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Adaptive significance of variation in vertebral number in fishes : evidence in Gasterosteus aculeatus.. Swain, Douglas Paul 1986-12-31

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ADAPTIVE SIGNIFICANCE OF VARIATION  IN VERTEBRAL  IN F I S H E S : EVIDENCE IN G a s t e r o s t e u s Mylocheilus  aculeatus  NUMBER AND  caurinus  By DOUGLAS PAUL B.Sc.(Hons.), M.Sc,  SWAIN  The U n i v e r s i t y  The U n i v e r s i t y  A THESIS SUBMITTED  of Manitoba,  of Manitoba,  1979  IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Zoology)  We  accept to  this  thesis  the r e q u i r e d  as c o n f o r m i n g standard  THE UNIVERSITY OF BRITISH COLUMBIA November ©  1975  Douglas Paul  1986 Swain,  1986  In p r e s e n t i n g requirements  this thesis f o r an  of  British  it  freely available  in partial  advanced degree at  Columbia,  understood for  that  Library  s h a l l make  for reference  and  study.  I  for extensive copying of  h i s or  be  her  g r a n t e d by  shall  not  be  ?ooLO&V  The U n i v e r s i t y o f B r i t i s h 1956 Main Mall V a n c o u v e r , Canada V6T 1Y3  DE-6  (3/81)  of  further this  Columbia  thesis  head o f  this  my  It is thesis  a l l o w e d w i t h o u t my  permission.  Department o f  the  representatives.  copying or p u b l i c a t i o n  f i n a n c i a l gain  University  the  f o r s c h o l a r l y p u r p o s e s may by  the  the  I agree that  agree that permission department or  f u l f i l m e n t of  written  ii  Abstract Variation is  partly  tested  i n v e r t e b r a l number  genetic  experiments  p e r f o r m a n c e , and predation  in  origin.  i n young t h r e e s p i n e  predation  age  in  for evidence  of  direct  of  was  aculeatus  measurements of  by  swimming  caurinus  f r y g r o u p e d by  selection  s t i c k l e b a c k s exposed  gibbosus  was  greater  than  f o r those  (mean  at  end  of  larger  (8.9-11.2 mm)  Kennedy  Lake,  survival  of  fish  lengths,  At  low  decreased  as  given was  body  proportions  20  or  was  the  ratio  d i d not  31  TV  high  at  by  length  for vertebral  size  25C)  fish at  but  with  not  smaller  from  either  or  number  at  respectively.  to s i z e  (precaudal/caudal  (total  8.1-8.3  mm  (7.6  mm)  or  Holden  or  was  due  (abdominal/caudal large  (11.2  intermediate Among  during  higher  Selective predation  between c o v e r  or  with  advantage  TV  (8.1-8.3 mm)  14AV/17CV  for f i s h  sunfish  sticklebacks, greater  lengths  of  of  at  Lake  small  by  31  lengths  fish  i n c r e a s e d , but  treatments.  predation  (9.8-10.0 mm)  greatest  attributable  vary  TV  Holden  ratio  ratios  size.  not  Among  intermediate  prey  32  using  (13/18) r a t i o s ,  sticklebacks,  a  a  survival  13/17) or  lengths,  with  with  with  to  for  experiments),  B.C.  fish  vertebrae).  (15/  significance  C o u n t s of w i l d  vertebrae)  and  by  and  wild.  Lepomis  at  Its  adaptive  fishes,  s t i c k l e b a c k s Gasterosteus  and  experiments.  Survival  to  in  i n young peamouth c h u b M y l o c h e i l u s  were e x a m i n e d the  i s widespread  mm)  (14/18,  Kennedy  Lake  predation  also  ratios  were  favoured  f o r v e r t e b r a l number  selection  or  selection  or a b d o m i n a l / c a u d a l  ( p r e s e n c e / a b s e n c e ) or  or for  lengths),  temperature  Burst 15C  was  small  swimming p e r f o r m a n c e o f superior  lengths  ratio  with  even  larger  AV/CV. with  lengths  optimal  were  to  in  at  indicated  (31)  (14/18, lengths  Survival smallmouth TV  end  number  at  which  during  and  unrelated  except  that at  effect  water  At  fry  slightly of  and  o f AV/CV  to  AV/CV  an  0.1%  could  length  not  ratio.  particular  ratios  the  concentration  in  Holden  (14AV/17CV) and  (7.3-7.8 mm), total  of  experiments.  fry  ratio  were  count  and  Lake a  low  intermediate  (32)  at  slightly  mm).  Micropterus with  experiments),  45  predation  dolomieui TV  at  but  was  lengths  not  at  f r y were u n d e v e l o p e d ) . be  (8.3-9.0 mm).  The  predation  o f peamouth chub d u r i n g  not  among  performance  and  a high  and  swimming  stickleback  lengths  intermediate  superior  and  at  14AV/17CV a t  an  precaudal/caudal  favouring a high small  25C,  Effects  growth  lengths  (7.8-8.3  o f most  could  lengths  13/17)  f o r those  of  vertebrae  at  bass  than  of  of  (7.8-8.3 mm),  between  15C.  c o u n t s of w i l d  selection  count  larger  greatly  reflected  with  temperature.  predation  the  smaller  Vertebral  ratios  ratios  effects  probably  mortality  at  intermediate  differed  ratio  p e r f o r m a n c e was at  higher  sticklebacks  large lengths  (9.0-11.5 mm),  between  experiments  those lengths  (13/18) a t  this  Lake  a high  of AV/CV were s i m i l a r  at  attributed  total  among  of m e t h y l c e l l u l o s e a t  Differences  44  ratio  performance  solution be  or  with  intermediate  lengths  Effects  shorter on  at  a low  high  fry  (7.4-7.8 mm),  (14/18)  those  among  Holden  attributed  to  size  by  greater of  sunfish for f i s h  10.8-11.1  smaller  or with  mm  (mean  lengths  (when  Selection for vertebral selection  by  predators.  iv Selection  i n the w i l d favoured  (9.3-9.9  mm),  (9.9-10.6  mm),  (10.6-14.0  are  selection  number  of  vertebral  TV  at  number  number  at  slightly  at  are related within  on  on  gradients  f o r pleomerism  operating  significance number.  45  neither  anteroposterior  suggested  Results  and  with  44 TV  even  small  lengths  larger  lengths  larger  lengths  mm).  Effects optimal  those  f r y with  and  the  performance  in f l e x i b i l i t y . Jordan's  rule,  of e n v i r o n m e n t a l l y  and  to  induced  the  in  in  possible  variation  involve  Explanations  l a r v a e o r f r y soon a f t e r  t o the maintenance of v a r i a t i o n  populations,  may  in  terms  of  hatching. vertebral adaptive vertebral  V  Table  of Contents Page  Abstract  •  List  of T a b l e s  List  of Figures  i i v i i xi  Acknowledgements  xiv  Introduction Part  1  I. Predation experiments with  Material  threespine  s t i c k l e b a c k s ..  and Methods  5  Results Total  14 vertebrae  1. Kennedy Lake 2. H o l d e n  Lake  14 experiments  14  experiments  18  3. Summary Abdominal  24  and c a u d a l  1. H o l d e n  Lake  2. Kennedy Lake  vertebrae  27  experiments  27  experiments  36  3. Summary  41  Body p r o p o r t i o n s 1 . Holden  Lake  2. Kennedy Lake 3 . Summary Part  I I . Burst  Material  5  43 experiments  43  experiments  50  .  56  swimming p e r f o r m a n c e  and Methods  of t h r e e s p i n e  s t i c k l e b a c k s 57 57  Results  61  Abdominal  and c a u d a l  vertebrae  61  1. P e r f o r m a n c e  a t 15C  61  2.  a t 25C  68  Performance  vi Table  of c o n t e n t s  continued  ...  3. P e r f o r m a n c e a t 15C  Part  i n 0.1% m e t h y l c e l l u l o s e  Body p r o p o r t i o n s  81  Summary  83  I I I . Changes i n v e r t e b r a l c o u n t stickleback  Material  with  length  in wild  fry  84  and M e t h o d s  84  Results Part  74  87  IV. P r e d a t i o n  Material  experiments with  peamouth c h u b  and M e t h o d s  102 102  Results  108  P a r t V. Changes i n v e r t e b r a l c o u n t  with  length  in wild  peamouth c h u b Material  120  and M e t h o d s  120  Results  122  Discussion  147  Experiments with Gasterosteus  147  Experiments with M y l o c h e i l u s  154  Effect Genetic  o f v e r t e b r a l number on b u r s t control  of the r a t i o  vertebrae Variation  swimming p e r f o r m a n c e . .  156  of abdominal t o c a u d a l 164  among p o p u l a t i o n s  169  1. P l e o m e r i s m  169  2. J o r d a n ' s  rule  175  within populations  178  Variation  Developmental noise  181  Phenotypic  186  Literature  plasticity  cited  190  vii List  of T a b l e s  Table  Page  1. D e s c r i p t i o n  of  Kennedy L a k e 2. D e s c r i p t i o n Holden Lake 3. V e r t e b r a l or  1982  predation  experiments  s t i c k l e b a c k s as p r e y of  1983  predation  sticklebacks  7  experiments  to predation  8  by  sticklebacks  or  Kennedy L a k e  to predation  by  7. V e r t e b r a l predation caudal  count c l a s s e s  1982 17  exposed  sunfish  19 length  in  1983  sticklebacks  .. .  i n c o n t r o l groups of Holden  control  vertebrae  or unexposed  i n Holden  to predation  between v e r t e b r a l c o u n t c l a s s and i n Holden  of abdominal  the r a t i o  to caudal  exposed  groups  sticklebacks  Lake  to caudal  exposed  by  Lake sunfish  length  vertebrae  or unexposed  e x p e c t e d i n exposed  fish  33  i n Holden  to predation  by  Lake sunfish,  i f predation  f o r prey size  but not f o r the r a t i o  11. V e r t e b r a l  count c l a s s e s  i n c o n t r o l g r o u p s o f Kennedy  predation  is  AV/CV  e x p e r i m e n t s , b a s e d on numbers o f a b d o m i n a l  vertebrae  29  in  experiments  selective  caudal  and 28  of a b d o m i n a l  9. R e l a t i o n s h i p  22  Lake  e x p e r i m e n t s , b a s e d on numbers o f a b d o m i n a l  sticklebacks  and  Lake  in  vertebrae  8. R a t i o s  10. R a t i o  Holden  length  sticklebacks  6. R e g r e s s i o n between v e r t e b r a l number and experiments using  15  sticklebacks  c o u n t s o f H o l d e n Lake  unexposed  exposed  sunfish  4. R e g r e s s i o n s between v e r t e b r a l c o u n t and experiments using  using  as p r e y  c o u n t s o f Kennedy Lake  unexposed  5. V e r t e b r a l  using  35 Lake and 37  viii  List  of t a b l e s  12. R a t i o s  continued...  of abdominal  sticklebacks 13. R a t i o s in  to caudal  exposed  of abdominal  Kennedy L a k e  to or g r e a t e r 14. R e g r e s s i o n  vertabrae  or unexposed  i n Kennedy  to predation  to caudal vertebrae  experiments, at lengths  by  Lake sunfish  in control  groups  l e s s than or  equal  t h a n t h e mean l e n g t h  of the r a t i o  on t h e r a t i o  42  of abdominal  of p r e c a u d a l  to caudal  to caudal length  vertebrae  in control  and  e x p e r i m e n t a l groups of Holden Lake e x p e r i m e n t s 15. Body p r o p o r t i o n s unexposed 16. Change count  of Holden Lake  to predation  by  classes  to predation 17. R e g r e s s i o n  length  i n Holden Lake  ratio  ratio  o f Kennedy L a k e  on  length  by  sticklebacks  exposure  ratios in  exposed or  sunfish  55  of s t i c k l e b a c k  c o u n t c l a s s on fry within  burst  length  15C  64  20. R e g r e s s i o n s o f swimming p e r f o r m a n c e  length,  after  52  swimming p e r f o r m a n c e  ratio  vertebral  fish  19. S i g n i f i c a n c e o f e f f e c t s o f v e r t e b r a l  the  within  49  to predation  at  or 47  sticklebacks  of v e r t e b r a l count  18. Body p r o p o r t i o n s  classes  exposed  i n 1983  Kennedy L a k e  unexposed  sticklebacks  44  sunfish  in precaudal/caudal  of abdominal  within  length  f r y on  of s t i c k l e b a c k  t o c a u d a l v e r t e b r a e and classes  21. C o e f f i c i e n t s o f r e g r e s s i o n s stickleback  38  length,  at  f r y on  total  15C  66  o f swimming p e r f o r m a n c e o f within  vertebral  count c l a s s e s  67  ix  List 22.  of t a b l e s  continued...  R e g r e s s i o n s of abdominal length small  swimming p e r f o r m a n c e  to caudal  ratio  ( L R ) , and  or l a r g e  and 24.  or l e s s 31,  on VR,  LR and  in length, c o l l e c t e d 4 and  D e s c r i p t i o n of p r e d a t i o n  the  total  of  precaudal/caudal length,  within  15C  class frequencies  o r between June  the r a t i o  ( V R ) , on  length c l a s s e s at  23. V e r t e b r a l c o u n t mm  vertebrae  on  82  (%)  of s t i c k l e b a c k s  from s i t e  8.3  A between May  7  11 , 1984  experiments  94  using  peamouth chub  as p r e y  103  25. V e r t e b r a l d e v e l o p m e n t surviving  predation  and  abnormalities  o f peamouth chub  experiments  106  26. V e r t e b r a l c o u n t s o f f r y s u r v i v i n g o r n o t experimental  r e a r i n g i n two  27. Mean l e n g t h s  groups  o f peamouth chub  surviving  from experiment  f r y exposed  post2 ....  or unexposed  to  predation 28.  111  R e g r e s s i o n s between v e r t e b r a l number and mouth c h u b  f r y exposed  or unexposed  29. V e r t e b r a l c o u n t s o f peamouth c h u b  l e n g t h among  pea-  to predation  f r y exposed  or  112 unexposed  to predation  116  30. V e r t e b r a l c o u n t s o f peamouth chub to p r e d a t i o n and  at small  f r y exposed  or l a r g e l e n g t h s  or  unexposed  i n experiments  3  5  118  31. V e r t e b r a l c o u n t s o f peamouth chub Creek  109  between  2200 and  32. V e r t e b r a l c o u n t s and f r o m Hemer C r e e k  2300 h,  lengths  at d i f f e r e n t  fry collected  i n May  and  June,  from Hemer 1984  125  o f peamouth c h u b f r y c o l l e c t e d t i m e s on  t h e same n i g h t  ...  128  X  List 33.  of  tables  Percent  continued...  of  peamouth chub  f r y with developed  among t h o s e c o l l e c t e d f r o m H o l d e n L a k e a t the 34.  date  Vertebral  Vertebral  Vertebral 31  37.  or  Vertebral  c o u n t s of  peamouth chub  14 and  c o u n t s of  c o u n t s of  31,  small  counts  Growth r a t e s  Fits  small  f r y c o l l e c t e d from  Holden  1984  or  or  133  large 23  f r y in cohort  and  large  A,  in  31  136  f r y in cohort  A,  on  May  of  142  extents  species, 39.  on  June 4  varying 38.  s i z e and  132  s a m p l e s c o l l e c t e d between May 36.  the  shown  L a k e between May 35.  vertebrae,  abdominal  of  for larvae  laboratory  models  to caudal  groups with  widely  rearing mortality  reported  i n the two  i n r e p l i c a t i o n s of  f o r the  (L)  and  or  genetic  vertebrae  144 f r y of  wild  several  (W)  c o n t r o l of  149 the  to counts observed  g r o u p s o f H o l d e n Lake p r e d a t i o n  fish  experiments  ratio  of  in c o n t r o l 166  xi  List  of F i g u r e s  Figure  Page  1. A x i a l  skeleton  2. Change  of a t h r e e s p i n e  i n percent  sticklebacks  frequency  stickleback f r y  11  of v e r t e b r a l c o u n t s i n  exposed t o p r e d a t i o n  at various  mean  lengths 3. Change count  25 i n percent  frequency  during  c l a s s e s b a s e d on t h e r a t i o  vertebrae,  predation  of abdominal  i n 1983 e x p e r i m e n t s w i t h  of v e r t e b r a l to caudal  Holden Lake  stickle-  backs  30  4. Change count  i n percent  frequency  during predation  c l a s s e s b a s e d on t h e r a t i o AV/CV,  ments w i t h 5. R a t i o s  of v e r t e b r a l  i n 1982 e x p e r i -  Kennedy L a k e s t i c k l e b a c k s  of precaudal/caudal  length  39  i n v e r t e b r a l count  c l a s s e s VR o f H o l d e n L a k e s t i c k l e b a c k s e x p o s e d o r unexposed 6. R a t i o s  to predation  by s u n f i s h  of abdominal/caudal  c l a s s e s VR' o f Kennedy Lake exposed 7. B u r s t -  swimming  9.0 mm  8. B u r s t -  to predation  11.5 mm  i n v e r t e b r a l count  s t i c k l e b a c k s e x p o s e d o r un-  by s u n f i s h  53  p e r f o r m a n c e a t 15C o f s t i c k l e b a c k f r y 6.6  i n length  swimming  length  45  i n 1983 (A) a n d 1984 (B)  62  p e r f o r m a n c e a t 15C o f s t i c k l e b a c k f r y 9.0  i n length  i n 1983 ( A ) , 1984 ( B ) , a n d 1985 (C)  69  xii  List  of f i g u r e s c o n t i n u e d . . .  9. B u r s t -  swimming p e r f o r m a n c e  9.0 mm  a t 25C o f s t i c k l e b a c k  i n length  72  10. R e g r e s s i o n s o f swimming p e r f o r m a n c e stickleback  f r y with vertebral  0.82 AV/CV, a t 15C i n 1983 at  25C i n 1984  11. B u r s t mm  f r y 6.9  count  ratios  o f 0.72 o r  ( A ) , a t 15C i n 1984  ( B ) , and  (C)  75  swimming p e r f o r m a n c e  in length  on l e n g t h among  of s t i c k l e b a c k  i n an 0.1% s o l u t i o n  f r y 6.6  -  9.0  of m e t h y l c e l l u l o s e a t  1 5C 12. Map  77 of Holden  Lake,  B.C.,  13. F r e q u e n c i e s o f v e r t e b r a l back  f r y grouped  in length,  15. V e r t e b r a l at and  site  count  grouped  ratios  B, c o m p a r i n g  length class  count c l a s s e s  count c l a s s e s  stickle-  in f r y less  by c o l l e c t i o n  of s t i c k l e b a c k  counts  than  date  91  f r y i n two  in length class  'cohorts'  i on day 36  i + 1 on day 39  by l e n g t h a t s i t e  96  vertebral  counts, i n f r y  A or B  17. R e g r e s s i o n s between v e r t e b r a l and  in wild  85  88  16. P e r c e n t f r e q u e n c i e s o f t o t a l grouped  sampling s i t e s  by l e n g t h  14. F r e q u e n c i e s o f v e r t e b r a l 7.4 mm  showing  number  99 and l e n g t h  in control  e x p e r i m e n t a l g r o u p s , peamouth c h u b p r e d a t i o n  experi-  ments 3 - 5  114  18. Number o f peamouth c h u b f r y c a p t u r e d p e r 5 min S u r b e r sampler  s e t , a t 2200-2300 h i n Hemer  Creek,  1984  19. L e n g t h s o f peamouth chub f r y c a p t u r e d i n Hemer between  2200 and 2300 h  123  Creek 126  xi i i  List 20.  21.  of f i g u r e s  Length d i s t r i b u t i o n s  o f peamouth chub  frycollected  H o l d e n Lake between May  (M) 21 a n d June  Frequencies  44  of 22.  continued...  of f r y with  collections  vertebrae,  of f r y i n c o h o r t  after  on May 31 a n d t h o s e  collection  between J u n e  in length classes 137  A, among  fish  preserved  A model e x p l a i n i n g p l e o m e r i s m  24.  C o n d i t i o n s under  upon 140 170  which mixed or pure s t r a t e g i e s  when t h e r e  reared  4 and 27  23.  optimal  ( J ) 27, 1984 ... 130  between J u n e 4 and 27  V e r t e b r a l counts  collection  from  i s temporal  variation  are  in selection  .. 183  xiv  Acknowledgements It  i s a pleasure  support  of  office  and  my  W.C.  facilities.  C.  of  Dr.  facilities  Station  S o l m i e , Dr.  acknowledge  supervisor,  computing  Biological  to  at  C. were  Clarke  and  Moore and  Dr. A.  the  for  arranging  shocking  C.  device  Haegele  equipment.  Dr.  CP.  Shillington  Mallett  used  LeGuerrier  for  the  D.E.  Hay  I  thank  Pacific  Blackburn,  for providing  them  these  collection  and  Dr.  K.  i n swimming p e r f o r m a n c e e x p e r i m e n t s ,  and  Gass  Cameron  in  assistance  for  the  loan  of  (who  counted about  D.  Miller,  the  laboratory,  for  i n the  I t h a n k C.  A.  for  Neaves  for assistance  by  Laboratory,  Pronk a s s i s t e d i n t h e  Archibald,  P.  Lindsey.  generous  Armstrong  for assistance and  C.  and  I thank J .  assistance.  L.  I thank E.  vertebrae),  McKinnell  and  this  advice  provided  Nanaimo, B.C.  s t i c k l e b a c k s f r o m Kennedy L a k e ;  Hyatt  the  assistance  shop, and in  the  C.  wild.  G.  on  500,000  chub  M a l l e t t , and  K.  M.  S.  the  J.  photographic  Hamer, computer,  Foote  Above a l l ,  and  I thank  R. R. my  wife  Elizabeth Mallett  f o r her  understanding  and  support  during  the  course  study.  F i n a n c i a l support  from the  Natural  Sciences C.C. Trust  and  of  this  Engineering  Lindsey  and  a  in a predoctoral  Research Council  of  Canada,  s c h o l a r s h i p t o m y s e l f , and fellowship  is gratefully  in grants  from  the  to  Killam  acknowledged.  1  Introduction  The central this  adaptive  significance  problem  in  p r o b l e m has  amounts  of  two  been  Hubby  expected ways.  because  stimulated  I t may no  1966).  by  variation  evolutionary  allozyme v a r i a t i o n  L e w o n t i n and been  of  largely  This  forces  act  on  it.  p o l y m o r p h i s m may  had  supposed.  This  selection  work  the  i n space or  populations 1963;  on  (Levene  Bryant  time can  Dempster  Hedrick  et  be  of  vast  had  has  genetic  in  simply  mechanisms  widespread  which  led  than  to  much  diversifying  variation  Haldane  a l . 1976;  1966;  than  persists  more  1955;  in  interpreted  selective  under  maintain  interest  greater  possibility  conditions  1953;  1976;  latter  be  a  (e.g., H a r r i s  and  Or,  is  discovery  can  neutral,  maintaining  theoretical  the  geneticists,  c a p a b l e of been  by  species  Present  variability,  selectively  selective  biology.  in populations  population be  within  and  Spieth  within Jayaker  1979;  Ewing  1979).  An  analogous  and  older  maintenance  of  populations.  T h i s problem  such  variation  genetic on  The received  morphological  may  variation,  genetically  or  may  mechanisms  result  conspicuously  of  body  armature  by  the  variation  possibility  induced  indirect  the  rather  selection  in that than  acting  traits.  i n the  variable  from  regarding  behavioural  environmentally  maintaining  much a t t e n t i o n  and  exists  i s complicated  reflect  correlated  are  problem  for  (number o f  morphological  gasterosteid characters lateral  variation  have  fishes.  These  fishes  r e l a t i n g to  the  extent  plates,  number and  size  of  2 dorsal as  an  and  pelvic  important  (McPhail  1969;  Hagen and  variety Reimchen  (e.g.,  1983;  has  u s u a l l y been  the  predators  1980,  1983).  Moodie  but et  in  character variety  rather al.  Bell  and  a  direct  functional  states  in  Hagen  avoiding  circumstances  not  Reist  Haglund  and  that be  the  the  1980a,b;  a  (e.g.,  character  extent  some c o r r e l a t e d b e h a v i o u r a l  1973;  1972;  Blouw  of  s i g n i f i c a n c e may  characters  Moodie  1976;  1980a,b;  implicated  these  1973;  emphasized  a  on  O t h e r s have s u g g e s t e d  selective  itself,  have  various  1972,  Reimchen  Reist  workers  of  direct  armature  of  Gilbertson  M o o d i e and  1980,  Some  significance  of  1973;  Reimchen  I984a,b).  Predation  factor in selection operating  Moodie et a l . 1978;  spines).  of  body  character  Blouw and  Hagen  1984a). Variation and  among  i n the fish  number of v e r t e b r a e populations.  environmental  in origin  and  I 9 8 6 a , b ) , but  Lindsey  1962;  Ali  and  Lindsey  'neutralist'  v i e w has  within  limits,  narrow  selective vertebral  count  strong  selective  the than  argued  to  has  (Fowler to  and  due  et  1970).  i t may  (Lindsey  1985a).  count  is  The  without  malleability influences  consistent with counts. be  Swain  p e r s i s t s because,  Wide  environmental  partly  1981;  al.  vertebral  within  is  component  such v a r i a t i o n  to p a r t i c u l a r  vary  Arnason  a genetic  been c o n s i d e r e d  limits,  widespread  variation  Leary  precise  advantage  vertebrae  f i x the  1974;  the  that, within  number of  a l s o has  in response  development  This  Lindsey  been t h a t  significance  early  has  (e.g.,  is  a  Fowler  of  during lack  of  (1970)  more a d a p t i v e  to ' l e t '  t o random e n v i r o n m e n t a l  changes,  number g e n e t i c a l l y , s i n c e t o do  so w o u l d  limit  a  3 fish's  ability  to respond  environmental selective A  contrasting  widespread  tendency  number  be  (pleomerism) rule)  for  not  with  perhaps  involving  1928).  optimum number flexibility,  number  number  number  Jordan's  rule  of  depend on w a t e r  thesis,  is  maximum  with  locomotory  when  lengths  mortality  ability  (to  the  vertebral  body waters  length (Jordan's  t h e s e t r e n d s might  number  per se, but r a t h e r  a  rate,  may  advantage,  be a s s o c i a t e d  1975).  This  which  i n embryos  functional  suggests that  with  might  some  involve  depend  the on  body a  that  is  size  number  high  and  selective  numbers o f v e r t e b r a e ,  d e p e n d s on w a t e r  population,  escape  s i z e , and given  some  v a r i e s w i t h body s i z e ,  a  functionally  or v i s c o s i t y .  vertebral  in  by  that  particular  a given size  I assume t h a t  body  lengths,  at  or c o l d e r  the hypotheses  t h e number a t a d v a n t a g e number  maximum  o f v e r t e b r a e formed  might  temperature  associated  f o r higher  t h e optimum number a t  I test  or  o r some o t h e r f e a t u r e o f t h e a x i a l  segments  suggests that  supported  developmental  locomotory a b i l i t y ,  I f so, pleomerism  optimum  viscosity.  or  Alternatively,  myomere  In t h i s  size  of v e r t e b r a e (Lindsey  segmentation.  optimum  longer  for vertebral  the  mutation  p r o c e s s e s of g r e a t e r  is  forms  I t has been a r g u e d  influence  1926,  advantage  view  related  such as egg  (Hubbs  that  among  by  1963).  'selectionist'  1975).  characters  might  exerted  and w i t h h i g h e r l a t i t u d e  selection,  incidently  (Bateson  associated  (Lindsey  reflect  stresses  change on o t h e r d e v e l o p m e n t a l  significance  to  to  and t h a t  temperature or  i s adapted  not t o  but r a t h e r selection  the  to the f r y  related  predators) i s l i k e l y  the  to  t o be most  4 stringent.  These hypotheses  threespine  stickleback  in  are  to those  compared  evidence of  of  selection  hypothesis  that  number, by  direct  aculeatus  related  within  and  significance  of  i n the  s i z e s and  of  (Richardson),  viscosities.  I  ages.  burst sizes  of  environmental  and  also  In a d d i t i o n , I  Finally,  populations,  the and  predation predation look  for  comparing v e r t e b r a l counts  depends  swimming and  to  the  i n f l u e n c e s on  on  test  the  vertebral  performance  at  results  to the maintenance of v a r i a t i o n among  using  s u r v i v o r s of  performance  various  species,  aculeatus • (Linnaeus)  w i l d , by  measurements of fry  two  unexposed c o n t r o l s .  locomotory  t e m p e r a t u r e s and are  caurinus  in  w h i c h v e r t e b r a l c o u n t s of  w i l d f r y of v a r i o u s  G.  tested  Gasterosteus  peamouth c h u b M y l o c h e i l u s experiments  are  of  of  various  water  these  tests  i n v e r t e b r a l number possible  adaptive  v e r t e b r a l number.  5  Part  I.  Predation  experiments with threespine  Material  and M e t h o d s  Breeding  sticklebacks  Holden  Lakes  on  Vancouver  oligotrophic  lake  (Hagen  Gilbertson  small  and  eutrophic  i n the laboratory of  and  30/L  Artemia  about  nauplii  of  Kennedy  Lake  fish,  designated control  green  cm)  a t about  Fry  17C.  were  Holden  Fry  fed  as c o n t r o l  of  K1, f r y were  were  alternately  among  had  itsfull three  d  after  maintained  the  a  natural  Each  held  at  hatching plankton,  in  single  1982  water  hatching.  Two  among  first  distributed  three  i n small  illuminated  a t 20C. lots  17  in lots  t a n k s t o be h e l d  t a n k s t o be h e l d  were  either  tanks  and  20C. 10-30  a t 15C u n t i l then  were One the In fish each  alternately  I n e x p e r i m e n t s K2 a n d  alternately  by o v e r h e a d  15C;  or of  six  dimensions  as e x p e r i m e n t a l tanks.  at  using  c o l l e c t i o n of  approximate  complement o f f i s h ,  K3, f r y were d i s t r i b u t e d Tanks  isa  offspring  were  and d i s t r i b u t e d  t a n k s and f o u r  experiment  the  morphs  morph.  a n d two e x p e r i m e n t a l t a n k s were m a i n t a i n e d a t  received  large  Lake  few d a y s a f t e r  conducted  offspring  fiberglass,  15-20  tanks  tanks.  is a  plate  t h e low p l a t e d  experiments  the  remaining  among  only  100/L f o r t h e f i r s t  three  (of  110 x 50 x 34  lateral  aculeatus;  ( a b o u t 50 c r o s s e s ) were m i x e d tanks  Lake  or  and nematodes.  each  190-L  Kennedy  Kennedy  t o two f e m a l e s , a n d t h e i r  thereafter.  For  parents  1972) o f G.  crossed  from e i t h e r  a l l three  lake containing  densities about  Island.  containing  male was a r t i f i c i a l l y were r e a r e d  were c o l l e c t e d  sticklebacks  among a l l s i x  fluorescent  l i g h t s on  6 a p h o t o p e r i o d of 1-2L/min plastic  in  16.5  each  suspended  removed  while  not  replaced  the  desired  near  number.  initial  number had  sunfish  mm  in  h  before  are given in Table  Three c o l l e c t i o n s (80-110 at  at  each  e v e r y day. entire At  the  anaesthetic with a l c i a n  10-50  each),  15-30  and  except that  Lake,  mm).  approached  of  pumpkinseed the  every  2-5  more t h a n  1 d.  and  averaged  sunfish.  24  Further  (1) t e m p e r a t u r e s  and  one  each  experiment,  fry  and  in  glycerine  ( f o l l o w i n g D i n g e r k u s and U h l e r  mg  of a l c i a n  b l u e p e r ml  0.5%  in two  resembled  those  were e i t h e r  15 o r  o f t h e two  are given in Table  stain  in  experimental  (3) s u n f i s h were r e p l a c e d  with trypsin  of  Lake  of each used  p r o v i d e d i t remained  Details  cleared  fry in  F r y were f e d e a c h  (MS222), p r e s e r v e d i n 10% b u f f e r e d blue,  usually  50-60 % o f  lasting  Experiments  provided in only  of  10-30  until  offspring  sizes.  When c o v e r was  end  eaten  by  h  introduction  temperature,  experiment.  was  was  1.  different  i n 1982  but  o f p a r e n t s were made f r o m H o l d e n  crosses  (2) c o v e r was  tanks  the  and  was  shredded  15 h o f a c c l i m a t i o n ,  from Holden  (range  details  tanks,  S u n f i s h were r e p l a c e d  u s e d were c o l l e c t e d  1-2  25 C,  for  flow  p r o v i d e d by  to predation  been e a t e n .  length  Water  fry  overnight i n experiments  standard  conducted  usually  about  gibbosus)  removed  experiments  dark.  the e x t e n t of p r e d a t i o n  After  morning  1983  was  h  of e x p e r i m e n t a l  t a n k s were e x p o s e d  (Lepomis  The  Cover  e a c h end  assessing  sunfish  and  tank.  7.5  when t h e e s t i m a t e d number o f  experimental  h,  h light:  in place  for  only the  2. were  killed  formalin, KOH,  and  stained stored  (1977), except that  solution  were  used  in  2  here).  T a b l e 1. D e s c r i p t i o n of 1982 p r e d a t i o n experiments u s i n g Kennedy Lake s t i c k l e b a c k s as prey. Percent cover i s percent of predator-hours (pred.-h) with cover. Pred.-h = no. predators x h present. Duration i n h i n c l u d e s night p e r i o d s without p r e d a t o r s . Predators are s u n f i s h c o l l e c t e d from Holden Lake.  Temp. ( C)  h  Pred.-h  0 0  12 22  0 0  0 0  15 15 20 20  88 64 57 61  12 12 22 22  60 107 104 135  62 55 61 64  Control  15 20  0 0  28 11  0 0  Exptl.  15 15 20 20  55 48 88 74  29 30 10 11  Control  15 17  0 0  Exptl.  15 15 17 17  96 0 100 0  Treatment  K1  Control  15 20  Exptl.  K2  K3  Duration  % eaten  Exp.  % Cover  No. eaten per pred.. -h 0..0 0 .0  No. surv1v1ng  standard length of s u r v i v o r s (mm) Mean  SD  87 89  8 .07 8 .55  0.52 0.72  3.. 1 1 .5 , 1. 8 1 .5 .  106 127 123 107  8 .23 8 .26 8 . 52 8 .74  0.51 0.59 0.61 0.54  0 0  0 .0 0 .0  126 117  8 . 14 8 .23  0.72 0.66  91 104 56 67  58 60 51 51  2..2 1 .9 . 3..0 2. 6  144 132 165 167  8 .50 8 .48 8 .43 8..58  0.64 0.69 0.68 0.75  50 35  0 0  0 0  0 .0 0.,0  132 152  8 .91 8 .93  0.82 0.84  50 52 35 51  303 329 262 373  58 63 53 59  0 .75 0..75 0..80 0 .59  162 147 187 157  9 . 17 9 . 10 9 .03 9 . 10  0.54 0.55 0.64 0.50  Table 2. D e s c r i p t i o n of 1983 p r e d a t i o n experiments u s i n g Holden Lake s t i c k l e b a c k s as prey. Cover 1s present (Y) or absent (N) d u r i n g a l l predator-hours (pred.-h). Duration 1n h i n c l u d e s night p e r i o d s without p r e d a t o r s . Predators a r e s u n f i s h c o l l e c t e d from Holden Lake. Prey In experiments with the same parent code a r e o f f s p r i n g of the same c o l l e c t i o n of p a r e n t s .  Duration Exp.  Parents Treatment  H1  H2  H3  A  B  C  Temp. ( C) Cover  h  Pred.-h  Control  15 25  N N  46 23  0 0  Exptl.  15 15 25 25  Y N Y N  52 46 22 22  298 298 119 122  Control  15 25  N N  52 33  0 0  Exptl.  15 15 25 25  Y N Y N  54 50 29 32  496 419 165 195  Control  15 25  N N  25 13  0 0  Exptl.  15 15 25 25  Y N Y N  26 24 12 12  136 92 97 109  standard length of predators (mm) Mean  SD  %  eaten  No. eaten per pred.-h  0 0 23 . 13 23..47 23., 15 23..60  0,.74 1 ., 19 1 .00 . 0,.81  55 63 55 59  0,,55 0,,63 1.39 1 ,44 .  0 0 24,.30 24,.28 24,. 10 24.. 10  0,.76 0,.79 0..74 0.,74  56 62 58 64  0. 34 0.,45 1.05 0. 98  0 0 28,.07 27 ,,93 28..00 28 .OO  0..80 0..80 0. 82 0..82  62 58 65 70  1 ,36 . 1 .90 2 .03 . 1 .94 .  standard length of s u r v i v o r s (mm) No. surviving  Mean  SD  119 121  7.62 7.63  0.53 0.57  135 112 133 124  7.97 7.98 7.83 7.78  0.52 0.54 0.54 0.49  124 125  8. 27 8. 35  0.49 0.48  132 1 13 127 108  8. 65 8. 79 8. 56 8. 69  0.55 0.54 0.52 0.53  124 125  8 .56 8 .50  0.51 0.63  1 15 126 104 89  8 .90 8 .92 8 .97 8 .97  0.56 0.60 0.52 0.50  contd.  Table 2. contd.  Exp. H4  H5  H6  Parents Treatment C  A  B  Temp. ( C) Cover  Duration h  Pred.-h  Control  15 25  N N  32 30  0 0  Exptl.  15 15 25 25  Y N Y N  32 31 31 30  246 238 171 156  Control  15 25  N N  71 56  0 0  Exptl.  15 15 25 25  Y N Y N  78 60 56 36  742 612 254 198  Control  15 25  N N  56 50  0 0  Exptl.  15 15 25 25  Y N Y N  58 56 51 48  608 507 246 226  standard length of predators (mm) Mean  SD  '% . eaten  No. eaten per pred.-h  0 0 29 29 29 29  .50 .50 .50 .50  1 .03 1 .03 1 .08 1 .08  57 57 60 58  0 .69 0 .71 1 .04 , 1. 1 1  0 0 29 .75 29 .50 28 .50 28 .90  1 .87 1 .89 1 .84 1 .85  56 58 59 57  0.,22 0..28 0.,69 0.,87  0 0 32,.94 32,.97 32 .75 32.,80  1 .05 1 .03 1 .07 1 . 15  63 57 59 58  0.,31 0.,34 0. 65 0. 70  No. surviving  standard length o f s u r v i v o r s (mm) '  Mean  SD  124 123  9 .83 9,.76  0.,63 0.,63  128 128 121 125  10,.26 10,.31 10,.03 10,.22  0.,53 0..61 O..63 0.,66  120 1 19  9,.89 0. 62 10.. 12 0. 66  133 126 124 128  10.,21 10,.05 10.,05 9..66  125 1 13  1 1. .13 0. 72 11 . , 19 0. 80  1 10 130 113 1 16  11 . ,47 1 1,67 . 1 1,54 . 1 1,66 .  0. 64 0. 62 0. 65 0. 57  0. 78 0. 80 0. 76 0. 72  10 Counts  were  centrum  frequently  complex  vertebrae  as  of  centra,  bore  two  over  80% o f f i s h  occurred first first  caudal  whose  those  fish  spine  normally  spine  1983  (Holden Lake) experiments,  least the the  1.5  or  more  vertebra  maximum s p i n e designated  differed  i n the  the f i r s t the  between  method d e s i g n a t e d  spine  caudal  methods  first  anal  basal.  gradually  near In the  bearing  a  i n the v i c i n i t y caudal  of  vertebra.  in  1986),  In the  l e n g t h was 80% o r more o f t h e  of only  one fewer c a u d a l  The  vertebra  were u s e d .  (recounted  of  vertebra.  in  length  as i t s centrum, or a t  the f i r s t  vicinity  designation  length.  1).  vertebra  haemal s p i n e  whose haemal s p i n e  length  b o t h methods,  increased  first  experiments  designated  (Fig.  the  times as long  was d e s i g n a t e d  1982 (Kennedy L a k e )  first  was  length  the  as the l o n g e s t  basals,  were  was d e s i g n a t e d t h e  basal, the f o l l o w i n g c r i t e r i a  85% a s l o n g anal  basal  last Such  i n haemal s p i n e  anal  this  The  arches.  projected p o s t e r i o r to the f i r s t  first  spine  Vertebrae  l o n g haemal s p i n e  the  haemal  haemal  on t h e b a s i s o f haemal  a  whose haemal  anal  or  of the f i r s t  bearing  vertebra;  haemal  neural  the u r o s t y l e .  a sharp d i s c o n t i n u i t y  i n the v i c i n i t y  vertebra  excluding  were c o u n t e d a s o n e .  'abdominal' or 'caudal'  In  In  made  the  anal  Of 332 f i s h  the  first  5 fish;  vertebrae,  basals counted  was using  caudal  vertebra  in 3 fish  the f i r s t  and i n 2  fish  one  more.  Total end  of  vertebral first  length  the  was measured  hypural  plate.  from t h e t i p o f t h e s n o u t I n Kennedy L a k e  c o l u m n was a l s o m e a s u r e d ,  vertebra  to  fish,  length  to the of the  f r o m t h e a n t e r i o r edge o f t h e  t h e p o s t e r i o r edge o f t h e h y p u r a l  plate.  In  Figure  1. A x i a l  skeleton. vertebrae  s k e l e t o n of t h r e e s p i n e  B-D.  Division  marked by a r r o w  rare d i v i s i o n ) .  Scale  8.1  i s caudal  (C,D) mm.  CL  s t i c k l e b a c k f r y . A.  between a b d o m i n a l and  caudal  (B. most common d i v i s i o n ,  1 mm.  Fish length.  lengths  8.0  Entire  D.  (A,B) o r  most  1 3 fish  from  anterior  both  in this  caudal  excluded  vertebrae in  some  from t h i s  in  calculated vertebra  instances,  fish  or  Independence  of  caudal  Rohlf  using  count  with  sample this  the  vertebrae  those  abdominal  In  sizes  calculated  Linear  of  Analyses  was  of  a  Adjusted fish, lengths  above.  treatment  was  BMDP4F  (Dixon  using used  in  200 o r l e s s .  a l l 2x2  Probabilities  may be c o n s e r v a t i v e  (Sokal  and  r e g r e s s i o n s were c a l c u l a t e d a n d BMDP1V,  of v a r i a n c e and c o v a r i a n c e  BMDP7D, BMDP1V o r BMDP2V.  l e n g t h was  Lake  described  and  these  length  Kennedy  was  vertebra  made when c a u d a l  criteria  for continuity  correction  1981).  in  above.  vertebra  i n question.  o f s l o p e s t e s t e d u s i n g BMDP1R a n d  1981).  described  average  distribution  tests  correction  1981; D i x o n  equality (Dixon  of  chi-square  using  designated  respectively).  calculated  were m e a s u r e d d i d n o t employ  calculated  t o those  the l a s t  to  1 ) . The v e r t e b r a e  caudal  length of the f i s h  the  comparisons  (Fig.  first  1D,  subtracting  since  Yates'  the  1C a n d  l e n g t h s c o u l d n o t be counts  the  basal,  f r o m H o l d e n L a k e , an a d j u s t e d c a u d a l  by a d d i n g  by  from  anal  to the c r i t e r i a  l e n g t h , or r a r e l y ,  i n the caudal  assessed  plate  corresponded  according  caudal  1981).  measured  v e r t e b r a whose haemal s p i n e o p p o s e d o r  length normally  included i n i t (Fig.  cases,  was  p o s t e r i o r to the midline of the f i r s t  However,  was  length  p o s t e r i o r edge o f t h e h y p u r a l  included as  caudal  edge o f t h e f i r s t  projected the  lakes,  respectively were  performed  14 Results Total 1.  Vertebrae  Kennedy L a k e  Vertebral among  tanks  count  distributions  b e f o r e exposure  two e x p e r i m e n t s , virtually  experiments  distributions significant  in  (Table 3).  i n the  third  apparently  to predators.  distributions  identical  were  the  two  (p=0.14, w i t h d a t a  In each  of the  first  control  tanks  were  Differences  experiment grouped  homogeneous  between t h e c o n t r o l  were  not  as f i s h  statistically  with or without  31  vertebrae). The  first  selective  two  predation  The  frequency  in  experimental  difference  of f i s h  experiments  the d i f f e r e n c e survival  times  that  experiments,  The average control were  of  31 v e r t e b r a e was c o n s i s t e n t l y  in  control  significant  tanks a f t e r  (p=0.00l4,  distributions  are  between c o n t r o l  of f i s h  with  with  (Table 3). greater  predation.  grouping  This  over  homogeneous  both  between  Judging  and e x p e r i m e n t a l  31 v e r t e b r a e was a b o u t  32 v e r t e b r a e i n t h e f i r s t  of  from  groups,  1.7 and and  1.3  second  respectively.  third  experiment  prey  size.  differed  Judging  and e x p e r i m e n t a l groups,  about  number  p r e d a t i o n t r e a t m e n t s , p>0.20).  fish  evidence  with  i n counts  rate  striking  respect to vertebral  count within  provided  with  than  i s highly  experiments;  the  experiments  8.5-10.5  mm  from  from the  the size  previous  two  in  d i s t r i b u t i o n s of  the m a j o r i t y of the  fish  eaten  l o n g , whereas most o f t h o s e e a t e n  i n the  Table 3. Vertebral counts of Kennedy Lake sticklebacks exposed (experimental) or unexposed (control) to predation by sunfish. Probabilities are from chi-square tests of independence between vertebral count and predation treatment, with f i s h grouped as those with or without 31 vertebrae.  Exp.  Treatment  K1  Control  Exptl.  K2  Control  Exptl.  K3  Control  Exptl .  Temp. ( C)  Mean length (mm)  15 20  8.,07 8 .55  15 15 20 20  15 20  15 15 20 20  15 17  15 15 17 17  8 ,23 8..26 8..52 8..74  8.. 14 8..23  8 .50 8..48 8 .43 8 .58  8 .91 8 .93  9 . 17 9 . 10 9 .03 9 . 10  No. surviving  Vertebral count (%) 29  87 89  30  31  32  33  1 ,. 1 41 .4 40,.4  56. 3 59. 6  1 .1  176  0.6  58.,0  0.6  106 127 123 107  55,.7 52 .8 1 ., 6 52,,8 0.,9 54..2  40. 6 44.,9 44., 7 43.,9  1 .9 . 2.4 0.8 0..9  463  1 .. 1 53,.8 43.,6  1 .. 5  126 1 17  6,.3 47..6 45,.2 5,. 1 46..2 47 , .0  0.8 1 ,. 7  243  5,.8 46,.9  46.. 1 '1 . 2  144 132 165 167  0.8  6,.9 8 .3 3,.0 6 .0  59,.0 49 .2 52,.7 52 .7  33 .3 39..4 43,.0 40..7  0.,7 2.3 1 .. 2 0..6  608  0.2  5 .9  53 .5. 39,.3  2 1.  132 152  4,.5 48,.5 47 , .0 4..6 57,.2 36 . .8  1. 3  284  4,.6 53 .2 41 .5  0..7  162 147 187 157  4,.3 4,,8 2. 1 1.9 ,  60,.5 54,.4 57,.2 56,. 1  34, 6 39..5 40,. 1 38..9  0.6 1 .. 4 0..5 3..2  653  3.2  57.1  38.3  1.4  40,.9  1,9 .  Probability  0.004  0.085  0.26  16 first  two e x p e r i m e n t s were a b o u t  these  longer  fish  number;  the  slightly  greater  average  was n o t s i g n i f i c a n t l y  frequency  Predation  was a l s o  was u s u a l l y s l i g h t l y  Vertebral in  in  of  rather  than  (Table  4).  vertebrae  respect  that  Moreover, size  to prey  of  fish  control  this  only  size.  The  groups  unexposed  groups  of  to  (Table  3).  c o r r e l a t e d among  fish  correlation  selective  selectivity  number c a n n o t  was  i n experimental  predation  was  predation  have been due t o s i z e  i n any in  the  to counteract  to the observed d i f f e r e n c e s  Therefore,  on  for vertebral  r e l a t i o n s h i p was n o t s i g n i f i c a n t  t h a t would cause  numbers.  Predation  i n c o n t r o l groups.  with  corresponding  than c o n t r i b u t e  vertebral  31  number and l e n g t h were p o s i t i v e l y  group  direction  than  long.  selective  surviving predation  greater  the  with  selective  a l l groups, but t h i s  control  fish  i n experimental  l e n g t h of f i s h  predation  7.0-8.5 mm  in  vertebral  with  respect  selection in  to  these  experiments.  Although between  vertebral  experimental increase  in  groups c o u l d vertebrae predators sample  significant  groups  number  result  in this in  at  and  in  sizes  experiment, or experimental  experimental  experiments  (Table 4 ) .  and  in  simply  groups.  control  favour  within  may  the  was  experimental  between v e r t e b r a l number and l e n g t h between  (K2  from s e l e c t i o n i n smaller  group,  length  i n one e x p e r i m e n t  significance  only  size  i n no c o n t r o l  significant Table  4).  relative of  in This  to control  fish  with  31  t h e range exposed t o reflect  Slopes  of  d i d not d i f f e r groups  correlation  in  increased regressions  significantly  any o f t h e t h r e e  Table 4. Regressions between vertebral count and length In 1982 experiments using offspring of Kennedy Lake sticklebacks. Data are grouped over replications within predation treatments since slopes are equal among replications (p>0.35). Probabi11ty of equal slopes between treatments  Treatment  No.  Slope  Probabi11ty of zero slope  K1  Control Exptl.  176 463  0.091 0.012  0.12 0.78  0.28  K2  Control Exptl.  243 608  0.031 0.099  0.59 0.006  0.31  K3  Control Exptl.  284 653  0.056 0.032  0.22 0.43  0.69  Exp.  18 No  significant  selective in  temperatures  groups  in  at  were  higher  at  temperatures.  the higher  2.  Holden  Selective  among  survival  8.5  mm  vertebrae  for  prey  control  groups  extent  of  was  than  to  both  homogeneous  6).  larger  fish,  Since this  of  between 0.49,  Holden  8.1-8.2  fish  temperature  survival  correlation  since  the  for  (Table 5 ) .  frequency  Vertebral  experiments  in  H2  during was a g a i n  and  and H3  predation in  of cover  the  length  control was  in  was  respect to prey  number  in  (p=0.82)).  and t o t h e a v a i l a b i l i t y with  fish  significant  between e x p e r i m e n t s these  (i.e.,  vertebrae  g r o u p s was h i g h l y  selective  among f i s h  31  fish  H2 a n d H 3 ) ,  greater  with  in  Lake  mm  with other counts  predation  experiments.  (Table  experimental  u s i n g Kennedy L a k e  about  experiments  P r e d a t i o n was a l s o  correlated  of  control  (p>0.65).  positively  of  f o r those  both  these  fish  i n l e n g t h i n experiments  unrelated  in  K2 and K3,  percent m o r t a l i t y  t o p r e d a t i o n was a g a i n  selective to  two  (p=0.16 and  number  t h a t seen  lengths  or l e s s  compared  (p=0.0025, c o m b i n i n g  the  differences  t h e lower  vertebral  increase i n the frequency  experimental  at  in  significant  of  experiments  d u r i n g exposure  31  but  extent  of s u r v i v o r s  identical  frequent  reflect  i n 1983 r e s e m b l e d  At average  fish  with  Lake  simply  predation  sticklebacks 1982.  more  were n o t s t a t i s t i c a l l y a n d may  the  In experiments  temperature,  respectively),  The  K1.  on  V e r t e b r a l counts  virtually  experiment  the  temperatures  This  temperature  32 v e r t e b r a e were s l i g h t l y  groups  in  of  p r e d a t i o n was d e t e c t e d .  experimental  with  effect  size were  groups  greater for  direction  that  Table 5. Vertebral counts of Holden Lake sticklebacks exposed (experimental) or unexposed (control) to predation by sunfish. Probabilities are from chi-square tests of independence between count and predation treatment, with f i s h grouped as those with or without the favoured count (31 In experiments at sizes under 8.5 or over 11.0 mm; 32 in experiments at other sizes). Results of experiments H2 and H3 are shown separately for f i s h 8.5 mm or less in length, or over 8.5 mm In length.  Exp.  Treatment  H1  Control  Exptl.  H2  Temp. ( C) Cover 15 25  15 15 25 25  .5 mm or less Control 15 25  N N  Y N Y N  N  N  Mean 1ength (mm)  No. surviving  7.62 7.63  119 121  7.,97 7..98 7.83 7.,78  8.,02 8.. 10  32  533  10., 1 58. 8 12.,4 63. 6  29. 4 22. 3  1 ,. 7 17 .  240  11. 2  61 .3  25. 8  1 .7  135 112 133 124  13. 4 11 . ,6 9.0 10.,5  60. 7 25. 9 68. 8 18. 8 66. 2 24. 8 63.,7 25. 0  0.9 0.8  504  , 1 64.,7 23. 8 11 .  0.,4  H3  15 15 25 25  .5 mm or less Control 15 25  Y N Y N  N N  8.. 8. 8.. 8..  18 15 13 15  8 . 15 8 .09  15 15 25 25  Y N Y N  8 .20 8 . 14 8 . 19 8 .29  31  3 .4 1. ,2  5..2 56..4 36..0  2,.3  62 36 63 44  6 .5 2 .8 4,.8 4,.5  69..4 66,.7 65.. 1 72,.7  24.,2 30,.6 30,.2 20,.5  2 .3  205  4,.9  68 .3  26 .3  0 .5  62 75 137  Exptl.  <30  28.,7 43..5  87 85 172  Exptl .  Vertebral count (%)  29 34 21 21 105  8 .0 59. 8 2..4 52..9  Probabi1ity  0.36  0.017  14.5 71 .0 14 .5 26 .7 46 .7 26 .7 57 .7  21 .2  17.2 69 .0 8 .8 70 .6 14.3 71 .4 23 .8 66 .7  13 .8 20 .6 14.3 9 .5  15.3  15.2  21 .2  69.5  0.058  contd.  Table 5. contd.  Exp. H2  Treatment over 8.5 mm Control  Exptl.  H3  over 8.5 mm Control  Temp. ( C) Cover 15 25  15 15 25 25  15 25  N N  Y N Y N  N N  Mean length (mm)  No. surviving  8 .85 8..88  37 40  7 .5  73 .0 62 .5  24 .3 30,.0  2..7  77  3 .9  67 .5  27 .3  1.3 .  70 77 64 64  2 .9 2 .6 4 .7 4 .7  62 67 60 57  .9 .5 .9 .8  34,.3 28 .6 29 .7 37 .5  1.3 . 4..7  275  3 .6  62 .5  32 .4  1 .5 .  8 . 1 64 .5 14 .0 54 .0  27 .4 30,.0  2..0  10 .7  59 .8  28..6  0..9  1 1.6, 14,. 1 4,.8 10,.3  55,.8 50,.0 59,.0 66 .2  32..6 35..9 34..9 23..5  10,.3  57.. 1 32..2  9..07 9.. 10 8 .98 9 .06  8 .97 9.. 1 1  62 50 112  Exptl.  15 15 25 25  Y N Y N  9.. 14 9..21 9.. 17 9.. 18  86 92 83 68 329  Vertebral count . ^30 31 32  (%) £33  Probabl1ity  1 .2 . 0.,3 contd.  Table 5. contd.  Exp.  Treatment  H4  Control  Exptl.  H5  Control  Exptl.  H6  Control  Exptl.  Temp. ( C) Cover 15 25  15 15 25 25  15 25  15 15 25 25  15 25  15 15 25 25  N N  Y N Y N  N N  Y N Y N  N N  Y N Y N  Vertebral count (%)  Mean length (mm)  No. surviving  9. 83 9.,76  123 122  5.,7 8.,2  245 10..26 10.,31 10.,03 10 .22  9 .89 10 . 12  10,.21 10 .05 10 .05 9 .66  11 . 13 11 . 19  1 1.47 11 .67 1 1.54 1 1.66  ^30  31 64,.2 68..9  32  £33  30,. 1 21 . ,3  1., 6  6 .9 66 .5  25,.7  0 .8  128 128 121 125  9..4 7. a 8.,3 6..4  67 .2 63 .3 66 . 1 54 .4  22 .7 28 .9 25,.6 38 .4  0,.8 0 .8  502  8.0  62.7  28.9  0.4  120 119  10.8 11.8  69. 2 70..6  20 .0 16 .8  0. 8  239  11.3  69. 9  18 .4  0.,4  133 126 124 128  10.5 12.7 8.9 13.3  70.,7 68..3 64. 5 64.. 1  18,.0 19 .0 25 .8 21 .9  0. 8  511  11.4  66.9  21.1  0.6  125 113  8. 8 9..7  69,.6 64..6  20,.8 23,.9  0,.8 1., 8  238  9..2  67 .2  22,.3  1..3  110 130 113 1 16  8..2 6..9 4,.4 6..9  72 .7 67,,7 66 .4 75,.0  18 .2 23,. 1 27,.4 18,. 1  0 .9 2 .3 1,, 8  469  6.6  70.4  21.7  1.3  0. 8 0. 8  Probabi11ty  Table 6. Regressions between vertebral number and length in experiments using offspring of Holden Lake sticklebacks. Only results grouped over replications within predation treatments are shown, since slopes are equal among replications (p>0.08). Probabl11ty of equal slopes between treatments  Treatment  No.  Slope  Probability of zero slope  H1  Control Exptl.  240 504  -0.020 0.057  0 .79 0 .27  0.39  H2 ^8.5mm  Control Exptl.  172 205  0.230 0.056  0 . 11 O .65  0.35  H3 <8.5mm  Control Exptl.  137 105  0.724 -0.119  <0 .0001 0 .55  0.001  H2 >8.5mm  Control Exptl.  77 275  0.237 -0.115  0 .37 0..31  0.24  H3 >8.5mm  Control Exptl.  112 329  O. 348 0. 194  0.. 1 1 0.032  0.46  H4  Control Exptl.  245 502  0.088 0. 183  0. 12 0001  0. 18  H5  Control Exptl.  239 511  0.111 0.061  H6  Control Exptl.  238 469  -0.004 0.019  Exp.  <0. o.046 0. 13  O.94 0.59  0.47 0.71  23 would  cause  size  contribute  to the  Therefore,  as  predation cannot  with  control  differed  not  difference  At was  not  5).  At  more  by  in  longer  fish  experimental  treatments  two  were  H4  fish  32  0.68,  selectivity  of  t o be  of  experiments  (Table  differ In  8.0  a t an  p r e d a t i o n appear  (p=0.00l).  mm,  vertebral  than  in control  groups.  with  be 31  between  were  In no  (Table  slightly  groups; more None  at  of  these cover  However, t h e cover  over  fish  experiment  t o depend upon t h e in experimental  with  with  i n the presence other  effect  treatments  fish  the  frequent  and  experiment,  not  predation  number  temperature  (p>0.35).  V e r t e b r a l numbers  Slopes  fish  or above 8.5  advantage  respectively).  6).  of  vertebrae  but  significant  groups c o u l d  31  this  the  mm.  when  together  H3,  treatments  favour  control  i n the absence,  (p>0.50).  in  with  significant  v e r t e b r a e appeared  numbers.  experiment  v e r t e b r a e were u s u a l l y in  to  than  selectivity  these  experimental  for total  experimental  (p=0.0l9).  (p=0.054 and  and  selective  grouped  counts  the  selection  with  the  l e n g t h was  between  l e n g t h s below  of p r e d a t i o n appeared  vertebral  number and groups  than  were  experiment  vertebral  in  in length in  l e n g t h s b e l o w 8.5  prey  in  number  experimental  smaller size,  sizes,  differences  less  vertebral  significantly  of c o v e r  or  stronger  average  the  in  rather  selection.  between c o n t r o l  frequent  larger  mm  significantly  vertebrae at  in  8.5  to s i z e  between but  explained  differences  r e s p e c t to v e r t e b r a l  have been due  correlation  This  observed  p r e d a t i o n to c o u n t e r a c t  i n t h e Kennedy L a k e e x p e r i m e n t s ,  Among f i s h  in  selective  in 32  other  of  cover  did  the  availability groups  did  24 not  differ  (p>0.lO was  significantly  i n a l l cases,  selective  correlation in  size  lengths  between  sizes,  direction the  this  i n a l l but  experimental  below  i n H5  Summary  The  selectivity  (Fig. fish  advantage over  fish  upon p r e y  2).  with with  31 other  mm.  size  lengths  vertebrae  significant  was  or  vertebral  greater  the  are  o f 8.0-8.5 mm, (8.9-11.2  at  i n the  between  number  Holden  a  mm)  with  of  s e l e c t i o n i n any e x p e r i m e n t  at average  Lake  significant exposed  to  exposed  lengths.  When  was u n r e l a t e d t o cover.  respect  f o r v e r t e b r a l number c o u l d  of  between  b u t n o t when  i t s extent  availability  also usually selective  predation  at  to contribute  v e r t e b r a l c o u n t s when  was s i g n i f i c a n t ,  temperature  the  experiments  In b o t h t h e Kennedy and t h e  predation  to  mm,  l e n g t h and i s c o n s i s t e n t  or  selective  was  predation  for total  (7.6 mm)  was  8.5  Among  groups.  at  predation  above  In o t h e r  selective  a t average  either  or  6).  predation  selective  Predation  though not s i g n i f i c a n t ,  of p r e d a t i o n  depends  populations,  smaller  cases).  d i f f e r e n c e s i n v e r t e b r a l number o b s e r v e d  3.  populations  8.0  (Table  correlation,  and c o n t r o l  sticklebacks  two  i n any e x p e r i m e n t  i n a l l e x p e r i m e n t s e x c e p t H5.  t h a t would cause s i z e slight  temperatures  v e r t e b r a l number and l e n g t h  c o n t r o l groups only  these  to  p>0.35  f o r prey  experiments a t prey  between  Although  to prey  size,  n o t be  attributed  lengths  o f 8.0-8.5  25  Figure  2.  Change  sticklebacks (experimental horizontal vertebrae groups;  frequency  of v e r t e b r a l  counts  e x p o s e d t o p r e d a t i o n a t v a r i o u s mean minus c o n t r o l  axis  are  fish).  experiments  a r e more f r e q u e n t  those  vertebrae  in percent  i n which f i s h  i n exposed than  above a r e e x p e r i m e n t s  a r e more f r e q u e n t  P o i n t s below  i n which  i n exposed  in  sizes  the  with  31  i n unexposed fish  groups.  with  32  26  z o  TD CD  1 1  o  < Q LU rr CL  CD Z  Q  >  «+CD  O k_  4  JQ  CD CD  >  C\J ro  0 2  LU ID O LU rr  TD CD  u_  s—  z  _Q CD  X o  o KENNEDY  6  D  o  <  • HOLDEN L.  ^_  >-  LU CD Z  8r  k_ ZS  rae  o > o  CL)  4 6  o  o  8  >  ro  10 12 o 8 AVERAGE  9 PREY  10 L E N G T H (mm)  L  27 A b d o m i n a l and 1.  Caudal  Holden Lake  Count c l a s s e s  experiments  based  on  vertebrae are  shown  Three c l a s s e s  a r e common:  vertebrae  (31  18 c a u d a l caudal  of  with  on  the  experiment  i n any no  count  was  prey  size  progressively  exposure to p r e d a t i o n . with a high  frequent  after  control  groups  frequency  mm, more  fish  frequent  fish. caudal  14 a b d o m i n a l  13 a b d o m i n a l  ratio  3.  and  and  fish  At  18  count  vertebrae  favoured  frequency  differ among  of  between  experimental  smallest during  over  prey  size  exposure  to  i n c r e a s e d above t h i s  value,  ratios  AV/CV were f a v o u r e d  during  prey  0.82  this  l e n g t h s of a b o u t  8.1-8.2  AV/CV were s i g n i f i c a n t l y more groups than  experiments  ratio  average  exposure  of  was  i n t e r m e d i a t e t o low after  s i n c e the not  the  in experimental  with  terms  Data are grouped  did  At  average of  in  treatments  (p=0.006 g r o u p i n g  (p=0.9l)).  with  lower  At  predation  of  cover  class  fish  experiments  Fig.  (p>0.35).  However, a s  the  with  with  17  abdominal to caudal  ratio(s)  between  predation.  fish  of  8 and  favoured  groups  mm,  those  caudal  of Holden Lake  experiments  ratio  nor  with  (TV)), those  and  and  14 a b d o m i n a l and  within p r e d a t i o n treatments, the  mm),  with  predation  temperatures  (7.6  abdominal  TV).  shown i n T a b l e  replications fish  (31  of  7 for offspring  fish  (32 T V ) ,  the  based  (AV/CV) a r e  numbers  t o t a l vertebrae  vertebrae  classes  in Table  vertebrae  Results  Vertebrae  prey ratios  to  did  H2S  not  i n unexposed  and  H3S,  since  differ  between  l e n g t h s of a b o u t  9.8-10.0  of 0.78-0.72 AV/CV  predation  than  were  i n unexposed  28  T a b l e 7. V e r t e b r a l c o u n t c l a s s e s i n c o n t r o l g r o u p s o f H o l d e n Lake p r e d a t i o n e x p e r i m e n t s , b a s e d on numbers o f a b d o m i n a l and caudal vertebrae. Vertebral Total  number  Abdominal 5 4 3 2  Caudal  No. 1 68 68 5  Ratio Abd./Caud.  30  1 1 1 1  31  1 5 1 4 13  16 1 7 18  35 701 196  0.94 0.82 0.72  32  1 5 1 4 1 3  17 18 19  52 290 24  0.88 0.78 0.68  15 16 17 18  1 .00 0.88 0.76 0.67  Table 8. Ratios of abdominal to caudal vertebrae in Holden Lake sticklebacks exposed (exptl.) or unexposed (control) to predation by sunfish. Results of experiments H2 and H3 are shown separately for f i s h 8.5 mm or less (S) or over 8.5 mm (L) in length. Probabilities are from chi-square tests of independence between count class and predation treatment, with f i s h grouped as those with or without the ratio(s) favoured during exposure to predation. (In experiment H1, a ratio of 0.82 is tested). Abbreviations are total vertebral number (TV), number of abdominal vertebrae (AV), and number of caudal vertebrae (CV). Vertebral count class (%) Mean 1ength (mm)  AV: TV: AV/CV:  £0.88  14 31 0.82  14 32 0. 78  13 30 0.76  13 31 0.72  No. surviving  Favoured ratio(s)  Probabi1Ity  5 5 2 6  240 504  (0.82)  0.87  6.4 6.3  2 9 10  172 205  0.82  0.038  10 2 4.8  10. 9 10. 5  10  137 105  0.82  0.062  20. 8 25. 1  2.6 15  9. 1 7.3  13 2 2  77 275  0.78  0.43  44. 6 41 .9  24. 1 27. 7  4.5 5.2  14. 3 13. 4  18 12  112 329  0.78  0.46  10 7 8 8  49. 8 45. 2  20. 4 24 3  2 9 4 6  13. 9 15. 3  2 4 18  245 502  0.78-0.72  0.066  10 01 9 99  9 2 4 9  46. 0 41 .5  13. 0 17. 8  5.9 7 8  21 .8 24. 9  4 2 3 1  239 511  0.78-0.72  0.01 1  1 1 16 11 59  8 4 5 4  52. 5 49. 0  17 2 17. 9  5 5 3 4  1 18. 20. 0  4 7 4 3  238 469  0.72  0.006  Exp.  Treatment  H1  Control Exptl.  7 63 7 89  1 13 1 19  45. 4 46. 0  19. 6 17. 7  4 6 5 4  13. 8 16. 5  H2S  Control Exptl.  8 06 8 15  14 6 15 2  45. 3 56. 1  29. 7 19. 5  1. 2 2.0  H3S  Control Exptl.  8 12 8 20  13 2 11 5  46. 0 58. 1  19. 7 14. 3  H2L  Control Exptl.  8 87 9 05  9 1 13 4  57. 1 50. 5  H3L  Control Exptl.  9 03 9 17  10 7 10 6  H4  Control Exptl.  9 79 10 21  H5  Control Exptl.  H6  Control Exptl.  other  30  Figure  3.  count  Change  in percent  c l a s s e s b a s e d on  vertebrae  (experimental  experiments with horizontal frequency a x i s are control  are  ratio  d u r i n g p r e d a t i o n of v e r t e b r a l  of abdominal to  minus c o n t r o l  H o l d e n Lake  caudal  frequencies), in  sticklebacks. Solid  a x i s are v e r t e b r a l count  bars  those  decreasing  g r o u p a t end a r e as  numbers of  respectively.  1983 above  classes increasing in  d u r i n g e x p o s u r e t o p r e d a t i o n ; open b a r s  Probabilities CV  the  frequency  below  d u r i n g p r e d a t i o n . Mean l e n g t h i n  of experiment in Table  8.  i s given  i n each  A b b r e v i a t i o n s TV,  t o t a l , a b d o m i n a l and  caudal  panel. AV  and  vertebrae,  H I 7.63 mm  5" 0 -5-  JI  10 5  c o  0  o v?  H2S 8.06 mm  TZT  -5  •  CL  X  -10  UJ  ^° 10  Z  H3S  o  5  r-  <  8.12mm  0  Q UJ CC 0,  -5 -10  CD  H2L CC  5  ID Q  0  >- .  8.87mm  -5  U  H3L  UJ  5  o  9.03mm  0  UJ  u.  -5 H4  UJ  0  AN  5  -5  9.79 mm  X o  H5 5  10.01 m m  0 -5 10 5 0  TZZT  1  H6 II.16mm  -5  AV/CV TV  i  >0.88 30-32  i  i  31  32,30  0.82 0.78-0.76  V E R T E B R A L  i  0.72  i  OTHER  31 C O U N T  32 control  groups  frequency  of  fish  experiments AV/CV  with  size  tested  This closer that  ratio after by  increase  AV/CV; not  fish  Selective  experiment  exposure  to  H5,  experiments,  (Table  ratio  9).  and  H6,  fish  increase  of  fish  in  the  have  fish  with is  r a t i o of  r e s p e c t t o the  the  in  number i n  31  vertebrae  ratio  0.72  of  0.82  AV/CV  did  sizes. AV/CV  cannot  t o have g r e a t e r s u r v i v a l  during  H2S  and  were  In  H3S,  fish  slightly  c o u l d not  with  (though  of  fish  ratio(s)  fish  not  groups  with  this  ratio  In e x p e r i m e n t s were  groups  slightly with  the  have c o n t r i b u t e d t o  experiments.  contributed of  In other  frequency  favoured  for  experiments.  occurred.  AV/CV  two  the  accounted  ratio  these  for  a l l  selection  frequency  0.72  experiments  frequent at greater lengths in c o n t r o l  with the  may  of  selection  with a high  a low  In e x p e r i m e n t s  i n these  these  p r e d a t i o n at  p r e d a t i o n at these  tended  0.82  of  of  fish  at greater lengths in control  selection  ratio  Lake  8.1-8.2 mm  selection  i n c r e a s e i n the  predation  frequent  size  of  less  Holden  result  selection  Hence, s i z e  the o b s e r v e d during  no  longer  significantly)  size  the  after  size  to predation.  favoured  H4  the  v e r t e b r a e and  predation with  attributed  s i n c e the  d i f f e r between  w i t h a low  increased frequency  31  H5,  predation for total vertebral  increase in frequency  be  of  in frequency  with  and  frequent a f t e r  p r e d a t i o n a t l e n g t h s of a b o u t  the  H4  mm).  is evidently  The  d i d not  fish  more  (11.2  selective  AV/CV.  ratios  examination  these experiments  experiments  Finally,  significantly  prey  reveals  these  (p=0.44)).  were  largest  (p=0.002 g r o u p i n g  slightly  (Table 9). to these  the  H2L, more  Hence, observed  ratios  during  Table 9. Relationship between vertebral count class and length 1n control groups In Holden Lake experiments. Frequencies of f i s h with the favoured ratio(s) are shown for lengths less than or equal to the mean (S) or greater than the mean (L). Probabilities are ch1-square tests of Independence between vertebral count and size classes, with f i s h grouped as those with or without the favoured ratio. Size cl ass  Mean 1ength (mm)  Frequency of favoured ratio (%)  No.  Probabi1  (0.82)  S L  7.. 16 8 .05  43,.0 47 .6  1 14 126  0.47  H2S  0.82  S L  7 . 74 8 .29  51 .4 41 .0  72 100  0. 23  H3S  0.82  S L  7,.80 8..38  46..8 45,.3  62 75  1 .00  H2L  0.78  S L  8 .70 9 .07  14 .6 27 .8  41 36  0.26  H3L  0.78  S L  8..77 9.35  24,.2 24. O  62 50  1 .00  Exp. H1  Favoured rat lo AV/CV  H4  0.78-0.72  S L  9.29 10.,30  36. 9 37 , .4  122 123  0.93  H5  0.78-0.72  S L  9.51 10. 54  35. 5 46., 1  124 1 15  0. 10  S L  10. 53 1 176 .  10. 3 13. 1  1 16 122  0.51  H6  0. 72  34 predation the  i n these  frequency  between  fish  (Table  9).  in  favoured  this  mean  However,  ratio(s)  size  than  i t i s unlikely  in a  experiments. the counts  of s i z e  expected  selection  the favoured  To f u r t h e r in  alone.  r a t i o ( s ) was  did  groups  much  between  that  case  control  involves  that  no  differ significantly  length  comparison  in  greater  control  and  selective predation  t o t h e r a t i o AV/CV c a n be e x p l a i n e d by s i z e  I calculated  with  the  groups,  of these  result  experiments.  below o r a b o v e t h e mean  experimental  any  of  Since  difference  respect  other  rule  selection  out t h i s  experimental  The e x p e c t e d calculated  with in  possibility, groups  frequency  as  E of  a  fish  as  E = (^ j P j N j ) / Nt where  Pj  is  the frequency  of  fish  in  the j t h s i z e c l a s s  in control  in  the j t h s i z e c l a s s  i n experimental  number  of  fish  distinguished: ^  X+0.68s,  groups,  i n experimental (1) L  and  (4)  ^ X-0.68s, L  >  deviation  experiments  the  ratio  AV/CV  control  differed  groups,  experimental selection  which  it  g r o u p s and  alone  ratio(s)  Nj i s t h e number o f  groups,  groups.  and Nt  Four  fish  i s the t o t a l  size classes  (2) X-0.68S < L  in  control  frequency  significantly  ^ X,  were  (3) X < L  groups.  of f i s h between  also  differed  those  expected  ( T a b l e 10).  the favoured  X+0.68s, where X and s a r e t h e mean  l e n g t h and i t s s t a n d a r d in  with  with  the  favoured  experimental  significantly as  In a l l  a  result  and  between of  size  Table 10. Ratio of abdominal to caudal vertebrae (AV/CV) In Holden Lake sticklebacks exposed (experimental) or unexposed (control) to predation by sunfish, and the ratio expected in exposed f i s h If predation Is selective for prey size but not for the ratio AV/CV. Frequencies of f i s h with the favoured ratio are shown. Probabilities are ch1-square tests comparing the observed frequency In experimental groups and that expected due to size selection alone. Probabilities are calculated assuming that the expected frequency due to size selection alone Is a sampled value, with sample size equal to that In control groups. Frequency of favoured ratio (%)  Exp.  Favoured rat 1o AV/CV  H1 (0.82) H2S 0.82 H3S 0.82 H2L 0.78 H3L 0.78 H4 0.78-0.72 H5 0.78-0.72 H6 0.72  Experimental Control 45.4 45 . 3 46 .0 20.8 24 . 1 37.2 40.7 11.8  Expected due to size selection 46.0 44 .6 46. 1 16.8 24 .8 37 .4 40.5 12.9  Observed 46.0 56. 1 58 . 1 25 . 1 27.7 44.2 50.5 20.0  Probabl11ty >0.90 0.025 0.05 0.05 0. 10 0. 10 0.25 0.50 0.75 0.05 0. 10 0.01 0.025 0.025 0.01  36 2.  Kennedy L a k e  The  division  caudal seen  regions  i n Holden  have  one  experiments  of the  vertebral  i n Kennedy Lake Lake  fish  (Table  more a b d o m i n a l  same t o t a l  vertebral  vertebrae  tended  fish  be  into  differed  11).  vertebra  count.  to  column  markedly  Kennedy L a k e  than Holden  Thus,  ratios  higher  abdominal from  fish  Lake  i n Kennedy t h a n  that  tended to  fish  of abdominal  and  with the  to  caudal  i n Holden  Lake  fish.  In  e x p e r i m e n t s K2  Holden  Lake  fish,  in  v e r t e b r a e at advantage prey size  size  increased  i n experiment  unexposed prey  control  size  in  fish  after groups  differed about Lake  at  8.1-8.2 fish,  mm,  w h i l e one  Results  above.  counts of  31  regardless  with high  after  of  However, r e s u l t s  to caudal  decrease  At the smaller of  0.88-0.94  fish  Conversely, w i t h low  predation during  K1  was  at  ratios  (p=0.024).  as prey  AV/CV than i n  the  larger  o f 0.78-0.82 However,  predation  at a given  At average  prey  favoured i n Holden  d e p a r t e d somewhat  In t h i s e x p e r i m e n t ,  the  to  using  the size  sizes  of  o f 0.88-0.94 were f a v o u r e d i n Kennedy  o f 0.82  appeared  4).  ratios  populations.  ratios  of abdominal  i n e x p e r i m e n t a l groups  (p=0.027). K3,  t h o s e seen  appeared  Fig.  predation  i n experiment  described  predation  advantage  between t h e two  resembled  ratios  12 and  experiment  ratios  the  during  AV/CV were more f r e q u e n t actual  results  that  (Table  K2,  were more f r e q u e n t  and K3,  to  be  proportion  d i d conform  to  at  fish  from the  with t o t a l  advantage  expected  were  fish.  pattern vertebral  during  of v e r t e b r a e t h a t the  Lake  predation abdominal.  pattern  to  the  37  T a b l e 11. V e r t e b r a l c o u n t c l a s s e s i n c o n t r o l g r o u p s o f Kennedy Lake p r e d a t i o n e x p e r i m e n t s , b a s e d on numbers o f a b d o m i n a l and c a u d a l v e r t e b r a e . Vertebral  number  Total  Abdominal  Caudal  30  1 5 1 4  15 16  6 22  1 .00 0.88  31  16 15 14  15 16 1 7  1 198 138  1 .07 0.94 0.82  32  1 6 1 5 1 4  16 1 7 18  1 2 250 70  1 .00 0.88 0.78  33  15  18  No.  6  Abd./Caud.  0.83  Table 12. Ratios of abdominal to caudal vertebrae 1n Kennedy Lake sticklebacks exposed (experimental) or unexposed (control) to predation by sunfish. Probabilities are from chi-square tests of Independence between vertebral count classes and predation treatments, with f i s h grouped as those with or without the ratios favoured during exposure to predators. In experiment KI, two ratios (0.94 or 0.82) are tested. Abbreviations are as in Table 8. Vertebral count class (%) Mean 1ength (mm)  AV: TV: AV/CV:  15 31 0.94  15 32 0.88  14 31 0.82  14 32 0.78  Exp.  Treatment  K1  Control Exptl.  8.31 8.43  21.0 29.2  40.3 32.2  19.9 24.6  17.6 10.8  K2  Control Exptl.  8. 18 8.50  24.7 31.3  30.5 32. 1  22.2 21.5  12.3 5.8  K3  Control Exptl.  8.92 9. 10  35.6 35.7  37 .0 30.5  17.3 21.3  3.2 6. 1  Other 1.1 3.2  No. surv1v1ng  Favoured rat1os  Probabl1i ty  176 463  0.94 0.82  0.038 0.21  10.3 9.4  243 608  0.88-0.94  0.027  7.0 6.4  284 653  0.78-0.82  0.024  39  Figure  4. Change  vertebral  i n percent  frequency during  count c l a s s e s based  experiments  using  abbreviations  predation  on t h e r a t i o AV/CV,  of  i n 1982  Kennedy L a k e s t i c k l e b a c k s . Symbols and  a r e a s i n F i g . 3.  ko  K2 8.18 mm  10  <  0  o  UJ LT CL  C9  - i o  Z)  Q  Z)  a LLI  KI 8.31 mm  C  O  O ^ LU  L  °  10  ^  0  I CL  x  LU  Ll  ~ IOL  K3 8.92 mm  lOr  0  UJ CD z: < x o  -10 AV/CV TV  0.94 31  0.88 0.82 0.78 Other 32  31  VERTEBRAL  32 COUNT  41 extent  that  this  increase i n frequency  of f i s h  after  p r e d a t i o n was s i g n i f i c a n t among f i s h  0.94  AV/CV  0.82 AV/CV  to  predation with  vertebrae  experiments.  have  higher  fish  with  fish  before 3.  w i t h a lower  respect to the r a t i o  cannot  be a t t r i b u t e d  survival  abdominal  was l o w e r  in control  predation  apparently  to caudal  among  intermediate survival  abdominal  selection in  larger  in larger  groups  (0.78-0.72)  f r y with  greatest or  experiments  with  total  resulted  survival  (9.8-10.0  was  for  vertebrae.  sticklebacks,  greatest  fish  tended  than  i n smaller  (Table 13).  low  vertebral  from  high  mm)  or  for  f r y with  (0.72)  Kennedy  large  of  (11.2  size  increased.  Kennedy t h a n a given  predation selection.  i n H o l d e n Lake prey  size  for vertebral  in  fish, the  count  0.82  and h i g h e r Kennedy  prey  the  to ratios  lake  Holden was  AV/CV.  mm)  tended  tended  these  (8.1-8.3 mm)  respectively.  sticklebacks,  However, r a t i o s  with  intermediate  ratios,  Lake  sizes  ratio  in  f o r the r a t i o of  I n 1983 e x p e r i m e n t s  a t small prey a  number  selection  advantage d u r i n g exposure t o p r e d a t i o n a l s o  at  r a t i o of  Summary  experiments  prey  of  d u r i n g p r e d a t i o n , but the frequency of  ratios  predation  of  to size  In a l l t h r e e e x p e r i m e n t s ,  the favoured  Selective  Lake  ratio  (p=0.2l).  caudal  these  31 v e r t e b r a e  with a high  (p=0.038), b u t n o t among t h o s e  Selective to  with  At  sizes, to  low  In  1982  ratios  at  to decrease  as  be  in  higher  were  fish.  r a t i o was n o t a t t r i b u t a b l e  favoured Selective to size  Table 13. Ratios of abdominal to caudal vertebrae In control groups in Kennedy Lake experiments, at lengths less than or equal to (S) or greater than (L) the mean length. Probabilities are from c h i square tests of independence between vertebral count and length classes, with f i s h grouped as those with or without the ratios favoured during predation. In experiment K1, two ratios (0.94 or 0.82) are tested. Abbreviations are as 1n Table 8. Vertebral count class (%)  Exp.  Size cl ass  AV: TV: AV/CV:  15 31 0.94  15 32 0.88  14 31 0.82  14 32 0.78  Other  No.  1.3 1 .0  80 96  Favoured ratios  Probabi11ty  0.94 0.82  1.00 0.33  K1  S L  21.3 20.8  36.3 43.8  23.8 16.7  17.5 17.7  K2  S L  29.2 20.3  27.5 33.3  23. 1 21.1  9.2 15.4  10.8 9.8  120 123  0.88-0.94  0.64  K3  S L  32.5 37.9  35.8 37 .9  20.3 14.9  4. 1 2.5  7.3 6.8  123 161  0.78-0.82  0. 15  4=>. K>  43 Body 1.  Proportions Holden Lake  Selection vertebrae  with  could  proportions.  of  To  directly  and  However, count (I  use  these  those  ratio,  length.  As  explain  by  length  over  is considerable  vertebral  count  classes  may  relative  head  lengths,  and  vertebrae  vertebrae  per  (i.e.,  in  significantly intercept, decreased H5,  and  LR  and  during  exposure  increased  during  length  is  the  length  the  ratio  ratio  were 14).  in length  ratio  as  Methods) caudal calculated  much o f  (Fig.  (LR).  length  with  variation  i n VR  regression  of  experimental  predation  i n the  abdominal body  within  variation  from v a r i a t i o n of  as  class,  This variation from  in  this  a v e r t e b r a l count  5).  number  predation  the  partly  to predation  were  length  expected, this  the  variation  partly  selective  considered  in vertebral  between c o n t r o l and  indicating  total  the  body  variation  u n i t of abdominal or c a u d a l  In most e x p e r i m e n t s ,  to  overall  result  the  caudal  (p<0.000l) r e l a t e d (Table  i t ) . Within  i n LR  to  respect  I  be  ratios  twice  c a l c u l a t e d without  with  and  ( s e e M a t e r i a l and  since  abdominal  precaudal  might  the  variation  of  where  vertebrae  i s explained  analyses  of  possibility,  30-65% of  adjusted  ratio  selection  significantly  about  (VR)  the  this  caudal  highly  the  adjustment do  to  only  ratio  test  caudal  to  from  length  minus t h e  abdominal  respect  result  precaudal/caudal total  experiments  in  spacing  or  caudal  length).  VR  on  groups  f o r VR,  LR  LR  differs  in slope or  both.  i n e x p e r i m e n t s H1,  i n e x p e r i m e n t H6  H2S  (Table  or LR and  15).  i n v e r s e l y r e l a t e d (p<0.05) i n a l l f o u r  T a b l e 14. R e g r e s s i o n to caudal length  o f t h e r a t i o o f a b d o m i n a l t o c a u d a l v e r t e b r a e (VR) on t h e r a t i o o f p r e c a u d a (LR) i n c o n t r o l and e x p e r i m e n t a l groups o f - H o l d e n Lake e x p e r i m e n t s .  Probabi1i ty VR No.  v s LR  Intercept  Slope  zero s i ope  e q u a l i t y of s l o p e s and Intercepts  equality of s l o p e s  2 r  Exp.  Treatment  H1  Control Exptl.  240 504  0..1514 0..3215  0 .4683 0 .3518  <0..0001 <0..0001  0.0005  0.009  0.40 0. 32  H2  Control Exptl.  249 480  0.. 1806 0..0710  0..4572 0..5446  <0 .0001 <0..0001  0.0001  0.038  0.44 0.47  H3  Control Exptl .  249 434  0., 1 136 9 . 1310  0,.4971 0 .4863  <0..0001 <0..0001  0.60  0.78  0.53 0.48  H4  Control Exptl.  245 502  0 .0746 -0..0740  0 .5341 0..6430  <0 .0001 <0..0001  0.026  0.007  0.48 0.61  H5  Control Exptl.  239 511  -0..0398 -0.. 1042  0..5965 0 .6494  <0..0001 <0..0001  0.0006  0. 13  0.66 0.63  H6  Control Exptl.  238 469  0..0273 -0..0800  0..5657 0..6308  <0..0001 <0..0001  <0.0001  0.085  0.54 0.66  45  Figure  5. R a t i o s  count  of p r e c a u d a l / c a u d a l  c l a s s e s VR  (experimental,  of Holden  open  bars) to predation abdominal three VR;  B. H2S,  C. H6,  by  A. H1, selection  selection  s u n f i s h . VR  vertebrae. predation favouring  favouring high  (LR)  in vertebral  s t i c k l e b a c k s exposed  b a r s ) or unexposed  to caudal  cases:  Lake  length  (control,  i s the r a t i o  Results selective  black  of  a r e shown f o r f o r LR  but  not  low LR b u t h i g h VR;  and  LR b u t low  VR.  Table 15. Body proportions of Holden Lake sticklebacks exposed (exptl.) or unexposed (control) to predation by sunfish. Body proportions are the pre-caudal length divided by the caudal length. When length ratios are related (p<0.05) to total length, adjusted ratios are also shown. When slopes of this relationship d i f f e r (p<0.05) between predation treatments, slopes within treatments are also shown. Methods of adjustment are : (A) no adjustment made. (B) ratios adjusted to grand mean length (standard analysis of covariance), ( C ) ratios in control group adjusted to mean length in experimental group, or (D) ratios In experimental group adjusted to mean length in control group. Regression between length ratio and total Probability of Exp.  SI ope  zero s 1 ope  H1  -0.00229  <0.001  H2S  -0.00176  H3S  equal slopes  Treatment  0.42  Control Exptl.  0.039  0.023  Control Exptl.  -0.00487  <0.001  0.56  Control Exptl .  H2L  0.00113  0.20  0.41  Control Exptl.  H3L  -0.00188  0.007  0.015  Control Exptl.  H4  -0.00090  0.002  0.54  Control Exptl.  H5  -0.00117  <0.001  0.66  Control Exptl.  HG  -0.00055  0.033  0.56  Control Exptl.  Slope  — -0.003G7 0.00181  -— 0.00136 -0.00278  -—  --  length Probability of zero si ope  -0.004 0.87  ----0.41 0.0003  -------  Precaudal/caudal No.  Mean  SE  length ratio  Adjusted mean  Adjustment method  Probability of equal means  240 504  1.3832 0 .00433 1. 3642 0 .00297  1.3782 1.3666  B  0.029  172 205  1. 3830 0 .00497 1.3671 0..00455  1.3788 1.3671  C  0.079  137 105  1.3928 1.3946  0 .00526 0 .00601  1.3907 1.3973  B  0.41  77 275  1.3673 1.3639  0 .00719 0 .00374  --  A  0.66  1 12 1.3830 0..00646 329 1. 3753 0,.00374  1. 3829 1.3802  D  0.71  245 502  1.3635 0..00402 1. 3566 0..00276  1.3604 1.3581  B  0.64  239 511  1.3951 1.3687  0,,00417 0..00285  1.3952 1.3686  B  <0.001  238 469  1.3695 1.3817  0.,00432 0..00304  1.3676 1.3827  B  0.005  Note: Regressions are calculated with length In ocular micrometer units: 1 unit = 0.082083 mm. SE = standard error.  48 experiments,  but s e l e c t i v e  attributed  to  significant  decrease  adjustment  size  of  In experiment  remains  lower  although  than  the  low  groups  no  size  during  In  predation  H2S, t h e mean LR that  of  was l o w e r  selection  (H5) p r e y s i z e s ,  of  control  between In  of  occurred.  t o a common  total  the  adjustment, approaches  t o LR.  predation  w h i l e h i g h LR was  LR  groups  experiment  with respect  groups  mean  control  In  a  after  only  H5,  be  persists  after  groups  that  H1,  experimental  groups  experiment than  t o LR c a n n o t  experiment  and e x p e r i m e n t a l groups  LR was sometimes f a v o u r e d d u r i n g  prey  of even  H6,  size  In summary,  at small  favoured  (H1,H2S) at  large  s i z e (H6). Results Table  overall count  a r e shown s e p a r a t e l y  16  and  selection  However,  vertebral  experiment  H5,  experiment  experiment obscured  and  class H2S,  by  common t o t a l predation  count  with  length  in  for  only approached  LR  (0.82) VR.  experiment, significance  does  H3L  LR  was  in a l l  In  partly  adjusting  the decrease combining  In  i s greatest i n (VR^0.88).  After  in  and H4.  apparently  significant  occur  treatment  predation mean  class  significant  direction  experiments  low  1 5 ) , b u t was h i g h l y  with  predation  highest  for high  in this  and  same  count  interaction  i n LR d u r i n g  the  selection  the  significant  possibly  selection  (Table  In a l l experiments  class  H5, t h e d e c r e a s e  count  classes  F i g . 5.  f o r each v e r t e b r a l  f o r LR, i t i s i n  classes.  between  the  with respect  alone.  counteracted selection  or medium  in  LR  (p=0.08).  experimental  selection  in  difference  significance  though  selection  control  length.  predation  to a  i n LR d u r i n g  vertebral  within  count  vertebral  Table 16. Change in precaudal/caudal length ratio (LR) within vertebral count classes in Holden Lake sticklebacks after exposure to predation in 1983. Data are the mean in experimental groups minus that in control groups. Unadjusted data and data adjusted to a common total length (TL) are shown. Adjustment A employs standard analysis of covariance; tests of zero slope and equality of slopes among groups are shown for the regression of'LR on TL. Groups with slopes differing (p<0.05) from the slope of other groups combined are noted. A second adjustment B is shown when slopes are heterogeneous among groups. PT is the probability that mean LR does not d i f f e r between predation treatments, and PT x CT the probability of no interaction between predation treatment and count class. Abbreviations: C = control, E = experimental, C72 = control with 0.72 abd./caud. vertebrae. Ratio abdominal/caudal  vertebrae  Probability  Probability f slopes Q  Exp.  Method  50.88  0.82  0.77  0.72  PT  PT x CT  z e r o  0  Probability f equal slopes  Groups differing from rest  H1  Unadjusted Adjusted A Adjusted B  -0 .018 -0 .015 -0 .010  -0..017 -0..012 -0..008  0..027 0..020 0 .018  -0,.030 -0 .021 -0 .018  <0..0001 0..0002 0,.0025  0,.44 0,.79. 0,. 73  <0.0001  0.007  C72, E77  H2S  Unadjusted Adjusted A Adjusted B  -0 .040 -0 .037 -0 .035  -0..017 -0..015 -0..016  0,.004 0..004 0..004  -0,.033 -0,.032 -0 .032  0..0004 0..0009 0..0010  0.. 13 0,. 17 0,.22  0.005  0.09  C88  H3S  Unadjusted Adjusted A Adjusted B  -0..024 -0..019 -O .031  •0,.002 0,.001 0..001  -0,.023 -0,.022 -0..023  0.. 17 0.,27 0.. 12  0,.21 0.. 19 0,.076  0.0004  0.18  E88  H2L  Unadj usted Adjusted A  0..008 0 .002  -0.,009 -0..013  0..010 0.,014  0..014 0 ,010  0.,93 0.,64  0..62 0.,67  0.013  0.93  H3L  Unadjusted Adjusted A Adjusted B  -0..025 -0..025 -0..028  0.,008 0.,009 0.,010  0.,014 0.,013 0..012  0.,015 0..019 0..020  0.53 0.68 0..65  0.,069 0.,054 0.,034  0.15  0.17  C88  Unadjusted Adjusted A Adjusted B  -0..002 -0..002 -0..002  -0. 001 0.,002 -0.,001  0..002 0..0003 0.,016  -0.,013 -0,,01 1 -0..013  0.,24 0.,49 0.,94  0.,60 0..61 0..044  0.033  <0.001  C77  H5  Unadjusted Adjusted A  -0..058 -0..057  -0.,016 -0.,016  0.020 0.020  -0.018 -0.018  <0.0001 <0.0001  0.012 0.012  H6  Unadjusted Adjusted A Adjusted B  0..018 0..021 0 ,024  0.025 0.027 0.027  0,,028 0..030 0.,030  0,.007 0,.009 0,.009  0.,0011 <0.,0001 <0..0001  0.49 0.,25 0.26  0.010  0.18  0.015  0.15  H4  0.,009 0.,01 1 0.,010  E88  Note: Adjustment B: (1) H1: slopes homogeneous among control groups; LR In control groups adjusted to mean TL in experimental groups. (2) H2S, 3S, 3L, and 6: slopes homogeneous among groups omitting the group noted in table; LR is adjusted to the mean TL of a l l groups combined, using either the slope in the differing group or that in a l l other groups combined. (3) H4: slope Is significant In C77 only; LR in C77 adjusted to mean TL in E77. vo  50 count  c l a s s e s (Table 16). Selection  for  the  with  ratio  respect  of  abdominal  e x p e r i m e n t H1, s e l e c t i o n In  t o LR c a n n o t to  caudal  was s i g n i f i c a n t  e x p e r i m e n t H2S, s e l e c t i o n  favoured  In e x p e r i m e n t s H3S a n d H4, s e l e c t i o n VR  (p=0.06-0.07) b u t n o t f o r LR  selection  favoured  experiments but  not the other  and the  H6)  high  high  selection  while  f o r one a t t r i b u t e  In  for  VR.  significance  for  In e x p e r i m e n t  LR.  Thus,  in  was s i g n i f i c a n t  i n other  H6, some  f o r one  e x p e r i m e n t s (H2S  counteracted  selection for  other. 2.  Kennedy L a k e  experiments  Body p r o p o r t i o n measurements were made K2  (VR).  (0.82) VR b u t low LR.  (p=0.40-0.60).  attribute,  selection  f o r LR but n o t  H3S, a n d H4) s e l e c t i o n prey  for  vertebrae  approached  low (0.72) VR b u t  (H1,  account  only.  length  Two  l e n g t h r a t i o s were c o n s i d e r e d :  (LR1) a n d p r e c a u d a l / c a u d a l  = t o t a l - head - c a u d a l abdominal  length).  (p<0.000l); ratio  length;  usual  employed those  l e n g t h = head l e n g t h +  r a t i o s were h i g h l y  u s e d when t h e s e  correlated  i n the precaudal/caudal  i n the abdominal/caudal  l e n g t h r a t i o s c o u l d n o t be compared among vertebral  length  ratio in  respectively.  count  to distinguish  r a t i o VR',  abdominal/caudal  (LR2) ( a b d o m i n a l  precaudal  80 a n d 86% o f t h e v a r i a t i o n  e x p e r i m e n t s K1 a n d K2,  the  length  The two l e n g t h  was e x p l a i n e d by v a r i a t i o n  These  i n e x p e r i m e n t s K1 a n d  r a t i o VR,  abdominal  s i n c e the c r i t e r i a  from c a u d a l  vertebrae  l e n g t h m e a s u r e m e n t s were made.  b a s e d on t h e  numbers  of  classes  vertebrae  of  finally  were  not  Instead, a  anterior  to  or  51 opposed VR  and  and VR'  K2.  In  were e q u i v a l e n t the remainder,  vertebra  from t h a t  Both with  p o s t e r i o r t o the  length  VR'  ratio,  variation  17).  However, one  ratio  i n the s p a c i n g  of  Holden  despite Lake  comparison. between  experiments (Table  17).  (Table  count  even  for  is the  latter  c l a s s e s must be due  length  i n Holden  length  i n VR  but  regressions  (Tables  length in  o f VR  experimental  14), but n o t  explained  fish  not  criteria  VR  fish  to  LR  (Table fish  14 and  used  the Lake  result  to d i s t i n g u i s h abdominal  was 15),  (Table  17).  usually  in  i n t h e Kennedy  Lake  LR  in This  i n the  i n t h e Kennedy  groups  i n t h e LR a n a l y s i s o f H o l d e n  VR')  variation  i n t h e LR  LR1 on  by  (or  fish.  i n Kennedy Lake  was  o f head  Lake  Some o f t h e s e d i f f e r e n c e s m i g h t  o f more a p p r o p r i a t e vertebrae  and  i n Kennedy Lake  and  one  ratio  In t h e c a s e o f t h i s  Lake  the i n c l u s i o n  control  6).  Holden  Finally,  by  correlation  in length  between Kennedy and  comparison,  and  vertebrae.  More o f t h e v a r i a t i o n  occurs  here.  K1  differed  significant  variation  within  r e l a t e d to t o t a l  than  i n VR'  or  r e l a t e d to t o t a l  i n Holden  used  length  inversely  be u s e d  i n experiments  total  somewhat  LR  fish  v e r t e b r a l count c l a s s ,  (Fig.  differed  18).  basal, w i l l  VR.  most v a r i a t i o n  directly  of  the d i v i s i o n  R e l a t i o n s h i p s between LR  but  anal  showed a h i g h l y  w i t h i n any  abdominal/caudal  i n 89%  in  ratios  (Table  considerable  length  used  first  Lake  differed  Holden  Lake  experiments from from  experiments.  the  use  caudal  Table 17. Regression of vertebral count ratio VR' on length ratios LR in Kennedy Lake f i s h . VR' is the number of vertebrae anterior to the f i r s t anal basal divided by the number opposing or posterior to i t . LR1 is the length from the f i r s t vertebra to the f i r s t one opposing or posterior to the f i r s t anal basal divided by the length from the latter point to the end of the hypural plate. LR2 resembles LR1, but includes the head length in the numerator. Regressions are shown separately for control and experimental groups, and equality of slopes and intercepts tested between the two. Probabi1i ty equal slopes and 1 ntercepts  equal s1 opes  Exp .  LR  Treatment  No.  Intercept  S1 ope  zero slope  K1  1  Control Exptl.  17S 460  0. 3778 0. 4882  0..4912 0.. 3765  <0..0001 <0..0001  0.36  0. 19  0. 19 0. 15  2  Control Exptl.  176 460  0. 4252 0. 4824  0., 2555 0.. 2205  <0..0001 <0..0001  0.72  0. 54  0. 13 0. 12  1  Control Exptl.  232 460  0. 3349 0. 3314  0..5465 0..5592  <0..0001 <0.,0001  0.052  0.86  0. 28 0. 24  2  Control Exptl.  232 605  0. 2535 0. 2997  0..3667 0., 3430  <0..0001 <0.,0001  0.25  0.63  0. 27 0. 20  K2  r  2  Figure  6.  Ratios  of abdominal/caudal  c o u n t c l a s s e s VR' (experimental,  by  by s u n f i s h . VR'  a n t e r i o r to the f i r s t  t h e number  in vertebral  o f Kennedy Lake s t i c k l e b a c k s e x p o s e d  open b a r s ) o r u n e x p o s e d  bars) to predation vertebrae  length  opposing  (control,  black  i s t h e number o f  anal  basal  and p o s t e r i o r t o i t .  divided  5h  1.0  1.2  L R 2 = ABD0MINAL /CAUDAL  1.0  1.2  LENGTH  Table 18. Body proportions of Kennedy Lake sticklebacks exposed (exptl.) or unexposed (control) to predation by sunfish. Body proportions LR1 and LR2 are as defined 1n Table 17. When LR is significantly (p<0.05) related to total length TL, adjusted LR is also shown. When slopes of regressions of LR on TL d i f f e r significantly between predation treatments, slopes within treatments are also shown. Adjustment methods are as in Table 15, except that in D control and experimental groups are adjusted to the grand mean TL using the separate slopes within each group. Probabi11ty Exp.  LR  S1 ope  K1  1  -0.00OO1  2 K2  zero s 1 ope  equal slopes  Treatment  Probabi1i ty of zero SI ope slope  Mean  0.96  0.53  Control Exptl.  --  0.00121  0.008  0.28  Control Exptl.  --  1  0.00034  0. 10  0.004  Control Exptl.  0.00129 -0.00004  0.003 0.85  0 .9870 0 .9797  2  0.00133  <0.001  0.015  Control Exptl.  0.00250 0.00086  0.0001 0.012  1.6920 1.6900  SE  Adjusted mean  --  Adjustment method  Probability of equal means  A  0.018  1.7052 1 .7241  B  0.015  0..00332 0,.00207  0.9919 0.9797  C  0.002  0..00486 0,.00304  1.6967 1 .6879  D  0.12  —  0 .9827 0 .9946  --  1.7039 0..00655 1. 7246 0..00404  0..00430 0..00265  56  Selective two LR  predation with  experiments  (Table  18).  i n c r e a s e d i n experiment  (after total  adjustment length).  contributed vertebrae ratio  i n experiment  in  experiment  K2.  with  r a t i o s cannot respect 3. In  g r o u p s t o a common to  LR  have  to caudal  selection  i n these with  may  for  this  experiments as i n  respect  to  vertebral  be a t t r i b u t e d  solely  to selection  Holden  fish,  low  ratios.  1983 e x p e r i m e n t s u s i n g favoured  h i g h LR was f a v o u r e d  1982  experiments smaller size  with  f r y size in  at large  i n experiment K1.  r a t i o was n o t a t t r i b u t a b l e  some  experiments, prey  for  one a t t r i b u t e  selection  attribute,  LR  Similarly,  was  K2, and h i g h LR a t t h e  to this  in  other  selection  in  low LR was f a v o u r e d a t  predation selection  larger  for vertebral for  LR.  was s i g n i f i c a n t f o r one b u t n o t  while  counteracted  sizes.  fish,  Selective  count  other  fry  Kennedy L a k e  experiment  the  Lake  d u r i n g p r e d a t i o n a t s m a l l o r medium f r y s i z e s ,  while  fry  selection  K2  Summary  sometimes  the  experiment  the r a t i o of abdominal  Therefore,  i n general  to length  in  respect  K1, b u t c o u n t e r a c t e d  t h e H o l d e n Lake e x p e r i m e n t s , count  decreased  with  for  the  e x p o s u r e t o p r e d a t i o n , mean  and e x p e r i m e n t a l  selection  selection  t o LR d i f f e r e d between  During  K1, b u t  of c o n t r o l  Thus,  to  respect  experiments f o r the other.  In for  selection  57  Part  II.  Burst  swimming  performance  of  threespine  sticklebacks M a t e r i a l s and Methods F i s h . used sticklebacks August a  were  collected  1984, a n d June  single  collection  together  a t about  and  crosses  and  15  embryos  hatching, parents 5  from  1985.  Holden  Lake  of parents,  14C  simulated  Burst mm in  in  made  1985.  twice  a single  0.6 m s q u a r e  fry  were i n t r o d u c e d  opened, swimming applied  was  daily.  14  and  1  23C.  After  collection 46h  use.  of p a r e n t s , and  after  fertilization  i n a l l years,  Illumination  was  I n 1985,  f r y were f e d  artificial,  but  photoperiod.  was m e a s u r e d o f f r y a b o u t  was m e a s u r e d  i n 1984 a n d 1985.  i n a tank  switched  initiated  on,  to  a  sliding  emerge  using  t h r o u g h two s t a i n l e s s  from  an a . c .  steel  1 m square  7-11.5  i n length i n 1983,  Water d e p t h was 3 cm.  i n t o a 3x3 cm c o n t a i n e r  and f r y a l l o w e d was  reared  of parents,  i n 1983 a n d 1984, a n d o f f r y 9.4-11.5 mm  or  floodlight  After hatching  swimming p e r f o r m a n c e  Performance  from  I n 1984, between  a n d h e l d a t 15C u n t i l  from  the n a t u r a l  length  were made  r e a r i n g t e m p e r a t u r e and c o l l e c t i o n o f  together,  thereafter.  Artemia n a u p l i i  1983, J u n e -  were made f r o m e a c h o f 8 c o l l e c t i o n s  f r y from a s i n g l e  breeding  a n d t h e embryos p r o d u c e d  r e a r e d a t t e m p e r a t u r e s between  were  of  i n August  I n 1983, 113 c r o s s e s  embryos r e a r e d a t . 14C, o r a t 22C u n t i l and  offspring  17C i n t h e same 75 L t a n k .  were m i x e d  crosses  laboratory-reared  grids  in this door  the  Single  tank.  A 250W  i n the container  container.  electric  shock  15 cm a p a r t .  Burst stimulus  In  1983,  58 swimming  was  swimming noted  in  a  followed  below).  overhead at  2V/cm  a 32  45 In  1983,  17C;  i n 1984  and  1985,  bath  which maintained or  will filmed  was  or  15C  (viscosity  in  a  15.OC  about  Some f r y f i l m e d  stimulus  48  duration  measured  under  viscosity  treatments:  poise  (in  15C  solution). and  Fry  viscosity  After  and  s t a i n e d as  such v e r t e b r a e irregularities  The  first  in  or  48  about or  mounted  t o the and  and  in a  water  of e i t h e r treatments  an  Ostwald  experienced similar  or  25C)  25C  and  0.011  methylcellulose  experimental  temperature h before  in anaesthetic,  preserved  numbered v i a l s , were  vertebra Fish  with  made was  of  centra complex;  vertebral  A b d o m i n a l and  l e n g t h was  80%  in  cleared  often  other  use.  and  b a s i s of haemal s p i n e  whose haemal s p i n e  was  three  water),  ( i n 15C  a  whether  f a s t e d f o r 8-24  last  the  15  methylcellulose with  (15  (in  from a n a l y s e s .  were d i s t i n g u i s h e d on  64  some f r y were a l s o  0.1%  Counts  one.  at  summary, p e r f o r m a n c e  poise  above.  were c o u n t e d a s  vertebra  exception  0.5C  solution  In  in individually  The  immersed  measured  0.009 p o i s e  8 h,  were o m i t t e d  of  treatments  0.021  urostyle.  1985,  cine-film  1984,  this  f r y were k i l l e d  described  the  Temperature  In  msec.  were a c c l i m a t e d least  mm  p e r f o r m a n c e was  temperature  formalin  the  32  water)  filming,  buffered  vertebrae  two  for at  10%  excluding  was  1985.  25C.  msec d u r a t i o n ;  stimulus  and  a mirror  usually within  poise,  viscometer). of  16  1984  (with  through  solution  0.021  8V/cm  a r e n a was  in  or  viscous  in  t e m p e r a t u r e v a r i e d between  filming  15C  of  on  temperatures  r e f e r r e d to as  at  angle,  the  field;  filmed  water  24.5C i n 1984,  be  stimulus  degree  frames/sec.  14.5  msec  Swimming  a  electric  caudal length.  or more of  59 t h e maximum s p i n e designated to  the  length  first  i n the  caudal  t h e p o s t e r i o r edge of  measured  from the  Film distance 3 frame The  intervals  swimming  interval to  The  be  f o r response q u a l i t y  Three  criteria  during  before  bursts.  problem  responses to the  in  frequency problem  of was  this  problem  avoided  pulse  as a s t i m u l u s .  with  a  sustained  Failure  to respond  0.011  poise  attempted follows.  of  and  objectively  In e a c h s i z e responses  lower  class  at  25C  fish  was  (2)  was  by  responses w i t h i n each count  class  most  fish. of  higher  convulsion  most  frequent  increased.  failed  for  to  the This  electric respond stimulus.  i n the  15C,  to s i z e .  analysis  I as  I c a l c u l a t e d the good.  s e l e c t e d the given  to  i n 1983;  unrelated  as  known.  failure  frequent  responses  of a  of  t o t h i s more m i l d  was  I then  in  (3) a . c h a n g e i n  used  i n each experiment,  X,  or  were  using a brief  s u b j e c t i v e l y scored  percentage  15C,  this  a  the  fry size  apparently  select  at  indication  more o f t e n  swimming  greatest  because b u r s t s  swimming, and  1985  enthusiastically  treatment,  to  p e r c e n t a g e of slightly  burst  The  (0.0625 s) a t  bursts,  i n c r e a s e d as  However,  was  swimming were s u b j e c t i v e l y  factor  and  measured  vertebra.  frame.  extreme s t i m u l u s  i n 1984  was  length  v e r t e b r a l counts  of  first  caudal  duration  of  or a f t e r  depth during  basals  c a l c u l a t e d f o r each  (1) an  a sustained burst The  was used  were c o n s i d e r e d :  or p a r a l y s i s b e f o r e ,  by  intervals  bursts  anal  Caudal  first  shorter  recorded  the  T o t a l l e n g t h was  frame  25C,  of  plate.  the  was  of  scored  with  of  (0.047 s) a t  tended  respond  hypural  i n 4 frame  time  temperature.  the  were a n a l y s e d  travelled  shorter  vertebra.  a n t e r i o r end  records  vicinity  size  Using  a  fastest  X% of  class.  The  60 percentages used (1) lengths  were:  15C, 1983:  70% f o r t h e l e n g t h c l a s s 7.4-7.8 mm,  o f 7.8-8.3 mm,  55% f o r l e n g t h s  l e n g t h c l a s s e s 9.0-9.8 a n d 9.8-11.4  o f 8.3-9.0 mm,  15C, 1984:  70% f o r a l l l e n g t h c l a s s e s ;  (3)  15C, 1985:  60% f o r a l l l e n g t h c l a s s e s ;  (4)  25C, 1984:  80% f o r a l l l e n g t h c l a s s e s ;  (5)  15C, 0.1% m e t h y l c e l l u l o s e :  basis  were of  examined  subjective scores  procedures results  also  revealed  obtained  using  and,  80% f o r a l l l e n g t h c l a s s e s .  using  responses  selected  of response q u a l i t y .  t h e same p a t t e r n the  a n d 40% f o r  mm;  (2)  Results  60% f o r  in results,  objective  on  the  Both s e l e c t i o n so  only  those  procedure are described  here. In most a n a l y s e s classes. (1  0.0816667 mm). 91-95,  classes will mm,  below, f i s h  L e n g t h c l a s s e s were d e f i n e d  unit=  81-90,  described  96-101,  102-110,  Effects  9.0-9.8 mm,  of v e r t e b r a l  were:  111-120, a n d 121 o r more.  These  6.6-7.4 mm,  count  on  swimming  by  two-way  regression 1981).  analyses.  7.4-7.8 mm,  7.8-8.3  a n d >9.8mm.  between l e n g t h and t h e e f f e c t  or  usually  units  used  interactions one-  in length  i n o c u l a r micrometer  The l e n g t h c l a s s e s  be r e f e r r e d t o a s :  8.3-9.0 mm,  a r e grouped  analyses ANOVA  of was  Homogeneity of v a r i a n c e s  performance,  o f c o u n t , were  variance computed  among g r o u p s  (ANOVA),  and  tested  and  by  using  BMDP7D  (Dixon  was  tested  using  61 Levene's  test  significantly count the  at sizes  7.4-7.8 mm  these  two  statistic  count  and  among g r o u p s over  equality  using  treatment,  Variances  two t e s t s :  BMDP1R,  was  tested  The  third  length class  1974b).  and  effect in  methylcellulose.  In  t h e Welch  lines  were  of slopes  tested  using  of regressions of  slope  a s d e s c r i b e d by S o k a l interaction  and count c l a s s  of  Regression  equality  order  differed  (1) t h e e f f e c t  o f means was t e s t e d u s i n g  Forsythe  The s i g n i f i c a n c e  p.503-505).  i n only  1974a).  l e n g t h c l a s s a t 15C i n 0.1%  (Brown a n d  ratio  Forsythe  9.8 mm a t 15C i n 1983, a n d (2) t h i s  cases,  calculated BMDP1V.  (Brown  on  vertebral  and Rohlf  between  (1981,  viscosity  was t e s t e d u s i n g  BMDP4V.  Results Abdominal and c a u d a l  vertebrae  1.  P e r f o r m a n c e a t 15C  The  same p a t t e r n  1983 (Fig.  and  1984 among f i s h  7).  vertebrae,  (7.8-8.3 sizes  Within  in  o f 7.4-9.0 mm number  but  to caudal  vertebrae.  on  the  ratio  an i n t e r m e d i a t e mm),  and  count  of abdominal  among f i s h  vertebrae)  (8.3-9.0 mm).  vertebral  f i l m e d a t 15C a t l e n g t h s  both  absolute  (abdominal/caudal with  seen  P e r f o r m a n c e d e p e n d e d n o t on t h e  P e r f o r m a n c e was b e s t  those  i n swimming p e r f o r m a n c e was  with  at small  ratio  among t h o s e This  ratio  a high  (0.78) with  interaction  p e r f o r m a n c e was s i g n i f i c a n t  of  according  sizes at  between  of  0.82  AV/CV  (7.4-7.8 mm),  among  intermediate  sizes  a low r a t i o  was s i g n i f i c a n t  length c l a s s e s , the e f f e c t  ratio  of  (0.72) a t l a r g e  l e n g t h and  i n both  vertebral  years count  optimum  (Table 19). ratio  on  t o ANOVA a t s m a l l a n d l a r g e  Figure  7. B u r s t  swimming p e r f o r m a n c e a t 15C o f s t i c k l e b a c k  fry  6.6-9.0 mm  are  g r o u p e d by l e n g t h  to caudal length  i n length  vertebrae  i n 1983 (A) and 1984 ( B ) .  a n d by t h e r a t i o  (AV/CV),  of abdominal  a n d p l o t t e d a t t h e mean  i n e a c h g r o u p . Symbol a r e a s a r e p r o p o r t i o n a l  t o sample  sizes.  Fry  63 22 r  A  .  o  1983 I5°C  ©  •  20  • o  to  in  18  C\J CD O O*  •  -  ©  -  E E  SAMPLE SIZE O  10  O  20  <  1  16  5  O  o  -  o  40 i  >— o  2 2  B  3  o  1984  >  I5°C 20 -  X  < CV  AV/CV  14  16  0.88  14  17  0.82  © 14  18  0.78  3  13  17  0.76  O  13  18  0.72  •  18  •  o  16  AV  i 7.0  8.0 LENGTH  9.0 (mm)  Table 19. Significance of effects of vertebral count class on burst swimming performance of stickleback fry within length classes at 15C. Vertebral count classes are based on the ratio of abdominal to caudal vertebrae. To avoid small sample sizes, f i s h with ratios above 0.82 are omitted, and those with intermediate ratios of 0.7G and 0.78 grouped together. Probabilities are for the effect of count class In one- or two-way analyses of variance. Variances are homogeneous among groups 1n a l l comparisons. The maximum and minimum sample sizes are given in parentheses for each comparison. Data are shown In F1g. 7. Length class Year 1983 1984 Both  *  6.6-7.4  — 0.095 (10 - 31)  --  7.4-7.8 0..098 (6 - 24) 0.020 (10 - 40) 0.003  (mm)  Interaction Count x Length  7.8-8.3  8.3-9.0  0..62 (5 -• 15)  0 . 13 (7 •- 24)  0 .042 (5 •- 24)  0.27 (17 - 45)  0..017 (28 - 43)  0.,001 ( 10 - 45)  0.23  0.,006  65 sizes  i n 1984,  but  not  small,  Table  effects  of v e r t e b r a l count  and  large  19).  i n 1983  sizes  count  ratio  Combining  relationship  was  large  i t was  size,  19).  t o show a  between  both  ratio  (Table  performance tended  (when sample  At  and  and  negative  these  0.82.  s m a l l and  At  the  at  large to  be  sizes,  size,  years;  i n both  small  vertebral  small  i n both  significant  to  two-way a n a l y s i s ,  relationship  significant and  in a  tended  were h i g h l y s i g n i f i c a n t  linear  0.72  positive  years  sizes  this  at  years  the  (Table  20) .  Regressions vertebral differ In  of  count  classes  significantly  both  years,  decreased  between  on  vertebral  not  i n 1983  (1,1)  The  0.82  1983  ratio  0.72. was  This  among  fish  with  (Fig.  7B).  Fish  best,  but  21.  At  slopes  c l a s s e s i n both  years.  linear  significant  within  15C,  vertebral  however, d e g r e e s of  seen  to these  as  length  count  ratio  r e g r e s s i o n of  i n 1984  slope  (p<0.025),  freedom  were  but  minimal  calculation).  trend  a  at  sizes at  high  with  i n 1984  for lengths  between l e n g t h s  smaller  effects  significant  increased  and  on  shown i n T a b l e  a v a i l a b l e only  extend  not  slopes  count  Results are  are  performance  among v e r t e b r a l c o u n t  (p>0.25;  i n the  mm.  swimming  an  15C;  of  v e r t e b r a l count intermediate  sizes  under  and  9.0  mm  p e r f o r m a n c e was ratio  ratio  of v e r t e b r a l count these  7.4  less  7.4  appeared  ratio mm  of  on  than  7.4  did  not  not  0.82 to  best  or  perform  performance  (Table  19).  0.88  were  Table 20. Regressions of swimming performance of stickleback fry on the ratio of abdominal to caudal vertebrae (VR) and total length (TL), within length classes at 15C. Only ratios between 0.82 and 0.72 inclusive are included. Abbreviations are b (partial regression c o e f f i c i e n t ) , n (sample size) and P(b) (probability that the coefficient Is zero). Length class (mm) Year  Varlable  1983  6.6-7.4 n  ---  VR  b P(b)  TL  b P(b)  —  n  50  1984  7.4-7.8  7.8-8.3  8.3-9.0  38  32  47  15.5628 0.032  -4.5185 0.53  -13.4940 0.038  -0.6021 0.81  - 1 .6979 0.39  61  87  1.0022 0.33 104  VR  b P(b)  0.3896 0.92  12.9016 0.006  -2.3170 0.50  -12 . 1149 0.0007  TL  b P(b)  1 .8036 0.019  2.0705 0. 16  0.2000 0.83  2.0114 0.003  Table 21. Coefficients of regressions of swimming performance of stickleback f r y on length, within vertebral count classes VR. VR Is the r a t i o of abdominal to caudal vertebrae. Regressions are over the length interval 6.9 - 9.0 mm in the 25C treatment, and 7.4 - 9.0 in the 15C treatments. Abbrevatlons are MC, 0.1% methylcellulose; P(b), probability that slope Is zero; P(equal b), probability that slopes are equal among vertebral count classes; n, sample size. -  Treatment  VR  n  Intercept  slope  15C 1983  0.82 0. 78 0.72  63 36 18  7 .4261 5 . 1687 -14 .6921  1.4271 1.7478 4 . 1631  0 .0008 0 .0027 0 .0003  0.014  15C 1984  0.88 0.82 0. 78 0.76 0.72  14 128 26 43 55  0 .6901 12 .3298 10 .5446 0..7743 -4 . .6274  2 .2721 0 .8845 1,. 1402 2 .3191 2 .9851  O .018 0 .0027 0 . 10 <0 .0001 <0 .0001  0.001  1 .9724 . 9. 1220 5..7740 -4. 0622  2..2709 1 .3815 . 1 .8084 . 3.,0621  • 0,.0010 <0..0001 0..022 ,0001  0.086  -12. 1075 -7 .9750 5.0943 -6. 7205  3.7128 3.2144 1 6003 . 3.0609  <0. 0001 0.035 <0. 0001  25C  0.88 0.82 0..76-0.78 0.72  34 183 30 47  15C MC  0. 88-0.94 0.82 O. 76-0.78 0. 72  26 1 10 26 52  P(b)  <O. o.OOOI  P(equal  0.097  68 Swimming p e r f o r m a n c e was m e a s u r e d a t 15C a t l e n g t h s mm  in  three  years  classes  with  respect  lengths  of  9.0-9.8  appeared  to perform  equally  well  this  mm) a  ratio,  i n both ratio  1983,  while  among  the  optimum i.e.  between among  performance  be  or  Nor was  to sizes  similar  poorly i n a l l  significant years i n  interaction  between  at either  unrelated  9.0 a n d 11.5  large sizes  with  over  significant  i s apparently  fish  among  was  grouping  the  (8.3-9.0  differences in  p=0.28 a t l e n g t h s  between  vertebral  relatively  classes  years  o f 0.78  to perform  o f 9.8-11.5 mm,  None o f t h e s e  of count c l a s s  these  smaller  i n 1985.  o f 9.0-9.8 mm,  at  ratio  At  i n 1985, p e r f o r m a n c e i n  to perform  count  years.  ratios  to  a t 15C a t l e n g t h s  ratio  of  size  9.8-11.5  to v e r t e b r a l mm  ( o r , the  i s n o t among t h o s e  tested,  0.72 and 0.88 AV/CV).  P e r f o r m a n c e a t 25C  Effects between  other  appeared  within  effect  n o t between  2.  with  However,  appeared  of v a r i a n c e .  Swimming ratio  an i n t e r m e d i a t e  At l e n g t h s  vertebral  either  among  t o be i n v e r s e l y r e l a t e d  years.  classes  (p=0.l9 a t l e n g t h s  count  with  9.0  of v e r t e b r a l count  differed  p o o r l y and t h o s e  performance  two-way a n a l y s e s  mm).  fish  appeared  count  and  mm,  0.78 a g a i n  (p=0.10-0.63),  year  t o performance  previous  performance  The r a n k i n g  a s h a d been s e e n a t s l i g h t l y  of  vertebral  8).  i n 1983 a n d 1984.  length class  count  (Fig.  over  of v e r t e b r a l count  lengths lengths fish  intermediate  with  of  6.9  and 9.0 mm  o f 7.4 and 9.0 mm a high  ratio  ratio  ratio  on  a t 25C r e s e m b l e d  a t 15C.  at small  a t an i n t e r m e d i a t e  swimming  Performance  sizes, size,  performance those  seen  was  best  among t h o s e  w i t h an  a n d among t h o s e  with  69  Figure  8.  fry  9.0  and  1985  Fig.  B u r s t swimming p e r f o r m a n c e -  11.5  mm  in length  i n 1983  ( C ) . Symbols and  sample  7 l e g e n d s , e x c e p t as  noted.  at  15C  (A),  sizes  of  stickleback  1984  (B)  a r e as i n  MAXIMUM ro  VELOCITY ro ro  O  (mm/0.0625 s ) ro CD  ro  -1—  cn co o co o OJ  o b  m z.  O  ^  CD  cn co o co  H X  o 3  b  o  cn co ° co o cn  O  o CO cn  m X o  m  Id  b  > CO CO >  _  s  _„  I  U m P  O OL  -  CO  m  3  71 a  low  ratio  at  large  sizes  w h i c h p e r f o r m a n c e was b e s t ratios  appeared  compared ratio  of  lengths be  among  between ratio  AV/CV  o f 6.9-7.4 mm  7.8-8.3 mm  fish  at  lengths  a t 25C.  fish  with  (p=0.05l), sizes  are  (Probabilities temperature 0.72  and  but  at  ratios  in  the  with  the  in  a l l but  the  E f f e c t s of v e r t e b r a l  s i z e s t e n d e d t o be s m a l l than  10,  sometimes  interaction  of v e r t e b r a l count 7.4-7.8  class  length classes ratios  was s e e n increased  at  ratio  on  any l e n g t h c l a s s  than  performance (p>0.20), b u t  b u t 0.82  5 within  as  (usually  a length  class).  length  same p a t t e r n 15C  (0.82,  t h e r a n g e 0.72-0.82 i n t h e 8.3-9.0 mm p=0.054).  of regressions  the  with  ratio  f  showed  class).  count  a t 25C (b=-12.1080  Slopes  At  over  length  (p>0.20, b u t  However, t h e r e g r e s s i o n o f p e r f o r m a n c e on v e r t e b r a l was s i g n i f i c a n t  mm  length  for a l l ratios  less  high  l e n g t h c l a s s 0.76-0.78) a s  count  a t 25C w i t h i n  a  o f 0.76-0.78 a t  This  smaller  smallest  a t 25C  a t 15C, b u t a t  length classes  a r e from two-way ANOVAs w i t h i n  were n o t s i g n i f i c a n t  less  fish  25C.  in  intermediate lengths  (1984 15C o r 25C) a n d v e r t e b r a l c o u n t  treatments).  sample  shorter  and t h e e f f e c t  i n other  small  or  performance appeared t o  intermediate  not  high  among  Similarly,  treatment  However, t h e s i z e s a t  o f 7.4-7.8 mm  a t 15C, b u t a t 7.4-7.8 mm  temperature  sample  with  to s l i g h t l y  on p e r f o r m a n c e was s i g n i f i c a n t  class  9).  P e r f o r m a n c e was b e s t  0.82  best  among  t o be s h i f t e d  t o 15C.  (Fig.  (Table  of  swimming  performance  among v e r t e b r a l c o u n t 21).  v e r t e b r a l count  25C, d i f f e r e n c e s i n s l o p e  At  ratio  both  on  c l a s s e s a t 25C a s  temperatures,  decreased  length  from  among v e r t e b r a l c o u n t  slopes  0.82 t o 0.72. classes  were  72  Figure fry  9. 6.9  a r e as  B u r s t swimming p e r f o r m a n c e - 9.0  mm  in length.  a t 25C  Symbols and  i n F i g . 7 l e g e n d s , e x c e p t as  of  stickleback  sample  noted.  sizes  73  IS  o b  22  O  • •  -  E JE >(-  25°C  20  o o  >  S A M P L E SIZES AND S Y M B O L S A S IN FIG. 7 EXCEPT:  •  8  Q  ON=70  X  <  9 i  i  7.0  AV/CV=0.76-0.78 1  i  8.0 LENGTH  (mm)  i  9.0  74 significant approached  over  this  significance  (p=0.086).  range  including  Differences  performed  best  at  of  small  r e s p e c t i v e l y ) were h i g h l y  ratios  10  each  o f t h e two  between two  for f i s h  in  slope  between  or  large  sizes  significant  effects  of  temperatures  are  temperatures, with  the  low  sizes,  ratio  In  intersect  with  were c a l c u l a t e d  between  the  intersect  3.  at  lines a t 7.85  15C  Overall  ratios  that  and  length are  0.72,  o f 0.72 and  shown  in  o r 0.82  at  differences  on p e r f o r m a n c e  this  regression  figure.  ratio at  15C,  At  superior  t h e two  (8.07-8.08 mm).  i s not a r e s u l t  ranges  over  of  both  large  regression  lines  at  25C,  Regression  7.4-9.0 mm  at  15C,  in intersection  point  this  the range  at  mm).  fish  at small  However, (7.85  the both  At  are superior  are  smaller size  at  a r e g r e a t e r among  ratio  the l e n g t h  calculated  change  7.4-9.0 mm  in  range.  a t 25C  also  mm.  Performance  i s shown  0.88  (0.82  ratios  However, t h e s h i f t  at  15C  Swimming p e r f o r m a n c e at  on  ratio in  high  low  a  over  a t 25C.  temperatures  Regression  seen  replications  intersect  6.9-9.0 mm  of  t h a n among t h o s e w i t h t h e h i g h r a t i o .  fish  both  the  similarities  count  this  a t t h e same l e n g t h  lines  lines  of  while those with the  sizes.  the  clearly  only  (p=0.0l5).  count  The  vertebral  slopes  temperatures,  and  with v e r t e b r a l  temperatures.  but  t h e more e x t r e m e r a t i o  R e g r e s s i o n s of swimming p e r f o r m a n c e Fig.  (p=0.053),  in F i g .  performance  was  i n 0.1%  i n an 11 not  0.1%  methylcellulose solution  of  methylcellulose  f o r l e n g t h s between 6.6 greatly  affected  by  and the  9.0  mm. high  75  Figure  10. R e g r e s s i o n s  stickleback 0.82 25C  f r y with v e r t e b r a l  AV/CV, a t 15C i n 1983 i n 1984  vertebral point axis  o f swimming  between i n each  count  ratios  t h e two panel.  on l e n g t h among o f 0.72  i n 1984  of e q u a l  i s g i v e n by lines  ratios  ( A ) , a t 15C  ( C ) . The p r o b a b i l i t y  count  performance  ( B ) , and a t  slopes  'p'. The  or  between  intersection  i s shown on t h e l e n g t h  76  0.72 p=0.004 0.82 CO  in  v _ C\J ^ CD J— o o o _l LU  °  E E  >  22"  1984 15 C  8.08 0.72 p<0.00l 0.82  20H B  18x <  24i  1984 25 C  8.07 -0.72 P=0.0I5 0.82  22 CO  O  20  d  E E  18 16  7.0  8.0 7.85  L E N G T H ( m m )  9.0  Figure  11.  6.6  - 9.0  Burst mm  in length  methylcellulose are  as  swimming p e r f o r m a n c e o f  at  15C.  i n an  0.1%  s o l u t i o n of  Symbols and  in F i g . 7 legends,  except  stickleback  as  sample noted.  sizes  78  20  METHYLCELLULOSE  #  •  I5°C  •  18  LU  >  16  S A M P L E SIZE AND S Y M B O L S A S IN FIG.9 EXCEPT  •  x <  14  1  7.0  1  LENGTH  -  ON  = 50  •  AV/CV=0B8-0.94  —  i  8.0  (mm)  1  i _  9.0  79 viscosity  of  performance in  water  this  in this at  solution. solution  15C. a  treatment;  below  in  Fig.  length  treatments.  Performances  0.72  AV/CV  length classes count  ratio  class  according  between  greatly  were s i m i l a r  length  and  their  inferior  performance  water  differed  (p=0.004, effects grouped  at large this  length  of count  third  ratio  Fig.  11)  Effects  and  of  the  between  interaction  count  r a t i o on (p=0.028).  performance of  small 11).  solution  at  sizes  viscosity  and  Comparing 15C, t h e  of v e r t e b r a l  count  treatments  i n t h e ANOVA  0.76-0.78, 0.82), viscosity  vertebral  the  (Fig.  effect  o f 0.82  any l e n g t h  the superior  sizes  previous  within a l l  7.4-9.0 mm  at  on  within  But  order i n t e r a c t i o n  (0.72,  the  solution  vertebral  viscous  and  15C  ratio  o r low r a t i o s  (0.76-0.78)  significantly  f o r the  in  reflects  ratios  or  between  mm.  of  1984  count and  viscous  over t h e range  performance  in  interaction ratio  effect  presumably  with intermediate  this  with high  9.0  the  80% o f  70% o f r e s p o n s e s a s shown  (p=0.16 - 0 . 9 8 ) .  the  in  were n o t s i g n i f i c a n t  was s i g n i f i c a n t  interaction  class  of vertebral  in this  between 6.6 a n d  t o ANOVA  a r e with the best  between  of f i s h  on p e r f o r m a n c e  performance  fish  count  7 B ) . However, t h e e f f e c t differed  This  and  class,  92% ( r a n g e 80-101%) o f t h a t  i s with the best  performance  or  averaged  (These comparisons  responses within that  W i t h i n a l e n g t h and count  testing  length class  (1984 15C:  water  (as  o r 0.1%  methylcellulose)).  Similar regressions classes  conclusions are  reached  of  on  (Table  performance  21).  The i n v e r s e  comparing  length  among  relationship  the  slopes  vertebral  between  slope  of  count and  80  vertebral between  count  0.72  and  Instead,  slopes  with  or  high  ratios.  ratio 0.82  seen  i s absent  in this  low  ratios,  Differences  previous  and in  low  are  those  intermediate  similarly  among  slope  are  treatments  for  i n the m e t h y l c e l l u l o s e  treatment  (p=0.097), b u t with  i n the  those  are  highly significant  not  among  fish or  fish  intermediate  significant  if  (0.76-0.78)  treatment.  high  with  ratios  are  with  overall  grouped other  as  ratios  (P=0.017).  In  summary, t h e  performance  differed  methylcellulose difficult effect  to  at  0.1%  15C.  assess.  i n the  for  a  0.1%  month  methylcellulose  was  significance  It  does  viscosity  appeared  to  shift  intermediate smaller  solution  poise)  large  shift  water  at  larger  than  from water  15C  would  those  changes  at  ratios  examined.  in viscosity  s m a l l changes normally  seen  t h a t the  i n 0.1%  term  exposure  differ  experienced  Fish  the  water). from  A 15C  with  in  25C  high to  15C  effects  effects  nature.  in  small to  or  slightly  viscosity  qualitatively  were  survival  (about  produced seen  m e t h y l c e l l u l o s e at  Alternatively, may  long  were s u p e r i o r in  toxic  greatly  m e t h y l c e l l u l o s e at so  to a  not  fish  increase  direction,  be  due  is  was  poise)  which  0.1%  difference  solution; in  swimming and  innocuous.  than  0.002  large  t o 0.1%  other  (Even  this  better  count  Perhaps the  i n the  or  sizes  this  seem t o be  i t .  on  water  of  relatively  water  ratio  performance of  (about  vertebral  sizes.  0.010  is  the  not  since  slightly  in  between  The  in  decrease  the  greatly  methylcellulose  reared  large  of v e r t e b r a l c o u n t  of m e t h y l c e l l u l o s e ,  diminished to  effect  of  a in  sizes such  from those  of  81 Body  Proportions  Effects swimming  performance  proportions  on  considered length  could  count  ratio  (p<0.000O  Variation  1984 f i s h ,  examining  of  the  VR  and  LR  correlation  linear  regression  regressions  (Table  among  performance  fish  regressions four and  approached  those  coefficients 22).  of  regression  coefficients  case,  those  one to and not  while case,  those LR.  on  Regressions  attributable  by  and  VR  8.3-9.0 Simple  of the simple  mm,  linear  (p<0.05) i n a l l i n o n l y one c a s e  were s i g n i f i c a n t  Partial  i n a l l b u t one  i n no c a s e s .  coefficients  multiple calculated  (p=0.063) i n o n l y one o t h e r .  signs of the p a r t i a l  Thus, e f f e c t s  in  were  1983 o r 1984.  on LR were s i g n i f i c a n t  on VR a n d t o t h o s e  compared  each  on LR were s i g n i f i c a n t  significance  i n VR among fish.  were  o f p e r f o r m a n c e on VR were s i g n i f i c a n t while  and  r e g r e s s i o n s o f p e r f o r m a n c e on e a c h  f i l m e d a t 15C i n e i t h e r  cases,  between  i n 1983  1983  s e p a r a t e l y w i t h i n t h e l e n g t h c l a s s e s 7.4-7.8 mm among  I  (LR) was h i g h l y  f i l m e d a t 15C b o t h  on  body  (where p r e c a u d a l  length ratio  variation  of  on  possibility,  ratio  The  vertebrae  effects  this  length  fish  25% o f t h i s  simple  the p a r t i a l  linear  from  test  length).  caudal  i n LR e x p l a i n e d 57% o f t h e v a r i a t i o n  but only  Effects  To  (VR) a n d t h i s among  to  result  precaudal/caudal  i s t o t a l minus c a u d a l  significant  and  of abdominal  performance.  the  vertebral  1984.  of the r a t i o  In a l l but  on LR were  coefficients  opposite  on b o t h  VR  o f VR on swimming p e r f o r m a n c e a r e c l e a r l y  to effects  o f LR on p e r f o r m a n c e .  Table 22. Regressions of swimming performance on the ratio of abdominal to caudal vertebrae (VR), on the precaudal/caudal length ratio (LR), and on VR, LR and TL (total length), within small or large length classes at 15C. Only f i s h with VR between 0.72 and 0.82 inclusive are included. Abbreviations are as In Table 20.  Year  Independent variables  Length class Statistic  1983  7.4 - 7.8  (mm) 8.3 - 9.0  n  38  47  VR  b P(b)  15.417 0.031  -13.247 0.041  LR  b P(b)  1.157 0.81  -7.864 0.044  VR  b P(b)  17.075 0.032  -9.608 0.21  LR  b P(b)  -2.625 0.58  -4.384 0.34  TL  b P(b)  -0.685 0.79  0.824 0.43  n  61  VR.LR.TL  1984 VR  b P(b)  LR  VR.LR.TL  104  13.028 0.006  -10.488 0.004  b P(b)  6.184 0.063  -3.964 0.13  VR  b P(b)  15.003 0.032  -14.250 0.007  LR  b P(b)  -1.971 0.68  2.048 0.58  TL  b P(b)  2.180 O.15  1.960 0.004  83 Summary Swimming p e r f o r m a n c e d e p e n d e d not vertebrae, 15C,  but  on  the  p e r f o r m a n c e was  AV/CV  at  ratio  among  with  those  sizes  a  low  vertebral  count  performance at of  slightly  on  f r y with  mm),  (0.72) a t or  or  sizes  tested.  A  ratios  v e r t e b r a l count  ratio  on  performance d i f f e r e d  within  ratios  performed  equally  well  a l l l e n g t h c l a s s e s between 6.6  vertebral attributable performance.  count to  ratio an  effect  on  and  swimming of  not  and mm).  effect  was  of  that  superior  The  effect  g r e a t l y between  high  (0.82)  i n the  viscous  9.0  an  differ  except  temperature.  with  0.82  (8.3-9.0  25C,  this  (0.72)  higher  of with  similar  seen a t  intermediate  Fry  ratio  did  at  methylcellulose.  At  (7.8-8.3 mm),  sizes  0.1%  vertebrae.  those  smaller  water and  of  large sizes  p e r f o r m a n c e was high  sizes  larger  ratios  number  a high  among  intermediate  ratio  the  ratio  of  (7.4-7.8  smaller  among  absolute  of abdominal to c a u d a l  (0.78) a t  P e r f o r m a n c e a t even significantly  the  s u p e r i o r among f r y w i t h  small  intermediate  ratio  on  mm.  performance  precaudal/caudal  or  low  solution  Effects  of  were  not  length  on  84  Part  III.  Changes  in vertebral  count with  length  in  wild  stickleback f r y .  Material  and Methods  Stickleback from H o l d e n a canoe sites  f r y were c a p t u r e d by d i p n e t (25 x 17  Lake,  floating A1,  A3  B.C. near  and  site  B between J u n e  and  8  Collections shore  (Fig.  4 a n d 14, 1984.  x 12 m i n a r e a .  collection,  10% b u f f e r e d  Part  I.  abdominal II.  sites,  F r y were c o l l e c t e d  Sites  were between  20 m, and s i t e  from from  11, 1984, a n d f r o m 5 x  S i t e s A3 and A4 were a d j o i n i n g ;  Centra  5  site  B f r o m A1 by  vertebra  such  equivocal  i n about  was  6.1-6.6 mm  counted,  counts  total  was  from  m A1  about  lengths  due  to  measured  as d e s c r i b e d  neural as  to obtain  one.  other  0.5% o f f i s h  6.7-7.2 mm  among to  counts  from  counts  and  i n Part  and/or  haemal  Counts  were  irregularities; Vertebral  12%  of  in length,  fish collected  obtain  preserved  as d e s c r i b e d i n  were e x c l u d e d f r o m a n a l y s e s .  sufficient B.  two  counted  fish  in length,  site  bore  were  insufficient  in length,  Development  often  1.5% o f  7.3-7.7 mm  collected  and c l e a r e d and s t a i n e d  vertebrae  equivocal  development  fish  were  in anaesthetic,  and c a u d a l v e r t e b r a e d i s t i n g u i s h e d  The l a s t  these  f r y were k i l l e d  formalin,  arches;  of  gape)  m. After  in  12).  A4 between May 7 a n d June  was s e p a r a t e d from A3 by a b o u t 200  were made a t f o u r  cm  a n d 0.1%  from A from  fish  sites.  a l l fish  85  Figure  12. Map  of Holden  Lake,  B.C.,  showing  sampling  sites.  HEMER CR  500 m  87  F r y were g r o u p e d abdominal  to  for analysis  caudal  vertebrae  distinguished:  (1) 0.82 AV/CV  AV/CV  (14/18,  13/17),  ratios  (mostly  tests,  calculated  (3)  (14  using  to  (AV/CV).  Four  AV/  0.72  0.88 o r m o r e ) .  according  17  AV/CV  CV),  (Dixon  ratio  groups (2)  (13/18),  Probabilities  BMDP4F  the  are  of were  0.78-0.76  a n d (4) o t h e r  from  chi-square  1981).  Results Differences among  sites  Frequencies among  A1, A3 a n d A4  and s i t e  analysed  fry  13, with  those  B (p=0.0085).  recruits  o f f r y under  (p=0.l8),  were  7.4 mm  classes  did  but d i d d i f f e r  Hence,  count  a high  frequency,  ratio  fish  tested  in length. not  differ  between  from s i t e s  these  A and B  are  o f f r y g r o u p e d by l e n g t h a r e shown i n  intermediate  As mean  r e v e r s e change in  from d i f f e r e n t  o f 0.82 AV/CV  a s mean l e n g t h  (p=0.020).  changes  ratios  pooling collections  with  length  counts  of  s e p a r a t e l y below.  Vertebral Fig.  comparing  counts  of the f o u r v e r t e b r a l count  sites  sites  by  in vertebral  ratios  of  i n c r e a s e d from  length  in  0.76-0.78 about  occurred  occurred  further  B, and  decreased  6.9  (p=0.024).  with  At s i t e  frequency,  i n c r e a s e d f u r t h e r t o about  i n frequency  frequency  increased  dates.  No  to  in  7.5  8.0 mm,  mm the  significant  increases in f r y  (p=0.80).  Among f r y c o l l e c t e d  from s i t e  frequency  occurred  (p=0.l3).  However, t h e same d e c r e a s e  the  ratio  high  between  A, no s i g n i f i c a n t  and  mean  increase  in  lengths  of  6.9  i n frequency frequency  of  changes and fish  of those  in  7.5  mm  with  with the  Figure  13. F r e q u e n c i e s o f v e r t e b r a l  stickleback based A.  f r y grouped  on t h e r a t i o  site  B.  length.  of abdominal  F r y c o l l e c t e d from  from  by  site  Symbols a s  count  A;  Count  classes classes  i n wi are  to caudal vertebrae. B.  Fry c o l l e c t e d  i n F i g . 14.  SAMPLE SIZE O 535 O 700  40  SAMPLE SIZE O 1 15  J  J  7  X  1  I  I  •  8 9 LENGTH (mm)  I  10  •  I  I  90 intermediate from  7.5  ratios  t o 8.0  frequency  was  mm  occurred  seen as  mean  (p=0.040).  with  even  length  Again,  further  no  increased  significant  increases  in  further  changes i n fry  length  (p=0.51>. These, c h a n g e s fry mm  with at  site  lengths  i n frequency  a high  ratio  of  B,  those  with  of  and about  w o u l d be  changes  frequency  in  reflect  changes  population length  fry  at  time,  time  differ site  A  period  of  14. the  intermediate recruits  A  and  frequencies  between  before  after  or  increase  mean l e n g t h s increase  7.5  A and  successive  correlation  initial  count  of  t o the  grouped as  i n the  tend  or a f t e r  day  23.  of  8.0  mm  at  those  significant  f r y with  at  between e a r l y and  A  the and  recruits are  i n the  site of  shown  figure,  the  most common sampling of  the  differ  between  Differences  i n count  collected  at  (p=0.006).  i s not late  (p=0.46) o r  frequencies to  did  B  extended  intermediate  site  of  sites  shown  the  do  are  to  classes in recruits  classes  date  the  between c o u n t  two  However,  s a m p l e s g r o u p e d as  Alternate  recruits  frequency  14A).  at  b o t h ) of  frequencies  in length)  trend  not  B.  7.3-7.7  l e n g t h c l a s s e s might  an  before  i n frequency  0.76-0.78  counts  (Fig.  and  of  among d a y s , e i t h e r  in frequency of  ratios  sites  (0.82) i s s e e n o v e r  this  about  vertebral  'other'  collected  both  favouring  of  (though probably  With data  No  ratio  site  at  four v e r t e b r a l count  (p=0.l8).  at  one  mm  significantly  count  mm  selection  lengths  intermediate  Vertebral 7.4  in Fig.  vertebral  the  or  reflect  AV/CV a t  between  the  under  frequencies not  in  that  in recruits.  (i.e. over  over  0.82  7.8-8.3  explanations  could  ratios  explained  recruits.  site  A  However, between by  this  The  two  91  Figure less  14. than  Frequencies 7.4  mm  Count c l a s s e s a r e vertebrae  v e r t e b r a l count  in length, the  for site  B  (panel  g r o u p e d by  ratio  (AV/CV). Samples  g i v e minimum sample 35  of  in fry  collection  date.  of  abdominal to  from  successive  days grouped  for site  (panel  s i z e s of B).  classes  50  A  caudal  A)  and  to  92  A 60  4 0  >o  20  LU ZD  O LU  CC  Li_  7  May  h-  ~ZL  LU O DT LU CL  7  June  L E G E N D B  S A M P L E  60  14  SIZE  o  35  o  5 0 - 9 0  O  110-175  A V / C V 40  •  0.82  ©  0.76-0.78  o  0.72  •  O T H E R  20  May  7  10  20 D A Y  30  [40 J u n e 14  93  length late  classes  i n the  classes after fry in  contained  sampling  7.3-7.7  day  25  into  these  8.0  mm  alone  (p=0.086 a n d  count  early  0.21,  and  Most  7.8  mm.  Thus,  and  recruitment  However, no  i s used to a l l o w  and  late  are  number and  vertebral  correlation an  i.e.  is  When c h a n g e s are  site  be  in  an  23),  initial can  recruited  7.5  though  subsample  A.  and  ratio  to these  similarly below  of a c o r r e l a t i o n  between  count  the  two 6.9  vertebral  smallest  and  count  7.5  mm.  occurred  A correlation  between v e r t e b r a l  be  in  expected  to  be  1981).  0.78  are  AV/CV  between v e r t e b r a l c o u n t  counteract  rather  contribute  length  to the  a  (i.e., 6.9  and  T h u s , an  changes  of f r y  32  these  in  the  positive  frequency  seen between  and  of  determining  I f so,  p r e d i c t e d changes.  correlation  view  involved in  i n c r e a s e i n the  of  i n v e r t e b r a l count  be  lengths  Arnason an  correlation  at  p r e d i c t e d between mean l e n g t h s o f  than  of  same c h a n g e s  neither  s e e n between  thought  ( L i n d s e y and  opposite  growth  (Table  recruits  difference in  i s expected,  vertebrae)  in  l e n g t h might  intermediate  collected  i n c r e a s e s from  between .mean l e n g t h s o f  processes  number  invoking  length  lengths at  developmental  the  length  respectively).  length should  hatching  were  f o r the  collections  significant  fry collected  f r y i n the  Furthermore,  greatest effect  significant  between t h e s e  % of  respectively,  f r y were a p p a r e n t l y  the  classes,  47.5  s e e n as mean f r y l e n g t h  i n frequency  discredited.  they  date  and  mm,  alternate explanation  between  with  are  i n both  changes  length  (47.6  length classes)).  these  The  same p r o p o r t i o n o f  7.8-8.3  later  v e r t e b r a l count  to  period  and  (the  the  total 7.5  mm.  lengths, initial  recruits  may  in vertebral  Table 23. Vertebral count class frequencies (%) of sticklebacks 8.3 mm or less In length, collected from s i t e A between May 7 and 31, or between June 4 and 11, 1984. Vertebral count classes based on the ratio of abdominal to caudal vertebrae. Mean 1ength (mm)  0.82  6.1-7. 2 7.3-7.7 7.8-8. 3  6.86 7.46 7.99  58.3 59.9 55.2  June 4-11 6.1-7. 2 7.3-7.7 7.8-8. 3  6.94 7.46 8.00  60.5 63. 1 55.0  Date May 7-31  Length cl ass (mm)  Vertebral count class (%) 0.76-0.78  Sample s ize  0.72  Other  13.0 14.8 21.2  10.0 7.4 4.9  18.6 17.9 18.7  408 364 364  16.7 19.6 24.3  10.5 7.6 9. 1  12.2 9.7 11.6  294 331 329  95 count  observed  between mean l e n g t h s o f 6.9  F r y were c o l l e c t e d were  grouped  Effects any  over  o f any  from  B  confounded  by  restricting can  by  one  collection  dates.  of  and this  length  of t h e s e These  to  from  0.5  respectively  mm  assumption  may  mm/d.  over  be v a l i d  first  site  classes.  time.  only a brief  of  However, period,  f r y a r e more l i k e l y can  c o h o r t of  be  so to  eliminated  fry.  Such  an  B i f i t i s assumed t h a t f r y  the  next  between  in length  growth r a t e s  successive  distributions  of  f r y . were by  three length classes,  for collections  from  and  time, or  S u c c e s s i v e mean l e n g t h s d i f f e r  f o r the  f r y were c o l l e c t e d  period,  among l e n g t h  problems  the peaks  fry in successive collections, 0.2  over  for site  class  Judging  about  extended  grouping over  to a s i n g l e  attempted  mm.  l e n g t h among n e w l y h a t c h e d f r y ,  collected  such e f f e c t s .  least  of  by  comparisons  grow from  7.5  i n the counts of r e c r u i t s  were  be  A o v e r an  comparisons  among l e n g t h c l a s s e s  be  analysis  in  cancelled  site  comparisons  site  between c o u n t  w o u l d be m o s t l y fry  time  change  correlation  from  and  B on d a y s  3d a p a r t . 36 a n d  0.6 so  at and this  Large  numbers  39 o n l y .  Counts  of  fry  i n one  length class  on day  36 a r e c o m p a r e d w i t h t h o s e o f  fry  i n the next  length class  on day  39  changes in  in  f r e q u e n c y a r e seen  the comparisons  levels  of  the changes selection  grouped  over  a l l  are reduced.  in vertebral  count count  Fig.  15.  i n these comparisons  significance  for vertebral  in  collection Thus,  The as were  dates,  length  classes.  seen  though  i t seems l i k e l y  seen among l e n g t h c l a s s e s i n those  same  that  reflect  96  Figure two  15. V e r t e b r a l c o u n t - r a t i o s 'cohorts'  class as  at site  of s t i c k l e b a c k f r y i n  B, c o m p a r i n g  counts  in length  i on day 36 and l e n g t h c l a s s i+1 on day 39. Symbols  i n F i g . 14. A. i= 6.1-7.2 mm;  B. i = 7.3-7.7  mm.  97  E  CT) e 1  ' r LO o  > o o ro < . II * — '  CM r -  /  o  /  L O  o o  / /  O X CJ  /  /  4  E rc oo E ^ r^o  CL  /  <  i  "  Q K ) Z  CD  I CD £ —  r o CD >_ ^ <r " 1  Q f O  ^  CD  _  oo  o d  II  Q.  ^  <  Q  O  00  o  CD  A3N3n03cdd  O  O CO  !N33cJ3d  c ^  L O  i II  —. Z CD —  98 Total are  shown  given  site  in  seen  significant with  31 v e r t e b r a e  change  further  to  8  significance frequency  with  the  occur  low  8  these  of f r y with  mm.  with  i n frequency  occurred second  i n frequency  of those  of  with  32,  A,  the  As a t s i t e  change  increased  only  approached  did significant  i n c r e a s e d above 8  i n the r e l a t i v e  between  hand, t h e most  a s mean l e n g t h  At n e i t h e r s i t e  a s mean l e n g t h  31, a s mean  occurred  On t h e o t h e r  from 6.9 t o 7.5 mm.  this  change seen a t  32 v e r t e b r a e , a n d  B was an i n c r e a s e  selection  changes  mm.  frequencies  favouring a high  ratio  of v e r t e b r a l  ratios  o f 0.76-0.78 AV/CV a n d a h i g h  larger sizes  between  count  o f 7.8-8.3 mm.  and  over  length  in relative  persist  when c o l l e c t i o n s  length  and  recruitment  frequency  or  size  total  or  will  main  an  of  initial c a n n o t be  causes  These  are pooled not  and  of changes i n  of  length.  dates  AV/CV  count  recruits,  not the  with  from d i f f e r e n t date  in  0.82  o f 7.3-7.7 mm,  Effects  time,  e l i m i n a t e d , but a r e p r o b a b l y  changes  sizes  of  c o u n t o f 31 a t s m a l l  v e r t e b r a l counts of r e c r u i t s  completely  significant  total  at s l i g h t l y  correlation  of abdominal t o caudal  l e n g t h among w i l d s t i c k l e b a c k f r y i n H o l d e n L a k e a r e  with  intermediate 32  B.  summary, c h a n g e s  consistent a  at site  expected  change  i n frequencies but  a r e those  Most o f t h i s  and d e c r e a s e  mm,  classes  of those  and  increased  reverse  counts  7.5  length  i n frequency  c h a n g e seen a t s i t e  as mean l e n g t h  In  The o n l y  i n frequency  decrease  of  i n frequency  f o r the r a t i o  13.  i n c r e a s e d t o 8 mm. lengths  and  Changes  selection  in Fig.  corresponding  mean  in  16.  A was an i n c r e a s e  length  fry  Fig  the apparent  vertebrae  a  v e r t e b r a l counts of f r y i n the v a r i o u s  be  of  changes (so that strongly  99  Figure fry  16.  Percent  g r o u p e d by  frequencies  length  O n l y c o u n t s between shown.  30  at  site  and  32  of A  total (panel  (>98%  vertebral A)  or  B  counts, (panel  of a l l c o u n t s )  are  in B).  K - p = 0.006-H  p = 0.39 31  p=O.I7 p=0.023  i  J  P = 0  -  0  2  0  - t  p=0.65  p=0.0035 H  H  p=0.076  20h B  8 9 LENGTH (mm)  10  101  confounded), and when fry in one length class of a given collection are compared with those in the next length class of the next collection.  1 02  Part  IV.  Predation experiments  Material Ripe Holden  and  peamouth chub M y l o c h e i l u s c a u r i n u s were c o l l e c t e d  crosses  respectively  single  male  incubated  and  28  and  made  May in  female).  in separate  20  11, the  L tanks  of  natural plankton.  and  development  among  two  7 (PM1)  or  (each  27  (PM8)  between  After  hatching,  fry  with o c c a s i o n a l supplements  C o n d i t i o n s were c r o w d e d ,  slow compared  a  e a c h s e t o f c r o s s e s were  14C.  twice d a i l y ,  and  tanks  exposed  been e a t e n .  to those  (15 or  or a b s e n t ) .  same  as  those  with  sticklebacks, in  of  f r y i n the  I n a l l but which  and wild  respect  to  tanks,  sunfish  until  the  50-60% of  experiments,  +/-  1C)  Experimental  except  that  experiments.  and  two  design above  distributed and  or  those  in  smallmouth  initial  number  had  f r y were e x p o s e d a t  two  cover and  treatments  procedure  f o r the  predators Details  were  1983  were  (cover the  experiments  not  removed  of e a c h e x p e r i m e n t  are  24.  experiment  vertebrae  Experiments  were  t o p r e d a t i o n by  five  25C,  fry  experimental  described in detail  these  i n Table  hatching,  four  dolomieui  In e a c h of  temperatures  overnight  d after  and  Micropterus  present  56  control  experimental  given  and  from  below). Between 22  bass  from  at  nauplii  nematodes and  1983,  laboratory  Embryos  were f e d A r t e m i a  (see  chub.  Methods  L a k e on A p r i l  growth  w i t h peamouth  are  5,  sufficiently  were done a t t h e s e vertebral  some f r y were  below  formed  small sizes  number c o u l d r e f l e c t  to  since  the be  size  countable.  selection  selection  at  with  f o r myomere  Table 24. D e s c r i p t i o n of p r e d a t i o n experiments u s i n g peamouth chub as prey. Predators are s u n f i s h (S) or bass (B) Predator-hours (pred-h) a r e c a l c u l a t e d u s i n g l i g h t e d periods only. Predators  Exp.  Par.  Temp. Tmt. (C) Cover  PM8  Con  15 25  Exp  PM1  PM8  Durat ion h  Pred-h  N N  28 27  0 0  15 15 25 25  Y N Y N  26 22 23 24  203 154 140 148  Con  15 25  N N  78 54  0 0  Exp  15 15 25 25  Y N Y N  98 96 52 54  2208 2082 830 868  Con  15 25  N N  49 29  0 0  Exp  15 15 25 25  Y N Y N  48 46 28 30  614 589 192 214  Type  -  -  S  s s s _  Length  (mm)  Mean  SD  -  31.2 30.4 29.4 30.0 _  2.6 2. 1 2.4 2.6 _  -  -  -  B B B B  14.8 14.5 16.7 16.6  1 .7 2. 1 2.3 2. 1  _  -  -  -  B B B B  22.8 21.8 23.8 23.3  4.3 4.0 4.8 5.5  % eaten 0 0 55 52 61 66 0 0 48 51 64 64 0 0 61 68 60 57  , NO. eaten per pred-h  No. surv i v i ng Reared  Rear i ng mortal 1ty (%)  60 49  155 161  1 .35 1 .. 7.1 2..34 2,.42  70 62 37 54  _  -  -  0.. 12 0.. 13 0. 40 0. 38 _  0. 50 0. 58 1 . 56 1 .33  Length (mm) of preserved survivors Mean  SD  5 .8 23 .0  8 .84 9..02  0 .37 0..40  155 186 168 131  10 . 3 37 . 1 19 .6 12 . 2  8 .95 8 .86 9 .05 9 .06  0..32 0. 30 0. 29 0. 33  53 53  149 149  20 .8 0 .0  9..89 0. 38 10.. 13 0. 58  75 61 34 41  201 196 153 146  1 .0 . 17 .9 . 0..0 0 O  10..03 9..85 10. 23 10.. 18  58 48  142 152  7.,0 5., 3  52 45 57 50  142 1 16 143 163  3..5 15..5 1 .. 4 7 .0 .  Pres .  0..49 0. 55 0. 57 0. 59  10.. 14 0. 53 10..38 0. 47 10. 42 10..67 10. 56 10. 47 contd.  0. 48 0. 48 0. 46 0.41  Table 24. contd. Predators  Exp.  Temp. Par. Tmt. (C) Cover PM1  PM8  Duration h  Length (mm)  Pred-h  Type  Con  15 25  N N  73 49  0 0  -  Exp  15 15 25 25  Y N Y N  70 74 47 48  1599 1751 610 623  B B B B  Con  15 25  N N  31 27  0 0  Exp  15 15 25 25  Y N Y N  30 30 26 26  377 359 150 152  Mean  SD  0 0 17,.8 17,.5 19,.0 19,.0  2,.8 2..0 0..8 2..8  _  49 49 55 57 0 0  B B B B  % eaten  23 23 25 25  .5 .6 .7 .7  4,.8 5,.2 5,.5 6,.0  58 58 60 60  No. eaten per pred-h  No. surviving Pres.  Reared  Rearing mortality (%)  Length (mm) of preserved survivors Mean  SD  -  48 43  215 162  0.0 0.0  10. 81 10. 86  0.,74 0.,67  0., 15 0. 14 0.44 0.,46  86 74 54 47  167 187 167 163  0.0 0.0 0.0 0.0  10.,77 10..91 11. 12 11.. 14  0.,71 0..74 0.,72 0.,85  _  109 1 10  0 0  1 1 1 1  0 0 0 0  0.,43 0.,44 1 .. 10 1 09 .  Abbreviations: Par = parental crosses Tmt = predation treatment: control (con) or experimental (exp) Pres = preserved at end of experiment without further rearing Other abbreviations as in Table 2.  14 16 11 10  _  -  1-1,.60 0,.62 11,.84 0,.73 12,.25 12 . 11 12,. 19 12 .26  0,.89 0..85 0,.81 0,.82  105 number o r some o t h e r thus  occur  feature of the a x i a l  before vertebral  of a l l but experiment quarters  using  a  development  5, f r y  in  'plankton  each  segmentation, i s complete.  tank  splitter'.  were  and m i g h t At t h e end  divided  One-quarter  into  of the f r y  were p r e s e r v e d  f o r l e n g t h m e a s u r e m e n t s , and t h e r e m a i n d e r  reared  to  size.  end o f  a  larger  experiment Fry  A l l fry  were k i l l e d  i n anaesthetic, preserved  from  hypural  'plate'.  urostyle  and i n c l u d i n g  or  the t i p of the snout Counts  second  were  last  arches.  counted  one.  with  as  Fish  Such  other  ( T a b l e 25) a n d were e x c l u d e d  for  experiments or  most  undeveloped  in  preserved  vertebrae.  counts  f r y preserved these  without In both  by  less  without  fry.  buffered  Length  edge  of  than  1%  over  irregularities  further  counts  rearing  were were  reported  rearing  were  3 a n d 4, most had  with  developed  a l l treatments.  3 and 4 a r e of  rearing.  The  countable  of r e a r e d f r y and of f r y  Counts r e p o r t e d f o r experiment  post-experimental  Counts  In experiments  but  the  f r y only, since vertebrae  post-experimental  rearing  was  two n e u r a l a n d vertebrae  analyses.  without  experiments,  bore  vertebral  from  experiments.  reported f o r experiments  non-reared fry  10%  c e n t r a , e x c l u d i n g the  complex  1 and 2 a r e of r e a r e d  post-experimental  differed  of  frequently  rare  without  in  t o the p o s t e r i o r made  vertebra  two haemal  fry  the  t h e members o f t h e W e b e r i a n c o m p l e x .  occasionally  a l l  at  and c l e a r e d and s t a i n e d a s d e s c r i b e d a b o v e .  measured  of  preserved  5.  formalin,  last  were  both  vertebrae  Accordingly, reared  and  5 a r e e n t i r e l y of  Table 25. Vertebral development and abnormalities of peamouth chub surviving predation experiments. Abnormalities not including complex vertebrae In the last or second last positions. Length 1s the mean in controls at the end of experiments. Undeveloped vertebrae :x . P  1 2 3 4 5  Length (mm)  Without rearIng  8.9 10.0 10. 2 10.8 11.7-  100.0 57.5 25.8 13.6 O.O  After rearing 0.0 0.7 1 .3 1 .2  -  (%)  Abnormalities Nonreared  -  6.9 0.0 1.7 0.4  (%)  Reared 2. 1 2.0 0.6 1 .3  -  1 07 Abdominal and c a u d a l At  the  smaller  undeveloped  sizes  or  to  criteria. was  division  other  structures  The u s e o f r e l a t i v e  not  practical,  certain  such  not  and s p i n e s  size  as  the  dependent, or  the anal  using  position  f i n b a s a l s as  l e n g t h as a in  were  of  developed)  criterion  length  discontinuous  near  as  the  described  3 and 5, v e r t e b r a l c o u n t s a r e  treatments  among f i s h  l e n g t h a t t h e end of experiments  11.5  mm  assigned  i n experiment  to the small  percentage  of  fry  samples  preserved  smallest  X%  assigned  of  5).  below  f o r each of  without  fry  in  to the small  class  10.35 mm  experiment  3, r e a r e d  fish  were  F i r s t , the  a t t h e end o f t h e e x p e r i m e n t the  six  corresponding  size class,  in  as f o l l o w s .  post-experimental  the  above o r below a  (10.35 mm  In experiment  or l a r g e s i z e  ( s a y X%) was d e t e r m i n e d  groups  using  rearing. reared  Then, t h e group  and t h e remainder  the  were  to the l a r g e  class.  L e n g t h s were compared by Variances (Brown  were  and  tested  Forsythe  Brown-Forsythe  test  were s i g n i f i c a n t l y were  (when  the a n a l y s i s of experiments  compared between p r e d a t i o n  size  distinguished.  for Gasterosteus.  In  3,  strongly  changes  were  be  designation  haemal s p i n e  since  abdominal/caudal d i v i s i o n above  was  not  haemal a r c h e s The  c l o s u r e o f t h e haemal a r c h  relative  could  examined,  rudimentary.  abdominal/caudal either  vertebrae  compared  ANOVA,  for  heterogeneity  1974a), (Brown  calculated  and and  means  Forsythe  (p<0.05) h e t e r o g e n e o u s .  by c h i - s q u a r e  tests,  using  using  Levene's  compared  using  1974b) when Count  BMDP7D. test the  variances  distributions  calculated using  BMDP4F.  To  108 avoid 44,  c l a s s e s with 45  sizes  and 'other'  were s m a l l  continuity 200.  small  was  Linear  equality  expected  (Table  (Tables used  29), 26  c o u n t s were g r o u p e d  o r a s 44 a n d ' o t h e r '  and  30).  Yates  i n 2x2 c o m p a r i s o n s w i t h  regressions  of slopes  values,  were  tested using  calculated  when  as  sample  correction for  sample s i z e s using  under  BMDP1R,  and  BMDP1V.  Results Rearing 1,  mortalities  2 and 3 (Table  fungi,  24).  were h i g h  M o r t a l i t y was l a r g e l y  b a c t e r i a or p a r a s i t i c  strongly  selective  development  reared  (Lindsey  dying  during  groups  i n experiment  2.  differ  significantly  from t h o s e  post-experimental  i n these  counts  do n o t d i f f e r  p>0.40).  i t was  selective be  If  rearing lower  those  with  experiments group  Counts of these  low  were  of s u r v i v o r s of the  fish  small  with  with  forfish  mortality.  44  26)  with  This  a n d low i n t h e o t h e r  (Table  high  with  44 v e r t e b r a e  were a c t u a l l y  the  group  high  less  mortality.  since  treatments,  dying  during  the data  suggest  Given  mortality  In both  frequent  d i d not  w o u l d be e x p e c t e d  relationship  24).  of  f o r two  groups  vertebrae.  44 v e r t e b r a e  in replications  be  post-experimental  two  m o r t a l i t y was s e l e c t i v e ,  for  stages  obtained  1 a n d 2, r e a r i n g m o r t a l i t y was h i g h  with  the  f r y (Table  (p=0.38 c o m b i n i n g  mortality, fish  more f r e q u e n t  at  to  V e r t e b r a l counts of f r y  rearing  was, however,  experiments  expected  between g r o u p s w i t h i n m o r t a l i t y  Sample s i z e  rearing. that  groups  number  1962).  in  due t o i n f e c t i o n by  f l u k e s , and i s n o t  for vertebral  here  rearing  i n some g r o u p s  such to  than  in  was n o t s e e n .  In  in  one  control  experiments, f r y  among s u r v i v o r s  Thus, t h e a v a i l a b l e  in  evidence  Table 26. Vertebral counts of fry surviving (Surv) or not surviving (Mort) post-experimental rearing in two groups from experiment 2. Vertebral number (%) Group  £43  1. Control 2. Exptl  15C  15C No cover  -  44  45  546  No.  -  Mort Surv  0.9  50.0 56.6  50.0 41.6  0.9  Mort Surv  5.0 1 .9  55.0 62.3  40.0 35. 1  0.6  20 113  .  20 154  110 suggests that vertebral  rearing  number  i n these  The mean l e n g t h groups  tended  groups  mortality  was  not  t o be s l i g h t l y  of  predation  greater  a t t h e end o f a l l e x p e r i m e n t s was  5.  Rates  of p r e d a t i o n  to  those  statistically  in  selective  for  experiments.  of s u r v i v o r s  selection  strongly  in  than that (Table  significant  of f r y i n c o n t r o l  27).  i n only  i n t h e s e two e x p e r i m e n t s  the experiments  without  experimental  However,  size  experiments  3 and  were i n t e r m e d i a t e  significant  size  selection  (Table 24).  R e g r e s s i o n s between v e r t e b r a l Table  28.  Data  treatments any  experiment  differed before and and  since  a r e grouped  (p>0.l8).  predation  experiments  significantly  experimental  control  group.  size  experiments significant  might  between 3 and 4. in  in  Differences  experimental groups sample  In  from z e r o  the  in control  be  in  zero  were  parents  (experiments 2  in  in significance  In t h e l a t t e r with  by  slope but  not  the  experiments,  fry  slopes  not  in  differed in  between c o n t r o l difference  i n experiment  the smaller  Among  but  5,  1, 3  significantly  3 and 4,  control  experimental  t h e two g r o u p s  group  experiments  explained  negative  parents (experiments  experiment the  groups  slopes  nor e x p e r i m e n t a l groups.  rearing from  groups.  significantly  o f PM1  predation  replications in  1 and 2, s l o p e s d i f f e r e d  control  post-experimental  differed  The s i g n s o f s l o p e s  offspring  within  among s u c h  among t h o s e o f PM8  from z e r o i n n e i t h e r with  replications  s e t s of c r o s s e s :  among  4 ) , but p o s i t i v e In  over  s l o p e s d i d not d i f f e r  between t h e two  5).  number and l e n g t h a r e shown i n  the and in  5, b u t n o t i n  regressions  sample s i z e .  were Mean  Table 27. Mean lengths of peamouth chub fry exposed (exptl.) or unexposed (control) to predation. Means are the unweighted averages of the means within temperature treatments. Means within temperature treatments are also shown when the interaction (INT) between predation (PT) and temperature (TMP) treatments 1s significant. Mean length (mm) Exp.  Temp.  Control  Probability  Exptl.  E--C  PT  TMP  INT  1  Both  8 .93  8..98  0 .05  0.26*  0 .0001  0.72  2  Both"  10..01  10..08  0..07  0.31  0 .0001*  0.88  3  Both 15C 25C  10. 26 10., 14 10. 38  10..53 10.,54 10. 52  0.27 0.40 0. 14  <0.0001 <0.0001 0.081  0..052  0.026  4  Both  10. 84  10. 98  0., 14  0. 1 1  0..061  0. 17  5  Both  11 .72  12. 20  0.48  <0.0001* 0.,028  * Variances heterogeneous (p<0.05). Brown-Forsythe test used.  0. 1 1  Table 28. Regressions between vertebral number and length among peamouth chub f r y exposed (exptl.) or unexposed (control) to predation. Fry were either preserved at the end of experiments (Pres) or reared to a larger size (Rear). Predation treatment  No.  Intercept  Rear  Control Exptl.  266 494  43.8435 44.3808  0.0405 -0.0015  0.13 0.93  2  Rear  Control Exptl.  258 634  44.8603 44.3083  -0.0439 0.0015  0.73 0.92  3  Pres  Control Exptl.  60 170  42.1349 45.4714  0.2083 -0.0953  0.24 0.41  Rear  Control Exptl.  268 500  43.1562 43.9449  0.1147 0.0398  0.002 0.20  Pres  Control Exptl.  82 216  45.1025 43.9354  -0.0708 0.0330  0.41 0.48  Rear  Control Exptl.  358 675  45.0395 44.5598  -0.0605 -0.0217  0.035 0.27  Pres  Control Exptl.  219 451  44.2292 43.6556  0.0194 0.0635  0.72 0.043  Exp.  Type  1  4  5  Slope  Probability of zero slope  11 3 lengths varied groups  than  experiments within  more among between  3 and  in  replications  4.  But  replications  e x p e r i m e n t a l groups significance  replications  of  control  and  latter.  Differences  predation  significance consistent larger  sizes  experiment experiment  between g r o u p s  in  and  4 and  shown  cover  in  Table  between  those  experiment  five  levels Counts of  counts  of  since did  (p=0.065).  experiments  was  mm  or  did  an  between  selective  to predation  are  +/-  2  5 (Fig.  not  SD)  to  differ  predation  any of  exposure  to  greatest  change  i n any  variations consistent  to predation d i d in  and  significantly  i n e x p e r i m e n t a l groups  controls  in  17).  over temperature  pattern  in  9.4-12.3 mm  unexposed  n o t show any  the  in  the n o n - s i g n i f i c a n t  increase  in  changes  (mean  i n the frequency  The  a r e not  w i t h 44 v e r t e b r a e a t  are grouped  f r y exposed  after  observed  i n experiment  Data  differences  from  i n the ranges  f r y exposed  unexposed  counts  significance  sizes  of t h e s e treatments  1, a d e c r e a s e  vertebral  mm  29.  (p>0.13) and  experiments.  the  counts of  levels  experiment  from  10.4-13.1  those of  of r e g r e s s i o n s  fry  9.2-11.2  at smaller  the  result  in  significant  not w i t h i n  or unexposed  favouring  range  treatments, • since  between  count  the  3,  Vertebral are  selection  groups  o f mean l e n g t h s  These  exposed  also  Thus,  could  number.  experimental  e x p e r i m e n t a l groups  range  groups  vertebral  with  but  i n the s i g n i f i c a n c e  experimental for  were  i n these experiments.  between c o n t r o l  reared  reared control  groups  by g r o u p i n g o v e r a w i d e r  and  of  regressions  explained  control  of  not  with  predation  over  differ  experiment. fry  in  In  extreme  approached  i n f r e q u e n c y seen i n  i n the frequency of  f r y with  11 4  Figure  17. R e g r e s s i o n s  control  (C) a n d e x p e r i m e n t a l  predation axis  between v e r t e b r a l  experiments  but  i s a t t h e end o f e x p e r i m e n t s  lines  before  are transposed  rearing;  Asterisks zero  (E) g r o u p s ,  3-5. L e n g t h  r e g r e s s i o n s a r e among f i s h  number a n d l e n g t h i n peamouth  shown on l o w e r  horizontal  ( f o r exp. 3 and  with post-experimental  t o the e s t i m a t e d  slopes s i g n i f i c a n t l y  (p<0.05). L i n e s drawn o v e r  4, rearing,  lengths  s c a l e s of r e a r e d l e n g t h s a r e a l s o  indicate  chub  different  t h e r a n g e X +/-  shown). from  1.5  SD.  115  REARED  L E N G T H (mm)  44.6n  44.4i  44.2  44.6-,  C  Exp. 5 44.4^  44.2-  10  II  12  LENGTH (mm)  13  Table 29. Vertebral counts of peamouth chub f r y exposed (exptl.) or unexposed (control) to predation. P is the probability that count distributions do not d i f f e r between predation treatments.  Exp.  Predat ion treatment  Vertebral number (%) < 43  44  45  :>46  No.  P  1  Control Exptl.  4. 1 2,.4  59.9 60.,4  33 .3 36 .4  2 .6 0 .8  267 503  0 .065  2  Control Exptl.  0 .7 2 .9  64 .4 61 .6  34 .5 35..3  0..4 0,.2  278 654  0 . 19  3  Control Exptl .  1. 5 2. 9  57.7 55.8  38.,7 38.,4  2., 1 2. 9  333 683  0. 31  4  • Control Expt1.  2. 7 1. 8  62. 3 67. 2  34. 1 30. 1  0. 9 O. 9  440 891  0. 18  5  Control Exptl.  O. 9 1. 6  54. 3 55.9  42. 9 40.6  8 1. 2.O  219 451  0. 76  1 17 44 v e r t e b r a e about of  5%,  after  p=0.l8).  f r y with  44  selection. classes fry  Counts  are  exposure to p r e d a t i o n frequency  the  smaller  at lengths  again  lacks significance  with  before but  at  44 v e r t e b r a e  cannot  about  in  experiment  4 ) i  selective  neither  This  with  experiments  of f r y with  with  respect  provide  to vertebral size  the absence of s i z e  event  after  at  be 5,  than  (p=0.031),  the  some  shorter  evidence  at lengths  number  weak  prey  and  sizes  (1 and 2 ) , p r e d a t i o n  (3 was  n o r s i z e , and significant  One p o s s i b i l i t y ,  i n these  between  i s strong i n  only  number  of  Evidence f o r  number and l e n g t h were  selection  difference  11.5 mm  ( 5 ) , but  sizes  predation.  at  In experiment  lengths.  to neither vertebral  nor a f t e r  increase  any  the experiments at intermediate  respect  before  selection.  44 v e r t e b r a e  prey  3,  44 v e r t e b r a e a r e  common  under  but not a t s m a l l e r  between v e r t e b r a l  before  selection.  size  Conversely,  in  difference  to size  than  but t h i s  could  size  large  but the  f r y with  (by  experiment  (p=0.23).  at lengths  In experiments a t s m a l l e r  correlations  10.35 mm,  and  to size  a t the l a r g e s t in  In  a r e s i g n i f i c a n t l y more  these  predation  circumstantial  by  partly  10.3 a n d 11.5 mm,  selective  30.  by  or  more common a f t e r  over  (p=0.l0)  lengths.  favour  small  4  i n favour  obscured  exposure to p r e d a t i o n ,  be a t t r i b u t e d  summary,  selection  and  least  not a t g r e a t e r  In  the  after  exposure to p r e d a t i o n  lengths  i n Table  i n t h i s experiment,  frequent  experiment  been  within  are s l i g t h l y  less  fry  have  compared  in  3 a n d 5, s e l e c t i o n  (5.5%) i s n o t s i g n i f i c a n t  lengths  attributed  could  two e x p e r i m e n t s  44 v e r t e b r a e  in  predation  In experiments  vertebrae  i n these  with  exposure to  experiments,  suggested is  that  Table 30. Vertebral counts of peamouth chub fry exposed or unexposed to predation at small or large lengths in experiments 3 and 5. Abbreviations as 1n Table 29.  Exp. 3  5  Length class (mm)  Mean length (mm)  Predation treatment  Vertebral number  (%)  44  £46  £43  45  No.  P  <10.35  9 .94 10 .06  Control Exptl.  1 .7 4..2  64 .4 33 .3 56.. 1 36 .9  0. 6 2. 8  174 214  0. 10  >10.35  10.. 76 10. 80  Control Exptl.  1.3 . 2..4  50..0 55..5  44 .9 39 .4  3. 8 2. 8  158 465  0.23  <1 1 .5  1 1 13 . 11 .16  Control Exptl.  1 O.  53. 6 69. 9  43..3 29..0  2. 1 1 .1  97 93  0.031  >1 1 .5  12. 18 12. 47  Control Expt1.  0. 8 2. 0  54. 9 52. 2  42..6 43. 6  16 . 2. 2  122 358  0.61  119 high  predator  related This  efficiency  overshadowed d i f f e r e n c e s i n performance  t o v e r t e b r a l number or  possibility  experiment vertebrae  2.  is  discounted  Apparently,  perform  size  fry  e q u a l l y well at  by  of p r e y a very  which these  at these low  will small  small  predation  develop sizes.  44  sizes. rate in or  45  120  Part  V.  Changes  i n v e r t e b r a l number  with  length  in  wild  peamouth chub f r y Material  and Methods  F r y were c o l l e c t e d s t r e a m , Hemer C r e e k , t o be c o n f i n e d between  late  i n 1984.  to the April  from H o l d e n Lake a n d f r o m  creek,  Spawning o f peamouth chub and  into  the lake a t night, beginning  fry  migration  13.  Fry migrating  and  July  lake. 2300  h,  were  made  and  sampled  at  a t dusk.  In  sampler  earlier  or  later  between May  B (Fig.  made by d i p n e t (25 x 17 cm g a p e ) ,  from  o f May 12 o r May  two  a  14  and  occasions.  F r y were a l s o  12).  first  Additional sets  14 a n d J u n e 27 a t A s i t e s ,  a n d J u n e 27 a t s i t e  the  between 2200  on  day o r two.  migrated  between  water column. times  nights  15 m u p s t r e a m o f t h e  15 min d u r a t i o n  the e n t i r e  appeared  fry  1984,  on t h e e v e n i n g  s e t about  inlet  several  t h e l a k e were c o l l e c t e d  were made e v e r y  from t h e l a k e 31  into  on  After hatching,  occurred  were o f 5 o r r a r e l y  Collections  May  the lake  1, u s i n g a S u r b e r  Sets  occurred  and e a r l y June.  into  i t s main  collected  and  between  Lake c o l l e c t i o n s  were  canoe  near  floating  shore.  Vertebrae in  most  collected were  size, 10%  fry collected from t h e l a k e  divided  One-half  were u n d e v e l o p e d  and  buffered  from t h e l a k e i n June.  into halves  or -quarter the  in fry collected  remainder  formalin.  killed Fry  creek,  i n May, a n d i n s m a l l e r f r y  Fry collections  or quarters  were r e a r e d  from t h e  from t h e  using a plankton  i n the l a b o r a t o r y in anaesthetic  collections  from  to  creek  splitter. a  larger  and p r e s e r v e d i n the  lake  were  121 treated  i n one  of  three  ways:  (1) A l l f r y c o l l e c t e d larger  size,  since  (2) F r y 27,  g r o u p was  killed  formalin. the  June  groups. and  Fry  those  (3) into  second  Fry  small  11  mm)  on or  the  large c l a s s preserved  Part  I.  to  from  the  Total in  1.3%  of  fry  those  reared  excluded creek of  these  on  the  reared after  preserved  (>  10%  mm)  June  buffered  A f t e r these  dates,  divided  into  to a l a r g e r buffered  size  One  site),  and  10%  a  collection  size size,  formalin.  and  classes.  to a l a r g e r s i z e ,  size  or  second  collection  collection  be  9.5  and  measured,  last  from t h e  from t h e  c l e a r e d and  f r y cannot  in  on  splitter.  were a n a e s t h e t i s e d  Vertebral  Fry  and  in  larger size.  to  divided Those  and  those  in in  formalin.  was  after  from a n a l y s e s . not  in  IV.  18,  a plankton  were c l e a r e d and  upon c o l l e c t i o n  were  June  reared  small.  ( d e p e n d i n g on  J u n e 22  larger  lake  Part  arches  preserved  a  length  accessory  were  g r o u p s were r e a r e d  c l a s s were r e a r e d  reared  described  14  large  small  collection  and  to a  smaller  the  Fry  or  reared  collected  size  and  l a r g e r group p r e s e r v e d  (<9.5  18  g r o u p were a n a e s t h e t i s e d  i n the  i n the  20  groups u s i n g  in anaesthetic  Before  i n the  between May  i n t o two  s e c o n d g r o u p was  fry  14 and  sample s i z e s were r e l a t i v e l y  collected  were d i v i d e d  on May  preserved  s t a i n e d as and  last  in  counted  as  (other  vertebra)  from t h e  in  i n 1.7%  of  i n 0.8%  These abnormal  upon c o l l e c t i o n  s t a i n e d , but  compared d i r e c t l y  were m e a s u r e d . to those  than  occurred  creek,  l a k e , and  upon  described  centra  abnormalities  lake.  preserved  those  of  those  f r y were from  the  Lengths  of c l e a r e d  and  1 22 stained by  fry.  about  0.5 - 0.7  Linear were  C l e a r i n g and s t a i n i n g  probabilities  by are  i n order  ANOVA, from  Vertebral  'other'  t o reduce  fry length  mm.  r e g r e s s i o n was c a l c u l a t e d u s i n g  compared  BMDP4F.  appeared  calculated  chi-square  counts  to avoid  were small  BMDP1R.  Mean  lengths  BMDP7D.  Other  calculated  using  using  tests,  usually  grouped  expected  values  a s 44, 45 o r in  chi-square  tests.  Results Fry migration usually on  slight  t h e l a k e was g r e a t e s t b e f o r e  thereafter (Fig.  t h e e v e n i n g s o f May  occurred between  on  before  June  15  occurred over  had  counts d i f f e r e d  or a f t e r  and  1 a n d 19.  2200 a n d 2300 h  Vertebral  in  into  May  17  i n o n l y about 70% o f t h o s e  18  About or  markedly  45  (p<0.000l).  entering thereafter.  from e a r l y t o l a t e m i g r a t i o n regression analysis, Fig.  migrations  were a p p a r e n t l y  vertebral  number,  but  vertebral  2200-2300  varied  h  representative  on  counts a  of  given those  over  Average the  dates  of  with  respect  entering  (Table the  31).  vertebrae  t h i s date, but length of f r y  (p<0.000l  period, according  an e v e n i n g , f r y  time with  respect  to length  (Table 32).  f r y entering  evening  44  migration  19). Within  homogeneous o v e r  not  peaks  (Table  of  45% o f f r y e n t e r i n g b e f o r e  also  Lesser  f r y entering the lake  Counts  decreasing  Hence,  19.  vertebrae  between  the  linear  or  occurred  95% o f f r y e n t e r i n g t h e l a k e  entering  to  lake  1 8 ) . Peak m i g r a t i o n s  May  44  May 21, a n d  the 31)  lake  lake are  over  to  between apparently  the  entire  1 23  Figure  18. Number  Surber  sampler  o f peamouth chub f r y c a p t u r e d p e r 5 min s e t , a t 2200-2300  h i n Hemer C r e e k ,  1984.  Table 31. Vertebral counts of peamouth chub fry collected from Hemer Creek between 2200 and 2300 h. In May and June, 1984.  Date May  14 15 16 19 28 June 1 9 13 19  Rearing mortal 1 ty (%) 12 . 1 21 . 3 15,.5 10 .7 2 O 9..6 0..0 10. 2 2., 4  Vertebral count £43 1 .4 1.8 , 4 .3 , 2 .2 6 .3 4..7 6..9 5. 4 7. 9  44 46,. 1 46,.2 44,.3 71 . ,7 70.,8 80..0 58.,6 73.,0 78 . ,7  (%)  45 50,. 1 49..9 49..3 25..6 22..9 15. 3 34 .5 21 .3 13. 4  46 2..4 2,.0 2.. 1 0.,6 0. O 0.,0 O. 0 0. 0 0. 0  No. counted 423 941 140 180 48 170 58 296 202  1  Figure  19. L e n g t h s o f peamouth  between  chub f r y c a p t u r e d  2200 and 2300 h . V e r t i c a l  Regression  line  between  P i s the p r o b a b i l i t y  i n Hemer C r e e k  bars are standard  l e n g t h and c o l l e c t i o n  t h a t the s l o p e of t h i s  26  day  line  errors.  i s shown. i s zero.  127  SAMPLE SIZE 5-10 o 24-36 O 48 0 96 o  9.0  e  E  8.8 o LU  1  p<0.000l  < 8.6  LU  8.4 May 14  DAY  July 5  T a b l e 32. V e r t e b r a l c o u n t s a n d l e n g t h s o f peamouth c h u b f r y c o l l e c t e d f r o m Hemer C r e e k a t d i f f e r e n t t i m e s o n t h e same n i g h t . P ( l ) a n d P ( v ) a r e t h e p r o b a b i l i t i e s t h a t l e n g t h s a n d c o u n t s , r e s p e c t i v e l y , do n o t d i f f e r among col l e c t i o n times. Length Date  T i me  Mean  SD  (mm) No.  May  15 16  2215-2230 0115-0130  8.87 9.05  0.33 0.29  48 48  May  16  2115-2120 2145-2150 2215-2200  9. 15 9.02 9.02  0.21 0.27 0.31  11 48 48  P(D 0.0064  0.39  No. per 5 min  R e a r i ng m o r t a l 1ty (%)  Vertebral 43  number  44  45  (%) 46  No. counted  807 58  21.3 27.3  1 .8 5.6  46.2 44.2  49.9 50.0  2.0 0.0  941 54  59 338 378  16.7 18.3 15.5  5.0 2.8 4.3  47.5 51.1 44.3  47 .5 45.4 49.3  0.0 0.7 2. 1  40 141 142  P(v) 0.81  0.72  1 29 evening. Length May was  21  distributions  and  i n the l a k e b e f o r e about  decreased  from May  in a l l f r y c o l l e c t e d and  June  increased most  8,  the  f r y 9.3  and  mm  31  undeveloped fry  counts of  A  between May  14-18  and  frequency lake  of  between  growth of f r y  Average  f r y length undeveloped  Between  May  25  with developed vertebrae  v e r t e b r a e were d e v e l o p e d  from  34. on  after  the  counts  and May  in  collection.  differed  21  of  counts  among  results  from  among f r y m i g r a t i n g The  between  fry collected  reflect  greater  At  rate,  decreased from  The  mortality vertebral  lake  into  on  among c o l l e c t i o n s  the  B  dates  increased between  f r e q u e n c y of  this  lake  21  in the  on  May  19  of t h i s v e r t e b r a l  count  May  might  21  distributions  made a f t e r  and  in  among newly a r r i v e d count  A  increase  18 and  increased  frequency  the  sites  decreased  (p=0.0l3).  the  grouped  collection  and  of  differed  f r y w i t h 44 v e r t e b r a e  (p<0.000l),  are  Fry are  between  May  v e r t e b r a e were  these dates, counts  nor  collections  31).  l a k e between  Because  f r y w i t h 44 v e r t e b r a e between May  count  homogeneous  4,  (p=0.85)  frequency  (Table  any  28.  s i t e s , since vertebral  sites  later  presumably  vertebral  fry  Table  fry collected  Vertebral The  21  June  Little  V e r t e b r a e were  fry collected in  collection  (p<0.000l).  May  May  the l a k e  (Table 33).  of  i n the l a b o r a t o r y  among  (p=0.59).  shown  i n most  over a l l four  28  proportion By  20.  t o 23.  b e f o r e May  from  o r more i n l e n g t h .  are  reared  neither  21  at a l l lengths.  Vertebral 14  fry collected  June 27 a r e shown i n F i g .  apparent  actually  of  May  21.  and  23  f r y i n the  lake.  were  relatively  In  particular,  130  Figure  20. L e n g t h d i s t r i b u t i o n s  from Holden 1984.  The  broken  median and in  cohort  Lake  between May(M) 21 and  smallest A  o f peamouth c h u b f r y c o l l e c t e d  solid  Only  l e n g t h a r e shown f o r June  27,  l i n e s connect the e s t i m a t e d  lengths,  (see t e x t ) .  and J u n e ( J )  22.  respectively, f r y over about  of f r y 9 mm  in  131 LENGTH 50  (ocular micrometer units) 60 70 80  >o z LU ZD  O LU  or  •z. LU  U  rr LU  0_  20  r  LENGTH  (mm)  Table 33. Percent of peamouth chub fry with developed vertebrae, among those collected from Holden Lake at the size and on the date shown. Empty cells indicate fewer than 5 fry preserved without laboratory rearing. Length class omu <54 55 56 57 58 59 60 61 62 >63  mm <8.87 9 .03 9. 19 9.36 9.52 9.69 9.85 10.01 10. 18 >10.34  Collection date M21 0.0 0.0  M23 0.0 0.0  omu=ocular micrometer unit; M = May, J = June.  M25  M28  M31  04  08  0.0 0.0  0.0 0.0 12.5 18.2 42.9  0.0 7.8 16.9 40.6 53.3 63.9 76 .0 70.0  0.7 34 .8 45.2 82.4 90.2 96.4 98.6 100.0 97.7 100.0  4.2 36.8 72.2 94 . 7 100.0 100.0 •98 . 1 100.0 100.0 100.0  1 omu = 0.1641667 mm.  J1 1  J14  J18  4.5 50.0 70.0 73.3 100.0 100.0 100.0 100.0 100.0 100.0  5.9 66.7 50.0 93.3 100.0 100.0 100.0 100.0 100.0 100.0  2.9 50.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0  Table 34. Vertebral counts of peamouth chub f r y collected from Holden Lake between May 14 and 31, 1984. Fry were reared to a countable size In the laboratory.  Date  Rearing mortal Ity (%)  May 14 18 21 23 25 28 31  16 .0 24 .3 30 .0 7 .8 . 9 .6 10,.7 1 1.8,  Vertebral count (%) <:43 3 .0 3,. 1 3 .5 6..0 1 .0 2.,5 2. 8  44 50 .9 43,.0 68 .2 60,.3 61 . 1 62. 6 59..6  45  46  No. counted  44 .2 53 .4 27 .5 32 .8 37 .6 33,,2 36..8  1 .8 0,.4 0. 9 0. 9 0. 3 16 . 0. 8  165 223 349 232 306 364 497  1 34 the  frequency  of f r y with  p e r i o d May 23-31  In  the  following  analyses,  Fry  cohort  A;  entering  those  entering  cohort  A i s shown i n F i g .  those  the  approximate The  solid  median  June  entering  line  19-21,  size  median  limit  have s i m i l a r  and e x c l u d e  However, t h i s those  a small  proportion  to  of f r yentering  and  of t h i s  delimit  that  growth line  rates.  A  the lake  were r e a r e d Methods).  f r y below  to a larger size  after  to delimit line  shows  the  collection.  smallest  smaller  and  f r y may  conservatively  also  ensure  do n o t i n c l u d e a after  May 21. 20.  sizes  in  i n length  collection  that  significant  Cohort  is  B c a n be  the  June  4  C o h o r t C was  b u t i s n o t shown 9 mm  A.  No a t t e m p t  i n t h e J u n e 27 sample.  i n t h e J u n e 22 s a m p l e ,  d a t e b e c a u s e most  the  should  d i s t i n g u i s h e d a s t h e mode a t s m a l l  this  i n each  drawn  B and C i n F i g .  C as that  and  broken  line  Since  be  first  sample, a n d c o h o r t  cohorts  B;  of f r y a c t u a l l y in.cohort  procedure cohort  f r y are  May 22 c o m p r i s e  the  solid  f r y of  to  on  the  of f r y of t h i s cohort i n  cohort  may  of  An a t t e m p t  the  made  also present  over  1, c o h o r t  figure,  length  proportion  conservative  f r y assigned  before  C.  In t h i s  i s drawn a s s u m i n g  lengths  little  'cohorts'  lake  cohort  20.  have l o w e r g r o w t h r a t e s , t h i s high  the  from the l a k e ,  lower  three  t h e l a k e about June  estimated  each c o l l e c t i o n  varied  (p=0.83).  distinguished.  connects  44 v e r t e b r a e  in Fig.  in this  20  sample  (see M a t e r i a l  and  1 35 A positive correlation might  be  in  p e r i o d May  the  expected  entering not  i n any  absence  of  of  due  Fry to  (Table  in  Fig.  below  9.3  a high 33).  cohort,  early.  since  f r y with  the  lake  4  cannot  c o n f o u n d i n g can classes  grouped  together.  l e n g t h and least  for  when In  cohort  lengths  in  fry  was The  apparent  in  at  of  figure,  these  fry  Within  tendency  between  44  could  length in  and  cohorts  i n those  entering  d i f f e r e n c e among l e n g t h  classes  Nor  former case, latter  than  sizes  with  increased. this  June  collection  the  were more common  collected  mm.  those  35).  the  from  confounding  season  late  24.  omitted  length  is i t likely difference June  a l l fry  compared  by  4 and  most c o n f o u n d i n g grouping  over  12 mm.  These changes  of  with  fry  that  seen  between  case,  been e l i m i n a t e d  9.9-10.6  by  l e n g t h c l a s s and  significant  about  did  collection  as  the  s e l e c t i o n in favour  of a b o u t  upon  so e x p l a i n e d .  under  May  frequency  vertebrae  i n the has  before  lake  (Table  explained  the  by  significant  the  31  t h a n a b o u t J u n e 8,  explained 44  and  the  length  association  undeveloped vertebrae  decrease  be  cohort;  reflect  lengths  of  e x p l a i n the  length  same  lake  in length are  late  However, the  be  g r o u p e d by  later  partly  June  could  to  23  and  than  However, s u c h an  In most c o l l e c t i o n s ,  least  entering  vertebrae  fry preserved  frequency  obtained  the  fewer  fry entering  between May  21, mm  collections at  since  a s s o c i a t i o n can  c o u n t s of  tended  on  had  collection  vertebrae  be  A,  g r o w t h among f r y i n t h e  shown  date.  14-21  s u c h an  Vertebral are  in cohort  early in this period.  seen  lack  between v e r t e b r a l number  45  such among  22  are  are  of  between  time, in  at  length  vertebrae  at  Table 35. Vertebral counts of small or large f r y In cohort A, in samples collected between May 23 and 31. Length class (mm)  Date May 23  After rearing  Before rearing (estimated)  <10.6 >10.6  <8 .4 >8.4  Vertebral count (%) £43  44  45  46  No.  P  7 .6 4 .0  60 .6 60 .0  31 .8 34 .0  0..0 2..0  132 100  0.  May 25  9.6-10..9 >10.9  7.8-8,,4 >8.4  1.9 0 .0  59..6 61 .7  37 .9 38 .3  0..6 0..0  161 141  0.  May 28  9.6-10.6 >10.6  8.1-8..7 >8 .7  2 .9 2 .2  64..5 61 .0  30. 2 35..7  2 .3 1 .1  172 182  0.  May 31  10.1-10.9 >10.9  8.6-9. 3 >9.3  4 .0 , 2 .0  55. 6 60. 2  39..9 36. 6  0. 5 1. 2  198 246  0.  Figure  21.  Frequencies  of  f r y with  l e n g t h c l a s s e s of c o l l e c t i o n s Probabilities  are  grouped as  or  44  from other.  44  vertebrae, in  between J u n e 4 and  chi-square  tests  with  27.  counts  LENGTH  (mm)  1 39 No  sample a p p r o p r i a t e  cohorts  is  available  f o r comparison  to test  Such samples a r e a v a i l a b l e counts  of  fry  in  collected  on May  for  collected  those  Counts are of preserved in  31  fish  upon c o l l e c t i o n  between  and  the  f o r the  cohorts.  Fry  those  45  with  9.3-9.9  and  Since vertebral  number and  (Table  this  35),  favouring (though  f r y with  other  hand, 45  9.3-9.9 since and  mm  below  vertebral  9.9  mm.  Finally,  vertebral mm,  and  44  in  June  frequent, May  larger  can  be  31  in  May  selection A  June  counts  vary  little  suggesting  that  selection  similar  36).  at  with  i n May  vertebrae  samples length  favours  the  On  the those  lengths  comparing 4  only  and  T h i s comparison  confirmed and  samples  seen c o m p a r i n g  44  in  (p=0.022).  were more f r e q u e n t ,  sample.  i n the  frequency,  size.  i n June samples  mm  same  decreased in  (Table  9.3  samples  indicates  the  fish  The  length classes  l e n g t h were u n r e l a t e d  is  below  these  increased  f a v o u r i n g f r y with  May  in  and  of  i s seen  vertebrae  4 samples  vertebrae  result  the  at  and  length  frequency  result  the  selection  fry  14.0  in  This  in  for fry  developed.  samples.  seen  44  both  Fry  l e n g t h were u n r e l a t e d  number and  smaller  and  less  than  suggests  31  was  vertebrae  vertebrae  f r y with  vertebrae  as  lengths.  undeveloped  sample,  number and  over  Vertebral  were m o s t l y  June  9.9-10.6 mm  non-significant) f r y i n t h e May  the  smaller  22,  mostly  May  with  change  45  larger  with  were  grouped  alone.  June samples.  from  A alone  at  shown i n F i g .  the  vertebral  J u n e s a m p l e s of c o h o r t  frequency,  for  omitted  between  over  A are  fry  A  i n J u n e when v e r t e b r a e  length are again  grouped  for cohort  when v e r t e b r a e  reared  relationship  for selection  only  cohort  with  of  is valid samples,  at  lengths  counts (Table  between  of 36). 10.6  neither f r y with  1 40  Figure  22. V e r t e b r a l c o u n t s o f f r y i n c o h o r t  reared  after  collection  upon c o l l e c t i o n in  between  A, among  on May 31 a n d among t h o s e  preserved  J u n e 4 a n d 22. F r y c o l l e c t e d  J u n e g r o u p e d by l e n g t h .  fish  p=0.010  VERTEBRAE • 44  SAMPLE  •  -  0 325  QIOO  0 45  SIZE  O 175-250 O 0 ° "  OTHER  4  •  _ a  4 5 0  •  p=0.022  a.  May 31  June 4-22 i  10 BY  II L E N G T H (mm)  12  13  14  Table 36. Vertebral counts of small or large f r y In cohort A, on May 31 or June 4. Counts are of f r y preserved upon collection on June 4, or reared after c o l l e c t i o n on May 31. Lengths of reared f r y are the estimated lengths before rearing. Vertebral number (%) Group May 31 June 4 May 31 June 4  8.8-9., 3 mm 9.3-9.. 9 mm >9.3 mm >9.9 mm  £43  44  45  46  No.  P  3.0 2.5  55.4 69.3  41.1 28. 1  0.6 0.0  168 199  0.022  2.0 3.0  60.2 54.8  36.6 40.7  1.2 1.5  246 135  0.56  143 44 n o r t h o s e w i t h  and the  45 v e r t e b r a e  here of reared  since  varies  rearing  possibility  (Part  that  section  No  show  37,  of r e a r i n g  second  subsamples  from  the  splitter.  samples  from do  mortality.  is  unlikely  reared  indication pattern  despite  mortality  with  groups,  from v a r y i n g  groups.  third  between  vertebral 34.  different group  In  rearing consists  2250 a n d 2315 on June of set,  this  group  separated  significantly i n the extent  pattern  s e e n among  of r e a r i n g  differences  reared  extents of r e a r i n g  31 a n d  are  using  a  three groups c o n s i s t of  differ  number a n d t h e e x t e n t  or  in this  between  The f i r s t  variation  the s i g n i f i c a n t  not  c o l l e c t e d on t h e same d a t e .  counts wide  Results  i n Tables  sampler  was  rearing  seen  replications  same S u r b e r  with  selective  substantially  Nor i s any c o n s i s t e n t  that  is  groups,  In t h e p r e v i o u s  mortality  of  fry,  selective  number.  Each of the remaining  vertebral  between v e r t e b r a l  be  rearing  vertebral  different A sites,  replications,  may  f r o m Hemer C r e e k between and  plankton  case  that  a r e shown f o r f o u r  fry collected The  no  replications  mortalities  and n o n - r e a r e d  s u b s t a n t i a l l y among  mortality  for  consistent  number and e x t e n t  lengths.  number must be c o n s i d e r e d .  selective  likewise  mortality.  13.  rearing  I V ) , i t appeared  significantly  Table  mortality  to vertebral  section  no  greater  S i n c e c o u n t s a r e compared  respect  of  at these  among rearing  replications  mortality.  It  above  among  and n o n - r e a r e d g r o u p s ,  result  mortality.  seen  of  In  Table 37. Vertebral counts In replications of groups with widely varying extents of rearing mortality. Rearing Vertebral number (%) mortal 1ty 46 44 45 Repl . £43 (%)  Group  No.  P 0.81  1 2 3  15. 7 24. 1 2 .9  7.0 6. 3 5.3  69. 8 77. 8 72. 1  23. 3 15. 9 22. 6  0..0 0.,0 O..0  43 63 190  Holden L., May 14  A1 A3  21 .2 12. 5  3.2 2.9  52. 4 50. 0  41 .3 46. 1  3.2 1 .. 0  63 102  May 18  A1 A3 A4  34. 7 24. 1 14 .6  3. 1 3.3 2.6  50. 0 45. 8 26. 3  46. 9 51 .0 68. 4  0..0 0..0 2.6  32 153 38  0.24  May 21  A1 A3 A4  25. 1 58 .0 18. 0  2 .1 2 .1 5 .4  68. 4 70. 2 67. 0  28. 4 27. 7 25. 9  1 .. 1 0..0 0.,9  190 47 1 12  0.49  Hemer Cr., June 13  0.70  1 45 Vertebrae  were u n d e v e l o p e d  fry  but  this  difference  in  i n few  vertebral  experiments were  of the r e a r e d  number  (Part  by  among g r o u p s .  IV), vertebral unrelated.  12-24%  in  vertebrae,  numbers.  i f the degree  Even  vertebral  the p r o p o r t i o n s the  large  For  length class  i n June  and  non-reared  subsamples,  of  fry  undeveloped  less  sample  latter  two  about  vertebral  4%  in of  samples,  differed  than  among  undeveloped  May and  by  in vertebral did  A,  non-reared and  i n no  differ  between g r o u p s i n  number  cohort  10%  not  seen  produce in  some  vertebrae  were  f r y i n t h e 9.3-9.9  reared  fry  of  mm  the  May  of  June  in  the  length class  44  vertebrae  o r more from t h e numbers  i n the v e r t e b r a l  samples,  in  uncountable,  c o u n t s of r e c r u i t s  recruits,  On  1%  i n the  samples.  In summary, c h a n g e s  vertebral  with  development  However, t h e number o f f r y w i t h  first  se.  development  o r n o n - r e a r e d f r y i n t h e 9.9-10.6 mm  samples.  new  in  differences  of  of v e r t e b r a l  example,  in  of  by  However,  in predation  of f r y w i t h c o u n t a b l e v e r t e b r a e c o u l d  undeveloped  Lake  f r y used  the small d i f f e r e n c e s  differences  comparisons.  samples  differed  numbers,  cause of  number and d e g r e e  numbers  non-reared  non-reared f r y .  Among  Reared  the  (uncountable)  among  or l a r g e r  c a n be d i s c o u n t e d as a m a j o r  apparently  differing  i n some o f t h e s m a l l e r  rather  which probably into  the  l a k e between May  of  June  samples,  and  June  indicate  v e r t e b r a e o f most reflect  the l a k e ,  than s e l e c t i o n  t h e o t h e r hand, c h a n g e s  c o u n t s of f r y i n Holden  samples, selection  changes  or g r e a t e r  for vertebral  i n the v e r t e b r a l and  f r y were in  mortality  number  counts of  between  favouring  length fry  the  per  fry in classes  with  44  146 vertebrae lengths  at lengths between  9.9  10.6 a n d 14.0 mm), Selection occur  for  only after  countable.  below  9.9 mm,  and  10.6 mm.  selection  vertebral vertebrae  and those  with  At g r e a t e r  appears to  favour  number a t t h e s m a l l e r are  sufficiently  45 v e r t e b r a e a t lengths  (between  neither  number.  sizes  appears to  developed  to  be  147  Discussion  Experiments with The  experiments  differences vertebral number with  in  counts,  of  fry  length.  both  in  performance  selective  predation  and changes  survival  with  a high  intermediate  with  ratio  as  did  those  vertebral  using  Swimming  exposure  performance  performance  to predation  at intermediate  sometimes with  to  a n d i n swimming p e r f o r m a n c e e x p e r i m e n t s  the  a n d among t h o s e  pattern,  i n frequency  intermediate  best,  among t h o s e  Changes i n v e r t e b r a l c o u n t  increased  was  g r e a t e s t , among f r y  sizes,  sizes,  f r y a l s o conformed t o t h i s  high  different  seen  at large sizes.  the  f r y with respect  in relative  o f 0.82 AV/CV a t s m a l l  ratios  wild  of  demonstrated  was  during  ratio  have  i n mean v e r t e b r a l number o f w i l d f r y  from Holden Lake.  and  among  Gasterosteus  swimming  predation  ratio  with  The same p a t t e r n  sticklebacks  low  Gasterosteus  ratios  at  with a  with  i n that  with  length  f r y with  small  sizes,  at s l i g h t l y  larger  sizes.  This the  similarity  selective  laboratory, from  mortality  seen  and a p p a r e n t l y  differences  different  i n p a t t e r n among e x p e r i m e n t s  in  i n the  seen among f r y i n t h e w i l d , may  result  v e r t e b r a l numbers.  among w i l d f r y a r e p r e c i s e l y  swimming  those  the high  ratio  o f 0.82 AV/CV  wild  at just  those  sizes  f r y , as  did  performance  The c h a n g e s  with  among s u c h  predation  that  experiments  the  in  suggests  with  i n v e r t e b r a l count  seen  increased  when b u r s t f r y with  fry  expected  i f this  of  were s o . F r y  i n frequency  swimming p e r f o r m a n c e the  intermediate  i n the i s best  ratios  of  148 0.78-0.76. differed two  However,  important  t h e two  apparent  fry  best  or  exposed  shifted  may  slight  shift  at  performance the  two  sizes,  vertebral  large  sizes.  a t the  growth  during  require  growth r a t e s  and  0.5-1.1 mm/d  larger the  sizes  range  especially  and  the  however, h i g h i n t h i s  for  0.9-1.4  larvae  higher range,  at  at small  ( e x p e r i m e n t s H4-6).  reported at  discrepancies  o f 0.2-0.5 mm/d  15C  than  mm/d  and  temperature and  in  at  the  are those at be  due  to  would  mm/d  at  ( e x p e r i m e n t s H1-3), 25C  of  (Table  a r e i n most  mm  0.6-1.5  rates  fry  be  smaller  explanation  at  These  lengths  could  and  sizes  to  i n swimming  2.5  This 15C  at which  at the  experiments  experiments.  experiments  at  size  the  the b e s t .  0.5-0.8 mm and  range  and  appeared  in predation  were a b o u t  these  predation  predation  perform  ratios  Since lengths in predation  of experiments,  in  sizes  i n the  This  wide  experiment,  ratios  count  swimming  ratios.  the r e l a t i v e l y one  effect  temperatures f o r  count  intermediate sizes,  t h e end  25C  in  temperatures i n  relative  between  temperatures  count  i n the  D i s c r e p a n c i e s between mean  t y p e s of e x p e r i m e n t s mm  any  vertebral  experiments.  between  vertebral  in  somewhat l a r g e r  1.5-2  slightly  between  Second, p a r t i c u l a r  similar  simply r e f l e c t  to predation  with p a r t i c u l a r  favoured  experiments  experiments  to d i f f e r  the s i z e s at which  intermediate  difference  relatively  predation  performance  appeared  R e s u l t s appeared  was  with high  sizes  experiments  e x p e r i m e n t s , but  performance  of  the  respects.  temperature.  predation  fry  of  f r o m t h o s e o f t h e swimming  First, of  results  in  those  are mostly  at  within  other  species,  38).  They a r e ,  cases  considerably  Table 38. Growth rates reported for larvae and fry of several f i s h species, 1n the laboratory (L) or wild (W). Type  Length (mm)  L  7-13  0 .5  12C  Griswold and Smith 1972  L  8-14  1 .2  25-30C  Strawn 1961  W  >7-10  0.6 • - 1.4  Etheostoma spectabile  L  9-16  1 .0  26C  Perca flavescens  L  7-9  0..2  17-18C.  Morone s a x a t i l l s  L  6-7.5 8-9  0,.4 0,.2  18C, 3 %  W  <10 >10  0..2 0..8  Harengula pensacola  L  4.5-20  Anchoa mltchi11i  L  3-12  Clupea harengus  (L)  L  Spec i es Pungitius  pungitius  Mlcropterus salmoldes  Bel one belone G = growth rate (mm/d) T = temperature ( C)  Growth rate (mm/d)  Comments  Source  Kramer and Smith 1960 West 1966 Hinshaw 1985  500/4L sal1n1ty, 100/8L  Eldridge et a l . 1981 Dey 1981  22-33.5C, G = 0.054 T - 0.85  Saksena et a l . 1972  0 .6  29C  Saksena et a l . 1972  >10  0.. 1 0,.2 0..3 0..4  1n in in in  12-35  0.7- -1.8  0.3 - 1 .0  120L tank 500L tank Loch Ewe bags Norway pond  8- 14C 8- 14C 8- 14C 8- 14C  13-24C. G = 0.093 T - 0.43  Geffen 1982  Fonds et a l . 1974  150 greater  than  Holden Lake length, fry  rough  (0.2  0.4  mm/d  respectively).  are  minimum  adjacent  peaks  collections.  i n the  for wild  But  the  estimated  distributions  length any  case,  from  growth  have been g r e a t e r due  either  to the  change  r a t e s of w i l d  f r y under  in  wild, or  growth  judged  may  laboratory  of  estimates,  In  experiments fry  or  estimates  to  high  the  food  densities  sizes  when  is first  larger  s i z e s when f e e d i n g  is well established  Smith  1960;  West  Feeding  was  well  experiments, conditions.  1981;  sizes  larger  f r y with  than  of  the  average  the  more  any  the  length  experiments can if  mortality  smaller predation  was  a l s o be  Such  i n the and  explained  usually size  when  even g i v e n  the  case  selective,  was  1972).  holding  transferred to those  growth r a t e s  growing  between  if  have  slower  two  types  In of  rates, at  i n most e x p e r i m e n t s , larger  of  selection  growth  concentrated  of  been  individuals.  the  favouring  and  predation  t o crowded  population,  experiments  was  Smith  in  Also,  fry  Kramer  and  fry  the  r a p i d l y at  e x p e r i m e n t s may  faster  discrepancies  in predation  sizes.  these  i n these  rates  vigorous  (e.g.,  due  in  smallest  c o n d i t i o n s were s i m i l a r  predation  favoured case,  small  sized  conditions  increases  used  well established feeding.  survivors  greater  fry  P e r h a p s g r o w t h r a t e s of  uncrowded e x p e r i m e n t a l  and  Griswold  in  were  to the  the  1966;  established  though  similarly  the  wild  predation  of  slow a t  in  successive  those  Growth  initiated,  mm  between  during  experiments.  Dey  fry in  from c r o w d e d t o uncrowded is typically  8.2  distance  of  during  feeding  over  growth r a t e s of  rates  than  or  fry in  prey.  the since  151 In  the above view, H6),  (except  count.  Hence,  been  more  much  be  small  result  result  selection intense  than  at  one  and  one  and  of  over these interval  j u d g e d on  then a  may  have  the b a s i s  experimental  of net groups.  of experiments  expected to completely cancel  effects  of s e l e c t i o n  near  the  start  most h u n g r y ,  experiments An  laboratory  n i l during  view is  swimming p e r f o r m a n c e  i s that  not  the  of f r y  than b u r s t  measured  at the a v a i l a b l e  low  during  day  result with be  swimming  sizes  the o b s e r v e d s e l e c t i v e  predation  between v e r t e b r a l  number and  in  at  in burst  swimming.  Or  have  resulted  other morphological characters  be  of  avoiding  from  a  some o t h e r m o r p h o l o g i c a l  sizes  in  be  best  the  importance  not  the  of  few  avoiding  i t too depends  or b e h a v i o u r a l c h a r a c t e r used here,  importance  burst  perform  than  might  in  numbers.  could  Perhaps  counts  seen  vertebral  but  in  reduced.  i n the  important  framing r a t e s .  in fast-starts  much  later  predation  performance,  the  in experiments  of d i f f e r e n c e s  more  at  predators  periods  different  would  predation  when  periods later  the s e l e c t i v e  c o u n t , but p a r t i c u l a r  larger  correlation  i n experiments  night  may  predators  somewhat  and  performance  on v e r t e b r a l  early  because  when p r e d a t o r numbers were g e n e r a l l y  alternate  Fast-start  of e x p e r i m e n t s ,  each  various  t h e end  when p r e d a t o r s were a b s e n t  the  any  control  r a t e s were p r o b a b l y g r e a t e s t were  of s e l e c t i o n  that  sizes  for f i r s t  experiments  near  sizes  the l a r g e r  predation  o b s e r v e d a t t h e end  within  i n f r e q u e n c y between  Selection not  The  i s thus the net  intervals.  changes  f r y grew d u r i n g  they experienced s e l e c t i o n  second v e r t e b r a l experiment  as  in avoiding  predators  are  predators.  yet  likely  At to  expressed:  1 52 lateral  plates  undeveloped, differences  are  and  not  yet  formed,  f i n rays  are  not  related  between  different  (Moodie  et  al.  from d i f f e r e n t a  single  fully  to v u l n e r a b i l i t y lateral 1973)  plate  but  populations.  population,  s p i n e s a r e r u d i m e n t a r y or formed.  to predation phenotypes  have been  in  t h e r e the d i f f e r e n t The  sticklebacks  so s u c h a s s o c i a t i o n s  Behavioural found  sticklebacks  phenotypes  were  u s e d h e r e were  between t r a i t s  from  are  less  likely.  However, t h e c h a n g e s wild  fry  argue  against  intermediate vertebral wild was  at  just  changes  i n the w i l d  from experiment seen  vertebral  discrepancies  seen  recorded  Thus,  burst at  from g r o w t h  swimming end  at  performance  of  those  that  an  performance,  and  that  smaller  selective effect  swimming  predation  were  predicted  the  from  the  predation  frequencies either  resulted  during  in  F r y w i t h h i g h or  o r were n o t  and  seen  i n frequency i n the  the  count  predation  of m o r t a l i t y  view.  i t seems l i k e l y  swimming  between  frequencies  increased  when t h e i r  laboratory  on  resulted  the c o n c e n t r a t i o n  ratios  ( e x p e r i m e n t s H4-6)  i n the  count  alternate  in vertebral  (H1-3).  number  experiments  count  At the s i z e s  experiments,  predation  this  those s i z e s  the b e s t .  absent  in vertebral  the  of  length  performance  experiments sizes  in  and  these  experiments.  Changes from  in vertebral  those p r e d i c t e d  respect.  Fry  significantly However,  from  with  f r e q u e n c i e s of w i l d  swimming p e r f o r m a n c e  the  increase  f r y with t h i s  count  low in  ratio  ratio  frequency were r a r e  of at  0.72 any  fry  differed  experiments AV/CV size  i n the w i l d ,  i n one  did  not  i n the  wild.  so  selection  153 in  their  favour  over  d e t e c t a b l e changes these or  f r y were f a v o u r e d  intermediate to  sizes,  f r y with  even  so  be  briefer  intermediate  periods  ratio  of  site  B but  not  0.82  than  be  at  on  site  as  apparent  reflect  in  low  the  ratios  in  the  may  than  have  at  these  w i l d than  with  larger  those  have been  produced  experiments,  were t h o s e  w i l d than may  not  laboratory  rates  at  high sizes  the  smaller  favoured  during  were t h o s e  somewhat between  A.  dates  embryos,  i n frequency  with  high  and  than  at  small  or  site  may  have  experienced  site  B.  or  A were  Size at  A.  spatial  d i f f e r e n c e s i n the  size  lower  below).  between s i t e s A and  l a r g e r f r y to s i t e  mostly  hatching  (see  of  at  temporal  from  f r y from  the  sizes  reflect  incubation temperature decreases  recruitment  temporal  Fry with  Fry  difference in selection by  sites.  This difference could  variation.  earlier  i n c r e a s e s as  explained  Growth  AV/CV i n c r e a s e d  spatial  temperatures often  In  larger sizes  also differed  high  collected  at  greater the  period  ratios.  Results  rather  brief  frequency.  ratios.  appeared  The  in  a  Or  B  could  i t might  or  type  of  predators.  Predation populations, geographic  e x p e r i m e n t s were r e p l i c a t e d from  separation.  considerably  Fish  i n morphology  results  were s i m i l a r  ratios  of  sizes,  and  vertebral  ecologically  those count  dissimilar  from  the  (e.g.,  two  with ratios  to caudal low  vertebrae  ratios  differed  at  fish  lakes  from  with  populations  in l a t e r a l  between p o p u l a t i o n s ,  abdominal  using  two  a wide differed  p l a t e number).  in that  fry  with  were f a v o u r e d  larger  sizes.  Yet,  at  high small  However,  m a r k e d l y between p o p u l a t i o n s ,  and  1 54 different two  actual ratios  populations.  depends not j u s t  favoured  Perhaps  the  width  may  h a v e v a r i e d between t h e two  was of  depth  these  were  not t o t a l  to caudal  related.  ratios.  (Lindsey  experiments,  apparently abdominal  Fry  for  larger  total  at small  using  Gasterosteus.  selection  vertebral  numbers  n e i t h e r number  sizes  Gasterosteus, in predation  reported  for  experiments, experiments, sizes  1986)  such which  but r a t h e r t h e r a t i o the  numbers  for  the  two  tended ratio  characters t o have  high  resulted  in  both  i n l a b o r a t o r y e x p e r i m e n t s (K1,  Fry  with  with  low  high  numbers  numbers  (31)  (32) a t  were  slightly  Mylocheilus Mylocheilus  Selection  v e r t e b r a l numbers  with  dimensions  sizes.  Results  and  ratio  of f u n c t i o n a l importance  However,  low t o t a l  those  count  and L a v i n  v e r t e b r a l number,  number,  i n the  populations.  the c h a r a c t e r  with  sizes,  Experiments with  low  vertebral  1975; L i n d s e y  K2, H2, H3) and i n t h e w i l d . favoured  optimum  vertebrae.  Accordingly,  selection  a t t h e same f r y s i z e  on f r y l e n g t h , b u t a l s o on o t h e r  as  In  or  were  resembled  acting  on w i l d f r y a p p e a r e d  (44) a t s m a l l  lengths  (45) a t s l i g h t l y  greater  a t even g r e a t e r  lengths  selection  appeared  experiments than  predation  so t h i s  Of c o u r s e ,  lengths  to occur  were  using to  favour  mm),  high  (9.9-10.6  (10.6-14.0  c o u l d be due  or t o the c o n c e n t r a t i o n  i n experiments.  (9.3-9.9  mm).  at s l i g h t l y  i n the w i l d .  experiments  discrepancy  those  those to  Again,  mm), As  larger lengths  a t t h e end o f growth  during  of m o r t a l i t y a t the s m a l l e r  d i f f e r e n c e s between r e s u l t s  in  1 55 the  laboratory  physiological,  and  this  Gasterosteus,  and  laboratory-reared  using  or  wild  possible since  Evidence  the  morphological  laboratory-reared However,  in  were  predation than  a d a p t e d , or a t are  25  have  been  (Note  relative  subsampling  the  advanced  but  to  5,  that  in  fry .after  Finally,  as  importance  in Mylocheilus  abdominal  to  f r y with  selection  start  the  of  Most  of  conducted at  because  and  the least  may  to a  have  been  5  also  may  increased due  to  necessity probably  results  by  fry  character  of  functional  been  even t h o u g h t h i s Variation  same t o t a l number  The  in  In a l l  Gasterosteus,  experiment  the  listed  development  larger size.  of  vertebrae  experiments).  have a c t u a l l y  for t o t a l  for  conclusive  development  with  but  vertebrae,  less  experiments;  partitioning  may  hold  experiments.  i s absent  error  distinguished.  laboratory-reared have r e d u c e d  the  Gasterosteus,  caudal  practically  of  reared all  e r r o r to the in  at  between  w h i c h v e r t e b r a l numbers were  experiments  f o r f r y t o be  rearing  end  to  Mylocheilus.  not  was  vertebral  sampling  introduced  be  that  due  between w i l d f r y  were a p p a r e n t l y to  be  of  Gasterosteus.  s i z e s where s e l e c t i o n  less  case  does  experiments  those  i s among f r y a t  experiments  of  below  undeveloped.  Table  the  similar  using  also  differences  f r y i n swimming p e r f o r m a n c e  from  sizes  in  explanation  experiments using Mylocheilus at  could  behavioural  fry,  results  Mylocheilus  partly  wild  in  size.  the  ratio  of  ratio  could  not  this  ratio  among  number of v e r t e b r a e  i n the  laboratory.  may  1 56  for  Both  i n l a b o r a t o r y experiments  fry  with  those  sizes  when  coincidence this  low v e r t e b r a l  selection  than  some  myomeres  size  may  related  to  that  be t h e  which  smaller yet  lower  Burst  to  than  vertebral  Effect  shock  selection  sizes  typical burst  While  shocks  stimuli  whether  (body  seen  number  this  are  a s may  f r y with  smaller  study  by a p r e d a t o r obtained  favour  those  obtained  by  Fuiman  in this  study  larvae  (50-65 B L / s a t . 2 1 - 3 0 C ) ,  These v a l u e s  but h i g h e r  responses to  more  mordax,  (Webb a n d  were a b o u t  are  zebra than  electric  F o r e x a m p l e , mean  shock  1981).  for  f r y with  those  Engraulis  (Webb  (1986)  If  performance  l e n g t h s / s e c ) a t 15 a n d 25C, r e s p e c t i v e l y  w i t h a mean l e n g t h o f 8.5 mm).  of the  at higher  u s i n g an  to  1981).  larvae,  not  favoured. occur  as  sizes.  swimming  in this  limit  i s not a n a t u r a l s t i m u l u s ,  anchovy  such  44 v e r t e b r a e a t y e t  or i t might  on b u r s t  initiated  t h e lower  vertebrae  here,  rather  coincidence, i t i s  s t i m u l a t e d by an e l e c t r i c  Maximum v e l o c i t i e s BL/s  segmentation  results  favour  This  involved in  axial  ( c f . Webb and C o r o l l a  1981) o r by p u r s u i t  54  44  just  developed.  a r e a p p a r e n t l y comparable  speeds of n o r t h e r n  similar  these  might  occurred at  themselves,  the  numbers a t t h e s e  swimming was  electric  of  selection  centra  at smaller sizes,  those  of v e r t e b r a l  stimulus.  from  wild,  structures directly  vertebral  f r y with  v e r t e b r a e were d e v e l o p e d temperatures,  first  A l s o because of t h i s  determine  range over  the  the  (44) f i r s t  were  feature  or n e r v e s .  possible  numbers  vertebrae  suggests  and i n  are  Corolla  38  and  (for fry  comparable  danio Danio those  to  rerio  obtained  by  1 57 Webb a n d C o r o l l a and  by R y l a n d  (11-16 using  (1981) f o r a n c h o v y l a r v a e  (1963)  BL/s  at  for plaice  6.5C).  Pleuronectes  ( V a l u e s were  a s t o p w a t c h a n d measurement  underestimates  (Fuiman  and  25C.  velocity  Fuiman  of zebra  obtained  a  gairdneri  between  danio  value  independent  of  25 B L / s a t 17C) platessa  larvae  obtained  by R y l a n d  (1963)  and  were  grid,  so  probably  1986)).  The Q ( 1 0 ) f o r maximum v e l o c i t y 15  (about  in this  (1986) o b t a i n e d  for  21 and 30C.  subadult  5 a n d 15C, b u t f o u n d  of temperature  in this  was 1.4 between  t h e same v a l u e  l a r v a e between 1.7  study  f o r maximum Webb  rainbow  (1978)  trout  Salmo  t h a t maximum v e l o c i t y  species at higher  was  temperatures  (15-25C). Spouge to  v e r t e b r a l number  model  indicated  vertebrae  on  to caudal optimum but  of the  absolute  r a t h e r than  number  of  of the r a t i o  as demonstrated here.  conformed  number w i t h  length  selection  is  thrust Their  locomotor  of abdominal  A relationship  intense at l a r v a l with  vertebral  number w i t h  observed  observed  between  1975) o n l y a t l e n g t h s  If selection  and f r y lengths  and  model  (and these  in over only  t h e maximum  f o r v e r t e b r a l number  is  are positively  model p r e d i c t s a d e c r e a s e i n  maximum l e n g t h , a r e l a t i o n s h i p  Spouge  model,  increase  a t l a r g e l e n g t h s near  adult length), their  trend.  the  i s e x p l a i n e d by t h e i r  concentrated  fora population.  to  (Lindsey  Thus, p l e o m e r i s m  correlated  the  relating  on h y d r o d y n a m i c c o n s i d e r a t i o n s .  performance,  relationship  10 cm.  recorded most  based  a model  v e r t e b r a l number a n d l e n g t h was p r e d i c t e d by t h e i r  this  about  (1979) d e v e l o p e d  an e f f e c t  vertebrae  vertebral  if  and L a r k i n  Larkin's  model  also  opposite to contained  1 58 factors  d e p e n d e n t on  m u s c l e v o l u m e ) , but would  decrease  Jordan's might of  rule,  still  other  be  in  or  by  observed  in t h i s  of  the  the  effects study,  length  concentrated  Lighthill's  of  nor  to  the  the  theory  might  body  position  reasonable  small,  along  when t h e  some e q u a t i o n s  an  of  of  the  the  by  with  this  rule  temperature  efficiency,  of  Spouge  thus on  body  between  temperature  model was  theory  for  Since  more  body in  questionable and  Batty is  m o d e l , Spouge and vertebra  Larkin  vertebra  to  be  relative  along  a  a and  large  1981), small.  Larkin  but In  assumed  infinitesimally  validity. was  (1971)  appropriate.  over  position  small  amplitude  valid  (e.g.,  with  i s not  bending passed  not  to  using  locomotion  Lighthill's  been  wave of  change  (Jordan's  derived  amplitude  of  have  fish's  vertebral  ( i f s e l e c t i o n i s assumed  is certainly a  conform  performance  a sine-wave of c o n s t a n t  in their  caudalmost  trends  use  the  caudalmost  assumption  a s s u m p t i o n made velocity  was  T h i s assumption  length  with  number  The  amplitude.  fish's  deriving  that  model  or water  'elongated-body'  swimming  be  the  sizes).  (1970) assumed t h a t  may  variation  Larkin  populations  Lighthill  in  suggested  of  number  i s in disagreement  vertebral  swimming,  large-amplitude  change  and  of  small  small  burst  velocity.  unit  vertebral  (hydrodynamic  (pleomerism)  at  (1970)  undulations  model  Spouge  o b s e r v e d among f i s h  during  systematic  power p e r  that  This  Larkin  and  v e r t e b r a l morphology).  to  and  indicate  c o l d e r waters.  explained  neither  be  to  (viscosity  t h o u g h Spouge and  Predictions  rule)  tended  variables in their  proportions  number  temperature  that to the  A the  critical lateral  preceding  one  159 depends o n l y myotome.  upon  This  the  rate  assumption  of  ignores  transmitted  from more a n t e r i o r  acting  a  view  on  that  body  by  Blight  The body  idea  of  a  that  fish was  locomotion  1926;  (Breder  questioned generated on  a  relatively end.  (1933b),  view,  so l o n g  stiff  The  generating  who  was  of  of  burst  1979). myotomal  1976) During  in  passing  by  also  side  and  that  body  was  studies  contract  in adult  contraction  steady is  fish  gradient first  in  of  at  the  carp  seen,  when  but  Gray  along  the  caudal  activity view.  simultaneously Triturus  waves  in A l l  during  helveticus  (Kashin  longitudinal the  in  by  the  alternate  Cyprinus carpio  swimming, a  caudal  flexibility  swimming  newt  be  flexibility,  demonstrated  Blight's  of the  (1977)  simultaneously  i s of v a r i a b l e  Gadus m e r l a n g u s o n l y  i n larvae  of  waves o f b e n d i n g w i l l  t h e s e waves were t r a n s m i t t e d  support  the  waves o f  However, B l i g h t  a r e seen t o c o n t r a c t  slower  down  coincident  early  1980).  Electromyograms  swimming, b o t h  (Blight  result  1933a), a n d has p e r s i s t e d t o t h e  this  bending  showed t h a t  a  fish  recently discredited  seen  segments  as the f i s h  intact.  on  swimming  a view  resistance  I t i s b a s e d on t h e  a t t h e a n t e r i o r end and f l e x i b l e  a m p h i b i a n s and f i s h myotomes  Gray  suggesting  importance waves  a  caused  suggested  body o f a swimming w h i t i n g fin  are  even when a l l m u s c l e  side,  seen on  Wardle and V i d e l e r  this  water  flexibility.  t h e waves o f b e n d i n g  swimming  (e.g.,  preceding  1977) .  muscular c o n t r a c t i o n  present  the  t h e e f f e c t s o f b e n d i n g moments  waves o f c o n t r a c t i o n ,  (1976,  of  segments and o f  of v a r i a b l e  t h e waves o f b e n d i n g  from c o i n c i d e n t  contraction  of  et a l .  delay  in  muscular  160 activation 1976; the  not  Kashin  caudal  and end  c o i n c i d e with  et a l .  adult tench  delayed  of  do  Tinea  the  of  the animal  with  simultaneous theory).  Blight  conduction also saithe  wave f r o m h e a d rather  become s h o r t e r , t o w a r d  the  This  results  in a period  the  position  of  the  is least  expected  but  r a t h e r the  the  that the  the  frequencies.  as  the  a standing  tail  moment does not lateral wave.  body  That  theory  is, left  the  running  does,  and  over  in  is  analysis  as a  curvature  produce a l t e r n a t e c o n t r a c t i o n s s i m u l t a n e o u s l y  f o r wave  This  travel  of  oscillation  swimming  V i d e l e r 1984).  this  propagation  Blight's  fast  such  of  flexibility  of  side,  conventional  lateral  Finally,  analysis  (Hess and  bending  to t a i l  of  to  the  a  (when  function  i s not  r e d u c t i o n of  adjustment  kinematic  body  according  i n muscle a c t i v i t y  by  behaves as  is  t h e myotomes on  'S'  of  activity  1976).  muscular  swimming  of  at d i f f e r e n t  that  of a c t i v i t y (Blight  Pollachius virens  indicates  of  i n steady  (Blight  most  and  supported  onset  bending  of  delay  head  the  of  example,  (1976,1977) s u g g e s t s  waves o f b e n d i n g , the  For  waves  activity  activity  longitudinal  of  tinea,  bursts  simultaneous  coinciding  1979).  the  right  but sides  the  whole  body  in  generating  fish  locomotion  length.  The the  running  suggests on  importance  an  of a g r a d i e n t  waves  explanation  swimming  differences  in by  f o r the  performance.  between a b d o m i n a l and  influenced  of bending  the  effect  of  of v e r t e b r a l  count  the d i f f e r e n c e i n  regions  However,  number of  flexibility  characteristic  Much of  caudal  girth.  in  of  a  fish  flexibility  segments  (i.e.,  ratio  flexibility  results  should hinges)  also per  from be unit  161 length, not a  especially  so r e s t r i c t e d high  ratio  relatively caudal  regions;  vertebrae  may  flexibility body  Lake  those  reflect  small s i z e s ,  for  sizes,  small  that  rainbow  trout  during  ratio  a low r a t i o  favoured  fast-start  at  (1981)  found  similar  in  large that  7  a relatively  high  to  regions.  The  with  using  this  a low g r a d i e n t  vertebrae  Conversely,  to caudal  sizes.  Thus,  length at selection  i n f l e x i b i l i t y at  sizes.  in flexibility  changes w i t h  smaller  with  length.  p a t t e r n was s i z e  and  (1981) d i d f i n d  i n larger  fish,  wavelength 10  and  mm p l a i c e  (1984)  were  frequency  in  found body  between observed  to fry sizes.  larvae at cruising beat  of  rainbow t r o u t  amplitude  t h a t maximum t a i l  (1976)  dependent  relationships,  may n o t e x t e n d  length  Webb  Webb e t a l .  However, t h e s e  Holden  suggestion.  sizes.  of precaudal  kinematic  caudal  selection  swimming t h e w a v e l e n g t h a n d a m p l i t u d e  relatively  relatively  and  of abdominal  large  10 t o 40 cm i n l e n g t h .  steady  were  kinematic  have a  abdominal  of abdominal t o caudal  ratio at large  l e n g t h s o f 5 a n d 56 cm.  Batty  ratio,  with  f o r some optimum g r a d i e n t i n  i n t h e optimum g r a d i e n t  observed  in  between  consistent  a n d a low  Fish will  i n p r e d a t i o n experiments  ratio  from  flexibility is  vertebrae  and a h i g h g r a d i e n t a t l a r g e  result  waves  low  f o r the r a t i o  a high  characters  Changes  that  a  selection  and a h i g h  sizes,  might  caudal  flexibility  i s also  favoured  both  to  between a b d o m i n a l a n d c a u d a l  favoured  selection  whose a b d o m i n a l  as i s that of a d u l t s .  with  selection  sticklebacks  small  in  p r o p o r t i o n s seen  Selection at  abdominal  low g r a d i e n t  Thus,  fish  by wide g i r t h  of  gradient.  for  in larval  Batty  relatively speed.  But  decreased  1 62 greatly  as s i z e  stiffer  caudal  (1972)  reported  anchovy  larvae,  style  larvae,  11  caudal  regions  as  herring  high  R  proposed  that  amplitude  to the  is  resistive  forces  which amplitude reactive  increases  forces  to  the  likely  t o be r e l e v e n t  smallest  generate values changes Weihs  routine  larvae  towards the t a i l  i n 11 mm  might  in  most  favour  an i n c r e a s e  mm more  Weihs  of of  the  while  forces  While  Batty  activities  of f i s h  swimming  accelerate  seen d u r i n g  1986) may be more i m p o r t a n t  in  which  larvae, relies  larvae,  since  speeds high  Weihs  1986).  causes of the  may  they a r e not  to  development  in  mainly  arguments  activities,  larval  (1984)  r e l i e s m a i n l y on  of large  these  while  dominate  larvae,  body,  that  (viscous)  thrust,  1986).  small  style  i n Reynolds  resistive  r a p i d l y towards t h e t a i l ,  can  i n 22  swimming  i n generating  o f R >> 200 (Webb a n d  i n morphology  the  length  and  style  to burst  swimming  to the  (<20),  forpropulsion.  apply  in  The a m p l i t u d e o f  (inertial)  (Webb  for propulsion,  in larger  body  the changes  reactive  over  Hunter  sizes.  importance  swimming  change  towards the t a i l  with  A t low R  thrust  large  amplitudes  of  grow may r e f l e c t  growth.  (>200),  that  relatively  1977).  larvae.  linearly  at larger  larvae  beat  angle  linearly  favour  (Blight  herring  changes  a r e o f predominant  contributions  and  mm  maximum  (1984) s u g g e s t e d  (R) d u r i n g  forces  the  22  increased  latter  might  (1984) o b s e r v e d a  and  These  Batty  on  and  sizes  larger t a i l  a n d more r a p i d l y t h a n  flexible  number  at smaller  and B a t t y  of motion  larvae.  seen  a change t h a t  relatively  oscillation  direction  at  regions  between  lateral  increased,  even  enough t o The  (e.g.,  rapid Webb  concommitant  1 63  changes  i n swimming  length during The to  on  water  dependency might suggested  by  temperature decrease  same  and  the  water  form  the  7.4-7.8  the  arguments of  small  and  reactive smaller  size  large  forces  smallest  narrow  anteroposterior ratio  ratio  range  of  flexibility  are  appeared fry  greater  such a  the  result results  Alternatively,  d e c r e a s e s and  changes  ratio  increase  shift  of  the  number. velocity  increase  count  f r o m an  Reynolds between  i n Reynolds  resistive  would  and  occur at a  However, as n o t e d a b o v e , speeds  explanation.  to  performance  affect  lengths.  Perhaps  w i t h changes  o v e r a narrow  the  o f even  alternative  associated  important only  water  resultant  on R e y n o l d s  with burst  this  (as  notwithstanding,  an e f f e c t  this  associated  As  (compare  importance  propulsion,  l a r v a e argues a g a i n s t  Just  25C).  i n optimum v e r t e b r a l  i n the r e l a t i v e  count  15 and  Both  This  viscosity  The  sizes  viscosity  increases.  number  Vertebral  count  reflect  increases,  in  sizes.  i n order to maintain  paragraph  at higher temperature.  Reynolds  a  might  at  f r y lengths results  a shift  size  with  appeared  favour a r e l a t i v e l y  at smaller  previous  I f t h e change  number a n d  over  the  temperature  given  might  length class  of temperature  number.  high  mm  i n water  at higher temperature.  in  size  at small  decreases.  at a given s i z e  i n these experiments  a  ratio  with methylcellulose).  resistance  in f l e x i b i l i t y  at l e a s t  viscosity  seen  at  count  at a given  by c h a n g e s  experiments  was  As w a t e r  ratio  temperature,  increases,  in  count  be e x p l a i n e d  kinematic  effect  optimum v e r t e b r a l  these stages.  optimum v e r t e b r a l  depend  gradient  style  the  only  the changes in  range  in  vertebral of  Reynolds  1 64 number. have is  Or, the r a t i o s  been a b s e n t  ratio  predominant  of  results  determining  to caudal  sizes,  t h o u g h somewhat h i g h e r between  the  propulsion. vertebral the  of  ratio on  girth)  over  a  those of  these  the  ratio  importance i n range  of  a t R e y n o l d s numbers  a s s o c i a t e d with  resistive suggested  or  above  of  gradients in  that  narrow  be  sizes.  i s of fundamental  swimming o c c u r s than,  may  larger)  indicate  in  v e r t e b r a l count  longitudinal  study  vertebrae  The e x p l a n a t i o n s  optimum r a t i o  obviously  in this  predominance  count  in  (especially  swimming p e r f o r m a n c e  At these  than  may  selection  sizes  other  variation  sizes  (because  extreme  i n determining  obtained  larger  studied  more  factors  a t t h e more e x t r e m e  abdominal  sizes.  these  longitudinal importance  flexibility  The  at  Alternatively,  (e.g.,  a t s m a l l e r or  from t h e p o p u l a t i o n s  never c o n c e n t r a t e d  populations).  optimal  a  fry near,  transition  reactive forces in for this  effect  of  on p e r f o r m a n c e , and f o r t h e d e p e n d e n c y o f fry  length  highly speculative.  and  water  speeds  f r y o f v a r i o u s l e n g t h s and v e r t e b r a l numbers a r e n e e d e d  before  Genetic  explanations  control  of  c a n be  the  analyses  are  at burst  more d e f i n i t i v e  Kinematic  temperature,  suggested.  ratio  of  abdominal  v e r t e b r a l c h a r a c t e r of s e l e c t i v e  importance  to  caudal  vertebrae The be  not the a b s o l u t e caudal  number  of v e r t e b r a e ,  abdominal  to  vertebrae.  suggested  f o r the g e n e t i c c o n t r o l  o f a b d o m i n a l and t h e number  of  Two  to  but r a t h e r the r a t i o of simple  of t h i s  caudal  appears  models  character.  vertebrae  may  can  be  The number each  be  1 65 controlled  by  separate genes.  disequilibrium,  the expected  class  i n a randomly mating  of  f r e q u e n c i e s of  the  caudal  Alternatively, abdominal  genes.  of  any  p o p u l a t i o n i s then  or l i n k a g e  vertebral simply  the  count product  t h e c o r r e s p o n d i n g numbers o f a b d o m i n a l  the to  (model  1).  total  number  is  the  number and  of v e r t e b r a e  c a u d a l v e r t e b r a e may  Then, t h e e x p e c t e d  (ratio) total  frequency  pleiotropy  and  vertebrae:  p(a+c)=p(a)p(c)  of  A s s u m i n g no  product the  frequency of  frequency  the of  be of  and  the  determined a  given  frequency the count  of  separate  count  the  class  by  ratio  class  corresponding  g i v e n the  total  number: p(a+c)=p(t)p(a+c|t) The the the  two  models a r e  Holden  of a b d o m i n a l  threshold  character.  distributed  w i t h the  vertebral  assumed t o be abdominal total  to  Liability  same mean  count  and  classes.  mid-points  and  thus  differ  is  assumed  are  the  among  2 i s f i t t e d only to t o t a l  be  to  be  of  be  0.8805 total  2, a  normally in  a l l  liability  are  ratios  of  example, among f i s h w i t h seen:  count  to  observed  31  15/16=0.9375  AV/CV,  Thresholds  between  0.7729.  Assumed  13/18=0.7222 AV/CV. to  In model  deviation  Thresholds  For  39.  groups of  assumed  standard  between  caudal vertebrae.  AV/CV,  is  in control  In T a b l e  to caudal vertebrae  c l a s s e s a r e assumed  thresholds Model  the  2).  f i t t e d to the counts  vertebrae, three classes  14/17=0.8235 these  (model  Lake p r e d a t i o n e x p e r i m e n t s  ratio  total  where t=a+c  and  vertebral  count  classes.  c l a s s e s w i t h t h r e e or  more  Table 39. F i t s of two models for the genetic control of the ratio of abdominal to caudal vertebrae to Counts observed in control groups of Holden Lake predation experiments. Contributions to chi-square are shown Including only classes to which both models are f i t t e d . A l l chi-square probabilities are less than 0.05 . Parental Group A  B  C  All  1.4 -44 .2  -9..6 -22 .8 2. 3  0 .5 -26 .9 1.3  -8 . 1 -95 .8 2 .6  13..6 26. 8 23 . .7  6 .9 26 .2 32 .6  28 . 4 99 .2 97..2  -2.. 1 -15..4 2..9  1.. 8 -23 .7 1 ..9  -0,.4 -73 . 1 17 .4  Observed - Expected: M1: TV=30  14/16 13/17 Other  TV = 31  15/16 14/17 13/18  TV=32  15/17 14/18 13/19  M2: TV=30  14/16 13/17 Other  N/A  -1.5 -2.2 3.6  10.2 •10.5 0.3  16.0 -20. 2 4.2  TV = 31  15/16 14/17 13/18  2.7 13.3 •16.0  4.2 8.6 •12.8  0. -0. -0.  3.3 44 .0 -47 .4  TV = 32  15/17 14/18 13/19  •10.2 1 .4 8.8  •16.4 16.3 O. 2  •14. 15. -0.  -49.6 36.6 13.0  M1 M2  123 .6 18.6  134 .3 14.5  80.2 18. 1  354.2 73 .6  TV = 30 31 32  0.7995 0.7747  0.7929+ 0.8149 0.7975  0.8233 0.8050 0.7948  Ch1-square  Abd/Caud  8. 2 44 .9 40 .5  -o  .7 -34. .0 1 1.8  0.8180 0.8113 0.7884  Abbreviations: M1=Model 1, M2=Model 2, TV=Total vertebrae. Abd/Caud=abdom1nal to caudal ratio In continuous units of l i a b i l i t y , estimated separately for each TV. + N<50  167  ratios  AV/CV.  deviations used  Weighted  in l i a b i l i t y  i n model  calculated  count  of b o t h  models  1 depart  counts  do  of model 2.  those  a r e e x p l a i n e d by  vertebrae  and  departures  cannot  pleiotropy  These  be  units  this  compared These  ratios in this  expected  are  the  favour  number and  used  this  correlation than  an  two  population  to  environment,  are  from  the  the  this  any  39).  simple  results  i f the  On  environmental  two  be  observed  were  1  reared  in  with  an of  Thus,  between  a  or  in  32 the  14/18,  independent. f o r i n the  selection  ratio. in  31  and/or  were  total  continuous  increase  correlation  These  involving  with  14/17  31  explained.  (in  fish  traits  presumably or  ratio  from  hand, most  so  sometimes s e l e c t e d  III).  pleiotropy one.  fish  the o t h e r  can  ratios  that are  correlation  (i.e.,  of  hypothesis  Among  abdominal / c a u d a l  analysis  observed  w i t h more e x t r e m e c o u n t s .  /caudal  (Part  the  of model  a negative correlation  (Table  expected  vertebral in  class  In a l l c a s e s ,  from  excess  mean a b d o m i n a l / c a u d a l  abdominal  to those  groups.  observation  correlation  of  observed  disequilibrium. from  liability)  frequencies  an  indicate  number and  vertebrae,  standard  count  Most d e p a r t u r e s  e x p l a i n e d by  of model 2  of  and  significantly  much more w i d e l y  of t h o s e  linkage  departures  vertebral  wild  deficit  or  departures  means  f o r each t o t a l  frequencies in a l l control  of model  observation  the  depart  predictions than  of  2.  Predictions observed  averages  would  between Since  common reflects  be  total  the  fish  laboratory a  genetic  linkage disequilibrium) rather  168 Variation  a l s o appears  which count c l a s s if  total  (14/17 or  vertebral  independent.  to  and  v a r i a t i o n may  p a r e n t s were c o l l e c t e d J u l y parents  August  10).  variation  among  variation  in  (Swain and  Lindsey  variation  in  variation  could  selection  Seasonal  genetic an  Since is  most  examination  Cheverud  (1982) s u g g e s t e d  related  traits  respect  to  should  genetic  reflect  developmentally  and  processes.  preliminary, functionally  and  of  (A C  genetic seasonal  age  also  among  of  Atchley  of  be  parents seasonal  selection,  al.  t h e m s e l v e s be that be  this  but  the  of  and  highly to He  find  suggested  genetic  vertebral  A quantitative  the  c o r r e l a t i o n between t h e s e correlation  genetic  between  with a genetic traits  analysis  in  that  this  and  among  through here  are  integration  response  i s needed t o  traits, them.  an  traits  reported  with  such  correlations  results  related  functionally  integrated  Although  consistent  to  selection.  independent  they are  responses  responses to  functionally the  been  However,  failed  evolution  has  1982).  developmentally  relatively  factors,  traits  correlated et  selection.  environmental  4-5,  effect or  were  variation  reflect  f a v o u r e d by  among macaque c r a n i a l t r a i t s .  might  genetic  an  correlations  may  of  or  expected  ratio  August  variation could  in  adaptive.  correlations  only  parents  groups,  count  genetic  stochastic  seasonal  t h e r e may  1981;  failure  represent  1986a,b).  (Falconer  association  /caudal  B  groups  than  abdominal  environment  be  towards  parental  prefertilization  which  Most work on directed  24,  parental  the  among  14/18) i s more f r e q u e n t  number  This  occur  to  estimate  to  look  for  Further  work  is  an also  169 needed  t o examine t h e  significance these  of any  1.  pleomerism. appeared  described In  large  1974;  G.  suggest  Thus,  offspring  1974;  selection small  vertebral  of l a r g e  females  (Fig.  explanation operates  offspring  of  large  exposed  to  example,  i t cannot  and  count  large  selection  at small  sizes,  larger  1972;  eggs t e n d t o p r o d u c e  large  yolk  might  eggs  sizes.  (Fowler  complete  absorption  (Fowler  Beacham e t a l .  face  less  1985).  exposure  c o u n t s a r e f a v o u r e d than would  23).  I f s o , h i g h e r c o u n t s would large  requires on  to  those  tend  females, lower c o u n t s  small  o v e r l a p between  vertebral  and  selection  selection  required  large  females  of  caurinus,  for  to  i n those  females.  selection  which  between  explanation  count a t s l i g h t l y  W a l l a c e and A a s j o r d 1984;  a t s i z e s when low  This  large  and  at  favoured in o f f s p r i n g small  an  a c u l e a t u s and M.  1981),  b o t h a t h a t c h i n g and Gall  of  adaptive  i n the c o r r e l a t i o n  females tend to produce  Kazakov  1972;  be  both  here  t o f a v o u r f r y w i t h a low  fishes,  fry,  possible  among p o p u l a t i o n s  those with a higher v e r t e b r a l  Gali  of  seasonal v a r i a t i o n  and  Pleomerism  Results  In  basis  traits. Variation  and  existence,  small  females  (referred  explain females  number  to  pleomerism  appears  to  occur  are  if a l l  f a v o u r s lower v e r t e b r a l  overlap  and  h e r e as  are recruited  the s i z e s those first  at at  which  potentially  'recruited'). offspring  at s i z e s numbers.  which  of  For both  below t h o s e a t However,  i n both the s p e c i e s  the  studied  1 70  Figure the  23. A model e x p l a i n i n g p l e o m e r i s m . size  when f r y a r e f i r s t  predation,  i . e . when  d e v e l o p e d . V,,  and  potentially  Recruitment s i z e i s exposed  f r y a r e free-swimming are f r y with  to selective  and v e r t e b r a e a r e  N o r N+1  vertebrae.  LENGTH  172 here. fry  The  s m a l l e s t modes i n s i z e  collected  selection  low  selection  vertebral appeared  i n peamouth chub f r y a t  first  developed Selection  even at  Holden Lake o v e r l a p p e d  favoured  Similarly, (44)  from  if  sizes  small  o p e r a t i n g on of b o t h  below t h o s e Large  eggs  numbers to  just  favour  those  the  l a r g e and  at which  eggs  (Wallace  may and  f r y might  selection  Aasjord  If fry is  ratio  of  not  here,  few  to caudal  occur  as  pleomerism  seen  i n both  other  inverse correlation  will  but  from  from  vertebral  count  when v e r t e b r a e  result  in  favours  were  pleomerism  are  recruited  low  vertebral  growing  If  f r y than  differences  from  vertebral  in  s m a l l or  large  numbers  will  l a r g e eggs than  data  selection  evidence  i n G.  operating  in  operating aculeatus  directly  rather to s e l e c t i o n vertebrae.  In  on  those  i s expected  the  between  i f most v a r i a t i o n  i s that i t the  the  ratio  the  If t h i s  o n l y when t h e  i n the  total  the  number  result  ratio  correlated.  to t e s t and  total  aculeatus,  stickleback populations  are a v a i l a b l e  the  the  G.  inversely  on  o p e r a t i n g on  fry length increased.  number o f v e r t e b r a e a r e was  but  the  selection  vertebrae,  correlation  An  to  r a t i o decreased  total  a low  eggs.  hatching,  a g e n e r a l one,  the  fry.  f r y produced  i n f r y produced  small  of a b d o m i n a l  optimum  between  pleomerism does r e s u l t  related  number  is  favoured  soon a f t e r  which  these  1984).  length increases, higher  as  from  at  in  p r o d u c e more r a p i d l y  eggs d e c r e a s e  produced  sizes  small females  growth  t o be  the  stickleback  (31)  sizes  length-specific  tend  with  of  i n these f r y .  offspring  numbers.  distributions  and  Such a studied  i t s generality. total  number  i s produced  by  1 73 variation been  i n the  caudal  observed  (Lindsey  in  1954),  number.  the  This pattern  paradise  fish  i n t h e medaka O r y z i a s  i n R i v u l u s marmoratus  (Swain  of  aculeatus  by  environmentally region  (i.e.,  variation pattern seen  most  the  the  few for  ratio  the  inverse  occurs the  because with  than  are of  larger the  ratio  with  and  capelin  males tend  British  Columbia I can  to and  abdominal  while  inherited  the  that  He  cited  males reach In  size  fail  r a t i o AV/CV i n t h e s e  a  few  the  fact does  should the  degree on  the  and  to  be  the  exhibit strong  groups.  instances  l e n g t h s and shark  the  caudal  show a  t h r e e examples.  larger  to  ratio  number d o e s not  in  in  depend p a r t l y  the  that  is  number, and  between  groups  Thus,  If pleomerism  adult  should  most  the  abdominal  total  pleomerism  some  of  maximum  f o r the  females.  females;  Newfoundland.  examined.  Lindsey  population  region.  total  sexes.  do  spine),  i n the c a u d a l  and  (1962), in  has  opercularis  In t h e  the  (1975) n o t e d  genus E c s e n i u s ,  females males  so  between t h e  vertebrae  the  Perhaps  correlation  Lindsey  anal  inverse correlation  number.  p l e o m e r i s m do  occurred  cases  than  1979).  to produce pleomerism  correlation  for this  s t r e n g t h of  of  of  which a group e x h i b i t s  total  the  expected  from s e l e c t i o n  stronger  to  (Ali  Lindsey  variation  anterior  of v a r i a t i o n  vertebrae,  to  induced  a p p e a r e d most m a r k e d l y  in  result  studied  variation  Macropodus  latipes  1974), and G.  of  pleomerism In  blennies  have  Etmopterus  more  spinax,  have more v e r t e b r a e  than  males.  Mallotus v i l l o s u s  tend  t o be  larger  than  females  in  than  females  in  have  more  Murmansk,  offer  two  vertebrae but  fewer  explanations  for  Finally,  differences  than  in  174 vertebral  number between t h e s e x e s .  egg-carrying to  caudal  studied in  capacity  females  is  period  correlated).  and of  Schultz rising  d e p e n d e n c y may number  produced  or  the  spawning  (Harrington  embryos  is  For  the  sex d e t e r m i n a t i o n  number w i l l  incubation  number.  This  pleomerism.  protracted  this  temperature  and  in vertebral  in size  in  the  of  Atlantic  females  temperatures;  of  vertebrae temperature,  tends to produce tend  tendency  operating  factors,  sex d e t e r m i n a t i o n o r s e l e c t i o n  to  might  for vertebral  Additional  in  1984;  earlier  be  number  on  reinforced (see  larvae  explanation such as  the  or  produced  may  be  in  differences If  counts  higher  mean  by s e a s o n a l  below).  f r y soon  f o r most  after  instances  temperature-dependent  for a high proportion  females,  in  season  high vertebral  have  are  females  be e x p e c t e d between t h e s e x e s .  provide a sufficient  to caudal v e r t e b r a e  a  most a r e p r o d u c e d  incubation  sex w i l l  in selection  may  by  also  temperature  embryos, t h e l a r g e r  Conover  i s over  example,  number  count  number a r e  thus experience a l o n g e r growing  In summary, s e l e c t i o n  of  both  than males because  also affected  vertebral  abdominal  vertebral  1968,1971;  i n c u b a t e d a t lower  Since  of  total  temperatures,  sexes.  s e a s o n and  1984).  hatching  the  When spawning  a difference  larvae  larger  (Conover  variation  and  i n some f i s h e s ,  falling  the  among  t o be  vertebral  favour a lower  Menidia menidia, a higher proportion  tend  in  would  Second,  for greater  In t h e s t i c k l e b a c k p o p u l a t i o n s  proportion  1986).  produce  between  silverside  low  the  temperature-dependent  Sullivan  in  selection  (since  selection  favour a high p r o p o r t i o n  vertebrae in females.  here, such  inversely  might  First,  required  of to  abdominal explain  175 instances  of  pleomerism  between t h e s e x e s .  o p e r a t e on v e r t e b r a l number a t a d u l t need  not  failure  be  2.  between  Jordan's  species  (Ray  poikilotherm  larval  a n d maximum a d u l t  latitudinal reflection Lindsey  tends  and  greater  clines  in  showed  In f a c t , the reflect  a poor  sizes.  demonstration  Labridae.  These  vertebral  number,  maximum  body  lengths  in  might body  marked  latitudinal  be  numbers  purely  a  However,  be a t t r i b u t e d  length.  The  by t h e w r a s s e  latitudinal cline  of  (pleomerism),  size.  r u l e cannot  within  1966)  mean v e r t e b r a l  was p r o v i d e d a  Jordan's  waters, both  i n maximum body  f i s h e s showed no  clines  for  (Lindsey  number  Jordan's  of t h i s  but  families higher  that  sought  i n colder  vertebral  clines  be  Since  latitudinal  to l a t i t u d i n a l  striking  within  with  of these  may a l s o  t o be l a r g e r  vertebrates.  (1975)  selection  rule  1960)  associated  solely  such  to e x p l a i n pleomerism.  functional explanation  r u l e . , Body s i z e  are  but  o f some g r o u p s t o e x h i b i t p l e o m e r i s m m i g h t  correlation  A  hypothesized  sizes,  S e l e c t i o n may a l s o  in  most family  cline  maximum  in body  length. However, J o r d a n ' s clines adult larger  in sizes.  egg a n d l a r v a l Like  in colder  water  adult  waters  presumably a t l e a s t attributable  r u l e might  sizes, (e.g.,  partly  to a direct  temperatures  sizes,  during  be a t t r i b u t a b l e t o rather  than  t o those  egg a n d l a r v a l Marshall  genetic,  modification  1953).  but  may  latitudinal i n maximum  s i z e s tend  For  be  These c l i n e s a r e also  be  o f egg a n d l a r v a l  development.  to  example,  partly s i z e s by i n the  176  pupfish  Cyprinodon  females  held  Similarly, at  in  n.  nevadensis,  colder  colder  macrocephalus,  pallasi, 1974; 1977; and  Alderdice Salmo  of  species  Alderdice  and V e l s e n  salar,  Hamor  Murray  (1986) f o r an  numbers may  be  because  the  larger  exposure  to s e l e c t i o n  larvae  explanation requires  l a r v a e produced  the  i n warm o r  potentially  latitudinal  variation  Jordan's latitudinal  cold  exposed in  rule clines  might  stringently size  may  in  in  waters  face  less  numbers  are  i n warmer the  waters.  sizes  those at  recruited  selection.  sizes  Beacham  colder  number and are  al.  Thus, h i g h e r  vertebral  waters  also  be  i n t h e body s i z e  that  unselective  Thus,  see  trend).  produced  Clupea  which  to  the  Examination  the  at  wrasses  of  would  of t h i s h y p o t h e s i s .  Predators  relatively  1929;  Peterson et a l .  o v e r l a p between  larval  which p r e d a t i o n i s s e l e c t i v e sizes.  low  to  Gray  i n these waters  smaller larvae an  larvae  Fonds e t  but  selection  o p e r a t e s on v e r t e b r a l  population  provide a test  1982;  produced  Again  selection  Heming  1977,  1977).  1971;  belone,  by  larger  trutta,  Forrester  Garside  a t s i z e s when  Gerking  produce  Belone  f a v o u r e d by  than  which  and  exception to t h i s  favoured, this  do  and  and  eggs a r e p r o d u c e d  (Salmo  1971;  Oncorhynchus tshawytscha,  vertebral  prey.  (Shrode  i n c u b a t i o n temperatures  hatching in a variety  Gadus  water  larger  prey  be  larger  of p r e d a t o r s i n t h e s e  attributable  of p r e d a t o r s .  depends both  on  r e s p e c t to the escape  size  The  prey  a r e v e r y l a r g e compared  with  the  partly  and  waters.  waters,  due  to  predator  to prey w i l l  be  performance  of  upon w h i c h s e l e c t i o n  in colder  extent  to  to  o p e r a t e s most the  larger  177 Water which  may  vertebral rates  temperature affect number.  i n these  affect  the  they w i l l of  selection or  over  a  which  selection.  least  effect  for  shift  recruitment  size,  the  D e p e n d i n g on how  these  higher  respectively. affects  here; of  is  range  favoured  by  decreases),  smaller  count  sizes  ratios). of  (2)  The  selection  f o r higher  ratios ,  how  overall  mortality  decreases  factors  Water  the s i z e  (or v i s c o s i t y  i s greater  (or decrease  otherwise a t net advantage.  t o reduce or  and n e t d i r e c t i o n  i t  not  Acceleration  vertebral  a t which p a r t i c u l a r  o r lower v e r t e b r a l  will  s i z e and t e m p e r a t u r e ;  much  i n temperature  temperature.  selection.  proportion  how  sizes  water  predation  number, b u t  number  reported  vary with  and  and  t o be f a v o u r e d a t s l i g h t l y  i n the r e s u l t s and  selection for  be e x p e c t e d  increases  factors  for vertebral  apparently  vertebral  of  a l l sizes,  number,  (1) whether t h e s h i f t  selective  either  vertebral  on t h e e x t e n t  potentially  increase  would  f o r h i g h and i n t e r m e d i a t e  rates  the  of t h i s  rates  temperature  mortality  in  over  of other  rates  increasing  of s e l e c t i o n  the extent  c o u n t s appear  i s suggested  a variety  direction  uniform  particular  of t h i s  increases.  or  viscosity also  As  depends on: as  if  predation  temperature  (at  rates,  net d i r e c t i o n  or  particular  extent  to increase with  influence  growth  increase  the  influences  F o r example, b o t h g r o w t h  are expected  Changes  also  that  is  and,  (3)  as temperature  interact,  a  decrease  c o u n t s a r e f a v o u r e d due t o an in viscosity)  could  numbers, o r w h i c h e v e r  favour  number  was  1  In  summary,  attributable in  latitudinal  to  clines  latitudinal  clines  also  influence  affect  selection  these various  polymorphic  spines,  of g a s t e r o s t e i d  number  presence  important  (e.g., or  variation  from  polymorphisms  i n some  respects.  functional  variation G.  no  obvious  (Moodie  of d o r s a l  1984a,b). other  at  spines  Selection  characters,  behavioural  traits  Blouw  polymorphisms,  and  those  is  in  effect  of  in addition  plates  or  dorsal  The  factors  number  within  spines).  vertebral  for  Particular fry  these  vertebral sizes  other numbers  because of a  performance.  functional  advantage  i s associated  a s t h e number  1972;  in Apeltes  quadracus  on  1984a,b).  be  and  genetically  in  Hagen these  correlated  1979; H u n t i n g f o r d  Secondly,  in  these  i s generally  supposed  or s e l e c t i o n  in  opposed  with  1973) o r t h e  (Blouw  Kynard  In  plates  p r e s u m e d t o a c t i n d i r e c t l y on  selection  to  of l a t e r a l  Hagen a n d G i l b e r t s o n  phenotype  supposed  conspicuously  characters  suggested  (Moodie e t a l . 1973; Hagen  often  pelvic  particular  i n a d i f f e r e n t circumstance,  phenotype  may  swimming  i s often via  each  and  that  involving  i n such c h a r a c t e r s  aculeatus  number  1981;  optimum  advantage  contrast,  temperature  but the net  fishes are  of  differ  be  number,  s i z e s , and  factors  numbers o f l a t e r a l  absence  i n maintaining  to  other  of m o r p h o l o g i c a l  populations  appear  of  be  populations  for a variety  to v e r t e b r a l  Water  might  i s uncertain.  within  Populations  variety  for vertebral  factors  Variation  a  number  i n egg and l a r v a l  the s i z e d i s t r i b u t i o n s of p r e d a t o r s .  viscosity  fit  in vertebral  78  other  t o be most  favour  of  one  by i n d i r e c t s e l e c t i o n i n  179 favour  of  the  may  of  advantage  be  other.  a b s e n c e may  be  (Reimchen  1980;  a d v a n t a g e of o p p o s e d by  of  spines  in  the  from  advantageous  1980a). forces  intrinsic  maintain  a  selection  stable at  another. one  and  number  variation annual  might  size  temperature which  of  rates).  That  coefficients selection Holden  size  could  influence  number  Lake.  will  in  with  of  optimum  cannot  by  be  at  that  by  or  predator)  hatching  of  growth r a t e s variation apparent  stickleback of  fry  rather  themselves event  that  selection  at  stringently for  the  Even  so,  seasonal operates  variation size,  or  number.  from v a r i a t i o n  from  the  but  size.  which s e l e c t i o n result  absence number,  greatest  spatial,  may  differences  unlikely  will  favour  the  o p e r a t e most  seasonal  number o f  Selection  the  balanced  i s s u g g e s t e d by  for vertebral  predation  selection,  i n the  i s optimal,  such s p a t i a l or occurs  on  predators,  (which w i l l  a particular  except  maintained  the  morphological  vertebral  type  pressures  optimal  Such v a r i a t i o n  distribution  on  fitness  is  of  indirect  selection  be  the  their  predation  from e x t r i n s i c  (e.g.,  exactly  overall  in  case  fry size  is  that  Or,  spines  while  invertebrate  vertebrate  not  and  selection  still  variation  stringently. size  of  More p r o b a b l y ,  vertebral  in  result,  polymorphism,  one  size,  the  selection  effect  These opposing  at  In  pelvic  predation,  advantage c o r r e l a t e d  a b a l a n c e between d i r e c t  f r o m an  avoiding  in avoiding  a behavioural  c i r c u m s t a n c e s of  p r e s e n c e of  1980,a,b).  spines  selective  the  vertebrate  in  Reist  (Reist  opposing  example,  in avoiding  pelvic  be  For  the  or most  in in  the water  size  at  and  predation  in  selection  differences between  in  sites  f r y with high counts  of  180 32 was most  s i g n i f i c a n t among f r y c o l l e c t e d  from  A, w h i l e  of  site  31 was most  season  from  selection  s i g n i f i c a n t among t h o s e site  B.  temporal  heterogeneity  genetic  variation  consideration Jayaker  About  vertebrae  fry  32 v e r t e b r a e .  expected  at very  small  (31 t o t a l v e r t e b r a e )  not  seen  in  the  Perhaps development potential  fecundity  survival due t o  proportions. be  fecundity  a  be  some  high  the  net  and  had  only  r a t i o of  expected sizes of  30  to  be  a s a r e most  f r y with  30  this  might  high  data  t h i s high  ratio  those  when a r a t i o o f an a d v a n t a g e  a t these  small  insufficient On  ratio,  be  the  sizes. for a  other  not  was  hand,  because  of  but r a t h e r because of g r e a t e r  abdominal  among t h e v a r i o u s  Haldane  to caudal  expressed.  to  variation  because  effect  theoretical  r a t i o of abdominal  f r y was  size,  in populations  in  'large'  majority  sparse  small  f r y with  at  are  ( s m a l l e r than  Thus, a d d i t i o n a l  maintained  variation  to  favour  Lake  was o p t i m a l ) , b u t s u c h  of these  advantage may  to  admittedly  maintain  1979).  and  However, t h e  sizes  s p a t i a l or  h a d an i n t e r m e d i a t e  t h e same  An a d v a n t a g e  i n the  can  1955;  Holden  (0.76),  a t about  0.82  greater  from  low c o u n t s  which such  Dempster  had an e x c e p t i o n a l l y h i g h (0.88).  selection  1953;  season  later  coefficients  a t h i r d of these  to caudal  vertebrae  the  with  collected  e t a l . 1976; Ewing  by s e l e c t i o n  vertebrae  of those  under  selection  ( e . g . , Levene  favoured with  in  14% o f f r y c o l l e c t e d  vertebrae. abdominal  Conditions  in  i n p o p u l a t i o n s have r e c e i v e d much  1963; H e d r i c k  About  i n favour  early  of  of  caudal  in vertebral spatial  differential  phenotypes.  ratio  in  body  number may  and  temporal  survival  and  181 Developmental A  single  noise  genotype  developing  environment  may  produce  in  This  is clearly  embryos.  two  self-fertilizing  cyprinodont  Harrington  1972;  Harrington  I986a,b),  and  This  variation  must  or developmental n o i s e  and  from  occurs random  (Waddington  often considered  t o be  t h e most  t h e many r e c e n t  s t u d i e s of  or genomic c o a d a p t a t i o n  (e.g.,  and  Felley  Schultz 1985).  in  genotypes producing  environment  may  1983;  be  or  fit  more than  affected  fit.  This  effects  et a l .  there  of  the  levels  of  stability 1985a,b;  environmental opposite  phenotypes those  is  1984,  is  the  by  developmental  developmental  coefficients,  two  more  on  Leary  However, when  selection  development  1957).  heterozygosity  true:  ' a c c i d e n t s ' of  greatest  behind  and  species.  with  rationale  (Lindsey  in outbreeding  those  are  the  Lindsey  (i.e.,  noise  of  Swain and  is least  stability)  heterogeneity  clones  expression  such developmental  Graham and  1976;  external  v e r t e b r a l numbers  R i v u l u s marmoratus  Crossman  G e n o t y p e s whose p h e n o t y p i c  Angus  single  demonstrated w i t h i n  also  result  a  o r more d i f f e r e n t  fish  presumably  in  in  producing  may  be  a  given  a  single  phenotype.  Consider B and and  f o l l o w i n g simple  C p r o d u c e p h e n o t y p e s P and  (0,1),  strategies, a  the  respectively. each p r o d u c i n g  'mixed' s t r a t e g y .  v and  1-v.  Q  in proportions  Genotypes a  single  Environments  In e n v i r o n m e n t  ( h a p l o i d ) model.  1,  the  A  and  C  (1,0),  represent  phenotype, while  1 and  2 occur  Genotypes  with  B  (p,  A, 1-p)  'pure'  represents frequencies  f i t n e s s e s of p h e n o t y p e s P and  Q  182 a r e F a n d 1, r e s p e c t i v e l y ;  i n environment  2, t h e y a r e 1  respectively  The r e s p e c t i v e  fitnesses  A,  (F>1,  G>1).  B a n d C a r e F, pF+1-p, a n d 1 i n e n v i r o n m e n t  and  G  in  environment  temporal,  the  geometric  mean  1977). A:  F  B:  (pF+1-p)  are  heterogeneity i s  one  Jayaker  with  greatest  1963, G i l l e s p i e  of the three genotypes a r e :  (p+G-pG)'"^  V  shown  near  under  in Fig.  which  each of the genotypes  24, f o r v a r i o u s  t e n d s t o be t h e most  between  especially  of  and  the  p+G-pG,  v  strategist  respect  (Haldane  mean f i t n e s s e s  conditions  fitness  is  is  of genotypes  1, a n d 1,  environmental  G,  G" V  The  mixed  If  f i t genotype  fitness  Geometric  C:  fit  most  2.  and  the  phenotypes  levels  f i t when  are great  0.5).  Levins  to the f i t n e s s  genotypes  considered  here),  (as opposed  using  The  differences  in  environments,  i s high  (1962) r e a c h e d a s i m i l a r  of p o p u l a t i o n s  o f v and p.  i n both  when e n v i r o n m e n t a l u n p r e d i c t a b i l i t y  i s t h e most  (i.e.,  conclusion to the  a qualitative  v  with  fitness  geometric  analysis.  Random v a r i a t i o n and  Cooper  strategist greatly  (1982) i s most  between  environmental this  one  may a l s o have  shown t h a t  between  clutches.  i n t h i s case a l s o  f i t ( i n a h a p l o i d model) when phenotypes  unpredictability  case,  occur  analogous  in  Kaplan t h e mixed  fitness  differs  a  given  environment  i s high.  (They  considered  and only  t o t h e c a s e F=G=6, v=0.5 i n t h e model  183  Figure  24. C o n d i t i o n s  optimal mixed  when t h e r e  strategist  the curves  i s temporal v a r i a t i o n  i s t h e most  in selection.  f i t under c o n d i t i o n s  and t h e p u r e s t r a t e g i s t C l e f t  Details  in text.  are  The  between  f o r a g i v e n p, t h e p u r e s t r a t e g i s t A below  lower c u r v e , curve.  under w h i c h mixed o r p u r e s t r a t e g i e s  the  of the upper  181+  F  185 described  here).  variation  in  though data Lindsey  There  the  phenotypic  to test  selection.  stringent  The c o n d i t i o n s under  in than  conditions. conditions  which  those  of  under w h i c h  important  random  ( b u t s e e A l i and  stability  stability.  developmental  stability  adaptation temporal number  on to  adaptation,  observed  been  in  adaptation  to t h i s  Finally, phenotypic  the  liability,  The i s both  is  that  under  by s e l e c t i o n of  lower  over  those  an  optimal  Spatial  coefficients  and  for vertebral  developmental  vertebral  low  developmental  represent  The  some  relatively  indicate  rather  above. of  less one,  genotypes with  instances  selection  expression  be  t o be  in a haploid  unpredictability.  suggested  noise  number  may  be  an  respect  t o l e v e l of  heterogeneity.  expression.  thresholds  expression.  in  distinction  threshold t r a i t .  here  not  but  environmental  heterogeneity has  may  will  d i s c u s s i o n to c a l c u l a t e these  be f a v o u r e d Thus,  relevant  i n the p o p u l a t i o n  are l i k e l y  heterogeneity,  will  the  strategy  i t i s optimal  point  environmental  higher  constraints  a  an i n t e r b r e e d i n g p o p u l a t i o n  The  developmental  with  of  v e r t e b r a l number,  be m a i n t a i n e d  i t i s beyond t h e scope of t h i s  with  of  of i n t e r b r e e d i n g i n d i v i d u a l s ,  i s which s t r a t e g i e s w i l l  maintained  a  expression  sort  1974, p . 9 6 1 ) .  question  but  for this  f o r i t s existence are sparse  In a . p o p u l a t i o n  by  i s no e v i d e n c e  should  V e r t e b r a l number  Such t r a i t s that  be made w i t h  impose  underlying genetic  have  i s u s u a l l y thought  an  underlying  discontinuities continuous  and e n v i r o n m e n t a l  continuity  on t h e i r  variable,  of as  visible  termed  in origin,  the  and c o u l d  186 in  p r i n c i p l e be  In  the  of  embryonic  studied  c a s e of  available  a metric  and  incorporation  Developmental  noise  number  is  to  of  of  relevant  underlying  effects  developmental  at  the  the  stability.  noisiness  simply  reflect  liability  whole v a l u e s )  the  of  the  shifts  (i.e.,  i n the  (Swain  in  Phenotypic  plasticity  p h e n o t y p e p r o d u c e d by Phenotypic  when  strongly  on  discussion i s the  (1)  not  may  by  rates  numbers o f  cells  above, w h i l e  more r e l e v a n t or  genomic in noise  necessarily  at  be  defined  plasticity  the  relative  may  and  i s now  examples  has  possible long  as  the  extent the  may of  between  adaptive  the  studies  of  i s the  attention  phenotypic  in  and  natural depends  (3)  of  f i t (Levins phenotypic  (Bradshaw animals.  plasticity  the  environmental  most  in plants  which  environment  chosen,  significance  been e m p h a s i z e d  by  phenotypes  (2)  be  to  developmental  favoured  f i t n e s s of  cannot  receiving considerable include  they  number  which phenotype  plasticity  of  differences  between t h r e s h o l d s  be  conditions,  individuals  determine The  on  level  instead  vertebral  the  questions  the  factors  1968).  at  coadaptation  i s c o r r e l a t e d with those  1963,  vertebral  to  developmental environment that  Arnason  noise  indicate  liability;  mean  and  observed  a g e n o t y p e d e p e n d s on  environmental  experienced  r e f e r to  (Lindsey  of  mean l i a b i l i t y the  or  1981).  1987).  plasticity  selection  level  underlying  shifts  could  somites  Differences  Phenotypic  environment.  the  heterozygosity  o b s e r v e d v e r t e b r a l number do in  into  liability  of  (Falconer  differentiation,  1981).  level  character  v e r t e b r a l number, l i a b i l i t y  growth  for  as  of  life  1965), Recent history  187  traits  in  the  snail  temperature-dependent menidia in  the  (Conover  The water  sex  1984),  the e f f e c t  n_.  spectabile  elodes  determination  and  f i s h e s Cyprinodon  and E t h e o s t o m a  Lymnaea  developmental U-shaped the  relative  on  water  1970).  fitness  water  may  1977),  and  are  larval  in fish  during  produce  Females  relatively  large  large  above).  As a r e s u l t  of t h e s e e f f e c t s ,  number (or  to developmental  viscosity)  a particular could  also  either  of  temperature factors  and  the e f f e c t of  on  of  and  U-shaped  relatively  cold  (see  number  selection  tend  temperature over  latter  which effect colder  (see above). to  would  The  developmental  d e p e n d on latter  suggests  to  vertebral  numbers a t  on h a t c h i n g s i z e .  responses  references  range  This  of f a c t o r s  usually  should  the s i z e  Gerking  water  response of  magnitude of t h i s  temperature  and  However, w a t e r  vertebral  f a v o u r e d by  the r e l a t i v e  of water  declivous  on a v a r i e t y  early  cold  selection  optimal.  or  depends  ( S h r o d e and  h i g h e r or lower v e r t e b r a l  response actually  is  to  the  hatching  a declivous  temperature.  number  temperatures, depending pattern  at  on  be a d a p t i v e , s i n c e  in  eggs  apparently affects  vertebral  favour  larvae  produce  1977)  number  numbers a l s o  held  relatively  that  size  declivous  embryo d e v e l o p m e n t  embryos d e v e l o p i n g i n r e l a t i v e l y  genotypes  may  vertebral  produce  favour  on egg  embryos d e p e n d s  either  This p l a s t i c i t y  stages.  Menidia  ( S h r o d e and G e r k i n g  usually  of d i f f e r e n t  temperatures  free-swimming  fish  P a t t e r n s of response of v e r t e b r a l  temperature  (Fowler  the  1985),  1984).  number o f v e r t e b r a e p r o d u c e d  temperature.  in  of t e m p e r a t u r e  nevadensis  (Marsh  (Brown  these  effect  and  The  ubiquity  that  selection  188 normally  f a v o u r s one  The within  variable  pattern  inverse  temperature  relation  among  differences  among  combination  of  overshadow  alone.  numbers  and in  are  Parental number  may  of  temperature temperatures,  the  size due  ranges  patterns of  before  When p a r e n t s  offspring  apparent  i f p a r e n t s were h e l d a t t h e r e a r i n g  Just  of  offspring more  i n an  vertebrae produced  vertebrae (Swain  and  of  aculeatus,  an  on  effect  after do  the  at  variety to  one of  rearing  a declivous  response  temperature  of  the  effect  of  number, p l e o m e r i s m  may  size  the  comm.).  analogue  of p a r e n t a l  in  in offspring.  or  age  In R.  on  marmoratus,  t h e o n s e t of b r e e d i n g t e n d t o  those produced  L i n d s e y 1986b). large  though  vertebral  produced  long  than  breeding G.  r u l e has  temperature  have an a n a l o g u e number  Lindsey, pers.  as J o r d a n ' s  developmental  even  a  response  would r e s u l t  (C.C.  conditions.  held  at  might  offspring  produced  within  affects  are  temperature  their  be  influences  ( D e n t r y and L i n d s e y  reared  U-shaped  a  typically  response  fertilization  L i n d s e y 1986a).  to  particular  experimental  in offspring  an  due  when  of  water Perhaps  to environmental  produced  their  rule). size  t o the  and  environmental influences  temperature  and  temperature  number  hatching  artifacts  vertebrae  Swain and  in  U-shaped  be  holding  vertebral (Jordan's  optimum  Alternatively,  populations  between  populations  genetic  incubation  o r U-shaped) i s i n c o n t r a s t  populations  differences  vertebral  patterns.  of response t o  populations (declivous  typically  1978;  o f t h e s e two  soon  Similarly,  after in  females tend to produce  have  the onset of a  population  offspring  with  189 more v e r t e b r a e effect  is  themselves Large  than  presumably appear  females  above), offspring  but  small  tend  large or  tend  result  from  counts  differing  selection  of d i f f e r e n t  do n o t  this  or  female  age  thus  vertebral  they  may  be  large  females  offspring,  higher  by s e l e c t i o n effect  number may  effects  between t h e eggs o f  Since  large  and  Instead,  However, t h e y  i n egg s i z e .  and  size  t o be p r o x i m a t e  Thus, t h e o b s e r v e d  pressures  population.  between  ( L i n d s e y and A l i 1 9 7 1 ) .  eggs  ages or s i z e s .  l a r g e females  i n f i s h e s (see  s h o u l d be f a v o u r e d  offspring  This  t o produce l a r g e eggs  of d i f f e r e n c e s large  data).  in  ( o r young o r o l d ) f e m a l e s .  effects  on  vertebrae  biochemical differences  (or o l d ) females.  size  since  number a r e n o t l i k e l y  i n egg s i z e  t o produce  vertebral  more  relationships  or l a r g e  ultimate  t o have  vertebral  (unpublished  non-genetic,  often  of d i f f e r e n c e s probably  do s m a l l f e m a l e s  i n o f f s p r i n g of of female  age  be an a d a p t a t i o n t o  o p e r a t i n g on o f f s p r i n g  of  parents  190  Literature  cited  A l d e r d i c e , D. 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