Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Behavioural adaptations to stream velocity in the guppy, Poecilia reticulata Crow, Richard Thomas 1981-12-31

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
831-UBC_1981_A6_7 C75.pdf [ 5.26MB ]
Metadata
JSON: 831-1.0095144.json
JSON-LD: 831-1.0095144-ld.json
RDF/XML (Pretty): 831-1.0095144-rdf.xml
RDF/JSON: 831-1.0095144-rdf.json
Turtle: 831-1.0095144-turtle.txt
N-Triples: 831-1.0095144-rdf-ntriples.txt
Original Record: 831-1.0095144-source.json
Full Text
831-1.0095144-fulltext.txt
Citation
831-1.0095144.ris

Full Text

BEHAVIOURAL ADAPTATIONS TO STREAM VELOCITY I N THE GUPPY, P O E C I L I A RETICULATA by RICHARD THOMAS CROW B.Sc,  The U n i v e r s i t y o f B r i t i s h C o l u m b i a ,  1976  A THESIS SUBMITTED I N P A R T I A L FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department o f Zoology)  We a c c e p t t h i s t h e s i s a s c o n f o r m i n g to the required  standard  THE U N I V E R S I T Y OF B R I T I S H COLUMBIA J u l y , 1981  C J R i c h a r d Thomas Crow, 1981  In p r e s e n t i n g  this  thesis  in partial  f u l f i l m e n t of the  r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e of B r i t i s h Columbia, I agree that it  freely  the L i b r a r y  a v a i l a b l e f o r r e f e r e n c e and s t u d y .  agree t h a t p e r m i s s i o n for  University  f o r extensive  s c h o l a r l y p u r p o s e s may  for  financial  shall  Zoology  The U n i v e r s i t y o f B r i t i s h 2075 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5 Date  thesis  Columbia  my  It is thesis  n o t be a l l o w e d w i t h o u t my  permission.  Department o f  further  be g r a n t e d by t h e h e a d o f  copying or p u b l i c a t i o n of this  gain  I  make  copying of t h i s  d e p a r t m e n t o r by h i s o r h e r r e p r e s e n t a t i v e s . understood that  shall  written  ii ABSTRACT  Populations of guppies l i v i n g t h e i r "behaviour and morphology.  i n d i f f e r e n t streams v a r y i n  Some p o p u l a t i o n s l i v e i n  f a s t - f l o w i n g streams w h i l e o t h e r s occupy I  slow-flowing water.  h y p o t h e s i z e d t h a t b e h a v i o u r a l d i f f e r e n c e s between the  p o p u l a t i o n s may r e p r e s e n t a d a p t a t i o n s t o s t r e a m I  velocity.  t e s t e d s e v e n p r e d i c t i o n s b a s e d o n t h i s h y p o t h e s i s i n two  experiments.  I n E x p e r i m e n t I , I. e x a m i n e d t h e b e h a v i o u r o f  l a b o r a t o r y r e a r e d guppies descendant  T h e s e g u p p i e s w e r e e x a m i n e d a t .03,  populations. .20  m/sec s t r e a m v e l o c i t i e s .  examined i n s t i l l As p r e d i c t e d ,  w a t e r (.00  «07,  .10,  and  Experiment I I used w i l d - c a u g h t  guppies from f o u r p o p u l a t i o n s .  T h e i r c o u r t s h i p b e h a v i o u r was  m/sec) a n d a t .08  i n Experiment I guppies from  w a t e r showed l ) g r e a t e r c o h e s i o n , 2) and 3)  from three n a t u r a l  m/sec v e l o c i t y . slow-flowing  l e s s a g g r e s s i v e "behaviour,  a g r e a t e r preference f o r the surface r e g i o n of stream  tanks than f a s t water f i s h .  A l s o as p r e d i c t e d , slow water  m a l e s p e r f o r m e d f e w e r s i g m o i d d i s p l a y s "but more t h r u s t s a n d gonopodial swings than f a s t water guppies. of  The p e r s i s t e n c e  these b e h a v i o u r a l d i f f e r e n c e s i n l a b o r a t o r y  raised  descendants o f i s o l a t e d p o p u l a t i o n s demonstrates a genetic c o n t r i b u t i o n to the d i f f e r e n c e s . are  presumably  evolutionary  Therefore the d i f f e r e n c e s  t h e p r o d u c t o f n a t u r a l s e l e c t i o n and r e p r e s e n t  adaptations.  E x p e r i m e n t I a l s o showed t h a t s t r e a m v e l o c i t y a f f e c t s the performance The  directly  o f c o u r t s h i p b e h a v i o u r by males.  f r e q u e n c y o f s i g m o i d d i s p l a y s and g o n o p o d i a l swings  decreased markedly velocity  as s t r e a m v e l o c i t y  increased.  As  stream  i n c r e a s e d , f a s t water males maintained t h e i r  frequency  and d u r a t i o n o f s i g m o i d d i s p l a y s b e t t e r t h a n sl'0wr„water thus p r o v i d i n g evidence f o r "behavioural a d a p t a t i o n to velocity.  The  higher ratio  of sigmoid displays  e x h i b i t e d b y f a s t w a t e r f i s h may to  stream  males,  stream  : thrusts  a l s o r e p r e s e n t an a d a p t a t i o n  velocity.  S t r e a m v e l o c i t y h a d no d i r e c t e f f e c t on g r o u p and a g g r e s s i o n i n t h e g u p p y .  However, i t d i r e c t l y  guppy s t r e a m d e p t h p r e f e r e n c e .  Slow water f i s h  cohesion affected  could  not  m a i n t a i n p o s i t i o n a t the top o f the stream i n f a s t e r - f l o w i n g w a t e r , whereas f i s h b r e d f r o m an i n t e r m e d i a t e s t r e a m p o p u l a t i o n w e r e a b l e t o do s o . the  bottom  of the stream  velocity  F a s t water f i s h always  bed.  I n E x p e r i m e n t I I w i l d - c a u g h t f i s h f r o m f a s t and f l o w i n g s t r e a m s were t e s t e d t o g e t h e r i n two A g a i n , as p r e d i c t e d ,  stream  slow-  conditions.  slow water f i s h performed fewer sigmoid  d i s p l a y s b u t more t h r u s t s and g o n o p o d i a l s w i n g s t h a n water f i s h .  Because  obtained.  I  on  courtship  D u r i n g the experiment males  p r e f e r r e d t o c o u r t f e m a l e s f r o m t h e i r own p r e f e r e n c e s may  fast  o f the slow v e l o c i t y used d u r i n g the  e x p e r i m e n t , no e f f e c t o f a f a s t s t r e a m v e l o c i t y b e h a v i o u r was  preferred  represent p a r t i a l  generally  population.  These  i s o l a t i n g mechanisms.  c o n c l u d e d t h a t d i f f e r e n c e s b e t w e e n guppy p o p u l a t i o n s  i n c o u r t s h i p b e h a v i o u r and  stream depth preference r e p r e s e n t  adaptations to d i f f e r e n t stream v e l o c i t i e s . i s t h e r e f o r e p r e s u m e d t o have b e e n one  Stream  velocity  of several environmental  f a c t o r s t h a t i n t e r a c t e d t o shape t h e g u p p y ' s p r e s e n t b e h a v i o u r .  iv TABLE OF CONTENTS Page Abstract  -  List  of Tables  List  of Figures  ;  i i v i  viii  Acknowledgements  •  ix  Chapter I. II.  Introduction  1  Guppy C o u r t s h i p B e h a v i o u r  and N a t u r a l E n v i r o n m e n t  R e p r o d u c t i v e B i o l o g y and C o u r t s h i p B e h a v i o u r  .  in  t h e Guppy.  8  The E n v i r o n m e n t III.  10  o f t h e Guppy  Stock C o l l e c t i n g , F i e l d Observations,  and  G e n e r a l Methods  lk  C o l l e c t i n g Stocks  1>  F i e l d Observations  16  Maintaining Stocks  17  The  18  Stream Tanks  20  Recording of Observations IV.  8  Experiment  I  : The  S o c i a l Behaviour  o f P.  reticulata  P o p u l a t i o n s at D i f f e r e n t Water V e l o c i t i e s  ....  21  Introduction  21  M a t e r i a l s and M e t h o d s  22  Statistical  2k  Treatment of Data  R e s u l t s and D i s c u s s i o n  25  Stream Depth L o c a t i o n  25  Index  30  of Cohesion  Male A g g r e s s i o n  .-  33  V.  Courtship Behaviour  Patterns  Page 3^  Thrusts  Displays  36  and Sigmoid  Gonopodial Swings.  k6  Copulation Attempts  50  Summary o f R e s u l t s  52  E x p e r i m e n t I I : M a l e P. r e t i c u l a t a C o u r t s h i p B e h a v i o u r and Mate P r e f e r e n c e i n S t i l l and F l o w i n g Water C o n d i t i o n s  55  Introduction  55  M a t e r i a l s and Methods  57  S t a t i s t i c a l Treatment o f the Data  60  R e s u l t s and D i s c u s s i o n  6l  Thrusts  and Sigmoid  .61  Displays  Gonopodial Swings . . . . . . . . . . . . . . .  67  Side-switches, Leaps, Copulation Attempts, Copulations  69  C o u r t s h i p B o u t s a n d t h e Number o f P a t t e r n s p e r C o u r t s h i p Bout Mate P r e f e r e n c e  and  Behaviour  7^4-  o f Males  77  Summary o f R e s u l t s VI.  79  General Discussion The E v o l u t i o n o:f B e h a v i o u r P. r e t i c u l a t a  71  and M o r p h o l o g y i n  Literature Cited  . . . . . .  79 $k 98  Appendix C o r r e l a t i o n s between Male S i z e and C o u r t s h i p Behaviour Patterns C o r r e l a t i o n s between C o u r t s h i p Patterns  Behaviour  98 103  vi LIST  OF TABLES  Table  Page  I. C l a s s i f i c a t i o n a n d p h y s i c a l f e a t u r e s o f s t r e a m s i n T r i n i d a d . .«  12  II.  Comparison o f "group depth" f o r each s t o c k a t d i f f e r e n t stream v e l o c i t i e s  27  III.  Comparison o f "group depth" between s t o c k s a t d i f f e r e n t stream v e l o c i t i e s  29  IV. C o m p a r i s o n o f " I n d e x o f C o h e s i o n " between, s t o c k s at d i f f e r e n t stream v e l o c i t i e s . . . .  32  V. C o m p a r i s o n o f M a l e A g g r e s s i o n a t d i f f e r e n t stream v e l o c i t i e s  35  V I . C o m p a r i s o n o f number o f T h r u s t s , S i g m o i d D i s p l a y s , and t h e r a t i o o f S i g m o i d D i s p l a y s : T h r u s t s f o r each s t o c k a t d i f f e r e n t stream velocities. VII.  VIII.  38  C o m p a r i s o n o f number o f T h r u s t s , S i g m o i d D i s p l a y s and t h e r a t i o o f S i g m o i d D i s p l a y s : T h r u s t s between s t o c k s a t d i f f e r e n t v e l o c i t i e s .  39  Mean number a n d d u r a t i o n o f S i g m o i d D i s p l a y s a t f o u r stream v e l o c i t i e s  ^5  I X . C o m p a r i s o n o f number o f G o n o p o d i a l S w i n g s performed a t d i f f e r e n t stream v e l o c i t i e s f o r each s t o c k  . ^-8  X. C o m p a r i s o n o f number o f G o n o p o d i a l S w i n g s between s t o c k s a t d i f f e r e n t stream v e l o c i t i e s .  ^9  Mean number o f C o p u l a t i o n A t t e m p t s a n d ;,p percentage o f Sigmoid D i s p l a y s f o l l o w e d by Copulation Attempts. . . .  51  Mean number a n d p e r c e n t a g e o f S i g m o i d D i s p l a y s w i t h o r f o l l o w e d by S i d e - s w i t c h e s , L e a p s , and C o p u l a t i o n Attempts f o r males from f o u r s t o c k s i n two s t r e a m c o n d i t i o n s . ,  70  Mean number o f c o u r t s h i p b o u t s p e r m a l e f o r e a c h s t o c k i n two s t r e a m c o n d i t i o n s  72  XI.  XII.  XIII.  XIV. P e r c e n t a g e o f s i g m o i d d i s p l a y s and t h r u s t s p e r f o r m e d b y m a l e s t o f e m a l e s o f t h e i r own or another stock  75  vii-' Table ^XV.  Page Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s between m a l e s i z e and c o u r t s h i p b e h a v i o u r p a t t e r n s and b e t w e e n v a r i o u s c o u r t s h i p b e h a v i o u r patterns. Experiment,;.!*  XVI. Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s between male s i z e and c o u r t s h i p b e h a v i o u r p a t t e r n s and b e t w e e n v a r i o u s c o u r t s h i p behaviour patterns. Experiment I I  101  lQk  viii L I S T OF FIGURES Figure 1.  Page Map o f t h e n o r t h e r n h a l f o f T r i n i d a d , the  major r i v e r systems.  showing •'•15  .  2.  Schematic  3.  "Group depth"  k.  Index o f Cohesion i n r e l a t i o n t o stream • ••• ' , velocity. . . . 31 Male a g g r e s s i o n i n r e l a t i o n t o stream velocity . 3^  5. 6.  19  diagram of stream tank,  . 26  i n r e l a t i o n t o stream v e l o c i t y .  Number o f t h r u s t s i n r e l a t i o n t o s t r e a m velocity  37  Number o f s i g m o i d d i s p l a y s i n r e l a t i o n t o stream v e l o c i t y  4-0  8.  Ratio of sigmoid displays : thrusts i n r e l a t i o n t o stream v e l o c i t y . . . . . . .  . • . kl  9.  Number o f g o n o p o d i a l s w i n g s i n r e l a t i o n to stream v e l o c i t y  7»  10. 11. 12. 13• 1^.  Number o f t h r u s t s i n r e l a t i o n t o s t r e a m velocity  ^-7 • ...  62  Number o f s i g m o i d d i s p l a y s i n r e l a t i o n t o stream v e l o c i t y  63  Ratio of sigmoid displays : thrusts i n r e l a t i o n t o stream v e l o c i t y  65  Number o f g o n o p o d i a l s w i n g s i n r e l a t i o n t o stream v e l o c i t y . . . . . .  68  P r o p o r t i o n o f c o u r t s h i p b o u t s w i t h one, t w o , a n d t h r e e o r more b e h a v i o u r p a t t e r n s 73  per c o u r t s h i p bout 15«  T o t a l l e n g t h o f males t e s t e d i n Experiment  16.  T o t a l l e n g t h o f m a l e s t e s t e d f o r e a c h s t o c k . . 102  I .  99  ix ACKNOWLEDGEMENTS  I  s i n c e r e l y t h a n kray.s u p e r v i s o r , D r . N.R. L i l e y , f o r  p r o v i d i n g me t h e o p p o r t u n i t y t o w o r k o n t h i s p r o j e c t . him  a n d my r e s e a r c h c o m m i t t e e , D r . J.N.M. S m i t h a n d D r . J.D.  M c P h a i l , f o r comments a n d d i s c u s s i o n o n my r e s e a r c h I  I thank  am a l s o g r a t e f u l t o D r . L i l e y  and D r . Smith f o r  proposal. critically  reading the manuscript. I  t h a n k D r . J . S . Kenny f o r h o s p i t a l i t y  of B i o l o g i c a l  S c i e n c e s , U n i v e r s i t y o f t h e West I n d i e s , T r i n i d a d ,  and  Senator  J. Stollmeyer f o r permission  his  estate.  Mr.  I a n Dube f o r t h e i r h e l p i n c o l l e c t i n g Finally,  raw  i n the Department  I am i n d e b t e d  t o c o l l e c t f i s h on  t o D r . L i l e y , MrsikHenktLuytenf,''. a n d  I t h a n k Ms. L y n d a H i n d  data and f o r h e r constant  fish.  f o r h e l p i n g t o compile  encouragement throughout the  study. T h i s w o r k was s u p p o r t e d Canada O p e r a t i n g  by a N a t i o n a l R e s e a r c h C o u n c i l o f  G r a n t t o D r . L i l e y and a U n i v e r s i t y o f B r i t i s h  Columbia Graduate F e l l o w s h i p t o myself.  1 CHAPTER I  INTRODUCTION  Within a species, individuals vary ability  t o s u r v i v e and r e p r o d u c e .  i n t h e i r behaviour  Those i n d i v i d u a l s  and  best  a d a p t e d t o t h e i r p a r t i c u l a r e n v i r o n m e n t c o n t r i b u t e more o f t h e i r genes t o s u b s e q u e n t e g e n e r a t i o n s . may l i n k s p e c i f i c b e h a v i o u r factors.  Thus, n a t u r a l s e l e c t i o n  patterns to certain ecological  I n t h i s t h e s i s I examine w h e t h e r  individual;'^ish  d e r i v e d from d i f f e r e n t n a t u r a l p o p u l a t i o n s are adapted to a s p e c i f i c e c o l o g i c a l f a c t o r , namely stream To  demonstrate the adaptive  structure or behaviour,  success.  requires assessing reproductive character. impossible  ( o r survival) value  i ti s necessary  contributes to reproductive  velocity.  to demonstrate t h a t i t  Strictly  success  speaking,  this  w i t h and w i t h o u t the  T h i s i s s e l d o m done s i n c e 1) i t i s u s u a l l y to find  two p o p u l a t i o n s d i f f e r i n g i n o n l y one .  c h a r a c t e r a n d 2) i t i s r a r e l y p o s s i b l e t o m e a s u r e success  of a  under n a t u r a l c o n d i t i o n s .  of comparative  and e x p e r i m e n t a l  adaptive value  of behaviour  reproductive  However, t h e combined use  methods c a n d e t e r m i n e t h e  ( s e e H i n d e , 1975)-  In this  a p p r o a c h , c o r r e l a t i o n s a r e made b e t w e e n p o p u l a t i o n d i f f e r e n c e s : and  e c o l o g i c a l v a r i a b l e s i n the environment.  c o r r e l a t i o n s generate and  These  h y p o t h e s e s on t h e observed r e l a t i o n s h i p s  t h e h y p o t h e s e s may be t e s t e d b y f u r t h e r c o m p a r i s o n s o r b y  experiments i n the f i e l d  and l a b o r a t o r y .  2  N a t u r a l p o p u l a t i o n s o f the guppy, P o e c i l i a  reticulata  ( P e t e r s ) , d i s p l a y c o n s i d e r a b l e v a r i a t i o n i n t h e i r morphology and b e h a v i o u r .  T h i s f a c t , a l o n g w i t h the guppy*s s h o r t  g e n e r a t i o n p e r i o d and easy maintenance i n the l a b o r a t o r y , makes i t i d e a l f o r s t u d y i n g the a d a p t i v e v a l u e o f b e h a v i o u r . D i f f e r e n t p o p u l a t i o n s o f t h e guppy were f i r s t s t u d i e d i n d e t a i l i n t h e i r n a t u r a l environment by ( C P . ) H a s k i n s , (E.F.) H a s k i n s , M c L a u g h l i n ,  and H e w i t t (1961).  t h a t p o p u l a t i o n s o f guppies  o c c u p y i n g d i f f e r e n t streams v a r i e d  genetically i n their colour patterns.  They  Since t h i s  found  study,  c o n s i d e r a b l e i n t e r e s t has been shown i n these n a t u r a l populations.  I n t e r - p o p u l a t i o n v a r i a t i o n has been found i n  guppy s i z e , s e x r a t i o , s c h o o l i n g , a n t i p r e d a t o r b e h a v i o u r , male c o u r t s h i p b e h a v i o u r ,  and male a g g r e s s i o n (Seghers, 1973,  197^a, 197^h; B a l l i n , 1973; L i l e y and Seghers, 1975; F a r r , 1975; and Snyder, 1978).  S t u d i e s on the v a r i a t i o n i n male  c o l o u r p a t t e r n s have a l s o c o n t i n u e d ( E n d l e r , 1978, 1980). I n most o f these s t u d i e s t h e i n v e s t i g a t o r s suggest  that  m o r p h o l o g i c a l and b e h a v i o u r 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 o f guppies  are adaptations t o d i f f e r e n t p r e d a t i o n pressures.  L i l e y and Seghers (1975)f  however, suggest  t h a t many o t h e r  f e a t u r e s o f the environment l i k e l y . r e s u l t i n s e l e c t i o n  pressures  w h i c h compete and i n t e r a c t w i t h those due t o p r e d a t i o n . Some p o p u l a t i o n s o f guppies  o c c u r i n f a s t - f l o w i n g mountain  streams w h i l e o t h e r s occupy s l o w - f l o w i n g o r s t a g n a n t T h i s f a c t l e d me t o h y p o t h e s i z e  water.  t h a t d i f f e r e n t p o p u l a t i o n s may  be adapted t o p a r t i c u l a r stream v e l o c i t i e s and, c o n s e q u e n t l y , t h a t stream v e l o c i t y may have a c t e d i n the p a s t as a s e l e c t i o n  3 pressure, p a r t l y moulding the species*  present behaviour.  t e s t t h i s h y p o t h e s i s , I examine the r e l a t i o n s h i p s o c i a l b e h a v i o u r and w a t e r v e l o c i t y . studies,  "between  3?hus, u n l i k e p r e v i o u s  I examine the e f f e c t o f a p h y s i c a l  f a c t o r on t h e  b e h a v i o u r o f d i f f e r e n t guppy p o p u l a t i o n s r a t h e r t h a n t h e of  To  effect  predation. Water v e l o c i t y i s c l o s e l y  fast-flowing  correlated  with turbidity:  waters are almost i n v a r i a b l y c l e a r ,  waters are g e n e r a l l y t u r b i d e x p e r i m e n t s , t u r b i d i t y was  (see Chapter I I I ) .  slow-flowing During  my  k e p t c o n s t a n t and s t r e a m v e l o c i t y  was  manipulated.  I t i s i m p o r t a n t t o r e c o g n i z e , however,  the  s o c i a l behaviour observed i s almost c e r t a i n l y coadapted to  b o t h p r e v a i l i n g f l o w and t u r b i d i t y c o n d i t i o n s ( a s w e l l biotic was  factors  s u c h as p r e d a t i o n ) .  as  courtship behaviour  c h o s e n a s a s o c i a l b e h a v i o u r on w h i c h t o c o n c e n t r a t e d  during t h i s study since f a c t o r s may  Male  that  also  that affect courtship behaviour  d i r e c t l y a f f e c t reproductive success.  The  h y p o t h e s i s t h a t guppy p o p u l a t i o n s a r e a d a p t e d t o  d i f f e r e n t s t r e a m v e l o c i t y and t u r b i d i t y c o n d i t i o n s l e d t o t h e following 1)  predictions: Guppies d e r i v e d from s l o w - f l o w i n g t u r b i d water should  show g r e a t e r c o h e s i o n ( s c h o o l i n g ) t h a n f i s h clear  from  fast-flowing  streams. 2)  S l o w w a t e r g u p p i e s s h o u l d be l e s s a g g r e s s i v e t h a n  f a s t water guppies. 3) top  Guppies  from s l o w - f l o w i n g t u r b i d w a t e r s h o u l d use  o f the w a t e r column  fast-flowing  ( s u r f a c e q r e g i o n ) , whereas f i s h  water s h o u l d remain n e a r the bottom  of the  the  from stream.  k)  Male guppies from t u r b i d s l o w - f l o w i n g water  perform  should  s i g m o i d d i s p l a y s l e s s f r e q u e n t l y b u t t h r u s t s and  g o n o p o d i a l s w i n g s more f r e q u e n t l y t h a n m a l e s f r o m streams.  fast-flowing  ( F o r a d e s c r i p t i o n o f these b e h a v i o u r p a t t e r n s see  Chapter I I . ) 5)  F o r a l l guppy p o p u l a t i o n s t h e f r e q u e n c y o f c o u r t s h i p  behaviour  (sigmoid displays,  should decrease  thrusts,  and g o n o p o d i a l  w i t h i n c r e a s i n g stream v e l o c i t y  swings)  and t h e  f r e q u e n c y o f s i g m o i d d i s p l a y s s h o u l d d e c r e a s e more t h a n t h e frequency of thrusts. 6)  Males  from s l o w - f l o w i n g water  s h o u l d be l e s s a b l e t o  m a i n t a i n t h e i r c o u r t s h i p b e h a v i o u r and stream p o s i t i o n a t h i g h v e l o c i t i e s than f i s h  from f a s t - f l o w i n g streams.  Slow  water  fish  s h o u l d t h e r e f o r e show a g r e a t e r d e c r e a s e  than f a s t  fish  i n t h e i r frequency o f c o u r t s h i p behaviour as stream  water  velocity increases. 7)  At f a s t v e l o c i t i e s the sigmoid d i s p l a y s performed  males from t u r b i d s l o w - f l o w i n g water  s h o u l d be o f s h o r t e r  d u r a t i o n than the d i s p l a y s o f males from f a s t - f l o w i n g  water.  T h e s e p r e d i c t i o n s were t e s t e d i n two e x p e r i m e n t s . first  experiment  stocks o f guppies descendants  by  The  t e s t e d a l l of the p r e d i c t i o n s , u s i n g three containing at least f i f t h  of wild-caught guppies.  generation  These s t o c k s , each  f r o m a d i f f e r e n t n a t u r a l s t r e a m p o p u l a t i o n , were under s i m i l a r s t i l l  water  f o u r stream v e l o c i t i e s .  bred  cultured  conditions before being tested i n Therefore, behavioural differences  f o u n d b e t w e e n s t o c k s s h o u l d n o t be due t o p r i o r e x p o s u r e  to  d i f f e r e n t environmental factors but instead represent genetic  5  d i f f e r e n c e s "between s t o c k s .  I n the second experiment  several  p o p u l a t i o n s o f w i l d - c a u g h t g u p p i e s were u s e d t o t e s t p r e d i c t i o n s k,  5 » a n d 6 u n d e r two s t r e a m c o n d i t i o n s .  In  a d d i t i o n , t h i s e x p e r i m e n t e x a m i n e d m a l e mate p r e f e r e n c e s f o r females from d i f f e r e n t The  populations.  p r e d i c t i o n s were i n p a r t b a s e d on p r e v i o u s s t u d i e s .  I now g i v e a more d e t a i l e d r a t i o n a l e  f o r each.  Prediction 1  assumes t h a t i n t u r b i d w a t e r one m i g h t e x p e c t f i s h close t o g e t h e r f o r communication  t o keep  or to provide protection  f r o m p r e d a t o r s ( a s s u g g e s t e d b y S e g h e r s , 1973.  197kh)•  I t  f o l l o w s t h a t p o p u l a t i o n s w i t h a t e n d e n c y t o s c h o o l s h o u l d be l e s s a g g r e s s i v e t h a n t h o s e w h i c h a r e more s p a c e d o u t ( P r e d i c t i o n 2).  Thus, s t r e a m v e l o c i t y and t u r b i d i t y  should  indirectly  a f f e c t a g g r e s s i o n i n g u p p i e s by a f f e c t i n g s c h o o l i n g b e h a v i o u r . The  t h i r d p r e d i c t i o n (that f a s t water f i s h  the bottom  o f t h e stream)  should remain near  i s b a s e d on t h e a s s u m p t i o n  that  f a s t w a t e r f i s h may n e e d t o r e t a i n v i s u a l c o n t a c t w i t h t h e s t r e a m b e d t o h o l d t h e i r p o s i t i o n a n d make u s e o f t h e d e c e l e r a t i o n of water close to the substrate. hand, by m a i n t a i n i n g a p o s i t i o n i n the w e l l - l i t slow water f i s h o t h e r more  s h o u l d be a s s i s t e d  On t h e o t h e r surface  layer,  i n s c h o o l i n g and f i n d  each  easily.  Males from c l e a r f a s t - f l o w i n g water are p r e d i c t e d to s i g m o i d d i s p l a y more b u t t h r u s t a n d g o n o p o d i a l s w i n g l e s s m a l e s f r o m t u r b i d s l o w - f l o w i n g w a t e r ( P r e d i c t i o n k). (1973) a n d S n y d e r  than  Ballin  (1978) f o u n d t h a t p o p u l a t i o n s o f g u p p i e s  d e m o n s t r a t e d t h e s e d i f f e r e n c e s i n c o u r t s h i p when o b s e r v e d i n s t i l l water.  B a l l i n s p e c u l a t e d t h a t males from t u r b i d  waters  6  may d i s p l a y l e s s f r e q u e n t l y a n d t h r u s t more f r e q u e n t l y  than  those from f a s t - f l o w i n g c l e a r streams p a r t l y as a response t o stream t u r b i d i t y . to  I n h i s view, female guppies are l e s s able  see t h e d i s p l a y s o f m a l e s i n t u r b i d w a t e r .  Therefore, i n  t u r b i d w a t e r males s h o u l d b e n e f i t l e s s from d i s p l a y i n g and more f r o m a t t e m p t i n g c o p u l a t i o n s b y p e r f o r m i n g t h r u s t s .  (Thrusts  represent i n s e m i n a t i o n attempts w i t h o u t the c o o p e r a t i o n o f females, whereas d i s p l a y s o c c a s i o n a l l y e l i c i t  female c o o p e r a t i o n  and t h e r e f o r e r e s u l t i n s u c c e s s f u l i n s e m i n a t i o n more than t h r u s t s  (Kadow, 1 9 5 ^ ;  As s t r e a m v e l o c i t y r e q u i r e d by f i s h  Liley,  1966).)  i n c r e a s e s , more e n e r g y s h o u l d be  t o m a i n t a i n p o s i t i o n i n the stream and t o  perform courtship.  Sigmoid d i s p l a y s , which involve f i n  s p r e a d i n g b y m a l e s and t h e m a i n t e n a n c e o f a p o s i t i o n to  often  perpendicular  females (and thus t o the d i r e c t i o n o f stream f l o w ) ,  be p a r t i c u l a r l y  difficult  t o m a i n t a i n as stream  should  velocity  increases (Prediction 5 ) • P r e d i c t i o n s 6 and 7 a r e o f p a r t i c u l a r importance t o the h y p o t h e s i s t h a t guppy c o u r t s h i p b e h a v i o u r i s a d a p t e d t o s t r e a m velocity.  I f f a s t water males are b e t t e r able t o m a i n t a i n  t h e i r c o u r t s h i p a t h i g h v e l o c i t i e s than males from slowf l o w i n g water i t f o l l o w s t h a t they are b e t t e r adapted t o the f a s t - f l o w i n g water  environment.  B e f o r e p r e s e n t i n g t h e two e x p e r i m e n t s t h a t t e s t t h e s e predictions,  i n Chapter I I I describe the c o u r t s h i p behaviour  p a t t e r n s s t u d i e d d u r i n g t h e e x p e r i m e n t s and p r o v i d e b a c k g r o u n d m a t e r i a l on t h e n a t u r a l e n v i r o n m e n t  o f the' guppy.  d e t a i l s the c o l l e c t i o n o f s t o c k s , f i e l d  Chapter I I I  o b s e r v a t i o n s , and  7 g e n e r a l methods r e l e v a n t t o b o t h e x p e r i m e n t s . ( C h a p t e r IV)  and E x p e r i m e n t  I I ( C h a p t e r V)  Experiment  a r e f o l l o w e d by  g e n e r a l d i s c u s s i o n on t h e e v o l u t i o n o S f m o r p h o l o g y behaviour  i n t h e guppy ( C h a p t e r V I ) .  and  I a  8 CHAPTER I I GUPPY COURTSHIP BEHAVIOUR AND NATURAL ENVIRONMENT Reproductive B i o l o g y and C o u r t s h i p Behaviour i n the Guppy The r e p r o d u c t i v e b i o l o g y o f the guppy i s s i m i l a r to t h a t of other P o e c i l i i d f i s h e s (Breder and Rosen, 1966).  Sexual  dimorphism i s q u i t e marked, the male i s c o n s i d e r a b l y s m a l l e r and more c o l o u r f u l than the female. o v o v i v i p a r o u s and p r o l i f i c ;  P. r e t i c u l a t a i s  i t has a g e n e r a t i o n p e r i o d of about  three months, w i t h females undergoing a w e l l d e f i n e d c y c l e of brood p r o d u c t i o n . Male c o u r t s h i p behaviour c o n s i s t s o f o r i e n t a t i o n to the female, d i s p l a y behaviour and p h y s i c a l c o n t a c t s .  I measured  male c o u r t s h i p b y h r e c o r d i n g the frequency and d u r a t i o n of s e v e r a l c o u r t s h i p behaviour p a t t e r n s .  The f o l l o w i n g b r i e f  d e s c r i p t i o n s of these behaviour p a t t e r n s are based on the d e t a i l e d account i n L i l e y (1966): Gonopodial Swing: The gonopodium, a m o d i f i e d a n a l f i n , i s brought forward to one side o f the m i d - l i n e . The organ then r e t u r n s t o the r e s t p o s i t i o n , the e n t i r e a c t i o n t a k i n g only one or two seconds. Gonopodial swinging may be performed a t p r a c t i c a l l y any stage d u r i n g c o u r t s h i p and while the male i s i n any o r i e n t a t i o n w i t h r e s p e c t to the female. I n t h i s work I r e c o r d e d a l l gonopodial swings i n which the gonopodium was swung h$ degrees or more. Sigmoid D i s p l a y : The male takes up a p o s i t i o n i n f r o n t of or to the s i d e of the female, t w i s t s h i s body i n t o a sigmoid or S-shape i n the h o r i z o n t a l p l a n e , and v i b r a t e s the whole body f o r s e v e r a l seconds. D u r i n g the d i s p l a y the caudal and d o r s a l f i n s may or may not be f u l l y spread.  9 Leap: F o l l o w i n g a s i g m o i d d i s p l a y t h e male may p e r f o r m a l e a p i n w h i c h he s h o o t s away f r o m t h e f e m a l e a l o n g a s t r a i g h t o r curved path. Thrust: The m a l e a p p r o a c h e s t h e f e m a l e f r o m "below a n d "behind, s w i n g s t h e g o n o p o d i u m f o r w a r d , a n d d i r e c t s i t v i g o r o u s l y t o w a r d s t h e f e m a l e ' s g e n i t a l p o r e . The g o n o p o d i u m may o r may n o t make momentary c o n t a c t w i t h the female's opening. C o p u l a t i o n Attempt: The c o p u l a t i o n a t t e m p t i s d i s t i n g u i s h ed f r o m t h e t h r u s t c h i e f l y b y t h e f a c t t h a t i t i s d i r e c t l y preceded by a sigmoid d i s p l a y . I n making a c o p u l a t i o n a t t e m p t t h e m a l e moves, s t i l l d i s p l a y i n g , 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 a n d j u s t b e l o w t h e f e m a l e . From t h i s p o s i t i o n t h e - m a l e t h r u s t s upwards and f o r w a r d s a s i n t h r u s t i n g . Copulation: I f , d u r i n g a c o p u l a t i o n ••attempt c o n t a c t i s made b e t w e e n t h e g o n o p o d i u m a n d t h e f e m a l e ' s g e n i t a l pore then i t i s m a i n t a i n e d f o r a f r a c t i o n o f a second. The m a l e t h e n jumps away a n d p e r f o r m s a s e r i e s o f j e r k s . Jerks: J e r k s may f o l l o w e i t h e r t h r u s t s o r c o p u l a t i o n s a n d a r e s h o r t , s h a r p , f o r w a r d a n d u p w a r d movements i n v o l v i n g t h e whole body. I n P. r e t i c u l a t a i n s e m i n a t i o n o c c u r s a l m o s t e n t i r e l y  during  the recognizable acts o f c o p u l a t i o n which a r e preceded by sigmoid displays.  V e r y o c c a s i o n a l l y , h o w e v e r , t h e more  commonly  o b s e r v e d t h r u s t s may a l s o r e s u l t i n i n s e m i n a t i o n (Kadow, Liley,  195^;  1966).  F o r most s u c c e s s f u l m a t i n g s t h e f e m a l e p l a y s a n a c t i v e r o l e which i n v o l v e s s e v e r a l r e c e p t i v e behaviour patterns. D u r i n g my e x p e r i m e n t s f e m a l e c o u r t s h i p b e h a v i o u r was n o t recorded since females are only r a r e l y observed during receptive periods. receptivity  Liley  (1966)  their  describes the cycle of  i n females and d e t a i l s t h e i r b e h a v i o u r p a t t e r n s .  Aggression or agonistic behaviour occasionally  occurs  b e t w e e n m a l e s d u r i n g c o u r t s h i p a n d h a s b e e n d e s c r i b e d i n some d e t a i l by L i l e y  (1966).  P o p u l a t i o n d i f f e r e n c e s i n male  a g g r e s s i o n were s t u d i e d i n E x p e r i m e n t recorded a l l inter-male attacks. charge  towards  evidence  Poecilia  of  T h e r e i s no  o r n i b b l i n g o c c u r s a n d i n many c a s e s t h e  t o make c o n t a c t .  The E n v i r o n m e n t  tion  I  An a t t a c k c o n s i s t s o f a  t h e f l a n k s o f another male.  that biting  male f a i l s  I (Chapter I V ) .  o f the  GUTOTJV  reticulata  i srestricted  i ni t s natural  t o c o a s t a l areas o f n o r t h e a s t e r n South America  the Caribbean i s l a n d s  (Rosen  and B a i l e y ,  I963)•  distribu-  and a few Within this  r e g i o n , however, i t i s f o u n d i n l a r g e numbers a n d i n a wide range  o f stream environments.  species o n l y those Liley  and Seghers  Among t h e many s t u d i e s o n t h i s  o f H a s k i n s e t a l . (1961), (1975).  Farr  (1975),  Seghers  (l973)i  a n d E n d l e r (1978)  deal  w i t h the b i o l o g y o f the animal i n i t s n a t u r a l environment. A l l of  t h e s e i n v e s t i g a t o r s s t u d i e d t h e guppy on t h e i s l a n d o f  T r i n i d a d , as d i d I . A mountainous c h a i n extends  along northern Trinidad.  The  n o r t h - f a c i n g slopes o f these mountains are d i v i d e d by s e v e r a l r o u g h l y p a r a l l e l streams  emptying  individually  into the  C a r i b b e a n S e a w i t h n o f r e s h - w a t e r c o n n e c t i o n s b e t w e e n them. The  south-facing slopes contain approximately p a r a l l e l  t h a t are connected  streams  i n the lowlands by draining into the  westward-flowing Caroni River.  Most o f these streams  contain  populations of guppies. Since guppies r a r e l y  o c c u r i n t h e o p e n s e a , ''••  p o p u l a t i o n s i n the n o r t h w a r d - f l o w i n g streams isolated  from each  other.  are v i r t u a l l y  P o p u l a t i o n s i n the upper r e g i o n s o f  the  southward-flowing  streams a r e probably  i s o l a t e d s i n c e l ) the upper courses  also  o f these  genetically  streams f l o w i n  deep v a l l e y s a n d a r e w e l l s e p a r a t e d a t a l l s e a s o n s , of these  several  streams c o n t a i n w a t e r f a l l s which l i k e l y a c t as  e f f e c t i v e b a r r i e r s t o upward m i g r a t i o n o f f i s h Seghers,  2)  1975)»  a n d 3) g u p p i e s  remain f i x e d i n t h e i r  l o c a t i o n s o v e r p e r i o d s o f months o r y e a r s I n c o n t r a s t t o these p o p u l a t i o n s , those are probably n o t as g e n e t i c a l l y the upper r e g i o n s o f northward  classified  rivers  I examine f i s h  and southward-flowing  from  streams  The p o p u l a t i o n s s t u d i e d  e c o l o g i c a l c o n d i t i o n s i n which guppies  T r i n i d a d streams.  196l)•  (Haskins e t a l . ,  r e p r e s e n t i s o l a t e d p o p u l a t i o n s from the f u l l  (1973)  stream  i n the lowland  isolated.  as w e l l a s f r o m l o w l a n d r i v e r s .  Seghers  ( L i l e y and  range o f  live.  made q u a n t i t a t i v e e c o l o g i c a l m e a s u r e s o f Based on p h y s i c a l f e a t u r e s , h i s s t r e a m s were  i n t o f o u r c a t e g o r i e s : s p r i n g s , headstreams,  midstreams, and lowland r i v e r s .  Going from s p r i n g s t o lowland  r i v e r s t h e s t r e a m s become w i d e r ,  d e e p e r , w a r m e r , a n d more  turbid.  Stream v e l o c i t y g e n e r a l l y i n c r e a s e s from s p r i n g s  through  headstreams andmidstreams b u t decreases  i n the lowland r i v e r s chemical  (I96I)  composition  and on stream  (Table I ) .  considerably  A d d i t i o n a l i n f o r m a t i o n - on t h e  o f such waters  i sgiven i n Haskins  substrates i n Endler  et a l .  (1978).  In a d d i t i o n t o d i f f e r e n c e s i n the p h y s i c a l features of T r i n i d a d streams, the faunas  there a r e a l s o s t r i k i n g d i f f e r e n c e s between  o f t h e streams.  The s p r i n g s a n d i s o l a t e d  headstreams  commonly c o n t a i n o n l y P. r e t i c u l a t a a n d a s m a l l c y p r i n o d o n t i d , R i v u l u s h a r t i i , .a p r e d a t o r o f t h e g u p p y .  I n contrast, the  Table I .  C l a s s i f i c a t i o n and p h y s i c a l f e a t u r e s o f streams i n T r i n i d a d . M o d i f i e d f r o m S e g h e r s (1973)-  Volume o f Elow (m / s e c )  Temp.  0.11-  0.0085-  24.326.2  3-4  0.06-0.15  0.320.67  0.028-  0.267  24.627.4  2-3  3.0-8.0  0.13-0.20  0.421.18  0.1501.129  30.0  24.3-  2  1  2.0-25.0  1.5-3.0  0.33-  0.563-  26.9-  0-1  2  Number o f Streams Studied  W i d t h (m)  D e p t h (m)  Velocity (m/sec)  Spring  4  0.50-1.0  0.05-0.15  Headstream  7  1.20-5.0  Midstream  5  L o w l a n d R.  3  Stream  0 "1 2 3 4  -  type  0.29  0.40  0.0128  22.50  no shade s m a l l amount o f shade r e s t r i c t e d m a i n l y t o s t r e a m b a n k medium shade (50% c o v e r ) . medium t o dense (75% c o v e r w i t h f e w e x p o s e d p a r t s ) v e r y dense c o v e r w i t h v i r t u a l l y c o m p l e t e s h a d i n g  Shade  a s  29.1  :  'Turbidity 0  •  0-1  0 - always c l e a r 1 - t u r b i d only a f t e r heavy r a i n s 2 - t u r b i d throughout year  b  m i d s t r e a m s a n d l o w l a n d r i v e r s h a v e a s many a s s i x t e e n s p e c i e s of f i s h ,  i n c l u d i n g s e v e r a l l a r g e guppy p r e d a t o r s ( e g . H o p l i a s  malabar.icus. C r e n i c i c h l a a l t a , Aequidens b i m a c u l a t u s and Hemibrycon s p . ) .  (I960, 196^),  Seghers  (1973),  pulcher.  Astvanax  F o r d e t a i l s see Boeseman  and L i l e y and Seghers  (1975).  Guppy p o p u l a t i o n s i n t h e s e d i f f e r e n t e n v i r o n m e n t s c o n s i d e r a b l e v a r i a t i o n i n morphology and b e h a v i o u r . summarized b y L i l e y and Seghers and  (1975),  guppies  exhibit  As  from s p r i n g s  i s o l a t e d h e a d s t r e a m s a r e g e n e r a l l y l a r g e r ' , t h e m a l e s more  b r i g h t l y coloured', and the females a s f o u r t o one.  o u t n u m b e r m a l e s b y a s much  They show r e l a t i v e l y p o o r l y d e v e l o p e d s c h o o l i n g  behaviour and avoidance  responses.  These c h a r a c t e r i s t i c s a r e  a s s o c i a t e d w i t h c l e a r , f a s t - f l o w i n g water, r e l a t i v e l y low t e m p e r a t u r e s , * and than Rivulus.  a v i r t u a l absence o f a q u a t i c p r e d a t o r s o t h e r  I n c o n t r a s t , i n the l o w l a n d r i v e r s ,  small,- the males l e s s b r i g h t l y n e a r one t o one. responses  These g u p p i e s  guppies a r e  c o l o u r e d and sex r a t i o s a r e show v i g o r o u s  avoidance  a n d o f t e n o c c u r i n s m a l l s c h o o l s a l o n g t h e edge o f a  stream o r r i v e r .  Here, guppies  water, high temperatures,  occur i n slow-flowing t u r b i d  a n absence o f shade, and the  presence  o f numerous p r e d a t o r s . The  evolutionary significance  these d i f f e r e n t p h y s i c a l and b i o t i c  of correlations f a c t o r s and the  between observed  v a r i a t i o n i n g u p p y m o r p h o l o g y a n d b e h a v i o u r w i l l be c o n s i d e r e d a t the end o f t h i s t h e s i s (Chapter V I ) .  CHAPTER I I I STOCK COLLECTING, F I E L D OBSERVATIONS, AND Collecting The sites  GENERAL METHODS  Stocks  s t o c k s o f f i s h were c o l l e c t e d i n T r i n i d a d f r o m  ( s e e map,  F i g . 1).  F i s h were c o l l e c t e d f r o m the  f l o w i n g P a r i a s t r e a m a t a p o i n t above a w a t e r f a l l 10-14- m e t e r s high'; f r o m two the  of the  five northward-  barrier,  southward-flowing  streams:  s m a l l P e t i t e Curucaye stream, at a p o i n t c l o s e to i t s  source,  and  from the Upper A r i p o  s e r i e s of f a l l s  3-5  f r o m t h e C a p a r o and  meters high.  region.  collection site The  These r i v e r s l i e i n the  T h e y a r e "both r e l a t i v e l y  f l o w westward, emptying i n t o the G u l f  P a r i a a t t h e C a r o n i Swamp. c a n be  D e t a i l e d i n f o r m a t i o n on  Vancouver.  t r a n s p o r t e d by  R.  I I used wild-caught d u r i n g May  and  Liley fish  from  c o l l e c t e d b y L i l e y and  fine-mesh c i r c u l a r dip nets.  The  r i v e r s , w h i l e h e a d s t f e a m and  field  populations  P.  Experiment H.  Luyten  g u p p i e s were c o l l e c t e d w i t h  Lowland populations  c o l l e c t e d by n e t t i n g f r o m s m a l l s c h o o l s  the  different  and m y s e l f i n J u n e , 1976.  J u n e , 1978.  from p o i n t s across  each  a i r to the l a b o r a t o r y i n  F i s h i n E x p e r i m e n t I were b r e d  c o l l e c t e d "by N.  of  f o u n d i n S e g h e r s (1973)•  s t o c k s w e r e c o l l e c t e d d u r i n g two  e x p e d i t i o n s and  a  F i s h were a l s o c o l l e c t e d  Guayamare r i v e r s .  sugar-cane p l a n t e d lowland l a r g e s t r e a m s and  (= N a r a n j o ) s t r e a m , above  a l o n g the  spring populations  stream beds.  were edges  of  were c o l l e c t e d  F i g u r e 1.  Map o f t h e n o r t h e r n h a l f o f T r i n i d a d , s h o w i n g t h e m a j o r r i v e r systems. I n s e t map i n d i c a t e s t h e p o s i t i o n o f t h e i s l a n d o f f the n o r t h e a s t c o a s t o f Venezuela.  1,6 F i e l d Observations In addition to c o l l e c t i n g  stocks i n June,  1976,  L i l e y and I  o b s e r v e d t h e .guppies i n t h e i r n a t u r a l s t r e a m s , n o t i n g d i s t r i b u t i o n and m e a s u r i n g in the  stream v e l o c i t y .  Stream  their  velocity  t h e f a s t e s t s e c t i o n o f e a c h s t r e a m was f o u n d t o be w i t h i n  (1973»  range g i v e n f o r the stream by Seghers  and Table I ) ,  e x c e p t f o r t h e l o w l a n d r i v e r s w h e r e i t was lower', s i n c e we d i d n o t measure i t f o l l o w i n g a heavy The  two h e a d s t r e a m s ,  mostly of r i f f l e s ,  1  r a i n as d i d Seghers.  the P a r i a and Upper A r i p o ,  although there are occasional  s e c t i o n s and a few p o o l s .  consist  smooth-flowing  The d e n s i t y o f g u p p i e s  appeared  s l i g h t l y h i g h e r i n t h e s m o o t h - f l o w i n g and p o o l s e c t i o n s b u t g u p p i e s were d i s p e r s e d a c r o s s t h e e n t i r e some r i f f l e s  (where  the v e l o c i t y  stream bed, i n c l u d i n g  r a n g e d f r o m 0.17  t o 0.50  G u p p i e s were o b s e r v e d t o r e m a i n n e a r t h e s u b s t r a t e • all  m/sec).  i n these  streams and t o p e r f o r m c o u r t s h i p b e h a v i o u r i n river sections, In  including  riffles.  t h e two l o w l a n d r i v e r s ' , t h e Guayamare a n d C a p a r o , t h e  s i t u a t i o n was e n t i r e l y d i f f e r e n t . long smooth-flowing sections.  These r i v e r s  Here guppies o c c u r r e d i n s c h o o l s  n e a r t h e w a t e r s u r f a c e a t t h e r i v e r edges. a velocity velocity  of  0.1^-0.16  consist of  The r i v e r s f l o w e d a t  m/sec a t t h e c e n t r e ; h o w e v e r , t h e  a t t h e i r e d g e s was u s u a l l y l e s s .  Throughout the  l o w l a n d r e g i o n , , g u p p i e s were a l s o f o u n d i n d r a i n a g e t r e n c h e s and p o o l s n e a r t h e r i v e r s , where t h e r e i s a l m o s t no s t r e a m  flow.  U n l i k e the other streams, lowland r i v e r s f l u c t u a t e w i d e l y i n depth d u r i n g t h e wet and d r y seasons and o f t e n o v e r f l o w t h e i r  1'?banks during lowland live and  the  r a i n y season, d i s p e r s i n g f i s h .  populations,  and  the  stream v e l o c i t y i n which the  very  m/sec).  m o u n t a i n s p r i n g , P e t i t e Curucaye", c o n s i s t s o f n u m e r o u s  shallow  r i f f l e s w h i c h are  f r e q u e n t l y b r o k e n by  f l o w i n g s e c t i o n s and  pools.  s l o w ( l e s s t h a n O.30  m/sec) and  o v e r the  e n t i r e stream  Maintaining  and.50 f e m a l e s .  Here, stream v e l o c i t y i s  aquaria  s t a r t e d w i t h a t l e a s t 50  conditions.  rooms.  and  6l  The  f i s h were hous.ed  litre  E a c h s t o c k was  .'which were s p a t i a l l y  capacity,  h o u s e d i n up  i s o l a t e d from other  w e r e removed- f r o m t h e w i l d - c a u g h t f i s h and separate tanks.  d e n s i t i e s and  reduce  A l l t a n k s had f i l t e r e d with  same s t o c k  in  eight  stocks.  Young  to mature  fresh dechlorinated  to  in  equalize  b e d s o f medium o r f i n e g r a v e l and  e x t e r n a l charcoal* f i l t e r s .  tank  The  :  was  were  t a n k s were  Lemna.  One-third  changed t w i c e m o n t h l y  with  water.  t a n k s we r e / " . l i t by cm  located to  allowed  w i t h V a l l i s n e r i a . C e r a t o p t e r i s . and  s u s p e n d e d 15  and  inbreeding.  o f the w a t e r i n each-  The  males  T h e s e i s o l a t e d f i s h were o c c a s i o n a l l y  t r a n s f e r r e d between tanks of the  planted  dispersed  A l l s t o c k s were m a i n t a i n e d u n d e r s i m i l a r  i n g l a s s t a n k s o f ^3  tanks  g u p p i e s were f o u n d  fairly  bed.  s t o c k was  controlled laboratory  three  smooth-  Stocks  Each laboratory  reared  guppies  ( o f t e n n e a r 0 m/sec  p e r f o r m c o u r t s h i p 'is r e l a t i v e l y l o w  u s u a l l y l e s s t h a n 0.16 The  T h u s , f o r " >•  30  o r ^0-watt f l u o r e s c e n t  above t h e w a t e r on a 13L-11D  tubes  photoperiod.  •  18 T e m p e r a t u r e i n t h e a q u a r i a rooms was m a i n t a i n e d a t 23-26°C, e l i m i n a t i n g the need f o r i n d i v i d u a l tank h e a t e r s . The  f i s h were f e d t w i c e d a i l y o n a d i e t o f c o m m e r c i a l l y  p r e p a r e d d r i e d f o o d , o c c a s i o n a l l y supplemented brine The  with frozen  s h r i m p a n d c h o p p e d T u b i f e x worms.  Stream All  Tanks  t e s t s were p e r f o r m e d  s t r e a m t a n k s ( F i g . 2)  i n two s p e c i a l l y c o n s t r u c t e d  designed by L i l e y  and m y s e l f .  T h e s e were  c o n s t r u c t e d i n t h e U.B.C. D e p a r t m e n t o f Zoology, w o r k s h o p * f r o m c l e a r p l e x i g l a s and mounted on plywood b a s e s .  Various  stream  c u r r e n t s w e r e c r e a t e d b y u s i n g a s u b m e r s i b l e pump ( M o d e l 4SMD, Little  G i a n t Pump Company) t h a t f o r c e d w a t e r t h r o u g h two 2 . 5  plastic  tubes.  These p l a s t i c  t u b e s were c o n n e c t e d  t o two  p l e x i g l a s t u b e s , one l o c a t e d a t e a c h e n d o f t h e c i r c u l a r tank channel. spaced 4.5  cm  stream  The p l e x i g l a s t u b e s e a c h h a d s i x 6 mm-holes  cm a p a r t .  Water f o r c e d through these h o l e s created  a f a i r l y l - e v e n c u r r e n t across the width o f the stream  tank  channel. The  s t r e a m v e l o c i t y was c o n t r o l l e d b y a l t e r i n g a v a r i a b l e  a u t o t r a n s f o r m e r ( o u t p u t v o l t a g e range 3PN,  Superior Electric  pump.  0-140 V; P o w e r s t a t , Type  Company) c o n n e c t e d  The s t r e a m v e l o c i t y p r o d u c e d  to the submersible  was m e a s u r e d u s i n g a  f l o a t i n g v i a l a n d t i m i n g i t s movement o v e r a 1 m e t e r D u r i n g a l l t e s t s f i s h were r e s t r i c t e d area o f the stream tank channel. The  to theobservation  T h i s a r e a was 100 X 25 X 15 cm.  f i s h were r e s t r a i n e d b y s c r e e n s (2.5  each end o f t h e a r e a .  distance.  A reference grid  mm-mesh) l o c a t e d a t o f 10 r e c t a n g l e s ~ ( 7 • 5 X  2 0 0  25  CM  CM  (D © ® © © ©  F i g u r e 2.  Schematic  diagram of stream tank.  Submersible pump P l a s t i c tube Plexiglas tubes with 6 mm h o l e s V a r i a b l e autotransformer Screen Observation area with grid  20  cm)  was  m a r k e d on t h e f r o n t o f t h i s o b s e r v a t i o n a r e a .  s h e e t o f b l a c k p l e x i g l a s was t i o n area d u r i n g Experiment which  p l a c e d a t the back o f the I , p r o v i d i n g a background  t h e f i s h were e a s i l y o b s e r v e d .  w h i t e p l e x i g l a s s h e e t was slightly The  observaagainst  During Experiment  II a  used, making the o b s e r v a t i o n a r e a  brighter. stream  t a n k s were l o c a t e d i n a s e p a r a t e l a b o r a t o r y  room, k e p t u n d e r t h e same p h o t o p e r i o d and a q u a r i a rooms.  The  stream  t a n k h e l d 500  Each stream  o f w h i c h was  been housed.  The  charcoal f i l t e r Recording of  temperature  as  the  t a n k s were l i t b y e i g h t ^1-0-watt  f l u o r e s c e n t t u b e s l o c a t e d 1.9  liters  A  m e t e r s above t h e  water.  l i t e r s of water,  drawn f r o m t a n k s i n w h i c h  t a n k s were f i l t e r e d w i t h a  at least  the s t o c k s  10 had  submersible  and a e r a t e d w i t h an a i r s t o n e .  Observations  O b s e r v a t i o n s were made w h i l e s i t t i n g a p p r o x i m a t e l y 1 from the f r o n t of the stream  tanks.  B e h a v i o u r p a t t e r n s were  r e c o r d e d on a ^--channel R u s t r a k p a p e r c h a r t e v e n t at  a c h a r t speed  sequences, was  o f 6 cm/min.  r e c o r d e d by hand u s i n g check grid.  recorder  From t h e s e r e c o r d i n g s f r e q u e n c i e s ,  o r d u r a t i o n s were c a l c u l a t e d .  the r e f e r e n c e  meter  Fish  distribution  sheets c o n t a i n i n g models of  CHAPTER I V EXPERIMENT I : THE POPULATIONS AT  SOCIAL BEHAVIOUR OF P.  RETICULATA  DIFFERENT WATER V E L O C I T I E S  Introduction I n t h i s experiment of guppies, river,  e a c h one  I examine the b e h a v i o u r  bred  from e i t h e r a headstream,  or s p r i n g population.  The  experiment  p r e d i c t i o n s t h a t f i s h from the l o w l a n d 1) g r e a t e r c o h e s i o n , preference  f o r the  headstream f i s h . males perform gonopodial was  lowland the  stock should  s u r f a c e r e g i o n of stream  tanks  show and  3)  swings than headstream males.  The  lowland  spring stock  i n an i n t e r m e d i a t e  stream  p r e d i c t e d t o show a l e v e l o f c o u r t s h i p headstream s t o c k s .  main purpose of t h i s experiment  e f f e c t of stream  velocity  was  t o examine  on e a c h s t o c k ' s c o u r t s h i p  I p r e d i c t e d 1) t h a t c o u r t s h i p b e h a v i o u r  f o r a l l s t o c k s as s t r e a m v e l o c i t y (.increases  the  behaviour.  t h r e e s t o c k s were t h e r e f o r e t e s t e d i n each o f f o u r  decrease  greater  than  I t a l s o t e s t s the p r e d i c t i o n t h a t  i n t e r m e d i a t e b e t w e e n t h e l o w l a n d and  velocities.  stocks  f e w e r s i g m o i d d i s p l a y s b u t more t h r u s t s and  v e l o c i t y and was  The  tests  2) l e s s a g g r e s s i v e " b e h a v i o u r ,  bred from a p o p u l a t i o n l i v i n g  The  of three  stream  should and  2) t h a t f i s h f r o m t h e h e a d s t r e a m s t o c k , d e s c e n d a n t f r o m  fish  that lived  to  i n f a s t - f l o w i n g water,  continue performing from the l o w l a n d  s h o u l d be b e t t e r a b l e  c o u r t s h i p i n f a s t - f l o w i n g water than  stock.  fish  To d e t e r m i n e w h e t h e r d i f f e r e n c e s "between p o p u l a t i o n s a r e largely genetic, at least f i f t h w i l d - c a u g h t f i s h were u s e d .  generation descendants of  Y o u n g were r e m o v e d f r o m t h e  o r i g i n a l w i l d - c a u g h t f i s h w i t h i n a few days o f b i r t h a l l o w e d t o mature under s i m i l a r  in isolation.  and  A l l s t o c k s had- b e e n . m a i n t a i n e d  ( s t i l l water) c o n d i t i o n s , e l i m i n a t i n g  environmental e f f e c t of stream v e l o c i t y , f o r s e v e r a l  any generations.  M a t e r i a l s and M e t h o d s A d u l t guppies from Caparo and P e t i t e C u r u c a y e containing f i f t h  (spring)  (lowland), P a r i a (headstream),  s t o c k s were t e s t e d .  Each  i n the G e n e r a l  III).  F r o m e a c h s t o c k , f o u r g r o u p s o f 10 were t e s t e d  stocks,  to eighth generation descendants of wild-caught  f i s h , were c u l t u r e d and m a i n t a i n e d a s o u t l i n e d Methods ( C h a p t e r  These  ( a t o t a l o f 20  m a l e s and 20  fish,  5 o f each sex,  females per  stock).  s t o c k ' s f o u r g r o u p s were t e s t e d d u r i n g d i f f e r e n t w e e k s ,  w i t h e a c h g r o u p t e s t e d i n a d i f f e r e n t s t r e a m v e l o c i t y on e a c h o f f o u r c o n s e c u t i v e days. g r o u p was  The  stream v e l o c i t i e s  i n which  each  t e s t e d v a r i e d a c c o r d i n g t o the f o l l o w i n g s c h e d u l e :  1  Dav  Dav  2  Day  Stream V e l o c i t y  3  Dav  (m/sec)  Group  1 2 3  •°  7  .10 • 03 .20  .03 .07 .20 .10  .10 .20 .07 .03  .20 .03 .10 .07  4  The  stream v e l o c i t i e s used l i e w e l l w i t h i n the range  velocities  f o r streams  i n h a b i t e d by g u p p i e s .  Faster  were n o t u s e d s i n c e the s t r e a m t a n k s d i d n o t c o n t a i n o f d e c r e a s e d v e l o c i t y , where g u p p i e s c o u l d r e s t  of velocities areas  (eg. behind  rocks)• The  5 m a l e s and 5 f e m a l e s f o r e a c h g r o u p were d r a w n f r o m  t h e s t o c k t a n k s f o u r d a y s b e f o r e t e s t i n g and p l a c e d , e a c h separately,  i n two  12-liter holding tanks.  On t h e m o r n i n g  e a c h c o n s e c u t i v e t e s t day t h e s e f i s h were i n t r o d u c e d i n t o stream tank.  (The  s t r e a m v e l o c i t y >in t h e t a n k was  introducingnthe fish.)  sex of the  set before  A t t h e end o f e a c h o b s e r v a t i o n day  f i s h w e r e r e t u r n e d t o t h e two h o l d i n g t a n k s .  the  T h i s procedure  of i s o l a t i n g the sexes ensured the s t a r t o f c o u r t s h i p b e h a v i o u r soon a f t e r t h e i r i n t r o d u c t i o n , e l i m i n a t i n g the need f o r a l o n g acclimation Each  period.  of the group's  day f o r t e n m i n u t e s ;  f i v e m a l e s was  a p p r o x i m a t e l y 1,  i n t r o d u c t i o n of the f i s h .  In total,  t h r e e 10-min r e c o r d i n g s f o r 20  observed three times a  3»  and 4 h o u r s  t h i s procedure  after produced  males from each o f the t h r e e  s t o c k s i n each of f o u r stream v e l o c i t i e s . d u r a t i o n o f s i g m o i d d i s p l a y s was  The  number and  r e c o r d e d , a s w e l l as t h e  number o f g o n o p o d i a l s w i n g s , t h r u s t s , c o p u l a t i o n a t t e m p t s , a g g r e s s i v e a t t a c k s , b o t h i n i t i a t e d and r e c e i v e d . e a s i l y d i s t i n g u i s h e d f r o m one  Males  a n o t h e r by t h e i r d i s t i n c t  and  were colour  p a t t e r n s , e s p e c i a l l y t h e i r b l a c k markings. D u r i n g each t e s t the d i s t r i b u t i o n of the t e n f i s h m a l e s and f e m a l e s ) was f i s h was  a l s o r e c o r d e d . • The  r e c o r d e d u s i n g t h e g r i d o f 10  p o s i t i o n of  (both each  r e c t a n g l e s marked-, on,••the  f r o n t o f the stream tank.  Recordings  i n t e r v a l s f o r a 10 m i n u t e p e r i o d (20 o f r e c o r d i n g s was r e p e a t e d beginning  approximately  of the f i s h .  1,  cohesion  4,  d u r i n g each t e s t day,  and 5 hours a f t e r i n t r o d u c t i o n  veloctiy.  d i s t r i b u t i o n r e c o r d i n g s were u s e d t o d e t e r m i n e and depth.  S e g h e r s , 1973)  An " i n d e x  was c a l c u l a t e d .  o f cohesion"  grid  sec observation, s q u a r e s was r e c o r d e d .  i n d e x i s t h e mean maximum d e n s i t y f o r t h e 80  int-each t e s t .  observations  I t h a s a t h e o r e t i c a l minimum o f l " ( o n e f i s h i n  e a c h o f t h e 10: s q u a r e s ) a n d a maximum o f 10 the  group  (designed by  F o r e a c h 30  t h e maximum d e n s i t y f o r a n y o f t h e 10 The  This series  T h u s 80 r e c o r d i n g s o f d i s t r i b u t i o n were made f o r  each group i n each stream The  recordings).  four times 3,  were made a t 30 s e c  ( e n t i r e group i n  a r e a o f one s q u a r e ) . O c c a s i o n a l l y d u r i n g t h i s e x p e r i m e n t a m a l e d i e d o r became  "sick".  I f s o , i t was r e p l a c e d w i t h a n o t h e r  e l i m i n a t e d from the data a n a l y s i s .  f i s h and  F o l l o w i n g the experiment  e a c h g r o u p o f f i s h was a n a e s t h e t i z e d  i n MS-222 ( t r i c a i n e  methyl  s u l p h o n a t e ) , measured w i t h c a l i p e r s , photographed and then housed i n separate  post-experiment  breeding  tanks.  S t a t i s t i c a l Treatment o f Data When c o m p a r i n g t h e same s t o c k u n d e r d i f f e r e n t  stream  c o n d i t i o n s I u s e d t h e F r i e d m a n two-way a n a l y s i s o f v a r i a n c e (Siegel,  1956)-  When c o m p a r i n g d i f f e r e n t s t o c k s u n d e r t h e  same s t r e a m c o n d i t i o n s t h e M a n n - W h i t n e y U t e s t was u s e d * (Siegel,  1956).  C o r r e l a t i o n s between the s i z e  o f males and  c o u r t s h i p b e h a v i o u r p a t t e r n s (see Appendix)  were m e a s u r e d  u s i n g the Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t R e s u l t s and  1956)•  (Siegel,  Discussion  Stream Depth L o c a t i o n The for  i s g i v e n i n r e l a t i o n to stream  e a c h s t o c k i n F i g u r e 3«  (0.03 of  depth of f i s h  At the s l o w e s t f l o w i n g  m/sec) t h e P a r i a ( h e a d s t r e a m ) t h e t a n k l e s s t h a n 20%  the  location,  made o f t h e " g r o u p  each s t o c k a t d i f f e r e n t v e l o c i t i e s d i f f e r e n c e was  Caparo  of the time.  t h e e f f e c t o f s t r e a m v e l o c i t y on  a c o m p a r i s o n was  depth  depths" f o r  (Table I I ) .  No  significant  found between v e l o c i t i e s f o r the P a r i a  P e t i t e Curucaye  and  s t o c k s ( a l t h o u g h f i s h were l o c a t e d l e s s  c o n t r a s t , the l o w l a n d Caparo  variance due  i n i t s group  to a decrease  depths.  often 3).  i n the top o f the tank w i t h i n c r e a s i n g v e l o c i t y , F i g . In  half  ( s p r i n g ) f i s h were l o c a t e d i n  t o p h a l f o f t h e t a n k more t h a n 50% Toodetermine  condition  f i s h were i n the t o p  o f the t i m e , whereas the  ( l o w l a n d ) and P e t i t e G u r u c a y e  velocity  s t o c k showed a  significant  T h i s v a r i a n c e was  clearly  i n the time spent i n the top h a l f o f the  s t r e a m t a n k a'ststream v e l o c i t y  I n c r e a s e d ( F i g . 3) .  The  number o f t i m e s f i s h were l o c a t e d i n t h e t o p h a l f o f t h e s t r e a m t a n k d e c r e a s e d b e t w e e n t h e s l o w e s t and f a s t e s t by 28$  f o r t h e P a r i a s t o c k , by 35$  s t o c k , and by 76$ of the  t h e two  f o r the Caparo  velocitie  f o r the P e t i t e C urucaye stock (Table I I ) .  Thus,  s t o c k s t h a t showed a p r e f e r e n c e f o r t h e t o p o f  stream tank i n s l o w - f l o w i n g w a t e r , the P e t i t e  Curucaye  F i g u r e 3«  "Group_,_depth" i n r e l a t i o n t o s t r e a m v e l o c i t y . Means ± 95% c o n f i d e n c e i n t e r v a l s . C = C a p a r o , P = P a r i a , PC = P e t i t e C u r u c a y e (N = 1 6 ) . (Lowland) (Headstream) (Spring)  vON  Table I I .  Stock  Comparison o f "group depth" f o r each stock a t d i f f e r e n t stream v e l o c i t i e s .  Mean number o f t i m e s p e r 200 t h a t f i s h were i n the top h a l f o f the stream tank  Overall Difference (Friedman 2-way ANOVA)  Stream v e l o c i t y (m/sec)  .03  •07  .10  .20  Caparo  109-9  93-9  65.3  26.9  <.01  Petite Curucaye  137.4  113.4  89.I  N. S.  19.8  23.0  N.S.  Paria  32.0  131.4 28.6  28 fish  ( d e r i v e d f r o m an i n t e r m e d i a t e  were b e t t e r a b l e t o m a i n t a i n stream tank  stream v e l o c i t y  t h e i r l o c a t i o n a t the  top of  i n f a s t - f l o w i n g w a t e r , whereas the Caparo  were u n a b l e t o do  I I I ) , i n the  slowest v e l o c i t y  three  fish  t h e r e was  a  stocks significant  d i f f e r e n c e b e t w e e n C a p a r o and P a r i a s t o c k s b u t no  significant  d i f f e r e n c e b e t w e e n C a p a r o and P e t i t e C u r u c a y e s t o c k s . highest velocity  t h i s s i t u a t i o n was  P a r i a stocks not  significantly  In  the  r e v e r s e d , w i t h Caparo  and  d i f f e r e n t and C a p a r o and  C u r u c a y e s t o c k s now  s i g n i f i c a n t l y d i f f e r e n t from each  T h i s i s c l e a r l y due  to the  depthV  the w i l d  l o c a t i o n t h e i r parent  (see Chapter I I I ) .  The  p o p u l a t i o n was p e r s i s t e n c e of  differences i n laboratory raised fish  suggests  in this trait.  The  i n f a s t e r - f l o w i n g water, whereas Caparo f i s h represent  an a d a p t a t i o n by  that there  at a l l v e l o c i t i e s .  The  these  P a r i a s t o c k , whose  stream so,  to parent  as p r e d i c t e d , stream  t h a t P a r i a f i s h have been  s e l e c t e d to p r e f e r a p o s i t i o n n e a r the surface  fish  a r e u n a b l e t o do  f o r the bottom o f the  I speculate  m a i n t a i n i n g a p o s i t i o n a t the  is  that  top of the  i n the f a s t e s t stream v e l o c i t y ,  exhibited a consistent preference tank  in  these  the P e t i t e Curucaye f i s h  i n f a s t e r - f l o w i n g water.  population lived  stream  f a c t t h a t P e t i t e Curucaye  are b e t t e r a b l e t o m a i n t a i n p o s i t i o n a t the  living  "group  observed  a g e n e t i c b a s i s t o s t r e a m d e p t h l o c a t i o n and  stocks vary  may  other.  ( F i g . 3).  t o the  likely  Petite  change i n t h e C a p a r o s t o c k ' s  E a c h s t o c k e x h i b i t e d a s i m i l a r l o c a t i o n i n the tank  the  so.  Comparing stream l o c a t i o n between the (Table  population)  s t r e a m bed is difficult  because i n f a s t -water.  Table I I I .  Comparison o f "group depth" between stocks a t different stream,velocities.  c, , .. Stream v e l o c i t y / / > (m/sec)  "Group d e p t h " Comparison between s t o c k s * ••> * C > P C ^ PC P ^ PC ' ' P •  .03  <.001  N.S.  < .002  .07  <.001  N.S.  <.002  .10  <.oi  <.02  <.002  <.002  <.002  .20  N.S.  *Mann-Whitney U t e s t . . C = C a p a r o , P = P a r i a ' , PC = P e t i t e C u r u c a y e .  30 Index of  Cohesion  C o m p a r i n g e a c h s t o c k s e p a r a t e l y ( F i g . k),  none o f  the  s t o c k s showed s i g n i f i c a n t v a r i a n c e s i n c o h e s i o n u n d e r (p<c.05, Friedman  four v e l o c i t i e s  the  test).  Comparing c o h e s i o n between s t o c k s (Table I V ) , I found Caparo had  a s i g n i f i c a n t l y higher index than P e t i t e  a t a l l stream v e l o c i t i e s .  The  not  The  These r e s u l t s s u p p o r t  i n any  The  of  s t o c k was  the stream  velocities.  t h a t these t e n d e n c i e s are  p r e d i c t i o n t h a t the l o w l a n d  s t o c k would have a g r e a t e r tendency (Paria)  and  the h y p o t h e s i s t h a t s t o c k s v a r y i n  t o s c h o o l and  genetic control.  o f P a r i a i n the s l o w e s t  P a r i a and P e t i t e C u r u c a y e i n d i c e s were  significantly different  t h e i r tendency  Curucaye  C a p a r o s t o c k i n d i c e s were a l s o  s i g n i f i c a n t l y h i g h e r than those fastest velocities.  that  confirmed.  The  under  (Caparo)  t o s c h o o l than the  headstream  P e t i t e Curucaye stock  was  s i m i l a r to the headstream s t o c k i n i t s s c h o o l i n g b e h a v i o u r . I n T r i n i d a d , l o w l a n d f i s h were f o u n d and  i n schools w h i l e headstream  s p r i n g p o p u l a t i o n s were d i s p e r s e d o v e r t h e s t r e a m  Chapter  III).  Again, each s t o c k e x h i b i t e d behaviour  to the w i l d p o p u l a t i o n from which The  results  i t was  bed  (see  similar  descended.  indicate that differences existing  between  s t o c k s i n t h e i r i n d e x of c o h e s i o n , o r degree of s c h o o l i n g , are n o t a f f e c t e d by velocities  stream v e l o c i t y ,  tested.  a t l e a s t w i t h i n the range  P e r h a p s d i f f e r e n c e s i n c o h e s i o n a r e due  d i f f e r e n t p r e d a t i o n pressures (as suggested or to other factors, combination  of  such as stream  factors.  by S e g h e r s ,  turbidity,  or to  a  of to  1973)  F i g u r e 4.  Index of Cohesion i n r e l a t i o n to stream v e l o c i t y . Means i 95% c o n f i d e n c e i n t e r v a l s . C = Caparo (Lowland), P = P a r i a (Headstream), PC = P e t i t e C u r u c a y e ( S p r i n g ) , ( N = 16).  Table IV.  Stream velocity (m/sec)  .03 .07  C o m p a r i s o n o f " I n d e x o f C o h e s i o n " betwe stocks a t d i f f e r e n t stream v e l o c i t i e s .  Index o f Cohesion Comparison between s t o c k s * O P  C > PC  P <J PC !  <.0l  <.03  N.S.  N..S.  <.0l  N.S.  <.01  N.S.  <.01  N.S.  (~.06) .10 .20  N.S. (^.08) <.01  * M a n n - W h i t n e y U t e s t ( P r e d i c t i o n s b a s e d on S e g h e r s , 1973)C = C a p a r o , P = P a r i a , PC = P e t i t e C u r u c a y e .  Male  Aggression F o r each s t o c k male a g g r e s s i o n i s g i v e n i n F i g u r e .5.  velocity d i d not of the  The  i n r e l a t i o n to  stream  number o f m a l e  attacks  d i f f e r s i g n i f i c a n t l y between stream v e l o c i t i e s f o r s t o c k s (p <.05,  Friedman t e s t ) ,  although  any  i t did  d e c r e a s e somewhat f o r t h e P a r i a s t o c k . Although  a g g r e s s i o n v a r i e d w i d e l y among i n d i v i d u a l P a r i a  m a l e s ( F i g . 5)1 C a p a r o and (Table  P e t i t e Curucaye m a l e s a t most s t r e a m  than  velocities  V).  Ballin another  t h e y were s i g n i f i c a n t l y more a g g r e s s i v e  (1973) f o u n d P a r i a m a l e s t o be more a g g r e s s i v e  l o w l a n d p o p u l a t i o n o f males (Guayamare).  o f t h i s e x p e r i m e n t c o n f i r m my  w h i c h had  than lowland males (Caparo)  spring population (Petite  n o t p r e v i o u s l y been s t u d i e d )  aggressive.  Once a g a i n , t h e s e  results  p r e d i c t i o n t h a t P a r i a (headstream)  m a l e s s h o u l d be more a g g r e s s i v e a l s o i n d i c a t e t h a t the  The  than  and  Curucaye,  is relatively  non-  b e h a v i o u r 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 l i k e l y have a g e n e t i c b a s i s . Stream v e l o c i t y does n o t among m a l e s d i r e c t l y ,  although  appear to a f f e e t . a g g r e s s i o n t h e r e may  i n aggression with increasing v e l o c i t y .  be  a slight  decrease  20 J  15MEAN NUMBER  OF  ATTACKS 10-  PER MALE PER  30  MIN  5  .03  .07  '  '  STREAM VELOCITY F i g u r e 5«  .10 (M/SEC)  Male a g g r e s s i o n i n r e l a t i o n t o stream v e l o c i t y . Means i 95% c o n f i d e n c e I n t e r v a l s . . C = C a p a r o ( L o w l a n d ; N = 19), P = P a r i a ( H e a d s t r e a m ; N = PC = P e t i t e C u r u c a y e ( S p r i n g ; N = 17).  19),  35  T a b l e V.  Comparison o f Male A g g r e s s i o n a t d i f f e r e n t stream v e l o c i t i e s .  Stream velocity  Male A t t a c k s Comparison between s t o c k s *  (m/sec)  C < P  .03  <.00l  .07  <.o25  .10  <.05  N.S.  .20  <.01  N.S.  *Mann-Whitney U t e s t , 1 - t a i l e d for  C =5* PC.,.  P=5* PC.  C =^PC  N.S.  P ^ PC  <.002  N.S.  f o r C < P,  C = Caparo', P = P a r i a , PC = P e t i t e  ^.02 N.S.  '2-tailed  Curucaye.  36 Courtship Behaviour  Patterns  Thrusts  Displays  and S i g m o i d  The  r e l a t i o n s h i p b e t w e e n t h e mean number o f t h r u s t s 7 ,  p e r f o r m e d by m a l e s and s t r e a m v e l o c i t y  i s shown i n F i g u r e  C o m p a r i n g e a c h s t o c k s e p a r a t e l y , t h e r e was no variance  6.  significant  i n t h e number o f t h r u s t s p e r f o r m e d a t t h e f o u r  velocities  (Table V I ) .  As p r e d i c t e d , C a p a r o m a l e s c o n s i s t e n t l y e x h i b i t e d more t h r u s t s a t a l l v e l o c i t i e s than P e t i t e Curucaye males.  Petite  C u r u c a y e m a l e s i n t u r n c o n s i s t e n t l y p e r f o r m e d more t h r u s t s P a r i a males.  than  T h e s e d i f f e r e n c e s were s i g n i f i c a n t b e t w e e n C a p a r o  and P a r i a m a l e s a t t h e two f a s t e s t v e l o c i t i e s ( T a b l e V I I ) . F o r e a c h s t o c k t h e r e was a s i g n i f i c a n t v a r i a n c e number o f s i g m o i d velocities. of sigmoid increased  i n the  d i s p l a y s performed a t the d i f f e r e n t  stream  T h i s v a r i a n c e was due t o a d e c r e a s e i n t h e number d i s p l a y s performed by males as stream  velocity  ( F i g . 7) .  A l s o a s p r e d i c t e d , P a r i a m a l e s p e r f o r m e d more  sigmoid  d i s p l a y s a t a l l stream v e l o c i t i e s than P e t i t e Curucaye males, and  P e t i t e C u r u c a y e m a l e s i n t u r n a l w a y s d i s p l a y e d more  f r e q u e n t l y than Caparo males.  The d i f f e r e n c e s b e t w e e n P a r i a  and P e t i t e C u r u c a y e a n d b e t w e e n P a r i a a n d C a p a r o w e r e s i g n i f i c a n t a t t h e two s l o w e s t v e l o c i t i e s Each population's r a t i o at the f o u r stream v e l o c i t i e s  of sigmoid  displays : thrusts  i s g i v e n i n F i g u r e 8.  s t o c k s showed a s i g n i f i c a n t v a r i a n c e the f o u r v s t r e a m v e l o c i t i e s .  (Table V I I ) .  A l l three  i n t h e i r r a t i o s between  The v a r i a n c e was due t o a  .03  .0? STREAM VELOCITY  Figure 6 .  .10  .20  (M/SEG)  Number o f t h r u s t s i n r e l a t i o n t o s t r e a m v e l o c i t y . Means ± 9 5 % c o n f i d e n c e i n t e r v a l s . C = C a p a r o ( L o w l a n d ; N = 19), P = P a r i a ( H e a d s t r e a m ; N = PC = P e t i t e C u r u c a y e ( S p r i n g ; N = 17).  19)  \j0  38  Table VI.  C o m p a r i s o n o f number o f T h r u s t s , S i g m o i d D i s p l a y s , and the r a t i o o f S i g m o i d D i s p l a y s : T h r u s t s f o r each stock a t d i f f e r e n t stream velocities.  Stream v e l o c i t y (m/sec)  Stock • 03  •0?  .10  .20  Overall Difference (Friedman 2-way ANOVA) P  Mean number o f T h r u s t s p e r male p e r 30 m i n s Caparo  25-9  34.0  28.2  24.5  N.S.  Petite Curucaye  23-5  30.1  24.1  22.5  N.S.  Paria  23.5  25.9  19.4  18.1  N. S.  Mean number o f S i g m o i d • Displays p e r male p e r 30 m i n s Caparo  33-9  29.3  22.4  11.1  <.001  Petite Curucaye  34.5  36.6  33.5  20.6  <.01  Paria  49-4  48.1  34.1  24.2  <.001  Ratio  of Sigmoid D i s p l a y s : Thrusts  Caparo  1.31  0.86  0.79  0.46  Petite Curucaye  1.4-7  1.22  1-39  0.92  Paria  2.10  1.85  1.76  1.34  ^.01 •  <".0l  <.oi  Table V I I .  Stream velocity  C o m p a r i s o n o f number o f T h r u s t s , S i g m o i d D i s p l a y s a n d t h e r a t i o of Sigmoid D i s p l a y s : T h r u s t s between s t o c k s a t d i f f e r e n t v e l o c i t i e s .  Number o f T h r u s t s Comparison between s t o c k s *  Number o f S i g m o i d D i s p l a y s Comparison between s t o c k s *  Ratio of Displays:Thrusts Comparison between s t o c k s *  C > P  C>PC  P <: PC  C < P  P>PC  C <: P  .03  N.S.  N.S.  N.S.  <.05  <.01  N.S.  <-025  .07  N.S.  N.S.  N.S.  <.01  N.S.  =.025  N.S.  N.S.  N.S.  N.S.  (m/sec)  C<PC  <.05  N.S.  0 l  N.S.  <  t  N.S.  C < PC  P > PC  C^.05) .10  <.025  N.S.  .20  <.05  N.S.  <.05 N.S.  N.S.  N.S.  N.S.  N.S.  N.S.  N.S.  (^.05)  *Mann-Whitney U t e s t . C = Caparo, P = P a r i a ,  PC = P e t i t e C u r u c a y e ,  N.S. <.025  50  50  ko  MEAN NUMBER OF SIGMOID DISPLAYS  .30  30  PER MALE PER  30  P  MIN  PC  20  lio  10  03  .07 STREAM VELOCITY  F i g u r e 7-  20  .10  .20  (M/SEC)  Number o f s i g m o i d d i s p l a y s i n r e l a t i o n t o s t r e a m v e l o c i t y . Means ± 95% c o n f i d e n c e i n t e r v a l s . Cr=.-Oaparo ( L o w l a n d ; N = 19) , P = P a r i a ( H e a d s t r e a m ; N = 19) PC = P e t i t e C u r u c a y e ( S p r i n g ; N = 17).  ,  o  2.00.  RATIO  1.50,  OF  •2.00  PC  SIGMOID  PC  DISPLAYS : THRUSTS  '1.50  PC  1.00  •1.00  0.50  •0.50  03  .07 STREAM VELOCITY  F i g u r e 8.  .10  .20  (M/SEC)  Ratio of sigmoid d i s p l a y s : t h r u s t s i n r e l a t i o n t o stream v e l o c i t y . C = C a p a r o ( L o w l a n d ; N = 19), P = P a r i a (Headstream; N = 19), PC = P e t i t e C u r u c a y e ( S p r i n g ; N = 17).  k2 decrease  i n the r a t i o  as stream v e l o c i t y  increased  T h i s means t h a t , a s p r e d i c t e d , t h e f r e q u e n c y decreased  more t h a n  velocity  increased.  the frequency  of sigmoid  ratio  displays  o f t h r u s t s as stream  At a l l v e l o c i t i e s P a r i a had the h i g h e s t r a t i o displays  8 ) .  (Fig.  of sigmoid  : t h r u s t s and P e t i t e Curucaye i n t u r n had a h i g h e r  than Caparo.  T h e s e d i f f e r e n c e s i n c o u r t s h i p were  s i g n i f i c a n t "between t h e P a r i a a n d C a p a r o s t o c k s a t t h r e e  of the  velocities  a n d b e t w e e n P a r i a a n d P e t i t e C u r u c a y e a t two o f t h e  velocities  (Table V I I ) .  Differences  i n the frequencies  o f t h r u s t s and  sigmoid  d i s p l a y s between t h e Caparo and P a r i a s t o c k s a r e c o n s i s t e n t with r e s u l t s f o r s i m i l a r stocks tested i n s t i l l 1973f  Snyder, 1 9 7 8 ) •  water  As p r e d i c t e d , t h e h e a d s t r e a m  u s e d more d i s p l a y s w h i l e l o w l a n d P e t i t e Curucaye stock, bred  fish  (Ballin,  population  u s e d more t h r u s t s .  from an i n t e r m e d i a t e  v e l o c i t y p o p u l a t i o n , used an i n t e r m e d i a t e  The  stream  courtship strategy.  These d i f f e r e n c e s between s t o c k s a g a i n presumably  reflect  genetic differences. The ability  p r e d i c t i o n t h a t each p o p u l a t i o n d i f f e r s to perform  supported. fish  c o u r t s h i p i n i n c r e a s i n g stream v e l o c i t y  Specifically,  were b e t t e r a b l e  than lowland  fish.  ini t s  i n f a s t e r - f l o w i n g water headstream  to maintain  t h e i r frequency  of displays  I n s l o w - f l o w i n g water the Caparo  stock  d i s p l a y e d more t h a n  i t t h r u s t e d , h o w e v e r , i t was u n a b l e t o  maintain  i n faster velocities.  this ratio  fastest velocity as  was  In fact,  i n the  i t d i s p l a y e d l e s s than h a l f as f r e q u e n t l y  i t t h r u s t e d ( F i g . 8 , Table  VI).  The P a r i a s t o c k  performed  more t h a n t w i c e  a s many s i g m o i d d i s p l a y s a s t h r u s t i n s l o w -  f l o w i n g w a t e r , a n d a t t h e f a s t e r v e l o c i t i e s i t was a l w a y s to m a i n t a i n a higher The  ratio  frequency of d i s p l a y s than t h r u s t s .  of sigmoid displays  : t h r u s t s decreased between the  s l o w e s t a n d f a s t e s t v e l o c i t i e s b y 65% by  36%  only  able  f o r the P a r i a stock.  f o r t h e Caparo s t o c k and  Thus P a r i a ( h e a d s t r e a m )  fish  appear b e t t e r adapted t o d i s p l a y i n g i n f a s t e r - f l o w i n g water than Caparo (lowland) f i s h . an  intermediate  ratio  (The P e t i t e C u r u c a y e s t o c k h a d  a n d were a b l e  to maintain this ratio to  a b o u t t h e same d e g r e e a s t h e P a r i a s t o c k fry 37%  - the r a t i o  between t h e f a s t e s t and s l o w e s t stream v e l o c i t i e s . ) The  ratio  slow-flowing  of sigmoid displays  water  (l.3l)  : t h r u s t s f o r Caparo i n  was s i m i l a r t o t h e r a t i o  fastest velocity  the  second f a s t e s t v e l o c i t y  (1.39)•  Although t h i s could  c o i n c i d e n t a l i t i s i n t e r e s t i n g t h a t i n the w i l d populations  perform courtship  t h u s may be a c h i e v i n g p e r f o r m an o p t i m a l successful  of sigmoid displays  r a t i o of sigmoid displays  then the p r e v i o u s l y  populations  Perhaps males : thrusts f o r  i n their ratio  : thrusts  Since sigmoid displays  between  of sigmoid displays  : thrusts velocities.  d e c r e a s e more t h a n t h r u s t s w i t h  stream v e l o c i t y , males t h a t l i v e  increasing  i n f a s t - f l o w i n g w a t e r may  have e v o l v e d a tendency t o p e r f o r m a h i g h e r : thrusts  does  observed d i f f e r e n c e s  represent adaptations t o d i f f e r e n t stream  displays  these  a t t h e s e r e l a t i v e v e l o c i t i e s and  roughly s i m i l a r r a t i o s .  ratio  be  mating.  I f an o p t i m a l exist,  f o rParia at  (1.3^) a n d t o P e t i t e C u r u c a y e * s r a t i o a t  the  could  decreased  ratio  of sigmoid  (as observed i n slow water) i n order t o s t i l l  be p e r f o r m i n g a t t h e o p t i m a l r a t i o when i n f a s t - f l o w i n g As n o t e d , when h e a d s t r e a m  water.  f i s h were o b s e r v e d i n f a s t - f l o w i n g  w a t e r t h e i r r a t i o was c l o s e t o t h a t o f l o w l a n d f i s h observed i n s l o w - f l o w i n g water.  Thus, apparent  when  differences'  i n male c o u r t s h i p o b s e r v e d between p o p u l a t i o n s i n s t i l l may n o t a c t u a l l y e x i s t i n t h e w i l d .  This point i s important  when c o n s i d e r i n g t h e a d a p t i v e s i g n i f i c a n c e guppy c o u r t s h i p b e h a v i o u r .  water  of variation i n  P r e v i o u s l y observed  courtship  d i f f e r e n c e s may r e p r e s e n t a d a p t i v e r e s p o n s e s t o i n c r e a s i n g s t r e a m v e l o c i t y r a t h e r t h a n a d a p t a t i o n s l o n l y t o t u r b i d i t y and p r e d a t i o n as suggested by B a l l i n  (1973)'  The mean number a n d d u r a t i o n o f s i g m o i d d i s p l a y s , number o f s i g m o i d d i s p l a y s l o n g e r t h a n 1.5 of  sees, and percentage  s i g m o i d d i s p l a y s l o n g e r t h a n 1.5- s e e s a r e g i v e n i n T a b l e  V I I I f o r each the  mean  stock a t the four stream v e l o c i t i e s .  d u r a t i o n o f d i s p l a y s and p e r c e n t a g e  t h a n 1-5  I n general  of displays longer  sees d e c r e a s e d as stream v e l o c i t y  increased.  At a l l stream v e l o c i t i e s P e t i t e Curucaye  m a l e s have, t h e  l o n g e s t s i g m o i d d i s p l a y s and t h e g r e a t e s t p e r c e n t a g e l o n g e r t h a n 1.5 slightly  sees.  A t s l o w e r v e l o c i t i e s Caparo  of displays  m a l e s have  l o n g e r d i s p l a y s a n d more d i s p l a y s l o n g e r t h a n 1.5  than P a r i a males.  sees  However, as p r e d i c t e d , a t t h e f a s t e r t s t r e a m  v e l o c i t i e s the opposite i s the case, w i t h P a r i a males having slightly  l o n g e r d i s p l a y s than Caparo  d i s p l a y s l o n g e r t h a n 1.5  m a l e s a n d more s i g m o i d  sees.  As e x p e c t e d , i n c r e a s i n g s t r e a m v e l o c i t y d o e s d e c r e a s e the  duration of sigmoid displays f o r f i s h  stocks.  from a l l t h r e e  H o w e v e r , t h e r e was n o t a l w a y s a d i r e c t  relationship  Table V I I I .  Stream velocity  Mean number and d u r a t i o n o f S i g m o i d D i s p l a y s a t f o u r stream v e l o c i t i e s .  Mean number o f Sigmoid D i s p l a y s / m a l e /30 m i n s C  Mean d u r a t i o n o f Sigmoid Displays (sees)  PC  P  C  PC  P  Mean number o f Sigmoid Displays >1.5 sees C  PC  P  Percentage of Sigmoid D i s p l a y s >4.5 sees C PC P  .03  33.9  34.5  49.4  1.4  1185  1.2  13.1  18.8  18.2  38.4  54.5  36.7  .07  29.3  36.6  48.1  1.3  1.5  1.1  10.5  16.8  14.9  35.7  45.8  31.0  .10  22.4  33-5  34.1  1.0  1.3  1.0  4.2  14.0  8.7  18.8  41.8  25.6  . 20  11.1  20.6  24.2  0.9  1.5  1.0  1.8  8.9  5-9  16.5  43.4  24.6  46  between a s t o c k ' s a b i l i t y and  t o perform longer sigmoid displays  i t s n a t u r a l stream v e l o c i t y .  living  i n f a s t e r - f l o w i n g water  F i s h d e r i v e d from p o p u l a t i o n s  ( P a r i a and P e t i t e Curucaye) d i d ,  as p r e d i c t e d , p e r f o r m l o n g e r d i s p l a y s i n t h e f a s t e r than t h e l o w l a n d (Caparo) intermediate  fish.  stream v e l o c i t y  velocities  However, t h e males from t h e  (Petite Curucaye),  performed  d i s p l a y s o f t h e l o n g e s t mean d u r a t i o n a t a l l s t r e a m  velocities,  w h i c h was n o t p r e d i c t e d . Gonopodial  Swings  The mean number o f g o n o p o d i a l s w i n g s p e r f o r m e d b y e a c h stock i n r e l a t i o n t o stream v e l o c i t y All  i s shown i n F i g u r e 9»  s t o c k s e x h i b i t e d a s i g n i f i c a n t v a r i a n c e i n t h e number o f  gonopodial swings performed  at different velocities  (Table I X ) .  T h i s v a r i a n c e was due t o a d e c r e a s e i n g o n o p o d i a l s w i n g s a s stream v e l o c i t y of  i n c r e a s e d ( F i g . 9).  g o n o p o d i a l swings  i s a f f e c t e d by stream  Under a l l stream v e l o c i t y P e t i t e Curucaye  C l e a r l y the performance  c o n d i t i o n s b o t h t h e Caparo and  stocks performed  s i g n i f i c a n t l y more g o n o p o d i a l  swings than the P a r i a s t o c k (Table X ) . Curucaye  velocity.  The C a p a r o  and P e t i t e  s t o c k s were n o t s i g n i f i c a n t l y d i f f e r e n t a t a n y o f 'the  velocities. The  d i f f e r e n c e between t h e Caparo  and P a r i a s t o c k s  c o n f i r m s my p r e d i c t i o n t h a t l o w l a n d m a l e s s h o u l d p e r f o r m more gonopodial swings than headstream based  T h i s p r e d i c t i o n was  on t h e d i f f e r e n c e s f o u n d between s i m i l a r  and l o w l a n d p o p u l a t i o n s by B a l l i n The  males.  headstream  (1973)- and S n y d e r  p r e v i o u s l y u n s t u d i e d P e t i t e Curucaye  v  (1978).  s t o c k ' s performance  of  03  .07 STREAM VELOCITY  F i g u r e 9.  .10  .20  (M/SEC)  Number o f g o n o p o d i a l s w i n g s i n r e l a t i o n t o s t r e a m v e l o c i t y . Means ± 95% c o n f i d e n c e i n t e r v a l s . ' C = C a p a r o ( L o w l a n d ; N = 19), P = P a r i a (Headstream; N = 19), PC = P e t i t e C u r u c a y e ( S p r i n g ; N = 17).  48  Table IX.  StcSitock  C o m p a r i s o n o f number o f G o n o p o d i a l S w i n g s p e r f o r m e d art d i f f e r e n t s t r e a m v e l o c i t i e s f o r each s t o c k .  Mean number o f G o n o p o d i a l S w i n g s Stream v e l o c i t y (m/sec)  Overall Difference (Friedman 2-way ANOVA)  03  .07  .10  .20  Caparo  32.8  26.5  25-5  18.3  <.001  Petite Curucaye  31.9  32.6  32.1  21.0  <.01  Paria  18.7  18.8  13.8  11.5  <.001  49  T a b l e X.  C o m p a r i s o n o f number o f G o n o p o d i a l S w i n g s between s t o c k s a t d i f f e r e n t stream v e l o c i t i e s .  Stream velocity (m/sec)  Number o f G o n o p o d i a l S w i n g s Comparison between s t o c k s * C > P  O  PC  P<PC  P .03  <.00i  N.S.  <.001  .07  <C«025  N.S.  <-.00l  .10  <.001  N.S.  <.001  .20  <.001  N.S.  <-025  *Mann-Whitney U t e s t . C = C a p a r o , P = P a r i a , PC = P e t i t e C u r u c a y e .  the  h i g h e s t frequency of g o n o p o d i a l swings a t a l l stream  v e l o c i t i e s was  not predicted.  f i n d i n g , ' however, i s d i f f i c u l t g o n o p o d i a l swings  The  significance  of  this  to i n t e r p r e t , e s p e c i a l l y  i n f a c t o c c u r d u r i n g "both c o u r t s h i p  n o n - c o u r t s h i p and t h e i r f u n c t i o n r e m a i n s unknown.  since  and  ( I n the  Appendix, which d e a l s w i t h the e f f e c t of stream v e l o c i t y  on  c o r r e l a t i o n s between c o u r t s h i p b e h a v i o u r p a t t e r n s , I c o n s i d e r i n m o r e - d e t a i l the f u n c t i o n of g o n o p o d i a l swings.)  At present  the  signifi'.caneei'ofnthe d i f f e r e n c e s found between s t o c k s i n  the  performance  Copulation  o f g o n o p o d i a l s w i n g s r e m a i n s unknown.  Attempts  The mean number o f c o p u l a t i o n a t t e m p t s p e r f o r m e d by m a l e s of  e a c h s t o c k a t t h e f o u r s t r e a m v e l o c i t i e s and t h e  of  s i g m o i d d i s p l a y s t h a t w e r e f o l l o w e d by c o p u l a t i o n  are  listed  d u r i n g the  i n Table XI.  No  a c t u a l c o p u l a t i o n s were  ( l e s s t h a n one statistically.  p e r m a l e p e r 30  observed  The  infrequently  m i n s ) , I d i d n o t a n a l y z e them  number o f c o p u l a t i o n a t t e m p t s  w i t h i n c r e a s i n g stream v e l o c i t y ,  d i s p l a y s , t h i s d e c r e a s e may  decreased  except f o r the P a r i a s t o c k .  S i n c e c o p u l a t i o n a t t e m p t s are always p r e c e d e d by  sigmoid  r e f l e c t t h e d e c r e a s i n g number o f  s i g m o i d d i s p l a y s p e r f o r m e d by m a l e s as s t r e a m  Liley  attempts  experiment.  B e c a u s e 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 so  increased  percentages  velocity  ( F i g . 7) .  (1966)  noted t h a t c o p u l a t i o n attempts are  on f e m a l e s m a i n t a i n i n g t h e i r p o s i t i o n d u r i n g and f o l l o w i n g a sigmoid display.  dependent  immediately  C o p u l a t i o n attempts are  51  Table XI.  Stream velocity (m/sec)  Mean number o f C o p u l a t i o n A t t e m p t s a n d percentage o f Sigmoid D i s p l a y s f o l l o w e d by C o p u l a t i o n A t t e m p t s .  Mean number o f C o p u l a t i o n Attempts /male / 3 0 mins  Percentage of Sigmoid D i s p l a y s : f o l l o w e d "by Copulation Attempts r  C  PC  P  c  PC  P  .03  1.1  0.7  0.3  3.3  2.0  0.6  .07:;'  0.8  0.5  0.7  2.7  1.3  1.4  .10  0.4  0.5  0.3  1.6  1.5  -0.8  .20  0.2  0.1  0.5  1.9  0.6  2.2  C = C a p a r o , PC = P e t i t e C u r u c a y e ,  P = Paria.  u n s u c c e s s f u l because  f e m a l e s a r e s e l d o m r e c e p t i v e , and when  unreceptive they r a r e l y m a i n t a i n t h e i r p o s i t i o n near d i s p l a y i n g male.  Thus a l a c k o f female r e c e p t i v i t y  reduces  t h e number o f c o p u l a t i o n a t t e m p t s p e r f o r m e d b y m a l e s f e m a l e s move away f r o m d i s p l a y i n g m a l e s .  a  because  H o w e v e r , when m a l e s  p e r f o r m more c o p u l a t i o n a t t e m p t s t h i s d o e s n o t mean t h a t w e r e n e c e s s a r i l y more r e c e p t i v e .  T h i s i s because  many  copulation attempts arSlperformed to unreceptive females have ( i n a d v e r t e n t l y ? )  temporarily maintained t h e i r  d u r i n g a male's d i s p l a y .  Thus c o p u l a t i o n a t t e m p t s  (When f e m a l e s a r e r e c e p t i v e ,  who  position reflect  f e m a l e p o s i t i o n i m m e d i a t e l y f o l l o w i n g a d i s p l a y and receptivity.  females  not  they continue  1  maintaining t h e i r p o s t i t i o n f o l l o w i n g sigmoid displays, resulting i n successful copulations. female r e c e p t i v i t y . )  Z-~ .. The  Thus c o p u l a t i o n s  f l u c t u a t i o n i n the  percentage  o f s i g m o i d d i s p l a y s t h a t were f o l l o w e d by c o p u l a t i o n at d i f f e r e n t stream v e l o c i t i e s  (Table XI) l i k e l y  reflect  attempts  simply  r e f l e c t s v a r i a t i o n s i n female p o s i t i o n d u r i n g sigmoid d i s p l a y s . Summary o f R e s u l t s Guppies bred from p o p u l a t i o n s l i v i n g (Caparo)  and f a s t - f l o w i n g ( P a r i a )  i n slow-flowing  streams d i f f e r e d  i n the  f o l l o w i n g ways: 1)  Caparo  g u p p i e s were l o c a t e d i n t h e t o p h a l f o f t h e  s t r e a m t a n k s i g n i f i c a n t l y more o f t e n t h a n P a r i a  guppies  ( e x c e p t a t t h e f a s t e s t s t r e a m v e l o c i t y , when t h e y were unable  to maintain t h e i r  2) C a p a r o  position).  g u p p i e s were s i g n i f i c a n t l y more c o h e s i v e t h a n  53  P a r i a g u p p i e s a t b o t h t h e s l o w e s t and f a s t e s t 3)  C a p a r o m a l e s were s i g n i f i c a n t l y l e s s a g g r e s s i v e t h a n  P a r i a males at a l l stream 4)  velocities.  velocities.  Caparo males performed  s i g n i f i c a n t l y fewer  sigmoid  d i s p l a y s and more t h r u s t s and g o n o p o d i a l s w i n g s t h a n  Paria  males i n s l o w - f l o w i n g water.. 5)  F o r b o t h guppy p o p u l a t i o n s t h e f r e q u e n c y o f s i g m o i d  d i s p l a y s , t h r u s t s , and g o n o p o d i a l s w i n g s d e c r e a s e d a s velocity  increased.  The  frequency of sigmoid  stream  displays  d i s p l a y s d e c r e a s e d more t h a n t h e f r e q u e n c y o f t h r u s t s a s  stream  velocity increased. 6)  C a p a r o m a l e s were l e s s a b l e t o m a i n t a i n t h e i r  c o u r t s h i p b e h a v i o u r and than P a r i a males. i n the r a t i o  stream p o s i t i o n at h i g h v e l o c i t i e s  C a p a r o m a l e s showed a g r e a t e r d e c r e a s e  of sigmoid d i s p l a y s  : t h r u s t s than P a r i a males  as s t r e a m v e l o c i t y i n c r e a s e d . 7)  I n f a s t e r - f l o w i n g water the s i g m o i d d i s p l a y s  performed  b y C a p a r o m a l e s were o f s h o r t e r d u r a t i o n t h a n t h o s e o f P a r i a males. Thus, a l l seven o r i g i n a l p r e d i c t i o n s r e g a r d i n g these p o p u l a t i o n s were i n l a r g e p a r t c o n f i r m e d .  In addition,  as p r e d i c t e d ,  most  o f the c o u r t s h i p b e h a v i o u r p a t t e r n s o f the i n t e r m e d i a t e stream v e l o c i t y p o p u l a t i o n ( P e t i t e Curucaye) between the headstream  were i n t e r m e d i a t e  and l o w l a n d p o p u l a t i o n s .  THe. p e r s i s t e n c e o f . t h e s e d i f f e r e n c e s i n b e h a v i o u r . i n l a b o r a t o r y r a i s e d descendants  demonstrates  g e n e t i c c o n t r i b u t i o n t o the d i f f e r e n c e s . t h e r e f o r e presumably  that there i s a TKe  differences  r e p r e s e n t the p r o d u c t of n a t u r a l  selection.  S t r e a m v e l o c i t y was depth l o c a t i o n .  f o u n d t o have a d i r e c t e f f e c t  H o w e v e r , no d i r e c t e f f e c t  on c o h e s i o n and m a l e a g g r e s s i o n was c o u r t s h i p b e h a v i o u r was  found.  of stream  on guppy  velocity  The..performance o f  c l e a r l y a f f e c t e d by s t r e a m  velocity,  w i t h b o t h s i g m o i d d i s p l a y s and g o n o p o d i a l s w i n g s b e i n g m a r k e d l y d e c r e a s e d by  increasing  S u p p o r t was  velocity.  g a i n e d f o r the h y p o t h e s i s t h a t p o p u l a t i o n  differences, especially  i n male c o u r t s h i p b e h a v i o u r , r e p r e s e n t  adaptive responses to stream  velocity.  55  CHAPTER V EXPERIMENT I I : MALE P.  RETICULATA COURTSHIP BEHAVIOUR  MATE PREFERENCE I N S T I L L AND  AND  FLOWING WATER CONDITIONS  Introduction I n t h i s e x p e r i m e n t I s t u d y the w i l d - c a u g h t g u p p i e s f r o m two populations.  The  p a i r s o f h e a d s t r e a m and  four populations  and  i n one  the  f i s h were m a i n t a i n e d i n the  week.  courtship behaviour  lowland  were t e s t e d i n s t i l l  flowing water c o n d i t i o n .  However, I a g a i n  of  water  Unlike Experiment I ,  stream c o n d i t i o n f o r a  t e s t e d the  full  p r e d i c t i o n s t h a t 1)  lowland  m a l e s p e r f o r m f e w e r s i g m o i d d i s p l a y s b u t more t h r u s t s  and  g o n o p o d i a l s w i n g s t h a n h e a d s t r e a m m a l e s , 2)  behaviour  should 3)  fish  decrease f o r a l l stocks from the  to maintain  i n the  flowing water,  headstream populations  courtship  should  m i g h t be  e x p e c t e d , due  selection occurring  p a i r s of populations  in still  were s t u d i e d  wildprior  l a c k of  water tanks.  since p a r a l l e l  of the To  any  Two  differences  b e t w e e n them, r e f l e c t i n g d i f f e r e n c e s f o u n d b e t w e e n s t o c k s Experiment I , would provide  able  fish.  to t h e i r the  and  better  d i f f e r e n c e s between these  e x p e r i e n c e i n d i f f e r e n t s t r e a m v e l o c i t i e s and laboratory  be  i n f l o w i n g water than lowland  S t r i k i n g behavioural caught p o p u l a t i o n s  courtship  in  a d d i t i o n a l support f o r g e n e r a l i t y  results. e x a m i n e c o u r t s h i p b e h a v i o u r i n more d e t a i l I  t h e number o f " c o u r t s h i p b o u t s " p e r f o r m e d by of males.  (A c o u r t s h i p b o u t was  defined  each  determined  population  as a s e r i e s  of  consecutive to the  sigmoid  d i s p l a y s a n d / o r t h r u s t s p e r f o r m e d by  same f e m a l e . )  d i s p l a y s and  Since, i n Experiment I , both  sigmoid  t h r u s t s were f o u n d t o d e c r e a s e w i t h i n c r e a s i n g  stream v e l o c i t y , I p r e d i c t t h a t headstream males perform  a male  more c o u r t s h i p b o u t s ( o b s e r v e d  should  i n s l o w - f l o w i n g water)  i n order to m a i n t a i n t h e i r l e v e l of c o u r t s h i p i n f a s t - f l o w i n g water.  The  number o f b e h a v i o u r  c o u r t s h i p • b o u t s was  patterns performed  a l s o examined.  wfiether a l l p o p u l a t i o n s perform, of behaviour courting  T h i s was  done t o  on a v e r a g e , t h e  determine  same number  p a t t e r n s t o i n d i v i d u a l f e m a l e s once t h e y  begin  them.  A n o t h e r o b j e c t i v e o f t h i s e x p e r i m e n t was m a l e mate p r e f e r e n c e  females from another  determine populations.  to t e s t the p r e d i c t i o n t h a t males  s h o u l d c o u r t f e m a l e s f r o m t h e i r own  on B a l l i n ' s  to  f o r females from d i f f e r e n t  I e x a m i n e d mate p r e f e r e n c e  by  during  population.  p o p u l a t i o n more  than  T h i s p r e d i c t i o n was  (1973)Mstudy,which found a degree o f  based  selectivity  d i f f e r e n t p o p u l a t i o n s of males f o r females of t h e i r  population. During  B a l l i n ' s r e s u l t s , h o w e v e r , were i n c o n c l u s i v e . t h i s e x p e r i m e n t m a l e and  f e m a l e mate  d i r e c t l y by  observing courtship behaviour  r e c o r d i n g which females males courted. male m a t i n g s u c c e s s indirectly.  autoradiographic  Female c h o i c e  were d e t e r m i n e d a t t h e  T h i s was  preferences  T d e t e r m i n e d male mate  were a c t u a l l y t e s t e d s i m u l t a n e o u s l y . preference  own  done by L i l e y  technique,  same t i m e  and L u y t e n ,  using  and but an  m e a s u r i n g ' : ; l a b e l l e d and u n l a b e l l e d  sperm c o l l e c t e d f r o m the f e m a l e s '  o v i d u c t s a t t h e end  experiment.  technique  The  and  autoradiographic  was  used  of to  the  determine whether reproductive whether  one  s t o c k o f m a l e s had g r e a t e r p o t e n t i a l  s u c c e s s ( i e . i n s e m i n a t e d more f e m a l e s )  this reproductive  velocity  condition.  s u c c e s s was  Unfortunately,  a f f e c t e d by  and  stream  the r e s u l t s from  t e c h n i q u e have n o t y e t been a n a l y z e d .  this  ( D e t a i l s of the  t e c h n i q u e u s e d and t h e r e s u l t s w i l l be r e p o r t e d e l s e w h e r e Liley  and  by  Luyten.)  M a t e r i a l s and M e t h o d s The  p r o c e d u r e u s e d i n t h i s e x p e r i m e n t was  conjunction with L i l e y  designed i n  and L u y t e n .  Wild-caught a d u l t guppies from f o u r T r i n i d a d were t e s t e d - Guayamare ( l o w l a n d ) , U p p e r A r i p o Caparo  ( l o w l a n d ) , and P a r i a ( h e a d s t r e a m ) .  t r a n s p o r t to Vancouver under  populations  (headstream),  Following  their  t h e s e p o p u l a t i o n s were m a i n t a i n e d  s i m i l a r c o n d i t i o n s (see G e n e r a l Methods, Chapter I I I ) . Guayamare and U p p e r A r i p o  groups  c o n t a i n i n g 20 f i s h ,  5 of each sex from both  I n e a c h g r o u p , m a l e s f r o m one radioactive o f m a l e s was  f i s h were t e s t e d t o g e t h e r  label incorporated  tested i n both s t i l l  but w i t h a d i f f e r e n t group  populations.  o f t h e two p o p u l a t i o n s h a d i n t h e i r sperm.  Each  and f l o w i n g w a t e r  conditions  o f females i n each c o n d i t i o n .  ;  1  5  UA* 5GG  5 5  UA G*  Females i n S t i l l water (A)  5 UA 5G 5 UA 5G  a  group  g r o u p s were as f o l l o w s : Groups of Males  in  Females i n 0.08 m/sec (B)  5 UA 5G 5 UA 5G  The  58  Females i n S t i l l Water  Groups o f Males  3  5 5  UA* G  5 UA 5 G  5 UA 5 G  5 5  UA G*  5 UA 5GG  5 UA 5 G  *Males i n j e c t e d w i t h r a d i o a c t i v e l a b e l . UA = U p p e r A r i p o , G = Guayamarer, M a l e s f r o m G r o u p s 1 a n d 2 were t e s t e d f i r s t  in still  water  ( w i t h G r o u p 1A a n d 2A f e m a l e s ) a n d t h e n i n a s t r e a m v e l o c i t y o f 0.08 m/sec ( w i t h G r o u p I B a n d 2B f e m a l e s ) . f r o m G r o u p s 3 a n d 4 were t e s t e d f i r s t in  s t i l l water.  sampled  In contrast,  i n f l o w i n g w a t e r and t h e n  F o l l o w i n g e a c h t e s t t h e f e m a l e s were k i l l e d a n d The same 20 m a l e s  f o r sperm.  tested i n both s t i l l  f r o m e a c h p o p u l a t i o n were  and f l o w i n g w a t e r , whereas,  40  f r o m e a c h p o p u l a t i o n were t e s t e d b u t h a l f i n s t i l l and h a l f i n f l o w i n g w a t e r The represent to  0.08 m/sec v e l o c i t y was c h o s e n , a s s u m i n g a fairly  females water  only  only. i t to  f a s t v e l o c i t y c o n s i d e r i n g t h a t f i s h were  be m a i n t a i n e d i n i t f o r a f u l l week.  velocity  males  i n E x p e r i m e n t I (0.07  (The s e c o n d  slowest  m/sec) h a d o n l y a s l i g h t  effect  on c o u r t s h i p b e h a v i o u r , h o w e v e r , f i s h w e r e m a i n t a i n e d i n i t for  l e s s than a during the experiment.) M a l e s f o r e a c h g r o u p were d r a w n f r o m p o p u l a t i o n  25 d a y s b e f o r e  t e s t i n g and p l a c e d  domestic stimulus females. thymidine-(methyl-  C) 25,  tanks  i n i s o l a t e d holding tanks with  T h e s e m a l e s were i n j e c t e d w i t h 20,  a n d 10 d a y s b e f o r e  C o n t r o l m a l e s were i n j e c t e d w i t h s a l i n e . were removed f r o m t h e h o l d i n g t a n k s f i v e  testing.  The s t i m u l u s days b e f o r e  females  testing,  59  e n s u r i n g the s t a r t o f c o u r t s h i p b e h a v i o u r by the males after introduction first  test  t o the stream tanks.  soon  A t t h e end o f t h e  t h e m a l e s were r e t u r n e d t o i s o l a t e d h o l d i n g  tanks.  L a t e r t h e y were i n t r o d u c e d t o a s e c o n d s t r e a m t a n k u n d e r t h e alternate After  stream condition,  w i t h t h e second group o f females.  t h i s s e c o n d t e s t t h e m a l e s were Females  killed.  f o r each group were drawn f r o m t h e p o p u l a t i o n t a n k s  a p p r o x i m a t e l y 25 days b e f o r e t e s t i n g and p l a c e d d i r e c t l y i n t h e stream tanks.  F i v e t o c e i g h t days b e f o r e t e s t i n g ,  the females  w e r e m a r k e d w i t h a s m a l l . d o t on t h e t o p o r b o t t o m o f t h e i r tails  to distinguish  them b y p o p u l a t i o n .  The d o t was made b y  intramuscular i n j e c t i o n w i t h i n d e l i b l e Trypan blue i n k .  The  f e m a l e s were t h e n r e t u r n e d t o t h e s t r e a m t a n k w h i c h was s e t a t t h e v e l o c i t y t o be u s e d d u r i n g t h e t e s t .  The t e s t  began  when t h e f e m a l e s r e c o v e r e d f r o m t h e m a r k i n g p r o c e d u r e ( 5 t o 8 days).  A t t h e e n d o f e a c h t e s t f e m a l e s were k i l l e d a n d  o v i d u c t s a m p l e s f o r s p e r m were t a k e n . Each t e s t l a s t e d of  20 f i s h  one week, d u r i n g w h i c h t i m e t h e g r o u p  ( e g . G r o u p I A ) was h o u s e d  i n the stream tank.  0 . 0 8 m/sec o r w i t h no  v e l o c i t y was k e p t c o n s t a n t , a t e i t h e r current, f o r the entire group o f males  seven days.  Theysecond  t e s t f o r each  ( e g . Group I B , a t t h e second v e l o c i t y )  5 t o 8 days a f t e r t h e end o f t h e f i r s t On d a y s 1 ,  The  occurred  test.  3 i 5» a n d 7 o f e a c h t e s t , two 1 0 - m i n r e c o r d i n g s  w e r e made f o r e a c h o f - t h e g r o u p ' s 10 m a l e s .  On e a c h o f t h e s e  d a y s one r e c o r d i n g was made i n t h e m o r n i n g a n d one i n t h e afternoon.  T h u s a t o t a l o f e i g h t 1 0 - m i n r e c o r d i n g s was made  f o r each male.  M a l e s were d i s t i n g u i s h e d  f r o m one a n o t h e r b y  t h e i r i n d i v i d u a l colour p a t t e r n s . . Each recording t h e number o f s i g m o i d  d i s p l a y s , gonopodial  s w i t c h e s , leaps,- and ...copulation a t t e m p t s male. occur  contained  swings,  side-  performed, by t h e  ( S i d e - s w i t c h e s have n o t p r e v i o u s l y been d e s c r i b e d . during sigmoid  switches  They  d i s p l a y s when t h e m a l e , w h i l e d i s p l a y i n g ,  t h e s i d e o f h i s body w h i c h f a c e s t h e f e m a l e .  This  i s brought about by a r a p i d t u r n i n the h o r i z o n t a l p l a n e , head t o t a i l ,  f o l l o w i n g which the sigmoid  F o r each behaviour to  display  p a t t e r n p e r f o r m e d b y a male t h e p o p u l a t i o n  w h i c h t h e f e m a l e he c o u r t e d b e l o n g e d was a l s o  Mate p r e f e r e n c e  recorded.  o f m a l e s a n d t h e number a n d l e n g t h o f c o u r t s h i p  b o u t s c o u l d t h e r e f o r e be This experimental  determined.  p r o c e d u r e was r e p e a t e d  u s i n g Caparo and  P a r i a f i s h , h o w e v e r , t h e m a l e s were n o t i n j e c t e d radioactive  continues.)  label.  Thus, i n t o t a l ,  the procedure  with produced  e i g h t 10-min r e c o r d i n g s f o r 20 m a l e s f r o m e a c h o f t h e f o u r populations  i n e a c h o f two s t r e a m v e l o c i t y c o n d i t i o n s .  O c c a s i o n a l l y during the experiment a f i s h "sick".  I f s o , i t was r e p l a c e d w i t h a n o t h e r  from the data a n a l y s i s .  d i e d o r became  fish  F o l l o w i n g the experiment  and e l i m i n a t e d each,group  o f m a l e s was a n a e s t h e t i z e d , m e a s u r e d w i t h c a l i p e r s , g r a p h e d a n d h a d a sperm smear Statistical  photo-  taken.  Treatment o f the Data  When c o m p a r i n g t h e same s t o c k u n d e r t h e two s t r e a m c o n d i t i o n s a n d when d e t e r m i n i n g females,  I used the Wilcoxon  (Siegel,  1956).  m a l e mate p r e f e r e n c e f o r  matched-pairs signed-ranks  test  When c o m p a r i n g d i f f e r e n t s t o c k s u n d e r t h e  same s t r e a m . c o n d i t i o n s , 1956).  (Siegel,  t h e M a n n - W h i t n e y U - t e s t was u s e d  C o r r e l a t i o n s between the s i z e  various courtship behaviour  patterns  o f males and  ( s e e A p p e n d i x ) were  m e a s u r e d u s i n g t h e Spearman r a n k c o r r e l a t i o n  coefficient  1956).  (Siegel,  R e s u l t s and D i s c u s s i o n Thrusts  and Sigmoid  The  Displays  mean n u m b e r s o f t h r u s t s p e r f o r m e d b y m a l e s i n t h e two  stream c o n d i t i o n s are g i v e n i n F i g u r e  10.  A l l four  stocks  p e r f o r m e d more t h r u s t s i n t h e 0.08 m/sec v e l o c i t y c o m p a r e d t o s t i l l water. (p < . 0 5 ,  The i n c r e a s e s , h o w e v e r , were n o t  Wilcoxon  significant  test).  Comparing each p a i r o f lowland  and headstream  stocks  ( C a p a r o w i t h P a r i a ; Guayamare w i t h U p p e r A r i p o ) , l o w l a n d  fish  u s u a l l y p e r f o r m e d more t h r u s t s t h a n h e a d s t r e a m f i s h a n d i n still  w a t e r the  d i f f e r e n c e b e t w e e n Guayamare and U p p e r A r i p o  m a l e s was s i g n i f i c a n t The  ( F i g . 10) .  mean n u m b e r s o f s i g m o i d  d i s p l a y s performed by each  s t o c k i n t h e two s t r e a m c o n d i t i o n s a r e g i v e n i n F i g u r e The  stocks performed e i t h e r approximately  decreased  number o f s i g m o i d  the  11.  same o r a  d i s p l a y s i n f l o w i n g water.  d e c r e a s e was s i g n i f i c a n t o n l y f o r t h e P a r i a s t o c k  The  (p<c.05,  Wilcoxon test) . As p r e d i c t e d , u n d e r b o t h  stream c o n d i t i o n s lowland  performed s i g n i f i c a n t l y fewer sigmoid males ( F i g . 11).  d i s p l a y s than  males  headstream  20 4 N.S.  MEAN  15J  N.S.  NUMBER THRUSTS.  N.S.  p <.025  OF 1 0 1  PER MALE PER 40 MINS 5J  G UA  G  . 00  ~ToE  Stream v e l o c i t y  Figure  10.  UA  (m/sec)  Number o f t h r u s t s i n r e l a t i o n t o s t r e a m v e l o c i t y . Means i t 9 5 % c o n f i d e n c e i n t e r v a l s . Probability values a r e f r o m t h e Mann-Whitney U - t e s t , 1 - t a i l e d f o r C > P, G > UA. C = C a p a r o (N(.OO) = 19; N ( . 0 8 ) = 17)., P = P a r i a (N(.OO) = 20; N ( . 0 8 ) = 1 9 ) , G = Guayamare (N(.OO) = 17; N ( . 0 8 ) = 1 7 ) , UA = U p p e r A r i p o (N(.OO) = 19; N ( . 0 8 ) = 1 7 ) .  120 A  120 p  <.001 p<.001  MEAN  90  J  p  <.001  P  <.oi  I  90  NUMBER OF SIGMOID DISPLAYS  60 4  6o  ?3<H  r 30  ? PER MALE PER 40 MINS  UA  UA  .00  .08 Stream v e l o c i t y  Figure 11.  (m/sec)  Number o f s i g m o i d d i s p l a y s i n r e l a t i o n t o s t r e a m v e l o c i t y . Means ± 9 5 % c o n f i d e n c e i n t e r v a l s . P r o b a b i l i t y v a l u e s are from t h e M a n n - W h i t n e y U - t e s t , 1 - t a i l e d f o r P ;> C, UA > G. C = C a p a r o , P = P a r i a , G = Guayamare, UA = U p p e r A r i p o .  ON  All thrusts  f o u r stocks had a lower r a t i o i n flowing water than i n s t i l l  difference Aripo  i n r a t i o was s i g n i f i c a n t  stocks  o f sigmoid displays : water ( F i g .  f o r t h e P a r i a and Upper  (p<>05, W i l c o x o n t e s t ) .  Comparisons between each p a i r o f s t o c k s predicted, ratios in  the headstream stocks  of sigmoid displays  both stream c o n d i t i o n s  also consistent with  ( F i g . 12).  stocks  These d i f f e r e n c e s a r e  those found i n Experiment I .  d i s p l a y s and t h e r a t i o  stocks  higher  : thrusts than the lowland  i n the frequencies  consistent with  showed t h a t , a s  had s i g n i f i c a n t l y  I n summary, d i f f e r e n c e s b e t w e e n t h e s e populations  12)..This  o f b o t h t h r u s t s and s i g m o i d  of sigmoid displays  differences  i n Experiment I .  wild-caught  : thrusts are  found between Caparo and P a r i a  I n both experiments lowland  fish  p e r f o r m e d f e w e r s i g m o i d d i s p l a y s a n d more t h r u s t s t h a n t h e headstream f i s h . stream v e l o c i t y the  However, t h e marked e f f e c t s o f i n c r e a s i n g f o u n d i n E x p e r i m e n t I were n o t f o u n d b e t w e e n  two s t r e a m c o n d i t i o n s  here.  T h e r e was no s u p p o r t f o r t h e p r e d i c t i o n t h a t f i s h are b e t t e r able  to maintain displays i n faster-flowing  water than lowland f i s h . displays  30%  Comparing the r a t i o  : t h r u s t s f o r each stock  0.08 m/sec, t h e r a t i o by  headstream  i nstill  o f sigmoid  water and a t  d e c r e a s e d b e t w e e n t h e two'  conditions  30% f o r C a p a r o , 29% f o r P a r i a , 3% f o r G u a y a m a r e , a n d f o r Upper A r i p o  ratios  Thus t h e l o w l a n d  populations'  d e c r e a s e d b y t h e same amount o r l e s s t h a n t h e h e a d s t r e a m  ratios. still  ( F i g . 12).  I t s h o u l d be n o t e d , h o w e v e r , t h a t h e a d s t r e a m m a l e s  used d i s p l a y s  s i g n i f i c a n t l y more f r e q u e n t l y  than lowland  16,  •16  P <.ooi  14J  .14  12  "12:  RA1I0 OF  10  p<.05  P<«01  "10  SIGMOID DISPLAYS :  8  •'8  p <.001  THRUSTS 6  6  4  L4  G UA  G PJA  .00  .08 Stream v e l o c i t y  Figure  12.  (m/sec)  Ratio of sigmoid d i s p l a y s : t h r u s t s i n r e l a t i o n t o stream v e l o c i t y . ' P r o b a b i l i t y v a l u e s a r e from t h e Mann-Whitney U t e s t , 1 - . t a i l e d f o r C < P, G < U A . C = C a p a r o , P = P a r i a , G = Guayamare, UA = U p p e r A r i p o .  66 males and t h e headstream  r a t i o s of sigmoid displays  were s i g n i f i c a n t l y h i g h e r i n b o t h s t r e a m The  p r e d i c t i o n t h a t headstream- f i s h  : thrusts  conditions. are b e t t e r able to  m a i n t a i n c o u r t s h i p i n f a s t - f l o w i n g water than lowland f i s h n o t supported^ l i k e l y because v e l o c i t y used the  o f the r e l a t i v e l y  d u r i n g the experiment.  slow  was  stream  Unlike Experiment I ,  e f f e c t o f a f a s t v e l o c i t y was n o t a c t u a l l y  tested.  D i f f e r e n c e s i n t h e f r e q u e n c i e s o f t h r u s t s and s i g m o i d d i s p l a y s i n Experiment  I b e t w e e n 0.03  (the.two slowest v e l o c i t i e s ;  m/sec a n d 0.07  6 a n d 7)  Figs.  are a c t u a l l y  consistent w i t h the r e s u l t s obtained i n t h i s between s t i l l  water  (0.00  m/sec) a n d 0.08  m/sec  experiment  m/sec.  I n both  experiments t h r u s t s increased s l i g h t l y  and s i g m o i d  u s u a l l y d i d n o t change s i g n i f i c a n t l y .  Only a t the h i g h e r  velocities  i n Experiment  stream v e l o c i t y  evident.  I were t h e e f f e c t s o f i n c r e a s i n g The r e s u l t s o f t h e two e x p e r i m e n t s ,  h o w e v e r , c a n n o t be c o m p a r e d d i r e c t l y b e c a u s e for II  d i f f e r e n t periods of time. examined f i s h  in still  displays  water  (0.00  they tested  In addition,  Experiment  m/sec) w h i c h r e p r e s e n t s  a c o n d i t i o n v e r y d i f f e r e n t from t h a t o f f l o w i n g water, of  a slow v e l o c i t y ,  s i n c e f i s h .doynot o r i e n t a t e  even  upstream  a n d m a l e s p m a y show h i g h e r t h a n n o r m a l r a t e s o f c o u r t s h i p , still  w a t e r m a l e s may o r i e n t a t e  fish  to females  a^dvn c o u r t ' I  In  them  f r o m any d i r e c t i o n . As p r e v i o u s l y , n o t e d , I c h o s e  t h e 0.08  m/sec v e l o c i t y f o r  t h i s e x p e r i m e n t b e l i e v i n g i t t o be a r e a s o n a b l y f a s t s i n c e f i s h were t o be m a i n t a i n e d i n i t f o r a f u l l I  h a d assumed t h a t a s l o w e r v e l o c i t y  velocity  week.  than the f a s t e r  velocities  o f E x p e r i m e n t I s h o u l d he u s e d , s i n c e i n E x p e r i m e n t I were m a i n t a i n e d i n t h e v e l o c i t y  f o r o n l y one  day.  The  o b t a i n e d here c o n t r a d i c t t h i s assumption, s i n c e the o f a f a s t s t r e a m v e l o c i t y were n o t o b t a i n e d . p e r h a p s due experiment.  T h i s was  g u p p i e s had p r e v i o u s l ' e x p e r i e n c e  and w o u l d t h e r e f o r e l i k e l y be l i t t l e  results  effects  t o the use o f w i l d - c a u g h t g u p p i e s d u r i n g These  fish  also  this  i n streams  a f f e c t e d by a s l o w  velocity. Gonopodial  Swings  The mean n u m b e r s o f g o n o p o d i a l s w i n g s p e r f o r m e d b y s t o c k i n t h e two  stream c o n d i t i o n s are g i v e n i n F i g u r e  four stocks performed s l i g h t l y  Comparing  13.  A l l  fewer g o n o p o d i a l swings i n the  f l o w i n g w a t e r c o n d i t i o n , t h i s d i f f e r e n c e was o n l y f o r the Caparo  each  significant  s t o c k (p<.01, W i l c o x o n t e s t ) .  s t o c k s , l o w l a n d m a l e s g e n e r a l l y p e r f o r m e d more  g o n o p o d i a l s w i n g s t h a n h e a d s t r e a m m a l e s and t h e were s i g n i f i c a n t b e t w e e n  differences  Guayamare and U p p e r A r i p o m a l e s i n  both stream c o n d i t i o n s ( F i g . 1 3 ) .  These  c o n s i s t e n t w i t h the d i f f e r e n c e s between  d i f f e r e n c e s are Caparo  and  Paria  stocks i n Experiment I. ( C o r r e l a t i o n s b e t w e e n m a l e s i z e and s i g m o i d d i s p l a y s , t h r u s t s and g o n o p o d i a l s w i n g s a r e p r e s e n t e d f o r t h i s i n the  Appendix.)  experiment  4-0  h4o p  MEAN NUMBER OF  30 A  <.001 p <.025  N.S.  GONOPODIAL SWINGS PER MALE PER 40 MINS  N.S.  20  20  10  10  G fcJA  KJA  . 00  .08 Stream v e l o c i t y  Figure  .30  13.  (m/sec)  Number o f g o n o p o d i a l s w i n g s i n r e l a t i o n t o s t r e a m v e l o c i t y . Means ± 95% c o n f i f e n c e i n t e r v a l s . P r o b a b i l i t y v a l u e s a r e f r o m t h e M a n n - W h i t n e y U - t e s t , 1 - t a i l e d f o r C > P, G^>UA. C = C a p a r o , P = P a r i a , G = Guayamare, UA = U p p e r A r i p o .  69 S i d e - s w i t c h e s , Leaps," C o p u l a t i o n A t t e m p t s , Table  and  Copulations  X I I g i v e s t h e mean n u m b e r s o f s i g m o i d  s i d e - s w i t c h e s , l e a p s , and  c o p u l a t i o n attempts  m a l e s o f e a c h s t o c k i n t h e two g i v e s the percentages  f o l l o w e d by  l e a p s and  These b e h a v i o u r therefore not  in still  patterns occurred statistically.  i n f r e q u e n t l y and A decrease  two  P a r i a f e m a l e was  velocity  to  one  their  experiment.  t o a Guayamare m a l e ,  r e c e p t i v e t o a C a p a r o m a l e , and  c o p u l a t i o n was  P a r i a m a l e and  copulation  d u r i n g the  r e c e p t i v e t o an U p p e r A r i p o m a l e .  one  was  w a t e r t h r e e U p p e r A r i p o f e m a l e s were r e c e p t i v e :  t o U p p e r A r i p o m a l e s and  f e m a l e was  were  water.  O n l y s i x c o p u l a t i o n s were o b s e r v e d While i n s t i l l  displays  attempts.  performed i n f l o w i n g water r e l a t i v e  frequency  I t also  of sigmoid  g e n e r a l l y s e e n i n t h e f r e q u e n c i e s o f l e a p s and attempts  by  d i s p l a y s during which s i d e -  the percentages  copulation  analyzed  performed  stream c o n d i t i o n s .  of sigmoid  switch.es w e r e p e r f o r m e d and  d i s p l a y Y'  female.  observed  and  one  one Guayamare  I n t h e 0.08  i t was  m/sec  between a  T h i s s m a l l number o f c o p u l a t i o n s a t  l e a s t i n d i c a t e s t h a t f e m a l e s w i l l mate w i t h m a l e s f r o m  both  lowland  own  and  headstream p o p u l a t i o n s r e g a r d l e s s of t h e i r  p o p u l a t i o n of o r i g i n . however were too  Direct observations  of  copulations  i n f r e q u e n t t o draw f u r t h e r c o n c l u s i o n s  r e g a r d i n g s e x u a l s e l e c t i o n by  females.  70 Table X I I .  Mean number a n d p e r c e n t a g e o f S i g m o i d D i s p l a y s w i t h o r f o l l o w e d by S i d e - s w i t c h e s , L e a p s , and C o p u l a t i o n A t t e m p t s f o r males f r o m f o u r s t o c k s i n two s t r e a m c o n d i t i o n s .  Mean number o f S i g m o i d Display Side-switches / m a l e / 40 m i n s Stream v e l o c i t y (m/ s e c )  Caparo Paria Guayamare Upper A r i p o  .08  .00  .08  1.4 2.0 1.8 0.8  0.3 1.3 2.0 1.2  4.0 2.1 3.4 1.1  0.9 1.7 3.8 1.6  Stream v e l o c i t y (m/sec)  Percentage of Displays F o l l o w e d by Leaps Stream v e l o c i t y (m/sec)  .00  .08  .00  .08  0.9  0.6 0.4  2.6  2.0  1.0  2.2  3.1  1.-5 2.2  Mean number o f Copulation Attempts / m a l e / 40 m i n s Stream v e l o c i t y (m/sec)  Caparo Paria Guayamare Upper A r i p o  Stream v e l o c i t y (m/sec)  .00  fie;an number o f L e a p s / m a l e / 40 m i n s  Caparo Paria Guayamare Upper A r i p o  Percentage of Sigmoid Displays with Side-switches  1.1  4.2 4.0  0.5 2.8 2.9  Percentage of Sigmoid D i s p l a y s f o l l o w e d by Copulation Attempts Stream v e l o c i t y (m/sec)  .00  .08  .00  .08  0.1 0.3 0.4 0.3  o.o 0.2 0.2 o.'3  0.3 0.3 0.8 0.3  o.o 0.2 0.4 0.4  71  C o u r t s h i p B o u t s and t h e Number o f B e h a v i o u r P a t t e r n s p e r Courtship  Bout  T a b l e X I I I g i v e s t h e mean number o f c o u r t s h i p p e r f o r m e d b y m a l e s o f e a c h p o p u l a t i o n i n t h e two conditions.  bouts  stream  As p r e d i c t e d , m a l e s f r o m t h e h e a d s t r e a m  p e r f o r m e d more c o u r t s h i p b o u t s t h a n l o w l a n d m a l e s .  stocks The  d i f f e r e n c e s were s i g n i f i c a n t b e t w e e n P a r i a and C a p a r o both stream c o n d i t i o n s . a tendency  H e a d s t r e a m m a l e s may  have e v o l v e d  t o p e r f o r m more c o u r t s h i p b o u t s i n o r d e r t o m a i n t a i n  an o p t i m a l number o f c o u r t s h i p b o u t s i n f a s t - f l o w i n g Comparing each p o p u l a t i o n w i t h i t s e l f c o n d i t i o n s , no  water.  i n t h e two  (Table X I I I ;  T h e r e f o r e , i n c o n t r a s t t o e x p e c t a t i o n , an  i n s t r e a m v e l o c i t y d i d n o t d e c r e a s e t h e number o f  increase courtship  E i t h e r my  v e l o c i t y u s e d was  n o t f a s t enough t o d e t e c t the e f f e c t  The  h y p o t h e s i s was  Wilcoxon  bouts performed.  stream v e l o c i t y  stream  s i g n i f i c a n t d i f f e r e n c e s were f o u n d i n t h e  number o f c o u r t s h i p b o u t s p e r f o r m e d test).  in  wrong o r the  stream of  on t h e f r e q u e n c y o f c o u r t s h i p b o u t s .  p r o p o r t i o n o f c o u r t s h i p b o u t s w i t h one,  two,  and  t h r e e o r more s i g m o i d d i s p l a y s and t h r u s t s i s shown i n F i g u r e 14. Headstream males d i d not d i f f e r from l o w l a n d males i n the number o f b e h a v i o u r p a t t e r n s p e r f o r m e d i n d i v i d u a l courtship bouts. performed o f one,  to females during  I n f a c t , both c l a s s e s of  remarkably s i m i l a r p r o p o r t i o n s of bouts  two,  fish  comprised  and t h r e e o r more c o u r t s h i p b e h a v i o u r p a t t e r n s .  T h i s r e s u l t " l e a d s me  t o s p e c u l a t e t h a t , once a m a l e b e g i n s  c o u r t i n g a f e m a l e , t h e r e i s an o p t i m a l number o f s i g m o i d d i s p l a y s and t h r u s t s f o r w h i c h  i t i s advantageous  f o r the  72  Table X I I I .  Mean number o f c o u r t s h i p b o u t s p e r m a l e f o r e a c h s t o c k i n two s t r e a m c o n d i t i o n s .  Mean number o f c o u r t s h i p b o u t s * p e r male p e r 40 mins Stream velocity (m/sec)  Difference** between stocks P  . 00  Caparo  32.9  Paria  78.0  Guayamare Upper A r i p o  Difference** between stocks  (m/sec)  P  .08  <.Q2£  32.5 64.7  4 6 . 7 5 4 . 9  Stream velocity  N.S.  <OQ2'5  49.1  N.S. 52.5  *A c o u r t s h i p b o u t i s d e f i n e d a s a s e r i e s o f consecutive sigmoid d i s p l a y s and/or t h r u s t s p e r f o r m e d b y a m a l e t o t h e same f e m a l e . **Mann-Whitney U - t e s t ,  1 - t a i l e d f o rP >  C, U A >  G.  G  80 -  G UA  70 60 PROPORTION OF  50  COURTSHIP BOUTS  40'  IN PERCENT  30  20' 10 i  1 2 3+ 1 2 3+  123+  1 2 3+  1 2 3+  1 2 3+  .00  1 2 3+  1 2 3+  .08 Stream v e l o c i t y  (m/sec)  NUMBER OF BEHAVIOUR PATTERNS PER BOUT Figure  14.  P r o p o r t i o n o f c o u r t s h i p b o u t s w i t h o n e , t w o , a n d t h r e e o r more behaviour patterns p e r courtship bout. C = C a p a r o , P = P a r i a , G = Guayamare, UA = U p p e r A r i p o .  male t o p e r f o r m .  P e r h a p s m a l e s do n o t i n c r e a s e t h e i r  chance  o f m a t i n g s u c c e s s b y p e r f o r m i n g more "faehaviour p a t t e r n s to  t h e same f e m a l e d u r i n g a c o u r t s h i p b o u t .  g r e a t e r advantage or  I t may be o f  t o l e a v e the female a f t e r  one o r two d i s p l a y s  t h r u s t s and seek o u t a n o t h e r f e m a l e . For  one,  each s t o c k the p r o p o r t i o n s o f c o u r t s h i p bouts  with  t w o , a n d t h r e e o r more b e h a v i o u r p a t t e r n s were ve.ryy  s i m i l a r under both c o n d i t i o n s ( F i g . 14). did not affect  Stream  t h e number o f b e h a v i o u r p a t t e r n s  velocity performed  during courtship bouts. Mate P r e f e r e n c e o f M a l e s Males from both headstream  populations exhibited  p r e f e r e n c e f o r f e m a l e s o f t h e i r own s t o c k ,  a  consistently  p e r f o r m i n g more s i g m o i d d i s p l a y s a n d t h r u s t s t o h e a d s t r e a m females i n both stream c o n d i t i o n s the  (Table XIV).  two l o w l a n d s t o c k s , h o w e v e r , v a r i e d  Males  from  i n t h e i r mate p r e f e r e n c e .  Caparo males e x h i b i t e d a s i g n i f i c a n t p r e f e r e n c e f o r females o f t h e i r own s t o c k when o b s e r v e d i n f l o w i n g w a t e r , w h e r e a s Guayamare m a l e s . c o u r t e d h e a d s t r e a m f r o m t h e i r own s t o c k . similar  i n both s t i l l  f e m a l e s more t h a n f e m a l e s  Mate p r e f e r e n c e s were and f l o w i n g w a t e r  generally  conditions.  I t h a s o f t e n b e e n assumed t h a t male g u p p i e s a r e v e r y promiscuous,  c o u r t i n g a l l f e m a l e s r e g a r d l e s s o f s t o c k , and t h a t  s e x u a l s e l e c t i o n i s e x e r c i s e d o n l y by females ( H a s k i n s e t a l . , 196ls  Farr,  1 9 7 6 ,1 9 7 7 ;  and E n d l e r ,  I98O).  In this  experiment  three of the f o u r p o p u l a t i o n s e x h i b i t e d a preference f o r f e m a l e s o f t h e i r own p o p u l a t i o n , a s p r e d i c t e d .  They d i d n o t  75  Table XIV.  Males  P e r c e n t a g e o f s i g m o i d d i s p l a y s and t h r u s t s p e r f o r m e d b y m a l e s t o f e m a l e s o f t h e i r own or another stock.  Females Courted  Percentage o f t o t a l sigmoid displays -, Stream v e l o c i t y (m/sec)  .00  Caparo  Paria  Guayamare  U.  Aripo  .08  Percentage o f t o t a l thrusts Stream v e l o c i t y (m/sec)  .00  .08  48.8  65.0** 35-0  49.7 50.3  68.9** 31.1  48.1  Paria  37.8 62.2**  30.1 69.9**  40.7 59.3*  Guayamare  41.0  42.1  49.0 51.0  39.0 61.0  46.0  34.3 65.7*  Caparo Paria C aparo  51.2  U. A r i p o  59.0  Guayamare  41.6  U.  Aripo  p <.0:25 P <• 005  58.4  51.9  57-9 43.0 57-0  54.0  Wilcoxon test, one-tailed f o r a preference f o r f e m a l e s f r o m t h e same p o p u l a t i o n a s m a l e s ( b a s e d on raw d a t a and n o t t h e p e r c e n t a g e s shown).  simply court females The  reasons  randomly.  f o r t h e mate p r e f e r e n c e s e x h i b i t e d by  p o p u l a t i o n s of males are not for  females  responses  may,  a t l e a s t i n p a r t , be  t o male c o u r t s h i p .  mate p r e f e r e n c e s may males.  entirely  clear.  i n f l u e n c e d by  a c t u a l l y r e f l e c t female or not,  some i n t e r - p o p u l a t i o n d i s c r i m i n a t i o n and inter-population breeding.  The  The  t h i s may  play i n  cooperation i s I966).  During  e v e n when m a l e s e x h i b i t e d a p r e f e r e n c e they  still  d i r e c t e d a t l e a s t 30%  s e x u a l s e l e c t i o n i n P.  for of  of the a l t e r n a t e s t o c k .  sexual selection could s t i l l  r e s u l t s of t h i s experiment  Future  restrict  therefore  t h a t females  for successful copulation (Liley,  stock of females  entirely  indicate  i s o l a t i n g mechanisms between p o p u l a t i o n s .  t h e i r c o u r t s h i p towards females  The  of  f a c t t h a t males e x e r c i s e a choice i n t h e i r c o u r t s h i p  the experiment,  Therefore  t h e n male  the r e s u l t s  s e x u a l s e l e c t i o n , e s p e c i a l l y s i n c e female  one  female  selection  p r e f e r e n c e s may  does n o t n e c e s s a r i l y a l t e r the r o l e  critical  preference  I f t h i s i s the case,  Whether t h i s i s the case  represent p a r t i a l  Male  the  be  e x e r c i s e d by  do,lihowever,  indicate  females.  that  r e t i c u l a t a i s not n e c e s s a r i l y  c o n t r o l l e d by f e m a l e  c h o i c e and  inter-male  competition.  s t u d i e s on i n t e r - p o p u l a t i o n s e x u a l s e l e c t i o n i n  t h e guppy s h o u l d e x a m i n e b o t h m a l e and  female  mate  preferences.  77 Summary o f R e s u l t s P o p u l a t i o n d i f f e r e n c e s i n the f r e q u e n c i e s o f "behaviour p a t t e r n s between w i l d - c a u g h t headstream  courtship and l o w l a n d  f i s h were c o n s i s t e n t w i t h d i f f e r e n c e s found between the Caparo  ( l o w l a n d ) and P a r i a ( h e a d s t r e a m )  Experiment  I.  stocks tested i n  L o w l a n d m a l e s were a g a i n f o u n d t o u s e  fewer  s i g m o i d d i s p l a y s and more t h r u s t s and g o n o p o d i a l s w i n g s headstream  males.  than  S i n c e b o t h p a i r s o f p o p u l a t i o n s showed  r e s u l t s c o n s i s t e n t w i t h t h o s e o b t a i n e d p r e v i o u s l y i t seems reasonable to suggest t h a t the d i f f e r e n c e s observed r e p r e s e n t a t i v e of headstream The  are  and l o w l a n d p o p u l a t i o n s i n g e n e r a l .  e f f e c t o f s t r e a m v e l o c i t y on m a l e c o u r t s h i p b e h a v i o u r  c l e a r l y demonstrated  i n E x p e r i m e n t I was much l e s s  i n t h i s experiment.  A l t h o u g h the f r e q u e n c i e s o f s i g m o i d  d i s p l a y s and g o n o p o d i a l s w i n g s g e n e r a l l y d e c r e a s e d  pronounced  slightly  i n f l o w i n g w a t e r compared t o s t i l l w a t e r , i n most c a s e s the d e c r e a s e s were n o t s i g n i f i c a n t . the p r e d i c t e d g r e a t e r decrease headstream  males.  L o w l a n d m a l e s d i d n o t show i n t h e i r courtship behaviour than  T h i s i s b e l i e v e d t o be due  to the  slow  s t r e a m v e l o c i t y u s e d d u r i n g t h i s e x p e r i m e n t and t h e f a c t w i l d - c a u g h t g u p p i e s were  tested.  As p r e d i c t e d , h e a d s t r e a m  m a l e s p e r f o r m e d more  b o u t s t h a n l o w l a n d m a l e s and t h i s may to stream v e l o c i t y .  that  courtship  r e p r e s e n t an a d a p t a t i o n  A l l p o p u l a t i o n s performed r o u g h l y the  same number o f b e h a v i o u r p a t t e r n s d u r i n g c o u r t s h i p b o u t s , s u g g e s t i n g t h a t m a l e s may  p e r f o r m an o p t i m a l number o f s i g m o i d  d i s p l a y s and t h r u s t s t o i n d i v i d u a l f e m a l e s b e f o r e l e a v i n g  the  female  and c o u r t i n g a n o t h e r  one.  T h r e e o f t h e f o u r p o p u l a t i o n s e x h i b i t e d a mate of t h e i r  own p o p u l a t i o n .  T h e s e mate  preference  for  females  preferences  may  r e p r e s e n t p a r t i a l i s o l a t i n g mechanisms between p o p u l a t i o n s .  79  CHAPTER V I  GENERAL DISCUSSION The  E v o l u t i o n of Behaviour In  my  and M o r p h o l o g y i n P.  this discussion I f i r s t  experiments  and n o t e  reticulata  b r i e f l y r e v i e w the r e s u l t s  t h a t they provide evidence  a d a p t a t i o n to stream v e l o c i t y .  Then I r e v i e w the  on n a t u r a l p o p u l a t i o n s o f t h e g u p p y , c o m b i n i n g those  of o t h e r s , t o develop  have l i k e l y  an o v e r v i e w  of b e h a v i o u r a l s t u d i e s done  my  findings with  of the f a c t o r s  which  a c t e d as s e l e c t i o n p r e s s u r e s t o mold the  p r e s e n t m o r p h o l o g y and b e h a v i o u r . r e s u l t s on m a l e mate p r e f e r e n c e s  Finally, and  of  guppy's  I consider  my  the p o s s i b l e f o r m a t i o n  o f b e h a v i o u r a l i s o l a t i n g mechanisms. S t u d i e s of the e c o l o g i c a l f a c t o r s t h a t are in  important  t h e e v o l u t i o n and m a i n t e n a n c e o f b e h a v i o u r : i n a p o p u l a t i o n  a r e b e c o m i n g i n c r e a s i n g l y common ( s e e B r o w n , 1 9 7 5 ; K r e b s Davies,  1 9 7 8 ; and K e e n l e y s i d e ,  1979).  Many o f t h e s t u d i e s ,  h o w e v e r , do n o t go b e y o n d n o t i n g c o r r e l a t i o n s b e h a v i o u r a l d i f f e r e n c e s and  environmental  t h e s i s , however, I went beyond n o t i n g such My  l a b o r a t o r y experiments  between  factors.  is  and  adapted to stream In  In  this  correlations.  on n a t u r a l p o p u l a t i o n s o f  t e s t e d s e v e n p r e d i c t i o n s b a s e d on t h e h y p o t h e s i s s o c i a l behaviour,  and  guppies  t h a t guppy  s p e c i f i c a l l y guppy c o u r t s h i p  behaviour,  velocity*conditions.  E x p e r i m e n t I , l o w l a n d and h e a d s t r e a m guppy p o p u l a t i o n s  showed a l l o f t h e p r e d i c t e d b e h a v i o u r a l d i f f e r e n c e s . b r e d f r o m a l o w l a n d p o p u l a t i o n showed g r e a t e r  Fish  cohesion,  80 l e s s aggressive behaviour, s u r f a c e r e g i o n o f stream males performed gonopodial differences  fewer  in  f o r the  tanks than headstream f i s h .  Lowland  s i g m o i d d i s p l a y s b u t more t h r u s t s a n d  swings than headstream males. i n male c o u r t s h i p b e h a v i o u r  i n Experiment I I . very l i k e l y  and a g r e a t e r p r e f e r e n c e  Similar population were a g a i n  found  Thus, these b e h a v i o u r a l d i f f e r e n c e s a r e  r e p r e s e n t a t i v e o f l o w l a n d and h e a d s t r e a m p o p u l a t i o n s  general. The  p e r s i s t e n c e of the b e h a v i o u r a l d i f f e r e n c e s i n  l a b o r a t o r y r a i s e d descendants o f i s o l a t e d p o p u l a t i o n s  proves  a g e n e t i c c o n t r i b u t i o n t o t h e d i f f e r e n c e s (Ehrman and P a r s o n s ,  I976).  Such g e n e t i c d i f f e r e n c e s a r e presumably the p r o d u c t  o f n a t u r a l s e l e c t i o n and r e p r e s e n t e v o l u t i o n a r y a d a p t a t i o n s . The  d i r e c t e f f e c t o f stream v e l o c i t y  b e h a v i o u r was c l e a r l y stocks of guppies gonopodial increased.  on m a l e c o u r t s h i p  demonstrated i n Experiment I .  the frequency  swings decreased  o f s i g m o i d d i s p l a y s and  markedly as stream  The b e s t e v i d e n c e  For a l l  velocity  of behavioural adaptation to  s t r e a m v e l o c i t y was o b t a i n e d when h e a d s t r e a m m a l e s w e r e to  be b e t t e r a b l e t o m a i n t a i n t h e i r r a t i o  found  of sigmoid d i s p l a y s :  t h r u s t s than l o w l a n d males as stream v e l o c i t y  increased.  In  a d d i t i o n , a s p r e d i c t e d , i n f a s t e r - f l o w i n g w a t e r th.e.0.sigmoid d i s p l a y s o f h e a d s t r e a m m a l e s were o f l o n g e r d u r a t i o n t h a n those  o f lowland males.  adapted  Thus, headstream males appear b e t t e r  to displaying i n fast-flowing  The  higher ratio  water.  of sigmoid d i s p l a y s : t h r u s t s exhibited  b y h e a d s t r e a m m a l e s may  i t s e l f r e p r e s e n t an a d a p t a t i o n t o  stream  sigmoid d i s p l a y s decrease  velocity.  Since  more  than  t h r u s t s w i t h i n c r e a s i n g stream v e l o c i t y , males l i v i n g i n f a s t - f l o w i n g w a t e r may h a v e e v o l v e d t h e t e n d e n c y t o p e r f o r m a higher ratio  of sigmoid displays  in  i n order to s t i l l  slow water)  r a t i o when i n f a s t - f l o w i n g  : thrusts  (when o b s e r v e d  be p e r f o r m i n g a t a n o p t i m a l  water.  Although differences i n the frequency of performing c o u r t s h i p b e h a v i o u r p a t t e r n s b e t w e e n p o p u l a t i o n s were t h e same i n b o t h e x p e r i m e n t s , t h e d i r e c t e f f e c t o f s t r e a m  velocity  on m a l e c o u r t s h i p b e h a v i o u r was l e s s p r o n o u n c e d i n E x p e r i m e n t I I . T h i s was l i k e l y this  due t o t h e s l o w s t r e a m v e l o c i t y u s e d d u r i n g  experiment. S t r e a m v e l o c i t y was f o u n d t o d i r e c t l y a f f e c t  depth l o c a t i o n i n Experiment I . a decrease  guppy  Increasing velocity  i n the time spent a t the t o p o f the stream  by l o w l a n d f i s h .  F i s h from the i n t e r m e d i a t e v e l o c i t y  produced tank spring  p o p u l a t i o n , h o w e v e r , were b e t t e r a b l e t o m a i n t a i n t h e i r at  the top o f the stream tank than lowland f i s h .  likely  i n d i c a t e s another a d a p t a t i o n t o stream  position  This result  velocity.  In  a d d i t i o n , headstream f i s h  of  t h e s t r e a m i n a l l v e l o c i t i e s and I s u g g e s t t h e y e v o l v e d t h i s  preference  showed a p r e f e r e n c e f o r t h e b o t t o m  i n order to hold t h e i r position i n fast-flowing  w a t e r a n d make u s e o f t h e d e c e l e r a t i o n o o f w a t e r c l o s e t o t h e substrate. D i f f e r e n c e s between p o p u l a t i o n s o f g u p p i e s i n b o t h male c o u r t s h i p and depth l o c a t i o n appear t o r e f l e c t a d a p t a t i o n s t o d i f f e r e n t stream v e l o c i t i e s .  T h i s , h o w e v e r , d o e s n o t mean  that other environmental factors d i dnot also play a role i n shaping these behaviours.  In fact,  i t i s o f t e n wrong t o s e a r c h  82 for a single biological function b e h a v i o u r o r morphology. that  a full  assessment  o r adaptation of a piece of  I agree w i t h L i l e y and Seghers  o f the e v o l u t i o n a r y  n a t u r a l v a r i a t i o n i n t h e guppy r e q u i r e s features  o f the environment. affected  guppies.  dealing with  The s t u d i e s  (Haskins e t a l . , Liley  196I;  a n d S e g h e r s , 1975;  significance of  consideration  o f many  Both p h y s i c a l and b i o t i c  pressures haveelikely  the morphology  1975;  selection  and b e h a v i o u r o f  g u p p i e s i n Trinidad.- . 1  Seghers, 1 9 7 3 , Farr,  (1975)  1974a, 1974b;  Endler,  1978,  Ballin, 1 9 7 3 ; 1980;  and  t h i s s t u d y ) s u g g e s t t o me t h a t  the f o l l o w i n g s e l e c t i o n p r e s s u r e s  may  the observed  have i n t e r a c t e d  b e t w e e n guppy  t o produce  differences  populations;  .Physical S e l e c t i v e Agents  Morphology and B e h a v i o u r  Biotic S e l e c t i v e Agents  Colouration Size  Temperature  Courtship Behaviou Avoidance _ Behaviour Schooling Behaviour y Aggressive / Behaviour ' Depth P r e f e r e n c e '  Stream Velocity Stream Turbidity Stream Background Pattern  Sexual Selection  ( S o l i d l i n e s i n d i c a t e demonstrated evidence f o r s e l e c t i v e influences. Broken l i n e s i n d i c a t e possible s e l e c t i v e influences.) For  each c h a r a c t e r  o f morphology  and behaviour l i s t e d I w i l l  b r i e f l y review the evidence f o r s p e c i f i c f a c t o r s a c t i n g as selection pressures.  83 Male C o l o u r a t i o n .  The e x t r e m e p o l y m o r p h i s m o f m a l e  colour  p a t t e r n i n P. r e t i c u l a t a h a s l o n g b e e n n o t e d a n d t h e g e n e t i c s of c o l o u r i n h e r i t a n c e h a s been s t u d i e d i n c o n s i d e r a b l e  detail  ( W i n g e , 1922,  1947;  1927;  F i s h e r , 1930;  H a s k i n s a n d D r u z b a , 1938; Slate, Hewitt,  1944;  Winge a n d D i t l e v s e n ,  Goodrich,  H a s k i n s and H a s k i n s ,  1970;  and H a s k i n s ,  Natural populations Haskins e t a l .  (I96I)  Josephson, T r i n k h a u s , and  1951»  o f the  a balance  guppy were f i r s t  t o g a i n an understanding  s t u d i e d by  f o r the  They s u g g e s t e d  between s e x u a l s e l e c t i o n , making the  l e s s conspicuous.  Endler  patterns of populations change w i t h p r e d a t i o n  colour  that  pattern  (1978) f o u n d t h a t t h e c o l o u r  o f guppies i n the w i l d  intensity.  I n another study, E n d l e r  patterns  and p r e d a t i o n , making the  (1980)  show a m a r k e d  M a l e c o l o u r p a t t e r n s were  l e s s c o n s p i c u o u s a t h i g h , compared t o low,  selection.  Young,  i n a g i v e n n a t u r a l p o p u l a t i o n may r e p r e s e n t  b r i g h t e r a n d more v i s i b l e ,  hypothesis  Haskins,  1975)*  a n d Yamamoto,  polymorphism e x h i b i t e d i n the w i l d . colour patterns  1954;  provided  predation  intensities.  a d i r e c t t e s t o f the  t h a t male c o l o u r p a t t e r n i s s u b j e c t t o n a t u r a l I n l o n g term l a b o r a t o r y and f i e l d  demonstrated t h a t p r e d a t i o n  e x p e r i m e n t s he  i n t e n s i t y and stream background  c o l o u r p a t t e r n s have p r e d i c t e d e f f e c t s on the  colour  patterns  o f male g u p p i e s .  G u p p i e s became l e s s c o n s p i c u o u s a t h i g h e r  compared t o l o w e r  predation intensity.  I n addition,  sexual  s e l e c t i o n by females appeared t o produce males as d i f f e r e n t f r o m t t h e i r stream background as p o s s i b l e . In l a b o r a t o r y choice populations, B a l l i n  (1973)  e x p e r i m e n t s u s i n g n a t u r a l guppy found t h a t b r i g h t c o l o u r a t i o n o f  males  d i d not influence  laboratory prefer  female  only  display rates.  does n o t i n f l u e n c e  He  o f mates.  (1980a)  s t r a i n s of guppies, Farr  conspicuous males  courtship  choice  i f a l l males  Using  found that  e x h i b i t equal  s u g g e s t s t h a t male  female choice  colouration  of males but r a t h e r  females p r e f e r males w i t h h i g h e r d i s p l a y r a t e s . e x p e r i m e n t s male r e p r o d u c t i v e by d e t e r m i n i n g t h e p a r e n t a g e  s u c c e s s was  s e l e c t e d males It  with  thus appears t h a t  whose c o l o u r a t i o n background  f e m a l e s a r e more r e c e p t i v e  I98O)  1980a)•  Male  i n male  Size.  adult  males stream  and s e x u a l  group  selection  t o a c t as s e l e c t i o n p r e s s u r e s p r o d u c i n g -  colouration.  inter-population  differences  different  were r a i s e d a t d i f f e r e n t t e m p e r a t u r e s h a v e differences  guppies, p a r t i c u l a r l y males,  genetic  to  E x p e r i m e n t s i n w h i c h g u p p i e s f r o m two  natural populations indicated that  patterns.  o t h e r males w i t h i n a  Both predation  have been demonstrated variability  o r 2)  1980a)  females  i s d i f f e r e n t from e i t h e r l ) t h e i r  (Endler,  1977i  (Farr,  (1977»  Farr  colour  his  directly  of competing males,  l e s s frequent or rare  that  (During  measured  of o f f s p r i n g . )  a l s o found t h a t w i t h i n a group  females  i n the s i z e  of  are p a r t l y determined  by  and a r e p a r t l y a p h e n o t y p i c r e s p o n s e  to  environmental temperature c o n d i t i o n s Evidence that predation  ( L i l e y and S e g h e r s ,  i s s i z e - s e l e c t i v e has a l s o  been  p r o v i d e d b y e x p e r i m e n t s i n w h i c h g u p p i e s were e x p o s e d  to  a v a r i e t y o f n a t u r a l p r e d a t o r s (Seghers, 1973;  and  Seghers,  1975)•  factor involved i n male  size.  Thus s i z e s e l e c t i v e p r e d a t i o n  Liley may  1975)*  a l s o be  i n the e v o l u t i o n of i n t e r - p o p u l a t i o n  a  differences  85 Liley  (1975)  and Seghers  s u g g e s t t h a t b o d y s i z e may be  a d a p t e d t o s t r e a m v e l o c i t y a n d p e r h a p s a l s o r e p r e s e n t some form o f mating advantage.  L a r g e body s i z e m i g h t a l l o w  fish  t o b e t t e r m a n o e u v r e i n f a s t - f l o w i n g s t r e a m s , a n d t h u s g a i n them an advantage predation.  i n i n t r a - s p e c i f i c b e h a v i o u r and escape  (l94l)  (Hubbs  from  has noted t h a t f i s h l i v i n g  i n faster  stream v e l o c i t i e s are g e n e r a l l y l a r g e r than those i n slowerf l o w i n g water.) if  S e x u a l s e l e c t i o n s h o u l d fa.vor l a r g e r  f e m a l e s choose  larger  (and presumably  fitter)  N e i t h e r o f t h e s e p o s s i b i l i t i e s have a s y e t been experimentally.  guppies  males. tested  O n l y c o r r e l a t i o n s b e t w e e n guppy s i z e a n d s t r e a m  v e l o c i t y have been n o t e d . The fish  e f f e c t o f s e x u a l s e l e c t i o n and stream v e l o c i t y on  s i z e c o u l d be t e s t e d b y m a i n t a i n i n g g u p p i e s u n d e r  stream v e l o c i t i e s f o r s e v e r a l g e n e r a t i o n s . c o u l d determine whether s m a l l males  l a r g e r males  Such  been found"to e l i c i t  Headstream  d i f f e r e n t responses fromttwo p o p u l a t i o n s (Seghers,  1973,  m a l e s moved i n t o d e e p e r w a t e r a n d r e m a i n e d  q u i e s c e n t w h i l e l l o w l a n d males Seghers  velocities.  o f a e r i a l p r e d a t o r s have  o f guppies and t h e i r l a b o r a t o r y - r e a r e d progeny  1974a) •.  experiments  a r e more s u c c e s s f u l than-',  i n mating with females a t d i f f e r e n t  A v o i d a n c e Behaviour.-.. M o d e l s  different  d i d s o t o a much l e s s e r  degree.  suggests that t h i s genetic v a r i a t i o n i n behaviour  r e f l e c t s d i f f e r e n c e s i n s e l e c t i o n pressures e x e r t e d by aquatic versus a e r i a l Cohesion.  predators.  G r o u p c o h e s i o n o r s c h o o l i n g may h a v e e v o l v e d  as a n a n t i - p r e d a t o r s t r a t e g y  (Shaw,  1970)•  I n laboratory  experiments, Seghers ( 1 9 7 3 * of guppies having less vulnerable  1974b)  a g r e a t e r tendency toHschool  to predation.  He  d i f f e r e n c e s between p o p u l a t i o n s with reaction distance microhabitat  the  r a t e s of sexual  activity).  along  the  He  did not,  due  d i s p l a y s and  t o the  however, t e s t t h i s  thrusts.  one  living  He  v e l o c i t y and while  behaviour. velocities  population  As n o t e d e a r l i e r ,  schooling behaviour,  have differences  i n t u r b i d water f o r the  purpose  r e l a t i o n s h i p between stream  (slow-flowing  lowland  clear),  I examined group c o h e s i o n f o u n d no  the  Rivulus.  r i v e r s are  turbid  i f turbidity affects  stream v e l o c i t y would i n d i r e c t l y a f f e c t  and  that  behaviour  s t r e a m t u r b i d i t y may  f a s t - f l o w i n g headstreams are  schooling,  higher  hypothesis.  Because of the  turbidity  aggregates  speculated  m i g h t e x p e c t f i s h t o Keep c l o s e t o g e t h e r  of communication.  low  i n streams  courtship  as a s e l e c t i v e a g e n t i n p r o d u c i n g  incschooling behaviour.  containing  displayed  i n dense  complex  dispersed  presence o r absence o f  I n a d d i t i o n to p r e d a t i o n , acted  i n streams were  and  (1975)  Farr  s t r e a m s and m a l e s e x h i b i t e d  o b s e r v e d d i f f e r e n c e s i n s c h o o l i n g and were e n t i r e l y  study,  (and  Populations  however, l i v e d  edges of the  r a t e s of sigmoid  In a field  e n t i r e s t r e a m bed  with large predators,  along  alarm threshold,  l a r g e r predators)  sparsely across  genetic  i n schooling behaviour,  of guppies l i v i n g  (and n o t  relatively  components o f a coadapted  of antipredator adaptations. found that populations  populations  were  suggested that  to predators,  s e l e c t i o n , are  Rivulus h a r t i i  demonstrated t h a t  i n several  schooling  stream  d i r e c t e f f e c t of stream v e l o c i t y  a t l e a s t w i t h i n the v e l o c i t i e s  on  tested.  87 Aggressive he  Behaviour.  Aggression  coadapted w i t h s c h o o l i n g behaviour  i n t h e guppy may s i m p l y since i t i s l o g i c a l  fishlliving  i n schools should b e l l e s s aggressive than i f  distributed  over the  stream  lowland r i v e r guppies guppies', B a l l i n  bed.  A f t e r f i n d i n g t h a t Guayamare  are l e s s a g g r e s s i v e  (1973)  suggested  that  than P a r i a headstream  t h a t aggression i n headstream  p o p u l a t i o n s may be due t o t h e a b s e n c e o f p r e d a t i o n a n d presence  o f inter-male competition f o r females.  suggested  t h a t a g g r e s s i o n may be a n i m p o r t a n t  d e t e r m i n i n g m a l e d o m i n a n c e among d o m e s t i c F a r r (1980a),  My  experiments  However, found  that  A t p r e s e n t , t h e r e i s no aggressive.  found no d i r e c t e f f e c t o f stream  velocity  Perhaps competition f o r resources,  as food, has produced i n t e r - m a l e a g g r e s s i o n i n headstream  males. at  it.  a s t o why h e a d s t r e a m m a l e s a r e  on a g g r e s s i o n i n m a l e s . such  guppies?.  increase t h e i r reproductive  i n f a c t they decreased  c l e a r reason  (1976)  factor i n  u s i n g l a b o r a t o r y s t r a i n s o f guppies,  more a g g r e s s i v e m a l e s d i d n o t success,  Gorlick  T h e r e i i s , h o w e v e r , no e v i d e n c e  for this  possibility  present. Depth Preference.  depth  preference  The p r e s u m e d g e n e t i c d i f f e r e n c e s i n  o f d i f f e r e n t guppy p o p u l a t i o n s may r e p r e s e n t  adaptations t o stream evidence  velocity.  f r o m my e x p e r i m e n t  I outlined earlier  for this possibility.  the Stream  t u r b i d i t y may a l s o h a v e s e l e c t e d f o r d i f f e r e n c e s i n  depth  preference.  Fish  evolved  a preference  f o r the  i n t u r b i d lowland waters  may h a v e  surface r e g i o n o f streams s i n c e they  would  l i k e l y be a s s i s t e d i n , . ; s c h o o l i n g a n d f i n d e a c h o t h e r more c  easily  i n the w e l l - l i t  surface region of r i v e r s .  The e f f e c t  88 of stream t u r b i d i t y behaviour)  on depth p r e f e r e n c e  i s presently being  (as w e l l as - on,other  studied (Luyten,  personal  c o m m u n i c a t i o n ) . . . Courtshit),,Behaviour. behaviour  o f P. r e t i c u l a t a h a s . b e e n s t u d i e d i n d e t a i l  C o a t e s , 1935;  and 1953;  The r e p r o d u c t i v e b i o l o g y a n d c o u r t s h i p  C l a r k a n d Aronson,' 1951;  H i l d e m a n a n d Wagner, 1954;  B r o u w e r , a n d W a t e r b o l k , 1955; and  Rosen,  I966;  Liley,  1966;  and W i s h l o w ,  o f .sigmoid  t h r u s t s i n a l a b o r a t o r y s t r a i n o f guppies. e x h i b i t e d the their prior they  He f o u n d t h a t m a l e s  only r a r e l y r e s u l t  f e m a l e s t h a n w i t h re.ee p t i v e -;.ones. t h r u s t s , which  i n successful inseminations  ( C l a r k and  A r o n s o n , 1951; B a e r e n d s e t a l . , 1955; a n d L i l e y ,  study vary  t o "rape"  does n o t  unreceptive  females.  i n t h e i r frequency  1966),  Unfortunately,  deal with natural populations  genetically  sigmoid  o f females  H o w e v e r , he f o u n d t h a t m a l e s t h r u s t more  F a r r t h e r e f o r e suggested that males u t i l i z e  order  o f guppies  his that  and r a t i o o f performing  displays s thrusts.  Working with n a t u r a l populations speculated  t h a t the  o f guppies,  Ballin.(1973)  l o w l a n d male g u p p i e s d i s p l a y l e s s  f r e q u e n t l y than headstream males because o f i n c r e a s e d in  1974).  d i s p l a y s and  o r the r e c e p t i v i t y  f r e q u e n t l y when w i t h u n r e c e p t i v e  in  Breder  same mean t o t a l number o f d i s p l a y s r e g a r d l e s s o f  sexual experience  courted.  Baerends,  R o s e n a n d T u c k e r , 196l;  Fa.rr:"..(..'1980bX s t u d i e d t h e r o l e  Breder  Rosen and Gordon,  Kadow, 1954;  and L i l e y  (eg.  lowland  rivers,  increase t h e i r r i s k  predation  a s s u m i n g m a l e s t h a t d i s p l a y more f r e q u e n t l y o f being eaten  by predators.  s u g g e s t e d t h a t , due t o p o o r v i s i b i l i t y ,  He a l s o  males i n t u r b i d  water  w o u l d " b e n e f i t l e s s f r o m d i s p l a y i n g a n d more f r o m copulations  by p e r f o r m i n g t h r u s t s .  t e s t these speculations.  Farr  attempting  However, B a l l i n d i d n o t  (1975)  previously  noted  c o r r e l a t i o n s b e t w e e n guppy c o u r t s h i p b e h a v i o u r a n d t h e p r e s e n c e of p r e d a t o r s .  He s u g g e s t e d t h a t d i f f e r e n c e s i n c o u r t s h i p  b e h a v i o u r r e f l e c t a balance between a d a p t a t i o n and  sexual  selection.by  females.  showed t h a t among l a b o r a t o r y displayed  at higher  s t r a i n s o f guppies', m a l e s w h i c h  reproductive  less frequently.  s u c c e s s t h a n m a l e s who  T h u s he d e m o n s t r a t e d t h a t  s e l e c t i o n by females favours males.  (1980a)  Farr  r a t e s were p r e f e r r e d b y f e m a l e s a n d  demonstrated greater displayed  Recently,  to predation  a high  The e f f e c t o f p r e d a t i o n  sexual  rate of displaying i n  on d i s p l a y r a t e , however,  r e m a i n s t o be t e s t e d . My f i r s t e x p e r i m e n t d e m o n s t r a t e d t h a t d i f f e r e n c e s i n c o u r t s h i p b e h a v i o u r between n a t u r a l p o p u l a t i o n s component.  I t showed t h a t c o u r t s h i p  populations  may r e p r e s e n t  velocities. exhibited',  adaptations  The h i g h e r a t e s  have a  differences  of performing sigmoid  : t h r u s t s may r e p r e s e n t  of sigmoid displays  : thrusts.  were a l s o f o u n d t o be b e t t e r a b l e  adaptations  to maintain  f a s t e r - f l o w i n g water than lowland  in  c o u r t s h i p b e h a v i o u r between p o p u l a t i o n s adatation  t o the b i o t i c  predation  and s e x u a l s e l e c t i o n .  an  to optimal  Headstream males  in  represent  displays  ratio of  f a s t e r - f l o w i n g w a t e r , a l l o w i n g them t o m a i n t a i n ratio  between  t o d i f f e r e n t stream  by h e a d s t r e a m males and t h e i r h i g h  sigmoid displays  genetic  males.  their Thus  courtship  differences  may n o t s i m p l y  s e l e c t i o n pressures  of  90 My  finding, that different populations of a species vary  genetically  i n t h e i r rates o f performing behaviour patterns  i s n o t new. W i t h i n s p e c i e s g e n e t i c v a r i a t i o n i n c o u r t s h i p b e h a v i o u r h a s p r e v i o u s l y b e e n f o u n d t o be m a i n l y and  l i k e l y polygene t i c  (see reviews by Bastock,  B r o a d h u r s t , F u l k e r , ' and W i l c o c k , 197^)  •  quantitative  1967';  and  How g e n e s a c t t o  produce d i f f e r e n t l e v e l s o f c o u r t s h i p i n d i f f e r e n t p o p u l a t i o n s remains unsolved.  (1967)  However, B a s t o c k  suggests t h a t  d i f f e r e n c e s a r e due t o d i f f e r e n t t h r e s h o l d l e v e l s mechanisms c o n t r o l l i n g The a role  such  i n the  behaviour.  above r e v i e w shows t h a t n u m e r o u s f a c t o r s h a v e p l a y e d  i n s h a p i n g each c h a r a c t e r o f the guppy*s p r e s e n t  morphology and behaviour.  My r e s u l t s ,  i n particular,  shown t h a t i t i s i n c o r r e c t t o c o n c e n t r a t e o n o n l y s e l e c t i o n p r e s s u r e s when e x a m i n i n g courtship behaviour.  have  biotic  population differences i n  Interpopulation variability  originally  a t t r i b u t e d t o p r e d a t i o n may i n f a c t a l s o be due t o a c o m b i n a t i o n of p h y s i c a l f e a t u r e s such as stream v e l o c i t y and t u r b i d i t y . To u n d e r s t a n d  the n a t u r e o f m i c r o - e v o l u t i o n a r y changes  more f u l l y we n e e d e v e n t u a l l y t o a s s e s s t h e r e l a t i v e  contributions  of d i f f e r e n t  s e l e c t i v e p r e s s u r e s i n shaping b e h a v i o u r and  morphology.  T h i s s h o u l d be p o s s i b l e b y c o n t i n u i n g t o  s t u d y n a t u r a l p o p u l a t i o n s o f t h e guppy. l o n g term experiments, velocity,  turbidity,  By p e r f o r m i n g  and s y s t e m a t i c a l l y v a r y i n g stream  a n d p r e d a t o r c o n d i t i o n s i t may be  p o s s i b l e t o evaluate these s e l e c t i v e  agents' r e l a t i v e  i n s h a p i n g guppy m o r p h o l o g y and b e h a v i o u r .  effects .  I n a d d i t i o n , u s i n g competition experiments those  similar  to  i n E x p e r i m e n t II.";' m a l e s f r o m d i f f e r e n t p o p u l a t i o n s w i t h  d i f f e r e n t c h a r a c t e r i s t i c s c o u l d be specific  t e s t e d to determine  c h a r a c t e r i s t i c s g a i n any m a t i n g  individuals.  whether  advantages f o r  T h u s , t h e guppy s h o u l d p r o v e v e r y u s e f u l i n  studying sexual s e l e c t i o n not only using l a b o r a t o r y s t r a i n s (as F a r r (1980a) has relative  and  r a t e o f c o u r t s h i p d i s p l a y s h o u l d be  It  o f male s i z e ,  also using natural populations.  The  u n d e r one  role  done)-, b u t  colouration, aggressiveness, only  c o n d i t i o n but under s e v e r a l d i f f e r e n t c o n d i t i o n s .  I s by e x a m i n i n g  n a t u r a l p o p u l a t i o n s under  c o n d i t i o n s t h a t the a d a p t i v e  significance  c h a r a c t e r i s t i c s becomes more c l e a r . understanding  s h o u l d be  gained  significance  different  of v a r i o u s  Eventually a  of the  f a c t o r s i n s h a p i n g m o r p h o l o g y and  my  assessed, not  detailed  i n t e r a c t i o n of  behaviour  and  selection  o f the  adaptive  of s p e c i f i c p o p u l a t i o n c h a r a c t e r i s t i c s .  s t u d y , a l o n g w i t h o t h e r s , have i n d i c a t e d t h a t  specific  c h a r a c t e r i s t i c s . o f guppy m o r p h o l o g y and b e h a v i o u r  are  to s p e c i f i c environmental  factors.  their relative  under d i f f e r e n t c o n d i t i o n s .  importance  I t r e m a i n s now  eventually result  different species.  inthe formation  T h i s o c c u r s when i n d i v i d u a l s  adapted  to  Adaptation of d i f f e r e n t populations to s p e c i f i c e n v i r o n m e n t s may  So f a r ,  test  o  of  from  d i f f e r e n t p o p u l a t i o n s ne? l o n g e . r s i n t e r b r e e d ( M a y r , 1970) • Although  the p o p u l a t i o n s of guppies  I studied remain  of i n t e r b r e e d i n g , i t i s i n t e r e s t i n g to note  capable  t h a t some  i n t e r - p o p u l a t i o n d i s c r i m i n a t i o n was  demonstrated d u r i n g  second experiment.  of males f o r females  The  preferences  my from  92 t h e i r own p o p u l a t i o n may r e p r e s e n t a p a r t i a l h a r r i e r t o gene f l o w b e t w e e n p o p u l a t i o n s .  Sexual s e l e c t i o n  excercised  by m a l e s ( a n d / o r f e m a l e s ) may b e m a i n t a i n i n g d i f f e r e n c e s between p o p u l a t i o n s .  H a s k i n s a n d H a s k i n s (1950)  found  a c o u r t s h i p preference by l a b o r a t o r y s t r a i n s o f males f o r f e m a l e s f r o m t h e i r own s t r a i n a n d b y w i l d - c a u g h t m a l e s f o r wild-caught females.  M y r e s u l t S j using;"differe'rit?Iwildycaught  populations, support t h e i r f i n d i n g o f i n t e r - p o p u l a t i o n discrimination. One  p o s s i b l e e x p l a n a t i o n f o r the p r e f e r e n t i a l  e x h i b i t e d b y m a l e s d u r i n g my  experiment  r e l e a s e d i f f e r e n t and i d e n t i f i a b l e  courtship  i s t h a t f e m a l e s may  pheromones.  Female g u p p i e s h a v e b e e n shown t o r e l e a s e a s e x u a l pheromone, e s p e c i a l l y d u r i n g the time o f t h e i r r e c e p t i v i t y C r o w and L i l e y ,  1979)•  The r e s p o n s e s o f m a l e s t o s e x u a l  pheromones p r o d u c e d by h e a d s t r e a m been s t u d i e d by Snyder  1976;  (Crow,  (1978)-  and l o w l a n d f e m a l e s have  She f o u n d t h a t m a l e s f r o m  each  s t o c k d i s p l a y e d t o c o n t r o l f e m a l e s more when w a t e r w h i c h h a d p r e v i o u s l y h e l d f e m a l e s f r o m t h e i r own s t o c k was a d d e d t o t h e i r t a n k - t h a n when w a t e r f r o m a n o t h e r  s t o c k was a d d e d .  T h u s , some f o r m r o f o l f a c t o r y d i s c r i m i n a t i o n may d i f f e r e n t i a t e p o p u l a t i o n s o f f e m a l e s , a n d t h i s may a c c o u n t ' f o r t h e  observed  mate p r e f e r e n c e s o f m a l e s . C o n t i n u e d s t u d y o f t h e g u p p y may p r o v i d e f u r t h e r i n t o how i s o l a t i n g m e c h a n i s m s d e v e l o p .  insight  Differences i n  c o u r t s h i p b e h a v i o u r b e t w e e n t h e guppy a n d t h r e e c l o s e l y s p e c i e s h a v e b e e n shown t o f u n c t i o n a s e t h o l o g i c a l  related  isolating  1966).  mechanisms ( H a s k i n s and H a s k i n s , 1949; L i l e y ,  In thi  s t u d y , d i f f e r e n c e s i n c o u r t s h i p " b e h a v i o u r were f o u n d b e t w e e n populations  o f guppies and a degree o f i n t e r - p o p u l a t i o n  d i s c r i m i n a t i o n e x i s t e d "between t h e p o p u l a t i o n s . adaptation  I t i s  t o d i f f e r e n t environments, perhaps s i m i l a r t o  those found i n t h i s behavioural  s t u d y , t h a t may e v e n t u a l l y " b r i n g a b o u t  i s o l a t i o n between  I n c l o s i n g , I would l i k e  populations. to stress that  predictions  about t h e r o l e s o f d i f f e r e n t s e l e c t i v e f a c t o r s and t h e i r e f f e c t s on guppy b e h a v i o u r s h o u l d field  experiments.  of examining f i s h When p o p u l a t i o n s unless  e v e n t u a l l y be t e s t e d i n  My s t u d y h a s made a p p a r e n t t h e i m p o r t a n c i n d i f f e r e n t stream v e l o c i t y c o n d i t i o n s .  are adapted t o d i f f e r e n t stream  velocities,  they a r e examined i n f l o w i n g water, t h e a d a p t i v e  significance  o f t h e i r b e h a v i o u r may be m i s i n t e r p r e t e d ^ .  My s t u d y showed t h a t d i f f e r e n c e s b e t w e e n guppy  populations  i n c o u r t s h i p b e h a v i o u r and stream depth p r e f e r e n c e represent  adaptations  t o stream v e l o c i t y .  study, these population only  as a d a p t a t i o n s  predation.  Until  d i f f e r e n c e s had been  to biotic  likely this  considered  s e l e c t i o n pressures,  such as  94 LITERATURE CITED B a e r e n d s , G.P., R. B r o u w e r , a n d H.T. W a t e r b o l k . 1955* E t h o l o g i c a l s t u d i e s on L e b i s t e s r e t i c u l a t u s ( P e t e r s ) . B e h a v i o u r 8 : 24-9-334. B a l l i n , P.J. 1 9 7 3 « Geographic v a r i a t i o n i n c o u r t s h i p behaviour o f t h e guppy, P o e c i l i a r e t i c u l a t a . M.Sc. T h e s i s . U n i v e r s i t y o f B r i t i s h Columbia. B a s t o c k , M. 1967' London. Boeseman, M. Trinidad.  Courtship:  i960. Stud.  a z o o l o g i c a l study.  Heinemann,  The f r e s h - w a t e r W i s h e s o f t h e i s l a n d o f F a u n a C u r a c a o 10: 72-153.  Boeseman, M. - 1 9 6 4 . The f r e s h - w a t e r f i s h e s o f t h e i s l a n d o f T r i n i d a d : addenda, e r r a t a , e t c o r r i g e n d a . Stud. Fauna C u r a c a o 20: 52-57. B r e d e r , C M . , J r . and CW. C o a t e s . 1935« Sex r e c o g n i t i o n i n the guppy, L e b i s t e s r e t i c u l a t u s P e t e r s . Z o o l o g i c a 19s  187-207.  B r e d e r , C M . a n d D.E. R o s e n . 1966. Modes o f r e p r o d u c t i o n i n fishes. N a t u r a l H i s t o r y P r e s s , Garden C i t y . Broadhurst,  P . L . , D.W.  1974.  F u l k e r , and J . W i l c o c k .  Behavioral genetics.  Ann. Rev. P s y c h o l .  Brown, J . L . 1 9 7 5 • The e v o l u t i o n o f b e h a v i o r . Company, New Y o r k .  25:  389-4l5«  W.W.  N o r t o n and  C l a r k , E . a n d L.R. A r o n s o n . 1 9 5 1 • Sexual behavior i n the g u p p y , L e b i s t e s r e t i c u l a t u s ( P e t e r s ) • Z o o l o g i c a 36":  49-66.  Crow, R.T. 1976. A s e x u a l pheromone i n t h e g u p p y , P o e c i l i a r e t i c u l a t a ( P e t e r s ) . B.Sc. T h e s i s , U n i v e r s i t y o f B r i t i s h Columbia. Crow, R.T.. .and N.R. L i l e y . 1979« A s e x u a l pheromone i n t h e guppy./Poecilia reticulata (Peters)C a n . J . Z o o l . 57: 184-188.  E h r m a n , L. a n d P.A. P a r s o n s . 1976". The g e n e t i c s S i n a u e r A s s o c i a t e s , S u n d e r l a n d , Mass. E n d l e r , J.A. 1 9 7 8 . A p r e d a t o r ' s v i e w o f a n i m a l patterns. E v o l . B i o l . 11: 319-364.  of behavior. color  E n d l e r , J . A . 1980. N a t u r a l s e l e c t i o n on c o l o r p a t t e r n s i n Poecilia reticulata. E v o l u t i o n 34: 76-91.  F a r r , J . A . 1975' The r o l e o f p r e d a t i o n i n t h e e v o l u t i o n o f s o c i a l b e h a v i o r r o f n a t u r a l p o p u l a t i o n s o f t h e guppy, Poecilia reticulata (Pisces : Poeciliidae). Evolution  29: 151-158.  F a r r , J . A . 1976. S o c i a l f a c i l i t a t i o n o f male s e x u a l b e h a v i o r i n t r a s e x u a l c o m p e t i t i o n , and s e x u a l - s e l e c t i o n i n the guppy, P o e c i l i a r e t i c u l a t a ( P i s c e s : P o e c i l i i d a e ) . E v o l u t i o n 30: 707-747. F a r r , J . A . 1977• M a l e r a r i t y o r n o v e l t y , f e m a l e c h o i c e b e h a v i o r , and s e x u a l s e l e c t i o n i n t h e guppy, P o e c i l i a r e t i c u l a t a Peters (Pisces : Poeciliidae). E v o l u t i o n 31'  162-168.  F a r r , J . A . 1980a. S o c i a l behavior p a t t e r n s as determinants o f r e p r o d u c t i v e s u c c e s s i n t h e guppy, P o e c i l i a r e t i c u l a t a Peters ( P i s c e s : P o e c i l i i d a e ) - an experimental study of the e f f e c t s o f intermale c o m p e t i t i o n , female c h o i c e , and s e x u a l s e l e c t i o n . B e h a v i o u r 74: 38-91• F a r r , J . A . 1980b. The e f f e c t s o f s e x u a l e x p e r i e n c e a n d f e m a l r e c e p t i v i t y on c o u r t s h i p - rape d e c i s i o n s i n male g u p p i e s Poecilia reticulata (Pisces : Poeciliidae). Anim. Behav.  28: 1195-1201.  F i s h e r , R.A. 1930. The e v o l u t i o n o f d o m i n a n c e i n c e r t a i n p o l y m o r p h i c s p e c i e s . Amer. N a t . 6 4 : 385-406. G o o d r i c h , H.B., N.O. J o s e p h s o n , J . P . T r i n k h a u s , a n d J.M. S l a t e 1944. T h e c e l l u l a r e x p r e s s i o n a n d g e n e t i c s o f t w o new genes i n L e b i s t e s r e t i c u l a t u s . G e n e t i c s 29: 584-592. G d r l i c k , D.L. 1976. Dominance h i e r a r c h i e s and f a c t o r s i n f l u e n c i n g dominance i n t h e guppy, P o e c i l i a r e t i c u l a t a (Peters). Anim. Behav. 2 4 : 3 3 6 - 3 4 6 . H a s k i n s , C.P. a n d J . P . D r u z b a . 1938. Note on anomalous i n h e r i t a n c e o f s e x - l i n k e d c o l o u r f a c t o r s i n t h e guppy. Amer. N a t . 72: 571-57^. H a s k i n s , C.P. a n d E.F. H a s k i n s . 1949. The r o l e o f s e x u a l s e l e c t i o n a s a n . i s o l a t i n g mechanism i n t h r e e s p e c i e s o f poeciliid fishes. E v o l u t i o n 3:. 16O-I69. H a s k i n s , C^P. a n d E . F . H a s k i n s . 1950. Factors governing s e x u a l s e l e c t i o n a s an i s o l a t i n g mechanism i n t h e poeciliid fish Lebistes reticulatus. P r o c . N a t . Acad. S c i e n c e s 36: 4 6 4 - 4 7 6 . H a s k i n s , C.P. a n d E.F. H a s k i n s . 1951The i n h e r i t a n c e o f certain color patterns i n wild populations o f Lebistes r e t i c u l a t u s i n T r i n i d a d . E v o l u t i o n 5: 216-225.  96 H a s k i n s , C P . and E.F. H a s k i n s . 1 9 5 4 . N o t e on a " p e r m a n e n t " experimental a l t e r a t i o n of genetic c o n s t i t u t i o n i n a n a t u r a l p o p u l a t i o n . Proc. Nat. Acad. S c i . 4 0 : 6 2 7 - 6 3 5 ' H a s k i n s , C P . , E . F . H a s k i n s , J . J . A . M c L a u g h l i n , a n d R.E. H e w i t t . 1961.. P o l y m o r p h i s m and p o p u l a t i o n s t r u c t u r e i n L e b i s t e s r e t i c u l a t u s . an . e c o l o g i c a l s t u d y . In: Vertebrate s p e c i a t i o n . ( e d . W.F. B l a i r ) , p p . 3 2 0 - 3 9 5 . U n i v e r s i t y of Texas P r e s s , A u s t i n . H a s k i n s , C P . , P. Y o u n g , R.E. H e w i t t , a n d E.F. H a s k i n s . 1 9 7 0 . S t a b i l i s e d h e t e r o z y g o s i s o f supergenes m e d i a t i n g c e r t a i n Y-linked colour patterns i n populations of Lebistes reticulatus. Heredity 2 5 : 5 7 5 - 5 8 9 . H i l d e m a n n , W.H. a n d E.D. Wagner. 1 9 5 4 . I n t r a s p e c i f i c c o m p e t i t i o n i n L e b i s t e s . Amer. N a t . 8 8 : 8 7 - 9 1 .  sperm  H i n d e , R.A. 1975• The c o n c e p t o f f u n c t i o n . I n : F u n c t i o n a n d evolution i n behaviour. ( e d s . G. B a e r e n d s , C. B e e r , and A. M a n n i n g ) , pp. 3 - 1 5 - C l a r e n d o n P r e s s , O x f o r d . H u b b s , C.L. 1 9 4 1 . Relation of hydrological conditions to speciation i n fishes. I n : A symposium on h y d r o b i o l o g y . pp. 1 8 2 - 1 9 5 . U n i v e r s i t y o f Wisconsin P r e s s , Madison. Kadow', P. 1 9 5 4 . An a n a l y s i s o f s e x u a l b e h a v i o r and r e p r o d u c t i v e p h y s i o l o g y i n t h e guppy, L e b i s t e s r e t i c u l a t u s ( P e t e r s ) . Ph.D. T h e s i s , New Y o r k U n i v e r s i t y . 1  x  K e e n l e y s i d e , M.H.A. 1 9 7 9 * D i v e r s i t y and a d a p t a t i o n i n f i s h behaviour. Springer-Verlag, Berlin. K r e b s , J.R. a n d N.B. D a v i e s . e v o l u t i o n a r y approach. Oxford.  1 9 7 8 . B e h a v i o u r a l ecology: an Blackwell Scientific Publications,  L i l e y , N.R. 1 9 6 6 . E t h o l o g i c a l i s o l a t i n g mechanisms i n f o u r sympatric species of p o e c i l i i d f i s h e s . Behaviour, Suppl. 13, 1-197. L i l e y , N.R. a n d B.H. S e g h e r s . 1 9 7 5 . Factors a f f e c t i n g the morphology and b e h a v i o u r o f g u p p i e s i n T r i n i d a d . I n : F u n c t i o n and e v o l u t i o n i n b e h a v i o u r . ( e d s . G. B a e r e n d s , C. B e e r , a n d A. M a n n i n g ) , p p . 9 2 - 1 1 8 . Clarendon Press, Oxford. L i l e y , N.R. a n d W. W i s h l o w . 1 9 7 4 . The i n t e r a c t i o n o f e n d o c r i n e and e x p e r i m e n t a l f a c t o r s i n t h e r e g u l a t i o n o f s e x u a l b e h a v i o u r i n t h e f e m a l e guppy, P o e c i l i a r e t i c u l a t a . B e h a v i o u r 48: 1 8 5 - 2 1 4 . M a y r , E. 1 9 7 0 . P o p u l a t i o n s , - s p e c i e s , and e v o l u t i o n . Harvard U n i v e r s i t y P r e s s , Cambridge.  97  R o s e n , D.E. and.JR.M. B a i l e y . 1 9 6 3 . The P o e c i l i i d f i s h e s ( C y p r i n o d o n t i f o r m e s ) , t h e i r s t r u c t u r e , z o o g e o g r a p h y , and systematics. B u l l . Amer. Mus. N a t . H i s t . 126: 5-176. R o s e n , D.E. and M. G o r d o n . 1953' F u n c t i o n a l anatomy e v o l u t i o n o f -male g e n i t a l i a i n P o e c i l i i d f i s h e s . Zoologica 38: 1-47.  and  R o s e n , D.E. and A. T u c k e r . I96I. E v o l u t i o n of secondary s e x u a l c h a r a c t e r s and s e x u a l b e h a v i o r p a t t e r n s i n a f a m i l y of v i v i p a r o u s f i s h e s (Cyprinodontiformes: Poeciliidae). Copeia I 9 6 I : . 2 0 1 - 2 1 2 . S e g h e r s , B.H. 1973• 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 the 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 the guppy, P o e c i l i a reticulata. Ph.D. T h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a . S e g h e r s , B.H. 1974a. G e o g r a p h i c v a r i a t i o n i n the r e s p o n s e s o f guppies- ; ( P o e c i l i a r e t i c u l a t a ) t o a e r i a l p r e d a t o r s . Oecologia 1 4 : 93-98. S e g h e r s , B.H. 1974b. S c h o o l i n g b e h a v i o r i n t h e guppy ( P o e c i l i a r e t i c u l a t a ) : an e v o l u t i o n a r y r e s p o n s e t o predation. E v o l u t i o n 28: 4 8 6 - 4 8 9 . Shaw, E-. 1970. S c h o o l i n g i n f i s h e s : c r i t i q u e and r e v i e w . I n : D e v e l o p m e n t and e v o l u t i o n o f b e h a v i o u r . (eds. L.R. A r o n s o n , E. T o b a c h , D.S. L e h r m a n , and J . S . Rosenblatt} pp. 4 5 2 - 4 8 0 . F r e e m a n , San F r a n c i s c o . S i e g e l , S. 1956. Nonparametric s t a t i s t i c s sciences. M c G r a w - H i l l , New Y o r k .  f o r the  behavioural  S n y d e r , B.E. 1 9 7 8 . A comparison of responses to the s e x u a l p h e r o m o n e s p r o d u c e d by two a l l o p a t r i c r a c e s o f g u p p y , ( P o e c i l i a r e t i c u l a t a . P e t e r s ) . B.Sc. T h e s i s , U n i v e r s i t y of B r i t i s h Columbia. W i n g e , 0. 1922. 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 cytological explanation. J . Genet. 12: 137-144. Winge, j^. 1927. reticulatus.  The l o c a t i o n of: e i g h t e e n . J . Genet. 1 8 : 1 - 4 2 .  genes i n L e b i s t e s  W i n g e , 0, and E. D i t l e v s e n . 1947' C o l o u r i n h e r i t a n c e and s e x d e t e r m i n a t i o n i n L e b i s t e s . H e r e d i t y 1: 6 5 - 8 3 . Yamamoto, T. 1975' h e medaka., O r v z - i a s l a t i p e s , and t h e guppy, L e b i s t e s r e t i c u l a r i s . I n : Handbook o f g e n e t i c s . V o l . 4. V e r t e b r a t e s o f g e n e t i c i n t e r e s t . ( e d . R.C. King), pp. 1 3 3 - 1 4 9 . P l e n u m P r e s s , New Y o r k . T  98 APPENDIX  C o r r e l a t i o n s between Male S i z e  and C o u r t s h i p  Behaviour  Patterns  Experiment I The  mean t o t a l  i n Experiment I  length  i s given  f o r each p o p u l a t i o n i n Figure  15•  o f males  P e t i t e Curucaye males  were s l i g h t l y  l a r g e r on average than P a r i a males and  significantly  Cp<.05)  U-test,  one t a i l e d  differences  l a r g e r than Caparo males  (Mann-Whitney  f o r C < P , C < P C , a n d P-CPC).  are consistent  with  tested  These  those found between w i l d -  caught guppies c o l l e c t e d from s i m i l a r streams (see Seghers,  1973)• Se.ghers differences genetic  (1973)  They s u g g e s t t h a t  here support the f i n d i n g that since  laboratory  that  size differences  t h e d i f f e r e n c e s were o b t a i n e d  stocks  r a i s e d u n d e r t h e same  examine whether t h e r e  differences  The d a t a o n m a l e s i z e  presented  are p a r t l y  between  conditions.  i s a r e l a t i o n s h i p b e t w e e n male  s i z e and the performance o f v a r i o u s patterns  showed  s i z e - s e l e c t i v e p r e d a t i o n may  i n the evolution o f inter-population  i n the s i z e o f mature f i s h .  To  (1975)  and p a r t l y a phenotypic response t o e n v i r o n m e n t a l  involved  genetic,  and Seghers  i n t h e s i z e o f a d u l t male g u p p i e s a r e p a r t l y  temperature. be  and L i l e y  courtship  behaviour  I l o o k e d f o r c o r r e l a t i o n s between male s i z e and t h e  frequency o f g o n o p o d i a l swings, t h r u s t s , and sigmoid T h i s was done t o d e t e r m i n e w h e t h e r , f o r e x a m p l e ,  displays.  larger  99 PC 24  23 A MALE TOTAL LENGTH  22  (MM)  21  A  20-1  19  A  18-  Figure  15«  T o t a l l e n g t h o f males t e s t e d i n Experiment I . H o r i z o n t a l l i n e s a r e means, "bars a r e 95% c o n f i d e n c e i n t e r v a l s , and v e r t i c a l l i n e s are ranges. C = C a p a r o (N = 19), P = P a r i a (N = 19), PC = P e t i t e C u r u c a y e (N = 17).  100 males w i t h i n thrusts,  a p o p u l a t i o n p e r f o r m more g o n o p o d i a l  and s i g m o i d d i s p l a y s .  I n addition,  c o r r e l a t i o n s between these v a r i a b l e s velocities, on  swings,  by comparing the  a t the four  stream  I hoped t o d e t e c t any e f f e c t o f stream v e l o c i t y  the c o r r e l a t i o n s . T h e r e w e r e o n l y two s i g n i f i c a n t c o r r e l a t i o n s  .male s i z e a n d t h e f r e q u e n c y o f v a r i o u s b e h a v i o u r (Table XV).  Two s i g n i f i c a n t c o r r e l a t i o n s  between patterns  i n thirty-six  c o m p a r i s o n s w o u l d be e x p e c t e d b y c h a n c e a l o n e a n d I attach  therefore  no m e a n i n g t o them. ' I n a d d i t i o n , no e f f e c t o f s t r e a m  velocity  on t h e c o r r e l a t i o n s was d e t e c t e d .  Ballin  (1973)  also  f o u n d no s i g n i f i c a n t  between male s i z e and c o u r t s h i p of i n d i v i d u a l males w i t h i n  correlations  behaviour patterns.  The s i z e  a p o p u l a t i o n does n o t appear t o  have a b e a r i n g on t h e i r c o u r t s h i p  activity.  Although the  P a r i a and Caparo s t o c k s d i d n o t v a r y s i g n i f i c a n t l y i n male s i z e , they d i f f e r e d s i g n i f i c a n t l y i n t h e i r courtship (see  Chapter IV).  T h u s , m a l e s o f a p p r o x i m a t e l y t h e same  s i z e but from d i f f e r e n t populations can vary g r e a t l y courtship  behaviour  activity.  i n their  The s i s e o f i n d i v i d u a l .rar.leB  Experiment I I I n E x p e r i m e n t I I , w i l d - c a u g h t U p p e r A r i p o m a l e s were significantly  ( p <.01)  were s i g n i f i c a n t l y  l a r g e r than P a r i a males, which i n turn  (p<.00l)  Guayamare m a l e s ( F i g . 16).  l a r g e r t h a n b o t h Caparo and The l o w l a n d s t o c k s d i d n o t d i f f e r  T a b l e XV.  Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s between male s i z e a n d c o u r t s h i p b e h a v i o u r p a t t e r n s and between v a r i o u s c o u r t s h i p b e h a v i o u r p a t t e r n s . S t r e am v e l o c i t y  G.S. Caparo Size  .228  Th  .050  S.D.  . 281  Petite Curucaye Size  Paria  S.D.  Th  G.S.  S.D.  Th  G.S.  .221 .310  .156  . 203  .167' .054  - .081 ;  .247  • 395*  • 399*  -.223 Th ••-.083 S.D. .332  -.296 .332  .154 •'  S i z e . -.093  -.010  .224  Th  ;  '  S.D.  .345  .418*  *p #  .180 •5295  .316  . 182 Size  -.449 .017 .312  = Male S i z e ,  <.05 '  -.346  .113 .518* .362  -.324  .064 .056  . 20  .10  .07  .03  (m/sec)  .027  S.D.  G.S.  S.D.  Th  -.017 1 .206  .063 .322  .111  -.310 .429*  • 139  • 039 •534$  .079  Th  . 202 -.018 -.302  1  .758$  -.125 .059 .474*  . 226 .276  .061 .518* .804$  .071 .352  .654*. -.264  .278 .886$ •578J  T h = T h r u s t s , S.D. = S i g m o i d D i s p l a y s ,  Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s , One-tailed test f o r positive correlations.  .043 • .720$ .624$  G.S. = G o n o p o d i a l S w i n g s  102  30 UA 28  MALE TOTAL  26  LENGTH ($M)  24  22 J  20 J  18  Figure  16.  T o t a l l e n g t h o f males t e s t e d f o r each stock. H o r i z o n t a l l i n e s a r e means, o a r s a r e 95% c o n f i d e n c e i n t e r v a l s , and v e r t i c a l l i n e s are ranges. C = C a p a r o (N = 19), P = P a r i a (N = 20), G = Guayamare (N = 17),  UA = U p p e r A r i p o  (N = 19).  significantly.  (Mann-Whitney U - t e s t , o n e - t a i l e d  two-tailed  f o r G 5 * C.) . T h e s e d i f f e r e n c e s  consistent  with  fish  differences  previously  f o r U A > P > G .yC  i n male s i z e a r e  found i n wild-caught  ( S e g h e r s , 1973)• T h e r e w e r e no c o n s i s t e n t l y  significant correlations  between  male s i z e and t h e f r e q u e n c y o f g o n o p o d i a l s w i n g s , t h r u s t s , sigmoid displays  (Table XVI).  ( T h e r e was a s i g n i f i c a n t  c o r r e l a t i o n between male s i z e and t h e f r e q u e n c y o f p e r f o r m e d by P a r i a males i n b o t h s t r e a m c o n d i t i o n s , t h i s was n o t f o u n d i n t h e o t h e r p o p u l a t i o n s . )  thrusts however,  A lack  s i g n i f i c a n t c o r r e l a t i o n s b e t w e e n m a l e s i z e and m a l e behaviour patterns i s consistent Experiment I .  with  of courtship  the r e s u l t s obtained i n  The s i z e o f i n d i v i d u a l m a l e s d o e s n o t a p p e a r t o  h a v e a b e a r i n g on t h e i r Correlations  or  courtship]>activity.  between C o u r t s h i p B e h a v i o u r P a t t e r n s  Experiment I To e x a m i n e w h e t h e r t h e r e i s a r e l a t i o n s h i p b e t w e e n v a r i o u s courtship  b e h a v i o u r p a t t e r n s p e r f o r m e d by males I l o o k e d f o r  c o r r e l a t i o n s between the f r e q u e n c i e s o f g o n o p o d i a l thrusts,  and s i g m o i d d i s p l a y s  T a b l e XV l i s t s the  four  swings,  p e r f o r m e d by i n d i v i d u a l m a l e s .  the c o r r e l a t i o n c o e f f i c i e n t s f o r each s t o c k a t  s t r e a m v e l o c i t i e s i n w h i c h t h e y were  tested.  T h e r e were s i g n i f i c a n t c o r r e l a t i o n s b e t w e e n t h e f r e q u e n c i e s o f g o n o p o d i a l swings and s i g m o i d d i s p l a y s i n t h e two f a s t e s t s t r e a m v e l o c i t i e s . consistently  f o r a l l three  T h e r e was a l s o  stocks  a  s i g n i f i c a n t c o r r e l a t i o n between g o n o p o d i a l  swings  104  Table XVI.  Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s between male s i z e and c o u r t s h i p b e h a v i o u r p a t t e r n s and between v a r i o u s c o u r t s h i p behaviour patterns. Experiment I I .  Stream v e l o c i t y  .00 Gonopod Swings  Sigmoid Display  .004  .525*  (m/sec)  .08 Thrusts  Gonopod Swings  Sigmoid Display  Thrusts  Caparo Male Size Thrusts Sigmoid Displays  -.025  .255  ••554  .508*  .064  .219  .513*  .318  .188  .748*  Paria Male Size  .050  Thrusts Sigmoid Displays  -.461  .006  • 398*  •.442  .096 .152  -.335  .433* .396*  103  •596t  Guayamare Male Size  .•459*  Thrusts  -.002  Sigmoid Displays  -.069  Upper  -.314  ••396  .315  .257 -.034  • .010 .365  . 106  .021  .000  .626*.  Aripo  Male Size  .319  .340  Thrusts  .006  Sigmoid Displays  .277  .180  •.223  .1188  ••398  .026  • 093  Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s , One-tailed test f o r positive correlations. *P < . 0 5 , £p < .01  105 and  t h r u s t s performed I t appears  and  by P a r i a  males.  t h a t the r e l a t i o n s h i p between g o n o p o d i a l  s i g m o i d d i s p l a y s i s a f f e c t e d by stream v e l o c i t y .  t h e c o r r e l a t i o n s were n o t s i g n i f i c a n t i n t h e s l o w e r velocities  ( t h e y were n e a r l y s i g n i f i c a n t a t 0.07  g e n e r a l l y became h i g h e r a s s t r e a m v e l o c i t y significant  i n the f a s t e r  I believe  Although stream  m/sec),  they  i n c r e a s e d and  were  velocities.  t h a t these changes i n the c o r r e l a t i o n s between  g o n o p o d i a l swings  and  sigmoid displays i n d i f f e r e n t  v e l o c i t i e s help to c l a r i f y swings.  swings  t h e unknown f u n c t i o n o f  stream gonopodial  I s p e c u l a t e t h a t g o n o p o d i a l s w i n g i n g has a d u a l  f u n c t i o n and  t h a t each  e x t e n t depending  of these f u n c t i o n s i s seen t o a g r e a t e r  on t h e f i s h ' s e n v i r o n m e n t .  In  faster-flowing  water, males t h a t d i s p l a y f r e q u e n t l y a l s o gonopodial f r e q u e n t l y and  those t h a t d i s p l a y i n f r e q u e n t l y  gonopodial swing.  swing  rarely  These r e s u l t s s u p p o r t the v i e w  that  g o n o p o d i a l s w i n g i n g i s r e l a t e d t o s e x u a l m o t i v a t i o n , as s u g g e s t e d by C l a r k and A r o n s o n g o n o p o d i a l s w i n g i n g may  (1951)  (1966).  and L i l e y  f u n c t i o n a s a n " i n t e n t i o n movement" o r  p r e p a r a t o r y movement o c c u r r i n g b e f o r e d i s p l a y i n g . P a r i a m a l e s i t may It  is in still  apparent I found  a l s o be  water  Thus,  ( F o r the  s i m i l a r l y r e l a t e d to t h r u s t i n g . )  t h a t a second  f u n c t i o n becomes more  - t h a t of b e i n g a type of "displacement t h a t g o n o p o d i a l s w i n g i n g was  performed  activity".  during  non-  c o u r t s h i p a t a h i g h e r f r e q u e n c y when f i s h were i n s l o w - f l o w i n g water.  T h i s " o u t - o f - c o n t e x t " b e h a v i o u r may  displacement a c t i v i t y , swimming a b o u t a t a n k .  performed Males  represent a  by m a l e s when t h e y a r e s l o w l y  perhaps  have l e s s t i m e o r  energy  106 to perform and  such displacement a c t i v i t i e s  i n fast-flowing  the r e l a t i o n s h i p between g o n o p o d i a l swings  and s e x u a l  m o t i v a t i o n w o u l d become more e v i d e n t i n f a s t - f l o w i n g Admittedly these could explain  suggestions are speculative,  water.  however,  they  t h e i n t e r e s t i n g a f f e c t o f s t r e a m v e l o c i t y on t h e  c o r r e l a t i o n s between g o n o p o d i a l swings They a l s o  water  c o u l d e x p l a i n why B a l l i n  and s i g m o i d  displays.  (1973) d i d n o t f i n d  a  c o r r e l a t i o n b e t w e e n g o n o p o d i a l swings- a n d s i g m o i d d i s p l a y s he  observed  fish  only i n s t i l l  water.  I n any c a s e ,  when  stream  v e l o c i t y d o e s a p p e a r t o a f f e c t c o r r e l a t i o n s b e t w e e n t h e two behaviour  pattern.  Experiment I I In Experiment  I I , males from three o f the f o u r s t o c k s  showed a s i g n i f i c a n t c o r r e l a t i o n b e t w e e n s i g m o i d d i s p l a y s gonopodial swings still  water  i n f l o w i n g water,  (Table XVI).  of Experiment  I.  as d i d Caparo males i n  These r e s u l t s t h e r e f o r  support  those  Stream v e l o c i t y a f f e c t s the c o r r e l a t i o n s  b e t w e e n t h e s e two b e h a v i o u r p a t t e r n s a n d p e r h a p s to g o n o p o d i a l swings two  and  t h i s may be due  e x h i b i t i n g , to- a g r e a t e r . ^ a n d l e s s e r  d i f f e r e n t f u n c t i o n s i n each  stream  condition.  degree,  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0095144/manifest

Comment

Related Items