i n s e l e c t i o n f o r downstream  dd w h i c h d i s p l a y l e s s f r e q u e n t l y  and r e l y more h e a v i l y on t a c t i l e s i g n a l s t o i n s u r e i n s e m i n a t i o n . model i s p r e s e n t e d  t o s u g g e s t how b e h a v i o u r a l d i f f e r e n c e s e v o l v e d .  r e s u l t s a r e d i s c u s s e d i n l i g h t o f o t h e r s t u d i e s on g e o g r a p h i c i n c o l o r and m a t i n g  mating  behaviour.  A simple The  variation  iv  ACKNOWLEDGEMENTS I thank Dr. N. R. L i l e y , my research s u p e r v i s o r , f o r i n t r o d u c i n g me t o guppies, p r o v i d i n g support and f a c i l i t i e s , and c r i t i c a l l y reading the manuscript.  I am also thankful t o my  research committee, Dr. I . E. E f f o r d and Dr. J . D. McPhail, f o r comments and d i s c u s s i o n s . I am e s p e c i a l l y g r a t e f u l to Dr. M. C u l l e n , who as v i s i t i n g p r o f e s s o r a t U.B.C, gave generously h i s advice, r e s o u r c e f u l n e s s , and good cheer. I express my appreciation to a number o f people who k i n d l y a s s i s t e d me during t h i s  study:  To f e l l o w students, e s p e c i a l l y Dr. D. L. Kramer and Dr. B. H. Seghers, f o r discussions and comradeship; Mr. W. P. Wishlow, f o r t e c h n i c a l assistance and a perspective on s a n i t y ; Mr. C. Parkinson and Mr. A. Koppel f o r help with equipment; Ms. J . Meredith f o r c r i t i c a l reading o f the manuscript; Mr. S. W. Borden, Ms. D. Lauriente, and Ms. R. Kardynal f o r the computer work; Ms. L. Duncan f o r measuring guppy photos; Ms. V. L. Lennox f o r drawing some f i g u r e s and p u t t i n g up with me most o f the time; and Ms. P. Waldron for typing.  v  TABLE OF CONTENTS  Page  Abstract  •  Acknowledgements  i i ••• •  L i s t of Tables  iv x  L i s t o f Figures  xii  Chapter 1.  Introduction  1  2.  The Environment and the Animals  4  A.  The environment  4  1.  Locations and i s o l a t i o n of the streams....  4  2.  A b i o t i c features  6  3.  B i o t i c features  6  B.  C. 3.  4.  The f i s h  8  1.  Range  8  2.  Morphology  3.  Sex r a t i o s  11  4.  D i s t r i b u t i o n of f i s h i n the streams.......  13  Summary  —  .  8  14  M a t e r i a l s and Methods  15  A.  Maintenance  15  B.  Subjects  16  C.  Observational set-ups  17  D.  Recording and analyzing instruments  18  A Comparison o f Male Courtship S t r a t e g i e s  19  vi Page A.  G e n e r a l i n t r o d u c t i o n and b e h a v i o u r described  B.  •  D.  E.  19  A d e s c r i p t i v e a n a l y s i s o f the courtship o f the three populations  C.  patterns  (Experiment 1)  21  1.  Introduction  21  2.  M a t e r i a l s and Methods  21  3.  Results  24  a.  Orientation  24  b.  C o n t a c t movements  29  c.  Display  29  d.  C o r r e l a t i o n s o f behaviours  35  Threshold distances  f o r courtship  (Experiment 2 ) . . . .  35  1.  Introduction  35  2.  M a t e r i a l s and Methods  36  3.  Results  36  C o m p e t i t i o n i n c o u r t s h i p I (Experiment 3 ) . . . .  40  1.  Introduction  40  2.  M a t e r i a l s and Methods  40  3.  Results  40  P i l o t e x p e r i m e n t s on t h e r o l e o f male-male during courtship  aggression  (Experiments 4, 5, and 6 ) . .  1.  Introduction  2.  A g g r e s s i o n and t e r r i t o r y  42 42  (Experiment 4 ) . .  44  a.  Introduction  44  b.  M a t e r i a l s and Methods  44  c.  Results  44  vii  Page Chapter 3.  4.  F.  G.  Aggression and females (Experiment 5)  .  a.  Introduction  47  b.  Materials and Methods  47  c.  Results  47  Aggression, females, and density (Experiment 6)...  49  a.  Introduction  49  b.  Materials and Methods  49  c.  Results  49  Competition in courtship II (Experiment 7)  50  1.  Introduction  50  2.  Materials and Methods  50  3.  Results  52  Competition in courtship III (Experiment 8)......  59  1.  Introduction  59  2.  Materials and Methods  59  3.  Results  60  a.  Effects of the different numbers of males on the courtship performed  b.  60  Contributions of different males to the total courtship  „  H.  47  61  c.  Interactions between the males  63  d.  Comparison of the races  67  Summary of the male's courtship...  70  1.  70  The behaviour of single males  2. The behaviour of two or more males  '.  70  viii  Chapter  P  Strategies  .  a  g  e  5.  D i s c u s s i o n o f Male C o u r t s h i p  74  6.  The Consequences o f G e o g r a p h i c I s o l a t i o n  81  A.  Introduction.....  81  B.  B r e e d i n g between t h e r a c e s  81  C.  Inter-population competition  i n courtship  ( E x p e r i m e n t 9)  82  1.  Introduction  "  82  2.  M a t e r i a l s and Methods  83  3.  Results  83  a.  Male behaviours  83  b.  Females as r e c i p i e n t s o f male b e h a v i o u r s . . . .  87  c.  Female b e h a v i o u r s  89  d.  Male-female i n t e r a c t i o n  92  D.  Female s e l e c t i v i t y  94  E.  C h o i c e t e s t 1 (Experiment 1 0 ) .  94  1.  Introduction  96  2.  M a t e r i a l s and Methods  96  3.  Results  96  F.  G.  C h o i c e t e s t 2 (Experiment 11)  99  1.  Introduction  99  2.  M a t e r i a l s and Methods  99  3.  Results  Reactive  distances  101 o f females (Experiment 1 2 ) . . . . . . .  101  1.  Introduction  101  2.  M a t e r i a l s and Methods  103  ix Chapter  Page 3.  H.  Results  103  Summary o f the female's r e s p o n s e  105  7. D i s c u s s i o n o f Geographic V a r i a t i o n  106  A.  Geographic v a r i a t i o n i n c o l o r  106  B.  Geographic v a r i a t i o n i n mating behaviour  113  Literature Cited  118  Appendix 1. Some S p e c u l a t i o n and F i n d i n g s about B l a c k M a r k i n g s o f t h e Male Guppy.  .  131  2. A D e s c r i p t i o n o f Guppy B e h a v i o u r P a t t e r n s P e r t a i n i n g to Courtship  134  X  LIST OF TABLES Table  Page  la.  Temperature,  pH, and DH v a r i a t i o n ; T r i n i d a d , 1969.  7  lb.  Stream d i m e n s i o n s , f l o w , and v e l o c i t y ; T r i n i d a d , 1969....  7  lc.  Water t u r b i d i t y and c o l o r , s u b s t r a t e c o m p o s i t i o n , and  7  amount o f l i g h t i n g ; T r i n i d a d  7  2.  C a r o t e n o i d pigment i n w i l d f i s h c o l l e c t e d i n 1967  12  3.  Sex r a t i o s i n w i l d f i s h  12  4.  S t a n d a r d l e n g t h s o f f i s h o b s e r v e d i n Experiment  5a.  Orientation distances  5b.  O c c u r r e n c e o f f i s h w i t h i n one male f i s h - l e n g t h  1........  26 (approx.  2 cm) o f each o t h e r 6.  23  26  A n g l e o f male l o n g a x i s t o l o n g h o r i z o n t a l a x i s o f female w h i l e o r i e n t a t i n g  27  7.  Display distances  32  8.  Differences i n frequencies of courtship a c t i v i t i e s  of  i n d i v i d u a l males when t e s t e d a l o n e w i t h a female (Experiment 1) o r i n the p r e s e n c e o f a n o t h e r male ( E x p e r i m e n t 7) 9.  53  Male charges i n a c o m p e t i t i o n s i t u a t i o n o f two males and one f e m a l e .  10.  Mean p e r c e n t a g e o f t i m e i n t r i a l  54 i n which a male  was  w i t h i n one male f i s h - l e n g t h (approx 2 cm) o f a female i n one-male and two-male s i t u a t i o n s 11.  55  O c c u r r e n c e o f males w i t h i n a 2 cm r a d i u s o f a female i n the two-male s i t u a t i o n  56  xi Table 12.  '  Page  Correlation coefficients of courtship a c t i v i t i e s i n a two-male, one-female s i t u a t i o n . . .  13.  R e l a t i v e amount o f d i s p l a y b e h a v i o u r  of f i r s t  58 and  second males on days 2 and 3. 14.  Summary o f m o r p h o l o g i c a l , b e h a v i o u r a l , and environmental  15.  66  d i f f e r e n c e s between t h e r a c e s  Response i n d i c e s females  73  (# g l i d e s / # d i s p l a y s ) f o r v i r g i n  w i t h males o f d i f f e r e n t r a c e s i n c o m p e t i t i o n  w i t h one another  95  xii LIST OF FIGURES Figure  Page  1.  Northern T r i n i d a d  5  2.  Male guppies from t h e P a r i a , Upper A r i p o , and 9  Guayamare R i v e r s o f T r i n i d a d . 3.  S i z e s o f w i l d - c a u g h t male guppies i n T r i n i d a d . . . .  10  4.  Three-way c h o i c e maze  17  5.  R e l a t i v e p o s i t i o n s recorded i n Experiment  6.  Mean a n g l e s o f o r i e n t a t i o n by males w i t h r e s p e c t t o  1  t h e h o r i z o n t a l p l a n e o f t h e female 7.  28  O c c u r r e n c e o f males i n p o s i t i o n s above, below, and i n f r o n t o f a female  8.  22  30  A comparison o f mean number o f b o u t s o f s i g m o i d d i s p l a y s and mean p e r c e n t a g e o f time i n t h e t r i a l s p e n t d i s p l a y i n g by males o f t h r e e r a c e s o f g u p p i e s . .  9.  33  Schematic r e p r e s e n t a t i o n o f male d i s p l a y s i n v a r i o u s p o s i t i o n s r e l a t i v e t o a female....  10.  Aquarium s e t - u p f o r Experiment  11.  Mean times u n t i l f i r s t  2, t o p view  34 37  d i s p l a y and mean number o f  bouts o f d i s p l a y a t t h e s h o r t e s t d i s t a n c e (0 cm) from t h e females 12.  39  C o u r t s h i p o f two males i n t h e p r e s e n c e o f one f e m a l e , e x p r e s s e d as p e r c e n t a g e s o f t o t a l c o u r t s h i p («*"l + d 2) (a.) and time i n t r i a l  13.  (b.)  41  C o u r t s h i p o f two males w i t h one f e m a l e , e x p r e s s e d i n seconds  43  xiii  Figure 14.  Page Number o f charges by males i n each o f t h r e e observation periods i n all-male aquaria.............  15.  46  Mean number o f male charges i n : (1) 5-male g r o u p s , (2) t h e same 5-male groups i n t o which 5 females were i n t r o d u c e d , and (3) t h e same groups as i n (2) from w h i c h 3 females were removed  16.  48  Number o f male charges i n groups o f 5 f i s h o f one sex,  and t h e s e same groups a f t e r 5 a d d i t i o n a l  f i s h o f e i t h e r t h e same o r o p p o s i t e s e x were introduced 17.  51  Comparison o f t h e c o u r t s h i p p e r f o r m e d by d i f f e r e n t numbers o f males w i t h one female  18.  62  C o n t r i b u t i o n s o f d i f f e r e n t males t o t o t a l  courtship  on each day o f t h e e x p e r i m e n t 19.  Comparison o f t h e c o u r t s h i p p e r f o r m e d by males o f the  20.  64  t h r e e r a c e s on each o f t h e days o f t h e t r i a l s . . .  A s i m p l e model showing f a c t o r s i n f l u e n c i n g male conspicuousness  21.  68  75  E x p e r i m e n t a l s e t - u p f o r E x p e r i m e n t 9..  84  i 22.  Comparison o f t h e c o u r t s h i p p e r f o r m e d by t h r e e m a l e s , one o f each r a c e , t o s i n g l e  virgin  females o f a l l r a c e s 23.  86  Comparison o f t h e c o u r t s h i p p e r f o r m e d by t h r e e males, one o f each r a c e , t o v i r g i n females o f each r a c e  88  xiv  Figure 24.  Page R e l a t i v e p o s i t i o n s o f f i s h and t h r u s t s r e c e i v e d by v i r g i n females from males o f d i f f e r e n t r a c e s i n c o m p e t i t i o n w i t h one a n o t h e r  25.  .  90  D i s p l a y b e h a v i o u r s r e c e i v e d by v i r g i n females o f d i f f e r e n t r a c e s from males o f d i f f e r e n t r a c e s i n c o m p e t i t i o n w i t h one a n o t h e r  26.  Responses  91  o f v i r g i n females t o males o f d i f f e r e n t  races  93  27.  E x p e r i m e n t a l s e t - u p f o r E x p e r i m e n t 10  97  28.  E x p e r i m e n t a l s e t - u p f o r E x p e r i m e n t 11  100  29.  P r e f e r e n c e s f o r males o f d i f f e r e n t r a c e s by v i r g i n 1  no  and e x p e r i e n c e d f e m a l e s 30.  Aquarium s e t - u p f o r E x p e r i m e n t 12  31.  A r e a s o f t h e male guppy's l a t e r a l s u r f a c e used t o q u a n t i f y b l a c k markings  104  133  C h a p t e r 1.  Introduction  Numerous s t u d i e s o f m a t i n g b e h a v i o u r have been c a r r i e d out a t species  l e v e l , but  tion differences.  little  i n q u i r y has been d i r e c t e d toward i n t e r p o p u l a -  Indeed, v e r y l i t t l e e f f o r t has been expended t o  c l a r i f y the a d a p t i v e n a t u r e o f a n i m a l v a r i a t i o n i n g e n e r a l 7).  the  (see C h a p t e r  S i n c e s u r v i v a l depends upon the a b i l i t y o f i n d i v i d u a l s t o c o n t r i b u t e  t o t h e subsequent g e n e r a t i o n , any g i v e n p o p u l a t i o n must have e v o l v e d  or  be e v o l v i n g the most e f f i c i e n t means t o do so i n i t s p a r t i c u l a r e c o l o g i c a l situation.  There are good r e a s o n s f o r b e l i e v i n g t h a t t h e l o c a l  breeding  p o p u l a t i o n i s the e v o l u t i o n a r y u n i t o f i m p o r t a n c e ( e . g . , E h r l i c h and Raven, 1969), and t h e r e f o r e i t would seem p r o p i t i o u s t o b e g i n a for  b e h a v i o u r a l d i f f e r e n c e s at the p o p u l a t i o n I f we  f i n d behavioural  search  level.  d i f f e r e n c e s between p o p u l a t i o n s  of  animals,  can we t h e n r e l a t e t h e s e d i f f e r e n c e s t o d i s s i m i l a r i t i e s i n the e n v i r o n m e n t ? I f we  can t h e n a s c e r t a i n t h a t t h e s e l e c t i v e agents i n t h e environment  i n f l u e n c e genotypes a s s o c i a t e d w i t h b e h a v i o u r a l g a i n some u n d e r s t a n d i n g The  o f how  behaviour  d i f f e r e n c e s , we  evolves.  guppy, P o e c i l i a r e t i c u l a t a P e t e r s , i s an i d e a l a n i m a l w i t h w h i c h  t o a s s e s s b e h a v i o u r a l d i f f e r e n c e s between n a t u r a l p o p u l a t i o n s . e x p r e s s such a h i g h degree o f m o r p h o l o g i c a l a multitude o f d i v e r s e environments. in  should  E s p e c i a l l y s t r i k i n g are d i f f e r e n c e s  e x p r e s s e d i n the l a r g e r , d r a b l y a t t i r e d  These c o l o r p a t t e r n s ,  not  ??, seem t o be i n v o l v e d i n i n t r a -  appear t o be i m p o r t a n t  Brower, and W a t e r b o l k , 1955;  animals  v a r i a b i l i t y and o c c u r i n such  c o l o r p a t t e r n s o f dd f r o m d i f f e r e n t a r e a s .  s p e c i f i c communication and  Few  H a s k i n s et^ al_. , 1961;  i n mating  (Baerends,  L i l e y , 1966).  In  2 addition,  <£ guppies spend much o f t h e i r day i n v o l v e d i n c o u r t s h i p  a c t i v i t i e s , and a r e e a s i l y o b s e r v e d .  A complete q u a l i t a t i v e and q u a n t i -  t a t i v e d e s c r i p t i o n o f guppy m a t i n g b e h a v i o u r  by L i l e y  (1966) i s a v a i l a b l e  as a b a s e l i n e f o r comparison o f n a t u r a l p o p u l a t i o n s . The p o p u l a t i o n s  chosen f o r t h i s s t u d y o r i g i n a t e i n t h r e e  geographi-  c a l l y i s o l a t e d streams i n T r i n i d a d , where t h e guppy i s n a t i v e , and r e p r e s e n t t h r e e o f t h e most d i s s i m i l a r demes w i t h r e s p e c t t o morphology and e c o l o g y .  Two o f t h e p o p u l a t i o n s  o r i g i n a t e i n headstreams where t h e  w a t e r i s c l e a r , p r e d a t o r s r e l a t i v e l y few, and d* guppies l a r g e and b r i g h t l y colored.  P h y s i c a l f a c t o r s remain f a i r l y constant  y e a r i n t h e s e two l o c a t i o n s .  throughout the  However, c o l o r p a t t e r n s o f t h e  <t g u p p i e s  d i f f e r : t h o s e o f t h e P a r i a R i v e r i m p r e s s one as b e i n g o r a n g e - r e d and t h o s e o f t h e Upper A r i p o R i v e r appear b l u i s h w i t h i r i d e s c e n c e and l a r g e o c e l l a t e d black spots.  The t h i r d p o p u l a t i o n comes from a l a r g e r l o w l a n d r i v e r where  the w a t e r i s t u r b i d , p r e d a t o r s  abundant, and <f guppies s m a l l and r e l a -  t i v e l y d u l l i n c o l o r a t i o n . H e r e , i n t h e Guayamare R i v e r , p h y s i c a l c o n d i t i o n s such as t u r b i d i t y , w a t e r f l o w , and t e m p e r a t u r e a r e more v a r i a b l e t h a n i n t h e headstream l o c a t i o n s .  A more e x t e n s i v e d e s c r i p t i o n o f t h e f i s h  and t h e environment i s g i v e n i n C h a p t e r 2. H a s k i n s et_ al_. (1961), i n c o n j u n c t i o n w i t h an e c o l o g i c a l s t u d y o f guppies i n T r i n i d a d , found t h a t l a b - r a i s e d b r i g h t e r ( t o humans) <*V were more s u c c e s s f u l than " d u l l e r "  d"d" i n i n s e m i n a t i n g  ?? .  The s t u d y  also  i n d i c a t e d t h a t the b r i g h t e r g u p p i e s were more l i k e l y t o s u f f e r p r e d a t i o n . The a u t h o r s  s u g g e s t e d t h a t s e x u a l s e l e c t i o n was p o s s i b l y p r e s s u r i n g f o r  more c o n s p i c u o u s  d* c o l o r a t i o n , w h i l e p r e d a t i o n was s e l e c t i n g f o r c/  3  crypsis.  I n n e i t h e r case was t h e b e h a v i o u r o f t h e f i s h t a k e n i n t o con-  sideration. respect  This  i s a major o m i s s i o n , as Seghers (1973) has shown w i t h  t o a n t i p r e d a t o r b e h a v i o u r and I hope t o show w i t h r e s p e c t t o  courtship  behaviour.  My f i r s t o b j e c t i v e was t o d e t e r m i n e , t h r o u g h d e s c r i p t i v e and e x p e r i mental a n a l y s e s , from p o p u l a t i o n  whether o r n o t <£ c o u r t s h i p b e h a v i o u r does i n d e e d d i f f e r to population.  My second o b j e c t i v e was t o r e l a t e o b s e r v e d  differences i n courtship strategies to differences i n the natural ment. and  T h i r d l y , I examined t h e s u c c e s s o f d i f f e r e n t c o u r t s h i p  the responsiveness o f ? ?  to various  environ-  strategies  o V i n an attempt t o e l u c i d a t e  the e f f e c t s o f g e o g r a p h i c i s o l a t i o n and s e x u a l  s e l e c t i o n as mechanisms i n  the e v o l u t i o n o f b e h a v i o u r and e t h o l o g i c a l i s o l a t i o n .  4 C h a p t e r 2.  The Environment  and t h e A n i m a l s  A.  The  environment  1.  L o c a t i o n s and i s o l a t i o n o f t h e streams The t h r e e streams from w h i c h the f i s h o r i g i n a t e — the P a r i a , Upper  A r i p o , and Guayamare R i v e r s - - a r e shown on t h e accompanying west T r i n i d a d ( F i g . 1 ) .  map  of north-  The P a r i a and t h e Upper A r i p o b e g i n i n t h e  N o r t h e r n M o u n t a i n range a t a l t i t u d e s o f a p p r o x i m a t e l y 1000 m and c o u r s e through r e l a t i v e l y u n t r a c t a b l e j u n g l e .  The Guayamare i s a l o w l a n d s t r e a m  w h i c h f l o w s t h r o u g h open c o u n t r y c u l t i v a t e d m o s t l y w i t h s u g a r cane. A ten-meter w a t e r f a l l a t t h e mouth o f t h e P a r i a and a f i v e - m e t e r w a t e r f a l l between t h e Upper and Lower A r i p o e f f e c t i v e l y s e p a r a t e t h e s e streams from any upstream movements o f g u p p i e s .  Thus, we can c o n s i d e r  the guppy p o p u l a t i o n s o f t h e s e two streams t o be i n a b s o l u t e g e o g r a p h i c isolation.  Guppies can be washed down s t r e a m , b u t the chance o f any o f  t h e t h r e e p o p u l a t i o n s under s t u d y m i x i n g a r e s l i m . system,gene  To r e a c h t h e C a r o n i  f l o w from t h e P a r i a would have t o e x t e n d t h r o u g h many k i l o -  meters o f ocean, where guppies a r e r a r e l y , i f e v e r , f o u n d .  Gene f l o w  from t h e Upper A r i p o would i n v o l v e d about 20 k i l o m e t e r s o f t h e Lower A r i p o and the C a r o n i , a c a n a l t o t h e Guayamare, and t h e n s e v e r a l k i l o m e t e r s downstream.* I n a d d i t i o n , d a t a from H a s k i n s e t a l . (1961) i n d i c a t e t h a t g u p p i e s t e n d t o adhere t o l o c a l i z e d g r o u p s , s u g g e s t i n g t h a t a d i s p l a c e d f i s h cease i t s wanderings upon e n c o u n t e r i n g more g u p p i e s .  might  Furthermore, Eaton  *The e x i s t e n c e o f t h i s c a n a l was r e p o r t e d t o L i l e y and Seghers b u t n e v e r o b s e r v e d by them.  5  F i g . 1.  Northern Trinidad.  populations studied.  Arrows i n d i c a t e s o u r c e s o f  A f t e r Seghers  (1973).  6 (1970) and E h r l i c h and Raven (1969) suggest that reproduction by some migrants may not s i g n i f i c a n t l y a f f e c t the unique spectrum o f genotypes i n a population.  Therefore, I believe that we may s a f e l y r e f e r to the  three populations as being geographically i s o l a t e d . 2.  A b i o t i c features Some measurements o f chemical and physical parameters o f the three  streams may be found i n Tables l a , b, and c. Note that the lowland r i v e r , the Guayamare, may be distinguished from the other two streams by i t s higher temperature, lack of shading, greater depth, larger volume of flow, and, perhaps most important 3.  to courtship, i t s t u r b i d i t y .  B i o t i c features Vegetation i s absent except during flood waters i n the Guayamare,  when plants along i t s banks are submerged. p r i n c i p a l l y on invertebrate d r i f t .  The guppies seem to feed  Most important  f o r t h i s study i s what  feeds upon guppies. The ubiquitous cyprinodontid Rivulus h a r t i i has circumvented the w a t e r f a l l b a r r i e r s to the i s o l a t e d headstreams, j o i n i n g an otherwise impoverished  f i s h fauna.  This f i s h i s moderately abundant i n the Upper  Aripo and r e l a t i v e l y scarce i n the P a r i a . strated, Rivulus i s an important d"  guppies.  As Seghers (1973) has demon-  predator mostly upon immature and young  P o t e n t i a l a e r i a l predators i n the form o f kingfishers  (Chloroceryle spp.) have been sighted along the Paria, s i t u a t i o n i n the Guayamare i s quite d i f f e r e n t .  The predator  Here, among an abundance  of large f i s h e s , the characid Hoplias malabaricus  and the c i c h l i d  7  Table l a . Stream  Temperature, PH, and DH v a r i a t i o n , T r i n i d a d , Dates  N  Guayamare  16/3-30/6  9  Upper Aripo  29/3-3/7  3  Paria  18/4-29/6  4  Temp, mean and range 29. r 27-31  1969.  pH mean and range  DH(ppm) mean and range  7.0 6.8-7.1  108.6 70-130  24.6 24.5-24.8  7.5 7.4-7.6  183.3 150-210  25.4 25-26.5  7.0 7.0-7.1  96.7 90-100  T a b l e l b . Stream d i m e n s i o n s , f l o w , and v e l o c i t y ; T r i n i d a d , 1969. Stream  Date  Guayamare  30/6  Upper Aripo  no d a t a  Paria  Width mean § range(m)  Depth mean g range(m)  Volume o f f l o w (m /sec)  Velocity (m/sec)  2.00  1.50  1,080  .400  similar to Paria  18/4  3.50 3-4  §29/6  Table l c .  3  .17 .14-.20  .0779 .0729-.0828  .168 163-.172  Water t u r b i d i t y and c o l o r , s u b s t r a t e c o m p o s i t i o n , and amount of l i g h t i n g ; T r i n i d a d .  Stream  Turbidity  Color  Substrate  Guayamare  brown  mud and silt  no c o v e r t o o c c a s i o n a l s u g a r canes a l o n g s h o r e  Upper A r i p o  turbid-always, b u t variable clear  white  rocky, silt in pools  75% c o v e r * o f low bushes --medium t o dense shade w i t h o n l y a few s p o t s exposed  Paria  clear  % o f cover i n d i c a t e s a f t e r S e g h e r s , 1973  Lighting  (Cover)  lightly rocky 50% c o v e r o f low bushes stained -medium shade how much s k y i s o b s c u r e d b y v e g e t a t i o n ,  8  C r e n i c i c h l a a l t a a r e t h e most s i g n i f i c a n t guppy p r e d a t o r s ( S e g h e r s , 1973). A more d e t a i l e d t r e a t m e n t o f guppy environments may Seghers  (1973).  H a s k i n s et_ al_.  be found i n  (1961) g i v e a g e n e r a l account o f guppy  ecology.  B.  The  fish  1.  Range The o r i g i n a l d i s t r i b u t i o n o f P o e c i l i a r e t i c u l a t a i s f r e s h w a t e r o f  t h e i s l a n d o f T r i n i d a d and t h e n o r t h e a s t e r n c o r n e r o f South A m e r i c a , o f which T r i n i d a d i s f a u n i s t i c a l l y a p a r t .  Because o f i t s r e m a r k a b l e a d a p t a -  b i l i t y , the guppy has been i n t r o d u c e d i n t o t r o p i c a l w a t e r s a l l o v e r t h e w o r l d t o a i d i n mosquito  2.  control.  Morphology ? guppies from the t h r e e p o p u l a t i o n s a r e v i r t u a l l y  a l t h o u g h a f t e r p r a c t i c e , I can d i s c e r n P a r i a by t h e i r deeper b o d i e s and d a r k e r s h a d i n g . f u l , smaller  indistinguishable,  from t h e o t h e r two t y p e s I n marked c o n t r a s t , t h e c o l o r -  cfd* d i f f e r g r e a t l y and a r e easy t o a s s i g n t o t h e i r home  streams. In the c l e a r headwaters  o f t h e P a r i a and Upper A r i p o , t h e o V  r e l a t i v e l y l a r g e and c o n s p i c u o u s l y c o l o r e d . and much l e s s c o n s p i c u o u s Guayamare <*V  Compare them w i t h the s m a l l e r  ( F i g s . 2 and 3 ) .  has shown a g e n e t i c b a s i s f o r t h e s e s i z e d i f f e r e n c e s . o f l a r g e areas o f o r a n g e - r e d i n the P a r i a f i s h .  Liley  (unpubl.)  Note t h e p r e s e n c e  Seghers has compared t h e  p e r c e n t a g e o f t h e body s u r f a c e c o v e r e d by c a r o t e n o i d pigments  i n several  r a c e s and has q u a n t i t a t i v e l y c o n f i r m e d t h i s i m p r e s s i o n ( T a b l e 2; and S e g h e r s , u n p u b l ) .  are  Liley  F u r t h e r m o r e , the q u a l i t y o f the c a r o t e n o i d s seems  9  F i g . 2.  Male guppies from t h e P a r i a , Upper A r i p o , and Guayamare  Rivers of Trinidad.  (Ektachrome: N.R.  Liley).  9a  10  Fig.  3.  S i z e s o f w i l d - c a u g h t <t guppies i n T r i n i d a d .  The v e r t i c a l  l i n e i s t h e mean, t h e shaded b a r +_ 2 S.E., t h e empty b a r +_ 1 S . D . , the h o r i z o n t a l l i n e t h e r a n g e , and t h e number i n d i c a t e s t h e sample size.  From S e g h e r s ,  1973.  UPPER '  AR1PO  ^«8i  48  I  P A R 1A  100  58  GUAYAMARE  i  1  16  Cf  • » * i 1  17  18  TOTAL  19  20  21  LENGTH  22  23  24  25  26  27  28  29  30  (mm)  o P3  11  d i f f e r e n t from t h o s e o f t h e o t h e r r a c e s .  Turning t o other c o l o r s ,  Upper A r i p o f i s h appear b l u i s h , c o n t a i n i n g g u a n i d i n e p i g m e n t , and e x h i b i t i r i d e s c e n c e and l a r g e b l a c k s p o t s , o f t e n c i r c l e d w i t h i r i d e s c e n t white.  The Guayamare f i s h e x p r e s s  are subdued.  a great v a r i e t y o f c o l o r s , but they  F u r t h e r m o r e , t h e y l a c k t h e markings on t h e body and t a i l  which make t h e headwater f i s h c o n s p i c u o u s t o t h e human a n d , p r e s u m e d l y , t o t h e p i s c i n e eye. An a n a l y s i s o f t h e amount o f b l a c k markings and t h e i r p o s s i b l e s i g n i f i c a n c e was u n d e r t a k e n and i s r e p o r t e d i n A p p e n d i x I.  Two c o r r e l a t i o n s s h o u l d be c o n s i d e r e d :  (1) t h e more c o n s p i c u o u s  o c c u r i n c l e a r w a t e r and t h e l e s s c o n s p i c u o u s * / (2) t h e l a r g e r dd o c c u r w i t h a s m a l l p r e d a t o r A r i p o and P a r i a ) and t h e s m a l l e r  occurs i n t u r b i d water; ( R i v u l u s i n t h e Upper  d occurs w i t h large predators  c h l a and H o p l i a s i n t h e Guayamare).  dd  (Crenici-  Regarding the causal b a s i s o f the  second c o r r e l a t i o n , Seghers (1973) has o b s e r v e d t h a t l a r g e guppies g i v e R i v u l u s h a n d l i n g d i f f i c u l t i e s and dd a r e e a t e n more r e a d i l y t h a n whereas s m a l l guppies appear t o be more e f f e c t i v e i n e v a d i n g  ;  large preda-  t o r s and ? ? a r e a t no advantage.  3.  Sex r a t i o s Seghers (1973) has found t h a t u n b a l a n c e d guppy s e x r a t i o s c o i n c i d e  w i t h t h e abundance o f R i v u l u s . Thus we f i n d t h a t  outnumber dd by 2  t o 1 i n t h e Upper A r i p o , w h i l e t h e o t h e r two streams have more n e a r l y balanced  sex r a t i o s  (Table 3 ) . L a b o r a t o r y  t i o n s e x h i b i t a 1:1 s e x r a t i o .  r e a r e d f i s h from a l l p o p u l a -  Seghers p r e s e n t s  convincing evidence that  12  T a b l e 2.  C a r o t e n o i d pigment i n w i l d f i s h c o l l e c t e d i n 1967. E x p r e s s e d as t h e p e r c e n t a g e o f s u r f a c e a r e a c o v e r e d on t h e l e f t s i d e o f t h e body. From S e g h e r s , 1973.  Stream  N  Avg  Paria  33  28.9  Upper A r i p o  40  12.4  Guayamare  50  9.4  T a b l e 3.  Sex r a t i o s i n w i l d f i s h .  Stream  dV  Paria  292  Upper A r i p o Guayamare  SD  "  Range  11.3  10.4-50..7  7.7  1.4-33.,8  4.1  1.4-20..8  From S e g h e r s , 1973. Immatures  N  dV?  256  212  760  1.14  252  528  565  1345  .48  110  120  85  315  .92  13 R i v u l u s i s i n d e e d t h e cause o f t h i s i m b a l a n c e . adept a t a v o i d i n g c a p t u r e t h a n  Male g u p p i e s were l e s s  and were a t a d i s a d v a n t a g e i n s i z e -  s e l e c t i v e .predatibn,., ,  4.  D i s t r i b u t i o n o f f i s h i n t h e streams O b s e r v a t i o n s by Seghers i n d i c a t e t h a t guppies t e n d t o i n h a b i t  pools  and b a c k - e d d i e s where w a t e r v e l o c i t i e s a r e n i l o r v e r y c l o s e t o i t . F i e l d and l a b o r a t o r y o b s e r v a t i o n s  b y Seghers show t h a t Guayamare  fish  swim n e a r t h e w a t e r s u r f a c e and c l o s e t o s h o r e , w h i l e t h e h e a d s t r e a m f i s h swim n e a r t h e s u b s t r a t e and show no p r e f e r e n c e t i o n t o shore.  of position i n rela-  P o s i t i o n s t a k e n by guppies i n t h e Guayamare seem t o c o r r e -  spond t o where t h e p r e d a t o r s  are not.  The degree o f s c h o o l i n g b e h a v i o u r shown by t h e g u p p i e s c o r r e s p o n d s t o t h e degree o f p r e d a t i o n upon them. wellydeveloped  Thus, we f i n d s c h o o l i n g b e h a v i o u r  i n f i s h f r o m t h e Guayamare, p o o r l y d e v e l o p e d i n t h e Upper  A r i p o , and a b s e n t i n t h e P a r i a ( S e g h e r s , 1973). These d i f f e r e n c e s i n p o s i t i o n a l p r e f e r e n c e s persist i n laboratory-reared  stocks.  and s c h o o l i n g b e h a v i o u r  Seghers and I t h e r e f o r e , b e l i e v e  t h a t t h e s e d i f f e r e n c e s r e f l e c t g e n e t i c d i f f e r e n c e s which r e s u l t from s e l e c t i o n due t o p r e d a t i o n .  14 C.  Summary  1.  Three g e o g r a p h i c a l l y i s o l a t e d p o p u l a t i o n s  o f guppies o r i g i n a t e  from t h r e e e c o l o g i c a l l y d i f f e r e n t streams i n T r i n i d a d . 2.  The p o p u l a t i o n s  w i t h l a r g e r , more c o n s p i c u o u s <£d f r e q u e n t  clear  headstreams o f t h e P a r i a and Upper A r i p o R i v e r s , w h i c h  contain only a  s m a l l guppy p r e d a t o r .  d occurs  t u r b i d lowland  The s m a l l e r , l e s s c o n s p i c u o u s  s t r e a m , t h e Guayamare, i n w h i c h s e v e r a l l a r g e  in a predators  occur. 3.  The p r e d a t o r  Rivulus i s probably  r e s p o n s i b l e f o r an u n b a l a n c e d sex  r a t i o (Id" :2 ??) i n t h e Upper A r i p o R i v e r .  Sex r a t i o s a r e n e a r l y  b a l a n c e d i n t h e o t h e r two s t r e a m s . 4.  D i f f e r e n c e s i n p o s i t i o n s i n streams seem t o have r e s u l t e d from  s e l e c t i o n by p r e d a t o r s . 5.  The degree o f s c h o o l i n g e x p r e s s e d by g u p p i e s c o r r e s p o n d s t o t h e  degree o f p r e d a t i o n upon them. 6.  D i f f e r e n c e i n c o l o r a t i o n , s i z e , and b e h a v i o u r p e r s i s t i n l a b o r a t o r y  populations.  T h i s i m p l i e s t h a t the d i f f e r e n c e s have a g e n e t i c b a s i s .  15 C h a p t e r 3. A.  M a t e r i a l s and Methods  Maintenance F i s h from t h e P a r i a , Upper A r i p o , and Guayamare R i v e r s  (the  fish  p o p u l a t i o n s w i l l h e r e a f t e r be r e f e r r e d t o as P, UA, and G, r e s p e c t i v e l y ) were housed i n p h y s i c a l and v i s u a l i s o l a t i o n from one a n o t h e r i n 43 liter  (51.5  cm x 27 cm x 31 cm deep) and 61 l i t e r  cm deep) a q u a r i a .  (62 cm x 32 cm x 31  S i m i l a r conditions p r e v a i l e d i n a l l the stock  aquaria,  as f o l l o w s : Photoperiod:  12L : 12D  Lighting: c o o l w h i t e 40 o r 30-watt f l u o r e s c e n t b u l b s 15 cm above t h e w a t e r  suspended  S u b s t r a t e : medium g r a v e l Vegetation: and Lemna.  a l l p o s s i b l e combinations o f V a l l i s n e r i a , C e r a t o p t e r i s ,  Water: one h a l f t o o n e - t h i r d o f each aquarium was changed r e g u l a r l y w i t h Vancouver c i t y w a t e r and l o c a l w e l l w a t e r pH:  approx 6.0  F i l t r a t i o n : o u t s i d e f i l t e r s o f c h a r c o a l and f i b e r g l a s s w o o l . Some a q u a r i a used s u b - g r a v e l f i l t e r s , b u t t h e s e were r e p l a c e d due t o a tendency f o r t h e w a t e r t o become a c i d . Food: t w i c e d a i l y on T e t r a - M i n , and chopped T u b i f e x worms  t r o u t chow, f r o z e n b r i n e s h r i m p ,  Temperature: d u r i n g t h e f i r s t p a r t o f t h i s s t u d y , f i s h were housed i n f o u r s e p a r a t e rooms. Temperature was c o n t r o l l e d b y h e a t e r - t h e r m o s t a t s a t about 25 C i n t h r e e o f t h e rooms: t h e f o u r t h room was supposedl y under t h e r m o s t a t i c c o n t r o l , b u t i n f a c t v a r i e d from 24 t o 31 C. F i s h were moved t o new f a c i l i t i e s i n O c t o b e r , 1970, where t h e c o n t r o l l e d t e m p e r a t u r e room k e p t t h e w a t e r a t 25 + .5 C. Density: an attempt was made t o keep a q u a r i a a t a p p r o x i m a t e l y equal d e n s i t i e s by n o n - s e l e c t i v e l y removing immature f i s h t o l a r g e t r o u g h s . G f i s h seemed t o m u l t i p l y more q u i c k l y t h a n e i t h e r o f t h e o t h e r r a c e s .  16 In a d d i t i o n , a q u a r i a w i t h t h e most p l a n t s u s u a l l y c o n t a i n e d t h e most young. An " a v e r a g e " 43 1 aquarium h e l d about 50 f i s h , o f which s l i g h t l y more than h a l f were immature. B.  Subjects F i s h were c o l l e c t e d i n T r i n i d a d i n 1967 ( L i l e y and Seghers) and  1969 ( S e g h e r s ) .  See Seghers  (1973) f o r c o l l e c t i n g t e c h n i q u e s .  Wild-  caught t o s i x t h g e n e r a t i o n l a b o r a t o r y - b r e d a n i m a l s were o b s e r v e d i n experiments. aquaria.  A l l f i s h observed, except v i r g i n  were from the s t o c k  Care was e x e r c i s e d t o s e l e c t f i s h from as many a q u a r i a as  p o s s i b l e t o m i n i m i z e p o s s i b l e i n b r e e d i n g and d r i f t e f f e c t s .  With t h e  e x c e p t i o n o f t h e seven-month p e r i o d p r e c e d i n g E x p e r i m e n t 1, f i s h o f t h e same r a c e were o c c a s i o n a l l y i n t e r c h a n g e d between a q u a r i a . Virgin  ? ? were o b t a i n e d b y a l l o w i n g about a dozen p r e g n a n t  drop young i n a w e l l - p l a n t e d 43 1 aquarium.  to  The mothers were removed  when s u f f i c i e n t numbers o f young appeared, u s u a l l y i n a month's t i m e . Males were removed when t h e i r sex became a p p a r e n t . B e f o r e a l l b e h a v i o u r a l r e c o r d i n g s , f i s h were g i v e n some t i m e t o become accustomed t o t h e t e s t s i t u a t i o n .  F i s h w h i c h d i d n o t r e m a i n calm  were l e f t u n t i l t h e y became s o , o r e l s e f i n a l l y r e j e c t e d .  "Calm" i s  d e f i n e d as swimming about i n a r e l a x e d f a s h i o n , n o t r e m a i n i n g m o t i o n l e s s w i t h r a p i d l y b e a t i n g p e c t o r a l f i n s , and n o t swimming e n e r g e t i c a l l y a t t h e s i d e s o f the aquarium.  W h i t e - c l o u d M o u n t a i n f i s h , T a n i c h t h y s albonubes  L i n , were u t i l i z e d as " d i t h e r f i s h " ( B a r l o w , 1968a) t o calm g u p p i e s i n several experiments. O n l y mature f i s h were used i n e x p e r i m e n t s . t o o b s e r v a t i o n s e s s i o n s on a g i v e n day.  F i s h were n e v e r f e d p r i o r  17 At t h e c o n c l u s i o n o f e x p e r i m e n t s 1, 3, 7, and 8 f i s h were  anesthe-  t i z e d i n MS 222 and were e i t h e r photographed f o r l a t e r measurement o r measured w i t h c a l i p e r s .  Males n o t p h o t o g r a p h e d were s k e t c h e d i n s t e n c i l e d  o u t l i n e s t o maintain a record o f markings.  A l l f i s h were r e t u r n e d t o  stock aquaria.  c.  Observational  set-ups  F i s h were observed vegetation.  i n three types o f c o n t a i n e r .  Food, w a t e r c o n d i t i o n s , t e m p e r a t u r e ,  the same as i n t h e s t o c k a q u a r i a .  Observation  None c o n t a i n e d  and p h o t o p e r i o d  were  c o n t a i n e r s always i n c l u d e d  some w a t e r i n w h i c h f i s h had l i v e d . 1.  N i n e a q u a r i a , h e r e a f t e r r e f e r r e d t o as t h e o b s e r v a t i o n a q u a r i a , were  employed i n s e v e r a l e x p e r i m e n t s .  Each h a d a volume o f 23 1 and d i m e n s i o n s  o f 41 cm x 21.5 cm x 26 cm deep. 2.  A n o t h e r aquarium, h e r e a f t e r r e f e r r e d t o as t h e l o n g aquarium, was  used f o r s e v e r a l t e s t s .  The volume was 22-1 and t h e d i m e n s i o n s were 61.5  cm x 17 cm x 21 cm deep. 3.  A three-way c h o i c e maze was c o n s t r u c t e d by Mr. C o l i n P a r k i n s o n o f t h e  Department o f Z o o l o g y workshop.  Top  F i g . 4.  Specifications:  I-  Three-way C h o i c e Maze  18 The maze was l i g h t e d by f o u r 40-watt f l u o r e s c e n t b u l b s 206 cm above t h e w a t e r and one 100-watt i n c a n d e s c e n t b u l b 82 cm above t h e w a t e r 4.  I o b s e r v e d f i s h i n t h e o b s e r v a t i o n a q u a r i a and t h e l o n g aquarium by  s i t t i n g q u i e t l y between 40 and 70 cm i n f r o n t o f them. were o b s e r v e d  F i s h i n t h e maze  from a d i s t a n c e o f a p p r o x i m a t e l y 130 cm above and t o one  side o f the apparatus.  D.  R e c o r d i n g and a n a l y z i n g i n s t r u m e n t s The major equipment employed i s l i s t e d h e r e and r e f e r r e d t o i n t h e  experimental sections. I p h o t o g r a p h e d f i s h f o r measurement w i t h a P e n t a x S p o t m a t i c 35 mm camera and Kodak H i g h Speed E k t a chrome Type B f i l m . An Olympus 35 mm camera, e s p e c i a l l y o u t f i t t e d f o r b u l k - l o a d i n g and t i m e d h a l f - f r a m e exposures p h o t o graphed f i s h on Kodak T r i - X Pan f i l m i n e x p e r i m e n t s 1 and 7. A Vanguard M o t i o n A n a l y z e r was used t o a n a l y z e f i l m o b t a i n e d i n e x p e r i m e n t s 1 and 7. Measurements were punched d i r e c t l y o n t o p e r f o r a t o r t a p e which was decoded i n an IBM 1130 computer. I b u i l t a k e y b o a r d w h i c h t r a n s f e r r e d my o b s e r v a t i o n s t o a computerized data a c q u i s i t i o n t e r m i n a l (herea f t e r r e f e r r e d t o as CDAT), b u i l t by Mr. Stephen Borden o f t h e B i o - S c i e n c e D a t a C e n t r e . As I o b s e r v e d f i s h , I p r e s s e d b u t t o n s c o r r e s p o n d i n g t o t h e i r beh a v i o u r p a t t e r n s and p o s i t i o n s . The machine r e c e i v e d t h i s i n f o r m a t i o n and punched i t on p e r f o r a t o r t a p e , which was l a t e r decoded by t h e IBM 1130. F r e q u e n c i e s , d u r a t i o n s , i n t e r v a l s , and sequences o f a c t i v i t i e s were t h e n a v a i l a b l e f o r p r i n t - o u t s and s t a t i s t i c a l analyses. A f o u r - c h a n n e l R u s t r a k event r e c o r d e r A P h i l l i p s c a s s e t t e tape r e c o r d e r  19  C h a p t e r 4.  A.  A Comparison o f Male C o u r t s h i p  Strategies  G e n e r a l I n t r o d u c t i o n and B e h a v i o u r P a t t e r n s  Described  My i n i t i a l g o a l was t o d e t e r m i n e whether o r n o t p o p u l a t i o n ences i n d" p a t t e r n s  differ-  and c o l o r a t i o n have any s i g n i f i c a n c e i n c o u r t s h i p .  I t soon became apparent t h a t d i f f e r e n c e s i n b e h a v i o u r were more i m p o r t a n t features t o observe. s i g n a l value  C o l o r p a t t e r n s have p r o b a b l y e v o l v e d  of behaviour patterns  t o enhance t h e  r a t h e r than the converse.  When one gazes i n t o an aquarium o f g u p p i e s , one cannot h e l p b u t be impressed by t h e seemingly i n c e s s a n t  a t t e n t i o n given t o  by  <t<t.  c o n v e n i e n c e , we may d i v i d e t h e d"'s c o u r t s h i p a c t i v i t i e s i n t o t h r e e  cate-  g o r i e s : o r i e n t a t i o n , c o n t a c t movements, and d i s p l a y ( L i l e y , 1966). O r i e n t a t i o n i s s i m p l y m a i n t a i n i n g v i s u a l and s p a t i a l b e a r i n g s u s u a l l y f a c i n g her.  C o n t a c t movements:  at t h e g e n i t a l pore o f a  1955)  a d" may t h r u s t h i s gonopodium  ?, b u t t h i s r a r e l y i n s e m i n a t e s h e r .  t o t i m e a d" d i s p l a y s t o a ? .  1966:  From time  When t h i s s i g m o i d d i s p l a y (Baerends et^ al_.  i s performed t o a r e c e p t i v e  ? , i t may e l i c i t a s e x u a l r e s p o n s e r e -  s u l t i n g i n c o p u l a t i o n , t h e normal mode o f sperm t r a n s f e r . a ?  on t h e ? ,  However, s i n c e  o n l y becomes r e c e p t i v e a t a p p r o x i m a t e l y three-week i n t e r v a l s ( L i l e y , 4 3 ) , most o f t h e d"'s d i s p l a y s j u s t l e a d t o more d"  courtship.  The  d i s p l a y , w h i c h l a s t s about two s e c o n d s , i s h i g h l y r i t u a l i z e d and i s emphas i z e d b y c h a n g i n g c o l o u r and m a r k i n g p a t t e r n s , s p r e a d i n g q u i v e r i n g , and r o c k i n g t o and f r o . sumedly t h e r e b y enhanced.  median f i n s ,  I t s e f f e c t i v e n e s s as a s i g n a l i s p r e -  O f a l l t h e d" • s c o u r t s h i p a c t i v i t i e s , t h e  For  20 d i s p l a y most o f t e n l e a d s t o c o p u l a t i o n . A number o f s t u d i e s o f guppy r e p r o d u c t i v e b e h a v i o u r have been r e p o r t e d i n the l i t e r a t u r e  (see L i l e y , 1966:  26-28).  Sexual  communication  appears t o be l a r g e l y v i s u a l , a l t h o u g h Amouriq (1964, 1965a, b , and and G a n d o l f i (1969) r e p o r t t h e p r e s e n c e o f o l f a c t o r y cues.  Liley  1967)  (1969)  f i n d s d i f f i c u l t y i n a t t a c h i n g i m p o r t a n c e t o a c h e m i c a l sex a t t r a c t a n t i n guppies.  F o r a d e t a i l e d d e s c r i p t i o n and a n a l y s i s o f guppy c o u r t s h i p r e f e r  t o L i l e y (1966),and Appendix  2).  The accompanying l i s t o f o*  b e h a v i o u r p a t t e r n s r e c o r d e d i n my  experi-  ments f o l l o w s L i l e y (1966) except where n o t e d . Orientating:  i n c l u d e s F o l l o w i n g , Watching, and Weak s i g m o i d s  Circling, Retreating,  Gonopodial swing: ( O c c a s i o n a l l y p e r f o r m e d when t h e courting).  <f was  not  S i g m o i d d i s p l a y : o n l y t h e f u l l y d e v e l o p e d d i s p l a y was r e c o r d e d The a d j e c t i v e s f r o n t a l and g e n e r a l were dropped i n f a v o r o f l o c a t i n g t h e d i s p l a y s by d e n o t i n g them as " i n f r o n t " i f t h e y were performed w i t h i n a twenty-degree a n g l e e x t e n d i n g h o r i z o n t a l l y f o r w a r d from a p o i n t between t h e ? *s e y e s , o r "not i n f r o n t " . The o b j e c t i o n t o " f r o n t a l " i s t h a t t h e t e r m i s used t o d e n o t e a t y p e o f d i s p l a y i n many f i s h e s and n o t i t s l o c a t i o n . Leap Thrust C o p u l a t i o n attempt and C o p u l a t i o n Jerk Snout c o n t a c t w i t h g e n i t a l pore o f £: t h i s b e h a v i o u r d i d not o c c u r i n the f i s h L i l e y s t u d i e d , even though he looked f o r i t . I t d i d o c c u r i n f r e q u e n t l y i n the p o p u l a t i o n s observed h e r e .  Chase:  a d* i n i t i a t e s a f l e e i n g r e s p o n s e by t h e ? , u s u a l l y by c o n t a c t w i t h h e r g e n i t a l r e g i o n , and pursues h e r .  N o n - c o u r t s h i p b e h a v i o u r a s s o c i a t e d w i t h c o u r t s h i p o c c u r r i n g between  dV:  Sparring Tail-beating Charge:  B.  a g g r e s s i o n which i n c l u d e s b i t e s a t another f i s h , a t t e m p t e d b i t e s , and c h a s i n g c u l m i n a t i n g i n a t t e m p t e d b i t e s . Few, i f any, b i t e s a c t u a l l y made c o n t a c t .  A d e s c r i p t i v e a n a l y s i s o f the courtship o f the three populations ( E x p e r i m e n t 1)  1.  Introduction The p u r p o s e o f t h i s s e t o f o b s e r v a t i o n s was t o d e t e r m i n e whether  t h e r e a r e d i f f e r e n c e s i n c o u r t s h i p between d V o f t h e P a r i a , Upper A r i p o , and Guayamare R i v e r s , and t o d e s c r i b e t h e n a t u r e o f t h e s e d i f f e r e n c e s . 2.  M a t e r i a l s and Methods A  ? and a <f  from one r a c e w h i c h had been r e s i d i n g i n s e p a r a t e  a q u a r i a were i n t r o d u c e d , a t about 0900 h o u r s , i n t o one s i d e o f an o b s e r v a t i o n aquarium w h i c h had been d i v i d e d i n h a l f (20 cm x 21.5 x 25 cm deep).  A t about 1700 hours a brown, opaque p l e x i g l a s p a r t i t i o n was  p l a c e d between t h e two f i s h , t h e n removed a t about 0900 hours t h e f o l l o w i n g morning.  O b s e r v a t i o n s commenced i f b o t h f i s h were calm.  I f the f i s h  were n o t c a l m , t h e y were l e f t t o g e t h e r u n t i l 1700 h o u r s , when t h e y were s e p a r a t e d u n t i l t h e n e x t morning. the  T h i s p r o c e d u r e was c o n t i n u e d u n t i l  f i s h met t h e b e h a v i o u r a l c r i t e r i a , which was u s u a l l y i n two o r t h r e e  days.  A few f i s h n e v e r calmed s u f f i c i e n t l y and were n o t used.  independent  Of 18  t r i a l s a t t e m p t e d f o r each r a c e , 13 P, 16 UA, and 17 G were  completed.  The s t a n d a r d l e n g t h s o f t h e f i s h o b s e r v e d a r e found i n  T a b l e 4. Each o b s e r v a t i o n p e r i o d l a s t e d 15 minutes and a l l t r i a l s were r e corded between 0900 and 1300 h o u r s ( l i g h t s on a t 0800 h r s . ) . A l l o f t h e c o u r t s h i p b e h a v i o u r l i s t e d i n C h a p t e r 4.A., a l o n g w i t h i n f o r m a t i o n on t h e r e l a t i v e p o s i t i o n o f t h e d w i t h CDAT.  t o the $  R e l a t i v e p o s i t i o n s r e c o r d e d were as f o l l o w s :  above o r below a  ? from t h e l e v e l  was r e c o r d e d A d  moved,  position.  JA&OVE  Fig. 5  R e l a t i v e p o s i t i o n s r e c o r d e d i n Experiment 1.  Occurrence o f a  d" w i t h i n a 2 cm  r a d i u s around t h e ? was a l s o n o t e d .  Two cm r e p r e s e n t s a p p r o x i m a t e l y one o* f i s h l e n g t h and was thus e a s i l y estimated.  E v e r y 15 seconds f o r t h e d u r a t i o n o f a t r i a l , t h e Olympus  camera photographed t h e o b s e r v a t i o n chamber and an o v e r h e a d m i r r o r , w h i c h a l l o w e d a view from t h e t o p . Measurements o f o r i e n t a t i o n and d i s p l a y d i s t a n c e s and a n g l e s were made on t h e m o t i o n a n a l y z e r .  U n f o r t u n a t e l y t h e camera f a i l e d  repeatedly  so t h a t o n l y about o n e - h a l f t h e t r i a l s were p h o t o g r a p h e d . The r a t i o n a l e f o r m e a s u r i n g s p a t i a l r e l a t i o n s h i p s and amount o f d movement t o v a r i o u s p o s i t i o n s r e l a t i v e t o t h e ?  i s as f o l l o w s .  Males  23  T a b l e 4.  Race  S t a n d a r d l e n g t h s o f f i s h o b s e r v e d i n E x p e r i m e n t 1.  dV mean(mm)  Range  Range mean(mm)  P  16.40  14.50-17.75  24.90  23.00-27.00  UA  16.40  15.25-19.25  25.30  22.50-29.00  G  15.75  13.75-19.75  26.18  22.50-30.25  24  who  changed p o s i t i o n more o f t e n would p r e s u m e d l y c a t c h t h e eye o f a  p r e d a t o r and a  ? more r e a d i l y than  G r e a t e r d i s t a n c e s from the  who  changed p o s i t i o n  ¥ might p l a c e  p r e d a t o r s might l i e i n w a i t .  o v e r deeper w a t e r where  Since the environments o f the p o p u l a t i o n s  d i f f e r i n b o t h number o f p r e d a t o r s and v i s i b i l i t y ,  I thought  might e x h i b i t a d a p t i v e d i f f e r e n c e s i n t h e i r u t i l i z a t i o n o f 3.  less.  t h a t the  dV  space.  Results Data was  f i r s t a n a l y z e d p a r a m e t r i c a l l y (one-way a n a l y s i s o f v a r i a n c e ) ,  but B a r t l e t t ' s t e s t i n d i c a t e d t h a t t h e v a r i a n c e s o f most o f t h e behav i o u r a l measures were p r o b a b l y not homogeneous. K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e was compare t h e p o p u l a t i o n s . a n a l y s i s o f v a r i a n c e was r a c e s was  The  non-parametric  t h e r e f o r e employed t o  On t h e p h o t o g r a p h i c d a t a , a p a r a m e t r i c one-way j u s t i f i e d and used.  done by K r u s k a l - W a l l i s s i m u l t a n e o u s  Comparisons o f p a i r s probabilities  of  i n the  one  c a s e , and S c h e f f e ' s t e s t f o r m u l t i p l e comparisons w i t h u n e q u a l sample s i z e i n the o t h e r case. a.  Orientation 1) Time spent  orientating  The t h r e e r a c e s d i f f e r e d i n p e r c e n t a g e  o f time i n t h e t r i a l  o r i e n t a t i n g and t h e l e n g t h o f each b o u t o f o r i e n t a t i o n . by G dV G  spent  Fewer d i s p l a y s  (see p a r t c) r e s u l t e d i n more and l o n g e r o r i e n t a t i o n p e r i o d s .  d V o r i e n t e d t o the  82% and UA o V  93% o f t h e t o t a l t r i a l t i m e , w h i l e P rfd" d i d so  , 85% o f t h e t i m e  o r i e n t a t i o n were: G, 51.1  (p = . 0 4 ) .  s e c o n d s ; P, 30.8  2  The mean bout l e n g t h s o f  s e c o n d s , UA,  36.2  seconds  —  A l l p r o b a b i l i t y v a l u e s a r i s e from the K r u s k a l - W a l l i s one-way a n a l y s i s of variance unless otherwise stated.  25 (p = .003).  Time and  d i f f e r between the  number o f times n o t  attending to the  from  ?  during  orientation  P h o t o g r a p h i c a n a l y s i s r e v e a l e d t h a t the mean d i s t a n c e ? d u r i n g o r i e n t a t i o n was  P and  not  races.  2) D i s t a n c e o f d  the  ? did  o f the  s i g n i f i c a n t l y l e s s i n the UA  than i n  G r a c e s ( p < . 0 0 1 , p a r a m e t r i c one-way a n a l y s i s o f v a r i a n c e ;  However, a d i f f e r e n t i m p r e s s i o n was  o* from  g a i n e d from l e s s p r e c i s e  Table  to a  ?  was  clear) . scored.  f i s h - l e n g t h of a ? and  Here the p r e s e n c e o f a <t w i t h i n one The  results  ( T a b l e 5b)  The  angles of d  a n g l e s a t which dd  An uncanny c o n s i s t e n c y o f  with respect to  oriented d  i n a l l races  to  who  4) Changes i n d  ?  (p =  .04)  their =  .0002).  $  %% were measured from the  was  recorded:  90°  film.  on e i t h e r  %  long side  showed g r e a t  averaged s l i g h t l y g r e a t e r a n g l e s below  s l i g h t l y exceeded G p o s i t i o n with  As s t a t e d e a r l i e r ,  the  dd.  respect to %  o V s p e n t most o f t h e i r t i m e o r i e n t a t i n g ,  changing p o s i t i o n r e l a t i v e t o the t i o n s above and  ^(p  a  (Table 6 ) .  v a r i a t i o n ( F i g . 6 ) , P dd dd  dd  moved w i t h i n  A n g l e s above and below the h o r i z o n t a l p l a n e o f the  t h a n d i d UA  fish-length  l o n g a x i s d i r e c t i o n i n r e l a t i o n t o the  a x i s i n the h o r i z o n t a l p l a n e o f the o f her  Once G dd  differ-  came w i t h i n  ?, t h e y remained t h e r e l o n g e r t h a n P o r UA  3) O r i e n t a t i o n  d  s i g n i f i c a n t l y l e s s o f t e n t h a n UA o r G  s p e n t l e s s time t h e r e (p = .001).  length of a  show P o V  5a).  data c o l -  l e c t e d on the d a t a a c q u i s i t i o n system (though the s o u r c e o f t h i s ence i s not  the  ? .  below the p l a n e o f the  When movement o f t h e  dd  are examined, r a c i a l  often to p o s i -  differences  26  T a b l e 5a.  Orientation distances .  Race  P  UA  G  Number o f f i s h  7  9  5  Number o f measurements  65  71  50  Mean d i s t a n c e  4.5  3.4  4.9  S.D. (cm)  2.6  1.9  2.3  Range (cm)  1.5-13.4  1.0-14.6  (cm)  1.4-11.1  One-way a n a l y s i s o f v a r i a n c e , p < . 0 0 1 .  T a b l e 5b.  O c c u r r e n c e o f f i s h w i t h i n one <f f i s h - l e n g t h 2 cm) o f each o t h e r .  Race n  (approx.  P  UA  G  KruskalW a l l i s oneway a n a l y s i s of variance  13  16  17  20.6  36.6  34.1  p = .04  p = .001  Mean number o f bouts Mean p e r c e n t a g e o f time  5.28  12.71  19.34  Mean bout length (sec)  2.12  2.77  5.61  p = .0002  T a b l e 6.  Race  A n g l e o f d" l o n g a x i s t o l o n g h o r i z o n t a l a x i s o f ? while orientating .  No. o f fish  No. o f Measures  Mean a n g l e (right or left)  S.D.  P  7  65  91.0  10.1  UA  9  71  89.5  2.9  C  5  50  90.1  1.6  One-way a n a l y s i s o f v a r i a n c e , p-**. 1.  28  F i g . 6.  Mean a n g l e s o f o r i e n t a t i o n by </c/ w i t h r e s p e c t  t o the  h o r i z o n t a l plane of the ? .  A n g l e s were t h e same on b o t h t h e  l e f t and r i g h t s i d e s o f t h e  The wedges c l o s e s t t o t h e ?  represent  standard  of variance chance.  d e v i a t i o n s around t h e mean.  One-way  analys  i n d i c a t e d that p >.l that the d i f f e r e n c e s arose by  28a  [ /  \  / / /  / /  /  \ '  j  \  1  v A \ \  29 become a p p a r e n t : ( F i g . 7 a ) . G <i<£ moved t o p o s i t i o n s below t h e ?  less  o f t e n (p = .04) and remained t h e r e f o r t h e s m a l l e s t p e r c e n t a g e o f time (p = . 1 ) . P d V tended t o spend a g r e a t e r p e r c e n t a g e o f t i m e b o t h above and below t h e ? t h a n o t h e r d V  ( F i g . 7 b ) . B e s i d e s moving above t h e  l e s s o f t e n and f o r l e s s time (p = . 0 1 ) , UA  d V ' mean bout l e n g t h i n t h a t  p o s i t i o n was a l s o s h o r t e r (p = . 0 3 ) . Mean bout l e n g t h below t h e ? d i d not d i f f e r between t h e r a c e s ( F i g . 7 c ) . The t i m e s above and below do n o t t o t a l 100% because d"d* were o f t e n l e v e l w i t h t h e  ? ; i . e . , some p a r t  o f t h e d " % body l a y w i t h i n two h o r i z o n t a l p l a n e s e x t e n d i n g from t h e ? 's most d o r s a l and most v e n t r a l body p a r t s ( F i g . 5 ) . The p r o b a b i l i t i e s o f d i f f e r e n c e s between t h e r a c e s i n b e i n g i n a p o s i t i o n w i t h i n a 20° h o r i z o n t a l a n g l e d i r e c t l y i n f r o n t o f t h e ? i s slight  ( F i g . 7a, b, c ) .  O v e r a l l t h e r e was an i n d i c a t i o n t h a t P and UA more t h a n G d V w h i l e o r i e n t a t i n g  <^d" moved around t h e  (mean p o s i t i o n changes i n t r i a l :  P,  69.5; UA, 68.6; G, 6 3 . 1 ) . b.  C o n t a c t movements The f r e q u e n c y o f t h r u s t s d i d n o t d i f f e r s i g n i f i c a n t l y between r a c e s  i n this experimental s i t u a t i o n  (P = 1.3, UA = .6, G = 1.0; p > . 5 ) .  few c o p u l a t i o n a t t e m p t s o c c u r r e d b e c a u s e a l l b u t e i g h t 4 G) were u n r e c e p t i v e .  Very  (3 P, 1 UA,  There was a s u g g e s t i o n t h a t s n o u t c o n t a c t w i t h  t h e ?.'s g e n i t a l p o r e , though i n f r e q u e n t , o c c u r r e d more o f t e n i n UA d V t h a n o t h e r s (P = 1.7, UA = 3.1, G = 2.2; p < . 3 ) . c.  Display The d i s t a n c e from t h e %  a t which the c/d"  performed  sigmoid d i s p l a y s  was a p p r o x i m a t e l y f i v e cm and d i d n o t d i f f e r between t h e r a c e s ( T a b l e 7 ) .  30  F i g . 7. of a ? .  O c c u r r e n c e o f d<£ i n p o s i t i o n s  above, below, and i n f r o n t  N = 13 f o r P, 16 f o r UA, and 17 f o r G.  are d e r i v e d f r o m t h e K r u s k a l - W a l l i s  P r o b a b i l i t y values  one-way a n a l y s i s  a.  Mean number o f t i m e s o V  b.  Mean p e r c e n t a g e o f t i m e c/V s p e n t i n d i f f e r e n t  c.  Mean l e n g t h o f t i m e  moved i n t o d i f f e r e n t  of variance.  positions, positions,  o V spent i n d i f f e r e n t p o s i t i o n s .  N = 11  f o r P, 13 f o r UA, and 11 f o r G i n t h e p o s i t i o n below t h e ? .  30a  .02  35 30 25  u > o <  20 15  CO  Ui  x:  10  o  5  03  hi e»  S3 »  0  55 55 Ui  o •J  UA  P > .4  5  Ui  10 P = .04  0 IN  5 FRONT  10  30b  14  P =  .01  12  10  w  w > o  r5 6  X  In O  4  w a  <  2  H SS  Ui  o 05 (4 OH  0  UA  P >  SS •<  w as  O  •J  .8  2  Ui  4  P = .1 0  i  2  i  IN FRONT  b .  4  i >  MEAN LENGTH OF TINE ( S E C ) BELOW  ABOVE  ro  O  v 'ro  O  2 H  cn  TJ  TJ  » o  to  C  II  >  o  31  G d'd" d i s p l a y e d  l e s s f r e q u e n t l y and f o r l e s s t i m e when a l l r a c e s are  compared (p = .02 and relative to  .04 r e s p e c t i v e l y , F i g . 8 ) .  ?  l o n g e r and more o f t e n  UA and G d'd", and UA 2 cm) o f t h e  in position  d u r i n g d i s p l a y o c c u r r e d n o t j u s t because o f v a r i a t i o n i n  t o t a l d i s p l a y a c t i v i t i e s between the r a c e s . above t h e  Difference  dV  F o r i n s t a n c e , P <JV  (p = .0002 and  displayed  .001, r e s p e c t i v e l y )  than  displayed w i t h i n a f i s h - l e n g t h (approximately  ? more o f t e n and f o r l o n g e r t i m e s (p = .0009 and  r e s p e c t i v e l y ) t h a n P and G dV.  .0008,  O t h e r d i f f e r e n c e s between r a c e s i n l o -  c a t i o n o f d i s p l a y more c l o s e l y f o l l o w e d t h e o v e r a l l d i f f e r e n c e s i n b o u t s and p e r c e n t a g e time o f d i s p l a y mentioned  above and i n F i g . 8 ( F i g . 9 a , b ) ,  The average number o f changes i n d i s p l a y p o s i t i o n (above, below, inside or outside 28.2  f o r P dV  one f i s h - l e n g t h ) d u r i n g a t r i a l was  and 27.9  f o r UA  7.7  level;  f o r G tfd",  d'd, b u t t h e number o f p o s i t i o n changes 1  p e r d i s p l a y d i d n o t d i f f e r (P, 2; UA,  1.8; G, 1.8).  I consider  t h e num-  b e r o f p o s i t i o n changes i n a t i m e p e r i o d t h e most e c o l o g i c a l l y r e l e v a n t measure because the amount o f m o t i o n complements r a c i a l d i f f e r e n c e s i n the v e r y o b v i o u s d i s p l a y b e h a v i o u r and t h e r e b y enhances r a c i a l in  differences  conspicuousness. I f we examine d i s p l a y times i n v a r i o u s p o s i t i o n s as a p r o p o r t i o n  of  t o t a l d i s p l a y times f o r each r a c e s e p a r a t e l y , we f i n d G d'd" i n f r o n t o f the  ? more o f t e n  (32%) t h a n P and UA d'd"  P d'd" remained above most and UA  (20% and 14%, r e s p e c t i v e l y ) .  d'd" remained w i t h i n a f i s h - l e n g t h most  (Fig. 9c). W h i l e r e l a t i v e p o s i t i o n s o f two f i s h n e c e s s a r i l y depends upon b o t h o f t h e i r movements, I b e l i e v e t h a t the d i f f e r e n c e s found h e r e are due d i f f e r e n c e s i n t h e d'd*  r a t h e r than a r e f l e c t i o n o f ?  response  to  patterns.  T a b l e 7.  Display  Distances  Race  n  distance (cm)  P  8  4.5  1-13  14  5.3  2-15  6  5.2  3-8  UA G  Range (cm)  One d i s p l a y ( t h e f i r s t c l e a r l y measurable on t h e f i l m ) was measured f o r each f i s h .  33  F i g . 8.  A comparison o f mean number o f b o u t s o f s i g m o i d d i s p l a y s  and mean p e r c e n t a g e o f time i n t h e t r i a l spent d i s p l a y i n g b y dV of three races o f guppies. variance.  Kruskal-Wallis  one-way a n a l y s i s o f  °/o CN  T I M E  T R I A L  CM  oo CN  O F  CM  00  <N  o II  O ii  CN  CN  00  S i  no8  34  F i g . 9.  Schematic r e p r e s e n t a t i o n  r e l a t i v e to a  ?  .  The  of  <? d i s p l a y s i n v a r i o u s  f i s h represents a  ? , the d o t t e d  p r e s e n t s a 2 cm c y l i n d e r w i t h i t s a x i s h o r i z o n t a l and the f i s h ' s l o n g a x i s . rence o f P, UA,  and  r e l a t i v e t o the  $ :  ?.  circle  G oV  ( i n that order) d i s p l a y i n g i n various  above, b e l o w , l e v e l , i n f r o n t , and ?  .  with  occurpositions  i n s i d e or out-  L e v e l d i s p l a y s o c c u r r e d on b o t h  P r o b a b i l i t y v a l u e s from the K r u s k a l - W a l l i s  analysis of variance  re-  coincident  Each group o f h i s t o g r a m s r e p r e s e n t s the  s i d e a p p r o x i m a t e l y 2 cm o f the s i d e s o f the  positions  one-way  are i n s e r t e d where a d i f f e r e n c e between r a c e s  exists.  a.  Number o f times  r e l a t i v e to a  b.  <f<?  Percentage of time i n t r i a l oV  Percentage of time  r e l a t i v e to a  positions  ?.  p o s i t i o n s r e l a t i v e to a  c.  were found d i s p l a y i n g i n v a r i o u s  were f o u n d d i s p l a y i n g i n  various  $,  <f<? were found d i s p l a y i n g i n v a r i o u s  positions  ? , e x p r e s s e d as p e r c e n t a g e s o f t o t a l d i s p l a y t i m e f o r  each r a c e ( i . e . , each r a c e d i s p l a y e d  100%).  34a  P = .001  54  a.  34b  34c  C .  35 F i s h d i d not d i f f e r i n mean number o f g o n o p o d i a l swings (P = 4.6 p e r t r i a l , UA = 4.2, G = 5.0; p > . 8 ) , o r l e a p s (P = .8, UA = .8, G = .5, p > 8 ) .  d.  C o r r e l a t i o n s o f behaviours C o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d between a l l r e c o r d e d  o f c o u r t s h i p , between ?  <S c o u r t s h i p and  l e n g t h and a l l a s p e c t s o f  s p a t i a l r e l a t i o n s , and between s h i p and s p a t i a l r e l a t i o n s .  aspects  <f l e n g t h and a l l a s p e c t s o f h i s c o u r t -  The o n l y s i g n i f i c a n t r e l a t i o n o b t a i n e d was  a s t r o n g p o s i t i v e c o r r e l a t i o n between numbers o f d i s p l a y s and l e a p s i n G  (R = .82, p < . 0 0 0 1 ) .  I know from p e r s o n a l o b s e r v a t i o n s t h a t l e a p s  are always p r e c e d e d by d i s p l a y s - - P and UA  d'd* d i d n o t l e a p enough t o  yield significant correlation coefficients. the d" o r $  Apparently the s i z e o f e i t h e r  f i s h had no b e a r i n g on d* c o u r t s h i p a c t i v i t y i n t h i s  situa-  tion.  C.  T h r e s h o l d d i s t a n c e s f o r c o u r t s h i p (Experiment  1.  Introduction T h i s experiment  was u n d e r t a k e n  Experiment 1 was completed.  2)  before the photographic  analysis of  Because o f t h e g r e a t e r t u r b i d i t y and h i g h e r  degree o f p r e d a t i o n i n t h e Guayamare R i v e r I h y p o t h e s i z e d t h a t P and UA d'd"  would d i s p l a y a t g r e a t e r d i s t a n c e s from t h e $  experiment  d'd* .  The  t h e r e f o r e was d e s i g n e d t o compare t h e c o u r t s h i p o f t h e d'd o f 1  the t h r e e r a c e s when p r e v e n t e d tances t o  than G  .  from a p p r o a c h i n g  Furthermore,having  nearer than c e r t a i n  dis-  shown t h e d i s c r e p a n c y i n d i s p l a y f r e -  q u e n c i e s between t h e r a c e s i n t h e p r e v i o u s e x p e r i m e n t ,  I hypothesized  that  36  P and UA  dd would a l s o d i s p l a y more f r e q u e n t l y and w i t h s h o r t e r  l a t e n c i e s than G  2.  dd .  M a t e r i a l s and Methods Three  o f t h e same s i z e (24.2 +_ .1 mm), one o f each r a c e , were  p l a c e d i n t h e l o n g aquarium as shown i n F i g . 10. chosen f o r calmness.  Eight  These  ? ? were  dd o f each r a c e were i n d i v i d u a l l y  the same day. The f o l l o w i n g day,  isolated  s i x dd. o f each r a c e were t e s t e d t h r e e  times each w i t h t h r e e d i f f e r e n t minimum d i s t a n c e s from t h e ? ? --0, 5, and  10 c m — d e t e r m i n e d b y i n s e r t i o n o f c l e a r p l e x i g l a s p a r t i t i o n s ( F i g .  10). Males were o b s e r v e d i n an o r d e r  ( P , G, UA) so t h a t t h e y had a p p r o x i -  m a t e l y e q u a l i s o l a t i o n p e r i o d s between t r i a l s . was  The o r d e r i n w h i c h a d^  t e s t e d a t t h e minimum d i s t a n c e s was d e t e r m i n e d b y chance.  Dither  fish  swam i n an aquarium b e h i n d t h e l o n g aquarium ( F i g . 1 0 ) . I recorded  t h e f o l l o w i n g : t i m e u n t i l f i r s t d i s p l a y , number o f d i s -  plays, display distances whether o r n o t t h e d  (+1 cm, d i s t a n c e s marked on aquarium) and  ever attended  to the %  during the t e s t ,  Attentive-  ness was d e f i n e d as d o r i e n t a t i o n and approach t o t h e ? ? , 3.  Results When  dd were p l a c e d i n t h e l o n g aquarium t h e y g e n e r a l l y began  attending to the One  immediately  i f t h e y were g o i n g t o a t t e n d a t a l l .  UA d d i d n o t behave c a l m l y enough on h i s f i r s t t r i a l and was r e p l a c e d , C o n t r a r y t o e x p e c t a t i o n , no f i s h , w i t h t h e e x c e p t i o n o f one P o* ,  d i s p l a y e d w i t h t h e 5 and 10 cm p a r t i t i o n s i n p l a c e . the f i s h d i s p l a y e d o n l y w h i l e v e r y c l o s e t o t h e  T h i s was n o t because , because  virtually  37  F i g . 10.  Aquarium s e t - u p f o r Experiment  2, t o p v i e w .  Three  •  e n c l o s e d i n a 5 cm wide s e c t i o n bounded by opaque p l e x i g l a s on one s i d e and c l e a r p l e x i g l a s on t h e s i d e o f t h e swim f r e e l y t h r o u g h o u t most o f the aquarium 2 mm o f t h e  <f  .  The  could  (approaching to w i t h i n  *"?) h u t c o u l d be l i m i t e d i n h i s most p r o x i m a l  approach  t o the ? ? by a c l e a r p l e x i g l a s p a r t i t i o n p l a c e d a t e i t h e r 5 o r 10 cm from t h e  i  ? ? * s p a r t i t i o n ( p o s i t i o n s shown by d o t t e d l i n e s ) .  DITHER FISH  ^ \ r  \  /  ' .  rf  n  T  1  P  I  !'!  P %%  \ ***  V  1 1  *  1  1  1 1<£ TE ST • — - -VJ  fcw  •  1  1  1  •*  38 a l l t h e f i s h d i s p l a y e d between 4 and 7 cm from them as i n Experiment 1 (Table 7 ) .  The apparent r e a s o n f o r t h i s b e h a v i o u r  i s t h a t t h e d"  must f i r s t come v e r y c l o s e t o t h e ? b e f o r e i n i t i a t i n g t h e d i s p l a y . Almost a l l d i s p l a y s were p r e c e d e d by t h e <? and ? o n l y by t h e t h i c k n e s s o f t h e p l e x i g l a s p a r t i t i o n  being  separated  (3 mm), w i t h t h e <t  backing o f f t o perform. Fig. plays.  11 shows times u n t i l f i r s t d i s p l a y s and f r e q u e n c i e s o f d i s The K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e r e f l e c t s t h e  d i f f e r e n c e s between a l l t h r e e r a c e s i n t i m e u n t i l t h e f i r s t d i s p l a y (p<.009).  P and UA  d'd" d i s p l a y e d most f r e q u e n t l y ( f o r b o t h P-G and  UA-G c o m p a r i s o n s , p = .004, Mann-Whitney U t e s t , o n e - t a i l e d ) and w i t h a s h o r t e r l a t e n c y t o t h e f i r s t d i s p l a y (P-G, p = .067; UA-G, p - .047; Mann-Whitney U t e s t , o n e - t a i l e d ) . P  UA  d'd took l o n g e r t o d i s p l a y t h a n 1  d V (p = .064, Mann-Whitney U t e s t , t w o - t a i l e d ) . At t h e two g r e a t e r d i s t a n c e s G d'd" p a i d l e s s a t t e n t i o n t o t h e  than d i d other  d'd*. I n 1/12 cases w i t h UA, 3/12 w i t h P, and 7/12 w i t h  G, t h e d* d i d n o t a t t e n d t o t h e  a t a l l during the five-minute t r i a l s  w i t h t h e p a r t i t i o n s 5 o r 10 cm from t h e ? ? .  E x p e c t e d f r e q u e n c i e s were 2  too low i n t o o many c e l l s t o compare t h e r a c e s w i t h t h e X a comparison o f each p a i r o f r a c e s w i t h t h e F i s h e r e x a c t  t e s t , but probability  t e s t y i e l d e d a t w o - t a i l e d p r o b a b i l i t y v a l u e o f .05 f o r t h e d i s c r e p a n c y between UA and G d'd" t o o c c u r by chance.  My i m p r e s s i o n was t h a t most o f  the G d'd" n o t a t t e n d i n g d i d not n o t i c e t h e  .  39  Fig. 11. Mean times until f i r s t display and mean number of bouts of display at the shortest distance (0 cm) from the ?? . Probab i l i t y values are from the Kruskal-Wallis one-way analysis of variance.  The dots are the data points.  statistical comparisons.  See text for further  TIME 0  •  O  I  I  •  TJ  FIRST  M N> O  CO  O •  1  UNTIL  I  I  M  O  \  M O O  IS> © O  0\  I  D I S P L A Y (sec)  I  I  I  I  4  •  C >  o '  A  O  K>  In)  *•  U>  ON  s i noa  C D  40 D.  C o m p e t i t i o n i n c o u r t s h i p I (Experiment  1.  Introduction  3)  Because o f the s o c i a l n a t u r e o f g u p p i e s , a  d p r o b a b l y would have  ??  ing  Does the manner and amount o f c o u r t s h i p  q u e s t i o n s may  be posed:  change i n the p r e s e n c e tition?  i n t h e absence o f o t h e r  dd..  l i t t l e opportunity to court  o f another  d  o f t h e same r a c e ?  The  follow-  Is t h e r e compe-  Are t h e d i f f e r e n c e s between the r a c e s r e t a i n e d i n a c o m p e t i t i v e  situation?  T h i s experiment  was  d e s i g n e d t o b e g i n t o answer t h e s e  questions.  2.  M a t e r i a l s and Methods One  ?  and two dd  between 1400 ing,  o f one r a c e were p l a c e d i n an o b s e r v a t i o n aquarium  and 1800 h o u r s .  u s u a l l y between 1000  and 1300 h o u r s .  A R u s t r a k event r e c o r d e r was ^  O b s e r v a t i o n s took p l a c e the f o l l o w i n g mornEach t r i a l  l a s t e d t e n minutes.  employed t o c h a r t t h e d u r a t i o n o f t i m e each  was c o u r t i n g . A l t h o u g h 18 independent  t r i a l s were attempted  f o r each r a c e , f i s h  which d i d n o t behave c a l m l y enough reduced the number o f t r i a l s to  3.  15 P, 13 UA,  and 15  analyzed  G.  Results A l t h o u g h one o f t h e p a i r o f  t h i r d s o f the time both  dd  dd c o u r t e d an average o f n e a r l y two-  c o u r t e d , t h e r e i s no r e a s o n t o b e l i e v e t h a t  t h e r e s u l t s r e f l e c t any d i f f e r e n c e s i n c o u r t s h i p t i m e between any o f t h e r a c e s  (one-way a n a l y s i s o f v a r i a n c e ; F i g . 12a).  dd  within  However,  41  Fig.  12.  C o u r t s h i p o f two  dV  i n t h e p r e s e n c e o f one $ ,  e x p r e s s e d as p e r c e n t a g e s o f t o t a l c o u r t s h i p ( d l + d"2) and time i n t h e t r i a l  (b.).  The h o r i z o n t a l l i n e s r e p r e s e n t  the mean v a l u e s f o r 15 P, 13 UA, are  and 15 G  d'd".  The  t h e 5% c o n f i d e n c e l i m i t s and t h e v e r t i c a l l i n e s  ranges.  (a.)  rectangl are the  100  r  100 80  90 80 J UA  70 UA  60 50  COURTSHIP OF o* WHO COURTED MORE  a.  COURTSHIP OF WHO COURTED MORE (TOP) COURTSHIP OF o" WHO COURTED LESS (BOTTOM)  42  r a c i a l d i f f e r e n c e s appeared i n the t i m e s p e n t i n c o u r t s h i p by the who  P dV  c o u r t e d more  c o u r t e d most (p = .05;  F i g . 12b).  c o u r t s h i p t i m e (d# 1 p l u s <f#2 ) t e n d e d t o be h i g h e r The  13).  There were no grounds f o r e x p e c t i n g  b a s i s of f i n d i n g s i n Experiment  for P d V  (p =  amount o f c o u r t s h i p . d* n o r  ?  length.  races  t h e s e r e s u l t s on  the  f o r length of a l l f i s h  Male c o u r t s h i p t i m e was  correlated with  with  neither  These f i n d i n g s do not n e c e s s a r i l y c o n t r a d i c t t h o s e o f  Baerends et^ al_. ( 1 9 5 5 ) , who a choice.  .08).  1.  C o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d  found t h a t d'd"  courted  My r e s u l t s show t h a t the l e n g t h o f ?  o f f e r e d (20-28 mm d'd"  Total  time spent i n s i m u l t a n e o u s c o u r t s h i p d i d not d i f f e r between  (Fig.  d"  S.L.)  had no c h o i c e .  larger  ?? i f given  i n the s i z e r a n g e  d i d not e f f e c t the amount o f c o u r t s h i p when the  T h i s f i n d i n g a l l o w s me  t o assume t h a t ? ?  of  differ-  ent s i z e s i n t h e one- ? e x p e r i m e n t s do not have d i f f e r e n t s t i m u l a t o r y properties. The  r e s u l t s and  impressions  from t h e s e o b s e r v a t i o n s  some mechanisms a r e i n o p e r a t i o n w h i c h d e t e r m i n e w h i c h opportunity  E.  d'd* get t h e most  t o mate.  P i l o t e x p e r i m e n t s on the r o l e ofd*—d* a g g r e s s i o n (Experiments 4, 5, and  1.  suggest t h a t  during  courtship  6)  Introduction O b s e r v a t i o n s i n E x p e r i m e n t 3 and d a i l y checks o f t h e s t o c k  a t the o n s e t o f t h i s s t u d y s u g g e s t e d t h a t P a r i a f i s h engaged i n able aggressive  a c t i v i t y , something which was  aquaria consider-  n o t i c e a b l y absent i n the  43  F i g . 13.  C o u r t s h i p o f t w o o V w i t h one ? , e x p r e s s e d  i n seconds.  The h o r i z o n t a l l i n e s r e p r e s e n t mean v a l u e s f o r 15 p a i r s o f P, 13 p a i r s o f UA, and 15 p a i r s o f G o V . confidence  The r e c t a n g l e s a r e t h e 5%  l i m i t s and t h e v e r t i c a l l i n e s a r e t h e r a n g e s .  a n a l y s i s o f variance y i e l d e d the p r o b a b i l i t y values.  One-way  P =.08 10  9 8  7 6 5 4 3 2 1  u  P < .0 5  UN  0 TOTAL COURTSHIP  SIMULTANEOUS COURTSHIP  NO COURTSHIP  44 other races.  For a c o n t r o l l e d check on d i f f e r e n c e s i n a g g r e s s i o n  and f o r some c l u e s as t o i t s f u n c t i o n a l s i g n i f i c a n c e and r e l a t i o n t o c o u r t s h i p , t h e f o l l o w i n g experiments 2.  A g g r e s s i o n and t e r r i t o r y  a.  Introduction T h i s experiment  were p e r f o r m e d .  (Experiment  4)  was p e r f o r m e d t o i n v e s t i g a t e t h e d i f f e r e n c e s i n  a g g r e s s i o n between P a r i a and t h e o t h e r two r a c e s , and t h e p o s s i b l e defence  o f t e r r i t o r i e s o r f o r m a t i o n o f dominance h i e r a r c h i e s .  d a t a suggest  (Field  the p o s s i b i l i t y o f t e r r i t o r i e s i n t h e P a r i a s t r e a m - S e g h e r s ,  p e r s . comm.) b.  M a t e r i a l s and Methods Each o f t h r e e o b s e r v a t i o n a q u a r i a were a r r a n g e d w i t h t h r e e r o c k s i n  a l i n e p a r a l l e l t o t h e f r o n t o f t h e aquarium, a p p r o x i m a t e l y midway between f r o n t and b a c k , and e q u i d i s t a n t from one a n o t h e r and t h e s i d e s . The r o c k s were p r o v i d e d as r e f e r e n c e p o i n t s s h o u l d a f i s h w i s h t o establish a territory.  S i x dV  f r o m each o f t h e t h r e e r a c e s were p l a c e d  s e p a r a t e l y i n each o f t h r e e o b s e r v a t i o n a q u a r i a . recognizable.  A f t e r s i x days f i s h were o b s e r v e d  F i s h were i n d i v i d u a l l y f o r ten-minute  O b s e r v a t i o n s were r e p e a t e d a f t e r seven and n i n e days. f r o n t o f t h e aquarium and t a l l i e d charges  periods.  I sat quietly i n  and n o t e d s p a r r i n g and t a i l -  beating. c.  Results Fig.  14 shows s c o r e s f o r each o f t h e t h r e e days the f i s h were  C l e a r l y , P d'd" were more a g g r e s s i v e than UA and G  d'd".  The t o t a l  observed. scores  45 were n o t a r e s u l t o f t h e a c t i v i t y o f a l l t h e f i s h , however. cases one o r two f i s h d i d a l l t h e c h a r g i n g .  I n most  I f o u n d no e v i d e n c e o f a  dominance h i e r a r c h y . The o n l y t e r r i t o r y formed was by a P a r i a f i s h - - t h a t i s , he always was found i n t h e same p l a c e and always r e t u r n e d t o i t a f t e r another f i s h . ill.  chasing  T h i s f i s h had a p e c u l i a r w o b b l e , b u t was n o t o b v i o u s l y  L a t e r o b s e r v a t i o n s have shown t h i s a s s o c i a t i o n - - w o b b l e ,  t e n a c i t y , and a g g r e s s i o n - - t o o c c u r o c c a s i o n a l l y i n b o t h Pdd  site and ? ? .  These f i s h d i d n o t d i e and u s u a l l y resumed normal swimming when r e p l a c e d i n t o stock aquaria.  I have a l s o observed  impermanent c o n d i t i o n i n s t o c k a q u a r i a . behaviour  t h i s wobble as an o c c a s i o n a l I have no e x p l a n a t i o n o f t h i s  and I d i d n o t p u r s u e t h e p r o b l e m because i t d i d n o t seem t o  have b e a r i n g on c o u r t s h i p . Observations  were t e r m i n a t e d due t o an i n c r e a s i n g c o n f u s i o n between  a g g r e s s i v e and s e x u a l b e h a v i o u r .  I n i t i a l l y , s p a r r i n g and c h a s i n g were  c l e a r l y aggressive.  assumed p o s i t i o n s p a r a l l e l o r a n t i -  S p a r r i n g dd  p a r a l l e l t o one a n o t h e r and chases were u s u a l l y t e r m i n a t e d by a b i t e attempt and no f u r t h e r p u r s u i t by t h e a g g r e s s o r .  L a t e r , chases p e r s i s t e d  and a t t e n t i o n was d i r e c t e d a t t h e g e n i t a l r e g i o n o f t h e o t h e r a d d i t i o n , s i g m o i d d i s p l a y s were a l s o p e r f o r m e d .  In  I t i s p o s s i b l e that the  s i g m o i d d i s p l a y has some appeasement f u n c t i o n , as t h e d forms i t t o t h e much l a r g e r  d .  u s u a l l y per-  ? , who o c c a s i o n a l l y charges (see a l s o  Appendix 1 r e g a r d i n g t h e p o s s i b l e f u n c t i o n s o f b l a c k c o l o r a t i o n i n dd When  ? ? were i n t r o d u c e d t o t h e s e  p e r s i s t e d i n c o u r t i n g other  dd  a f t e r day 9, a few dd  dd and a t t e m p t i n g c o p u l a t i o n w i t h them.  ).  46  F i g . 14.  Number o f charges by o V  p e r i o d s i n all-c»" a q u a r i a .  i n each o f t h r e e o b s e r v a t i o n  47 I interpret  this  as abnormal b e h a v i o u r  o f a p r o p e r sex o b j e c t i n an animal threshold f o r sexual  3.  Aggression  a.  Introduction  isolation that  (Experiment  response  5)  experiment and o b s e r v a t i o n s by L i l e y  from S?  low  ( dd r a i s e d i n  tend t o become homosexual; p e r s . comm.)  suggested  a r e a n e c e s s a r y p a r t o f the environment f o r t h e development o f  normal d of ?  w i t h an e x t r e m e l y  activity.  and females  The p r e v i o u s  r e s u l t i n g from the d e p r i v a t i o n  responses.  presence  on d  T h i s experiment was d e s i g n e d  t o t e s t the e f f e c t s  a g g r e s s i o n , and t h e p o s s i b i l i t y t h a t  s e r v e s as a mechanism o f c o m p e t i t i o n f o r  d  aggression  , as seen i n two s p e c i e s o f  the genus Gambusia (Warburton, Hubbs, and Hagen, 1957; M c A l i s t e r , 1958). b.  M a t e r i a l s and Methods The  o b s e r v a t i o n a q u a r i a were employed minus the r o c k s .  were used f o r each r a c e , and f i v e each.  dd  aquaria  from s t o c k a q u a r i a were p l a c e d i n  The n e x t day t h e y were s c o r e d f o r ten-minute p e r i o d s f o r aggres-  s i o n as i n t h e p r e v i o u s experiment. five  Two  At the c o n c l u s i o n o f o b s e r v a t i o n s ,  ? $ were added t o each aquarium, and s c o r i n g commenced  the end o f t h i s s e r i e s o f t e s t s , t h r e e o f t h e  on day 2.  At  were removed t o s t i m u -  l a t e a more h i g h l y c o m p e t i t i v e s i t u a t i o n f o r t h e dd , i f i n d e e d t h e y were competing f o r t h e ? ? .  c.  Results F i g . 15 shows t h a t the a d d i t i o n o f  i n c r e a s e d the t o t a l  amount o f  a g g r e s s i o n i n a l l r a c e s , w i t h the most a g g r e s s i o n by f a r o c c u r r i n g i n  48  Fig.  15.  same 5-d"  Mean number o f <f charges i n : (1) 5-<f g r o u p s , (2) t h e groups i n t o w h i c h 5 ? ?  were i n t r o d u c e d , and (3) t h e  same groups as i n (2) from w h i c h 3 ? ?  were removed.  Solid  i n d i c a t e s P g r o u p s , dashed l i n e , UA, and d o t t e d l i n e , G. groups f o r each r a c e .  line  N = 2  Cf C H A R G E S / T O  MIN  CO  49 Paria. ??  I n a d d i t i o n , one P ?  t w e l v e times and a  day 3.  defended a t e r r i t o r y and  d once on day 2, and charged dd  The r e d u c t i o n i n a g g r e s s i o n  f o l l o w i n g : (1) fewer ? ? (2) t h e dd  charged o t h e r f o u r times  on day 3 i m p l i e s one o r more o f t h e  meant the dd  were l e s s s t i m u l a t e d t o  fight,  had e s t a b l i s h e d more s t a b l e r e l a t i o n s h i p s , (3) the d e c r e a s e  i n a g g r e s s i o n was  4.  Aggression,  a.  Introduction  dependent upon the a d d i t i o n o f f i s h r e g a r d l e s s o f  females,  d a g g r e s s i o n was s i t y of f i s h .  sex.  and d e n s i t y (Experiment 6)  The p r e v i o u s e x p e r i m e n t posed the p r o b l e m o f whether the a f u n c t i o n o f the p r e s e n c e o f  The p r e s e n t  experiment was  o f the e f f e c t o f sex and d e n s i t y on b.  on  increased  ? ? o r j u s t a h i g h e r den-  designed  t o get an  indication  aggression.  M a t e r i a l s and Methods The manner o f s c o r i n g and the l e n g t h o f s c o r i n g p e r i o d s were as i n  the p r e v i o u s race. dd  The  experiment.  Three o b s e r v a t i o n a q u a r i a were u s e d f o r each  day b e f o r e the f i r s t t e s t two  each and one  aquarium r e c e i v e d f i v e  of these aquaria r e c e i v e d ??  .  A t t h e c o n c l u s i o n o f the  f i r s t s c o r i n g s e s s i o n , f i v e a d d i t i o n a l dd  were added t o one o f the  aquaria, f i v e ??  d  added t o the  ?  were added t o t h e o t h e r aquarium.  c o n t r o l s f o r d e n s i t y and ?  c.  The  all-d  1  five  d  aquarium, and f i v e ? ?  and the a l l - ?  t r i a l s were r u n  were as  r o l e s i n aggression.  Results The  only aggressive  a c t s on day  1 were i n a l l - d "  n o t e w o r t h y i n c r e a s e i n a g g r e s s i o n on day 2 o c c u r r e d  P aquaria. where  The  only  ? ? were added  50  to P dd  ( F i g . 1 6 ) . These r e s u l t s suggest t h a t  a g g r e s s i o n among P dd  f i s h may s t i m u l a t e  , and t h a t i n c r e a s e d d e n s i t y a l o n e may n o t be t h e  p r i m a r y cause o f a g g r e s s i v e i n t e r a c t i o n s . F.  C o m p e t i t i o n i n c o u r t s h i p I I (Experiment 7)  1. I n t r o d u c t i o n To f u r t h e r i n v e s t i g a t e mechanisms o f c o m p e t i t i o n I undertook  a  d e t a i l e d a n a l y s i s o f how a d e s t a b l i s h e d h i m s e l f as t h e dominant s u i t o r , i f he i n d e e d d i d s o . T h i s a n a l y s i s was much s t r e n g t h e n e d by u s i n g t h e dd  o f Experiment  1, who h a d some p r e v i o u s c o u r t s h i p r e c o r d e d .  sis  o f changes i n c o u r t s h i p b e h a v i o u r was t h e r e b y p o s s i b l e .  2.  M a t e r i a l s and Methods F i s h were i s o l a t e d i n each o b s e r v a t i o n aquarium  i n Experiment  1, a t about 1700 h o u r s .  An a n a l y -  after observation  Between 1250 and 1600 h o u r s t h e  f o l l o w i n g a f t e r n o o n , t h e c e n t e r p a r t i t i o n was removed and b o t h dd one o f t h e ? ? immediately.  were a l l o w e d i n t h e c e n t e r s e c t i o n . Each t r i a l  l a s t e d t e n minutes.  and  R e c o r d i n g commenced  N i n e independent  trials  were a t t e m p t e d f o r each r a c e , and 9 P, 8 UA, and 8 G were completed. following  d  b e h a v i o u r s were r e c o r d e d on t h e CDAT: d i s p l a y , l e a p , t h r u s t ,  c h a r g e , charge by t h e ? , c h a s e , and amount o f time each 2 cm o f t h e  The  % .  d spent w i t h i n  S p a r r i n g and any u n u s u a l a s p e c t s o f a t r i a l were n o t e d .  The Olympus camera s h o t a frame e v e r y 15 s e c o n d s , b u t due t o i t s i n c e s s a n t m a l f u n c t i o n i n g , o n l y 5 P, 4 UA, and 3 G t r i a l s y i e l d e d photographs for  analysis.  suitable  51  Fig.  16.  Number o f <t charges i n groups o f 5 f i s h o f one s e x , and  t h e s e same groups a f t e r 5 a d d i t i o n a l f i s h o f e i t h e r t h e same o r o p p o s i t e s e x were i n t r o d u c e d . are shown.  O n l y groups where c h a r g e s o c c u r r e d  S o l i d l i n e s i n d i c a t e P g r o u p s ; dashed l i n e , UA.  51a  D A Y  1  D  A  Y  2  52  3.  Results. Changes i n c o u r t s h i p from t h e l d * - l ?  w i t h i n each r a c e i n t h i s 2  Experiment  dd - 1 ? s i t u a t i o n  d i s p l a y s and l e a p s o f s i n g l e dd  1 were q u i t e e v i d e n t  (Table 8 ) .  Frequency o f  were reduced i n a l l r a c e s .  P dd  de-  c r e a s e d t h e i r f r e q u e n c y o f t h r u s t s g r e a t l y whereas UA and G dd i n c r e a s e d theirs slightly.  I f we compare r a c e s we f i n d t h e degree o f changes much t h a n i n UA and G dd  g r e a t e r i n PdV thrusts: p< . 0 2 ) .  tegy than the o t h e r  F u r t h e r m o r e , V dd d'd".  (displays:  seemed t o r e l y on a d i f f e r e n t  ,001;  stra-  They f o u g h t ( T a b l e 9 ) .  There was a tendency f o r p a i r s o f UAdd dd  leaps; p <  p < . 0 2 ;  t o d i s p l a y more than p a i r s  (means: UA = 1 0 , P = 4 , G = 2 ; p < . l ) .  of  P and G  to  d i s p l a y w i t h i n 2 cm more o f t e n than P o r G d'd (JJA 5/8 t r i a l s , 1 3 t i m e s  3  UA  d'd" i a  tended  s o  1  t o t a l ; P 2 / 9 , 4 ; G 2 / 8 , 3 ; p = . 1 1 ) . No d i f f e r e n c e between t h e r a c e s i n mean number o f c h a s e s , l e a p s , o r t h r u s t s were r e c o r d e d . All  dd  d e c r e a s e d t h e i r d i s t a n c e from t h e ? when a n o t h e r d was  The p e r c e n t a g e o f t i m e i n a t r i a l length o f a ?  i n which t h e d was w i t h i n a d  f o l d , UA  fish-  d i d n o t d i f f e r between t h e r a c e s i n t h e c o m p e t i t i v e s i t u a -  t i o n , a l t h o u g h i t d i d d i f f e r when t h e d Note t h a t P dd  present.  was a l o n e w i t h a  i n c r e a s e d t h e i r time v e r y c l o s e t o a ?  $ (Table 1 0 ) .  more t h a n f i v e  dd b y j u s t under t h r e e f o l d , and G dd by j u s t o v e r two f o l d  from t h e 1-d" t o t h e 2-d*  experiment.  s a m p l i n g t h e p o s i t i o n s o f t h e dd  The d a t a i n T a b l e 1 1 a r o s e from  e v e r y 1 5 seconds i n t h e t r i a l .  One o r  But see F i g . 1 3 i n E x p e r i m e n t 3 . T h e r e , t o t a l c o u r t s h i p was measured. Because o f t h e d e p r i v a t i o n p e r i o d p r i o r t o o b s e r v a t i o n h e r e , almost a l l of the f i s h were c o u r t i n g f o r t h e d u r a t i o n o f t h e t r i a l .  53  T a b l e 8.  Differences i n frequencies o f courtship a c t i v i t i e s o f i n d i v i d u a l dd when t e s t e d a l o n e w i t h a ? (Experiment 1) o r i n t h e . p r e s e n c e o f a n o t h e r d (Experiment 7 ) . D i f f e r e n c e e x p r e s s e d as mean % change i n number o f b o u t s p e r f o r m e d f o r t h e same dd from Experiment 1 t o Experiment 7.  UA Displays  73.3 r e d u c t .  27.4 r e d u c t .  54.6  Leaps  71.4 r e d u c t .  19.0 r e d u c t .  22.3 r e d u c t .  Thrusts  66.3 r e d u c t .  9.3 i n c r e a s e  K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e ,  2  reduct  p < .02 p < .001  9.5 i n c r e a s e p <  .02  d f ,corrected f o r ties,  Numbers f o r r a n k i n g were a r r i v e d a t b y t h e f o l l o w i n g f o r m u l a : % change = # b o u t s i n c o m p e t i t i o n / ( . 6 6 7 ) (# b o u t s a l o n e ) where .667 i s a c o r r e c t i o n f a c t o r f o r t h e d i f f e r e n c e i n t h e l e n g t h o f the t r i a l s . When b o t h t h e numerator and t h e denominator were 0, t h e t r i a l was d i s c a r d e d . When t h e numerator was 0, t h e number a r r i v e d a t was 0. When t h e denominator was 0, t h e number a r r i v e d a t was i n f i n i t y .  54  Table 9.  Male charges i n a competition s i t u a t i o n o f two o V and one ?.  P  UA  G  28  4  4  26  0  0  7/9  2/8  2/8  Mean number of charges Median number of charges Number o f t r i a l s i n which changes occurred  Kruskal-Wallis one-way a n a l y s i s o f variance, 2 df.  p< .02  T a b l e 10.  Mean p e r c e n t a g e o f t i m e i n t r i a l i n which a was w i t h i n one d* f i s h - l e n g t h (approx 2 cm) o f a ..? i n one-d" (Experiment 1) and two- d* (Experiment 7) s i t u a t i o n s .  lrf-1? 2dV_i?  Kruskal-Wallis  P  UA  G  5  12  19  p =  26  36  44  p<  one-way a n a l y s i s o f v a r i a n c e ,  N = 13 and 18 f o r P, 16 and 16 f o r UA,  .001 .3  2 df.  and 17 and 16 f o r G.  T a b l e 11.  Occurrence the two-o" centage o f o r two dd  o f dd w i t h i n a 2 cm r a d i u s o f a ? i n s i t u a t i o n . Numbers- r e p r e s e n t t h e p e r photographs i n w h i c h no dd , one d appeared w i t h i n t h e 2 cm r a d i u s . t  P  UA  G  5  6  3  % no dd  57  57  54  % Id  30  32  38  % 2dd  13  11  8  N ( p a i r s o f dd )  Each e n t r y i s t h e average o f a t l e a s t 35 frames and u s u a l l y 40 frames measured f o r each p a i r o f dd .  57 both o f the  were w i t h i n 2 cm o f a ? i n almost h a l f o f t h e o b s e r v a -  t i o n s i n a l l r a c e s ( P , 43%, UA 43%; G, 4 6 % ) . C o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d between a l l measures t a k e n . There was no i n d i c a t i o n t h a t t h e l a r g e r d'd* were i n t h e c l o s e r p o s i t i o n relative to a  ? i n any o f t h e r a c e s .  S i z e was n e g a t i v e l y  correlated  w i t h b o t h number o f d i s p l a y s and number o f t h r u s t s i n t h e G r a c e (p <.008 and p <.05, r e s p e c t i v e l y ) . and b e h a v i o u r appeared. no advantage t o one some c o u r t s h i p  only  No o t h e r c o r r e l a t i o n s between s i z e  I t follows that larger o r smaller  s i z e confers  d* o v e r a n o t h e r i n t h e f r e q u e n c y o f p e r f o r m a n c e o f  a c t i v i t i e s , w i t h t h e above e x c e p t i o n i n t h e G r a c e .  Certain behaviour patterns as w i t h c l o s e p r o x i m i t y  were c o r r e l a t e d w i t h one a n o t h e r , as w e l l  to a ? .  Many more s i g n i f i c a n t p o s i t i v e c o r r e l a -  t i o n s i n d i s p l a y and c o n t a c t b e h a v i o u r were found i n P  d'd" ( T a b l e 1 2 ) .  T h i s i n d i c a t e s t h a t when a P d" p e r f o r m s one d i s p l a y o r c o n t a c t b e h a v i o u r more f r e q u e n t l y , he a l s o does more o f e v e r y t h i n g  else.  Since these  corre-  l a t i o n s d i d n o t appear i n t h e one d*-one % e x p e r i m e n t , t h i s may be a r e s p o n s e to competition.  P  who were charged more tended t o d i s p l a y l e s s , and  charged l e s s when c l o s e t o a J . were n e i t h e r  On t h e o t h e r hand, more a g g r e s s i v e P d'd  1  l a r g e r n o r d i d t h e y d i s p l a y more t h a n l e s s a g g r e s s i v e d'd . 1  The  h i g h p o s i t i v e c o r r e l a t i o n between charges and d i s p l a y s and charges  and  l e a p s i n UA  d'd" r e s u l t s from t h e e f f e c t i v e n e s s  whom o n l y charged once.  Displays,  o f o n l y two  d'd , one o f 1  l e a p s , and t h r u s t s p e r f o r m e d by one <S  d i d n o t appear t o i n f l u e n c e t h e p e r f o r m a n c e o f t h o s e b e h a v i o u r s i n t h e other  d*.  58 T a b l e 12.  Correlation coefficients of courtship a c t i v i t i e s i s a two-d", one-? s i t u a t i o n .  Activities  correlated  Number o f d i s p l a y s and p e r c e n t a g e o f time o f t r i a l d" i s w i t h i n 2 cm o f ?  Race  R  Probability of R being 0  p UA G  .16 .02 -.14  Number o f l e a p s and number o f displays  P UA G  .71 .90 .37  Number o f t h r u s t s and number of d i s p l a y s  P' UA G  .65 -.23 .61  .003 > .1 .01  P UA G  -.35 .80 -.13  >  Number o f t i m e s charged and number o f d i s p l a y s  P UA G  -.41 .05 .08  Number o f t i m e s w i t h i n 2 cm o f ? and number o f l e a p s  P UA G  .40 .05 -.34  Number o f t i m e s w i t h i n 2 cm o f ? and number o f t h r u s t s  P UA G  Number o f t i m e s w i t h i n 2 cm o f $ and number o f charges  Number o f charges and number of displays  > .1 > .1 > .1 .0008 < .0001 > .1  >  .1 .0001 .1 .09 .1 .1  > > > > >  .1 .1 .1  .63 .33 .22  > >  .005 .1 .1  P UA G  -.44 .11 .21  > >  .07 .1 .1  Number o f l e a p s and number o f thrusts  P UA G  .55 -.22 .21  > >  .02 .1 .1  Number o f l e a p s and number o f charges  P UA G  -.03 .74 -.13  Number o f t h r u s t s and number o f charges  P UA G  -.21 -.18 -.20  > > > > >  .1 .0009 .1 .1 .1 .1  59 Previous experience with a p a r t i c u l a r t e s t $ the  d 's performance i n c o m p e t i t i o n .  c o u r t s h i p b e h a v i o u r s when a  I n a d d i t i o n , the frequency o f  was a l o n e w i t h a  ?  no b e a r i n g on h i s performance i n t h i s experiment. courter i n the s i n g l e d  had no e f f e c t on  i n E x p e r i m e n t 1 had Thus, a v e r y  s i t u a t i o n d i d not n e c e s s a r i l y outperform  active a less  a c t i v e c o u r t e r when t h e y were p l a c e d i n c o m p e t i t i o n .  C.  C o m p e t i t i o n i n c o u r t s h i p I I I (Experiment  1.  Introduction The r e s u l t s o f Experiments  8)  3-7 suggest  f u r t h e r i n v e s t i g a t i o n of the  r o l e s o f a g g r e s s i o n , t e r r i t o r y , and " p o s s e s s i o n " o f a courtship.  S  i n relation to  Braddock (1949) found t h a t p r i o r r e s i d e n c e gave p l a t y f i s h ,  Xiphophorus m a c u l a t u s ,  a g r e a t e r p o t e n t i a l f o r dominance.  gathered s i m i l a r evidence  for %  Xiphophorus h y b r i d s .  experimental design allowed examination  I n Experiment 8 the  o f t h e e f f e c t s o f d i f f e r e n t num-  b e r s o f o V u p o n t h e c o u r t s h i p p e r f o r m e d t o one c o u r t s h i p by each o f t h r e e  Heuts (1968)  ? , the c o n t r i b u t i o n t o  oV w i t h d i f f e r e n t residency periods w i t h the  ?  , and t h e i n t e r a c t i o n s between t h e o V .  2.  M a t e r i a l s and Methods Females were s e l e c t e d f o r tameness and one ? was p l a c e d i n each  o b s e r v a t i o n tank a t about 1000 h o u r s .  I n t h e a f t e r n o o n ad"  was added.  O b s e r v a t i o n took p l a c e t h e f o l l o w i n g m o r n i n g , f o r 10 minutes between 0945 and 1335 h o u r s .  A n o t h e r d" o f t h e same r a c e was added t h a t a f t e r n o o n  between 1600 and 1845 h o u r s , and t h e t h r e e f i s h were o b s e r v e d morning.  This procedure  the next  was r e p e a t e d once more s o t h a t a t o t a l o f t h r e e  60 dd  were observed w i t h a ?  over a three-day p e r i o d .  was  r u n wherein:'.; s i n g l e dd were o b s e r v e d  way  as i n the e x p e r i m e n t a l  trials.  f o r t h r e e days i n the same  A R u s t r a k event r e c o r d e r was  t o r e g i s t e r d i s p l a y s and c h a s i n g , and charges and down.  No d V  were used more than once.  r a c e , 15 P, 15 UA,  A control series  employed  l e a p s were w r i t t e n  Of 15 t r i a l s  a t t e m p t e d f o r each  and 13 G were c o m p l e t e d .  3.  Results  a.  E f f e c t s o f the d i f f e r e n t numbers o f d'd* I hypothesized  on the c o u r t s h i p p e r f o r m e d .  t h a t i f no c o m p e t i t i o n took p l a c e between the  the t o t a l number o f d i s p l a y s , c h a s e s , and  l e a p s would on a l l days be  m u l t i p l e o f day 1 o f the t r i a l - - w h e n o n l y one  d*  t h e r e i s no d e p r i v a t i o n p e r i o d as i n E x p e r i m e n t 7.  was  present.  The  assumption t h a t  1  was  Guppies whose p a r e n t s came from b o t h the Diego M a r t i n and  Curacaye streams i n T r i n i d a d were u s e d due t o a s h o r t a g e o f o t h e r but my i m p r e s s i o n i s t h a t t h e s e f i n d i n g s can be g e n e r a l i z e d . r e p l i c a t e s f a i l e d t o d i s p r o v e my  a  Note t h a t  s i n g l e d'd c o u r t e d much t h e same on each o f t h r e e c o n s e c u t i v e days tested.  d'd" ,  Petite fish,  Sixteen  a s s u m p t i o n (Wilcoxon t e s t between each  4, p a i r o f days ) . trials  In f a c t , d i s p l a y frequency  (means: day  1, 1.63;  day 2, 1.81;  r o s e on the t h i r d day o f t h e  day 3, 2.88).  To t e s t t h e h y p o t h e s i s , t h a t no c o m p e t i t i o n took p l a c e between expected  dd  f r e q u e n c i e s and d u r a t i o n s were d e r i v e d i n the f o l l o w i n g way.  average f r e q u e n c y  o r d u r a t i o n o f an a c t i v i t y by a l l dd  on day  1, i n  H e r e a f t e r , p r o b a b i l i t y v a l u e s f o l l o w e d by " W i l c o x o n " w i l l r e f e r t o the Wilcoxon matched-pairs signed-ranks t e s t , t w o - t a i l e d .  The  each r a c e , was  added t o the f r e q u e n c y o r d u r a t i o n o f t h a t a c t i v i t y o f  each i n d i v i d u a l o f t h e r a c e t o g i v e e x p e c t e d numbers f o r day 2. l a r l y , t w i c e the average f r e q u e n c y o r d u r a t i o n was  added t o i n d i v i d u a l  r e s u l t s o f day 1 t o y i e l d e x p e c t e d numbers f o r day 3. presence o f o t h e r  dd  Simi-  Thus, i f t h e  d i d not a f f e c t another d * s performance,  p e c t e d and o b s e r v e d f i g u r e s f o r each day would be e q u a l .  the ex-  T r i a l s i n which  a g i v e n b e h a v i o u r n e v e r o c c u r r e d were e x c l u d e d from a n a l y s i s o f t h a t be-, haviour. The r e s u l t s a r e summarized i n F i g . 17. f o l l o w i n g are from t h e W i l c o x o n t e s t .  A l l the p r o b a b i l i t y v a l u e s  Frequency and t o t a l d u r a t i o n o f  d i s p l a y s were s i g n i f i c a n t l y below e x p e c t e d on t h e t h i r d day i n P and dd dd GoV  (p< . 0 1 ) , and d i s p l a y d u r a t i o n was (p< .01).  a l s o low on t h e second day i n UA  Thus, i n c r e a s i n g numbers o f  dd  showed no e v i d e n c e o f change i n d i s p l a y s  t h a t each d  UA  d i s p l a y e d as i f no o t h e r dd  l e a p e d l e s s t h a n e x p e c t e d on t h e t h i r d day i n c o n t r a s t , l e a p e d more on the t h i r d day  i n h i b i t e d these behaviours. ( F i g . 1 7 a ) , which means  were p r e s e n t .  Both P and UA G  (P: p<.05; UA: p<.02). ( F i g . 17b).  Frequency  dd dd,  and  t o t a l t i m e o f c h a s i n g i n c r e a s e d more t h a n e x p e c t e d on each c o n s e c u t i v e day i n a l l r a c e s (day 2: p < . 0 1 , w i t h t h e e x c e p t i o n o f UA p < . 0 5 ; day 3: p <.01; dd  F i g . 17c).  b.  Not s u r p r i s i n g l y , i n c r e a s i n g numbers o f  enhanced c h a s i n g , which appears t o be a  from t h e p r e s e n c e o f o t h e r  dd  frequency,  d"'s a t t e m p t t o remove a ¥  .  C o n t r i b u t i o n s o f d i f f e r e n t males t o the t o t a l  courtship  I f we sum the amount o f a g i v e n b e h a v i o u r on one day o f t h e  trial  and d i v i d e t h a t t o t a l by the number o f p a r t i c i p a n t s we a r r i v e a t an  62  Fig. of  17.  Comparison o f t h e c o u r t s h i p performed b y d i f f e r e n t  dd w i t h one ? .  t h r e e on day 3.  numbers  One d was p r e s e n t on day 1, two on day 2, and  The darkened  c i r c l e s and s o l i d l i n e s r e p r e s e n t ob-  s e r v e d d a t a and t h e open c i r c l e s and dashed l i n e s a r e e x p e c t e d v a l u e s . The number o f samples f o r each d a t a p o i n t - a r e shown under t h e r a c e designations.  ** s i g n i f i e s p<.01 and * s i g n i f i e s p < .05.  v a l u e s a r e d e r i v e d from t h e W i l c o x o n m a t c h e d - p a i r s  Probability  signed-ranks  two  tailed.  a.  Comparison o f mean f r e q u e n c y and d u r a t i o n o f d i s p l a y s .  b.  Comparison o f mean f r e q u e n c y o f l e a p s .  c.  Comparison o f mean f r e q u e n c y and d u r a t i o n o f c h a s e s .  test,  DISPLAYS MEAN DURATION (SEC)  MEAN FREQUENCY  O  ~1  Wi  ©  u%  I  I  1  o  1  G  >  LEAPS MEAN FREQUENCY o  qz9  CHASES MEAN DURATION (SEC)  ?Z9  MEAN FREQUENCY  63  expected  l e v e l o f p e r f o r m a n c e f o r a d i f a l l dd  equally.  were c o n t r i b u t i n g  I f p r i o r r e s i d e n c e c o n f e r s any dominance t o t h e f i r s t  would expect h i m t o exceed t h e o t h e r d of a c t i v i t y  toward t h e ? .  and l e a p s f o r a l l t h e dd  o r dd  d  we  and the average amount  F i g . 18 compares t h e p e r f o r m a n c e s o f d i s p l a y s  on each o f t h e t h r e e days o f t h e t r i a l .  case i s t h e r e a s t a t i s t i c a l l y  I n no  s i g n i f i c a n t indication that the f i r s t d  had an advantage o v e r t h e o t h e r s , o r t h a t any o f t h e dd d i f f e r e d f r o m one  a n o t h e r on days 2 and 3.  seemingly  o f leaps precludes the  l a r g e d i f f e r e n c e s e x h i b i t e d i n F i g . 18 from r e a c h i n g  significance. increased  The low f r e q u e n c y  The d e c r e a s e d  l e v e l of d i s p l a y behaviours  statistical  observed  with  <J d e n s i t y i n t h e P and UA r a c e s was t h e r e f o r e n o t d i c t a t e d by  a t e r r i t o r i a l or "possessive" d  , b u t by some o t h e r i n t e r a c t i o n s o f t h e  fish.  c.  I n t e r a c t i o n s between t h e males The mechanisms o f i n t e r a c t i o n s between dd  were n o t always c l e a r .  I c o u l d see no e f f e c t s o f s u b t l e body c o n t a c t s d u r i n g c h a s i n g and changes i n body and f i n p o s t u r e t o t h e ? activity  on ^  behaviour.  w h i c h o b v i o u s l y changed©* - d b e h a v i o u r .  were t o t a l l y  F i g h t i n g was t h e o n l y Here, t h e i r a t t e n t i o n s  d i r e c t e d toward one a n o t h e r r a t h e r t h a n t o w a r d t h e ? .  A g g r e s s i v e b e h a v i o u r need o n l y be c o n s i d e r e d in P dd charges o c c u r r e d i n 750 f i s h - m i n u t e s v a t i o n times where a t l e a s t two dd  .  Only f o u r  (number o f f i s h m u l t i p l i e d by o b s e r were p r e s e n t ) i n UA and o n l y two  charges o c c u r r e d i n 650 f i s h - m i n u t e s i n G; whereas 247 c h a r g e s  occurred  i n 700 f i s h - m i n u t e s i n P ( i n 11/14 t r i a l s ) .  The amount o f P a g g r e s s i o n  i n t h i s experiment when two dd  (47.86 charges/100  were p r e s e n t  fish-  64  Fig.  18.  Contributions  day o f the e x p e r i m e n t .  o f d i f f e r e n t dV  t o t o t a l c o u r t s h i p on each  For each day, d"  1 i s on t h e l e f t , e t c .  Dashed  l i n e s r e p r e s e n t t h e average v a l u e s f o r a l l t h e d'd* and t h e e x p e c t e d v a l u e f o r each d"  .  No s t a t i s t i c a l l y  See t e x t f o r d i s c u s s i o n .  s i g n i f i c a n t differences  appeared.  LEAPS  DISPLAYS  MEAN FREQUENCY  MEAN DURATION MEAN FREQUENCY (SEC)  >•  K  11  tl 1  a > K  >  5  65  minutes) was markedly lower t h a n i n E x p e r i m e n t 7 (140.00  charges/100  f i s h m i n u t e s ; p = .0344, Mann-Whitney U t e s t c o r r e c t e d f o r t i e s ) . Apparently f a m i l i a r i t y with the other d of  aggression.  and t h e ?  Friedman two-way a n a l y s i s o f v a r i a n c e shows no  ences i n t h e f r e q u e n c y o f charges between P dd where c h a r g i n g o c c u r r e d on day 2, f i r s t n e a r l y t h r e e t o one nificant  dd  dd  .  In the n i n e t r i a l s  out-charged secondoV  charged 49 t i m e s .  A g a i n , d i f f e r e n c e s were not s t a t i s t i c a l l y  No c o n s i s t e n c y appeared i n who  by insig-  On day 3 f i r s t  c h a r g e d e q u a l l y (27 and 24 t i m e s ) , w h i l e t h i r d  more (72 t i m e s ) .  differ-  (92-32), but t h i s d i f f e r e n c e i s s t a t i s t i c a l l y  (Wilcoxon) because one d  and second  reduced the l e v e l  dd  charged  reliable.  charged whom between f i r s t and second  on t h e two days t h e y were o b s e r v e d t o g e t h e r .  dd  I n a d d i t i o n , charges d i d  not b e a r any r e l a t i o n t o d i s p l a y i n g i n any o f t h e r a c e s . However, one  d  Q  f t h e f i r s t two i n t r o d u c e d p e r f o r m e d more d i s p l a y  b e h a v i o u r t h a n t h e o t h e r on b o t h t h e second and t h i r d days o f t h e e x p e r i ment.  The l i k e l i h o o d t h a t t h i s r e s u l t s bv chance a r e s l i m .  (Table 13).  The r e s u l t s o f e x p e r i m e n t s 1 and 7"* suggest t h a t i n t e r a c t i o n s a r e e s s e n tial in  determining which d  d i s p l a y s most.  T h i s experiment suggests  t h a t t h e r e s u l t s o f t h e s e i n t e r a c t i o n s a r e s t a b l e f o r a t l e a s t a two-day period.  Remember t h a t f i s h were n o t s e p a r a t e d from one a n o t h e r i n t h i s  experiment. The e f f e c t s o f s i z e on d-d i n t e r a c t i o n s appear t o be n e g l i g i b l e . Length (P, X = 17.2 mm;  UA, X = 18.8 mm;  G, X = 18.2 mm)  was  significantly  c o r r e l a t e d w i t h d i s p l a y i n g i n s e v e r a l i n s t a n c e s , m a i n l y i n P and UA, ^No r e l a t i o n e x i s t e d between the amount o f d i s p l a y i n g o f s i n g l e dd n o n - c o m p e t i t i v e and c o m p e t i t i v e s i t u a t i o n s .  but in  66  T a b l e 1 3 . R e l a t i v e amount o f d i s p l a y b e h a v i o u r o f f i r s t and second <f<f on days 2 and 3. P r o b a b i l i t y v a l u e s a r e d e r i v e d from t h e b i n o m i a l t e s t .  Race  T o t a l No. of T r i a l s  No. o f t r i a l s i n w h i c h same d* d i s p l a y e d most b o t h days  No. o f t r i a l s i n w h i c h same d" d i d n o t d i s p l a y most b o t h days  P  13  11  2  p =  .011  UA  14  10  4  p =  .090  G  12  9  3  p =  .073  Race  No. o f Trials i n which leaps occurred  P  No. o f t r i a l s i n w h i c h d" who d i s p l a y e d most b o t h days a l s o l e a p e d most 9  2  p =  .033  5  0  p =  .031  5  1  p =  .109  11  UA  5  G  6  No. o f t r i a l s i n w h i c h d" who d i s p l a y e d most b o t h days d i d n o t l e a p most  67  d i d n o t c o r r e l a t e w i t h t h e d who d i s p l a y e d most on t h e t h i r d y e a r . Leaps and charges bore no r e l a t i o n t o l e n g t h .  d.  Comparison o f t h e r a c e s K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e was employed t o compare  t h e b e h a v i o u r of dd  o f t h e t h r e e r a c e s o v e r t h e t h r e e days. F i g . 19  summarizes t h e comparison o f d i s p l a y s , l e a p s , and c h a s e s . d i s p l a y e d l e s s than the o t h e r  dd  }  On day 1, G dd  b u t n o t s i g n i f i c a n t l y l e s s as i n Ex-  p e r i m e n t 1 ( t h i s was p r o b a b l y owing t o t h e s h o r t e r o b s e r v a t i o n t i m e ) . dd  p e r f o r m e d more l e a p s t h a n t h e o t h e r  dd ( p < . 0 5 ) , a d i f f e r e n c e n o t  d e t e c t e d i n t h e c o n d i t i o n s o f E x p e r i m e n t 1. amounts o f t i m e c h a s i n g  UA  A l l dd  ( p > . 2 ) , b u t UA dd  s p e n t about t h e same  chased more o f t e n t h a n  t h e o t h e r s (p< .01). The t o t a l t i m e d i s p l a y i n g d o u b l e d i n P and G dd b u t i n c r e a s e d o n l v s l i g h t l y o v e r day 1 i n UA  dd  .  on t h e second day,  P s p e n t t h e most t i m e  d i s p l a y i n g (p< .05). The number o f d i s p l a y s d i d i n c r e a s e i n UA P dd  dd  , but  d o u b l e d and G d'd* more t h a n d o u b l e d t h e i r d i s p l a y f r e q u e n c i e s .  d i s p l a y e d more f r e q u e n t l y and G dd  P dd  d i s p l a y e d l e s s f r e q u e n t l y (p = .05).  The mean d i s p l a y bout l e n g t h o f f i r s t  dd  i n P and G remained a t about two  seconds on each o f t h e t h r e e d a y s , b u t dropped from 2.8 seconds on day 1 t o 1.9 and 1.8 seconds on days 2 and 3, r e s p e c t i v e l y , i n UA (p< .05, Friedman two-way a n a l y s i s o f v a r i a n c e ) .  A l l races increased t h e i r  quency o f l e a p s on day 2, P most and UA l e a s t , b u t G dd (p< .05).  fre-  leaped less  These r e s u l t s c o n t r a s t w i t h t h o s e o f E x p e r i m e n t 7, where i n  a two- d s i t u a t i o n f r e q u e n c i e s o f d i s p l a y s and l e a p s were r e d u c e d when  68  Fig.  19.  Comparison o f t h e c o u r t s h i p p e r f o r m e d bv dd  t h r e e r a c e s on each o f t h e days o f t h e t r i a l s . histograms  r e p r e s e n t s P, UA, and G dd  o f the  Each group o f t h r e e  , i n that order.  Kruskal-  W a l l i s one-way a n a l y s i s o f v a r i a n c e p r o b a b i l i t i e s appear above t h e histograms. for  a given  Sample s i z e s a r e shown on t h e f i r s t group o f behaviour.  histograms  DAY 1  DAY 2  DAY  «.05  20 IS  MEAN DISPLAY FREQUENCY  >.2  10  5  . i t l  0  ruts  40  MEAN DISPLAY DURATION (SEC)  <.05  r  30  >.8  >.2  20 10 14  <.0S 1.0 <.05  MEAN LEAP FREQUENCY  tL  ^ 4 L5j  <.2  10  s  MEAN CHASE FREQUENCY  <.2  6 4 2 0  <.01 141512  25 20  MEAN CHASE DURATION (SEC)  IS  <,2  10  s 0  >.2 _r-f~r-l.. 14 IS 12  n  69  compared t o the one-d" s i t u a t i o n o f Experiment 1. the P dd  who  reduced these behaviours  F u r t h e r m o r e , i t was  the most.  The  d i f f e r e n c e s are  t h a t i n the p r e s e n t e x p e r i m e n t no p e r i o d o f i s o l a t i o n was the dd  , one  d  was  w i t h the %  l o n g e r t h a n t h e o t h e r , and t h e dd  the o p p o r t u n i t y t o l e a r n about one do more c h a s i n g  (p <. 2 ) .  imposed upon  a n o t h e r and the  ¥ .  G dd  had  tended t o  No d i f f e r e n c e i n c h a s i n g were found i n E x p e r i -  ment 7. By the t h i r d day d i f f e r e n c e s i n d i s p l a y i n g d i s a p p e a r e d dd  d i d n o t d i s p l a y more t h a n on t h e s e c o n d day, UA  s l i g h t l y more, and G dd from day races Two  1 t o day 2.  (p< .05).  P dd  dd  (p> . 8 ) .  displayed only  d i s p l a y e d more, i n p r o p o r t i o n w i t h the  Leaps d i f f e r e d , but P dd  P  increase  leaped l e s s than the  other  The p a t t e r n o f change o f l e a p i n g d i f f e r e d q u i t e s t r i k i n g l y .  t o g e t h e r l e a p e d much more f r e q u e n t l y than one, but t h r e e P  l e a p e d w i t h the same f r e q u e n c y on the t h i r d day was  as one.  The  amount o f l e a p i n g o f UA  mid-way between the s c o r e s o f days 1 and 2.  s i m p l y d o u b l e d t h e i r average number o f l e a p s on c o n s e c u t i v e days.  dd dd  G  dd UA  dd  s p e n t l e s s t i m e c h a s i n g on d a y 3 ( p < . 0 5 ) and t e n d e d t o chase l e s s o f t e n (p< . 2 ) .  The  a d d i t i o n o f the t h i r d P d  induced  a v e r y s h a r p upward s u r g e  i n c h a s i n g when compared t o the p r e v i o u s d a y s , and G  dd  d i r e c t p r o p o r t i o n t o t h e i r i n c r e a s e i n numbers o v e r day  chased more i n 2.  As n o t e d i n p a r t c above, the p r e s e n c e o f a g g r e s s i v e a c t i o n s i n P the absence o f i t i n UA and G a r e o f an a l m o s t a l l o r n o t h i n g Differences i n behaviour  o f i n d i v i d u a l dd  and  nature.  between the r a c e s  are  mentioned i n p a r t s a, b, and c o f t h i s e x p e r i m e n t and g e n e r a l l y f o l l o w the d i f f e r e n c e s d i s c u s s e d above.  70  H.  Summary o f t h e male's c o u r t s h i p  I.  The b e h a v i o u r  o f s i n g l e males  P and U A dd , t h r o u g h b e h a v i o u r more o b v i o u s than G dd  i n courtship.  G dd , b u t d i s t a n c e from t h e ? proximity t o the ?  and c o l o r p a t t e r n s , a r e p r o b a b l y P and U A <JV d i s p l a y e d more t h a n  d u r i n g d i s p l a y was t h e same and c l o s e P dd  was mandatory t o i n i t i a t e d i s p l a y i n a l l r a c e s .  o r i e n t a t e d a t g r e a t e r d i s t a n c e s and a t g r e a t e r a n g l e s r e l a t i v e t o t h e ?' and moved above h e r and d i s p l a y e d t h e r e more f r e q u e n t l y . themselves a t more a c u t e a n g l e s above and below t h e ? changed p o s i t i o n s r e l a t i v e t o t h e ? l e a s t o f t e n . a ?  G  dd p o s i t i o n e d  , and, w h i l e d i s p l a y i n g ,  U A d<f came c l o s e r t o  w h i l e d i s p l a y i n g , chased h e r more o f t e n , and l e a p e d more t h a n t h e  o t h e r r a c e s when t h e r e was a l o n g e r i n t r o d u c t o r y p e r i o d w i t h a ? . had a l o n g e r and G dd  , a shorter, latency to display.  G dd  least attention to ??  a t s h o r t e n f o r c e d d i s t a n c e s from them.  P dd  paid the Gonopodial  swings and t h r u s t s were s i m i l a r f o r a l l r a c e s .  2.  The b e h a v i o u r  o f two o r more males  Neither previous experience oned* -one?  w i t h a ? , previous performance i n a  s i t u a t i o n , p r i o r r e s i d e n c e , n o r s i z e c o r r e l a t e d w i t h a d 's  performance i n t h e p r e s e n c e o f o t h e r dd . i n one  d ' s courtship behaviour  P dd other  dd.  However, a c o n s i s t e n c y e x i s t e d  i n r e l a t i o n t o another d .  were much more a g g r e s s i v e t h a n U A and G dd Increased  suggesting that  dd  aggressiveness  f i g h t over ? ? .  d i s p l a y l e s s when f i r s t e n c o u n t e r i n g  upon  encountering  occurred i n the presence o f Pdd  ??,  who were c h a r g e d tended t o  one a n o t h e r , b u t t h i s r e l a t i o n s h i p  71  d i d n o t h o l d a f t e r some time t o g e t h e r , and the l e v e l o f a g g r e s s i o n dropped. P a i r s o f P dd  c o u r t e d and d i s p l a y e d more t h a n p a i r s o f UA and G  a f t e r an a f t e r n o o n and n i g h t w i t h a ? . each p a i r were c o n s i d e r e d , P dd one a n o t h e r and a $  When o n l y t h e t o p c o u r t e r s o f  c o u r t e d more.  Two dd  However, i f two  i n t e r a c t p r i o r t o o b s e r v a t i o n , no d e c r e a s e was n o t e d .  dd b u t n o t i n G  My i m p r e s s i o n i s t h a t dd  of another d  o r dd  a n o t h e r , a l l dd  b e f o r e d i s p l a y i n g , and t h e p r e s e n c e  moved c l o s e r t o t h e One  Upon b e i n g i n t r o d u c e d t o one  ¥ to the extent that  or both  interracial  dd were w i t h i n a f i s h - l e n g t h o f  ? f o r almost h a l f the time o f t h e t r i a l i n the two- d s i t u a t i o n ,  one, two, o r t h r e e dd dd  and  o f d i f f e r e n t r a c e s remained c l o s e even l o n g e r .  decreased t h e i r frequency o f t h r u s t s g r e a t l y i n the presence o f a  second  UA  The a d d i t i o n o f  dd.  made t h i s d i f f i c u l t .  differences disappeared.  d  h a d time t o -  u s u a l l y attempt t o maximize t h e amount o f  a t t e n t i o n t h e y r e c e i v e from t h e ?  P  dd  d w i t h time f o r l e a r n i n g l e d t o l e s s d i s p l a y i n g and l e a p i n g t h a n  e x p e c t e d i n P and UA  the  introduced to  a f t e r an i s o l a t i o n 'period d i s p l a y e d and l e a p e d l e s s  than they d i d i n d i v i d u a l l y w i t h a ? .  a third  dd  CJ* , whereas UA and G dd  situation.  S m a l l e r G dd  i n c r e a s e d t h e i r s s l i g h t l y over the s i n g l e  d i s p l a y e d and t h r u s t more t h a n l a r g e r ones.  dd tended t o d i s p l a y more and more c l o s e l y t o the ?  .  More  dd  meant more c h a s i n g i n a l l r a c e s . There were no i n t e r r a c i a l d i f f e r e n c e s i n d i s p l a y f r e q u e n c y when t h r e e dd not). G  dd  were p r e s e n t (see E x p e r i m e n t 9, whether o f t h e same r a c e o r  I n three-d" t h r u s t more.  s i t u a t i o n s Pdd G dd  l e a p e d l e s s t h a n o t h e r r a c e s , and  behaved almost as i f no o t h e r  dd  were p r e s e n t ,  72  T a b l e 14 summarizes m o r p h o l o g i c a l , b e h a v i o u r a l , and  environmental  d i f f e r e n c e s between t h e r a c e s by r a n k i n g each r a c e from 1 t o 3 f o r each p a r a m e t e r c o n s i d e r e d .  (1>2>3)  73  T a b l e 14.  Summary o f m o r p h o l o g i c a l , b e h a v i o u r a l , and e n v i r o n m e n t a l d i f f e r e n c e s between t h e r a c e s . Rank 1 > 2 > 3 . An a s t e r i s k a f t e r a r a c e denotes a s t a t i s t i c a l l y v a l i d d i f f e r e n c e between t h a t r a c e and t h e o t h e r s . More t h a n one a s t e r i s k means t h a t t h e r a c e s marked d i f f e r s i g n i f i c a n t l y .  Rank  1  2  3  Size  UA*  P*  G*  Brightness  P and UA  Sex r a t i o  P*  Water c l a r i t y  P and UA  Predators  G  UA  G  Schooling  G*  UA  P  % time c l o s e p r o x i m i t y t o $  G*  UA*  P*  Angle o f o r i e n t a t i o n  P  UA  G  courtship  P  UA  G  Bouts o f s i g m o i d d i s p l a y  UA  P  G*  Latency  P*  UA*  G*  UA* P*  P  G* UA and G  (after isolation)  P*  G  UA  Leaps w i t h 3  G  UA  P*  G*  P  UA  Parameter . -  G G*  UA* G  P o s i t i o n changes d u r i n g  to display  Attentiveness t o $ distance Charges between dd  at a  R e d u c t i o n i n d i s p l a y and contact behaviours i n the p r e s e n c e o f a second d dd p r e s e n t  T h r u s t s w i t h 3 dd  present  74 C h a p t e r 5.  D i s c u s s i o n o f Male C o u r t s h i p S t r a t e g i e s  I t i s t e m p t i n g t o assume t h a t b e h a v i o u r p a t t e r n s have e v o l v e d i n t h e same manner as o t h e r f e a t u r e s o f a n i m a l p o p u l a t i o n s , by the s e l e c t i o n o f i n heritable differences. I t i s i m p o s s i b l e t o be c e r t a i n , however s t r o n g the i m p l i c a t i o n about the e v o l u t i o n o f b e h a v i o u r , u n l e s s one can d e m o n s t r a t e the e x i s t e n c e o f " g e n e t i c " v a r i a t i o n s i n b e h a v i o u r upon w h i c h s e l e c t i o n could act. Bastock The  f i e l d and e x p e r i m e n t a l  . '  (1956)  evidence gathered  by Seghers  (1973)  p r o v i d e s s t r o n g arguments i n f a v o r o f t h e a d a p t i v e n a t u r e o f a n t i p r e d a t o r s t r a t e g y , and i t seems l i k e l y t h a t the same f o r c e s have e f f e c t e d the evol u t i o n o f courtship behaviour.  F i r s t c o n s i d e r the b e h a v i o u r  i n r e f e r e n c e t o t h e s i m p l e model p r e s e n t e d t h a t the  </'s  To a c h i e v e  courtship behaviour  i n F i g . 20.  I t i s s a f e t o say  i s goal d i r e c t e d to copulation with a  t h i s g o a l maximum c o n s p i c u o u s n e s s ,  d i s p l a y s , i s probably optimal.  o f s i n g l e dd  with behaviours  such as  I f , however, the environment i n c l u d e s the  eyes o f p i s c i v o r e s as w e l l as t h o s e o f guppy e v o l u t i o n a r y t r a d e - o f f i n conspicuousness.  , t h e r e must e x i s t  d  guppy be.  maximization The  of  Conversely,  ^-attracting  reduced p r e d a t i o n pressure  behaviour  allows f o r  activities.  g u p p i e s s t u d i e d f i t the model w e l l .  d i s p l a y and  an  Q u i t e s i m p l y , the g r e a t e r t h e  p r e d a t o r component o f the model i s , the l e s s c o n s p i c u o u s can the o f the  $•  G dd  are not as q u i c k  are l e s s conspicuous i n d i s p l a y behaviour,  s p a c e , s i z e , and c o l o r than a r e P and UA dd  .  utilization  to  of  Seghers' f i n d i n g s s u g g e s t  75  Fig. 2 0 .  A s i m p l e model showing f a c t o r s  conspicuousness.  influencing  76 t h a t c o l o r i s not i m p o r t a n t i n p r e y s e l e c t i o n by guppy p r e d a t o r s . r e l a t i v e l y d u l l c o l o r a t i o n o f G dd t u r b i d waters w h i c h t h e y i n h a b i t  probably i s a s s o c i a t e d w i t h the (see Chpt. 7 ) .  These guppies  show a g e n e t i c p r e f e r e n c e f o r the s h a l l o w waters n e a r s h o r e . f i x e d t h e i r a t t e n t i o n on  also I f the  dd  a t r e l a t i v e l y l a r g e d i s t a n c e s , not o n l y  might t h e y l o s e s i g h t o f them, but t h e y might f i n d themselves w a t e r s where p r e d a t o r s l u r k .  The  o v e r deeper  On t h e o t h e r h a n d , i n t h e streams where  p r e d a t i o n p r e s s u r e i s r e l a t i v e l y low, t h e dd  exhibit elaborate display  b e h a v i o u r , d i s p l a y r e a d i l y , u t i l i z e more space (which may f u n c t i o n o f the c l e a r w a t e r ) , and a r e l a r g e r and  a  brighter.  The d i s p l a y i t s e l f and the d i s t a n c e from t h e ? p e r f o r m e d seem c o n s e r v a t i v e components i n t h e  a l s o be  a t which i t i s  d 's b e h a v i o u r  repertoire,  a p p a r e n t l y not as e a s i l y a f f e c t e d by s e l e c t i v e p r e s s u r e s as most o t h e r courtship a c t i v i t i e s .  Observations  t u r b i d w a t e r would be  instructive.  o f d i s p l a y b e h a v i o u r and d i s t a n c e i n  The model f i t s w e l l w i t h t h e i d e a s o f G i e s e l (1972), who t h a t the p o t e n t i a l r a t e o f e v o l u t i o n i n s p e c i e s where m o r t a l i t y than  ??  may  be g r e a t e r t h a n expected  suggests  dd s u f f e r h i g h e r  from e x i s t i n g t h e o r y .  He  p r o p o s e s t h a t such s p e c i e s s h o u l d have g r e a t e r n i c h e b r e a d t h , be b e t t e r able to t r a c k short-term environmental efficient I t may  changes g e n e t i c a l l y , and be more  colonizers. be w i s e t o emphasize t h a t a l l t h r e e r a c e s o f  d'd" p e r f o r m a l l  t h e same b e h a v i o u r s , and t h a t t h e m a j o r d i f f e r e n c e s between them a r e quantitative. quantitatively.  S i m i l a r l y , Seghers f i n d s a n t i p r e d a t o r a d a p t a t i o n s t o d i f f e r P f i s h h a r d l y respond  to predators while G f i s h  are  77  h i g h l y r e s p o n s i v e t o them.  UA guppies  f a l l between t h e s e two e x t r e m e s ,  as t h e y d i d w i t h many o f t h e b e h a v i o u r a l measures I employed. Moving c l o s e r t o t h e ? a way i n which ad  i n t h e presence  gains the  she can g e t from o t h e r  dd .  o f other  ¥ 's a t t e n t i o n and m i n i m i z e s  the a t t e n t i o n  I t i s p r o b a b l y s i g n i f i c a n t t h a t G dd t h r u s t  more than t h e c o m p e t i t o r s i n t h e p r e s e n c e  o f others.  s i o n a l l y r e s u l t i n i n s e m i n a t i o n and thus a l l o w a d w i t h o u t endangering  dd seems t o be  T h r u s t s may o c c a t o t r a n s m i t h i s gene's  h i s s u r v i v a l as much as by d i s p l a y i n g .  In a d d i t i o n ,  the low v i s i b i l i t y i n t h e Guayamare might a l l o w more o f t h e s e t h r u s t s t o r e s u l t i n s u c c e s s than would t h e c l e a r waters o f t h e o t h e r two s t r e a m s . I n s e m i n a t i o n t h r o u g h t h r u s t s p r o b a b l y does n o t i n v o l v e c o o p e r a t i o n b y t h e ¥ and a d a  i n t u r b i d w a t e r would p r o b a b l y have a b e t t e r chance o f a p p r o a c h i n g  ¥ unnoticed.  ones.  A l s o , s m a l l e r G dd t h r u s t and d i s p l a y e d more t h a n  Seghers (1973) has e v i d e n c e t h a t s m a l l e r dd  large predators. The  Perhaps s m a l l e r G dd  are b e t t e r at avoiding  can " a f f o r d " t o be more o b v i o u s .  f l u r r y o f a c t i v i t y when s e v e r a l dd  s p i c u o u s , even t h r o u g h  encounter  a  ¥ i s q u i t e con-  t h e t o t a l space o c c u p i e d by a l l t h e f i s h a t one  moment may be l e s s t h a n t h a t o c c u p i e d when a s i n g l e d and ing.  larger  ¥ are i n t e r a c t -  Perhaps t h e group o f f i s h g i v e a s c h o o l i n g e f f e c t , i . e . , make i t  d i f f i c u l t f o r a p r e d a t o r t o s i n g l e out an i n d i v i d u a l f o r a t t a c k .  I t may  a l s o be t h a t t h e r e a r e more eyes w i t h w h i c h t o s p o t a p r e d a t o r , b u t t h e ¥ seems t o have t h e dd 's u n d i v i d e d a t t e n t i o n .  Observations  i n the f i e l d  c o u l d c o n t r i b u t e much i n f o r m a t i o n t o c l a r i f y t h i s p r o b l e m . O t h e r d i f f e r e n c e s emerge i n s i t u a t i o n s where more t h a n one d present.  F o r i n s t a n c e c o n s i d e r t h e a g g r e s s i v e b e h a v i o u r o f P dd  is .  Many  78 P  dd  even have a s l i g h t s p i k e , o u t l i n e d i n b l a c k , on the v e n t r a l edge  o f the c a u d a l  f i n , and  e x h i b i t a "backing" motion r e m i n i s c e n t  t a i l s , where t h e s p i k e f u n c t i o n s i n a g g r e s s i o n between dd 1966). F i g h t i n g i s a s t r a t e g y which has chance o f s u c c e s s f u l i n s e m i n a t i o n . a f i s h v e r y c o n s p i c u o u s , so we among G dd  .  But why  b e l i e v e t h a t we  do P dd  This i s probably .48.  The  can u n d e r s t a n d why  i t i s n o t o f t e n seen  f i g h t so much more t h a n UA  the h i g h e s t r a t i o o f  dd  to  Has  aggression  Seghers found t h a t .  C o u l d the low p r e d a have opened the g a t e s  emerged as a p o p u l a t i o n c o n t r o l d e v i c e i n  ( c f . B r e d e r and C o a t e s , 1932)?  The  t i c s , dominant dd  (1971) f i n d s t h a t the dominant d  who  Though t h e r e a r e no s u c c e s s  e x h i b i t e d t h e i r r a n k s by c h a s i n g o t h e r dd  ( M c A l i s t e r , 1958)  were more i n t e n s e l y c o l o r e d .  i s a c l u e t o the c o l o r polymorphism i n guppy p o p u l a t i o n s As w i t h the g u p p i e s , s i z e was  ness i n t h e l a t t e r two  studies.  dif-  o f a p a i r leaves  ? ? i n b o t h Gambusia h e t e r o c h i r (Warburton et^ a l _ . , 1957)  Appendix 1 ) .  l a t t e r hypo-  g r e a t l y i n f l u e n c e insemination success w i t h i n a  more o f f s p r i n g than the s u b o r d i n a t e .  hurtadoi  UA,  U s i n g d i f f e r e n t g e n e t i c t y p e s , but c o n t r o l l i n g f o r t h e  ferences, Gandolfi  from  I  tested.  S o c i a l s t a t u s may population.  ?  ? $ o f 19 streams w h i c h  and i n c r e a s e d c o m p e t i t i o n between dd  the absence o f p r e d a t i o n t h e s i s can be  dd  v e r y low, w i t h few l a r g e i n d i v i d u a l s .  Seghers checked, and a v e r y dense guppy p o p u l a t i o n .  f o r aggression?  's  I t i s a l s o a b e h a v i o u r w h i c h makes  the r e a s o n f o r sex r a t i o d i f f e r e n c e s : P,1.14, and  P a r i a had  tor pressure  (Hemens,  evolved here t o f u r t h e r a d  can t u r n t o R i v u l u s f o r the answer.  R i v u l u s d e n s i t y i n the P a r i a was  o f sword-  and  Perhaps  statisaway G. competition  (see Chapt 7  not c o r r e l a t e d w i t h  In M o l l i e n e s i a ( = P o e c i l i a )  far  and  aggressive-  latipinna  79  larger  dd  dominated s m a l l e r ones.  Males were more a g g r e s s i v e when  c o u r t i n g , but l e v e l s o f a g g r e s s i o n dropped when s e v e r a l dd o r a t t e m p t i n g c o p u l a t i o n ( P a r z e f a l l , 1969).  were t h r u s t i n g  There seems t o be a s i m i l a r  r e l a t i o n s h i p between c o u r t s h i p and a g g r e s s i o n i n m o l l i e s and ( a l s o see Baerends ejt a l _ . , 1955) . h i e r a r c h i e s i n guppies may  The  guppies  absence o f o b v i o u s s t a b l e dominance  be r e l a t e d t o a c o m p a r a t i v e l y low l e v e l  of  a g g r e s s i o n ( C o l l i n s et_ a l _ . , 1967). C o n t r a r y t o my r e s u l t s and t h o s e o f Henderson ( u n p u b l . ) , F a r r (1972) f i n d s an i n c r e a s e i n d i s p l a y b e h a v i o u r from t h e one d-one ? two dd  -one  ?  t o two dd  -two  ¥$  .  s i t u a t i o n to  I n h i g h e r d e n s i t i e s up t o 15 p a i r s ,  d i s p l a y s p e r i n d i v i d u a l remained c o n s t a n t .  Henderson found a d e c r e a s e  in  reproductive a c t i v i t y at higher d e n s i t i e s .  I b e l i e v e these d i f f e r e n c e s  emphasize t h e need t o examine and compare p o p u l a t i o n s o r i g i n a t i n g from different ecological  circumstances.  R e s u l t s o f the c o m p e t i t i o n experiments  suggest t h a t G dd  t h e i r b e h a v i o u r r e l a t i v e l y l i t t l e i n the p r e s e n c e  of other  much o f t h e e v o l u t i o n o f t h e b r i g h t e r c o l o r s i n P and UA p l a i n e d by i n t e r in:/6hapterx4e::  :  c o m p e t i t i o n (see Chapts.  6 § 7) .  dd  have p a r t i c u l a r l y e f f e c t i v e  G  dd  .  Perhaps  can be  ex-  In a d d i t i o n , r e s u l t s  and E x p e r i m e n t 9 i n t h e n e x t c h a p t e r s u g g e s t  each r a c e might have a dominant mating s t r a t e g y . f i g h t , and UA  dd  change  dd  t h a t dd  thrust, P  of  dd  displays.  V a r i a b i l i t y w i t h i n p o p u l a t i o n s must be mentioned a l o n g w i t h v a r i a t i o n between p o p u l a t i o n s (see a l s o B a r l o w ,  1961).  F o r most b e h a v i o u r s ,  measurements from i n d i v i d u a l s from a l l the r a c e s o v e r l a p almost To quote L i n d s e y  (1962): "Perhaps,  completely.  w i t h i n a s p e c i e s , each p o p u l a t i o n can  c a r r y i n i t s p o o l o f b u i l t - i n v a r i a b i l i t y the p o t e n t i a l t o a l t e r  rapidly  80  so as t o resemble any o t h e r p o p u l a t i o n , g i v e n o n l y t h e s e l e c t i v e p r e s s u r e s a c t i n g on a l l e l e s a l r e a d y p r e s e n t " . i n which t o a s c e r t a i n t h i s  appropriate The  ideal  way  would be t o t a k e a T r i n i d a d s t r e a m d e v o i d  o f f i s h e s , s c r e e n o f f s e c t i o n s , and i n t r o d u c e v a r i o u s guppy p o p u l a t i o n s and v a r i o u s p r e d a t o r p o p u l a t i o n s i n the a p p r o p r i a t e c o m b i n a t i o n s , controls.  There a r e such streams a v a i l a b l e .  g i c a l sampling  could take p l a c e p e r i o d i c a l l y .  with  B e h a v i o u r a l and morpholoI f T r i n i d a d c o u l d not  u s e d , p r e d a t o r complements c o u l d be added t o l a r g e a q u a r i a (  s e e  Seghers,  1973:176) and o b s e r v a t i o n s c o u l d be made on w h i c h g u p p i e s were most r e a d i l y preyed  upon.  be  81  C h a p t e r 6. A.  The  Consequences o f G e o g r a p h i c I s o l a t i o n  Introduction L i k e most r e s e a r c h e r s w o r k i n g w i t h g e o g r a p h i c a l l y i s o l a t e d  t i o n s , I was  i n t e r e s t e d i n the p o s s i b i l i t y o f occurrence o f r e p r o d u c t i v e  i s o l a t i o n between r a c e s . a by-product races.  popula-  Reproductive  o f the a c c u m u l a t i o n  isolation is first,  presumedly,  o f g e n e t i c changes between d i v e r g i n g  When e f f e c t i v e r e p r o d u c t i v e i s o l a t i o n o c c u r s , r a c e s become s p e c i e s  (Dobzhansky, 1970:  Chpt. 11).  Many b o r d e r l i n e cases between " r a c e s " and  s p e c i e s have been examined by Mayr (1963).  Examples a r e the  descriptive  and e x p e r i m e n t a l s t u d i e s o f r e p r o d u c t i v e i s o l a t i o n between " i n c i p i e n t s p e c i e s " or "semispecies" o f f r u i t f l i e s , undertaken his  students  (see C h a p t e r  7).  In C h a p t e r  by Dobzhansky and  6 I sought t o d e t e r m i n e  e x t e n t d i v e r g e n c e i n c o u r t s h i p b e h a v i o u r o f t h e guppy has e v o l v e d i n v o l v i n g f i s h o f a l l t h r e e r a c e s i n experiments  B.  t o what by  together.  B r e e d i n g between t h e r a c e s A l l p o s s i b l e c r o s s e s between t h e r a c e s  4 virgin  (4 w i l d - c a u g h t  ) produced v i a b l e , f e r t i l e o f f s p r i n g .  The  oVplaced  with  range o f v a r i a t i o n  w i t h i n each r a c e would have made many r e p l i c a t i o n s n e c e s s a r y t o e s t a b l i s h heritability  c o e f f i c i e n t s o f behaviours  f o r the " h y b r i d " o f f s p r i n g .  o f space ( f o r 6 " h y b r i d " groups p l u s 3 n o n - h y b r i d such a b e h a v i o u r a l a n a l y s i s .  Examination  o f o*  more b r i g h t l y c o l o r e d r a c e s l e f t more c o l o r f u l  c o n t r o l groups) p r e c l u d e d  color patterns  t h a t most o f t h e o f f s p r i n g were s i r e d by one <J" .  Lack  suggested  G e n e r a l l y , the  d" o f f s p r i n g .  d"d* o f t h e  In a d d i t i o n  t o the predominance o f Y - l i n k e d c o l o r p a t t e r n s (see Winge, 1922a, b, 1927) , the P oV seemed t o c o n t r i b u t e a l o t o f c o l o r t o t h e i r CJ"  young  82 ( e . g . , LV x P ? F l oV were as b r i g h t as P  d*d* ).  Atz  (1962) found t h a t  r e c i p r o c a l c r o s s e s o f s e v e r a l Xiphophorus s p e c i e s d i d not always p r o d u c e s i m i l a r l y pigmented o f f s p r i n g  (see a l s o K a l l m a n ,  I attempted t o d e t e r m i n e c o m p a r a t i v e  1970b).  r e p r o d u c t i v e success  by comparing c o l o r p a t t e r n s o f p o t e n t i a l f a t h e r s and d V o f each r a c e were p l a c e d w i t h s i x v i r g i n weeks.  The ¥$  d" o f f s p r i n g .  o f a s i n g l e r a c e f o r two  U n f o r t u n a t e l y , space was  method o f f o l l o w i n g d* Individual  one  ?,  p a r e n t a g e by c o l o r phenotype seems  was  not  However, the reasonably  d e l i v e r e d young from more t h a n one <f  t h a t one o*  jars,  i n s u f f i c i e n t and  enough young were r a i s e d to p e r m i t c o n c l u s i o n s t o be drawn.  s u l t s suggested  Six  were then removed t o i n d i v i d u a l q u a r t e r s i n 4 - l i t e r  where t h e y dropped young.  accurate.  of  , but r e -  r e s p o n s i b l e f o r most o f the o f f s p r i n g  (see Hildemann and Wagner, 1954).  of  Further experiments i n t h i s  a r e a c o u l d be i m p o r t a n t i n e l u c i d a t i n g some f a c t o r s o f p o p u l a t i o n s t r u c t u r e as w e l l as i n t e r r a c i a l  competition.  C.  I n t e r - p o p u l a t i o n c o m p e t i t i o n i n c o u r t s h i p (Experiment  1.  Introduction The major q u e s t i o n asked i n t h i s experiment was:  w i t h i t s p a r t i c u l a r combination  The  does one r a c e  o f morphology and b e h a v i o u r  g r e a t e r chance o f r e p r o d u c t i v e s u c c e s s f o r t h e same ¥ ?  9)  stand  ofdV  a  than a n o t h e r r a c e when competing  r e s u l t s are p r e s e n t e d  i n two p a r t s : one  t h e e f f e c t s o f i n t e r r a c i a l c o m p e t i t i o n on the o t h e r c o n c e r n i n g the r e s p o n s e s o f the ¥?  d*d* *s b e h a v i o u r ,  t o the  dV 's  concerning and  behaviour.  the  83 2.  M a t e r i a l s and Methods F o r each t r i a l one d" o f each r a c e , a f t e r an i s o l a t i o n p e r i o d o f  about two days, was i n t r o d u c e d i n t o t h e l o n g aquarium, a r r a n g e d as i l l u s t r a t e d i n F i g . 21. A f t e r t h e d'd* had about t e n minutes o f e x p l o r a t i o n time, a v i r g i n ¥  was i n t r o d u c e d t o them.  Seven  were o b s e r v e d f o r a t o t a l o f 21 independent t r i a l s . minutes o r u n t i l c o p u l a t i o n took p l a c e .  ¥¥ o f each r a c e A t r i a l l a s t e d 30  The CDAT was employed t o r e c o r d  f r e q u e n c y and d u r a t i o n o f b e h a v i o u r s and t h e i d e n t i t y o f t h e a c t o r i n t h e case o f t h e dcf and r e s p o n s e b e h a v i o u r and t h e i d e n t i t y o f i t s e l i c i t o r in  the ¥ .  Male b e h a v i o u r s r e c o r d e d were d i s p l a y , l e a p , t h r u s t , c o p u l a -  t i o n and which f i s h was c l o s e s t t o the ¥ .  In addition; aggression, j e r k s ,  and o t h e r n o t e w o r t h y e v e n t s were spoken i n t o a tape r e c o r d e r .  3.  Results  a.  Male b e h a v i o u r s V e r y i n t e n s e ¥-oriented a c t i v i t y commenced when t h e h i g h l y r e s p o n s i v e )  virgin  ¥ was p r e s e n t e d w i t h p r e v i o u s l y i s o l a t e d  t i o n o c c u r r e d (Gd  1  d'd" .  and UA ¥ ) , however, d e s p i t e t h e ¥¥ 's r e c e p t i v i t y .  r e a s o n was o b v i o u s : as soon as one d" d i s p l a y e d t o a ¥ response, another  O n l y one c o p u l a The  and e l i c i t e d a  d" c l o s e r t o h e r attempted c o p u l a t i o n - - t h e d i s p l a y i n g d"  t h e n r u s h e d toward t h e ¥ and d i s r u p t e d t h e attempt o f t h e o t h e r <J* , w i t h no c o p u l a t i o n e n s u i n g . each  T h i s sequence o f e v e n t s was r e p e a t e d many t i m e s i n  trial. I t appeared  that the dV  showed no r a c i a l d i s c r i m i n a t i o n toward one  a n o t h e r - - t h e y behaved as t h e y would have t o members o f t h e same r a c e .  The  comparison o f r a c e s , lumping a l l t h e ¥¥ , c l o s e l y resembles t h a t o f t h e  84  DITHER FISH  t  J  / , —  \  i s e=  17 era  CLEAR PLEXIGLAS  20 Fig.  cm.  2 1 . E x p e r i m e n t a l s e t - u p f o r e x p e r i m e n t 9.  Three o V , one o f  each r a c e , were p l a c e d i n t h e empty compartment a l o n g w i t h a v i r g i n ? . D i t h e r f i s h were v i s i b l e the  observer's.  t o t h e e x p e r i m e n t a l f i s h on a l l s i d e s b u t  85  three-d"  s i t u a t i o n o f Experiment 8: the f r e q u e n c y and d u r a t i o n o f d i s -  p l a y s d i d not d i f f e r and P dd 22a, b, and (Fig. for  22c).  a l l dd  e) . The  Bouts o f d i s p l a y t e n d e d t o be  as opposed t o 4-16  dd  dd  l o n g e r i n UA dd,  r e l a t i v e l y low f r e q u e n c y o f d i s p l a y s (7-15  p e r i m e n t 1) p r o b a b l y k e p t the  tended t o l e a p l e s s t h a n o t h e r  however  i n 30 minutes  i n 15 minutes f o r a l l s i n g l e oV  a r o s e f r o m t h e v i g o r o f t h e dd  (Fig.  i n Ex-  's p u r s u i t s , w h i c h  moving r a t h e r q u i c k l y and t h e r e b y made i t d i f f i c u l t  t o p o s i t i o n themselves f o r d i s p l a y .  quency o f UA  dd  trials  P,0).  (G,2;  may  The  f o r the  r e l a t i v e l y low d i s p l a y f r e -  be r e l a t e d t o t h e i r p e r f o r m a n c e o f j e r k s i n s i x A l t h o u g h j e r k s are commonly a s s o c i a t e d w i t h s u c c e s s f u l  c o p u l a t i o n , no UA dV  copulated  successfully.  The  j e r k may  be a "consum-  m a t o r y " s o r t o f a c t i v i t y and have a d i m i n i s h i n g e f f e c t on f u r t h e r c o u r t ship.  G  dd  t h r u s t more o f t e n t h a n o t h e r dd  a n a l y s i s o f variance;** F i g . 22d) . t e n t l y c l o s e r t o the The  Males o f any one  Friedman two-way  r a c e were n o t  of aggression  Charges o c c u r r e d  on t h e p a r t o f P d"d"  .  F u r t h e r m o r e , P dd  f o u r t r i a l s , two  iniCloser  involved  engaged i n a n o t h e r a g g r e s s i v e b e h a v i o u r i n  of these w i t h P  charges o c c u r r e d ) .  was  i n o n l y f o u r o f the 21 t r i a l s .  e x a m i n a t i o n o f the d a t a r e v e a l e d t h a t a l l f o u r o f t h e s e t r i a l s P ¥?  consis-  ??•  r e l a t i v e infrequency  t i a l l y puzzling.  (p <.01,  %%  (no o v e r l a p w i t h t r i a l s i n w h i c h  These f i s h pushed t h e i r t a i l s i n a n o t h e r  d 's f a c e ,  an a c t i o n which sometimes p r e c e d e s t a i l - b e a t i n g o r an a t t e m p t e d b i t e , u s u a l l y r e s u l t s i n t h e o t h e r f i s h moving away.  Thus, we  and  f i n d th'at some  P r o b a b i l i t y v a l u e s t h r o u g h o u t t h i s experiment a r o s e from the Friedman two-way a n a l y s i s o f v a r i a n c e , 2df.  86  F i g . 22.  Comparison  o f t h e c o u r t s h i p performed by t h r e e  each r a c e , t o s i n g l e v i r g i n  %% o f a l l  r e p r e s e n t s the b e h a v i o u r o f  dd  order.  races.  from the P, UA,  dd  one o f  Each group o f h i s t o g r a m s and G r a c e s , i n t h a t  P r o b a b i l i t y v a l u e s d e r i v e d from t h e Friedman two-way a n a l y s i s  o f v a r i a n c e appear above the h i s t o g r a m s . histograms.  Sample s i z e s appear on t h e  MEAN DISPLAY FREQUENCY  MEAN DISPLAY DURATION (% TIME OF TRIAL)  MEAN DISPLAY BOUT LENGTH (SEC)  MEAN THRUST FREQUENCY  NUMBER OF TRIALS IN NHICH LEAPS OCCURRED  87  form o f r e c o g n i z a b l e P d P  ¥  a g g r e s s i o n took p l a c e i n s i x o f the seven  t r i a l s and two o f the f o u r t e e n t r i a l s w i t h o t h e r ¥¥  o t h e r a g g r e s s i o n was  f r o m a UA  d  .  i n the p r e s e n c e o f a UA  The  ¥ .  The p o s s i b i l i t y o f some s e l e c t i v i t y t a k i n g p l a c e between prompted t h e e x a m i n a t i o n separately.  V dd  o f the  dd's  behaviour  d i s p l a y e d t o t h e i r own  f i v e o f seven t r i a l s  (p <. 1).  ¥¥  to  dd  G Few  dd  leaped o n l y w i t h P  P  an a f f i n i t y  not show a p r e f e r e n c e ¥¥  to P  ¥¥  (p = ¥¥  ¥¥  .  p dd  tended t o My  (2) i f UA  copulation.  b.  and G  dd  , t h e y showed an a v o i d a n c e o f  score o f success  ( i n s e m i n a t i o n ) c o u l d be o b t a i n e d i n  t h i s e x p e r i m e n t because t h e i n t e n s e c o m p e t i t i o n between t h e dd  a¥  impression  ( F i g . 23e). No c o m p a r a t i v e  ing  ¥¥  ,02; F i g . 23d).  ( F i g . 23a).  between P f i s h , and  f o r t h e i r own  to  ( F i g . 23a, b, and c ) .  t o t h e i r own ¥¥  spend the most time as t h e c l o s e s t d  did  n  Males tended t o e x h i b i t h i g h e r f r e q u e n c i e s ,  t h r u s t more t h a n o t h e r dd  i s t h a t (1) t h e r e was  ¥¥  more than the o t h e r dd i  r a c e , w i t h the e x c e p t i o n o f G dd  l e a p s o c c u r r e d , but P dd  and  ¥¥ o f each r a c e  d u r a t i o n s , and average bout l e n g t h s o f d i s p l a y than o t h e r dd o f t h e i r own  only-  However, i t seems r e a s o n a b l e  t o suggest t h a t the  the g r e a t e s t amount o f c o u r t s h i p b e h a v i o u r has  and r e m a i n i n g  prevented d* e x h i b i t -  c l o s e s t to  the h i g h e s t p r o b a b i l i t y o f s u c c e s s .  Females as r e c i p i e n t s o f d I t seems l i k e l y t h a t dd  behaviours r e c e i v e some cues from ¥¥  t h e i r p r o p e n s i t y t o c o u r t them. virgin  ¥¥  on the  ¥¥'s  than n o n - v i r g i n ¥¥ part i s involved.  Certainly  dd  w h i c h increase:',  a r e much more r e s p o n s i v e  to  , even i f no apparent o v e r t s e x u a l r e s p o n s e Compare the f o l l o w i n g r e s u l t s , where  88  F i g . 23.  Comparison o f t h e c o u r t s h i p p e r f o r m e d by t h r e e  o f each r a c e , t o v i r g i n  %% o f each r a c e .  r e p r e s e n t s t h e b e h a v i o u r o f dd order.  dd , one  Each group o f h i s t o g r a m s  from t h e P, UA, and G r a c e s , i n t h a t  P r o b a b i l i t y v a l u e s d e r i v e d from t h e Friedman two-way a n a l y s i s  o f v a r i a n c e appear above t h e h i s t o g r a m s .  N = 7 f o r each r a c e .  88a  TO P  25  a,  MEAN DISPLAY FREQUENCY  TO UA  TO G  <.l  20  >.2  15  n  10  >.2  5 0  3.5  <.08  3.0  b.  MEAN DISPLAY DURATION (Z TIME OF TRIAL)  2.5 2.0 <.1.9  1.5 1.0  .5 0  >.2  m d <.05  '.19 <.19  MEAN DISPLAY BOUT LENGTH (SEC)  15  -.02  10  d.  MEAN THRUST FREQUENCY  <.2 <.2  <.2  60 50  MEAN TIME CLOSEST TO * (Z TIME OF TRIAL)  40 30 20 10  >o2  >.2  89  a p p l i c a b l e , with the d  c o m p e t i t i o n i n F i g . 23.  P ? ? were c l o s e s t t o P dd  f o r a g r e a t e r p e r c e n t a g e o f t i m e and  g r e a t e r average l e n g t h s o f time than UA and G r e s p e c t i v e l y ; F i g . 24a and b ) . t h e i r own dV  (p = .06 and .05,  Although the other  were c l o s e s t t o  s l i g h t l y more o f t h e t i m e , d i f f e r e n c e s were i n s i g n i f i c a n t .  Both P and G  were approached most c l o s e l y more o f t e n by P and G dd  t h a n were UA  (p = .07 and .06, r e s p e c t i v e l y ; F i g . 2 4 c ) .  Females r e c e i v e d more t h r u s t s from  dd o f t h e i r own r a c e  (p<.02,  2 X ).  However, t h e s e r e s u l t s a r i s e l a r g e l y because G ? ?  more b y t h e i r own dd fewer t h r u s t s from G dd  than o t h e r s (p = . 0 2 ) . UA ? ?  P<*V  t h r u s t more t o a l l  than d i d the other and G ? ?  were t h r u s t a t  tended t o r e c e i v e  (p .= .09; F i g . 24d) .  were t h r u s t a t more by a l l  dd  (p<.01, Friedman, and <.05, K r u s k a l - W a l l i s , r e s p e c t i v e l y ; F i g . 2 4 e ) . Bouts o f d i s p l a y s were r e c e i v e d more from members o f t h e same r a c e 2 t h a n from o t h e r s (p< .01, X ) , b u t c l o s e a s s o c i a t i o n s between d P guppies and d  and ?  G guppies seemed t o account f o r t h i s .  r e c e i v e d l o n g e r d i s p l a y s from P dd c e i v e d s h o r t e r d i s p l a y s from G dd P ??  t h a n d i d UA  ( p < . 0 2 ) , UA  P?? ?? re-  ? ? (p<.02; F i g . 25a).  a l s o got a g r e a t e r p e r c e n t a g e o f d i s p l a y time from  i n c o n t r a s t t o UA other  than o t h e r  and ?  (p = . 0 3 ) ,  ? ? who tended t o get l e s s d i s p l a y t i m e from P dd  than  dd (p = .19; F i g . 2 5 b ) . D i s p l a y f r e q u e n c i e s f o l l o w e d t h e same  pattern ( F i g . 25c). P  r e c e i v e d l e a p s o n l y from P dd  UA ¥$ r e c e i v e d fewer l e a p s from P dd c. Female b e h a v i o u r s  (p = .12) and  (p = .13; F i g . 2 5 d ) .  Female guppies e x h i b i t a r a t h e r s t e r e o t y p e d s e x u a l r e s p o n s e , as  90  Fig.  24.  R e l a t i v e p o s i t i o n s o f f i s h and t h r u s t s r e c e i v e d b y v i r g i n  ¥$  from  dd  o f d i f f e r e n t r a c e s i n c o m p e t i t i o n w i t h one  Each s e t o f h i s t o g r a m s i n that order.  represent a c t i v i t i e s  another.  o f P, UA, and G dd  K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e .  f i r s t s e t o f histograms  i n e. r e p r e s e n t  a n a l y s i s o f variance i s used.  dd  , The  , and Friedman two-way  90a  60  P dV  UA oV  G dV  P = .06  P>.2  P>,2  P = .05  P>.2  P>.2  P- .07  P>.2  P=.06  P = .09  P > .2  P = .02  50 a.  X TIME OF TRIAL WHEN d* AND $ ARE CLOSEST  40 30 20 10 1 5 12  b.  MEAN LENGTH OF TIME d* AND ? REMAIN CLOSEST (SEC)  9 6 3 O 125 100  MEAN NUMBER OF TIMES ? WAS APPROACHED MOST CLOSELY BY d"  75 50 25 0 1 5 12 9  MEAN NUMBER OF THRUSTS RECEIVED  6 3 0 10 .  P<.01  e> MEAN NUMBER OF THRUSTS  6 A  .  2 . 0  TO ALL  FROM ALL dV P<.05  91  F i g . 25. races from  Display behaviours received by v i r g i n ??  of d i f f e r e n t  oV of d i f f e r e n t races i n competition with one  Each set of histograms represent P, UA, and G ?? Kruskal-Wallis one-way a n a l y s i s of variance.  another.  , i n that order.  91a  FROM UA 4<S  FROM G dV  P<02  P< 02  P< .02  P = 03  P = .19  P>.2  P=.19  P>.2  P=13  P>.2  FROM P dV  25 20  MEAN DURATION OF DISPLAY (SEC)  15 10  .5 0 5 4  b.  MEAN % TIME OF TRIAL DISPLAYING  3 2 1 0 25  >=12  20  MEAN DISPLAY FREQUENCY  15 10 5 0 5 4  d.  NUMBER OF TRIALS IN WHICH LEAPS OCCURRED  3 2 1  O  P = .12  92  described by L i l e y (1966).  See Appendix 2.  The occurrence o f the r e -  sponse depends upon a combination o f the p h y s i o l o g i c a l readiness o f the and the motivating c a p a c i t i e s o f the d  , and appears t o be i d e n t i c a l  i n a l l three races. The g l i d e i s the f i r s t response o f a receptive $ t o a d i s p l a y i n g d". Females tended to g l i d e to t h e i r own d'd" i n more t r i a l s than t o others . 2 (p< .1, X ). Upon c l o s e r a n a l y s i s , P ?¥ .tended to g l i d e more to P d'd" (p = .17 ) and l e s s to UA and G d'd" (p = .10 and .09, r e s p e c t i v e l y ) than UA and G  ( F i g . 26a). P ? $  P d'd* (p = .12) and G than d i d the other  tended toward longer bouts o f g l i d i n g to  had longer bouts o f g l i d i n g t o G d'd" (p<.05) ( F i g . 26b). There were tendencies f o r P ? ?  g l i d e f o r a greater t o t a l time to P d'd* to UA dV the  (p = .14), and G  (p = .09), UA $¥  t o g l i d e l e s s t o P dd  to  to g l i d e more  (p = .07) than d i d  other ( F i g . 26c). The subsequent ? responses, arching and wheeling, were infrequent.  Nevertheless, the number o f t r i a l s i n which arches occurred was h i g h e s t 2 with f i s h of the same race (p<.05, X ). P ? ? performed arches and wheels more f o r P dd Fig. d.  than d i d the other ¥? (p = .06 and .03, r e s p e c t i v e l y ;  26d and e ) . Male-female i n t e r a c t i o n The d who e l i c i t e d the f i r s t  ¥ response i n a t r i a l was o f the same  2 race as the ? (p<.01, X ) . An index o f response was formulated by 7 Unless otherwise mentioned, p r o b a b i l i t y values are derived from the Kruskal-Wallis one-way a n a l y s i s o f variance.  93  F i g . 26.  Responses o f v i r g i n  t o oV  of d i f f e r e n t races.  s e t o f h i s t o g r a m s r e p r e s e n t a c t i v i t i e s o f P, UA, and G order.  K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e .  Each  , i n that  93a  TO P  TO UA  TO G  10 8  NUMBER OF TRIALS IN WHICH GLIDES OCCURRED  P = 17  P =.10  P = .09  P = .12  P>.2  P< .05  P = .09  P = .14  6 4 2 O  2.5 2.0  b.  MEAN BOUT LENGTHS 1.5 OF GLIDES (SEC) 1,0  .5 O  .5  P = .07  ,4  MEAN % TIME OF TRIAL GLIDING  .3 .2  -1 O 5 4 .  d.  NUMBER OF TRIALS IN WHICH ARCHES OCCURRED  _LZt  Ll  P= .06  P >.2  P = .03  P>.2  P>.2  3 2 1 O 5 4  NUMBER OF TRIALS IN WHICH WHEELS OCCURRED  3 2 1 O  P=.12  94 d i v i d i n g t h e number o f g l i d e s by the number o f d  displays.  c l e a r t h a t UA  They were a b l e t o  dd have v e r y a t t r a c t i v e d i s p l a y s .  I t seems  e l i c i t more r e s p o n s e s from a l l c o m b i n e d t h a n the o t h e r dd b u t t h i s was (p <.05;  c o u p l e d w i t h t h e g r e a t e r r e s p o n s i v i t y o f UA %%  T a b l e 15a).  than d i d o t h e r  UA  dd  dd , and P dd  t h a n d i d P and UA  UA and G dd <.02,  e l i c i t e d fewer (p = .194 and  dd  G  UA dd  s p o n d i n g t o one a n o t h e r than  and dd  dd evoked fewer  ( p < .039, Friedman  evoked more r e s p o n s e s from UA  respectively).  to a l l  s  dd  e l i c i t e d more responses from UA and G  r e s p e c t i v e l y : Friedman two-way a n a l y s i s . from P  (p < . 0 1 )  <.005, responses  two-way a n a l y s i s ) .  ?? than other  (p< .01  and  were much more s u c c e s s f u l i n r e and  o f o t h e r r a c e s (p <.001; T a b l e  15b).  D.  Female s e l e c t i v i t y The purpose o f t h e f o l l o w i n g e x p e r i m e n t s i s t o examine the s e l e c t i v i -  t y o f the  to  dd  o f d i f f e r e n t races suggested i n the p r e v i o u s e x p e r i -  ment.  Two major problems  the  : (1) e x p e r i e n c e d  $  r e s p o n d so r e a d i l y t o dd  appear i n a t t e m p t i n g t o a s s e s s the r e s p o n s e s r a r e l y respond to t h a t a n y t h i n g but  D e s p i t e t h e s e d i f f i c u l t i e s , I thought t h a t  dd  , and  of  (2) v i r g i n  d -ness i s p r o b a b l y n o t n o t i c e d . might d i s c r i m i n a t e between  i f g i v e n a c h o i c e , even i f t h e i r s e l e c t i o n s were n o t s e x u a l l y m o t i v a t e d (e.g. s c h o o l i n g ) .  E.  C h o i c e T e s t 1 (Experiment  10)  _ I once a c c i d e n t a l l y bent a ? w h i l e t r a n s f e r r i n g h e r t o an aquarium o f v i r g i n s . Almost immediately another 2 began a s e x u a l r e s p o n s e t o t h i s apparently d i s p l a y i n g f i s h . Females do n o t seem t o r e s p o n d t o m o d e l s , hswever ( L i l e y , p e r s . comm.).  95  Table 15. Response indices (# glides/ # displays) for virgin SS with dd of different races in competition with one another.  All a.  dd  All SS  p dd  b.  PSS  UASS  G  .134  .437  .112  P dd  Vkdd  G  .126  .306  .222  PSS  UA SS  G SS  ^185"**- • ^ .130  SS p < .05  dd  .052  p < .01  p < .2  UA dd  .138"""- - ^ . 652"* - , .280  p < .01  G dd  .079  p < .02  P<  .039  .459"  P =  .194  .089""  P <" .005  p < .00?  96 1.  Introduction I gave v i r g i n and e x p e r i e n c e d  with The  d'd* a c h o i c e o f swimming t o one o f t h r e e dd e x p e r i m e n t a l h y p o t h e s i s was  t e n t c h o i c e s o f dd  that  of d i f f e r e n t races.  o f one r a c e would make c o n s i s -  o f one r a c e , n o t n e c e s s a r i l y t h e i r own  H a s k i n s e t a l . , 1961;  2.  deprived o f recent experience  s e l e c t b r i g h t e r d'd"  (recall  ).  M a t e r i a l s and Methods F i r s t , one  maze, t h e n one  j ?  o f each r a c e was  i n t r o d u c e d i n t o the three-way c h o i c e  was p l a c e d b e h i n d c l e a r p l e x i g l a s p a r t i t i o n s , as i l -  l u s t r a t e d i n F i g . 27 (see a l s o F i g . 4 ) . p a r t i t i o n s by a p u l l e y system, and t h e  A f t e r f i v e minutes, I r a i s e d the ? was  free to proceed  to a d  The  £ completed h e r t r i a l when she touched a p a r t i t i o n w i t h a d  it.  I recorded her choice of d  him. Six  A  $  .  behind  and t h e l e n g t h o f t i m e she took t o r e a c h  had f i v e minutes t o complete h e r t r i a l b e f o r e I t e r m i n a t e d i t .  White C l o u d M o u n t a i n minnows s e r v e d as d i t h e r s i n each o f the t h r e e  s i d e compartments o f t h e maze. All rotating saw  t r i a l s were independent.  P o s i t i o n e f f e c t s were c o n t r o l l e d by  d'd" t o d i f f e r e n t arms o f the maze f o r each t r i a l , so t h a t  ??  dd o f a g i v e n r a c e i n each o f the t h r e e arms a p p r o x i m a t e l y e q u a l l y .  Twenty-four time).  G and 23 P v i r g i n s were t e s t e d (no UA were a v a i l a b l e a t t h e  Twelve e x p e r i e n c e d  o f each r a c e , i s o l a t e d from d'd"  (but n o t  from one a n o t h e r ) f o r 28-36 d a y s , were t e s t e d . 3.  Results G e n e r a l o b s e r v a t i o n s o f d i f f e r e n c e s i n b e h a v i o u r between v i r g i n s  and e x p e r i e n c e d  i n t h e maze must f i r s t be n o t e d .  When a v i r g i n  was  97  F i g . 27.  E x p e r i m e n t a l s e t - u p f o r E x p e r i m e n t 10.  The c l e a r p a r t i -  t i o n s s u r r o u n d i n g t h e ? were removed by a p u l l e y system. but t h e o u t e r ones r e p r e s e n t c l e a r p l e x i g l a s .  A l l lines  98  p l a c e d i n t h e maze, she g e n e r a l l y swam around u n t i l she a p p a r e n t l y noticed a d  t h e n swam i m m e d i a t e l y t o him.  In contrast, the experi-  enced  seemed t o t a k e no more n o t i c e o f t h e dd  fish.  F i v e o f t h e e x p e r i e n c e d %% n e v e r r e a c h e d a d  did  than o f the d i t h e r , and t h o s e t h a t  took an average o f 82.9 seconds, compared t o 43.6 seconds f o r t h e  virgins  (p = .00006, Mann-Whitney U t e s t ,  two-tailed).  Females e x h i b i t e d no p r e f e r e n c e s o f . dd . N e i t h e r d i d t h e y show a b i a s i n t h e i r s e l e c t i o n o f arms o f t h e maze.  The b e h a v i o u r o f t h e dd  i n t h i s experiment and t h e n e x t was q u i t e c o n s i s t e n t : a l m o s t a l l o f them swam a t t h e c l e a r p a r t i t i o n , o r i e n t a t i n g t o t h e Experienced  ? $ o f a l l r a c e s demonstrated no d i f f e r e n c e s i n t h e  l e n g t h o f time t a k e n t o r e a c h any r a c e o f  d-.'.  P v i r g i n s also d i d not  d i f f e r , b u t G v i r g i n s tended t o t a k e l e s s time t o r e a c h G dd  (p<.l,  9 K r u s k a l - W a l l i s )„  When t h e d a t a f o r e x p e r i e n c e d  were lumped, a t r e n d  appeared i n t h e d i r e c t i o n o f l e s s t i m e t a k e n t o r e a c h t h e G dd P other ?$  (p< . 1 ) .  (both v i r g i n s and n o n - v i r g i n s ) t o o k l o n g e r t o r e a c h & d-  than  ( v i r g i n s : p< .011, Mann-Whitney U t e s t ; n o n - v i r g i n s : p < . 0 5 ,  Kruskal-Wallis).  I a t t r i b u t e t h i s d i f f e r e n c e t o t h e tendency o f P ? ?  t o f r e e z e near t h e s u b s t r a t e i n u n f a m i l i a r s u r r o u n d i n g s (see S e g h e r s , whereas UA and G f i s h t e n d t o swim about r a p i d l y .  " K r u s k a l - W a l l i s " h e r e a f t e r r e f e r s t o the K r u s k a l - W a l l i s analysis o f variance.  one-way  1973);  99 F.  C h o i c e t e s t 2 (Experiment 11)  1.  Introduction T h i s c h o i c e t e s t was d e s i g n e d t o measure r e l a t i v e l e n g t h o f t i m e  spent near  dV o f the three r a c e s .  I t seemed t h a t t h e h i g h l y e x p l o r a t o r y  c o u l d then make c h o i c e s based on comparison.  The e x p e r i m e n t a l hy-  p o t h e s i s f o r t h e e x p e r i e n c e d *¥ was t h a t a r a c e o f $ would spend f e r e n t amounts o f time c l o s e t o d*d* o f d i f f e r e n t r a c e s . two p o s s i b i l i t i e s were advanced: r a c e , and (2)  (1)  dif-  For the v i r g i n s ,  would p r e f e r  d V o f t h e i r own  would p r e f e r t h e r a c e s w h i c h appear  brighter to the  human eye (P and UA) o v e r t h e d u l l e r one ( G ) . 2.  M a t e r i a l s and Methods The maze was a r r a n g e d as i l l u s t r a t e d i n F i g . 28.  employed.  D i t h e r f i s h were  Males were i n t r o d u c e d and t h e i r p o s i t i o n s changed between  t r i a l s as i n t h e p r e v i o u s e x p e r i m e n t .  One  * was i n t r o d u c e d i n t o t h e  c e n t e r o f t h e maze and a s t o p w a t c h began when she began moving. thus begun, l a s t e d t e n m i n u t e s .  The t i m e t h e $  Each  s p e n t n e a r each  trial,  d" began  when she made c o n t a c t w i t h t h e p a r t i t i o n b e h i n d w h i c h he swam, and ended when she swam out o f h i s a r e a (see F i g . 2 8 ) . I n t h i s way, t o t a l t i m e spent w i t h each d" and number o f approaches The same e x p e r i e n c e d now i s o l a t e d from ment.  t o each d" were r e c o r d e d .  were used as i n t h e p r e v i o u s e x p e r i m e n t ,  d V f o r 37-41 d a y s , w i t h t h e e x c e p t i o n o f t h a t e x p e r i -  Some o f t h e v i r g i n s t e s t e d p r e v i o u s l y p a r t i c i p a t e d i n t h i s  ment, w i t h t h e a d d i t i o n o f new UA v i r g i n s . v i r g i n s o f each r a c e were used.  experi-  Twelve v i r g i n s and 12 non-  100  Fig. 28.  Experimental set-up f o r Experiment 11.  delimit a a* s "area". ?  plexiglas.  The dashed lines  A l l lines but the outer ones represent clear  101  3.  Results Most f i s h swam up t o each d  b e f o r e c h o o s i n g one a second t i m e .  As i n E x p e r i m e n t 10, t h e v i r g i n s were m a r k e d l y more r e s p o n s i v e t o t h e dd  . They made more approaches t o t h e dd and spent more t i m e i n  t h e i r areas t h a n t h e n o n - v i r g i n s (p = .008 and .034, r e s p e c t i v e l y ; MannWhitney U t e s t ) . No v i r g i n  Females showed no p o s i t i o n a l b i a s e s . showed d i f f e r e n c e s i n a c t i v i t y , measured b y number o f  approaches, but the experienced P $$  d i d ( p < .05, K r u s k a l - W a l l i s ) , w i t h  b e i n g l e a s t a c t i v e (P-UA: p = .142; P-G: p = .007; Mann-Whitney U  test). F i g . 29 r e v e a l s t h a t e x p e r i e n c e d o f any r a c e , w i t h one e x c e p t i o n . P  showed no p r e f e r e n c e s f o r dd  P a i r s c o m p a r i s o n was p e r m i s s i b l e f o r  ? ? ( p < . 0 1 , Friedman two-way a n a l y s i s o f v a r i a n c e ) , where t h e y  spent  l o n g e r average t i m e s w i t h UA dd t h a n t h e i r own (p <.02, W i l c o x o n ) . Virgin  $ ? , on t h e o t h e r h a n d , e x h i b i t e d d i s t i n c t p r e f e r e n c e s  ( p < .01,  2 X , 1 d f ) as i n d i c a t e d b y t h e number o f t r i a l s i n w h i c h most and s p e n t most t i m e w i t h d V s e l e c t e d t h e i r own d'd*  o f t h e i r own r a c e .  i n p a i r s comparisons,  UA  approached  W h i l e P and G d i d not.  No  showed p r e f e r e n c e s when t h e p a i r s comparison d i d n o t i n c l u d e a d t h e i r race.  of  No e v i d e n c e was found t o s u p p o r t t h e h y p o t h e s i s t h a t  p r e f e r t h e dd b r i g h t e r t o humans. G.  Reactive instances of  1.  Introduction T h i s experiment  (Experiment  12)  was d e s i g n e d w i t h t h e f o l l o w i n g i n mind:  more c o n s p i c u o u s l y c o l o r e d d  s h o u l d be more n o t i c e a b l e t o a ?  (1) a at a  102  F i g . 29.  P r e f e r e n c e s f o r d*d* o f d i f f e r e n t r a c e s by v i r g i n  experienced of  .  Each s e t o f t h r e e h i s t o g r a m s r e p r e s e n t s  o f one r a c e t o P, UA,  and G  oV  , i n that order.  below t h e f i g u r e s show t h e p r o b a b i l i t i e s o f v i r g i n o f r a c e s o t h e r t h a n t h e i r own  by chance ( W i l c o x o n  signed-ranks t e s t , o n e - t a i l e d ) .  each group o f  .  ?*s own  responses boxes  c h o o s i n g d*d* matched-pairs  Under each column t h e  i s made between d"d* o f t h a t r a c e and t h e  The  and  race.  comparison N = 12 f o r  102a  12 ><  u as 14  E>  10  10  or W OS hi  8  8  X o < o  6  6  04 4 ft. ft. <  it  2  SB  <  2  0 i UA  P  VIRGIN 8 * PdV COp  UA  G  0  EXPERIENCED «?  UArfrf  Grfrf  < .01  N.S.  SS  3 OS  N.S .  UA  M  .005  > G  u w w  OS  < u  SS  w  N.S. < .02  300.  ,300  250.  • 250  200  . 200  150  . 150  100  100  50 0  . 50  PA UA  VIRGIN  P  UA  EXPERIENCED 8 ?  _0  103 d i s t a n c e , (2) i n a s s o c i a t i o n w i t h t h e t u r b i d w a t e r o f t h e i r n a t u r a l h a b i t a t , G S S might t a k e l o n g e r t o n o t i c e distances  ( s e e experiment 2 ) , and (3) S S  dd a t r e l a t i v e l y g r e a t might p e r c e i v e t h e i r own  race o f d at a greater distance.  2.  M a t e r i a l s and Methods To ensure t h a t 22  were r e s p o n s i v e , v i r g i n s were u s e d  but o n l y 4 UA were a v a i l a b l e a t t h e time).. A  (25 P, 22 G,  D i t h e r f i s h were  employed.  cf was i n t r o d u c e d b e h i n d a c l e a r p a r t i t i o n i n t h e l o n g t a n k , f o l l o w e d  by a ?  , as i l l u s t r a t e d i n F i g . 30.  A f t e r t h e S c a l m e d , t h e opaque  p a r t i t i o n b l o c k i n g h e r v i e w o f t h e d was removed.  One s t o p w a t c h r e -  corded t h e t i m e from removal o f t h e p a r t i t i o n u n t i l t h e i n a s t r a i g h t l i n e towards t h e d  f  l e n g t h o f t i m e t a k e n by a swimming toward him.  and a n o t h e r s t o p w a t c h r e c o r d e d t h e  S t o reach the  A different d  d's p a r t i t i o n once she began  was used f o r each t r i a l and dd  t h e t h r e e r a c e s were p r e s e n t e d i n a r e g u l a r sequence. t e d i n t h r e e t r i a l s , one w i t h each r a c e o f d . by p l a c i n g  Each  2  of  participa-  O b s e r v e r b i a s was a v o i d e d  S S i n d i v i d u a l l y i n j a r s i n c o n s p i c u o u s l y l a b e l e d and h a v i n g  someone mix t h e j a r s up. testing.  2 began swimming  Thus, I d i d n o t know t h e r a c e o f t h e S  I was  Males were c o n s i s t e n t i n swimming a t t h e p a r t i t i o n between them  and t h e ? , u s u a l l y o r i e n t a t i n g t o h e r .  3.  Results I t was g e n e r a l l y c l e a r when a 2 n o t i c e d a d .  She would  cease  swimming about o r s i t t i n g on t h e bottom and swim r a p i d l y s t r a i g h t toward him.  No d i f f e r e n c e s appeared i n t h e d i s t a n c e s a t which t h e S S r e a c t e d  104  *  i  CLEAR PLEXIGLAS  F i g . 30. Aquarium s e t - u p f o r Experiment behind a c l e a r p l e x i g l a s  12. The d  was c o n f i n e d  p a r t i t i o n on t h e l e f t , and t h e % was r e -  l e a s e d from b e h i n d an opaque p a r t i t i o n on t h e r i g h t . swim b e h i n d t h e e x p e r i m e n t a l  aquarium.  Dither fish  105  to  t h e dd  , e i t h e r between  d i f f e r e n t races w i t h P  ? ? o f d i f f e r e n t r a c e s , o r between dd o f  o f one r a c e  (average = 34.6 cm f o r 79 runs on  , 8 on UA, and 64 on G, each ¥  times).  b e i n g used a maximum o f t h r e e  Females o f one r a c e d i d n o t v a r y e i t h e r i n t h e t i m e t a k e n t o  s t a r t toward t h e d o r i n t h e time t a k e n t o swim t o dd o f t h e d i f f e r e n t populations. I t i s e v i d e n t from t h e l a s t t h r e e e x p e r i m e n t s t h a t v i r g i n P and G r a c e s d i s c r i m i n a t e i n f a v o r o f t h e i r own r a c e o f dd  o f the  , but only  when g i v e n o p p o r t u n i t y f o r c l o s e o b s e r v a t i o n and c o m p a r i s o n . H.  Summary o f t h e female's r e s p o n s e Virgin  ? ? o f t h e P and G r a c e s d i s c r i m i n a t e d i n f a v o r o f dd  of  t h e i r own r a c e s i f t h e y were g i v e n o p p o r t u n i t y f o r c l o s e o b s e r v a t i o n and comparison o f a l l t h r e e r a c e s o f dd w i t h a l l t h r e e r a c e s o f dd o f t h e i r own r a c e .  were d i r e c t e d t o t h e i r own  d i s p l a y s than d i d  whether by i n i t i a l responsiveness to  t e n d e d t o r e s p o n d more t o dd  T h i s was accompanied b y t h e tendency o f dd toward t h e i r own dd when dd  Response i n d i c e s i n d i c a t e d t h a t UA d  I f given opportunity t o i n t e r a c t  a t once, ? ?  more d i s p l a y and c o n t a c t b e h a v i o u r by  .  F i r s t responses  o f each r a c e were p r e s e n t .  responded much more r e a d i l y t o UA  o f other races t o t h e i r  i n n a t e r e c o g n i t i o n (P and G  t o d i s p l a y s (UA  .  to direct  ),  complete f u l l s e x u a l r e s p o n s e s w i t h  dd's  displays.  Thus,  *'* ) , o r by i n c r e a s e d >  o f each r a c e seemed more l i k e l y dd  o f t h e i r own r a c e .  106  C h a p t e r 7.  D i s c u s s i o n o f Geographic  Variation  G e o g r a p h i c v a r i a t i o n has g e n e r a l l y been r e g a r d e d as t h e m a n i f e s t a t i o n o f a d a p t a t i o n a t the p o p u l a t i o n l e v e l .  Geographic b a r r i e r s m a i n t a i n  d i f f e r e n c e s between p o p u l a t i o n s i n d i f f e r e n t e c o l o g i c a l  situations':  whereas l a c k o f p h y s i c a l b a r r i e r s a l l o w l e s s d i s t i n c t and more g r a d u a l d i f f e r e n c e s between p o p u l a t i o n s ( c l i n i a l of  variation).  Numerous a c c o u n t s  g e o g r a p h i c v a r i a t i o n i n c o l o r and c o n s i d e r a b l y fewer o f v a r i a t i o n i n  m a t i n g b e h a v i o u r have appeared  i n the l i t e r a t u r e .  However, few  studies  suggest the s e l e c t i v e agents i n v o l v e d , o r the a d a p t i v e s i g n i f i c a n c e o f these v a r i a t i o n s .  I can do l i t t l e more t h a n add t o t h e l i s t o f o b s e r v a -  t i o n s and s p e c u l a t i o n s on c o l o r v a r i a t i o n .  However, i n f o r m a t i o n about  v a r i a t i o n i n m a t i n g b e h a v i o u r i n t h e guppy, as d i s c u s s e d i n C h a p t e r  5,  adds t o t h e knowledge about t h e e v o l u t i o n o f r a c e s and s p e c i e s .  A.  Geographic v a r i a t i o n i n c o l o r S u b s p e c i e s o f f i e l d mice from e n v i r o n m e n t a l l y s i m i l a r i s l a n d s  i n c o a t c o l o r , a t l e a s t p a r t l y due t o a f o u n d e r e f f e c t  differ  ( B e r r y , 1970).  The  p r e s e n c e o f few ground p r e d a t o r s may have h a s t e n e d the development o f these d i f f e r e n c e s  ( D e l a n y , 1970).  W i t h t h e guppies we have d i s s i m i l a r en-  v i r o n m e n t s , but a p a r a l l e l can be drawn between the o c e a n i c i s l a n d s o f t e r r e s t r i a l a n i m a l s and the land-bounded  " i s l a n d s " o f the guppies.  s u s p e c t t h a t l o w l a n d r i v e r guppies were a n c e s t r a l t o t h e upstream  I popula-  tions.  A e r i a l p r e d a t o r s and t o r n a d o e s c o u l d have been d i s p e r s a l a g e n t s .  Seghers  and I b o t h have the i m p r e s s i o n t h a t the Guayamare r a c e h a r b o r s  c o n s i d e r a b l y more v a r i a t i o n than the P a r i a r a c e , and n o t i n c o l o r a l o n e . In o u r s u p p o r t , Bromley  (unpubl.) has demonstrated  a polymorphism  for  107  m a l a t e dehydrogenase i n G f i s h w h i l e UA and P are monomorphic ( c f . Northcote,  et_  , 1970;  c o l o r and m e r i s t i c d i f f e r e n c e s o f r a i n b o w  t r o u t d i d n o t match l a c t a t e dehydrogenase d i f f e r e n c e s i n s i m i l a r  en-  v i r o n m e n t s above and below f a l l s ) . D e s p i t e t h e l a r g e c o l o r and  c o l o r - p a t t e r n d i f f e r e n c e s between t h e  guppy r a c e s , o c c a s i o n a l males f r o m t h e Guayamare R i v e r l o o k v e r y much l i k e Upper A r i p o o r P a r i a males.  Even r a r e r are UA males w h i c h resemble  G m a l e s , and P males seem n e v e r to appear l i k e members o f t h e UA and races.  Remember t h a t I was  most d i s s i m i l a r r a c e s . two  w o r k i n g w i t h t h r e e o f the  morphologically  A l l t h e r a c e s i n T r i n i d a d are p o l y m o r p h i c ,  are the same, and the e x t e n t o f p o l y m o r p h i s m seems t o v a r y .  and A t z  (1966) f i n d t h a t s p e c i e s o r s u b s p e c i e s  G  no Kallman  o f Xiphophorus w i t h  ex-  t e n s i v e g e o g r a p h i c ranges are more p o l y m o r p h i c t h a n t h o s e w i t h r e s t r i c t e d r a n g e s , b u t remark: "There i s as y e t no answer t o the q u e s t i o n why  cer-  t a i n p a t t e r n s are w i d e s p r e a d w h i l e o t h e r s o c c u r o n l y i n s i n g l e s p e c i e s o r are absent from c e r t a i n p o p u l a t i o n s o f o t h e r s " (p. Hershkovitz  (1968: he r e g a r d s  128).  d i f f e r e n c e s i n c o l o r or c o l o r - p a t t e r n  i n marmoset r a c e s n o n - a d a p t i v e ) t h e o r i z e s t h a t when c e r t a i n mammals become r e l a t i v e l y f r e e o f p r e d a t i o n , c o l o r l o s e s i t s concealment f u n c t i o n s and becomes e i t h e r more a t t r a c t i v e o r n e u t r a l , w h i c h I i n t e r p r e t as s e l e c t i o n f o r i n t r a s p e c i f i c communication o r no s e l e c t i o n a t a l l .  Contrast  t h i s w i t h the drab plumage o f i s l a n d b i r d s which s u f f e r l e s s p r e d a t i o n t h a n r e l a t e d s p e c i e s , o f t e n c o l o r f u l , on the m a i n l a n d ( G r a n t ,  1965).  S u p e r f i c i a l l y i t appears t h a t w i t h marmosets and mice we have a s i t u a t i o n s i m i l a r t o the g u p p i e s - - r e l a x p r e d a t i o n and the c o l o r s emerge. t h e r e i s no good e v i d e n c e t o s u g g e s t t h a t guppy c o l o r has  However,  a direct  link  108  w i t h v u l n e r a b i l i t y t o p r e d a t i o n ( S e g h e r s , 1973; Chpt. 4, s u g g e s t s c a r e f u l r e - e x a m i n a t i o n o f H a s k i n s e t a l . , 1961). F u r t h e r m o r e , t h e r e l a t i v e i m p o r t a n c e o f v i s u a l communication  t o d i f f e r e n t s p e c i e s must be c o n s i d e r e d .  W h i l e v i s i o n appears t o be o f p r i m a r y i m p o r t a n c e t o g u p p i e s , I e x p e c t t h a t o l f a c t i o n , a u d i t i o n , and t a c t i o n a r e more i m p o r t a n t t o m i c e . c o l o r s were v e r y i m p o r t a n t t o i n t r a s p e c i f i c communication  If  t h e y would  e x i s t i n t h e p r e s e n c e o f p r e d a t i o n a l s o ( c f . S e l a n d e r , 1965). Many s p e c i e s o f a n i m a l s e x h i b i t c o l o r o r p a t t e r n v a r i a t i o n between a l l o p a t r i c p o p u l a t i o n s w i t h no apparent c o r r e l a t i o n w i t h t h e s e v e r i t y o f e c o l o g i c a l b a r r i e r s o r d i s t a n c e between them ( e . g . , b u t t e r f l i e s ; Dowdeswell and F o r d , 1953; f r o g s ; V o l p e , 1961; c y p r i n o d o n t f i s h e s : Gordon, 1947; Gordon and Gordon, 1957; Rosen and K a l l m a n , 1969; S c h e e l , 1970; b i r d s : Moreau, 1957; Moreau and S o u t h e r n , 1958; S e l a n d e r , 1964; S i b l e y and S h o r t , 1964; H a l l e_t a l _ . , 1966; V u i l l e u m i e r , 1971). t i o n i s due t o random g e n e t i c d r i f t ?  How much c o l o r v a r i a -  How much i s due t o a d a p t i v e d i f f e r -  ences i n s e x u a l - a g g r e s s i v e communication  i n d i f f e r e n t geographic areas?  How s p e c i f i c a r e r e s p o n s e s between animals i n t h e same p o p u l a t i o n compared w i t h a n i m a l s from d i f f e r e n t p o p u l a t i o n s ? O t h e r cases o f c o l o r v a r i a t i o n e x i s t where t h e i n v e s t i g a t o r s were a b l e t o get some c o r r e l a t i o n w i t h environment  o r even an i n d i c a t i o n o f  s e l e c t i v e v a l u e : p o r p o i s e s - - p r e d a t o r y b e h a v i o u r and more s t r i k i n g c o u n t e r shading i n c l e a r e r waters  ( P e r r i n , 1969; p e r s . comm.); b i r d s - - v e g e t a t i o n  and s u b s t r a t e c o l o r ( D a v i s , 1951; Buchanan, 1964; C h a n i o t , 1970; Barlow and W i l l i a m s , 1971; Johnson  and B r u s h , 1972); q u a n t i t a t i v e a s p e c t s o f  t e r r i t o r i a l d i s p l a y and p o s s i b l y p r e d a t i o n ( C o l l i a s and C o l l i a s ,  1971);  109  absence o f r e l a t e d o r s i m i l a r s p e c i e s cf.  ( S i b l e y , 1961; Mayr, 1963: 318-319;  Cody, 1969); l i z a r d s - - m a t e d i s c r i m i n a t i o n  (McKinney, 1971; b u t con-  t r a s t some b i r d s : S e l a n d e r , 1964; S h o r t , 1965); frogs--amount o f l i g h t on the  f o r e s t f l o o r (Savage and Emerson, 1970): f i s h e s - - a l a r v a l escape r e -  sponse and a p r e d a t o r ( M c P h a i l , 1969); p o t e n t i a l p r e d a t o r s ( F r y e r , 1959; 237-281; McKenzie and K e e n l e y s i d e , 1970); b u t t e r f l i e s - - a c t i v i t y p e r i o d s ( H o v a n i t z , 1953); s p i d e r s - - h e a t a b s o r p t i o n and/or camouflage  ( M u n i z , i n ••  L e v i n s , 1968); s n a i l s - - p r e d a t i o n (Wolda, i 9 6 3 ; 1965; 1969; C u r r e y e t a l . , 1964; Owen, 1965; P a r k i n , 1971; c f . Komai and Emura, 1955; C l a r k e , 1968). The i n c i d e n c e o f g r a y morphs o f t h e p o e c i l i i d B r a c h y r h a p h i s e p i s c o p i i s h i g h e r i n t h e s i l t y w a t e r above a w a t e r f a l l t h a n below i t ( D r e s s i e r , 1971) .  The c o l o r s a r e n o t s e x - l i m i t e d , and males do n o t d i s c r i m i n a t e i n  aggressive or courtship behaviour. predators.  The p a p e r g i v e s no i n f o r m a t i o n about  I t i s t e m p t i n g t o s p e c u l a t e t h a t u n d e r w a t e r v i s i b i l i t y has  been a f a c t o r i n t h e e v o l u t i o n o f t h e B r a c h y r h a p h i s and guppy morphs. S p e c i e s o f temperate f r e s h - w a t e r f i s h e s t e n d t o be d u l l e r i n t u r b i d e n v i r o n ments, b u t I c o u l d f i n d no e v i d e n c e t h a t t h i s i s g e n e t i c . not  Though p r o b a b l y  i m p o r t a n t i n c a m o u f l a g e , the b r i g h t n e s s o f male g u p p i e s c o r r e l a t e s  p o s i t i v e l y w i t h water c l a r i t y . Why have b r i g h t c o l o r s when t h e y cannot be seen?  T h i s q u e s t i o n im-  m e d i a t e l y s u g g e s t s t h e c o n v e r s e : why have b r i g h t c o l o r s when t h e y can be seen?  P l e i o t r o p i s m i s n o t a s a t i s f y i n g answer.  solution i s required.  An a d a p t i v e , f u n c t i o n a l  F o r example, c o n s i d e r B a r t n i k ' s  a l l o p a t r i c s u b s p e c i e s on longnose dace.  (1972) s t u d y o f two  The males o f t h e e a s t e r n sub-  s p e c i e s ( R h i n i c h t h y s c a t a r a c t a e c a t a r a c t a e ) have b r i g h t c r i m s o n n u p t i a l  110 c o l o r a t i o n , which i s absent dulcis).  R.  i n males o f t h e w e s t e r n  subspecies  (R_. c_.  c. c a t a r a c t a e males use the r e d c o l o r a t i o n f o r sex  c r i m i n a t i o n , w h i l e R. c_. d u l c i s males appear t o r e l y m o s t l y on stimuli.  Furthermore,  dis-  tactile  the c o l o r e d s u b s p e c i e s spawns m o s t l y d u r i n g day-  l i g h t , and t h e u n c o l o r e d s u b s p e c i e s spawns a t n i g h t , p o s s i b l y i n r e s p o n s e t o a p r e d a t o r , which i s absent  i n the E a s t .  A l t h o u g h n a i v e guppy females  o f a t l e a s t t h e P and G r a c e s  n a t e i n f a v o r o f males o f t h e i r own  discrimi-  r a c e v i s u a l l y , I cannot r u l e  out  f a c t o r s o t h e r than c o l o r i n t h e i r c h o i c e s ( i n c o n t r a s t t o some b i r d s - Mayr, 1963:  318-319).  H a s k i n s e;t al_. (1961: 387) have t h e i m p r e s s i o n  t h a t i n t r a - m a l e c o m p e t i t i o n i s more i m p o r t a n t i n making more males more a t t r a c t i v e t o f e m a l e s . o f male c o l o r has  Although  conspicuous  I have found t h a t b r i l l i a n c e  l i t t l e t o do w i t h a g g r e s s i o n o r a t t r a c t i v e n e s s t o f e -  m a l e s , I have the i m p r e s s i o n t h a t c o l o r a t i o n i n f l u e n c e s i n t r a - m a l e beh a v i o u r more than male-female b e h a v i o u r , w i t h i n p o p u l a t i o n s . i n comparison, helleri, 1968;  Consider,  t h a t t h e t a i l - s p i k e o f the male s w o r d t a i l , X i p h o p h o r u s  a p p a r e n t l y f u n c t i o n s as a s i g n a l t o o t h e r males o n l y (Hemens,  Franck  and H e n d r i c k s , 1973).  H i g h e r r a n k i n g males have more c o l o r  i n t h e r e l a t e d Gambusia h e t e r o c h i r (Warburton e_t a l _ . , 1957) ( M c A l i s t e r , 1958).  Noble and C u r t i s  (1935) and H a s k i n s  and G_. h u r t a d o i  and H a s k i n s  c o n s i d e r t h e male's b r i g h t c o l o r s t o be i n t i m i d a t i n g d e v i c e s . and Coates (1935) c o u l d n o t a v o i d c o n c l u d i n g t h a t t h e r e was n i t i o n i n g u p p i e s , but t h i s i s now  impossible to accept.  the m a l e - i n t i m i d a t i o n h y p o t h e s i s , H a s k i n s m a t i n g i s p e r f o r m e d by young males who  (1949)  Breder  no sex  recog-  In s u p p o r t  et_ al_. (1961) suggest  of  t h a t most  a r e j u s t b e g i n n i n g t o show c o l o r .  (I would be c a u t i o u s i n e x t e n d i n g t h i s statement  t o a l l guppy p o p u l a t i o n s ,  Ill  however). t o one  F u r t h e r m o r e , i t seems t h a t the b r i g h t e r P and UA males a t t e n d  another  f a r more than G males.  A few cases have been s t u d i e d where h y b r i d zones and i n t r o g r e s s i o n o c c u r between d i f f e r e n t l y c o l o r e d forms w i t h no o b v i o u s correlates  ( e . g . , b i r d s : S h o r t , 1965;  1962; McKinney, 1971; h y b r i d may  Hubbard, 1969;  s a l a m a n d e r s : S t e b b i n s , 1949).  environmental  lizards: Zweifel, An  intermediate  be adapted t o an i n t e r m e d i a t e e c o l o g i c a l s i t u a t i o n  Hagen, 1967).  O p p o r t u n i t i e s f o r e x p l o r i n g these kinds of d i f f e r e n c e s  e x i s t w i t h i n the l a r g e r streams o f T r i n i d a d .  Guppies t e n d t o form  p o p u l a t i o n s w i t h r e l a t i v e l y l i t t l e gene f l o w between p o o l s a l . , 1961;  (e.g.,  sub-  (Haskins et_  S e g h e r s , 1973).  Clines i n morphological  types o f a s p e c i e s can be more o r  less  s t e e p , i n d i c a t i n g r e l a t i v e l y d i f f e r e n t amounts o f gene f l o w , and r e l a t i v e degrees o f d i s c r e t e n e s s o f p o p u l a t i o n s .  Differences i n color  are u s u a l l y r e s p o n s e s t o l o c a l c o n d i t i o n s , and r e p r e s e n t adaptations  ( e . g . , e l e p h a n t shrews: C o r b e t , 1970;  S i b l e y and West, 1959;  Johnston  f r o g s : S c h a a f and S m i t h , 1970).  and S e l a n d e r ,  antipredator  birds: Pitelka,  1964;  Johnston,  1951;  1966;  O t h e r cases e x i s t where the concommitants  o f c l i n a l c o l o r v a r i a t i o n are more o b s c u r e ( e . g . , b i r d s : M i l l e r , Mayr and Stresemann, 1950;  D i c k i n s o n , 1952;  V a u r i e , 1957;  B e r r y and D a v i s , 1970;  Banks, 1964;  thereby  G a l b r a i t h , 1956,  1941;  1969;  f i s h : Hubbs and  Miller,  1965). V a r i a t i o n i n c o l o r i s g e n e r a l l y l i n k e d to c r y p s i s .  Some r e s e a r c h e r s  have c o n s i d e r e d i n t r a s p e c i f i c s i g n a l i n g .  A p o s s i b i l i t y which almost a l l  i n v e s t i g a t o r s have n e g l e c t e d i s m i m i c r y .  Behaviour  differences associated  w i t h g e o g r a p h i c a l c o l o r d i f f e r e n c e s have been found o n l y by M c P h a i l  (1969),  112 C o l l i a s and C o l l i a s  (1971), McKinney (1971), and B a r t n i k  Streams and P i m e n t e l  (1972).  (1961) have s t a t e d , " S e l e c t i o n seldom a c t s on  character without a f f e c t i n g other characters".  The  one  current state of  knowledge l e a d s us t o the c o n c l u s i o n t h a t u n e x p l a i n e d v a r i a t i o n s i n c o l o r are due  l a r g e l y t o p l e i o t r o p i s m s (Dobzhansky, Scudder, p e r s . comms.).  I b e l i e v e t h i s t o be a p r e m a t u r e c o n c l u s i o n because i t e x p l a i n s n o t h i n g . E x p l a n a t i o n s f o r c o l o r v a r i a t i o n s have been sought m a i n l y as mechanisms f o r a g i v e n a n i m a l ' s p r e d a t o r avoidance  adaptive  association with other species, especially  and p r e y c a p t u r e .  The  importance  of colors i n intra-  s p e c i f i c communication, emphasized by an a n i m a l ' s b e h a v i o u r , must be given attention. As I mentioned e a r l i e r , I i n i t i a l l y i n t e n d e d t o s t u d y t h e s i g n a l v a l u e o f guppy c o l o r a t i o n , b u t found t h a t polymorphism i n a d d i t i o n t o g e o g r a p h i c v a r i a t i o n made the p r o b l e m t o o c o m p l i c a t e d .  The  correlations  o f b l a c k markings and b e h a v i o u r , d i s c u s s e d i n A p p e n d i x 1, s u g g e s t t h e r work.  fur-  Perhaps c e r t a i n c o l o r p a t t e r n s a r e l i n k e d q u a n t i t a t i v e l y  with behaviours. tance t o b e g i n 1948; H a s k i n s  C e r t a i n l y enough i s known about guppy c o l o r i n h e r i -  (Winge, 1922a, b, 1923a, 1927, and H a s k i n s , 1951,  1954;  Haskins  1930; Winge and D i t l e v s e n , et^ a K ,  1961;  Haskins  et a l . , 1970) , but the work would appear t o r e q u i r e much space and many hours.  N e v e r t h e l e s s , the guppy seems t o me  a l e a d i n g c a n d i d a t e f o r be-  h a v i o u r g e n e t i c a n a l y s e s , h o p e f u l l y u s i n g c o l o r s as marker genes.  Some  r e l a t e d work on b e h a v i o u r - g e n e t i c s and, s e p a r a t e l y , c o l o r , has begun on s p e c i e s o f the r e l a t e d genus Xiphophorus (Kallman and A t z , 1966; 1970a, b; F r a n c k ,  1970).  Kallman,  113 B.  Geographic  v a r i a t i o n i n mating  behaviour  The p r o b a b l e consequence o f g e o g r a p h i c v a r i a t i o n i n m a t i n g i s s e x u a l i s o l a t i o n and s p e c i a t i o n .  behaviour  T h e r e f o r e , most i n v e s t i g a t o r s  who  have l o o k e d a t r a c i a l d i f f e r e n c e s i n m a t i n g have been s e a r c h i n g f o r s p e c i a t i o n i n a c t i o n , and n o t so much f o r t h e a d a p t i v e s i g n i f i c a n c e o f the d i f f e r e n c e s .  Obviously, r e i n f o r c e d sexual i s o l a t i o n i s adaptive,  but t h e e v o l u t i o n o f d i f f e r e n t m a t i n g p a t t e r n s o r mate c h o i c e s i n i s o l a t e d p o p u l a t i o n s where no secondary t r o p i s m may  c o n t a c t has o c c u r r e d i s p u z z l i n g .  be a r e a s o n f o r many o f t h e cases on r e c o r d , b u t , as mentioned  e a r l i e r , t h i s i s not a s a t i s f a c t o r y explanation to The  Pleio-  me.  r e p o r t o f McKenzie and K e e n l e y s i d e (1970) i s t h e o n l y s t u d y  I came a c r o s s t h a t o u t l i n e d d i r e c t e n v i r o n m e n t a l  correlates to  which  geographic  d i f f e r e n c e s i n m a t i n g b e h a v i o u r , and h e r e t h e s i g n i f i c a n c e o f t h e c o u r t s h i p d i f f e r e n c e s was i n ungulates primates  not c l e a r .  ( E s t e s , 1966;  Intraspecific variation i n social organization K l o p f e r , 1972), r o d e n t s  ( G a r t l a n and B r i a n , 1968; C r o o k , 1970)  the p h y s i c a l and s o c i a l environment,  and Zimmerman, 1961)  1969)  McKinney, 1971)  and from  and i s not n e c e s s a r i l y g e n e t i c . ( M a r l e r and Tamura,  and n e s t i n g s i t e s and n e s t s t r u c t u r e  show no i n d i c a t i o n o f a g e n e t i c b a s i s .  s t u d i e s mate p r e f e r e n c e s  1961),  i s l i k e l y to r e s u l t  S i m i l a r l y , g e o g r a p h i c a l v a r i a t i o n i n some b i r d s o n g s 1964; T h i e l c k e , 1965,  (Anderson,  ( G o d f r e y , 1959)  (Walkinshaw  In other  and c o u r t s h i p (Ferguson,",  1970;  d i f f e r , but environmental c o r r e l a t e s are not e v i d e n t .  I n g e n e r a l , members o f one s u b s p e c i e s o r r a c e o f D r o s o p h i l a succeed muhh more f r e q u e n t l y i n mating w i t h t h e i r own o r r a c e ( S t a l k e r , 1942; Dobzhansky, 1944; Dobzhansky and S t r e i s i n g e r , 1944;  r a t h e r than another  Dobzhansky and Mayr,  Bateman, 1949; S p i e t h , 1951;  subspecies  1944; Dobzhansky  114  and Spassky,  1959; Dobzhansky and M a t h e r , 1961; Ehrman, 1961,  1965; Dobzhansky et^ a l _ . , 1964; Anderson and Ehrman, 1969; T h i s g e n e r a l i t y extends even t o s t r a i n s w i t h i n r a c e s 1962).  L a b o r a t o r y s t u d i e s have demonstrated  l o g i c a l i s o l a t i o n evolves 1958;  Baimai,  1970).  (Carmody et_ a l . ,  p o s s i b i l i t i e s o f how  ( K n i g h t et_ a l _ . , 1956;  Dobzhansky and P a v l o v s k y , 1971;  1964,  etho-  S a n t i b a n e z and Waddington,  a l s o see P o w e l l , 1971).  A l l in all,  e i t h e r D r o s o p h i l a are u n u s u a l a n i m a l s o r i n v e s t i g a t o r s have examined a preponderance o f cases where r a c e s d i f f e r e d i n m a t i n g . m a t i n g system be so s u b j e c t t o v a r i a t i o n ? f r u i t f l i e s as p l i a b l e ?  Why  should a  Are o t h e r c h a r a c t e r i s t i c s  of  I s p l e i o t r o p i s m so o f t e n e x p r e s s e d i n m a t i n g  behaviour? Many s t u d i e s showing m a t i n g d i f f e r e n c e s and p r e f e r e n t i a l mate s e l e c t i o n between c l o s e l y r e l a t e d s p e c i e s have been r e p o r t e d (e.g. c r i c k e t s : Hoy  and P a u l , 1973; D r o s o p h i l a :  f i s h e s : C l a r k e , Aronson, F r a n c k , 1969,  Tan,  1946;  Koopman, 1950, M e r r e l l ,  and Gordon, 1954; H e i n r i c h , 1967; N e l s o n ,  1970; P a r z e f a l l , 1969;  1954; 1968;  G e r a l d , 1971; R u b i n o f f and R u b i n o f f ,  1971; f r o g s : L i t t l e j o h n and L o f t u s - H i l l s , 1968;  L i c h t , 1969;  Gorman, 1969; b i r d s : Ramsay, 1961; Crook, 1964;  Sharpe and  lizards: Johnsgaard,  1966; S m i t h , 1966; D a v i e s , 1970; mammals: B l a i r , 1953; F i s l e r , 1965). many cases e t h o l o g i c a l i s o l a t i n g mechanisms may forcing selection.  In  have e v o l v e d due t o r e i n -  I n o t h e r i n s t a n c e s t h e d i f f e r e n c e s have e v o l v e d i n  a l l o p a t r i c s p e c i e s and t h e s e l e c t i v e agents are not  apparent.  U s u a l l y no s u g g e s t i o n s are g i v e n by i n v e s t i g a t o r s r e g a r d i n g t h e s i g n i f i c a n c e o f d i f f e r e n c e s between p o p u l a t i o n s . v a r i a t i o n i n e n v i r o n m e n t a l parameters  When concommitant  are g i v e n , they are o n l y c o r r e l a t i o n s  and n o t c a u s a l r e l a t i o n s h i p s , as Mayr (1963) s u g g e s t s .  I f we  pursue  115 n e o - D a r w i n i a n t h o u g h t i n an e f f o r t t o s u b s t a n t i a t e the a d a p t i v e cance o f the p h e n o t y p i c  v a r i a t i o n s we  signifi-  s e e , we have the f o l l o w i n g s t a t e -  ment o f Mayr w i t h which t o c o n t e n d : "Geographic v a r i a t i o n as a whole i s adaptive.  I t adapts each p o p u l a t i o n t o the l o c a l i t y i t occupies?*;,.  e v e r , not a l l the p h e n o t y p i c  manifestations of t h i s genotypic  How-  adaptation  a r e n e c e s s a r i l y a d a p t i v e " ( e . g . , Mayr, 1963; Dobzhansky, 1970). Dobzhansky s t a t e d t h a t the o r i g i n o f i s o l a t i o n i s a p r o c e s s ent from the o r i g i n o f o t h e r s p e c i e s d i f f e r e n c e s :  differ-  "Race f o r m a t i o n i s  e s s e n t i a l l y the development o f g e n e t i c p a t t e r n s which a r e adapted t o a d e f i n i t e environment.  S p e c i a t i o n i s a process r e s u l t i n g i n f i x a t i o n  t h e s e p a t t e r n s through  the development o f p h y s i o l o g i c a l i s o l a t i n g mechan-  isms"  (Dobzhansky, 1940).  of  T h i s l a t t e r s e n t e n c e seems f i n e i n t h e case o f  r e i n f o r c e m e n t , b u t i f two p o p u l a t i o n s a r e i s o l a t e d we must l o o k t o e i t h e r t e l e o l o g y o r p l e i o t r o p i s m i f s e l e c t i o n i s not w o r k i n g d i r e c t l y on m a t i n g behaviour  or physiology.  There are no e n v i r o n m e n t a l  f a c t o r s obvious  f l u e n c e guppy female s e l e c t i v i t y o f males.  The  t o me w h i c h s h o u l d i n opportunity f o r reinforcing  s e l e c t i o n seems n o n - e x i s t e n t i n the absence o f s e c o n d a r y c o n t a c t . understand  I could  c h o i c e s b i a s e d toward males w i t h more a t t r a c t i v e c o l o r s o r  d i s p l a y s , i f females had cestral populations  a s i m i l a r r e s p o n s e t h r e s h o l d r e t a i n e d from an-  ( c f . S e l a n d e r , 1969;  type o f s e x u a l s e l e c t i o n may  O o r t m e r s s e n , 1970).  While t h i s  t a k e p l a c e w i t h i n p o p u l a t i o n s , the c h o i c e  G females f o r t h e i r more d u l l y c o l o r e d , l e s s e l a b o r a t e l y p e r f o r m i n g r e f u t e s t h i s hypothesis of Haskins to support  the h y p o t h e s i s  et_ al_. (1961) .  There i s good  of  males  evidence  t h a t male guppy c o u r t s h i p d i f f e r e n c e s a r e  r e s u l t s of d i f f e r e n c e s i n s e l e c t i o n pressure operating i n d i f f e r e n t  the  116 environments,  (see Chpt. 5 ) . The males do n o t appear t o d i s c r i m i n a t e  between females o f d i f f e r e n t p o p u l a t i o n s - - t h e y respond t o females w h i c h r e s p o n d t o them. C o u l d i t be t h a t an a n c e s t r a l p o p u l a t i o n , b e l i e v e d t o be s i m i l a r t o t h e G r a c e , c o n t a i n e d females w h i c h v a r i e d g e n e t i c a l l y i n r e s p o n s e t h r e s h o l d t o d i f f e r e n t males?  C o u l d t h e e v o l u t i o n o f male c o n s p i c u o u s n e s s  i n i s o l a t e d p o p u l a t i o n s have p r e c e d e d female s e l e c t i v i t y ?  Could t h e  females more r e s p o n s i v e t o the t y p e o f male now more p r e v a l e n t i n t h e p o p u l a t i o n have l e f t more o f f s p r i n g , u n t i l most o f t h e f e m a l e s p o s s e s s e d an i n n a t e " t e m p l a t e " o f males o f t h e i r r a c e ?  Or would t h e g e n e t i c p r e -  f e r e n c e s o f females p r o v e i n c o n s e q u e n t i a l w i t h e x p e r i e n c e ?  T h i s can be  tested. C o u l d t h e males t r a n s m i t t h e genes f o r female b i a s toward t h e i r t y p e ? I f t h e a n c e s t r a l r a c e were l i k e t h e Guayamare, perhaps t h e r a r e r , more c o n s p i c u o u s males i n t h e p o p u l a t i o n i n s e m i n a t e d a h i g h e r p r o p o r t i o n o f females t h a n e x p e c t e d due t o an advantage i n i n t r a - m a l e c o m p e t i t i o n (see P a r s o n s , 1967; Ehrman and P e t i t , 1968; Ehrman, 1969, 1970).  I have t h e  i m p r e s s i o n t h a t as many as 10% o f G males f a l l w i t h i n t h e range o f " b r i g h t n e s s " v a r i a t i o n o f UA males.  The male o f f s p r i n g would p o s s i b l y be  a t a d i s a d v a n t a g e i n p r e d a t o r - i n f e s t e d w a t e r s , b u t t h e females would n o t . A b a l a n c e d polymorphism  could r e s u l t .  I n an i s o l a t e d p o p u l a t i o n w i t h r e -  duced p r e d a t i o n , more c o n s p i c u o u s males would i n c r e a s e i n f r e q u e n c y , and more females would c a r r y t h e i r genes. a l l crosses are p o s s i b l e .  This hypothesis i s t e s t a b l e , since  Remember t h a t s e l e c t i o n by f e m a l e s i s j u s t  a c h o i c e must be p r e s e n t e d .  that:  C h o i c e s w i t h i n a p o p u l a t i o n would be a l o n g  a continuum, and genotype changes would e v o l v e  statistically.  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An a n a l y s i s o f g e o g r a p h i c v a r i a t i o n i n t h e a n t i p r e d a t o r a d a p t a t i o n s o f t h e guppy, P o e c i l i a r e t i c u l a t a . Ph.D. T h e s i s . U n i v . B r i t i s h C o l u m b i a . 273 p. S e l a n d e r , R. K. 1964. S p e c i a t i o n i n wrens o f t h e genus Campylorhynchus. U. C. P u b l . Z o o l . 74: 1-259. S e l a n d e r , R..K. 1965. H y b r i d i z a t i o n o f r u f o u s - n a p e d wrens i n C h i a p a s , M e x i c o . Auk 82: 206-214. S h a r p e , R. S., and J o h n s g a r d , P. A. 1966. I n h e r i t a n c e o f b e h a v i o u r a l c h a r a c t e r s i n F- m a l l a r d x p i n t a i l (Anas p l a t y r h y r i c h o s L. x Anas a c u t a L.) h y b r i d s . B e h a v i o u r 27: 259-272, S h o r t , L. L. J r . 1965. H y b r i d i z a t i o n i n t h e f l i c k e r s ( C o l a p t e s ) o f N o r t h America. B u l l . Amer. Mus. Nat. H i s t . 129: 307-420. S i b l e y , C. G. 1961. H y b r i d i z a t i o n and i s o l a t i n g mechanisms, p. 69-87. I n B l a i r , W. F. (ed.) V e r t e b r a t e s p e c i a t i o n . U n i v . Texas P r e s s , Austin. S i b l e y , C. G., and S h o r t , L. L. J r . 1964. H y b r i d i z a t i o n i n t h e o r i o l e s o f t h e Great P l a i n s . Condor 66: 130-150. S i b l e y , C. G., and West, D. A. 1959. H y b r i d i z a t i o n i n t h e r u f o u s - s i d e d towhees o f t h e G r e a t P l a i n s . Auk 79: 326-338. S m i t h , N. G. 1966. E v o l u t i o n o f some A r c t i c g u l l s ( L a r u s ) : an experiment a l s t u d y o f i s o l a t i n g mechanisms. O r n i t h . Monogr. 4: 1-99. S p i e t h , H. T. 1951. M a t i n g b e h a v i o u r and s e x u a l i s o l a t i o n i n t h e D r o s o p h i l a v i r i l i s s p e c i e s group. B e h a v i o u r 31: 105-145.  129  S t a l k e r , H. D. 1942. S e x u a l i s o l a t i o n s t u d i e s i n t h e s p e c i e s Drosophila v i r i l i s . G e n e t i c s 27: 238-257. Stebbins,  complex  R. C. 1949. S p e c i a t i o n i n salamanders o f t h e p l e t h o d o n t i d genus E n s a t i n a . U. C. P u b l . Z o o l . 48: 377-526.  Streams, F. A., and P i m e n t e l , D. 1961. E f f e c t s o f i m m i g r a t i o n on t h e evolution of populations. Amer. N a t u r . 95: 201-210. Tan,  C. C. 1946. G e n e t i c s o f s e x u a l i s o l a t i o n between D r o s o p h i l a p s e u d o o b s c u r a and D r o s o p h i l a p e r s i m i l i s . G e n e t i c s 3 1 : 558573.  T h i e l c k e , G. 1965. Gesangsgeographische V a r i a t i o n des G a r t e n b a u m l a u f e r s ( G e r t h i a b r a c h y d a c t y l a ) i m H i n b l i c k a u f das A r t b i l d u n g s p r o b l e m . Z. T i e r p s y c h o l . 22: 542-566. T h i e l c k e , G. 1969. Geographic v a r i a t i o n i n b i r d v o c a l i z a t i o n s , p. 311339. I n H i n d e , R. A. (ed.) B i r d v o c a l i z a t i o n s . U n i v . P r e s s , Cambridge. V a u r i e , C.  1957. S y s t e m a t i c n o t e s on p a l e a r c t i c b i r d s . No. 30. The C e r t h i i d a e . Amer. Mus. N o v i t a t e s 1855: 1-14.  V o l p e , E. P. 1961. Polymorphism i n anuran p o p u l a t i o n s , p. 221-234. I n B l a i r , W. F. (ed.) V e r t e b r a t e s p e c i a t i o n . U n i v . Texas P r e s s , Austin. V u i l l e u m i e r , F. 1971. G e n e r i c r e l a t i o n s h i p s and s p e c i a t i o n p a t t e r n s i n O c h t h o e c a , M y i d t h e r e t e s , X o l m i s , N e b x o l m i s , A g r i o r n i s and Muscisaxicola. B u l l . Mus. Comp. Z o o l . 141: 181-232. Walkinshaw, L. H., and Zimmerman, D. A. 1961. Range e x p a n s i o n o f t h e Brewer b l a c k b i r d i n e a s t e r n N o r t h A m e r i c a . Condor 6 3 : 162-177. Warburton, B., Hubbs, C , and Hagen, D. W. 1957. R e p r o d u c t i v e b e h a v i o r o f Gambusia h e t e r o c h i r . C o p e i a 1957: 299-300. Winge, 0.  1922a. A p e c u l i a r mode o f i n h e r i t a n c e and i t s c y t o l o g i c a l explanation. J . Genet. 12: 137-144.  Winge, 0.  1922b. O n e - s i d e d m a s c u l i n e and s e x - l i n k e d i n h e r i t a n c e i n L e b i s t e s r e t i c u l a t u s . J . Genet. 12: 145-162.  Winge, 0.  1923. C r o s s i n g - o v e r between t h e X and t h e Y chromosome i n L e b i s t e s . J . Genet. 13: 201-217.  Winge, 0.  1927. The l o c a t i o n o f e i g h t e e n genes i n L e b i s t e s r e t i c u l a t u s . J . Genet. 18: 1-42.  130  Winge, 0.  1930. On t h e o c c u r r e n c e o f XX males i n L e b i s t e s . J . Genet. 23: 69-76.  Winge, 0.,  and D i t l e v s e n , E. 1948. C o l o u r i n h e r i t a n c e and sex d e t e r m i n a t i o n i n L e b i s t e s . Compt. Rend. d. Lab. C a r l s b e r g , S e r . P h y s i o l . 24: 227-248.  Wolda, H.  1963. N a t u r a l p o p u l a t i o n s o f t h e p o l y m o r p h i c l a n d s n a i l Cepaea n e m o r a l i s ( L . ) . F a c t o r s a f f e c t i n g t h e i r s i z e and t h e i r g e n e t i c c o n s t i t u t i o n . A r c h . N e e r l . Z o o l . 15: 381-471.  Wolda, H.  1965. Some p r e l i m i n a r y o b s e r v a t i o n s on t h e d i s t r i b u t i o n o f the v a r i o u s morphs w i t h i n n a t u r a l p o p u l a t i o n s o f t h e p o l y m o r p h i c l a n d s n a i l Cepaea n e m o r a l i s ( L . ) . A r c h . N e e r l . Z o o l . 16: 280-292.  Wolda, H.  1969. S t a b i l i t y o f a s t e e p c l i n e i n morph f r e q u e n c i e s o f t h e s n a i l Cepaea n e m o r a l i s ( L . ) . J . Anim. E c o l . 38: 623-633.  Z w e i f e l , R. G. 1962. A n a l y s i s o f h y b r i d i z a t i o n between two s u b s p e c i e s o f t h e d e s e r t w h i p t a i l l i z a r d , Cnemidophorus t i g r i s . Copeia. 1962: 749-766.  131  A p p e n d i x 1.  Some S p e c u l a t i o n and F i n d i n g s About B l a c k M a r k i n g s o f the Male Guppy  A.  Introduction As c o u r t s h i p p r o c e e d s , t h e b l a c k markings o f t h e d guppy become  more and more p r o m i n e n t , a l t h o u g h no s p e c i a l " a g g r e s s i v e " o r " s e x u a l " melanophore systems were n o t e d ( c f : Baerends e t a l . , 1955).  Because  the b l a c k seems t o be an a r o u s a l s i g n a l , I h y p o t h e s i z e d  dd of t h e  that  r a c e which c o u r t e d most s h o u l d have t h e most b l a c k ; i . e . , P a r i a and Upper A r i p o s h o u l d have more b l a c k t h a n Guayamare.  In addition i t i s  p o s s i b l e t h a t t h e b l a c k markings a l s o have some appeasement f u n c t i o n (see B a r l o w , 1970, When dd  on t h e appeasement and a r o u s a l h y p o t h e s i s  a r e engaged i n a g g r e s s i v e a c t i v i t i e s , v i r t u a l l y a l l t h e b l a c k  on t h e body b l a n c h e s . *  F u r t h e r m o r e , when t h e d  , he i s i n a p o s i t i o n t o be c h a r g e d .  to o t h e r  o f Tinbergen).  dd , and t h e p o s s i b i l i t y  displays i n front o f the  Males do o c c a s i o n a l l y d i s p l a y  remains t h a t t h i s b e h a v i o u r  i s not  j u s t m i s g u i d e d s e x u a l i t y , b u t has a component o f appeasement.  Since P  f i s h a r e much more a g g r e s s i v e than e i t h e r o f t h e o t h e r r a c e s , I p r e d i c t e d t h a t P dd  s h o u l d have t h e most b l a c k .  The h y p o t h e s i z e d  order f o r the  most t o t h e l e a s t amount o f b l a c k p i g m e n t , t h e n , was P--UA--G.  B.  Method o f a n a l y s i s F o r t u n a t e l y , t h e a n e s t h e t i c MS 222 expands melanophores so t h a t an  anesthetized ing  d .  d has much t h e same appearance as a h i g h l y m o t i v a t e d  The s k e t c h e s  court-  o f 32 P, 32 UA, and 30 G dd a s s o c i a t e d w i t h  Experiment 3 were employed t o s c o r e b l a c k markings by e s t i m a t i n g t h e amount  132  o f b l a c k i n each o f e l e v e n s e c t i o n s o f t h e guppy's l a t e r a l (Fig. 31).  0 - 25% o f t h e a r e a b l a c k gave a s c o r e o f 1, 26 - 50% =  2, 51 - 75% = 3, and 76 - 100% = 4 ) .  The use o f s t e n c i l e d o u t l i n e s  o f the same s i z e a u t o m a t i c a l l y c o r r e c t e d s c o r e s f o r s i z e between the r a c e s . t o my C.  surface  discrepancies  An i n d e p e n d e n t a n a l y s i s was p e r f o r m e d i n a d d i t i o n  own because o f t h e s u b j e c t i v i t y i n v o l v e d i n t h e s c o r i n g .  Results The two a n a l y s e s y i e l d e d v i r t u a l l y i d e n t i c a l r e s u l t s .  The  differ-  ences i n t h e amount o f b l a c k were s i g n i f i c a n t as p r e d i c t e d (P had an average s c o r e o f 1.25 p e r body s e c t i o n , UA = 1.08, and G = .93; P t o G c o m p a r i s o n , p <.00023; UA-G, p < . 0 0 5 4 ; P-UA, p < .0329; Mann-Whitney U test).  No c o r r e l a t i o n s e x i s t e d between amount o f b l a c k and t h e dd  who c o u r t e d most w i t h i n a r a c e , however. et a l _ . , (1957) , where dominant dd  I n c o m p a r i s o n , see Warburton  o f Gambusia h e t e r o c h i r may be  n i z e d by i n c r e a s e d i n t e n s i t y o f b l a c k c o l o r a t i o n .  recog-  These r e s u l t s a r e  perhaps n o t as o b j e c t i v e as i s d e s i r a b l e , b u t t h e y do s u g g e s t f u r t h e r e x p e r i m e n t s on t h e v a l u e o f b l a c k as a s i g n a l i n c o u r t s h i p and  aggression.  133  F i g . 31.  A r e a s o f t h e <S guppy's l a t e r a l s u r f a c e used t o q u a n t i f y  black markings.  134 Appendix  2.  A D e s c r i p t i o n o f Guppy B e h a v i o u r P a t t e r n s P e r t a i n i n g to Courtship  The f o l l o w i n g d e s c r i p t i o n s f o l l o w L i l e y A.  (1966).  Male c o u r t s h i p Orientating.  <t a t t e n d s t o t h e  The  ¥ , u s u a l l y watching her.  He g e n e r a l l y f o l l o w s h e r when she moves, and a t t e m p t s t o m a i n t a i n an optimal p o s i t i o n of observation. below, o r l e v e l w i t h t h e  He may  o r i e n t a t e from p o s i t i o n s above,  ? .  Gonopodial s w i n g i n g .  The gonopodium i s moved f o r w a r d on one  o f t h e m i d l i n e , accompanied by an a r c h i n g i n the v e r t i c a l p l a n e o f t e n a sigmoid bending i n the h o r i z o n t a l p l a n e . practically  The  occur at  <S bends h i s body i n t o an S shape and q u i v e r s ,  w i t h the p e c t o r a l f i n s working r a p i d l y .  Often the  T h i s p o s t u r e i s u s u a l l y h e l d f o r a few  Leap.  and  any time d u r i n g c o u r t s h i p .  Sigmoid d i s p l a y .  forth.  T h i s may  side  c/ r o c k s back and  seconds.  As i f s p r i n g - l o a d e d , t h e d* s h o o t s away from t h e %  s t r a i g h t o r c u r v e d p a t h f o r 10 cm o r more.  along a  He t h e n o f t e n resumes o r i e n -  t a t i n g , sometimes a f t e r a s h o r t p e r i o d o f i m m o b i l i t y .  Leaps may  follow  s i g m o i d d i s p l a y s , and are always p r e c e d e d by them. Thrust.  The <f approaches  the ?  from b e h i n d , b e l o w , and s l i g h t l y  t o one s i d e , and b r i n g s h i s gonopodium f o r w a r d and t h r u s t s i t a t t h e  S 's  g e n i t a l o p e n i n g w i t h an upwards and f o r w a r d movement. Jerk.  A <f may  make a s e r i e s o f s h o r t , s h a r p , f o r w a r d and upward  movements w i t h h i s whole body f o l l o w i n g a g o n o p o d i a l c o n t a c t . moves no more t h a n a few mm  H i s body  and he u s u a l l y c o n t i n u e s o r i e n t a t i n g .  135  Copulation  and C o p u l a t i o n  Attempt . W h i l e d i s p l a y i n g , a  i n t o a p o s i t i o n p a r a l l e l t o one  s i d e and  j u s t below the  d" moves  ? .  He  then  s t o p s d i s p l a y i n g , swims t o l i n e h i m s e l f up w i t h h e r , t h e n d i r e c t s h i s gonopodium as i n t h r u s t i n g .  I f he makes c o n t a c t w i t h t h e  p o r e , he r o l l s o v e r on h i s s i d e .  The  p a i r may  $ 's g e n i t a l  swim i n one  o r two  c i r c l e s d e p e n d i n g on t h e d i f f i c u l t y o f g o n o p o d i a l i n s e r t i o n .  small  Contact  i s m a i n t a i n e d f o r o n l y a f r a c t i o n o f a s e c o n d , a f t e r w h i c h the d* away and p e r f o r m s a s e r i e s o f j e r k s . l a t i o n and  The  jumps  o n l y d i f f e r e n c e between copu-  c o p u l a t i o n attempt i s whether o r not i n s e m i n a t i o n  has  taken  place. B.  Male a g o n i s t i c b e h a v i o u r Sparring.  Males l i n e up p a r a l l e l o r a n t i - p a r a l l e l ,  .5 t o 1  cm  a p a r t , w i t h s t r a i g h t , q u i v e r i n g b o d i e s and median f i n s s p r e a d . Tail-beating.  From the s p a r r i n g p o s i t i o n , a <S  toward the o t h e r  C.  d*.  gliding  A receptive %  may  g l i d e i n r e s p o n s e t o a d i s p l a y o r Leap.  % seems r i g i d i n m o t i o n , u s i n g h e r t r u n k  m a i n l y on h e r p e c t o r a l and  caudal  , Arch. Following g l i d i n g the %  fins. may  Her  l i t t l e and r e l y i n g  a t t e n t i o n i s " f i x e d " on t h e d".  s t o p and r a i s e h e r t a i l and head  s l i g h t l y , o f t e n moving the t a i l s l i g h t l y t o one She  tail  Female c o u r t s h i p Glide.  The  lashes h i s  s i d e away f r o m t h e  thus makes her g e n i t a l p o r e q u i t e a c c e s s i b l e t o the  attempts  <£ , who  usually  copulation.  Wheel. copulation  The  $ moves i n a t i g h t c i r c l e , a s s i s t i n g the  attempt.  d  d" .  in a  

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