UBC Theses and Dissertations

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UBC Theses and Dissertations

Metavariation and long term evolutionary patterns Blachford, Alistair M 1984

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METAVARIATION AND LONG TERM EVOLUTIONARY PATTERNS by A L I S T A I R M. BLACHFORD B . S c . ( H o n o u r s ) Queen's U n i v e r s i t y ,  K i n g s t o n , 1978  A THESIS SUBMITTED I N PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department o f Zoology) We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e required standard  THE UNIVERSITY OF B R I T I S H COLUMBIA November 1984 ©  Alistair  M. B l a c h f o r d ,  1984  In p r e s e n t i n g  this  thesis i n partial  f u l f i l m e n t of the  r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y of B r i t i s h Columbia, I agree that it  freely  the Library shall  a v a i l a b l e f o r r e f e r e n c e and study.  agree t h a t p e r m i s s i o n f o r extensive for  financial  copying or p u b l i c a t i o n of t h i s  gain  Department o f The U n i v e r s i t y o f B r i t i s h 1956 Main M a l l  V a n c o u v e r , Canada  (3/81)  1Y3  It i s thesis  s h a l l n o t be a l l o w e d w i t h o u t my  permission.  DE-6  thesis  s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e h e a d o f my  understood that  V6T  I further  copying o f t h i s  department o r by h i s o r h e r r e p r e s e n t a t i v e s . for  make  Columbia  written  ii  ABSTRACT  By  definition  systems  "adaptability"  t o cope w i t h change.  production  of  production  genetic  is  selection, adaptability. processes  of  in maintaining  important  for persistence  is  important  based  on  short  effective  rate  properties should  term  favored  be  time  requires  that  the  variation  not are  tailor known  with genetic  to  modify  and s e c o n d a r y s e l e c t i o n can  justified.  term. Genetic a d a p t a b i l i t y  t e r m , and  definitions increase).  of  If  i s ignored  fitness  "fitness"  selection",  s c a l e dependent.  properties  f i t n e s s , a s w e l l as p r o p e r t i e s  the short  d e f i n i t i o n s of the a c t i o n of allowed  does  i n the short  by n a t u r a l  living  i . e . unconnected  elements  immediate  in  of  view  of  term, n a t u r a l s e l e c t i o n 'favors'  important,  less  The  selection  i s not  ability  adaptability  production,  a c t on them, so t h a t v i e w  the  random,  genetic  variation  Over t h e l o n g e r  or  that  But many  Genetic  variation.  undirected  implies  is  (e.g. r e l a t i v e is  then  to  its  Currently prevalent  natural  i n models  selection  be  "the  definition short  should  term  not  be  t o hamper c o n s i d e r a t i o n o f t h e r o l e o f s l o w p r o c e s s e s i n  determining  long  term e v o l u t i o n a r y  A r e v i e w of explanations on n o t i o n s explanation  patterns  for  genome  size,  and  the  them, r e v e a l s t h a t most e x p l a n a t i o n s  of a d a p t e d n e s s of  in  patterns.  t o the s t a t e  genome s i z e p a t t e r n s  of  the  existing are  based  environment.  An  b a s e d on t h e r a t e o f c h a n g e  of environments i s proposed. I t i s hypothesized genome  is  new  the  i n v o l v e d i n r e g u l a t i n g v a r i a t i o n p r o d u c t i o n , and that  more DNA means slower This  that part of  hypothesis  production of a d d i t i v e is  simple,  general,  genetic and  variation.  testable,  but  r e q u i r e s more evidence. The q u e s t i o n  i s r a i s e d of whether genomes  might be  the  organized  to  facilitate  v a r i a t i o n production by n a t u r a l s e l e c t i o n .  adjustment  of  genetic  iv  TABLE OF CONTENTS ABSTRACT  i i  L I S T OF TABLES  v i i  L I S T OF FIGURES  v i i  ACKNOWLEDGEMENTS  ix  INTRODUCTION  1  PART ONE C h a p t e r One Some B a s i c  Concepts  3  "Random" v e r s u s " D i r e c t e d "  3  Randomness a n d S c a l e  3  K i n d s of V a r i a t i o n  4  Time S c a l e s  and N a t u r a l  Selection  5  C h a p t e r Two S e l e c t i o n of V a r i a t i o n Patterns  Production  i n V a r i a t i o n Production  M o d i f i e r s of v a r i a t i o n production S e l e c t i o n Mechanisms Secondary  selection  processes  9 13 14  The L a y z e r M o d e l  17  A time s c a l e s c o n s i d e r a t i o n  20  Di s c u s s i o n Chapter  7  22  Three  Metavar i a t ion An o p t i m a l  27 r a t e of v a r i a t i o n p r o d u c t i o n  27  To t r a c k o r n o t t o t r a c k ?  30  Metavar i a t ion  31  Time s c a l e d e p e n d e n c e  32  V  When i s m e t a v a r i a t i o n The r e a l w o r l d  important?  i s multidimensional  V a r i a t i o n p r o d u c t i o n a n d g e n e t i c memory  33 40 42  PART TWO Chapter  Four  Genome S i z e P a t t e r n s  44  The P a t t e r n s a n d t h e C - v a l u e P a r a d o x  44  The E x p l a n a t i o n s  47  Discussion  63  Genome S i z e a n d R a t e s o f E v o l u t i o n  65  A New E x p l a n a t i o n o f Genome S i z e P a t t e r n s  66  Support  f o r t h e Genome S i z e / V a r i a t i o n  Production Hypothesis Conclusion Chapter  67 70  Five  T e s t i n g the Ideas  72  Where t o Look  73  S p e c u l a t i o n on M e t a v a r i a t i o n S y s t e m S t r u c t u r e  73  E p i g e n e s i s and C a n a l i z a t i o n  77  On M e a s u r i n g G e n e t i c  78  V a r i a t i o n Production  Suggested Experiment  79  Previous Experiments  83  M e t a v a r i a t i o n as E x p l a n a t i o n  i n Two  Bandwagon T o p i c s  84  DISCUSSION P o p u l a t i o n - l e v e l Genetic ' V a r i a t i o n Production Old  Ideas  Memory  and E v o l u t i o n a r y P a t t e r n s  87 89 91  vi  SUMMARY  92  REFERENCES  94  APPENDICES I . F i t n e s s , P e r s i s t e n c e and Time S c a l e s II. III.  104  The F u n c t i o n a l H i e r a r c h y . , A c o m p u t e r game f o r e x p l o r i n g v a r i a t i o n strategies  108 production 119  vii  L I S T OF TABLES  TABLE 1.  Known m o d i f i e r s  of g e n e t i c  variation  TABLE 2.  Patterns  TABLE 3.  The r a n g e i n genome s i z e c o m p a r e d  10  i n genome s i z e  48  with  t h e minimum  and maximum f o r t h e t a x o n  TABLE 4.  Properties various  required  59  for persistence  under  environmental conditions  112  L I S T OF FIGURES  FIGURE 1.  Fitness  f u n c t i o n a n d two p h e n o t y p e  frequency  distributions  FIGURE 2.  Visual  19  description  a computer  of t h e i n i t i a l  simulation  r a t e s of v a r i a t i o n  FIGURE 3.  Results  t h a t compares  simulation  subpopulations d i f f e r i n g  FIGURE 4.  23  c o m p a r i n g two  i n r a t e s of v a r i a t i o n  undergoing d i r e c t i o n a l  The r e l a t i o n s h i p  differing  production  of a computer  production,  c o n d i t i o n s of  of a l p h a  l e v e l s of i n d i r e c t i o n  selection  24  and beta genes, and t h e  i n secondary s e l e c t i o n  38  vi i i  FIGURE 5.  Illustration  o f t h e amount o f v a r i a t i o n i n genome  s i z e among s p e c i e s  FIGURE 6.  A h i e r a r c h i c a l c o n t r o l system persistence-oriented  FIGURE 7.  45  Pictorial  of b i o l o g i c a l  strategies  1 15  d e s c r i p t i o n o f some o f t h e m o d e l ' s  parameters  120  FIGURE 8.  E x a m p l e r u n o f t h e s i m u l a t i o n model  125  FIGURE 9.  S i m u l a t i o n model o u t p u t : p o p u l a t i o n s i z e s over time  127  FIGURE 10. S i m u l a t i o n model o u t p u t : a v e r a g e p h e n o t y p e s over time  FIGURE 11. S i m u l a t i o n model o u t p u t : r e l a t i v e  128  average  f i t n e s s e s over time  FIGURE 12. S i m u l a t i o n model o u t p u t : a v e r a g e  129  "step-sizes"  over time  FIGURE 13. The s i m u l a t i o n model p r o g r a m l i s t i n g s  130  131  ix  ACKNOWLEDGEMENTS  This  thesis  t h i n k of myself explored  ecology"  almost  background.  I had w h i l e a d a p t i n g  I am most g r a t e f u l  ideas  embarrassing.  He s p e n t  were a  out  of  my  t o acknowledge t h e  t o t h i s new " h a b i t a t " :  t o a l l of those  that  completely  I would l i k e  who e n c o u r a g e d me.  S t e f a n Tamm was t h a t s p e c i a l p e r s o n w i t h discuss  I  a s an e c o l o g i s t , t h e g l i m m e r o f some o f t h e i d e a s  i n t h i s t h e s i s l u r e d me  "standard support  h a s been q u i t e an a d v e n t u r e f o r me. A l t h o u g h  so  raw  l o t of  time  whom that  I  felt  they  I  were  reviewing  my  could almost  earliest  drafts.  Marco Rodriguez chats  were  i s an e n t h u s i a s t i c j u g g l e r o f i d e a s , a n d o u r many  very  helpful.  Scott  Carley helped  g i v e me a  p e r s p e c t i v e on some o f my i d e a s , a n d t h a t was b o t h  wider  i n t r i g u i n g and  encouraging.  I owe p e r h a p s my g r e a t e s t t h a n k s t o Don L u d w i g . with  valuable  coaching,  and  He  provided  f i n a n c i a l a s s i s t a n c e (NSERC  me  grant  #9239).  C a r l Walters' this  thesis.  thorough e f f o r t s  i n reviewing  my  drafts  improved  Con Wehrhahn made h i m s e l f v e r y a p p r o a c h a b l e ,  thank him f o r encouragement,  our  discussions,  and  and I  h i s prompt  X  reading  of  my  drafts.  Judy  M y e r s ' h o n e s t c r i t i c i s m s were n o t  a l w a y s i m m e d i a t e l y welcome, b u t t h e y were  I t h a n k my roomies  family,  f o r m o r a l and m a t e r i a l  a t 4460 W.  Hestbeck,  s u p p o r t , a n d my  1 1 t h . T h a n k s t o a l l o f my  J o y c e A n d r e w , who a l s o h e l p e d c o n s t r u c t Jay  valuable.  who  c o n v i n c e d me t h a t  friends,  the f i g u r e s  arbitrarily  (at  distributions. and  vary only  parental  a  f i x the two  proportion  thirds)  The l a t t e r  and  vary  are symmetrical  i n the d e v i a t i o n  of  will  segment  be r e f e r r e d of  a  and  the  (undirected),  of t h e v a r i a n t  offspring  before  and  offspring offspring bimodal, from the  c h a r a c t e r i s t i c of a  t o as i t s " s t e p - s i z e " .  population  tables,  stretch.  variant only  p h e n o t y p e . The p a r t i c u l a r d e v i a t i o n  given player shows  to  especially  I was r e a d y t o f i n i s h ,  G l e n n S u t h e r l a n d , who e n c o u r a g e d me down t h e f i n a l I t was d e c i d e d  fellow  Figure  ( a ) , and a f t e r  S (b)  1  INTRODUCTION The  Neo-Darwinian t r a d i t i o n  genotypes  as  adaptive  a  regards  random p r o c e s s ,  needs  of  the  "Mutations...arise  undirected  species.  regardless  the generation with  Dobzhansky  of  their  of  respect  t o the  (1970)  actual  or  new  states  potential  usefulness.  I t may seem a d e p l o r a b l e  i m p e r f e c t i o n of nature  that  mutability  is  changes  the  not  restricted  adaptedness of t h e i r c a r r i e r s . could  imagine  that  to  adaptively that  that  according  part  of  thesis  cast  viewed  production  as  and  evolutionary  a  continual  of  genetic  variation production  search  variant  production  loss,  for a  framework  has  environment.  in  process  of  Evolution  creation  o f new  of genotype f r e q u e n c i e s , or of loss.  c h a n g e c o u l d be  of e x p l a n a t i o n variant  the  e v o l u t i o n a r y h y p o t h e s e s i n t e r m s o f p a t t e r n s of  genotypes and a l t e r a t i o n  variant  examine  c o n t r o l can r e g u l a t e g e n e t i c v a r i a t i o n  t h e s i s developed from a  to  be  to  an o r g a n i s m ' s genome i s i n v o l v e d i n  change i n , r a t h e r t h a n t h e s t a t e o f , an can  is  to i t s potential usefulness.  This which  Pangloss  t h e g e n e s know how a n d when i t i s good f o r  r e g u l a t i n g the production  genetic  enhance  However, o n l y a v i t a l i s t  them t o m u t a t e " . The i n t e n t o f t h i s possibility  that  It  always  i s o b v i o u s t h a t p a t t e r n s of  determined  and p a t t e r n s been  variant  by  both  in variant loss. placed  on  patterns  in  But t h e burden  the  processes  e.g. n a t u r a l s e l e c t i o n a n d c h a n c e . Why?  of  Although  we need t o u n d e r s t a n d s e l e c t i o n t o j u d g e w h i c h , i f a n y , o f a s e t o f new v a r i a n t s a r e r e l a t i v e l y variant  production  can  that  say  b e t t e r , we  t o s a y what t y p e s  a l l conceivable  need  to  know  about  m i g h t a p p e a r . So u n l e s s  variants  are  always  we  present,  2  variation logical,  production, therefore,  not  to  influence  on  evolution  e v e n i f we  end  up  selection,  have  a  good  of p a t t e r n s  ruling  rather  to  increased  and  the  plausibility  potential  production  --  d e s c r i b e how  a  variation  production  adaptability  s t a t e of t h e  I t seems  and  change,  environment.  p a r t s . In the  of p a t t e r n e d  first  variation  part  variation  requirements variation  and  patterns.  constraints  of  a  I  then  regulation  can  e x p a n d on  the  system  for  production.  The  merit  d e t e r m i n e d by in  production  I  production,  d e s c r i b e a g e n e r a l m e c h a n i s m by w h i c h n a t u r a l s e l e c t i o n  adjust  and  at  in variation  to  T h i s t h e s i s i s w r i t t e n i n two the  look  l o s s to  attention  t h a n a d a p t e d n e s s and  establish  limiting.  them u n i m p o r t a n t . I w i l l  change i n emphasis from v a r i a t i o n amounts  is  of a d i f f e r e n t  i t s success i n e x p l a i n i n g  generating  exercising patterns  the in  traditional hypothesis  new  ideas  of  genome  questions. Part  size  One  as  an  e x p l a n a t i o n s have not based  on  system  might  i d e a s t o g e n e r a t e new  ways  be  questions  existing  Part in  Two  this  example  is way.  of  production in  detected, f o r two  which  in science i s observations,  an  proved f r u i t f u l ,  variation  successful. After discussing regulation  i d e a or p e r s p e c t i v e  devoted I  might the  where  where be  a  more  hypothesized  I c o n c l u d e by "bandwagon"  consider  area and  to  using  topics.  the  3  CHAPTER  ONE  SOME BASIC  In t h i s c h a p t e r I w i l l some  of the c o n c e p t s t h a t  CONCEPTS  define  a few  underly  terms,  and  introduce  t h e a r g u m e n t s t o be d e v e l o p e d  later.  "Random" v s . " D i r e c t e d " How does one d i s t i n g u i s h in  variation  production  "directed"?  Random  "directed"  by,  subjected.  from  variation  the  that  those is  selection  I t i s by r e a s o n o f  connection (Mayr  "random" o r " u n d i r e c t e d "  "Evolution  which  are "adaptive"  uncorrelated  processes the  patterns  with,  to  generally  i . e . not  which i t w i l l assumed  lack  i s ( I r e p e a t ! ) a two s t e p  1978) o f v a r i a t i o n p r o d u c t i o n  and v a r i a t i o n  or  be of  process"  loss.  Randomness a n d S c a l e I will control  that  particular this  not, i n  thesis,  program  l e v e l t o be u n c o n t r o l l e d ,  selection.  of  mutation the  selected  I will  assume  production  on  selection  at  a  of  the  loci,  a  given  variation  and " u n d i r e c t e d "  existence  variation of loci  a  to influence the pattern  locus  of to a at  by any i n f l u e n c e  of p o s s i b l e  were  make  not  Given always  system f o r i t  of v a r i a t i o n  t h e l e v e l of t h e genotype, and i n the p o p u l a t i o n  control  traits.  heritable  would  level  production  and hence, a c r o s s  genetic  c o n t r o l l i n g mutation rates across for  suggesting  argue f o r c o n s i d e r a t i o n  rates across  against,  be  mutation  end r e s u l t . I w i l l  of  that  can  this  possible production  as a  whole.  4  With  this  evolution  feedback i s no  production level,  points w i l l  step  process  can  influence step  be d i s c u s s e d  production,  of  variation  or  organismal  one.  i n f u r t h e r d e t a i l l a t e r . At variation  production"  " d i r e c t e d v a r i a t i o n p r o d u c t i o n " a r e t o o vague i n the  randomness o f a phenomenon c a n  on w h i c h i t i s mutation  is  production simplify  Kinds  considered. but  one  of  Secondly, many  I  i n a p o p u l a t i o n . Above  it  d e p e n d on  must  processes was  themselves, the  scale  emphasize  that  of g e n e t i c  variation  discussed  alone  to  explanation.  of V a r i a t i o n If  we  selection  are  and  describes  in  deal  among  a  interaction  variation patchy  t o make a " p a t c h  variation genotypes  in in  effect  i t will  variation  with  environment  individual,  a  then  be  convenient  according  selection.  to  Levins  regimes f a v o r i n g  between  their  (1964a)  non-additive  respectively:  different,  with  of  selection  sufficiently  compared  w i t h the p o s s i b l e c o n n e c t i o n  types  the d i f f e r e n t  additive In  to  variation production,  distinguish  differences  and  variation  i t s u f f i c e s t o n o t e t h a t "random  because  to  two  to  s e l e c t i o n , at the g e n o t y p i c  b e c a u s e s t e p two  present  selection  longer a simple  f o l l o w e d by  These  and  from  "patch  relative  which to  the the  generalist" specialist"  permits  constant  in  a  single  f r e q u e n c i e s and  patches  tolerance  strategy strategy,  are of  an  inefficient NON-ADDITIVE  population  to  become a m o s a i c of  retain patch  specialists. The  f u n c t i o n o f ADDITIVE v a r i a t i o n , on  the other  hand,  is  5  to  permit  change  responsiveness. favored future  if  present  environment, determines  In  variation  selection  pressures.  rather the  than  this  the  am  variation  and  evolutionary  genetic  response  are  a r e good p r e d i c t o r s of  kind  s t a t e of  of  change  in  the e n v i r o n m e n t ,  adaptability,  and  an  which  additive  Time S c a l e s  components  genetic  variation  than  selection  as  production  are  an  formulation  of N e o - D a r w i n i s t  summarizing the  a g e n t , but  and  will  process  a process,  be and  (Ghiselin its  and  its  1981).  The  many  predation. Unfortunately  models, w i t h  selection  r e p r o d u c t i o n , tends to conjure  G h i s e l i n 1981  "results  of  themselves i n the  "units"  the  the  affecting  illusion  (patients,  in  of  a  the  uses). selection"  i n v o l v e d . Longer time allow  up  sub-  coefficients  r e s u l t s of a l l d e t e r m i n i s t i c p r o c e s s e s  " f o r c e " ( a g e n t ) a c t i n g on  observation)  a  t h e c o m b i n e d r e s u l t s of  such as c o m p e t i t i o n  are  as  I  t h e amount of a d d i t i v e  sub-processes  processes,  terminology  adaptability,  Furthermore,  a m e a s u r e of  i s not  therefore  selection  differential  with  Natural S e l e c t ion  are  r e s u l t s of  about a d d i t i v e v a r i a t i o n  population.  and  Natural  talking  responsiveness.  rather in a  be  concerned  additive  strategy,  processes  the  of  thesis I will  I  discussing  The  and  pressures  It is  importance  evolutionary  selection  frequencies,  production.  because i.e.  gene  Additive  selection  variation  in  the  results  actions ( i . e . to  will  depend  scales of  (longer  slower become  on  what periods  processes  subof  t o show  "important").  This  6  implies  that  t h e r e s u l t s of s e l e c t i o n can d i f f e r q u a l i t a t i v e l y  d e p e n d i n g on t h e t i m e s c a l e o v e r w h i c h we  perceive  A p p e n d i c e s I ~atid I I f o r f u r t h e r d i s c u s s i o n  of t h i s  them. idea.)  (See  7  CHAPTER SELECTION OF  If  there  selection, mold  exists  i n the  genetic  production. terms  of  Four).  heritable  f o r m of  Hypotheses  a d a p t e d n e s s , and  t h e way  of d i r e c t e d  explanation  for  and  control of  of a d a p t a b i l i t y ,  environmental  i.e. additive the  the  more  way  genetic  phrased  is  can  influence  be  perceived  production,  the  regulation  system i s d e s c r i b e d  by  production patterns  of are  alternative  of  of  Many  genetic variation  modify such a  analyzing  a  simple  literature.  in Variation is  the  p a r t of a  m e c h a n i s m w h i c h can  There  establish  variability.  system. A s e l e c t i o n  Patterns  (Chapter of  production  as b e i n g  way  in  terms  an  regulation  model from the  variation  in  to  o b s e r v e d p a t t e r n s of g e n e t i c factors  can  are.  chapter  variation  change,  e n v i r o n m e n t s change  commonly  this  then  f o r m u l a t i o n of h y p o t h e s e s  environments  of  plausibility  known h e r i t a b l e  and  are  purpose  variation,  kinds  would j u s t i f y  adaptability  The  VARIATION PRODUCTION  adaptability,  This  TWO  no  Product ion  question  that  genetic v a r i a t i o n "random"  variation production,  and  or  --  not.  patterns  there  are  the q u e s t i o n Mutation  is  patterns is one  i n i t i n c l u d e the  in  whether process  the the of  following:  8  . 1. D i f f e r e n t  g e n e s have d i f f e r e n t m u t a t i o n  This pattern that  mutation  is easily  rate  Different  g e n e s have  different  mutation  i s an  explained intrinsic  different rates?  rates.  by  the  p r o p e r t y o f t h e gene.  structures,  Ohno  assumption  (1969),  so  why  not  for  example,  higher  mutation  suggests that  l a r g e r genes p r o b a b l y have  rates  m u t a t i o n p r o c e s s e s a c t p e r b a s e p a i r and  per  since  not  locus.  2. D e l e t e r i o u s m u t a t i o n s a r e more f r e q u e n t  than  beneficial  ones. This  o b s e r v a t i o n a g r e e s w e l l w i t h t h e u s u a l model o f  u n d i r e c t e d m u t a t i o n . An u n d i r e c t e d c h a n g e i s improve  a h i g h l y o r d e r e d and  3, M u t a t i o n s  James 1959; It  is  c o u l d be  less  only  usually  result  products.  that  one  why  random  this  alterations  refinement  be  enough  f o r the  changes  worse, do  not  The  e f f e c t on tools  of  would  normally  s u c h c h a n g e s do of  essential  of  the  not gene  pattern  genome  is  t h a t changes t o i t are very l i k e l y but  unconstrained  matter  much.  r e f e r e n c e d above measured the its  Kerkis  s o , but i t  o f t h e e x p l a n a t i o n of  (2) s h o u l d be n o t e d : t h e o r g a n i z a t i o n constrained  s h o u l d be  mutations  o r a few c o d o n s and  in crucial  This  1935;  than  1964).  obvious  argued  affect  (Timofeef-Ressovsky  Mukai  to  system.  w i t h s m a l l e f f e c t s a r e much m o r e • f r e q u e n t  those with large e f f e c t s 1938;  integrated  unlikely  The  'severity'  enough  to  that  most  experimental  work  of a m u t a t i o n  by  viability. m o l e c u l a r b i o l o g y have r e v e a l e d p a t t e r n s i n  9  genetic  change  (Jeffreys within  among  1981),  within  patterns  in  hypothesized  vary  genes  populations,  between  b e t w e e n i n t r o n s a n d e x o n s , and  post-selection,  variation  cannot  production  and,  t o be t h e r e s u l t o f p a t t e r n s  less c r i t i c a l  be  attributed  indeed,  are  to  usually  in selection  pressures  p a r t s o f a p r o t e i n c i s t r o n a r e more f r e e  alternative  to  several  of  the explanations  a b o v e i s t h a t m u t a t i o n s o c c u r more f r e q u e n t l y parts  of  greater  the  extent  hypothesis  genome in  is  glance,  or,  more  equivalently,  critical  uncommon,  mutation control i s  to  less  Karlin  parts  "...the  are of  of  or  etc.,  is  genetics 1 lists  population, that  production  the  genome.  This  loci  because,  processes that genes  controlling  affecting  mutation  directly  or  specific rates  identified,  and  at  indirectly  factors controlling outcrossing  documented,  first  or Lamarckian.  r e c o m b i n a t i o n r a t e s , genes i n f l u e n c i n g  r a t e s of m i g r a t i o n ,  suppressed to a  at  (1974) s t a t e  sites,  critical  parsimonious  existence  particular  less  system of  i t seems t o be t e l e o l o g i c a l  and M c G r e g o r  in  advanced  perhaps because the i m p l i e d  Modi f i e r s of v a r i a t i o n p r o d u c t i o n  fact  are  (Holmquist et a l . 1983)). An  Table  genes  exons ( H o l m q u i s t e t a l . 1983). But t h e s e o b s e r v a t i o n s  i n t e r p r e t e d as being  (e.g.  natural.  studied  rates, i n the  literature." t h e many d e t e r m i n a n t s o f g e n e t i c along  with  heritable  variation  known e x a m p l e s o f g e n e t i c modifiers  of  processes  in  modifiers. of  e x i s t implies the p o t e n t i a l f o r adaptive  a  The  variation modification  10  TABLE 1.  The along  determinants  of genetic  variation  i n populations,  w i t h examples of h e r i t a b l e f a c t o r s that can  variation  modify  production.  MUTATION mutator Green  genes  and t r a n s p o s o n s  (Ives  1973; Thompson a n d W o o d r u f f  1950; M c C l i n t o c k  1978),  genes  for  1965; repair  enzymes a n d p o l y m e r a s e s  RECOMBINATION -chromosome number -frequency  of  (Catchesdide  c r o s s i n g over  1968; S t a m b e r g  ( i n v e r s i o n s , recombinant  1969),  B  chromosomes  genes  (Carlson  1978))  MEIOTIC DRIVE segregation al.  distorter  1960), t - a l l e l e  POPULATION  SIZE  POPULATION  STRUCTURE  -dispersal "The  locus  (SD) i n D r o s o p h i l a  i n h o u s e mouse  (Lewontin  (Hiraizumi et  a n d Dunn  1960)  r a t e s and m i g r a t i o n  genetic  control  genes d e t e r m i n i n g  of m i g r a t i o n  flagella  r a t e s i s e x e m p l i f i e d by  i n protozoa,  movements i n  b i r d m i g r a t i o n , e t c . B i r d and f i s h m i g r a t i o n  patterns  Hydra, often  11  Table  display  1 (cont'd)  t h e i n t e r e s t i n g phenomenon t h a t p o p u l a t i o n s  categorically  into  migrators  and  may  non-migrators, per  se  vary  and t h e  evidence suggests at times that  migration  may  be  polymorphic within populations."  ( K a r l i n a n d M c G r e g o r 1974)  BREEDING SYSTEM -frequencies  of mating  types  -mating patterns  (assortativeness)  - a l l of the f a c t o r s  can  to  isolation  contribute  reproductive  (see Dobzhansky  1970, p . 3 1 4 ) , e . g . i n c o m p a t i b i l i t y f a c t o r s i n p l a n t s , controlling  seasonal  timing  (olfaction,  vision,  sound),  Mendelian  factors  associated  affecting  of  reproduction,  e t c . "A  number  preferences  w i t h pigment c o l o r or p a t t e r n  that  in  genes  recognition of  simple  mating  (Mainardi  are  1968)."  ( K a r l i n a n d M c G r e g o r 1974)  SELECTION -dominance r e l a t i o n s h i p s i n f l u e n c e t h e e f f e c t s of s e l e c t i o n . Genetic Wright  modification  dominance  1929; F e l d m a n a n d K a r l i n  i d e n t i f i e d genetic  HISTORY  of  elements.  1971),  is  o f t e n assumed ( s e e  but  I  know  of  no  1 2  of  variation  these  p r o d u c t i o n by s e l e c t i o n . How  modifiers?  questions w i l l  Must  'group'  be answered  next.  selection  can be  s e l e c t i o n act on invoked?  These  13  SELECTION MECHANISMS Perhaps variation general  the greatest b a r r i e r  production mechanism  i s t h e l a c k of explaining  production  can  different  mathematical  production  take  of  MacGregor  Gillespie  more  concerned  Layzer  to  literature  concerning  variation 1967;  Charlesworth  easily  understandable,  the p a t t e r n i n g of v a r i a t i o n contains  Leigh  1976;  several  the m o d i f i c a t i o n of  (e.g. F i s h e r  1930;  1970,1973;  Felsenstein  Kimura  Karlin and  Yokoyama  about t h e dynamics of m o d i f i e r f r e q u e n c i e s of  a  large  process  of  modification  of  than  variation  s c a l e or long term e v o l u t i o n a r y p a t t e r n s .  and d w e l l e d  adjustable variation  and  e q u i l i b r i u m m o d e l s u s u a l l y seem  ( 1 9 8 0 ) d e s c r i b e d a more g e n e r a l  modification,  of  The  1981). But these  the relevance  production  an  how  models  Levins  1974;  1976;  on  place.  genetic  1956,1960,1967;  t o c o n s i d e r a t i o n of p a t t e r n e d  mechanism  of  variation  upon t h e e v o l u t i o n a r y i m p l i c a t i o n s o f  production.  T h e r e a r e two k i n d s o f s e l e c t i o n  t h a t c a n a c t on  processes  variation  selection,  secondary  production:  group  and  s e l e c t i o n . The c o n d i t i o n s u n d e r w h i c h g r o u p s e l e c t i o n  can  place  selection  a r e r a t h e r s t r i n g e n t ( W i l l i a m s 1966). Secondary  i s common, a l t h o u g h the it  present can a c t  of u n c e r t a i n , and v a r i a b l e ,  section I w i l l on  variation  mechanism f o r m o d i f y i n g  importance.  take  In  e x p l a i n s e c o n d a r y s e l e c t i o n a n d how  production,  variation  and  production.  criticize  Layzer's  1 4  Secondary s e l e c t ion Secondary transmission selection traits  selection  of t r a i t s  'acts'  that  'primary'  to  of is  the  are  acted  selection  on  by  acts  process  next  natural  on  further  level  that are acted N.B.  Pleiotropy  second  not  of  this  involve  can  on  production, distribution traits  i s a given  i f these within  There  i n s e c o n d a r y s e l e c t i o n -with other  genes  trait)  does  or l i n k a g e d i s e q u i l i b r i u m of selection.  regulate  population  assures  This  p r o d u c t i o n , . secondary  alleles a  strength  frequencies.  by s e l e c t i o n on a n o t h e r .  that  The  c h a r a c t e r s and t h e d r a g g i n g  the c o r r e l a t i o n ,  alleles  with  i s among g e n e s , n o t t r a i t s .  genes, and i s not s e c o n d a r y  act  usual  way.  correlated  In the case of v a r i a t i o n  The  correlation.  correlation  correlation  o f one c h a r a c t e r  because  are correlated with  (a gene a f f e c t i n g more t h a n one  existence  along  two  upon t h r o u g h t h e i r  This  the  indirection  on i n t h e u s u a l  not  genes v i a t h e i r c o r r e l a t i o n  t h e more e f f e c t i v e  of  differential  selection.  s e l e c t i o n on p h e n o t y p e s i n c h a n g i n g gene a  of  generation,  i s a measure of  the h e r i t a b i l i t y ,  genes a r e a c t e d  processes  are  correlated  with  selection  of  variation in  their  a l l e l e s producing  the  on w h i c h s e l e c t i o n a c t s . F o r e x a m p l e , l e t us c o n s i d e r t h e  r a t e of production phenotypic  constant  of g e n e t i c and ( g i v e n non-zero  variation  ( x ) . Suppose  for  the  on them, b u t b e c a u s e t h e y  phenotype. H e r i t a b i l i t y higher  is  the  heritability)  f o r some a l l - i m p o r t a n t , q u a n t i t a t i v e t r a i t  population  has  been  e n v i r o n m e n t . The o b s e r v a t i o n  increasing variation production  at  that  will  equilibrium  in  a  "factors responsible  be p r e s e n t  in  greater  15  proportion  in  the  e s t a b l i s h e s the secondary To there  phenotypic  variants  second c o r r e l a t i o n  two  alleles  of  offspring  (H)  produces a higher  (H and  important  x  phenotypes  with respect  variance  fecundity)  of  frequency  characterized  by  the  phenotype dimension relative  in  of  the  trait.  other. depends  generating  d i s t r i b u t i o n s of the  a  distribution One  H  and  L,  quantitative  two along  trait),  allele  The  fitness  only  the p a r t i c u l a r a l l e l e  r a t e s of  let  p o p u l a t i o n , whose the  t o one  genotype by  alleles  (x,  than  a  b e c a u s e of d i f f e r e n t  phenotype, the  following  operation  observation,  L ) , i n an a s e x u a l  phenotype, which i s u n a f f e c t e d In t i m e ,  population"  selection.  o n l y e f f e c t s are to determine the v a r i a n c e  (survival  the  r e q u i r e d f o r the  take a c l o s e r look at t h i s be  of  on i t s H or L .  variance  in  subpopulations the  relevant  take  on  the  shapes:  H  L  u Now  we  can  see  subpopulations, their  that,  in  a population  the genotypes  offspring  are  x->-  present  producing in  a  of the  shapes  relative  of t h e  frequency  frequencies  greater  variation  greater proportion  v a r i a n t s of the p o p u l a t i o n . T h i s happens relative  composed o f t h e s e  only  because  d i s t r i b u t i o n s , and  o f H and  L i n the  in of  two in the the  regardless  population.  16  W i t h t h i s p i c t u r e i n mind  we  may  follow  the  s e c o n d a r y s e l e c t i o n by c o n s i d e r i n g c e r t a i n p a t t e r n s on  phenotype.  both t a i l s variation reduced  It  would  p r o d u c t i o n , and t h a t s t a b i l i z i n g variation  greater  production.  proportion  in  production,  the  favored  while also  right a  equally  less  the  same  than  amount  f(/<).  The  greater  comprises  a  greater  deviant  to the l e f t that  differences  1 generation,  production  will  monotonic  no occur.  neither  modification  of  t o the as  o f t h e mean. And t h e  i s greater  cancel,  horizon  So  a  bell-  as f r e q u e n t l y  that the f i t n e s s of the l e f t  h a v e t h e same mean f i t n e s s  advantage.  (not n e c e s s a r i l y  (M). C o n s i d e r  subpopulations of o n l y  for  in  i n the population  phenotype t o t h e r i g h t has a f i t n e s s by  allele  f u n c t i o n f ( x ) . A phenotype that d e v i a t e s  o f t h e mean i s p r e s e n t  phenotype  The  x->  s h a p e d ) a b o u t t h e same mean p h e n o t y p e fitness  favor  tail.  s t a r t w i t h symmetric d i s t r i b u t i o n s  linear  greater  present  y  Let's  favor  s e l e c t i o n would  would do.  tail,  p r o p o r t i o n of the d i s f a v o r e d  favoring  B u t i t i s l e s s e a s y t o s e e what  s e l e c t i o n ( f o r one t a i l )  variation  of  of s e l e c t i o n  i s c l e a r that d i s r u p t i v e s e l e c t i o n ,  of t h e phenotype d i s t r i b u t i o n ,  directional  action  than  t(n)  phenotype i s  both  symmetrical  £(v) a n d , w i t h a t i m e  allele the  has rate  a  selective  of  variation  17  If  the f i t n e s s  f u n c t i o n f ( x ) i s n o t l i n e a r , one o f t h e H o r  L subpopulations  will  c o n c a v e up, t h e n  the r i g h t  a subpopulation  have a h i g h e r a v e r a g e f i t n e s s . I f f ( x )  more t h a n  tail  is  i n c r e a s e s t h e a v e r a g e f i t n e s s of  the l e f t  tail  decreases  i t , and a l l e l e  H h a s an a d v a n t a g e .  x->  u  If  f ( x ) i s c o n c a v e down, t h e n members t h a t d e v i a t e t o t h e l e f t  o f t h e mean p h e n o t y p e w i l l those  decrease average  members e q u a l l y d e v i a n t  t o the right  (symmetrically  distributed)  p r o p o r t i o n of v a r i a n t s (L) w i l l have d e c r e a s e d  The  Layzer  variation  will  more  than  increase i t .  X->-  U  The  fitness  subpopulation be f a v o r e d , a n d  w i t h the smaller selection  will  production.  Model  Layzer's  (1980)  about t h e e f f e c t s  m o d e l makes u s e o f t h e a b o v e  of c o n c a v i t y of t h e f i t n e s s  average f i t n e s s of subpopulations  observations  function  of d i f f e r i n g v a r i a n c e s  on  the  (Figure  18  1).  Layzer  assumes t h a t  the f i t n e s s  function i s bell-shaped,  and  that "...the  spread  compared w i t h the  trait  the  of  fitnesses  i n question;  instantaneous  i t s Taylor  this  see F i g u r e  trait, of  f(ji) +  f u n c t i o n by t h e f i r s t  f'(M)(x-M)  than the f i t n e s s  value  x  when  f"(y)<0. In other  It  phase  in  the  variation  production  case,  Gillespie,  this  adequate  i f  associated  with  o  is the  distribution  Thus t h e mean f i t n e s s f a v  and i s s m a l l e r  of  peak."  mechanism  the  mean  t h a n f ( y ) when during  the  an a d a p t a t i o n , a n d  ( p . 815) works  because  f u n c t i o n . Templeton  (1981)  of  the  severely  who  about t h e e v o l u t i o n of genes t h a t c o n t r o l t h e r e f o r e have l i t t l e has  done  genes, assumes t h a t  Layzer's  mechanism  much  adaptive  c o n c a v e down e v e r y w h e r e  variation,  terms  t h e model f o r t h i s a s s u m p t i o n , p o i n t i n g out t h a t ( 1 ) , conclusions  i.e.  is  evolution  a t o r near a f i t n e s s  Layzer's  modifier  then  2  f.(^) a s s o c i a t e d w i t h  f"(ju)>0,  assumed shape o f t h e f i t n e s s  (2),  0.5f" (M) ( X - M )  words ( s e e f i g . 1 ) , f a v > f ( y )  i s obvious that  criticizes  may  three  f over t h e normal  0.5f"(M)a2.  +  is greater  fav<f(/i)  +  which  by a v e r a g i n g  x, i s f a v = f ( ^ )  emergent  X = M one  mean  s m a l l , t h e mean f i t n e s s  obtained  of  with  1. I n t h e n e i g h b o r h o o d o f  population  approximation,  sufficiently  i s small  expansion:  f(x)=  In  the population  the t o t a l range of f i t n e s s e s a s s o c i a t e d  approximate the f i t n e s s in  in  (Gillespie  would  not  g e n e r a l i t y , and  that  work on t h e e v o l u t i o n o f peaks  are  dome-shaped,  1 9 7 8 ) . I f t h i s were t h e work  except t o decrease  l e a v i n g h i s e v o l u t i o n a r y consequences  of  adjustable  19  x  Figure  ->  1. "Fitness function f(x) and two frequency distributions P(x) for an a d a p t a t i o n s p e c i f i e d by p a r a m e t e r x. D u r i n g t h e emergence o f an a d a p t a t i o n t h e quantity c = f " ( x ) i s p o s i t i v e and s e l e c t i o n f a v o r s a broad f r e q u e n c y d i s t r i b u t i o n o f x. N e a r t h e f i t n e s s peak c i s negative and selection favors a narrow frequency d i s t r i b u t i o n . " ( L a y z e r 1980)  20  variation  unfounded.  A time s c a l e s A based  consideration  less on  obvious flaw  a  discusses  in Layzer's explanation  one-generat ion  definition  of  i s that  fitness.  Yet  i m p l i c a t i o n s o f h i s model on t h e e v o l u t i o n a r y  generation) selection  time  scale.  differ  on  Since  the  different  quali tat ive  time  scales,  i t is he  (multi-  results  as  I  of  argue i n  A p p e n d i c e s I and I I , L a y z e r ' s c o n c l u s i o n s a r e u n s o u n d . It terms  i s convenient to explain of  'adaptedness'  suitability  and  of a phenotype  this  time  scales  ' a d a p t a b i l i t y ' . Adaptedness  to the present  environment.  g e n e r a t i o n e v a l u a t i o n o f f i t n e s s w o u l d be one way Adaptability adaptedness described being  is  the  function  potentially  heterogeneous  environment,  for genetic  changing  environment  (Fisher  selection  variation 1958;  population  dealing  to  respond  Price  (or  for  so  and  additive or  ( s e e C h a p t e r O n e ) . The  in  determining  of  as  to maintain (1964a)  genetic variation to  variation  given  as  being  Fundamental role  additive  the  rate  (additive) variance  variation  to  a  Theorem  of  additive  at  which  subpopulation) evolves varies d i r e c t l y  (1980)  as  a  adaptability,  the  it.  evolutionary responsiveness  1972). I t says t h a t  based  one-  t o measure  adaptedness  responsiveness,  c r i t i c i s m of L a y z e r with  non-additive  i s a statement  amount o f g e n e t i c a l l y My  of  important  important  genetic  ability  in  i s the A  i n the face of e n v i r o n m e n t a l change. L e v i n s the  of n a t u r a l  problem  is  that,  (which  with  a the  i n phenotype. although  is  he  responsive  s e l e c t i o n ) the f u n c t i o n of which i s a d a p t a b i l i t y , h i s  is to  mechanism  21  and  e x p l a n a t i o n o f what s o r t o f v a r i a t i o n  various circumstances generation  i s based e n t i r e l y  e v a l u a t i o n of f i t n e s s  responsiveness,  i s a d v a n t a g e o u s under  on a d a p t e d n e s s . H i s one-  l e a v e s no room f o r e v o l u t i o n a r y  w h i c h i s t h e f u n c t i o n of t h e a d d i t i v e  variation  w i t h w h i c h he i s d e a l i n g . Given  the r e l a t i o n s h i p  (Layzer  fav= f U ) it  is  only  clear,  given  1980)  + 0.5f"U)a a  certain concavity  v a r i a n c e h a s t h e a d v a n t a g e i f t h e two same  mean.  It  subpopulation average  could  be,  mean v more  fitness  due  for  than  an  (f"(x)),  subpopulations  example,  that  a  compensates  for  any  which  have  the  different loss  in  t o t h e t e r m 0 . 5f " (ju) o . The s u b p o p u l a t i o n 2  with the greater variance evolves nearer  2  adaptive  peak  and  f a s t e r and  is  likely  to  t h e r e f o r e have a h i g h e r  be  average  fitness. The  above e q u a t i o n  subpopulations Unless be  the i n i t i a l  wrong  i s an  variance peak).  differences complicated. can  mean  relative  but  r e l a t i v e advantage holds initial  increasing  different  t h e r e a f t e r , i t would  function  of  of  of  the  being  time  the merits  different variances  i n variance production)  term  n(t),  genetically  toward  the  and  based nearest  (maintained  by  over  the long term  i s more  I t i s noteworthy t h a t over  the long term  selection  f a v o r i n c r e a s e d v a r i a n c e even under c u r v e s  downward.  variances.  l o n g e r p e r i o d s . Over t h e l o n g e r  (the d i r e c t i o n  comparison  advantages of  assessment t o e v a l u a t e  means u become f u n c t i o n s  i n phenotype Thus  same  v a r i a n c e s over  subpopulation  An/At  the  t o use t h i s  of d i f f e r e n t the  with  gives the i n i t i a l  that are  concave  22  This  last  p o i n t c a n be i l l u s t r a t e d  ( d e t a i l s of t h e  model  subpopulations,  A  phenotypic  are  described  in  aricKB, have d i f f e r e n t  v a r i a n c e . B has t h e h i g h e r  by c o m p u t e r s i m u l a t i o n Appendix  III).  Two  r a t e s of p r o d u c t i o n of  rate.  They  evolve  under  the p a r a b o l i c f i t n e s s  f u n c t i o n shown i n F i g u r e 2 . N o t e t h a t  this  curve  down  the  is  concave  subpopulation  with  disadvantage  in  subpopulations The  Figure fitness  greater  fitness  shows  3 a ) , which over than  that  causes  ranking  effect  variance  is  equal at  means,  an  immediate  average  the subpopulation  t h e l o n g e r term  of  the  the  with the greater  from  of  the  subpopulation  Therefore,  peak.  w i t h lower  (see  average  variance,  Short  term  v a r i a n c e t o have  run (see  3b),  Figure  r e v e r s e s due t o t h e c u m u l a t i v e  of a f i t n e s s advantage g a i n e d  phenotype.  w i t h lower  adaptive  7, in this  subpopulations  rate  leads to a higher  subpopulation  both  phenotype.  improves i t s average phenotype a t a g r e a t e r  g r e a t e r numbers. I n g e n e r a t i o n the  given  everywhere under t h e c u r v e . Here  that  w h i c h l a g s f a r t h e r away fitness  that,  b e g i n w i t h t h e same s i z e a n d  simulation  variance  so  by i m p r o v e m e n t  in  average  i f we l o o k more t h a n one g e n e r a t i o n  ahead  we s e e t h a t s e l e c t i o n c a n f a v o r g r e a t e r v a r i a n c e p r o d u c t i o n under a f i t n e s s  function that  even  i s c o n c a v e down.  Discussion Proper rates  of  e v a l u a t i o n of t h e r e l a t i v e advantages variation  production  (and  of  therefore,  different population  v a r i a n c e s ) i s d e p e n d e n t on t h e t i m e  s c a l e of comparison.  scales lengthen, a d a p t a b i l i t y  in  initial  adaptedness  gains  (Appendices  I  importance and  As  time  relative  to  I I ) . Variation  is  23  Figure  2. An i l l u s t r a t i o n o f the initial conditions of computer s i m u l a t i o n t h a t produced the r e s u l t s i n F i g u r e Two subpopulations, initially identical in size average phenotype, are allowed to evolve w i t h respect quantitative trait x under a f i t n e s s function that c o n c a v e down e v e r y w h e r e .  the 3. and to is  o OJ  in  in  40  50  60  70  MEASURE OF PHENOTYPE  GENERATIONS  F i g u r e 3. Output from the computer s i m u l a t i o n model described in Appendix I I I . Two s u b p o p u l a t i o n s a r e e v o l v i n g t o w a r d s an a d a p t i v e peak a t 75 " p h e n o t y p i c u n i t s " . S u b p o p u l a t i o n B ( d o t t e d l i n e ) h a s t h e h i g h e r r a t e of v a r i a t i o n p r o d u c t i o n , (a) A v e r a g e p h e n o t y p e o v e r t i m e , (b) Numbers o v e r t i m e .  80  25  important  f o r i t s determination  over time, fitness  not j u s t  at  any  in i t s contribution  one t i m e .  account  i n any r e a l i s t i c  alleles  that confer  Population  of t h e r a t e of phenotypic to  average  The f o r m e r e f f e c t  must be t a k e n  and  of  different  a  rates of v a r i a t i o n  population.  I  am  , w h i c h c a n be t r e a t e d a s a  a b o v e I have shown how t h e s e  talking  about  into  a n a l y s i s of the r e l a t i v e advantages  selection  behavior of  variation  addressing  life  as  a  variation  history  two ' v a r i a t i o n s '  for different  of  production.  p o p u l a t i o n s , a n d we commonly t h i n k o f p h e n o t y p i c  product ion  population  genetics deals with the s t a t i s t i c a l  characteristic  change  strategy,  a r e l i n k e d . In  variation  production,  people o f t e n t h i n k of t h e p o p u l a t i o n  characteristic  that  group  selection  I n t h e e x p l a n a t i o n above, I  have  shown  how  (individuals variation  selection  of  production) (by  group a g a i n s t  group.  seems  variation  favored  under  the  reader  that,  In other  w o r d s , i t i_s r e a s o n a b l e  been  done  patterns  production i n the past,  of  respective  t h a n by p i t t i n g  variation variation  because d i f f e r e n t p a t t e r n s  variation  can produce a d a p t i v e  rather  heritable  The p o i n t o f t h i s given  categories  v i a their  conditions —  selection  of v a r i a t i o n  place  given  certain  different  that  inclusive  deduce  p h e n o t y p e s w i t h common r a t e s o f  take  i s interesting  always minimized.  more  secondary s e l e c t i o n ) ,  production, But t h i s  not  can  obvious  prevail.  of  many d i f f e r e n t  subcomponents  It  i s necessary.  and  variation  variation  p a t t e r n s of v a r i a t i o n to explicitly  r a t h e r t h a n t o assume, that v a r i a t i o n  to  are  convince  production, production.  consider as  will  production i s  section i s  in  in  has  patterns usually  i s random, a n d l e a v e t h e  26  explanation  of e v o l u t i o n a r y p a t t e r n s  loss,  natural selection  e.g.  and  to  drift.  patterns  in  variation  27  CHAPTER THREE METAVARIATION The  last  chapter  pointed  f a c t o r s c o u l d be p e r c e i v e d regulating explained natural  the how,  as being  production  given  selection  out  of  act  a  in  will  the  consider  system  variation. heritable  why  we  a theoretical exist,  " M e t a v a r i a t i o n " i s my  for  production". mold  Given  the  metavariation,  word  basis  for also  factors,  The  of  s e l e c t i o n can t a i l o r  think present  production  look a t the c o n d i t i o n s  i fat a l l . "variation  heritable variation  genetic  It  could  c o n t r o l systems f o r v a r i a t i o n  a b s t r a c t , and t a k e  genetic  t o change t h e p a t t e r n of v a r i a t i o n  under which such a system s h o u l d  can  a  a system f o r r e g u l a t i n g v a r i a t i o n p r o d u c t i o n .  chapter in  known  of  these  w i t h i n a p o p u l a t i o n . C h a p t e r One d e s c r i b e d about  many  part  genetic  variation  can  that  in  variation  i n phenotype, s e l e c t i o n  phenotype. variation  Given  heritable  production.  An O p t i m a l R a t e o f V a r i a t i o n P r o d u c t i o n The  'function'  'search'  of  additive  phenotype-space  selection.  variation  f o r phenotypes  i n phenotype i s t o  better  favored  In a changing environment t h i s v a r i a t i o n  i n f o r m a t i o n of a  optimal  phenotype. I f , i n a changing environment, v a r i a t i o n at  too  slow  to  track  enables the  genetic  produced  population  a rate, the population  by  the  (changing) were  w o u l d go e x t i n c t  once t h e c h a n g i n g c o n d i t i o n s exceeded t h e t o l e r a n c e range of a l l the phenotypes. Competition  with another population  t h a t was b e t t e r a b l e t o  track  cause  i f a l l other  extinction  even  the  changing aspects  of organisms  conditions  could  of t h e environment  28  c o u l d be t o l e r a t e d . So a g e n e t i c too  system can produce v a r i a t i o n  at  slow a r a t e . But v a r i a t i o n c a n be p r o d u c e d a t t o o  Unless less  the  f i t , producing  rather for  environment changes  than  a  a long time,  near  an  a  rate  t o make t h e o r i g i n a l  experimental  phenotypes  is  a  also.  phenotypes bad  gamble  n e c e s s i t y . I f t h e e n v i r o n m e n t h a s been t h e same the p o p u l a t i o n w i l l  adaptive  peak,  down. I n s u c h a c a s e greater  great  production  likely  have e v o l v e d  where t h e f i t n e s s  greater of l e s s  variation  the environment remains s t a t i c ,  the best  be  f u n c t i o n i s concave  production  f i t phenotypes  to  will  mean  (see C h a p t e r One). I f  strategy  would  be  to  p r o d u c e no v a r i a t i o n a t a l l . It a best  appears then t h a t there  i s an o p t i m a l  r a n g e of r a t e s , a t w h i c h t o  particular  rate  of  change  of  produce the  r a t e , or at  variation  recognized  rate  that there  of  between  be  adaptedness  phenotype in  r a t e s of change  systems  The variation  it  production  We  have  production  would  by  i n a world seem  the  Just  rate  reasonable  as  of  of changes i n  of t r a c k i n g t h e moving  adaptability.  that  compromise  variation  in  variation  t h e t r a c k i n g o f an  optimal  rate.  n o t i o n o f an o p t i m a l i s n o t new.  just  r a t e , or range of r a t e s , a t  live  rates permits  a  i s a changing  i s u s e f u l i n t r a c k i n g an o p t i m a l p h e n o t y p e ,  variation  variation  capable and  changes?  that i s determined  t h e e n v i r o n m e n t . I f we  environmental genetic  change  i s an o p t i m a l  which to produce v a r i a t i o n change  of  given  environment. In a c c e p t i n g  e v o l u t i o n we a r e a c c e p t i n g t h e i d e a t h a t t h e w o r l d one. But what i f t h e  least  Kimura  r a t e at which t o  produce  (i960) quotes Auerbach  genetic  (1956):  29  "Thus e a c h species has to s t r i k e a b a l a n c e between the s h o r t - t e r m r e q u i r e m e n t f o r a low f r e q u e n c y of m u t a t i o n and the long-term requirement f o r an ample s t o r e of m u t a n t genes. A species i n which mutations are too frequent will die out because too many o f i t s i n d i v i d u a l s a r e weak, s h o r t - l i v e d or s t e r i l e . A s p e c i e s i n which m u t a t i o n s are too r a r e may do w e l l f o r a t i m e , but w i l l n o t s u r v i v e when a l t e r e d c o n d i t i o n s demand a d a p t a t i o n s f o r w h i c h i t d o e s n o t p o s s e s s the necessary genes." Kimura  s t a t e s : "These  there  must  species  be  optimal  of  Minimum  mutation  Load",  by  be d e t e r m i n e d .  suggest  that  survival  of  a  change."  t o d e s c r i b e what  Genetic  r a t e can  he  calls  which the  His  the  expected  essential  points  these: 1. H a l d a n e ' s  (1957)  substituting  one  independent on  2.  of  allele  of  a  and  3. M u t a t i o n a l  load  of is  instead,  frequency  (Lm)  system  increases with mutation should  modify  of  the  presented  Kimura's  Lm  + Le  is  i n terms of  argument, because a g e n e t i c fitness  is  rate.  rate  argument o n l y  load  is  a  (and  minimized. f o r the  w i t h the c o n c e p t of g e n e t i c  genetic  initial  rate.  mutation  argument i s s t r a i g h t f o r w a r d t o e x p l a i n .  argument  population  depends,  (Le) d e c r e a s e s w i t h g r e a t e r  i n t e r e s t . Given a f a m i l i a r i t y Kimura's  cost  another,  therefore decreases with mutation  load  genetic  have  or  for  initial  d e g r e e of d o m i n a n c e ) so t h a t L= I  gene  s e l e c t i o n i n t e n s i t y and  Substitutional  The  load,  mutant.  frequency,  4.  substitutional  t h e d e g r e e of d o m i n a n c e and  favored  his  r a t e f o r the  r a t e of e n v i r o n m e n t a l  (1960) t h e n g o e s on  "Principle  inevitably  optimum m u t a t i o n  under a given  Kimura  are  an  considerations  s a k e of load,  Unfortunately,  group  selection  l o a d i s " t h e p r o p o r t i o n by w h i c h  decreased  i n c o m p a r i s o n w i t h an  the  optimum  30  genotype"  (Crow 1 9 5 8 ) . The r e a s o n s  existence  of  concise,  an  but they  optimal  In  r a t e of v a r i a t i o n  to t r y to forstall  the  chapter  results  I  have  adaptedness of  described  f o r the  production  are less  selection.  some c o n f u s i o n b e f o r e  C h a p t e r One I p o i n t e d o u t t h a t t h e r e l a t i v e  o f a d a p t e d n e s s and a d a p t a b i l i t y which  have  do n o t i n v o l v e g r o u p  I would l i k e on.  I  depend on t h e  of s e l e c t i o n a r e c o n s i d e r e d .  noted  that  the  and a d a p t a b i l i t y  optimal  h o r i z o n the r a t e of  environmental  compromise. For a g i v e n  h o r i z o n o f an o b s e r v e r ' s  go  importances scale  over  In the present  compromise  between  i s d e p e n d e n t on t h e r a t e o f c h a n g e  t h e e n v i r o n m e n t . These a r e s e p a r a t e  optimal  time  I  notions. For a given  change (changing)  comparison  will  will  determine  time the  environment the time determine  the  best  or  a best  variation  in  determining  strategy.  To  Track  or not t o Track?  Whether  tracking  production  rate,  responsive  to  should  a  the  be  system  a  to be,  a d a p t a b i l i t y worth  best  basic  phenotype problem  'movement or  when  be  the  o f t h e t a r g e t ' . How are  the  pioneer  i n Levins  v a r i a t i o n production might  be  tuned  costs  of  o f most o f t h e t r a c k i n g i d e a s . The i s s u e o f  environments".  algebraically  adaptable  (1962,1963,1964a,1964b,1965,1967)  a d a p t a b i l i t y a r i s e s as soon a s t h e w o r l d "changing  immediate  how  bearing?  I consider Richard Levins to  is  to  (He  (1964b),  described  viewed  the  as  Layzer's  p. 638) L e v i n s  was an a d a p t i v e produce  is  one  of  mechanism  recognized  that  s y s t e m , a n d t h a t t h e genome optimal  rate  of  variation  31  production The  by  secondary  i m m e d i a t e c o s t s of v a r i a t i o n  bearing  if  the  change i s s u c h as  predictors  of p r e s e n t  responded a d a p t i v e l y to past present is  ones"  an . i m p o r t a n t  determination  of  determination of  to  the  environmental  o f what i s  predictable  t h i s p a p e r . But  phenotype.  should  autocorrelation about  be  pattern  environments t h a t have  ill-adapted  to  parameter  'enough'  in  the  compromise.  The  is  the  beyond  Levins explored autocorrelation with a  His  v a r i a n c e was  (1965)  adjustable via  of t h e a v e r a g e e f f e c t  analytical both  be g r e a t e r t h a n f r o m one  worth  or a u t o c o r r e l a t i o n ,  adaptedness/adaptability  Monte C a r l o e x p e r i m e n t s variance  only  past  environments w i l l  s e l e c t i o n on a g e n e t i c d e t e r m i n a n t on  are  environments, populations  s i m u l a t i o n model i n w h i c h p h e n o t y p i c  allele  make  ( L e v i n s 1965). P r e d i c t a b i l i t y ,  therefore  scope  production  t a r g e t i s p r e d i c t a b l e 'enough'. " I f t h e  of e n v i r o n m e n t a l poor  selection.  of  an  c a l c u l a t i o n s (1964)  and  suggest  zero only  generation  that  i f the  t o the next  phenotypic environmental  i s greater  than  0.8.  Metavariation In should  my be  d i s c u s s i o n o f how to  changes  in  genetically  responsive  compromise  in  the  i n t e r e s t here w i l l genetic Phenotypic  to  be  look  genetic in  determination v a r i a t i o n has  at  the  the  f o r , a moving t a r g e t .  adaptedness/adaptability  determination  examining of  population  t h e e n v i r o n m e n t I h a v e been u s i n g a  s p a t i a l m e t a p h o r of t r a c k i n g , o r s e a r c h i n g L e v i n s ' p r o b l e m was  a  of  phenotype.  My  the  analogous  problem  phenotypic  variation  product i o n .  f u n c t i o n of t r a c k i n g i n  of  phenotype-  32  space;  variation  in  variation  ' m e t a v a r i a t i o n ' , has t h e  function  p r o d u c t i o n - s p a c e . The p r o b l e m s on d i f f e r e n t  production, of  in  call  variation-  a r e t h e same e x c e p t t h a t t h e y a r e  work  has demonstrated  environmentally determined optimal factor  in  determining  produce  phenotypic v a r i a t i o n . important  metavar i a t  tracking  I will  levels.  Earlier  probably  which  how  that a u t o c o r r e l a t i o n phenotype  well to track, By  is  an  i n the  important  i . e . a t what r a t e t o  analogy,  autocorrelation  is  i n d e t e r m i n i n g the r a t e a t which t o produce  ion.  Time S c a l e D e p e n d e n c e At t h i s  t i m e i t must  'autocorrelation' function series  ...is as  specified  be  emphasized  the  i s t i m e s c a l e d e p e n d e n t . "The  a measure of t h e degree  observed  and  that  time l a g . " ( F i n e r t y  one-generation  that  autocorrelation  of c o r r e l a t i o n between  same s e r i e s  i f initiated  1980) L e v i n s was  dealing  the  minimum  time  over which d i f f e r e n t i a l  i n f l u e n c e gene f r e q u e n c i e s ; which  i t i s t h e minimum  Any e n v i r o n m e n t a l c h a n g e on a s h o r t e r  responses shorter time  a  with  a  must  be  dealt  with  time  time s c a l e ,  by a f a s t e r  generation  scale  over  environment.  i . e .within  response.  term b e h a v i o r a l and p h y s i o l o g i c a l consideration,  system  should  we  respond  now only  a  Faster  include developmental adjustment, a c c l i m a t i z a t i o n ,  scale  tracking  after  r e p r o d u c t i o n can  the g e n e t i c system can respond t o a changing  generation,  a  t i m e l a g , i . e . how p r e d i c t a b l e an e n v i r o n m e j r t i s  f r o m one g e n e r a t i o n t o t h e n e x t . T h i s i s b e c a u s e one is  statistic  responses. Given  and this  make t h e r e f i n e m e n t t h a t a if  the  environment  is  33  predictable  enough  on  the  time  s c a l e over  which the  system  can  well  for  respond.  When i s M e t a v a r i a t i o n The its  c o m p u t e r model d e s c r i b e d  intended  schemes  p u r p o s e of c o m p a r i n g d i f f e r e n t  environment  f o r m of an a d a p t i v e  the  i n Appendix I works  i n v a r i o u s e n v i r o n m e n t s . The  dimensional  form  Important?  and  breadth  i s modelled  peak d e f i n i n g  change  arbitrarily  from  specified.  "arbitrary"  to  time,  independently  output  c o n s i s t s of the  population  size,  or  in  average  f o r a l l p o p u l a t i o n s . The  better  population,  confirms of  and  The  be with  run at the  same  be  with  each o t h e r .  f o r each  and  can  The  populations  The  generation:  relative  average  a v e r a g e r a t e of  variation  data are produced  above computer model i s not under  i s not than  which  whether  another  any  under  adjustable v a r i a t i o n , given compared  the  in tabular  form.  conditions  question  asexual  phenotype  production  the  generation  statistics  for  The  to  competition  fitnesses  plot  each  phenotype.  (unfit variants).  schemes can  following  one-  peak a r e m o d i f i a b l e t o c h a n g e  six  variation production  regime i n a  optimal  generation  Up  production  as a f i t n e s s f u n c t i o n i n  i m m e d i a t e c o s t of v a r i a t i o n p r o d u c t i o n  environmental  and  selection  the  of t h e a d a p t i v e  variation  with  fixed  what has  variation  adequate  metavariation particular certain  is  for  important. scheme  circumstances, at  p r o d u c t i o n . The  been d i s c u s s e d a b o u t d i f f e r e n t  production  determining  variation  i t s c o s t s , i s ever  variation  for  different  k i n d s of  but  an  The is  whether  advantage  computer model optimal  rates  environmental  34  change, but i t s c o n s t r a i n t generality,  of  asexual  was u n c l e a r  fixed variation.  of  a  metavariation  c o s t s of m e t a v a r i a t i o n 1. F i r s t ,  there  the  regulation genome  development  genomes large  that is  solely  maintenance  a  of  useless  of  in  DNA  usefulness,  t h e amount o f DNA have  DNA  a very  involved  proportion  population  levels.  c o s t s of having not  responding  costs  of  discussed,  "extra"  are prepared of  eukaryote  t o the i n d i v i d u a l . Given the  eukaryotes  that  is  of  no  i t m i g h t be s a f e t o assume t h a t  required  for a  metavariation  system  s m a l l e f f e c t on i m m e d i a t e f i t n e s s . See  of c o s t s It  arises  can  at  concerns.  the  lineage,  or  be m e a s u r e d by c o m p a r i n g t h e  a fixed variation  production  t o change i n e n v i r o n m e n t a l  possibly  in  phenotype  effects  C h a p t e r Four f o r f u r t h e r d i s c u s s i o n of these 2. A s e c o n d c a t e g o r y  only  In the short  of the i n d i v i d u a l  significant  "junk",  amount  the  incurred to  involved  have on an o r g a n i s m . Some, a u t h o r s  demonstrated  would  cost  of v a r i a t i o n p r o d u c t i o n .  m i g h t be ' c h e a p e r ' . I t i s u n c e r t a i n what  t o assume  which  w o u l d be w o r t h b e a r i n g . The  i n t h e f o r m o f DNA  comprised  and  would  under  i s the a d d i t i o n a l metabolic  in  DNA  Furthermore,  a r e o f two k i n d s :  i n d i v i d u a l organism  a  conditions  system  the  term  with  t o me how s u c h an e x p l o r a t o r y model c o u l d be u s e d  to c o n f i d e n t l y d e l i m i t a l l of t h e costs  restricts  a n d i t i s n o t e q u i p p e d t o compare a p o p u l a t i o n  a d j u s t a b l e v a r i a t i o n w i t h one w i t h it  reproduction  responding  and  change, w i t h t h e  inappropriately.  such i n a p p r o p r i a t e response can  environment i s not s u f f i c i e n t l y  scheme,  occur  As j u s t i f the  a u t o c o r r e l a t e d on t h e t i m e  35  scale  over  system t h a t  which  the  regulation  responds too q u i c k l y t o  is  d i s a d v a n t a g e o u s i f immediate  and  therefore  system can respond. A immediate  conditions  c o n d i t i o n s a r e anomalous,  bad p r e d i c t o r s o f f u t u r e c o n d i t i o n s . G i v e n a  p r e d i c t a b l e e n v i r o n m e n t , a s y s t e m may r e s p o n d t o o and A  t h u s a l w a y s be a d a p t e d t o t h e way t h i n g s  quantitative  favor metavariation 1 . the  assessment  of  environmental  individuals  variability.  the cost  were.  the c o n d i t i o n s required to  over f i x e d v a r i a t i o n r e q u i r e s  tolerance  determining  of  slowly,  to  knowledge o f :  the  amplitude  of  is  important  in  This  of not r e s p o n d i n g , and t h e b e n e f i t of  responding. 2. t h e  potential  metavariation 3. t h e  I  of  of  environmental  i t s assumed m e t a v a r i a t i o n  describing  that  a l l the  metavariation  sets  system  unmeasurable  But  would  of  change,  conditions  be a d v a n t a g e o u s  variables  system might first,  I  from t h e response  to  to  which  was t o o c o m p l e x have  be o f l i t t l e o f how f a s t  a to  included  immediate u s e . a  variation  i t exist. t h a t my  intended  was t o a n s w e r j u s t a p a r t i c u l a r  instance  question  like  of  under  t h e s i s . I t would  respond, should  would  q u a n t i t a t i v e assessment o f t h e more g e n e r a l  particular  i n t e n t i o n of q u a n t i t a t i v e l y  I o f f e r a q u a l i t a t i v e assessment  regulation  a  system.  my o r i g i n a l  manage w i t h i n t h e s c o p e o f t h i s  Below  of  o f t h e o r g a n i s m , on t h e t i m e s c a l e  concluded  enough  response  system  predictability  viewpoint of  speed  emphasize  "What s p e e d s  of  incorporation  of  36  information  about  advantageous models  of  different the  the  to l i v i n g variation  environment  into  genotype  systems?" I can  imagine  production  selection,  and  feedback speed of i n f o r m a t i o n  genetic  the  four  are  different  each  with a  from the e n v i r o n m e n t  to  material:  1. t r i a l random  and  error  --  This  i s t h e s t a n d a r d a s s u m p t i o n of  (undirected) v a r i a t i o n .  uncorrelated Warburton  with  their  M u t a t i o n s happen i n potential  (1967) f o r a model  of  a  way  usefulness.  See  selection  based  on  the  t h e o r y o f g u e s s i n g games. 2. p a t t e r n e d focussed  trial in  beneficial. stored  and e r r o r  patterns  -- V a r i a t i o n p r o d u c t i o n can  that  are  more  likely  S e l e c t i o n on a l p h a - g e n e s p r o d u c e s  to  be be  'heuristics'  i n ( l o n g e r memory) b e t a - g e n e s .  3. s t r e s s - p r o d u c e d variation  trials  L i f e t i m e e x p e r i e n c e s enhance  i n an  individual's  respect to stressed t r a i t s  (see McDonald  4. d i r e c t  production  --  programming  process  (Lamarckian)  moderated  experience  by  natural  programs  an  C h a r a c t e r i s t i c s are acquired Variation  production  --  is  germ  trial  selection. individual's  always  with  and  error  1983). No  steadily,  line  Lifetime gametes.  i f not a l l a t once.  in  the  direction  of  improvement. Not  a l l of  these  feedback  speeds  have  received equal  attention.  Is that reasonable? A q u a n t i t a t i v e demonstration that  Lamarckian  i n h e r i t a n c e would seldom or  even  if  i t  discrediting  were  possible,  would  never  be  advantageous,  be much more p o w e r f u l t h a n  i t on t h e b a s i s o f what we do n o t  know,  i . e . lack  37  of e v i d e n c e f o r t h e r e q u i r e d c o n n e c t i o n s between e n v i r o n m e n t and genetic  material.  the p o t e n t i a l knowledge,  The q u a n t i t a t i v e  utility  lacking  requiring  o f any o f ^ ^ t h e s e f e e d b a c k s p e e d s  i n the b i o l o g i c a l  literature.  i s , to  Figure  4,  systems: the phenotype (see Bateson  T h i s i s an a r e a  which p i c t u r e s a h i e r a r c h y of c o n t r o l  includes several  l e v e l s of c o n t r o l  1963), t h e a l p h a genes c o n t r o l  developed,  and t h e beta-genes  (alpha-) genotypes.  control  the  system  phenotype  that  t h e g e n e r a t i o n o f new  (The ' a l p h a ' a n d ' b e t a ' d i s t i n c t i o n  was made  by L a y z e r 1980.) A c c o r d i n g t o h i e r a r c h y t h e o r y ( s e e Simon we  expect  and  t o d e t e r m i n e l o n g e r t e r m p a t t e r n s , and l o w e r  higher levels  i n t h e h i e r a r c h y t o c h a n g e more  f a s t e r and i m p o r t a n t i n t h e s h o r t In  the  hierarchical  selection.) comprised  The of  o r g a n i z a t i o n of F i g u r e  'selection  the  in  degree  is  reflected  i.e.  of  a  correspondence  the h e r i t a b i l i t y ,  perfect genotype  each  level  'fitnesses'  f i t n e s s e s of  change  because can  development environment,  2  a  for  be  faces  is  of t h e l e v e l  just  phenotypes  determine  the  a population. phenotypes  i n gene f r e q u e n c i e s d e p e n d s on t h e between  phenotype  and  genotype,  (0<h <l). This correspondence 2  through  code  of  h  to  4, c h a n g e s i n  t o w h i c h t h e s t r e n g t h o f s e l e c t i o n on t h e in  slowly  ( T h i s i s not group  gene f r e q u e n c i e s o f a l p h a - g e n e s w i t h i n  The  degree  pressure'  differential  b e l o w . The d i f f e r e n t i a l  levels  1973)  term.  each l e v e l a r e s e l e c t e d v i a t h e l e v e l s below.  change  my  attention.  Consider  is  theory necessary to specify  i s never  d o m i n a n c e a n d e p i s t a s i s more t h a n one a  phenotype  environmental  given  phenotype  proceeds variation  and,  since  in interaction can  produce  the  with the different  PARAMETERS RANDOM  VARIATION  OF  THE  7 GENETIC SYSTEM  PRODUCTION  {J9  NON-RANDOM  STRUCTURAL AND  VARIATION  REGULATORY GENES  EPIGENESIS  5  PHENOTYPE  S  PRODUCTION (©<  GENES)  GENES)  METAVARIATION  (SECONDARY) SELECTION GIVEN CORRESPONDENCE OF GENOTYPES WITH PARTICULAR PARAMETERS  GIVEN CORRESPONDENCE OF PHENOTYPE WITH GENOTYPE  F i g u r e 4. The r e l a t i o n s h i p o f a l p h a a n d b e t a genes, l e v e l s of i n d i r e c t i o n i n secondary selection.  and t h e CO  39  p h e n o t y p e s f r o m t h e same g e n o t y p e . (response t o ) = ( selection ) So we c a n s a y t h a t (change i n a l p h a ) (gene f r e q u e n c i e s ) The  differential  determine  h  =  (strength of) ( selection ) ( R o u g h g a r d e n 1979)  2  h , ( s t r e n g t h of s e l e c t i o n ) ( on p h e n o t y p e s ). 2  'fitnesses'  of  genotypes  t h e change i n f r e q u e n c i e s of t h e 'metagenotypes'  genes).  The c o r r e s p o n d e n c e  between these  either  (h  because the beta  2 2  < l ) . This  is  L a y z e r ( l 9 8 0 ) a n d i n F i g u r e 4) j u s t each  alpha  which  tailor  involve  a  Lamarckian  variability=0);  a given beta a l l e l e  any  of  different  alpha  allele  number  particular  beta a l l e l e s .  Sexual linkage  levels  alpha  recombination  the  perfect  variabi1ity  mechanism  alleles,  =  h  and  2 2  c a n work w i t h i n s e x u a l l y r e p r o d u c i n g  affect  only  the  modifier  and  secondary  p o p u l a t i o n s . They and  speed of f i x a t i o n  polymorphism but not the q u a l i t a t i v e nature  or  and t h e a l p h a  i s referred to Karlin  selection  to  a  different  the c o r r e l a t i o n ,  t h a t t h e mechanism of  between  setting  ( s t r e n g t h of s e l e c t i o n ) ( on a l p h a - g e n o t y p e s )  (1974)  "Linkage  allele,  conversely,  between t h e beta a l l e l e s  t h a t t h e y p r o d u c e . The r e a d e r  that  or  of  may c a u s e t h e g e n e r a t i o n o f  f u r t h e r decreases  f o r evidence  (beta  g e n e s ( a s d e f i n e d by  McGregor  appears  not  may-be a s s o c i a t e d w i t h many  So we have ( change i n beta ) (gene f r e q u e n c i e s )  disequilibrium,  determined  is  l o c u s ( r a t h e r than p r e s c r i b e the p a r t i c u l a r  would  alleles  (alpha genes)  primary  loci  or approach t o  of t h e  outcome"  at  the m o d i f i e r (beta) l o c u s . There  are  two  l e v e l s of i n d i r e c t i o n  b e t w e e n s e l e c t i o n on  p h e n o t y p e s and c h a n g e s i n b e t a gene f r e q u e n c i e s The  strength  of  selection  (see Figure  4).  on t h e p h e n o t y p e i s d i l u t e d by two  40  successive beta  gene  Levins be  'heritability' level,  f a c t o r s , so t h a t t h e r e s p o n s e  the v a r i a t i o n - p a t t e r n i n g l e v e l ,  (1965) c a l c u l a t e s t h a t t h i s  important  lifetime.  on  a  time  But t h e p o i n t  response  scale  much  i s that the patterns a r e on an  scale,  to generation  scale usually dealt with  The  Real For  world  World  in classical  I have, u n t i l  i s multidimensional.  In  of v a r i a t i o n p r o d u c t i o n That s i m p l i f i c a t i o n  different  traits  c a n have d i f f e r e n t  t h a t t h e r e c a n be c o v a r i a n c e  One  only  time  genetics.  variation  defined  component  of  o f p h e n o t y p e c a n be c a l l e d  particularly discussed  relevant in  order  c o m p a r i s o n s . That  that the  explained  the  identify  production  that rates,  traits.  i t refers  to  trait.  components  to  the  to  facilitate  The  term  of  selection  variation-production-space.  production changes. once,"  makes s e n s e o n l y But  and  is  phenotype  regime  being  phenotype-phenotype  here.  J u s t as phenotype- or t r a i t - s p a c e i s m u l t i d i m e n s i o n a l , is  a  p h e n o t y p e . A l m o s t any  a  i s how i t i s u s e d  the  facts  i n f i t n e s s among t h o s e  subjectively  to  I  avoided  i s an awkward t e r m i n t h a t  used  the fact  i n terms of one, a l l -  NOTE: ' T r a i t '  usually  species  e c o l o g i c a l time  population  Chapter  trait.  aspect  than a  evolutionary  now, i g n o r e d  important,  and  nevertheless  i s Multidimensional  simplicity  modification  slow.  of change i n v o l v i n g  adjustment of v a r i a t i o n p r o d u c t i o n r a t h e r than the g e n e r a t i o n  the  i s very  would  shorter  at  Adjusting  rates  of  so  variation  i f the rate of environmental  change  t h e e n v i r o n m e n t may n o t c h a n g e i n a l l r e s p e c t s a t  only  a  subset  of  variants  may  have  potential  41  usefulness.  For  example,  if  the  environment only changes in  temperature then only temperature v a r i a n t s would be r e q u i r e d for a d a p t a b i l i t y -- v a r i a n t s of any  other  sort  have  no  potential  usefulness. Consider  the  problem from another p e r s p e c t i v e . Let us  that v a r i a t i o n production  is  regulated  in  populations  say  of  a  p a r t i c u l a r type of organism by a mechanism a f f e c t i n g a l l t r a i t s , say  by  which  different is  more  temperature allele  of  effective  variants  that  selection  alleles  be  than  more  more  to  select  general traits  for  Selection  favor the l e s s But  this  of for  effective  directional  in o p p o s i t i o n to the s t a b i l i z i n g s e l e c t i o n  effective  p r o d u c t i o n . And  other.  variants.  a c t i n g on a l l other phenotypic the  the  would i n d i r e c t l y  produced  would  a g e n e t i c r e p a i r enzyme, one  repair  traits.  latter  enzyme, that  i f the d i r e c t i o n a l greater  The  favor  caused lower v a r i a n t  s e l e c t i o n were strong  pro d u c t i o n  e f f e c t of the genetic  would  enough  of v a r i a n t s , because of  repair  system,  variants  in  the all  would be produced, whereas only temperature v a r i a n t s have  a chance of having From responsive  this  a higher  kind  of  fitness. argument  it  is  c l e a r that the most  v a r i a t i o n adjustment system would be one  independently  regulate  the p r o d u c t i o n  that  of v a r i a n t s of  could  different  traits. In the p o p u l a t i o n g e n e t i c s l i t e r a t u r e , selection  on  statistically known process  as  the  one  locus  the i n t e r f e r e n c e  with s e l e c t i o n on other  loci  that  c o r r e l a t e d ( i n l i n k a g e d i s e q u i l i b r i u m ) with Hill-Robertson  of recombination  effect  destroys  (Felsenstein  linkage  of are  it  is  1974).  The  disequilibrium  among  42  loci  in  a  population,  and  that  explanations  of the  (Felsenstein  1974, F e l s e n s t e i n and Yokoyama  Variation  spatial  metaphor u s e f u l also  be  acquiring The  has,  array  Levins  survival.  about  modelled  track  recent  Memory  is  genetic  variation  short  evolution  in  a  selection and  out that  terms o f  contains  i n the present and,  as  Warburton a  (1967)  guessing  successful  a  t h e gene p o o l  recipe  memory,  for  game  alleles  the environment  would  are  with  the  or  the  shortened  equal  of  depended  weight,  would  recent  environment,  history by  of  reducing  conditions. or enhancing  respectively.  p a r a d o x w h i c h now emerges  parameters of the  capable  and i t s h i s t o r y , but i t c o u l d  than  production,  can  phenotypes  population  have t o be p r i m a r i l y d e t e r m i n e d by t h e  rather  lengthened  of a  i n w h i c h gene f r e q u e n c i e s  c o n d i t i o n s . To t r a c k  memory  in  population  i n the past.  environments of the p a s t ,  environment,  "The  of  Insights  answers.  long  frequencies  recent  time,  "guesses"  (1968) p o i n t s  A very  dynamics.  i t s environment  natural  are  "right"  a l l the  gene  1976).  evolutionary  thinking  or l o s s takes  "know" a l o t a b o u t not  recombination  t a r g e t - t r a c k i n g i s not t h e o n l y  frequencies  a memory, a s w e l l a s  on  of  information.  o f gene  mutations  sufficiently  is  by  information  in fact,  of  in discussing gained  fixation  where  metaphor  and r e j e c t i n g  indirect since  advantages  underlies a l l  P r o d u c t i o n and Genet i c Memory  The  can  evolutionary  function  i s that  only  a  system  with  f o l l o w t h e e n v i r o n m e n t . But t h e optimum tracking  system  depend  on  the  mean,  43  v a r i a n c e , a n d a u t o c o r r e l a t i o n o f t h e e n v i r o n m e n t . These c a n o n l y be e s t i m a t e d  a c c u r a t e l y by a s y s t e m w i t h a l o n g  memory s o t h a t t h e l a w o f l a r g e numbers o p e r a t e s . statistics  of  the c a l i b r a t i n g is  some  Since the  the environment a r e a l s o subject s y s t e m c a n n o t have i n f i n i t e  enough  t o change,  memory.  There  optimum l e v e l o f memory f o r i t , w h i c h c a n o n l y be  e s t a b l i s h e d by s y s t e m s w i t h l o n g e r  memory,  e t c . " (Levins  1968) Levins  perceives  assuming gene  a  problem, or paradox, because  that a population  c a n have o n l y  p o o l . I f organisms c o n t a i n only alpha  But  i f they had beta  for  a p o p u l a t i o n : one s h o r t memory o f  and  another  genes  longer,  as w e l l ,  So i f we s u p p o s e such  a  way  as  of  to  sufficient  r e q u i r e s a l o n g memory, memory,  does  g e n e t i c memory?  genes, t h a t  i . e . one i s true.  t h a t w o u l d mean two m e m o r i e s alpha  gene  frequencies,  deal with the level,  since  constructed  adaptedness/adaptabi1ity the  autocorrelation and  genes  genes.  that s u c c e s s f u l organisms are  tradeoff at the genetic existence  memory,  more s l o w l y c h a n g i n g memory o f b e t a  encoding the strategy f o r the alpha  in  one  he i s t a c i t l y  responsiveness  assessment in  the  the  environment  requires  i t n o t make s e n s e t o e x p e c t a t l e a s t  of  a  short  two k i n d s o f  44  CHAPTER FOUR GENOME S I Z E PATTERNS I h a v e been a s s e r t i n g t h e p o s s i b i l i t y determines  a  pattern  of  r a t e and d i r e c t i o n  of  Since  control  a  genetic  change  s t r u c t u r e , a n d genome s i z e a crude i n d i c a t o r reasonable evidence  variation of  production  a  system  that genetic suitable  population's has  (the t o t a l  control t o the  environment.  i m p l i c a t i o n s f o r genome  amount o f DNA p e r c e l l ) i s  o f d i f f e r e n c e s i n genome s t r u c t u r e ,  i t  seems  t o e x a m i n e p a t t e r n s i n genome s i z e among s p e c i e s f o r  of p a t t e r n s a c r o s s environments d i f f e r i n g  in  rates  of  change. Below critical an  review  known  patterns  look a t the e x i s t i n g  of v a r i a t i o n  is  extensive  genome a c r o s s a n i m a l  is  little  factor  of  take a  f o r them, a n d p r o p o s e  r a t e s of  variation  and p l a n t t a x a  species  in  the  (see Figure varies  change  and  the  amount o f DNA p e r 5). The r a n g e i n  considerably.  t o s p e c i e s v a r i a t i o n among  b i r d s , a n d mammals, DNA amounts i n a m p h i b i a n s range of these  size,  Paradox  genome s i z e w i t h i n e a c h g r o u p a l s o there  genome  production.  P a t t e r n s and t h e C-value There  in  explanations  e x p l a n a t i o n b a s e d on e n v i r o n m e n t a l  regulation  The  I  span  While  reptiles,  the  entire  g r o u p s . DNA amount i n b i r d s v a r i e s by l e s s t h a n  two, but i t ranges over  a  three orders of magnitude i n  a l g a e and p r o t o z o a . Genome s i z e h a s been o b s e r v e d levels.  But i n t r a s p e c i f i c  to vary  variation  e x c e p t i o n ; r e p o r t s of i t a r e probably  among  i n genome s i z e  taxa  at a l l  i s s t i l l the  over-represented  i n the  45  -l—I  A.  I l m i ;  -I—I  I  MTTTI—  TTTTT—  I I I 111 ] —  i i  c'  _^  i m i i ~ ~  T—I  o"  "1  1—I I M III]  1—I I I r t ;  III lll|  ANIMALS 1  ~ M C T A T X R i A I M o w M K l J MAMMAL**  , PnOTQTMCRiA (I 1  $T * v t 5 (B*tfi>  CCCCNQ I ONA'CELL  ANUftA (Frog* and ToofrU  IHAPLOIOJ  1 . 1 1 •• i 1.1  —  —  "  UROOCL« I S o K m M f i  11 APOOA ( C o v c i U m * —* | f>PNOA (Lung f * h n l .  D'<*/G£*OMt  ^ ^ • " • " ^  j j j TELtOSTCl I  J KXOSTEl  ] 3NA/CMO0M0$0MC  1  | t*ONT riSMCS  , CMONDROSTCi  J  J  I TOTAL 0 N 4 * I N MULTINUCLEATED C E L L S _t.  O i N & E FO« W E E N  1  »LCAE 1  , 5 A G N A T H A ( L o m p r t n and Mrjq«*h«v)  [ aPMALOCMORDATA ( A ^ c ^ u * !  ' UROCHCAOATA I T ^ c e t r t ) •  £ ARTMROPOOA  ' MOLLUSCA 11 ANNCLlCA (&«QmrM*<9 W o " m ) 1  I 2 POmrfRA  B.  , CC«NO0C«VATA 7  1 1 K M A T O O A (flcvd—*™! 11 C O t L t N T E W T A <Spo«ont  PLANTS JSPERMtTCVitTES G»M»*OSPt«!MtE | 1  J  SPHEKO**StOA I H V W I O H I  PTEBiOOPMrTES  5 LYCOPSlDA (CutJ-MOTt*!)  BACTERIA AND VIRUSES \ 56 B A C T E * » i A 32 2 - 5 DNA v i f t u s t s f. * 5  AND - S  DNA ViftUSES I  t I 11III  _l  '  1  1 1 ' 'I'  ' im i l  I  1_1_L1 U l l -  NUCLEOTIDES  Figure  5. The r a n g e s o f DNA (RNA f o r some v i r u s e s ) c o n t e n t p e r c e l l a n d p e r chromosome i n m a j o r c a t e g o r i e s o f p r o k a r y o t i c ad e u k a r y o t i c o r g a n i s m s . The number o f s p e c i e s r e p r e s e n t e d i s t o t h e r i g h t o f e a c h e n t r y , ( f r o m P r i c e 1976)  46  literature, subsequent cannot and  and studies  reliably  Smith  The  and  variation  notion  should  them  have  it  is  goes  not  Smith  detect variation  1976).  therefore  information  no  significant  (Sparrow  of  a  and  2n f o r d i p l o i d , by  Moreover, in  any  eukaryote  estimation  proportion  (Crick  1971;  t o d e s c r i b e why Although  there  the  eukaryote  related  c o n t e n t s (Walker  Although  the  much  that  been  S t u d y i n g them may to  be  consistent  in a  for proteins  remaining  regulation  differ  DNA  (Britten  unable  to  markedly  in  1968).  expected  observed.  DNA  only  rule  o f genome s i z e  increase  o r g a n i s m c o m p l e x i t y d o e s n o t h o l d , many p a t t e r n s i n genome have  of  problems  genome c o d e s  s p e c i e s would  n-value  amount  1969,1971; Z u c k e r k a n d l 1974,1976) seems two c l o s e l y  problem  in'picograms.)  are  hypothesis that the  is  n for haploid  t h e r e i s so  i n t r a n s c r i p t i o n a l c o n t r o l and  and D a v i d s o n e x p l a i n why  of  Ohno 1 9 7 2 ) . The  involved  t h e i r DNA  (Whereas t h e  ( B i s h o p 1 9 7 4 ) , most e s t i m a t e s i n d i c a t e  small  is  et a l . 1972); t h i s  weights are t y p i c a l l y  species.  of  organisms.  c - v a l u e i s a r e l a t i v e measure o f  i t is difficult  organism  requirements, there  'C-value paradox'.  Absolute  much  t h e amount  r e f e r s t o number o f chromosomes, e.g.  weight.  (Bennett  that  r e q u i r e m e n t of  f r o m what i s known a b o u t  has become known a s t h e  3-5%  possible  by  methods  i s t o p r o g r a m an  But  DNA  Current  l e a d s t o the e x p e c t a t i o n t h a t  correlation  confirmed  undemonstrated.  vary w i t h the i n f o r m a t i o n  cell  been  a t l e v e l s below  t h a t t h e r o l e of DNA  i t s development  DNA  of  ( B e n n e t t and  1976),  intraspecific  and  many  with size  I t i s n o t known what t h e s e p a t t e r n s mean.  suggest a f u n c t i o n w i t h the dynamics  f o r ' e x c e s s ' DNA, of  'junk' and/or  turn  out  'selfish'  47  DNA  (see below), . or  particular  values  character.  At  not  of  both  present  'explanations' patterns  point  as  intended  The  are  to  factor  and  be  patterns.  reported  causing  the c o r r e l a t e d  almost  In Table  i n the l i t e r a t u r e .  but t o  o f DNA  other  quantity  seem  t o be e x h a u s t i v e ,  non-random d i s t r i b u t i o n  some  DNA  there  there  i n genome s i z e  to  illustrate  as  many  2 are l i s t e d This the  list is apparent  amount.  Explanat ions It  is  obvious  t h a t t h e r e a r e two b r o a d p o s s i b i l i t i e s f o r  t h e m y s t e r y DNA. I t c o u l d h a v e a f u n c t i o n , a n d many a u t h o r s  have  cautioned  that  DNA  that  i s ,  i t m i g h t n o t . I t c o u l d j u s t be  afterall,  frequently gets multitude The context less  "... r a t h e r  confounding  can  i s as  always  wide  certain  that  of g e n e r a t i n g a  1980).  as  effect.  our  minds  be p o s t u l a t e d " ( G o u l d  D o o l i t t l e and S a p i e n z a a  molecule  i n t h e f a c t t h a t even  DNA m i g h t have some p h e n o t y p i c  stories  (Dover  and  o f c o r r e l a t i o n and c a u s a t i o n a p p e a r s i n t h e  o f genome s i z e p a t t e r n s  stories  ignorant  o u t o f hand a n d i s q u i t e c a p a b l e  of sequence arrangements"  adaptive  for  an  'junk'  "Since are  function-  t h e range of fertile,  and L e w o n t i n  1979 i n  1 9 8 0 ) . The DNA c o u l d be o f a d a p t i v e  selection  regime  (causation),  or  new  value  merely  be  t o l e r a t e d by i t . I  will  now c o n s i d e r p u b l i s h e d e x p l a n a t i o n s  genome s i z e . T h e s e groups role  according  explanations to  i s o f t h e DNA t h a t  the  are  most  for patterns in  easily  treated  in  u n d e r l y i n g a s s u m p t i o n a b o u t what t h e  i s differentially  s p e c i e s so as t o p r o d u c e t h e p a t t e r n s .  distributed  across  TABLE Patterns  radiosensit1vity ( S p a r r o w and a l . 1968 )  2  i n Genome s i z e  v a r i e s d i r e c t l y w i t h DNA content M i k s c h e 1961; Bowen 1962; B a e t c k e  e t a l . 1967;  r a d i a t i o n - i n d u c e d mutation r a t e s vary d i r e c t l y with ( S p a r r o w e t a l . 1968; A b r a h a m s o n e t a l . 1973)  DNA  Underbrink  et  content  p r o p o r t i o n o f genome c o m p r i s e d o f r e p e t i t i v e DNA i n c r e a s e s w i t h genome s i z e ( a m p h i b i a n s : M i z u n o a n d M a c G r e g o r 1974; S t r a u s s 1971; c o n i f e r s : M i k s c h e H o t t a 1973; a n g i o s p e r m s : F l a v e l l e t a l . 1974) C o n t r a r y e v i d e n c e : V i c i a : C h o o i 1971b ) high  DNA c o n t e n t u s u a l l y (Stebbins 1966)  i m p l i e s much  and  heterochromatin  D N A / c e l l v a r i e s d i r e c t l y w i t h chromosome s i z e ( B a e t c k e e t a l . 1967; S p a r r o w e t a l . 1972) DNA  c o n t e n t may o r may n o t c o r r e l a t e (see Hinegardner 1976)  with  chromosome  number  D N A / c e l l v a r i e s d i r e c t l y w i t h n u c l e a r volume (Commoner 1964; B a e t c k e e t a l . 1967; S p a r r o w e t a l . DNA/cell v a r i e s d i r e c t l y with c e l l size ( a n i m a 1s:Commoner 1964; s e e d and p o l 1 e n : J o n e s and B e n n e t t 1973, J o n e s a n d Brown 1976 ) a d u l t b o d y s i z e i n c r e a s e s w i t h DNA content ( m o l l u s c s : H i n e g a r d n e r 1974a; D r o s o p h i 1 a plants)  m e i o t i c c y c l e time ( B e n n e t t 1971;  i n c r e a s e s w i t h DNA content and p o l y p l o i d y : B e n n e t t and  inbreeding/outbreeding different genera ( s e e Rees and  trends are Hazarika  significant  Rees  :Endow and  m i t o t i c c y c l e t i m e i n c r e a s e s w i t h DNA content ( V a n ' t Hof and S p a r r o w 1963; Yang and D o d s o n E v a n s e t a l . 1972)  1970;  Smith  1972)  Gall  minimum g e n e r a t i o n t i m e i n c r e a s e s w i t h DNA content ( B e n n e t t 1972; S m i t h and B e n n e t t 1975)  Bennett  1975;  Evans and  1972.  polyploid  Rees  1971;  1972)  1n d i f f e r e n t  1969)  1968,  directions  in  Table  14.  15.  2  (cont'd)  a n n u a l s h a v e l e s s DNA t h a n p e r e n n i a l s ( L a t h y r u s : Rees a n d H a z a r l k a 19G9; V 1 c 1 a : C h o o i B e n n e t t 1972; R a n u n c u l u s : S m i t h a n d B e n n e t t 1975) a n n u a l s h a v e more DNA t h a n p e r e n n i a l s ( L o l i u m : J o n e s a n d Rees 1967; A n t h e m i d e a e  :Nagl  1971; many  1974; P h a l a r i s  16.  t e m p e r a t e p l a n t s h a v e l a r g e r genomes t h a n t r o p i c a l p l a n t s ( A v d u l o v 1931; S t e b b i n s 1966; L e v i n a n d F u n d e r b e r g 1979)  17.  w i t h i n a g r o u p DNA i n c r e a s e s w i t h l a t i t u d e ( P i c e a s i t c h e n s i s : B u r l e y 1965. M i k s c h e 1967)  1971; P1nus  :Mergen a n d  18.  c o a s t a l p o p u l a t i o n s h a v e more DNA t h a n i n l a n d p o p u l a t i o n s ( P s e u d o t s u g a m e n z i e s i i :El-L-akany a n d S z l k l a i 1971)  19.  deep  20.  p r i m i t i v e s p e c i e s h a v e more DNA t h a n new s p e c i e s ( S t e b b i n s 1966; H i n e g a r d n e r 1976; L a t h y r u s :Rees a n d H a z a r i k a : J o n e s a n d Brown 1976; Bachmann e t a l . 1972)  s e a f i s h e s h a v e more DNA ( E b e l i n g e t a l . 1971)  than  their  plants:  s h a l l o w water  :Kadir  1974)  Thielges  relatives  1967; C r e p i s  21.  g e n e r a l 1 s t s h a v e more DNA t h a n s p e c i a l i s t s ( p l a n t s : S t e b b i n s 1966; t e l e o s t s : H i n e g a r d n e r 1968; a m p h i b i a n s : Bachmann e t a l . 1972; i n s e c t s : B i e r a n d M u l l e r 1969; mammals: Bachmann 1972; m o l l u s c s : H i n e g a r d n e r 1974a; e c h l n o d e r m s : H i n e g a r d n e r 1974b)  22.  t h e d i s t r i b u t i o n o f DNA c o n t e n t w i t h i n m a j o r g r o u p s d i s t r i b u t e d , skewed t o w a r d t h e h i g h e n d ( H i n e g a r d n e r 1976, a n d r e f s . t h e r e )  1s u s u a l l y a s y m m e t r i c a l l y  23.  f i s h f a m i l i e s w i t h s m a l l e r a v e r a g e genome genome s i z e ( H i n e g a r d n e r a n d R o s e n 1972).  have  24.  a v e r a g e genome s i z e o f a t a x o n 1s i n v e r s e l y r e l a t e d t o t h e number o f s u b t a x a ( B a c h m a n n e t a l . 1972; M l r s k y a n d R1s 1950; H i n e g a r d n e r 1968; G o i n a n d G o i n 1968)  size  also  less  variation in  50  E x t r a DNA p l a y s no' r o l e If  'excess'  i n phenotype  DNA h a s no e f f e c t  on p h e n o t y p e ,  then p a t t e r n s  i n DNA amount c o u l d be e x p l a i n e d by p r o c e s s e s a c t i n g within  t h e genome. S t o c h a s t i c p r o c e s s e s  patterns  in  genome  s i z e . T h i s would  could  internally,  generate  not e x p l a i n  random  t h e many n o n -  random p a t t e r n s r e p o r t e d . On t h e o t h e r h a n d , i t m i g h t increases probable,  and  decreases  i n which case  Hinegardner  (1976),  i n c a p a b l e o f DNA  in an  for  amount  of  DNA  orthogenetic example,  are  trend  that  not e q u a l l y  would  l a b e l s groups  i n c r e a s e , thus presuming  be  result.  as capable or  a difference  i n genome  organ i z a t ion. Means by w h i c h c h a n g e s i n genome  size  brought  unequal  tandem d u p l i c a t i o n ,  c h a n g e s i n chromosome number) a r e d o c u m e n t e d  (1970).  It  is  obvious  over, i n s e r t i o n ,  about  (polyploidization,  i n Ohno  crossing  are  that  these  processes  proceed without at l e a s t o c c a s i o n a l l y a f f e c t i n g an  organism  probable  viability.  net  direction  of  change,  disrupting  essential  i n c r e a s e over  have a lower p r o b a b i l i t y translation.  This  an  example,  that  (than d e l e t i o n s ) of  would  a n d Rosen  favor  genome  accumulate  (1972) c o n s i d e r t h e ' t i m e h y p o t h e s i s ' DNA o v e r e v o l u t i o n a r y  p o t e n t i a l l y e x p l a i n c e r t a i n p a t t e r n s such as more  by  time.  Hinegardner genomes  level  b u t a l s o by p r o b a b l e  I t d o e s n o t seem u n r e a s o n a b l e , a s always  having  the v i a b i l i t y of  So t r e n d s i n genome s i z e a r e a f f e c t e d n o t o n l y  insertions  that  cannot  a n d t h e r e b y b e i n g s u b j e c t t o s e l e c t i o n a t one  (internally). the  deletion,  DNA  time. This could  primitive  species  t h a n new s p e c i e s (#20) a n d g e n e r a l i s t s  l a r g e r genomes t h a n s p e c i a l i s t s  (#21, g i v e n t h a t  the  having  direction  51  of e v o l u t i o n (1972)  i s toward  found  no  s p e c i a l i z a t i o n ) but Hinegardner  significant  t a x o n a n d i t s genome s i z e . a  correlation  and Rosen  b e t w e e n t h e age o f a  Regardless of the e x i s t e n c e  correlation  or  existence  of  problems.  How  i s a genome r e s e t t o ' s m a l l ' a t t h e ' s t a r t '  species?  It  is difficult  mechanism r a t h e r It  be  like  i n that  sequences,  At appealing  again  size  patterns.  with  explain  the  during  reversal  selfish  what DNA  The  relative 1980)  sequences they  limits of  t o organisms  and  1980).  of  Selfish  i n c r e a s e over to  time.  proceed  without  in generating  genome  work  o f M i r s k y and R i s  evolution.  increased How c a n one  the  limit  to  the  accumulation  s p e c i e s ? O b v i o u s l y t h e r e would  of  have t o  to the t o t a l  amount o f DNA a t  selfish  invoke "metabolic disadvantage  DNA  w i t h l e s s s e l f i s h DNA"  "energetic  to  Crick  t h e phenotype  t h a t genome s i z e h a s b o t h  burden"  by s e l f i s h e l e m e n t s  appeal  on  of  reason?  determines  proponents  and  impossible  course  Dover  i n an o r t h o g e n e t i c t r e n d ? By a c h a n g e i n genome  in different  be l o g i s t i c a l  as  accumulation  affect  pioneering  the  o r g a n i z a t i o n ? F o r what And  a  p r o p o r t i o n o f ' j u n k ' DNA  s e l e c t i o n as a f a c t o r  Since  decreased  little  i t seems  idea,  promote t h e  1980; O r g e l  (1951) i t h a s been a p p a r e n t and  limited  r e a s o n why DNA m i g h t  point  to natural  more  i t s sequences  i s another  this  and  that a significant  ( D o o l i t t l e and S a p i e n z a replication  of  t h a n mere c o r r e l a t i o n .  emphasizes,  'selfish'  serious  t o c a s t t h i s h y p o t h e s i s i n terms of  i s a very d i f f e r e n t  (1980)  t h i s h y p o t h e s i s has o t h e r  non-  selection  and  the  some  (Orgel  and  on  Crick  d e s t r u c t i o n of needed  ( D o o l i t t l e and S a p i e n z a forces  point.  the phenotype.  1980) No d o u b t  52  metabolic  c o s t s would e x i s t  DNA.  the  In  justify  the  end  across  species.  amount of DNA  t h e c o n c e p t s of  existence  contribute nothing  f o r junk  of  to the The  relative  and  tolerances  or the  1980)  of  i t s presence.  important  understanding  understanding does  not  the  E x t r a DNA  junk  has  case,  the  of p a t t e r n s  of p a t t e r n s r a t i o of  and  i n genome  size  i n the  particular to  useful  explanation  selection  only  genome,  useless  the  can  regimes  of  the  to  the  w i t h i n genomes and  for  s e q u e n c e s , but  the e v o l u t i o n a r y f o r c e s  it  determining  1980b).  nucleotypic effects  and  of an  intermediate  a l p h a b e t i c c o d e --  between  i t s bulk  those  alone  could  of  mere  determine  of p h e n o t y p e , i n d e p e n d e n t o f s e q u e n c e . I f t h i s were  s e l e c t i o n c o u l d a c t not  ( a g a i n s t the accumulation  only  of  junk  of  larger  DNA  produces a phenotype w i t h  i n favour  of  smaller  o r s e l f i s h DNA),  but  resulting  this a from  'nucleotype'.  "The  character" idea  a  selective  in  advantage.  ' n u c l e o t y p i c ' e f f e c t , and such  sequence-independent  nucleotype (Bennett of  ( 1 9 7 8 , 1 9 8 0 a , 1980b) who  the  favour of  Bennett  s e t of  traits  effects  i s therefore a genotypic,  the  genomes  genomes u n d e r c o n d i t i o n s where a g r e a t e r q u a n t i t y  (1971) c a l l e d  The  selfish  "Intragenomic s e l e c t i o n i s c l e a r l y  (Cavalier-Smith  could play a role  a genie  for  s e l f i s h DNA in  evolution  clarify  DNA  aspects  DNA  would  s i g n i f i c a n c e o f c e r t a i n DNA  in i t s e l f  genome s i z e . . . "  or  requires  various  consequences of for  junk  explanation  explanation  Crick  it  'excess'  f u n c t i o n l e s s DNA,  (Orgel  as  but  the not  1981).  nucleotype expounds  appealed a  to  'nucleotypic  Cavalier-Smith theory'.  He  53  (1978) or  proposes  indirectly  two  f u n c t i o n s of DNA  involved i n coding  1.  c o n t r o l of c e l l  2.  determination  Function origins  (1)  in  and  Maaloe  o f an  1973;  Donachie  initiator,  specific  for  replicon  cell  is  1974)  this  i s d e t e r m i n e d by  may  be  surface area  important (and  pore  nucleocytoplasmic  size  bulk  number)  replicon  unit  models  of  of  (Sompyrac  repressor, of  the  concentration  repressed)  and  the  of  the  feels  that  i s determined. that  the  volume  i t s contents.  i t thereby with  of  DNA  accumulation  g r o w t h of a  c e a s e d t o be  because  transport  a  particular  assumes  the  is  of  When t h e c o n c e n t r a t i o n  a  d i v i d e s . Thus maximum c e l l  nucleus  by c e l l  (or  (1978)  number  t h a t p o s t u l a t e the  origins.  initiated  the  (1978) r e f e r s t o  attains  Cavalier-Smith  by  replicon  or the d i l u t i o n  initiator/repressor replication  volume.  (A  replication.) Cavalier-Smith  directly  and  determined genome.  than those  for proteins:  of n u c l e a r  is  the  volume,  other  a  He  determines  consequent  RNA  and,  attempts to apply  these  nuclear  effect  therefore,  on  'growth  rate'. Cavalier-Smith to  the  explanation  of genome s i z e p a t t e r n s  of t h e C - v a l u e p a r a d o x ) by and  K-selection " The  (and  functions  the r e s o l u t i o n  linking  up w i t h some i d e a s  about  r-  of c e l l  v o l u m e s and  growth r a t e s ,  and  theory:  great d i v e r s i t y  therefore  non-genic  of DNA  contents,  v a r y i n g balance  in different  which  small  favours  t h e r e f o r e low DNA  cells  C-values,  among e u k a r y o t e s species and and  between  rapid  results  r-selection,  growth  K-selection  from a  which  rates  and  favours  54  l a r g e c e l l s and values." The  link  (Cavalier-Smith  cell  evolving  by him.  size,  But  increasing  the  of  volume-dependent c o n t r o l of 1 9 8 0 b ) . But provide  i n the  the  i t d o e s not  only  a  small  "On larger cell  this  origins  p o i n t s out of  1980b)  b e t w e e n s e l e c t i o n and  larger  cytoplasm therefore  be as  to  nuclear DNA  is  (as  cannot  paradox,  it  involves  where i s t h e  the  The  used, not,  increase  lest  nuclear  suggestion a s has  origins  link  not  the  increases  is  nuclear  look at the  causal  transport  smaller c e l l s .  DNA,  the  to One  rate  the would  of  RNA  i t become r a t e l i m i t i n g the c e l l  i n c r e a s i n g t h e amount o f  pores.  "This  directly  rRNA  c y c l e t h a n do  unduly lengthen  increase  (Cavalier-Smith  such, which  l e t us  more  in larger c e l l s ,  done by  the  volume.  require  cell  g r o w t h and  in  s e c o n d p r o p o s e d f u n c t i o n of  expect s e l e c t i o n to  transport cell  the  So  of n u c l e a r  cells per  involved  the C-value  extra replicon  l a r g e r genome as  (Cavalier-Smith  "...  by  C-value?  the  t h a t of d e t e r m i n a t i o n  be  that  t h e genome)..." So  i t i s - the  or  for  would  replication."  s i z e : what t h e C - v a l u e c o n t r o l s more  volume." chain  theory  nucleus,  replicon DNA  selection  way  n e c e s s i t a t e a l a r g e r genome  b e t w e e n s e l e c t i o n and  C-  slow growth i s  given  direct  explanation  f r a c t i o n of  h i g h DNA  u n d o u b t e d l y s e v e r a l ways of  and  n e x t s e n t e n c e he  fundamental  since  case,  are  a simple  number  l a r g e c e i l s and  i n any  "Though t h e r e  larger cells,  therefore  1978).  between K - s e l e c t i o n and  never e x p l a i n e d larger  s l o w g r o w t h r a t e s and  surface  c y c l e . This  s k e l e t a l DNA area  and  i s therefore  been i n c o r r e c t l y  to  could  (S-DNA) so  t h e number of  that  the  excess  s t a t e d , to  slow  55  d e v e l o p m e n t but development increases In o t h e r favours  in c e l l  increased for  Cell  replicon values  which  "...  size."  otherwise  C - v a l u e . At  v o l u m e can  origins  be  with  lengthening  and  short  of  RNA'  this point  little  what  should  life  never  due  cycle  large  c y c l e time  that  i t i s apparent that no  effect  i n c r e a s i n g the  e f f e c t on  really  by  transport)  requirements given  with the  two  of  large  C-  to  prevent  and  has  time.  o c c u r on my  theory  --  n o t ? A l a r g e genome (and few  C-  number  C - v a l u e , and  to r - s e l e c t i o n  "K-  on  i s t h a t h i g h C - v a l u e o r g a n i s m s have s m a l l  c y c l e s . " Why  of  1980b)  s l o w g r o w t h " has by  slowing  caused  for shorter c e l l  increased  of c e l l  be  (Cavalier-Smith  l a r g e c e l l s and  been o b s e r v e d --  replicon  non-protein  not cells  high  rate  o r i g i n s would f u l f i l l coding  the  functions given  at  outset. A final  caution  Cavalier-Smith o r i g i n s are  are  shown,  quantity (Bennett  that  the  not  entirely  DNA  functions  they  At p r e s e n t may 1971).  have  presents are  not  by  Replicon  sequences,  role  us w i t h  and  i s the  one  of  RNA.  s e v e r a l new  sufficient  a l l that e x i s t s a  proposed  sequence-independent.  i s t o code f o r s t r u c t u r a l  Cavalier-Smith  theory'.  is  presumably p a r t i c u l a r  s t r u c t u r a l DNA  have  would  i n l a r g e c e l l s are  excessive  the  to p r e v e n t the e x c e s s i v e  words i t i s s e l e c t i o n  selection value.  rather  ideas  to form a suggestion  sequence-independent  but,  as I  'nucleotypic that  DNA  (nucleotypic)  role  56  DNA d i f f e r e n c e s Another generality call  the  a r e i n amount o f pr i m a r y DNA  selectionist in  hypothesis  explaining  hypothesis  H i n e g a r d n e r a n d Rosen  t h i s hypothesis  great  genome s i z e p a t t e r n s  'loss-of-parts'  (1968,1976;  of  i s what I s h a l l  advanced  by  a r e as f o l l o w s :  while others  their  DNA c h a n g e a n d l o s s i s e v o l u t i o n t o w a r d  and  eventual  extinction."  Specialization  (Hinegardner  specialization  1976)  i n v o l v e s l o s s of p a r t s  and/or  functions.  s p e c i a l i z e d f i s h w o u l d be e x p e c t e d t o have f e w e r p a r t s ,  since  the  adaptation use  of  derivative  c o n d i t i o n of s p e c i a l i z a t i o n  to a restricted  a l l structures  mode o f l i f e present  is  hardly necessary;  examining have  i n the generalized  even t h e g r o s s  intermuscular the t r e n d and  bones, s k u l l  parts, i t  generalized  t o h a v e more s e p a r a t e  i n t h e h y o i d a p p a r a t u s and g i l l  form.  p i c t u r e one g e t s  f i s h anatomy shows t h a t t h e  more p a r t s . They t e n d  i s the  not r e q u i r i n g t h e  Though i t w o u l d be p o s s i b l e t o q u a n t i t a t e f i s h  arches,  more  from  fishes elements  vertebrae,  bones, and f i n r a y s . C e r t a i n l y  i s not i n the opposite  direction."  (Hinegardner  R o s e n 1972)  4. DNA c o d i n g There  are  f o rthe lost several  traits  difficulties  genome s i z e p a t t e r n s . One i s t h e trends,  size,  DNA "The c o n s e q u e n c e  of  "A  genome  c a n n o t , o r do n o t .  I n g r o u p s t h a t do n o t i n c r e a s e  3.  Hinegardner  1 9 7 2 ) . The main c o m p o n e n t s o f  1. Some g r o u p s o f o r g a n i s m s c a n i n c r e a s e t h e i r  2.  potential  that  some  c a n be l o s t ,  and i s .  w i t h t h i s e x p l a n a t i o n of  postulation  of  orthogenetic  groups can and o t h e r s cannot i n c r e a s e  their  57  DNA.  No  the  interesting  is  reason for these trends question  were as  "Generalized  will  be  with other  of  presence or  definitions  of  used to d e s c r i b e  contrast, a specialized members  direction  of  is  evolution  generalized  and  follows:  numerous f e a t u r e s  the  Another d i f f i c u l t y  of w h e t h e r t h e  t o w a r d s p e c i a l i z a t i o n . The  specialized  i s given.  its  members  of  their  share  taxon.  o r g a n i s m shares fewer f e a t u r e s taxon  absence  organisms that  of  and  will  certain  differ  In with  f r o m them i n  features."  (Hinegardner  1976) These of  definitions  imply  specialization,  Evolution  is  definition there  making  change,  characteristics  it  (unless  that evolution w i l l the  and  will  if  all  the  to  require  l o s s of DNA.  i s viewed  trend means  direction  tautological. gain  specialization  s u b t a x a change i n the  i s not  authors metabolic enzyme  Some modes of  ( H i n e g a r d n e r and  an  connection  f e w e r p a r t s and  specialization  the  i n the  or  by  loss  the  same way  of  above so  that  i s no d i v e r s i f i c a t i o n ) .  and  lost  change  imply  A t h i r d problem i s the  it  stated  be  within  1972)  l o c u s . At any  not  1976)  of  assume  (Teleostei),  oviparity. that  form  of  although  Also,  some  t h e more p r e c i s e of  an  r a t e , t h e m e c h a n i s m by w h i c h u n u s e d DNA  is  i s never e x p l a i n e d . same r e a s o n t h a t DNA Hinegardner(1976)  as a p a r t i c u l a r  the Atherinomorpha  r e q u i r e m e n t s of  w o u l d seem  f u n c t i o n s . V i v i p a r i t y , f o r example,  Rosen  Valentine  specialization  specialization  obvious s i m p l i f i c a t i o n  (e.g.  between  s p e c i a l i s t s r e q u i r e more c o p i e s  And  why  t h a t has  are  DNA  increases  not  f a l l e n into disuse  distinguishes  two  types  is of  lost  for  lost? DNA  in  58  organisms. These  "There  are  the  ones  are  i n c l u d e genes and DNA.  the that  affect  constrained  their control. This  duplication;  undoubtedly probably  this  lies  is  will  be  than  the  p o p u l a t i o n s of n u c l e o t i d e i s s e c o n d a r y DNA  removing  serious only  relevant  sequences",  is a relatively  produced  however,  the  two  area  types  are  and c a n be e x a m i n e d as  sequences." retained  fuzzy  (Hinegardner  1976)  i f there i s s e l e c t i o n  capable most  w i t h the l o s s - o f - p a r t s h y p o t h e s i s i s t h a t  i t is  primary f o r a few  DNA,  fallen  two  i n t o d i s u s e ? The  to and  sequences A  a p i e c e of p r i m a r y DNA  problem  primary  DNA.  overlap  and  called  secondary  between t h e two;  bigger  Why  the  sequences.  events i n the organisms,  Then t h e r e a r e t h e much l e s s c o n s t r a i n e d  by  of  selectively  "the  reasons  unimportant part  selectively  i t is likely of  genome  constrained  that primary  size  DNA  differences.  These r e a s o n s a r e : 1. P r i m a r y a small  DNA,  a c c o r d i n g t o most e s t i m a t e s , c o m p r i s e s o n l y  proportion  of  the  genome.  c o n s i d e r s t h i s and c o n c l u d e s t h a t our  average  organism  proportion likely DNA, But  then  a c c o u n t s f o r 0.6  I f primary  is  s e l e c t i o n - d e t e r m i n e d changes  u n l e s s t h e q u a n t i t y o f s e c o n d a r y DNA  rapid  DNA  a  secondary  DNA  "Changes  t h a n i n t h e p r i m a r y DNA."  24  small  secondary  i s very  or l o s s e s would  (Hinegardner  to  i n i t are  t o be swamped by c h a n g e s i n t h e amount o f  .in  (1976)  "At t h e maximum t h e n , i n  p r i m a r y DNA  p e r c e n t o f t h e h a p l o i d DNA."  Hinegardner  1976,  stable. be more p.195)  59 T a b l e 3. The r a n g e i n genome s i z e i n teleost taxa as a proportion o f t h e minimum a n d maximum genome m e a s u r e d i n e a c h t a x o n . The minimum ( o r maximum) genome s i z e c a n be viewed a s a g e n e r o u s o v e r - e s t i m a t e o f t h e p r i m a r y DNA f o r the group. C a l c u l a t e d from t h e d a t a of H i n e g a r d n e r and Rosen (1972).  DNA T e l e o s t Taxon Osteoglossomorpha Osteoglossiformes Osteoglossoidei Mormyriformes Elopomorpha Anguilliformes Clupeomorpha Protacanthopterygii Ostariophysi Cypriniformes Characoidei Cyprinoidei Siluriformes Callichthyidae Scolpelomorpha Paracanthopterygii Gadiformes Batrachoidiformes Lophiiformes Acanthopterygii Atherinomorpha Exocoetoidei Cyprinodontoidei Atherinoidei Percomorpha Gasterosteiformes Gasterosteoidae Syngnathoidei Scorpaeniformes Scorpaenoidei Hexagrammoidei Cottoidei Perc iformes Percoidei Sphyraenoidei Labroidei Blennioidei Gobioidei Scombroi d e i Stromateoidei Anabantoidei Pleuronectiformes Pleuronectoidei Soleoidei Tetraodontiformes Balistoidei Tetraodontoidei  min. .77 .77 .77 1.0 1.2 1.4 .77 2.7 .65 .65 .71 .65 .88 1.7 1.2 .68 .68 1.7 .74 .48 .72 .74 .72 1.1 .48 .58 .58 .64 .76 .96 .79 .76 .59 .72 .83 .91 .81 1.2 .88 .80 .59 .65 .65 .65 .48 .64 .48  max. 1.3 1.3 1.0 1.2 2.5 2.5 1.9 3.3 4.4 2.2 2.1 2.2 4.4 4.4 1.2 3.0 .98 3.0 1 2.1 1.6 1.2 1.6 1.3 2.1 .70 .70 .66 1.4 1.4 .99 1.1 . 2.1 1.4 1.2 2.1 1 1.4 1.1 .81 .88 1.1 1 1.1 1.1 1.1 .90  (pg) — Range % of % of max. min.  # of spp.  41 41 23 17 52 44 59 18 85 70 66 70 80 61 0 77 31 43 26 77 55 38 55 15 77 17 17 3 46 31 20 31 72 49 31 57 19 14 20 1 33 41 35 41 56 42 57  8 4 3 4 4 3 6 3 75 43 22 21 32 8 2 12 5 4 3 168 19 5 11 3 149 6 3 3 15 4 5 6 104 68 2 5 6 3 7 2 9 12 10 2 10 5 5  69 69 30 20 108 79 147 22 577 238 196 238 400 159 0 341 44 76 35 338 122 62 122 18 338 21 21 3 84 46 25 45 256 94 45 131 23 17 25 1 49 69 54 69 129 72 131  60  2.  I f the  d i f f e r e n c e s i n genome s i z e l i e i n p r i m a r y DNA  differences  i n genome s i z e b e t w e e n r e l a t e d s p e c i e s  l e s s t h a n t h e e n t i r e amount o f p r i m a r y DNA  i n the  derived  the  from  shows t h e  (most l i k e l y  generalized  data  given  of H i n e g a r d n e r and  The  of a v e r y  primary  DNA  in  The  not  greater  estimate  than  size  are  due  of  24%).  the was  1972 as  is and a  a l l , of  the  of  and  the  reason  to  differences  amounts of  seems  than a  amount 24%  is  secondary  unimportant, • i f  implausible.  is  often  r e d u n d a n c y f o r gene d o s a g e e f f e c t s  speculated  that  the  causal  p o s i t i v e c o r r e l a t i o n b e t w e e n genome s i z e and i s t e m p e r a t u r e , and is adaptive "... the  3  taxa  This  to varying  l o s s - o f - p a r t s hypothesis  variation is differential It  Rosen  g e n e r a l l y much g r e a t e r  t h a t a t l e a s t some, i f n o t  genome  DNA.  generous  be  maximum genome w i t h i n a  (e.g. Hinegardner's e s t i m a t e  range i s o f t e n  DNA  ranges are  fraction  believe  Table  r a n g e i n genome s i z e w i t h i n t e l e o s t  taxon.  must  a small f r a c t i o n )  species.  p e r c e n t a g e of b o t h t h e minimum and  then  t h a t has  in cooler One  way  l e d to the  to increase  dependence  w i t h each  10°C.  limiting  factor  latitude  suggestion  the  (#16,#17)  t h a t more  DNA  environments.  number of gene c o p i e s .  strong  factor in  on  rise  up  with  protein production Since  enzyme  temperature t o an respect  t e m p e r a t u r e s i n p l a n t s and  i s to  activity  (approximately  optimum)  it  to e f f i c i e n t  cold-blooded  increase has  doubling  could  be  growth at  animals.  a  Then,  one low any  61  organisms  having d u p l i c a t i o n s of r a t e - l i m i t i n g  have an i m m e d i a t e s e l e c t i v e a d v a n t a g e . . . "  genes would  (Sparrow  et a l .  1972) . Stebbins(1966)  and  others  have c a u t i o n e d  DNA  i s probably not d i r e c t l y  adaptive  few  ( p l a n t ) g r o u p s have a h i g h DNA  strictly  tropical  S t e b b i n s s u g g e s t e d t h a t gene development,  which  l a t i t u d e s . He organized  that  the duration  the chain  be  in  a  time-chain,  since  rate  at  gene  still  (in British  climates,  multiples  one c o p y a c t i v e a t a t i m e ,  (1982) p r o p o s e d  a  i n time of c e l l  permit high  flora).  or only  so  i s s e t by t h e l e n g t h  different  model  i s that  Plants  and  cell  i s i n h i b i t e d at (low)  r a t e s of c e l l  which  grow  e x p a n s i o n , and  in  large  nuclear  envelope  DNA  continually  i n t h e warm s e a s o n o f v a r i a b l e  be due t o d o s a g e r e p e t i t i o n  for a  to  t h e r e can  expansion  genomes. The a s s o c i a t i o n o f f a s t c e l l  genome c o u l d  t o t h e need  of  cooler  s h o o t e x p a n s i o n a t l o w e r t e m p e r a t u r e s means h i g h e r  have s m a l l  a  content.  the  slower  which  They c i t e e v i d e n c e t h a t m i t o s i s  show t h a t  large  be  of a stage i n development  of separation  temperatures that  warm  to  c o n t e n t a n d t e m p e r a t u r e . The i d e a  a strategy  content  has  governs  content  of c o p i e s .  DNA  division.  redundancy  generally  Grime and Mowforth relate  temperatures  (1966) p r o p o s e d a model i n  are  of  t o low  that high  climates,  expansion  with  requirements, or (see  nucleotypic  effects). Grime  and  Mowforth  i n f l u e n c e genome s i z e "As  (1982) s u g g e s t t h a t  could  i n animals, t o o .  m i g h t be e x p e c t e d , s m a l l  warm-blooded  temperature  animals  and  genomes a r e c h a r a c t e r i s t i c i t i s particularly  of  interesting  62  that  r e p t i l e s which f l o u r i s h  uniformly  small  genomes  with exceptionally  in  l a r g e genomes and  p e r m e a b l e s k i n , so t h e  body  of  the  point  of  environments.  centered  It  as e x p e r i m e n t a l  to  several  the  material  l o s s of p r e v i o u s l y  duplication.  structural  genes,  importance  of  regulation  r e p e t i t i v e DNA Introns  Whereas  Ohno  Britten  and  and  suiting  the  in  t h e DNA  be  s u g g e s t i o n s of  tried  and  their  important  this  type'.  redundant  genes w i t h o u t  needed,  genes.  s e v e r a l genes have e v o l v e d was  p r i m a r i l y concerned  Davidson  to  (1971)  stress  i n order  to evolve  explain  the  by with the  new  gene  existence  of  i n t h i s manner. (intragenic  t r a n s c r i b e d , but  regions) s p l i c e d out  (1978) s u g g e s t e d t h a t  evolution:  that  existing,  h a v i n g r e d u n d a n t DNA  systems,  to  existing  i n w h i c h t o t e s t new  i s e v i d e n c e t o show t h a t  of  low  up  i m p o r t a n c e of e x t r a , o r  And  Gilbert  species  DNA  'adaptedness', or  i s a d i f f e r e n t idea  the  that are  moist  m a i n t e n a n c e of  'extra'  conditions  suffering there  f o r the  around  organisms  Ohno (1970) s t r e s s e s  gene  respiratory  adaptabi1ity  ' a d a p t a b i l i t y ' . There are  DNA  The  species  b e h a v i o r o f most  i n s o l a t i o n and  proposed f u n c t i o n s  have  properties  for  cells.  have  t h e m a i n t e n a n c e of a  e c o l o g y and  a v o i d a n c e of  influences  All  conditions  temperature."  E x t r a DNA  this  the  hot  whereas amphibia i n c l u d e  s y s t e m of a m p h i b i a n s d e p e n d s on  involve  dry  are  portions  o f RNA  of  the  genome  before t r a n s l a t i o n .  i n t r o n s serve to  increase  the  rate  63  1.  large  s c a l e changes c o u l d  altered a splicing 2.  they  could  the  frequency  h a n d , e x t r a DNA m i g h t r e t a r d failure  that  recombination  of  the  progress  many d u p l i c a t e d  gene l o c i . "  out  recombination.  polyploids  which  spacing  evolution.  c h a r a c t e r i s t i c s c a n b e s t be a s c r i b e d evolutionary  of  a l s o be i m p o r t a n t t h r o u g h t h e  of genes i n complex o r g a n i s m s t o f a c i l i t a t e  "... t h e  mutation  of a s i n g l e gene.  R e p e t i t i v e DNA c o u l d  On t h e o t h e r  a  pattern  increase  between p a r t s  be c a u s e d by  to  evolve  new  to the retardation  of  r e s u l t s from t h e p r e s e n c e of  (Stebbins  1966)  DISCUSSION The is  existence  t o be l e a r n e d  There  i s much  of the C-value paradox i s evidence that  a b o u t t h e s t r u c t u r e a n d f u n c t i o n o f t h e genome. more  DNA  in cells  than i s r e q u i r e d  p r o t e i n s , and i f t h e remainder p l a y s can  congeneric  differ  much  species,  a role in  with apparently  t o code f o r  regulation,  why  s i m i l a r requirements,  s o much i n DNA c o n t e n t ? What e l s e c o u l d  t h e DNA be  doing  there? There  a r e many non-random c o r r e l a t i o n s o f genome s i z e  physiological, 2).  These  e c o l o g i c a l , and taxonomic p a r a m e t e r s are  clues  d i s t r i b u t e d DNA. S i n c e explain  with  the  many o f t h e  role  of  patterns  the are  Table  differentially difficult  to  e x i s t i n g m o d e l s o f t h e genome, t h e d i f f e r e n t i a l l y  d i s t r i b u t e d DNA c o u l d the  to  (see  with  be t h e same a s t h e  two a s p e c t s o f t h e p a r a d o x .  'extra'  DNA,  linking  64  I  have  reviewed  the  explanations  size,  t r e a t i n g them a c c o r d i n g  what  t h e e x t r a DNA  and  this  there  to the  underlying  i f not  be m u l t i p l e c a u s e s u n d e r l y i n g  Furthermore,  many  of  the  an  i n genome  assumption  i s . Many o f t h e s e e x p l a n a t i o n s  i s at l e a s t a reminder,  could  of p a t t e r n s  'make  sense',  indication,  the patterns  explanations  are  of  that  observed.  not  mutually  exclusive. As can  an i l l u s t r a t i o n  consider  be b r o u g h t t o b e a r on  Table  2).  could  the  t h e number o f e x p l a n a t i o n s annual/perennial  that  perennials  because they a r e longer  have  a  that  DNA, a n d t h a t with  the  greater  the metabolic  selection  their  cost a  short  against  life  (sequence-independent)  annuals  and  minimum  life  useless the  meiosis),  DNA,  regulatory  requirement  DNA  generation  cycle,  DNA  in  effects  in a so  there  annual are  (faster  o r ( f o r some r e a s o n ) s m a l l e r c e l l s .  'parts',  and  therefore  Mowforth  (1982) would l o o k  annuals  was c o n f i n e d  from  require see  less  i f the  species.  nucleotypic  mitosis  Hinegardner  they and might  and  with  Grime  and  period  for  DNA.  growth  is  t o t h e warm p a r t o f t h e s e a s o n , when e x t r a  DNA w o u l d n o t be r e q u i r e d separated  to  species  have l e s s DNA b e c a u s e time  a  or ' s e l f i s h '  suggest that annuals are s p e c i a l i z e d , u s u a l l y simpler fewer  and  c y c l e s . Or one c o u l d  o f i t were g r e a t e r  Another a l t e r n a t i v e i s that  need a s h o r t e r  regulatory  DNA d i f f e r e n c e was due t o ' j u n k '  f a s t development and  stronger  in  One  l i v e d a n d t h e r e f o r e must c o n t e n d w i t h  more v a r i a b l e e n v i r o n m e n t d u r i n g assume  (#14,  A n n u a l s g e n e r a l l y h a v e l e s s DNA t h a n p e r e n n i a l s .  assume t h a t t h e d i f f e r e n c e l i e s  argue  pattern  that  mitosis.  for  fast  Someone  cell else  expansion might  point  temporally out that  65  a d a p t a b i l i t y might the  additional  be more i m p o r t a n t f o r p e r e n n i a l s ,  DNA  experiments could  they c o n t a i n  distinguish  among  h y p o t h e s e s , but s e v e r a l would There be s o l v e d . and  could  that  be t o t h a t e n d . C a r e f u l  some  of  these  be q u i t e d i f f i c u l t  a r e two c o n c e i v a b l e  and  alternate  to f a l s i f y .  ways i n w h i c h t h i s p a r a d o x  One i s t h a t a f u n c t i o n be f o u n d f o r  the  might  extra  DNA,  t h a t t h i s new u n d e r s t a n d i n g make us r e a l i z e why t h e v a r i o u s  trends is  exist —  the  what t h e i r  possibility  'common d e n o m i n a t o r '  i s . The  o f n o t i c i n g s u c h a 'common d e n o m i n a t o r ' ,  g r a n d c o r r e l a t i o n t h a t accommodates a l l o f t h e and  exploring  the r e a l i t y  DNA) t h a t c o u l d  second  patterns  a  found,  o f m e c h a n i s m s ( w i t h assumed r o l e s o f  p l a u s i b l y generate the patterns.  Genome S i z e a n d R a t e s o f E v o l u t i o n The the  grand c o r r e l a t i o n 'the f a s t e r the  smaller  patterns. such  the  Ancient  genome  size'  or ' l i v i n g  because t h e i r  could  fossil'  be  specialists  generalists.  Biotic  in  specialists's  themselves  in  than  to  generation  often a  than  is  they  (#21).  slow f o r a  long  would  more  agree  role  often  The  in find  Specialists  more  i t does f o r p e r e n n i a l s ,  inversely  f i t a l l as  greater  races'.  generally d i f f e r  t o d i r e c t i o n a l s e l e c t i o n . That  taxon  and  'arms  generalists  dispersing annuals could  to  recognized  people  factors play a  niches,  coevolutionary  genomes  evolution,  more o f a 'Red Queen' s i t u a t i o n t h a n  (evolving)  defining  smaller  are  r a t e o f c h a n g e h a s been v e r y  are  of  argued  species  t i m e -- and t h e y h a v e l a r g e r genomes. M o s t that  rate  have  environment of from  generation  e x p o s i n g them more  the average  genome s i z e  r e l a t e d t o t h e number o f s u b t a x a  of  (#24),  66  t e m p e r a t e genomes be sea  fishes  have  bigger  more  (#19), are a l l f a i r l y  A New  Explanation  DNA  genetic  this  grand  this  of  selection  can  modes  means  characteristic  that  conservatives  and  i n f l u e n c e d by phenotype.  a s s o c i a t i o n of phenotypic  have  indirectly would f a v o r  a  of  these  these  phenotypic  genome  size  v a r i a n t s i n the p o p u l a t i o n  non-random  disruptive  the c h a r a c t e r i s t i c  variants.  smaller select for  If,  with  modes  of  that  the  variants in or  will  can  rate  of  any  be  the  other  phenotypic indirectly acting  on  about  by  production  of  come  f o r e x a m p l e , s m a l l e r genomes p r o d u c e  r a t e , t h e n on a v e r a g e p h e n o t y p i c genomes  and  smaller  selection  genomes.  for  variants  variants  Stabilizing  size.  S t a t e d more p r e c i s e l y , my  new  hypothesis i s :  will  selection  l a r g e r genomes. I n t h i s manner r a t e of e v o l u t i o n  be c o r r e l a t e d w i t h genome  or  evolution-  selection  distribution  the  Neo-Darwinian  I hypothesize  both  favor  or  might  change i n  i s n o n - r a n d o m l y d i s t r i b u t e d among  v a r i a n t s at a g r e a t e r will  is  From  size.  that  that  relatives  a c t i o n of e i t h e r d i r e c t i o n a l  genome  directional  This  Evolution  t h e p r o b l e m becomes how  selection  This  water  deep  Patterns  population.  observation  of  shallow  and  c a u s a t i o n . What m e c h a n i s m  the  influence  i n the  population.  a  implies  s e l e c t i o n . So  causing  imply  ones ( # 1 6 ) ,  i n ' r a t e of e v o l u t i o n ' t e r m s .  correlation?  disruptive  answer l i e s  cast  f o r Genome S i z e  constitution  perspective  than t h e i r  easily  C o r r e l a t i o n d o e s not explain  than t r o p i c a l  can  67  1. The  function  genome  size  2.  t h e ' m y s t e r y ' DNA r e s p o n s i b l e f o r most  patterns  production; genetic  of  more  is  regulation  DNA means s l o w e r  of  variation  production  of a d d i t i v e  variation.  Secondary s e l e c t i o n (Chapter variation  Two) c a n a c t v i a  t o i n f l u e n c e DNA amount, g i v e n ( 1 ) .  3. D i r e c t i o n a l production  selection  of g e n e t i c  indirectly  variation,  favors  Unfortunately  the hypothesized  r a t e s of a d d i t i v e g e n e t i c There  is  link  size.  Hypothesis  b e t w e e n genome s i z e a n d  variation production only  greater  and s m a l l e r genome  S u p p o r t f o r t h e Genome S i z e / V a r i a t i o n P r o d u c t i o n  established.  phenotypic  has  circumstantial  yet  evidence  to  be  i n the  literature. Pierce  and  relationship, and and  genetic  (1980)  i n the species  reported  strong  negative size  v a r i a t i o n a s m e a s u r e d by a v e r a g e h e t e r o z y g o s i t y  (H)  of  they  a  e x a m i n e d , b e t w e e n genome  percent  constitute  Mitton  polymorphic  loci  evidence supporting  the hypothesis  1. The s t a t i s t i c s H a n d P additive variation  or  ( P ) . Their  cannot  non-additive  be  f o r these  equated  variation.  influences evolutionary  work  with Only  does n o t reasons: either additive  responsiveness.  2. H a n d P a r e n o t m e a s u r e m e n t s o f v a r i a t i o n  product ion  per  se. 3. L a r s o n  (1981)  statistical  severely  analyses  and  criticized concluded  P i e r c e and M i t t o n ' s that  the  reported  r e l a t i o n s h i p was u n d e m o n s t r a t e d . There  i s ,  however,  considerable  literature  that  is  68  explicitly  or  promoting  or  question  implicitly  suggestive  suppressing  rates  t h a t needs t o be be  of a r o l e of DNA of  variation  a n s w e r e d i s , "Does  observed  to  differentially  generally  i n c r e a s e or d e c r e a s e g e n e t i c  Some " n u c l e o t y p i c e f f e c t s " production greater times  as  w e l l as  other  evolutionary  rate  phenotypic  cause  slower  cell  therefore, decreased evolutionary  ( p a t t e r n s #10,  ( H o t t a and  Stern  replication,  #11),  1 9 6 5 ) , had  e i t h e r by  Selection  for  generation DNA  bulk  generations  and,  responsiveness.  or  any  variation  production.  Another n u c l e o t y p i c e f f e c t c o u l d occur divisions  production?"  influence  longer  DNA  organisms  would s e l e c t f o r s h o r t e r  d i v i s i o n s and  The  of  across  traits.  as w e l l as more a d d i t i v e v a r i a t i o n  might  production.  variation could  either  the"~^ind  distributed  of DNA  in  of  i f the  certain  i n f l u e n c e on  facilitating  s p e e d of  phases  the  of  fidelity  error-checking  cell them  of  DNA  processes  by a l l o w i n g more t i m e f o r t h e p r o p e r o r g a n i z a t i o n and  or  alignment  of g e n e t i c m a t e r i a l . The higher  organizing replication  maintain  the  efficient  operation  and  function fidelity.  proper  spatial  of t h e c e l l  of "...  stages  a i d i n the  initial  l o n g been c a u s a l l y l i n k e d t o m u t a b i l i t y  But  production, ( Y u n i s and B  heterochromatin f o r e x a m p l e by  Yasmineh  may  allowing  also  Yasmineh  increase  chromosomal  of  1971).  (Thompson variation  rearrangement  1 9 7 1 ) . S u p e r n u m e r a r y chromosome segments  chromosomes a r e b o t h h e t e r o c h r o m a t i c .  the  meiosis  alignment  Asynapsis  to  help for  of  prior  1962).  and  may  chromosomes has  (Yunis  lead  necessary  through the  synapsis  may  heterochromatin  relationships  m i t o s i s " , f o r e x a m p l e i t may to  heterochromatin  and  They h a v e been o b s e r v e d  69  t o b o t h i n c r e a s e and 1972;  Carlson It  for  decrease recombination  rates  (refs.  1978).  i s r e l e v a n t t o ask  what f r a c t i o n  t h e d i f f e r e n c e s i n genome s i z e . On  of DNA  is  t h e one  #3).  i n amount of  Evidence suggests  intermediately Stebbins generally other  has  have  hand,  repetitive  is  not  evidence that other  of as  marshalls  a  shield  a  suggestion "... in  the a  provoke  the  that  variation.  i s Hsu's  genomes On  the  proportion  of  (Chooi  1971),  DNA,  may  and vary  1981).  (1975)  "bodyguard  c i r c u m s t a n t i a l evidence  constitutive  heterochromatin  "Mutagens, c l a s t o g e n s (Hsu  1975).  A  or  even  preliminary  Muller  inertia; a r e not  redundancy l e a d s  Bachman e t a l . ( 1 9 7 2 )  to  the  describe  (1969) t h a t  r e p e t i t i v e n e s s inherent  natural  and  hypothesis.  of B i e r and  r e p e t i t i v e DNA  of  i n Larson  common i d e a t h a t g e n e t i c  genetic  most  of a l l r e l a t i o n s h i p s between  against  his  that  larger  single-copy  nucleus..."  r e d u c t i o n of e x p r e s s e d the  e.g.  considerable  proposal  experiment supported  with  c h a n g i n g w i t h genome s i z e  v i r u s e s a t t a c k i n g the  is  evidence  production  his  It  some  variation  in  (pattern  p r o p o r t i o n of h e t e r o c h r o m a t i n .  supported  He  functions  plants  best  hypothesis".  1970)  have  largely  resides in heterochromatin,  that  fractions,  the  amount and  favor  Yasmineh  w i t h genome s i z e . ( r e f s .  Probably DNA  and  DNA  a greater  DNA  significantly  (Yunis  noted  there  are  i n t e r m e d i a t e l y r e p e t i t i v e DNA  repetitive  (1966)  responsible  hand, t h e r e  been numerous r e p o r t s t h a t genome s i z e d i f f e r e n c e s differences  i n Rees  i n l a r g e r genomes  mutations  in  single  q u a n t i t a t i v e l y important  selection,  even  if  the  results  copies  of  enough  to  genes  are  70  functional." Stebbins  (1966) a s c r i b e s t h e  retarded  evolution  p l a n t s t o t h e p r e s e n c e o f d u p l i c a t e d gene l o c i . mutations, an  as  One  problem i n a p p l y i n g  which a r e  not  polyploid  extensive  tandem  i s that  duplication  1 9 7 6 ) . Some e v i d e n c e a g a i n s t is  provided  by  It  has  in  be  a  correlated  DNA  been  of  redundant to species  existence  supported  of  (Price  redundancy  who f o u n d t h e r a t e o f diploid  yeast  to  be  haploids.  general  more DNA, t h a n d o e s v a r i a t i o n of  not  populations  truth  organisms, v a r i a t i o n suppression  amount  assumed  t h e "coverup" e f f e c t of  that of c o i s o g e n i c  might  f o r " by  the  i s that  have l e s s o f  coverup notion  P a q u i n a n d Adams ( 1 9 8 3 ) ,  variation production almost twice  this  polyploid  The i d e a  long as they a r e not dominant, w i l l  i m p a c t on p h e n o t y p e i f t h e y a r e " c o v e r e d  copies.  of  t h a t , a t l e v e l s common i n  r e q u i r e s more o r g a n i z a t i o n , a n d  promotion.  The  hypothesis  and r a t e of v a r i a t i o n p r o d u c t i o n  that  are negatively  i s t e s t a b l e (Hsu 1975), b u t t h e c r i t i c a l  experiments  have y e t t o be p e r f o r m e d .  CONCLUSION I  have  critically  reviewed the e x i s t i n g  genome s i z e p a t t e r n s . Some scope.  The  more  are  general  "special-case" explanations  explanations f o r and are  narrow  in  internally  i n c o n s i s t e n t , and u n t e s t a b l e . The smaller  c o r r e l a t i o n "the f a s t e r t h e genome s i z e "  patterns. causally  It  i sconsistent  i s hypothesized  connected  with  the  lower  rate  evolution,  the  w i t h most o f t h e r e p o r t e d  that greater rates  of  of  amounts o f DNA a r e additive  variation  71  production.  Although  circumstantial hypothesized  observed Testing  of  " r a t e of  problem  evidence  for  this  indirectly  favor  i s at present  hypothesis.  relationship, directional  variants could the  i t i s t e s t a b l e , there  Given  only the  s e l e c t i o n f o r phenotypic  s m a l l e r genomes, t h u s  producing  correlation. this  explanation  evolution"  would r e q u i r e the q u a n t i f i c a t i o n  f o r many  groups  i s a k i n t o that of comparing  o n l y be p o s s i b l e t o make e v o l u t i o n , under s p e c i a l l y  relative  of  "niches".  statements  controlled  organisms. It will about  circumstances.  This  probably rates  of  72  CHAPTER F I V E TESTING THE IDEAS  I  have  suggested  (Chapter  Four)  p r o p o r t i o n o f t h e genome c a n be c o n s i d e r e d variation mechanism  production (Chapter  that  a  significant  a g e n e t i c memory  p a t t e r n s , and I have d e s c r i b e d  for  a selection  One) by w h i c h i t c a n be m o d i f i e d .  How d o e s one go a b o u t t e s t i n g a r e g u l a t i o n system  the hypothesized  for variation  production?  e x i s t e n c e of  The  available  o p t i o n s a r e t o seek: 1. g e n e t i c 2.  evidence of t h e system i t s e l f ,  and/or  e v i d e n c e of the a c t i o n of such a system.  E a c h s o r t o f e v i d e n c e c o u l d be s o u g h t i n a " n a t u r a l e x p e r i m e n t " , or a p u r p o s e f u l l y c r e a t e d  experiment. A f t e r b r i e f l y  organisms  a r e most l i k e l y  speculate  on  expected  the  is  outlined,  of  a  are  then d i s c u s s  i n genetic  and  "metavariation  chapter two  I will  patterns  experiments the  structure  the  problems  in  of  some  related  by  generating  ends w i t h a d i s c u s s i o n of t h e r e l e v a n c e  "bandwagon" t o p i c s .  measuring  Throughout t h i s chapter  perspective"  system.  An  evidence of the  v a r i a t i o n . A suggested  outcomes  discussed.  f o r seeking  which  systems, I w i l l  metavariation  s t r u c t u r e i s a requirement  system i t s e l f . expected  t o have m e t a v a r i a t i o n  noting  the  experiment previous I exercise  questions.  The  of the ideas t o  73  Where t o Look O r g a n i s m s most l i k e l y live  t o have a m e t a v a r i a t i o n  system  would  i n an e n v i r o n m e n t 1. w h i c h  changed  over time,  w h i c h c o u l d be  accommodated  necessitating a genetic 2. where  the  by  range than  phenotypic  that  flexibility,  response.  change i n r a t e s and/or d i r e c t i o n  the e n v i r o n m e n t a l make  over a g r e a t e r  of change of  c h a n g e h a s t o be p r e d i c t a b l e "enough" t o  modification  of  variation  production  patterns  worthwhile. The  difficulties  determining perceived to  choosing  "environmental  properly describe  fecundity,  likely  g r a i n " ( i . e . how t h e  production?  Making  distributed  the  r e g u l a t i o n of v a r i a t i o n  to  see  i f there with  DNA  Speculation  could  losses  the  assumption  isa significantly  estimated  last  their  production,  information  on M e t a v a r i a t i o n  the  chapter  I noted a t the outset be  is  interpreted  as  genome s t r u c t u r e . A l t h o u g h ,  (unfit  lower  variants) that  the  among t a x a h a s i t s f u n c t i o n i n  organisms as compared w i t h complex  size.  environment  "enough".  f i n d a way o f r e d u c i n g  differentially  In  o r g a n i s m a r e t h o s e of  i t be more e s s e n t i a l t h a t c o m p l e x o r g a n i s m s , o f  variant  content  a  by t h e o r g a n i s m ) a n d t h e l a c k o f a q u a n t i t a t i v e t h e o r y  Could  in  of  System  i t w o u l d be  interesting  b e t t e r c o r r e l a t i o n o f DNA requirement  for  simpler  ones.  Structure  I considered  known p a t t e r n s  that  differences  rough  indicators  in  i n genome  genome  size  of d i f f e r e n c e s i n  as p r e d i c t e d from t h e  metavariation  74  model,  the  evolution"  patterns  seemed  of a g r o u p , t h e  less variation production prior  expectation  I t w o u l d be  structure  of  a  linking was  system  If  established,  t h e way  that  some  variation  hoc.  speculate  for variation  h y p o t h e t i c a l model s y s t e m c o u l d y i e l d knowledge.  post  such v a r i a t i o n  u s e f u l to  to the  necessary  There  about  exists  no  insight  organized  be  genetic  adjustment. A into  characteristics  i n an  was  the  production  new  with  r e g u l a t i o n might  w o u l d be open t o f a l s i f i c a t i o n  control  " r a t e of  o f g r e a t e r amount of DNA  strictly  a b o u t how  organized.  to vary according  present could  of t h e  be idea  s y s t e m . We  know  that: 1. To m a x i m i z e t h e e f f e c t i v e n e s s of s e c o n d a r y s e l e c t i o n set  of  variation  production  production m o d i f i e r s should that  influence  selection  the  acts.  correlation  In  between  variation production  schemes,  be c l o s e l y  phenotype that  way  genotypes scheme,  the  linked  upon  the  to the  genes  (primary)  'heritability'  the  a  variation  which  created and  on  from  a  beta  or  certain  genes  that  p r o g r a m t h a t scheme, i s as h i g h a s p o s s i b l e . I  intentionally  used a s e x u a l  t h e a c t i o n of s e c o n d a r y panmictic not  sexual  linked,  average  of  then  (Chapter  p o p u l a t i o n , i f b e t a and they  only  selection  populations  two  would  remain  generations  describe  One).  In  alpha  gene were  associated (Leigh  for  1970). In  that  and  the  h y p o t h e t i c a l v a r i a t i o n c o n t r o l genes r e s p o n s i b l e  for  producing  secondary  between  an  there  i t , and  association  a  situation  ef f e c t i v e .  is little  to  selection  phenotype  is  least  75  2. S i n c e e v o l u t i o n a r y required "control  of  r e s p o n s i v e n e s s w i l l not n e c e s s a r i l y  a l ltraits  a t t h e same t i m e , t h e  of v a r i a t i o n f o r d i f f e r e n t t r a i t s  3. T h e r e must be a c e r t a i n amount o f the  genes  involved  s e l e c t e d change, selection effect One  way  and t h o s e g e n e s  (Felsenstein  McGregor  appears  tight  avoid  between  undergoing  under d i f f e r e n t  the  Hill-Robertson  1974).  f o r r e a s o n (1)  ).  i f one m o d i f i e r  w o u l d be t o have  i n t h e genome ( c l o s e l y  But  selection  is  a f f e c t s many l o c i  more  (Karlin  1 9 7 4 ) . So t h e most r e s p o n s i v e v a r i a t i o n r e g u l a t i o n  s y s t e m w o u l d have o n l y It  the t r a i t s  of t r a i t s  c o n t r o l l i n g each l o c u s  e f f e c t i v e on m o d i f i e r s and  i s advantageous.  t o have i n d e p e n d e n t c o n t r o l o f t r a i t s  to the locus  independent  recombination  producing  regimes, i n order to  separate modifiers linked  in  be  that  linkage  one m o d i f i e r  the  f o r each  ways t o s a t i s f y  independent  the dual  t o e a c h l o c u s , and one m o d i f i e r  trait.  r e q u i r e m e n t s of  for several  loci,  f o r a t r a i t , and t h e m o d i f i e r ,  i n one  are: 1. c o m b i n e linkage  a l l loci group  2. have a r e g u l a t o r - c o n t r o l l e r s y s t e m i s o m o r p h i c t o t h e gene regulation for The  s y s t e m p r o p o s e d by B r i t t e n and D a v i d s o n  gene r e g u l a t i o n .  pleiotropic  traits  makes  relationship  solution  regulator-controller  (1)  system  that  can e x i s t between  less  effective  (2),  one  or  ( ' r e c e p t o r s ' ) w o u l d be l i n k e d t o e a c h p r i m a r y would loci  (1969)  receive  signals  (the modifier  genes)  than  more  (2).  example,  locus,  allow  and  In  a  'controllers'  from p a r t i c u l a r monomorphic to, for  genes  and  they  'regulator* or  disallow  76  error-checking The  by  a c e r t a i n enzyme.  fact that  regulation coincide  the  s y s t e m and is  the  important  interpretations  to the  confidence  in  the  McClintock  (1965)  for  mutation  (1979),  in  have  has  may  And  predictability  and  the  their  the  of t h e  change. I t should s l o w e d by  may  increase  variation  system  is  latter  being  rate  of  a  of  variation  to  in previous  change  involved  bulk  Nagl and  of DNA  chapter),  the  of  most  by  the  environmental  r e s p o n s i v e n e s s would r a t e s between and  in  the  loci  decrease  different  be  of  traits,  effect. highly  one  significant  always determined  recombination  less  system than the  changes i n the  system.  including  not  'controllers',  regulation  a  regulation  v a r i a t i o n production  be a p p a r e n t t h a t  require  two d i f f e r e n t  processes.  to produce the H i l l - R o b e r t s o n It  system  I t might a f f e c t  authors,  that  r e c o m b i n a t i o n between l o c i  2.  regulation  are:  responsive one,  i d e a l gene  a r e g u l a t o r - c o n t r o l l e r system  several  related  the  i t gives  gene  described  suspicion  be  appropriate  since  hypothesized  voiced  most  variation  same s t r u c t u r a l e v i d e n c e .  important points  1. The  ideal  in i t s e l f ,  maize.  differentiation Two  s t r u c t u r a l p r e d i c t i o n s of  formalized  just suggested extent.  present  to  pattern  Gene d u p l i c a t i o n , o r  (see  f o r e x a m p l e , may  variation  other be  influences  enough.  77  Epigenesis So  and  far  Canalization I  simplification process been It  have of  i.s  the  epistatic,  making  ignoring  of e p i g e n e s i s  discussing,  been  and  lies  the  the  standard  process  the phenotype  (and  of  genes  pleiotropic),  an  epigenetic  "additivity"  variation).  traits  (one-to-one,  and  of g e n e t i c  mutation I  consideration,  and  the  variation.  a  genetic  I  t o note the g r e a t  variation  and  t h e phenomenon of  production  so t h a t t h e  patterns  from a m e t a v a r i a t i o n  " d e e p e n i n g " of a d e v e l o p m e n t a l  same norm i s p r o d u c e d d e s p i t e c o n s i d e r a b l e  in  sensitivity  (Waddington  phenotypic of  system, the  v a r i a t i o n per  trait,  the phenotypic a  se, but  level  this  to  selection pressure  been  continues  observed  in  to  the  decreasing  variation  in  the  implies less variation  c h a n g e t h a t c o u l d be m i m i c k e d by  "...has  variation  t o the  on m e t a v a r i a t i o n . M o d i f i e r f r e q u e n c i e s  Canalization  response  1957,1975). I t r e f e r s , not  t h e d e v e l o p m e n t a l pathway  e n v i r o n m e n t . At  selection  expected  of the c h a n g i n g  " c a n a l i z a t i o n " c a u s a l l y a t t r i b u t e d to  i s the  environment  the  similarity  i n the context  system.  Canalization  in  between  o r g a n i z a t i o n t h a t e a c h r e q u i r e . Now  would l i k e  decrease  relatedness  the  of  in the  possible  of  similarity  epigenetic  > PHENOTYPE  variation production  of  that  epigenesis  mentioned  differentiation  The  phenotypic  > GENOTYPE  Earlier  epigenesis.  between t h e g e n e t i c m e c h a n i s m s I h a v e  relationships  determine the  of  Neo-Darwinian  stabilizing  change  situations  f o r many g e n e r a t i o n s . "  slowly. in  which  (Waddington  78  1974)  Stable  environments  canalization, selection and  favor  references  epigenetic for  whereas  and  changing  therein).  focussing variation  and  favor  disruptive  ( W a d d i n g t o n a n d R o b e r t s o n 1966,  Waddington  rather  selection  environments  i t s breakdown  system,  stabilizing  gives  credit  than t o a category  to  of (beta)  the genes,  production.  On M e a s u r i n q G e n e t i c Var i a t i o n P r o d u c t i o n One  prediction  metavariation adaptively "niche  patterned  variation  to  suit  hypothesis"  In  Genetic  percent  either  a  i n populations  be  environment.  (This i s the  about g e n e t i c v a r i a t i o n . )  case  variation  such p a t t e r n s would metavariation  clear  "non-additive"  a  not  system.  genetic that  under  loci  ( P ) . These to  populations  imply  Stronger  production  v i a phenotype)  additive  convenient  the categories  v a r i a t i o n . Levins  different  environment constant additive  isa  i n v o l v e s t h e measurement o f  measured  (1964a)  and n o n - a d d i t i v e  functions in adaptation,  selection  This  terms of average h e t e r o z y g o s i t y  relationship  explanation  test  (generally  in  of polymorphic  different  of  production.  quantified  no  existence  variation  the  because f i n d i n g  genetic variation  usually  assumed  w o u l d be i n t e r m s o f c h a n g e s i n v a r i a t i o n  patterns.  his  the  e x i s t e n c e of the hypothesized  predictions  bear  on  system i s that g e n e t i c  weak p r e d i c t i o n , the  based  and a r e  (H) a n d  statistics  "additive" was  clear  variation  favored  by  in have  natural an  i n time would not favor the maintenance  of  to perceive  But  that  same  For  and  example,  variation.  circumstances.  is  stability  could  the environment as s p a t i a l l y  enable  patchy,  a  79  situation  f a v o r i n g the maintenance  of n o n - a d d i t i v e  variation in  the p o p u l a t i o n . A l l p r e d i c t i o n s of t h e m e t a v a r i a t i o n in  terms  of  additive  variation  only.  model  Any p a t t e r n  g e n e t i c v a r i a t i o n m e a s u r e d by H a n d P w i t h some o t h e r potentially  influenced  by  differing  amounts  are  comparing factor  is  of n o n - a d d i t i v e  var i a t i o n . The  r e s t of the problem  product ion.  Variation  f a c t o r s such  as  i s in  to  i n a population  population last  size,  estimate  variation  i s i n f l u e n c e d by s e v e r a l  population  bottlenecking).  structure,  (time  variation  be i n t e r p r e t e d a s p r e - s e l e c t i o n , o r p o s t - s e l e c t i o n ? I s i n d i c a t i v e of low v a r i a t i o n  And,  and  history  low v a r i a t i o n  since  how  should  production,  the  or  high  s e l e c t ion? Perhaps relevant  the  to  best  these  measurements  way  to  measure t h e a d d i t i v e v a r i a t i o n  hypotheses  would  be  of e v o l u t i o n a r y responsiveness.  done t h r o u g h s e l e c t i o n  indirectly  via  T h i s would best  be  e x p e r i m e n t s u s i n g t h e methods o f a n a l y s i s  of q u a n t i t a t i v e g e n e t i c s .  Suggested  Experiment  Ayala compared with  (1966,1967,1969) performed e x p e r i m e n t s the  that  of  densities pressure. and  in  evolutionary unexposed h i s cages  Adaptation  productivity.  populations  response flies.  was a s s e s s e d After  an  of i r r a d i a t e d  The  provided  in  the  increasing directional  i n terms of  initial  delay,  which  fruit  selection size,  irradiated  i n c r e a s e d i n f i t n e s s a n d became b e t t e r a d a p t e d  the c o n t r o l s .  flies  population  population the  he  than  80  I  propose  selection,  a  similar  i n s t e a d of  increased  selection population,  production.  system  will  exists.  cause  and  of  populations  The  latter  by  will  hypothesis  comparing t h e i r  environment.  stimulate  variation  be  selection  i n a way  that  is  that  decrease  cause i t to  confer  a  in a  increase. groups  responsiveness.  to maintain  is  trigger  c o m p a r e d i n two  one  stored v a r i a t i o n . This  to  stabilizing  productivity  experimental  in  d o e s not  to  evolutionary  The  production  that  production  will  directional  used  implies  be m e a s u r e d as a b i l i t y  changing  appropriate  This  which  is  directional selection will  r a t e of v a r i a t i o n p r o d u c t i o n  a  The  variation  The  in  in  ionizing radiation,  variation  metavariation  experiment  trick  is  to  group  by  directional  i t with  an  advantage i n  to  be  accomplished  as  follows: 1. C h o o s e a v a r i a b l e t h a t can produce  directional  d i r e c t i o n s , and such  as  cutoff  S t a r t two  temperature  should  i m p o r t a n c e of d r i f t , capacity  of  us c a l l  possible  to  two  (opposite)  selection.  that  permits  range,  is  to  A  variable  catastrophic  superior  to  a  tolerance.  be yet  in  manipulated  from the  large small  same s t o c k .  enough  to  minimize  relative  to  the  Each the  carrying  i t s container. the  " r e l a t i v e zero".  has  time,  g r o u p s of p o p u l a t i o n s  population  3. L e t  stabilizing  developmental  like  conveniently  selection  beyond a p r e d e t e r m i n e d  variable 2.  strong  be  s t a r t i n g value Relative  zero  the c o n d i t i o n s  been m a i n t a i n e d  of  the  should  selection variable be  under w h i c h the  for a long  time,  so  that  as  close  founder  as stock  "stabilizing"  81  selection  around  directional  relative  selection.  selection at relative 4. S u b j e c t  group  B  quantitative  theory  intensity  of  will  the  the next  back  specify  lack  the  selection  is  again  to  to  be  the of  a  duration  and  required  to  alleles. loci  on a l l e l e s  directionally i n the negative  relative  zero.  t o " t u r n on" v a r i a t i o n  This  production  i n the population appropriate  environmental  selection  generations.  in  for  response.  important  directional  For  that undetermined extent  storing alleles  The  selection  t h e speed of s e l e c t i o n  intended  genetic  to  to s t a b i l i z i n g  speeds of s e l e c t i o n a t m o d i f i e r  than  d i r e c t i o n , and then  without  cannot  phenotype.) Group B  is  amount  change t h e f r e q u e n c i e s of m o d i f i e r  to half  treatment  A  (arbitrary).  I  be much s l o w e r  selected  not  group  directional  directional  that  determining  Subject  to  direction  (Remember  does  zero.  "negative"  significantly  zero  The  change  for  i s between g e n e r a t i o n s , classical  producing  not  experiments  within  testing  the  e f f e c t i v e n e s s of h e t e r o g e n e o u s e n v i r o n m e n t s i n m a i n t a i n i n g polymorphisms  (Powell  within-generation be  expected  to  1 9 7 1 ; A y a l a and M c D o n a l d  temporal favor  heterogeneity,  the  maintenance  1974)  used  which would not of  addi t ive  var i a t i o n . 5. The  productivity  the  same t i m e s , o v e r  o f g r o u p s A and B i s t o be m e a s u r e d a t regular intervals.  be m e a s u r e d i n t e r m s o f t h e " s u r p l u s " size  "quota".  The q u o t a  Productivity i sto over  a  population  i s s e t l a r g e enough t o a v o i d t h e  82  i n f l u e n c e of g e n e t i c this  quota  selection  at  each  variable,  directional  drift.  census. which  selection,  adult population  the  The  is  to  directional "positive"  the  reset  to  intensity  be c o n t r o l l e d  of  so t h a t t h e  below t h e q u o t a .  to conditions  selection  are  r a t e of change of t h e  determines  s i z e never f a l l s  6. As g r o u p B i s r e t u r n e d begin  The p o p u l a t i o n s  at  relative  zero,  of both g r o u p s , t o g e t h e r , i n  direction.  Monitor  their  relative  i s that group A w i l l  initially  be more  responsive  product i v i ti e s . My  prediction  to the s e l e c t i o n  because i t s s t o r e d v a r i a t i o n  g r e a t e r , a n d more a p p r o p r i a t e G r o u p B, i f i t d i d i n d e e d this  time,  latter's  should  gain  A possible criticism  directional production. variation  group  sizable little  A,  itself  r a t e by  merits  of  stabilizing  potentially  phenotypic  variation.  stored  useful  than  variation  versus  produced  Slow  variation  large populations  genetic  rather  f o r changing  consideration.  were moderated  s t o r e of  i s that the a l t e r e d  (e.g. temperature),  may be r e s p o n s i b l e  important  under  be  "positive".  at a greater  of t h i s experiment  might r e q u i r e that very  production  to  i s depleted.  relative an  to conditions s l i g h t l y  produce v a r i a t i o n  to obtain appreciable  variation then  The are  production order  parameter  selection,  likely  and s u r p a s s group A i n adaptedness as t h e  stored variation  environmental  is  be u s e d  in  r e s p o n s e . And i f p h e n o t y p i c at  the  epigenetic  selection, alleles  level,  could maintain while  a  producing  83  Previous  Experiments  Several  experiments  competitive a b i l i t y production.  have  1974;  Chao  and  diploid  s t r a i n s of t h e y e a s t 1983).  were a s e x u a l , adaptation  and  a  new  to  be  reason  fixation  faster  rate  of  of  The  higher  y e a s t was  same p e r - l o c u s therefore and Cox genes  mutation  twice  diploid rate  the o v e r a l l  (1983) c o n c l u d e d t h a t are  rarely  the  as  variation  new  had  a  m u t a t i o n r a t e of t h e h a p l o i d .  Chao  is surprising  that  mutator  found i n n a t u r e . " E v o l u t i o n d i d not s t o p over  never  I  would  i f i t c o u l d be p r o d u c e d of the  are  by  and  reached.  These  superior  haploid,  "...it  isogenic  peak",  the advantage  the  assumed t o have the  e x p e r i m e n t -- an e q u i l i b r i u m ,  selection,  of  and  E. c o l i  the c o u r s e of t h e i r was  strains  advantageous  mutator  the  and  problem  competitively  m u t a t i o n s -- t h e y e v o l v e d f a s t e r . m u t a t i o n . r a t e . The  and  (Paquin  e n v i r o n m e n t . The m u t a t o r E. c o l i be  a  Cox  cerevisiae  facing  d i p l o i d S. c e r e v i s i a e p r o v e d t o of  1970;  wild-  i s o g e n i c haploi.d  Saccharomyces  considered  the  variation  m u t a t o r and  (Gibson et a l .  1983),  of  In both of t h e s e c a s e s the competing  and  to  Cox  comparing  in rates  T h e s e have c o m p a r e d , f o r e x a m p l e ,  Gibson  Adams  done  of s t r a i n s d i f f e r i n g  type s t r a i n s of E s c h e r i c h i a c o l i  and  been  expect  in their  or  that  "adaptive stabilizing  s y s t e m , w o u l d be  to  non-mutator.  comparisons  of  the  suitability  schemes t o a g i v e n e n v i r o n m e n t ,  the e x i s t e n c e of m e t a v a r i a t i o n ,  rather  i . e . the a b i l i t y  c h a n g e i t s v a r i a t i o n p r o d u c t i o n scheme.  of  different  than a t e s t f o r of a s t r a i n  to  84  in  M e t a v a r i a t i o n as E x p l a n a t i o n SEX.  Sex  f l o w , and  consequently  regulated.  (See  adaptability value  of  opens  than  that, the  flow.)  See  More  variation  for for  variation  a  I  using  very  flexible  think  cues,  fluctuations.  than  of  (1964) on just  is  reproductive  to  system f o r producing  caught  strains  strains  associated  germ  mutability,  frequent  recombination  to  phenomenon,  a  of  response  to  response  process by  sex  individual)  s i g n i f i c a n c e of of  which  is gene  genetic  variation  rates,  ranging to  the  I p r e f e r t o v i e w sex a s  i s very one males  line  is  of  a  metavariation,  interesting: of t h e from  two  reciprocal  recently  characterized  dysfunctions  chromosomal absent  e a r l y e m b r y o n i c d e v e l o p m e n t , and extinction  important  wild-  w i t h females from l o n g - e s t a b l i s h e d It  (normally  the  metavariation.  in  usually  ...  kind  standpoint  arises  crossed  laboratory  is  dispersal  t h e phenomenon o f h y b r i d d y s g e n e s i s  male-female c r o s s e s ,  on  r e g u l a t e d i n many ways,  isolation.  dysgenesis  of  literature  it  mechanism  be a d j u s t e d and  cost  c o n c e p t and  the a d a p t i v e  a  be  damping g e n e t i c  recombination,  sex  can  (between  (This  HYBRID DYSGENESIS. From t h e  "Hybrid  The  spatial  f r o m a s s o r t a t i v e n e s s of m a t i n g s , extreme  1.)  production,  between-individual  temporal  Levins  can  genetic  being  production,  production  of d i f f e r e n t ways i n w h i c h gene  been d i s c u s s e d more i n t h e  short-term  wasteful.  Topics  a myriad  anywhere e l s e .  way  Bandwagon  f a c t o r s i n Table  in  heterogeneity local,  the  have  sex  realize  permits  Two  i n b o t h m a l e s and  by  various  including  high  rearrangements,  male  in Drosophila), failure sterility  females...  The  due  t o germ  only puzzle  of  line is  85  the  ostensible normality  Doolittle So  f a r two  underly  i n t e r a c t i o n systems  transposable  dysgenesis, P  and  I  d i s t r i b u t i o n s of  P and  laboratory  is  age  a c t i v e P and  1. The  (P-M  elements  1981)  loss  I  "recent  suggests  Again, c o n s t a n c y , or  and  that  record there  is  original a  a  (Bucheton et  than  uncontrolled,  are  1976;  r e s u l t from  isolates,  mainly  (Kidwell  hypothesis  1979,1982)  Old  laboratory  populations. dealing  with  than the p a r t i c u l a r P and  I elements are  l e s s b e n e f i c i a l i n the  are  in  I  a p e r h a p s more  the  state, related constant  temporally  environment.  perspective,  runaway  to have  al.  M populations  s t a t e of w i l d  missing  they  like  advanced  r e c e n t l y been a r a p i d s p r e a d of  has  lab  the  of  there  and  of  presence  hypothesis"  l a b e n v i r o n m e n t . Maybe t h e  From my  trends:  invasion  the  heterogeneous n a t u r a l  The  conditions.  r a t e of c h a n g e , r a t h e r  environment  1983).  1983):  P factors in small  to v a r i a t i o n production  normality  Kidwell  to  involve  of D r o s o p h i l a  P f a c t o r s through n a t u r a l populations.  strains  the  and  the  been  populations  (Bregliano  to  temporal  with  h y p o t h e s e s have  those kept under l a b o r a t o r y 2. The  and  have been f o u n d  Doolittle  correlated  s u g g e s t s t h a t R and of  I-R)  (Rose and  "stochastic loss hypothesis"  the  of  and  I s t r a i n s show s t r i k i n g  laboratory  I elements  Engels  and  s o m a t i c t i s s u e . " (Rose  t h e y have been shown  inversely  older  f e w e r P and  and  I e l e m e n t s . Two  why  the  1983)  hybrid  explain  of  soma, t h e  particularly  the  "puzzling"  phenomenon of h y b r i d d y s g e n e s i s  variation  variation  given  is  production produced  system in  — the  looks  t o o much, o r germ  line  86  (offspring).  Notice  that, like  sex, i t i s a  between-individual  phenomenon, a n d c o u l d t h e r e f o r e be p l a y i n g a f u n c t i o n spatial  heterogeneity  variation Kidwell and the of  useful (1983)  in  as  temporal  note t h a t data  a p p e a r a n c e o f s t r o n g new  correspond  The with  dates  responsiveness.  "... r o u g h l y  appearance  intensive  place to start  use  of  of  DDT,  I and  variation  t o emphasize h y b r i d dysgenesis  looking  production.  for  a  and  on t h e t i m i n g o f a p p e a r a n c e o f I  selective pressures  of  Bregliano  coincides  system  involved  with  in populations and  P  first  o r g a n o p h o s p h a t e s , r e s p e c t i v e l y ( B r e g l i a n o and K i d w e l l I would l i k e  using  a means o f p r e d i c t i n g a n d r e g u l a t i n g  P factors in wild populations  insects".  in  use  of  1983).  a s an in  strains  important  regulating  87  DISCUSSION  "There  has  grown up, w i t h i n t h e N e o - D a r w i n i s t p a r a d i g m o f  evolutionary  theory,  a dogma t h a t  elements  that  materials  for evolution  nature  of  the  subjected...This but  deeply  may a p p e a r  i n a population  are  selection  the character  quite  process  to  ( C H . Waddington  new  a s p o t e n t i a l raw  unconnected  seems t o be n o t o n l y  felt..."  o f any  with  the  which they w i l l  tenaciously  be  believed,  1974).  P o p u l a t i o n - l e v e l Genet i c Memory Waddington and h i s f o l l o w e r s have s t r e s s e d of  the  "epigenetic  system",  a  the production  the  phenomenological  adaptively  focussing  epigenetic  system i s presumably the r e s u l t  importance model,  in  o f p h e n o t y p i c v a r i a t i o n . The of a l o n g  period  of  evolut ion. In  the  course  of  this  phenomenological model, d e r i v e d but  rather  a  mechanism  that  a p p r o x i m a t i o n t o an e p i g e n e t i c conceptual mutually  division  of  the  thesis  I  have  from e x p e r i m e n t a l might  be  system. genome  described  observations,  considered  It  is  not a  a  premised  first on  a  i n t o two, n o t n e c e s s a r i l y  e x c l u s i v e , s e t s of genes ( L a y z e r  1980):  88  1. t h o s e  (alpha genes)  which  govern  maintenance of t h e i n d i v i d u a l 2.  Cf/eta  those i.e.  To  genes)  use L e v i n s '  govern g e n e t i c  end  analogy,  favored  i n d e v e l o p m e n t a l programs, and t h e  selection  has  memory  of  memory  what  alpha  favored  my  stores  i n genotypic  E a c h memory' h a s a c h a r a c t e r i s t i c  adaptability,  l a g time  Chapter  beta  memory  variation due  to  the  last  influenced  Unless  the l a s t  generation  environment  of  generation,  i t would  genetically,  i . e . t o u p d a t e a l p h a "memory,.at  The  not  have  same r a t i o n a l e h o l d s  i s much l o n g e r selection)  been  f o r beta  in  alpha  that  evolutionary  patterns  changes a r e n e c e s s a r i l y  of  longer  present  all.  memory, o n l y  adaptedness,  time  i t s l a g time  (by  d e t e r m i n e d by t h e way a  generation. the  memory. B e c a u s e  ( b e t a memory) c h a n g e s more s l o w l y t h a n  i t  an a d v a n t a g e t o r e s p o n d  b e c a u s e i t i s more s l o w l y c h a n g e d  v i a changes  time  memory" i s  the past  was a good p r e d i c t o r o f  stores  production.  t o f i x new i n f o r m a t i o n . F o r e x a m p l e , t h e " a l p h a the  Three)  what s e l e c t i o n h a s  takes  by  and  production.  (1968, and see  the  development  o r g a n i s m , and  which  genetic v a r i a t i o n  the  scale  secondary  adaptability this  means  adaptability than  those  p a t t e r n s b a s e d on c h a n g e s i n a d a p t e d n e s s . It  is  interesting  to realize  that the beta  f a v o r a b l e p a t t e r n s of g e n e t i c v a r i a t i o n population-level  memory.  ingenious  of  model  Edstrom  production,  (1975)  the,  frequencies  second  has  storing  are really a  described  an  e v o l u t i o n i n which he, t o o , p o s t u l a t e s t h e  e x i s t e n c e o f a p o p u l a t i o n - l e v e l memory i n model  genes,  genetic  memory  i n the population, obtained  the  is a by a  genome.  sample  of  censusing  In h i s allele process  89  made  possible  by  sexual  reproduction  memory i s u s e d i n a  different  segregation  are  ratios  way:  through  distorted  T h i s would cause r a r e a l l e l e s  and  much  lower  s e l e c t i o n . Edstrom generations,  at  i n c r e a s e the  cost,  a  positive  A segregation  r a t i o of  produce  same  Variation  Layzer,  of v a r i a t i o n there  d i s c u s s the  idea  discussion  about  made  them  selection  adaptability  al.  in only  it  of  233  production  in  would  the  clear.  0.1. could  without  the  Patterns such as L e v i n s  be  a I  r e l u c t a n c e to have  (1981)  yet  to  ideas,  criticized  made no comment on  and  system subject  adjustable variation  Templeton  to  to  recessive  a s an a d a p t i v e to  o f 0.01,  f r o m 0.01  the  9240  selection.  literature.  Layzer's  take  generations,  natural  seems  faster,  to  openly see  a  although Layzer's  the c e n t r a l d r i v e of  (1980) p a p e r .  Although  optimal  favor  rare  be p o s s i b l e by n a t u r a l  r e c o g n i t i o n , . b y people  m e c h a n i s m and  Layzer's  in  Evolut ionary  still  f a v o r of  selection coefficient  r e q u i r e d by  explicit  selection,  he  1.01  P r o d u c t i o n and  Despite  would  of a r e c e s s i v e m u t a t i o n  result  r e p r o d u c t i v e excess  in  This  conversion,  t o i n c r e a s e much  (1975) c a l c u l a t e s t h a t  frequency  the  than  1975).  gene  slightly  alleles. at  (see E d s t r o m  considerable and  foraging  1983;  importance received Waddington  attention  a d j u s t m e n t of v a r i a t i o n literature  Crandall  and  (Kaplan  Stearns  1957;  attention Ho  and  only  by  Saunders  now  i n the  and  1982;  o f p a t t e r n s of v a r i a t i o n direct  is  being life  Cooper Caraco  production the 1979).  paid  to  history  and  1984;  Lacey  1980),  in evolution  epigeneticists But  processes  et the has  (eg. of  90  variation  production  for  potential  their The  'effect  explanation tendencies be  This  is  species to  'effects'  than  notion  of  secondary  selection,  individual  have  that  incidental  group.  1975,1979). A l t h o u g h  'individual'  adaptive  I  of d i r e c t  is  emphatic  level,  and  on v a r i a t i o n  l o s s , eg. the  allowing  does not  include  s y s t e m . My  point i s  s y s t e m m i g h t e x i s t . On i s a f o r m of g r o u p  upward c a u s a t i o n by  "molecular  selection  action  drive"  and  the  other  selection,  selection  on  unusual  in  is  moving to  chromosomes  drift.  of a s e t of p r o c e s s e s  t r a n s p o s i t i o n , and  of  intrachromosomally,  in  refers  p a t t e r n s b a s e d on v a r i a t i o n p r o d u c t i o n  to  capable  Vrba  and  advocate.  ( 1 9 8 2 ) c o n c e p t of  refers  she  species selection  suggests  nonhomologous  adaptation.  e f f e c t s might i n f l u e n c e net s p e c i a t i o n  selection,  unequal c r o s s i n g over, are  s e l e c t i o n may  may  within  a  a process  i n d i v i d u a l s , as  drive"  processes and  t h a t s u c h an  rather  than  and  of a more i n c l u s i v e a d a p t i v e  Stanley's  it  characters  trends  selection  o n l y at the  hand,  that  directional  1983).. I t s t a t e s t h a t  (see S t a n l e y  order  Dover's  long-term  one  i s i n t e r m e d i a t e between t h e e f f e c t h y p o t h e s i s  the p o s s i b i l i t y precisely  are  is  of  on  selection  adaptation  (1980,1983)  result  i n a monophyletic  second  Vrba  which  of  that these  stance  of  evolutionary patterns.  the  d r i v e n by  and  (R) My  'trends',  based  t o come u n d e r g r e a t e r s c r u t i n y  in determining  i n e v o l u t i o n (Vrba  adaptations  rate  role  r a t h e r than  effects,  starting  hypothesis'  for  unselected  species,  are  a  homologous (Lewin  "Molecular including  gene c o n v e r s i o n ,  variant  repeat  chromosomes,  rather  that  sequence and  1982). In a p a n m i c t i c  to sexual  91  population this diffusion is  faster  than  •repeats. This  the  o f a v a r i a n t t h r o u g h o u t t h e gene  fixation  implies that  of a v a r i a n t w i t h i n a f a m i l y of  "there  i s i n each i n d i v i d u a l  a v e r a g e r a t i o o f o l d and new v a r i a n t s f o r a (Dover  1982),  and  that  i n d i v i d u a l s because they an  It  selection w i l l  family i s mostly  particular  that v a r i a t i o n  t h e p o i n t where t h e v i a b i l i t y  seems  to  This  divergence  of " a c c i d e n t a l  of s u b p o p u l a t i o n s  on  a  to  o f h y b r i d s m i g h t be a f f e c t e d .  d r i v e i s independent of s e l e c t i o n and d r i f t ,  operate  is  between s p e c i e s , and n o t w i t h i n s p e c i e s .  due-to the cohesive  Molecular  family"  i n members o f a  a l s o l e d D o v e r t o s p e c u l a t e on t h e p o s s i b i l i t y  speciation"  t h e same  n o t d i s c r i m i n a t e among  a r e a l l more o r l e s s s i m i l a r .  e x p l a n a t i o n of the o b s e r v a t i o n  repeat  pool  longer  time  scale  than  and  those  two  processes.  Old  Ideas The  recent  conceptual  division  i d e a . Dobzhansky  "Lamprecht Lamprecht  varieties.  Bocher  mutations,  in  a  series  distinguishing  some  of  papers  beta  genes  continues, Perhaps these  species  responsible  a  (summary  and  and  others  f o r adaptation  in  only kinds  t o the  for progressive evolution."  Bocher's dichotomy, i n p a r t i c u l a r ,  present."  i s not  (1951) b e l i e v e d t h a t t h e r e a r e two  environment and o t h e r s  Dobzhansky  genes  1964) t h a t t h e r e a r e two c a t e g o r i e s o f g e n e s some  of a l p h a and  of  (1970) w r i t e s  argued  mutations,  of  between t y p e s  i s remarkably  (Layzer  "These  1980),  which  similar I  to that  described.  v i e w s have v e r y . f e w a d h e r e n t s  ideas should  be r e c o n s i d e r e d !  at  92  SUMMARY  1. U n d i r e c t e d connection variants  variation  production  with  selection  will  the be  subjected,  by  definition  forces  and  has  no  t o w h i c h t h e new  usually  lowers  the  immediate f i t n e s s of p a r e n t s . 2. G e n e t i c  adaptability  immediate f i t n e s s production  of  genetic  variants,  for  maintaining  and i t r e q u i r e s t h e so  there  is  an  t y " tradeof f.  adaptedness/adaptabi1ity  a. e n v i r o n m e n t a l and  important  i n a changing world,  "adaptedness/adaptabi1i 3. The b e s t  is  parameters,  c o m p r o m i s e d e p e n d s on i n c l u d i n g r a t e s of change  p r e d i c t a b i l i t y , and  b. t h e t i m e s c a l e o v e r w h i c h t h e c o m p r o m i s e s t r a t e g y observed.  A long  investment  in adaptability.  4. G i v e n  the  existence,  "variation (i.e.  time s c a l e of o b s e r v a t i o n  in  in  processes variation  genetic  in  these  Secondary s e l e c t i o n , modifiers.  Thus  to  is  production.  patterns" genetic  production.  production  can  of  Random  act  on  these  a t t h e l e v e l of the  undirected,  modification  modify  metavariation.  or  random.  r a i s e d o f w h e t h e r genomes m i g h t be  facilitate  heritable  tailor  produces  particular,  variation  of  e l e m e n t s a r e known t h a t  elements  genotype i s not n e c e s s a r i l y question  can  variation  in  f a v o r s more  production  selection  Many g e n e t i c  of  population,  variation  "metavariation"),  adaptability.  a  is  genetic  The  organized variation  93  5. We  can  expect  patterns  in  traditionally (e.g. on  evolutionary  variation  production,  emphasized  basis  of  to  as  patterns  s e l e c t i o n and d r i f t ) .  the  patterns  well in  Hypotheses can  adaptability  and  be c a u s e d by as  the  variant  loss  be  formulated  change,  as w e l l as  a d a p t e d n e s s and s t a t e of t h e e n v i r o n m e n t . 6. The m e c h a n i s m o f s e c o n d a r y s e l e c t i o n , a n d t h e n o t i o n a p a r t o f t h e genome i s  involved  variation  production,  are  explanation  f o r the observed patterns  7. S e l e c t i o n c h a n g e s a l l e l e much  more  slowly  adaptability  occur  adaptedness.  Slow  evolutionary special  than  at  processes,  contingencies.  used  to  frequencies  more  patterns  in  better  regulating build i n genome at  primary  loci.  slowly  than  might than  a  genetic possible  size.  modifier  loci  So c h a n g e s i n changes  e x p l a i n , long fast  that  processes  in term and  93a  Patterned  production  of g e n e t i c  variation:  consider i t , "...the  main  l a c k of a f u l l y canditure  w e a k n e s s o f modern worked out t h e o r y  evolutionary theory of v a r i a t i o n ,  that  is its is,  of  for evolution..." (Medawar  1967)  or d i s m i s s i t . "Mutations...arise usefulness. that  I t may  mutability  regardless  seem a d e p l o r a b l e is  not r e s t r i c t e d  the a d a p t e d n e s s of t h e i r Pangloss  could  of t h e i r  carriers.  a c t u a l or p o t e n t i a l  i m p e r f e c t i o n of  nature  t o changes t h a t  enhance  However,  only a  i m a g i n e t h a t t h e g e n e s know how  vitalist  a n d when i t  i s good f o r them t o m u t a t e . " (Dobzhansky  1970)  94  REFERENCES CITED  A b r a h a m s o n , L., M.A. B e n d e r , A.D. C o n g e r and S. W o l f f . 1973. U n i f o r m i t y of r a d i a t i o n - i n d u c e d m u t a t i o n r a t e s among d i f f e r e n t s p e c i e s . N a t u r e 245:460-462. A u e r b a c h , C. 1956. G e n e t i c s of t h e a t o m i c a g e . O l i v e r and B o y d , Edinburgh. A v d u l o v , N.P. 1931. K a r y o - s y s t e m a t i s c h e U n t e r s u c h u n g e n d e r F a m i l i e Gramineen. B u l l . A p p l . B o t . G e n e t . P l a n t Breed. 44(Suppl.):1-428. A y a l a , F . J . 1968. B i o l o g y a s an autonomous S c i e n t i s t 56:207-221. Bachmann,K. 1972. Genome s i z e  s c i e n c e . American  i n mammals. Chromosoma  Bachmann,K., B.A. H a r r i n g t o n , and J . P . C r a i g . i n b i r d s . Chromosoma 37:405-416.  37:85-93.  1972. Genome s i z e  B a e t c k e , K . P . , A.H. S p a r r o w , C.H.Nauman, and S.S. Schwemmer. 1967. The r e l a t i o n s h i p o f DNA c o n t e n t t o n u c l e a r and chromosomal, volume and t o r a d i o s e n s i t i v i t y (LD50). P r o c . N a t l . A c a d . S c i . USA 5 8 : 5 3 3 - 5 4 0 . B a t e s o n , G r e g o r y . 1963. The r o l e o f s o m a t i c c h a n g e i n e v o l u t i o n . E v o l u t i o n 17:529-539 B e n n e t t , M . D . 1971. The d u r a t i o n o f m e i o s i s . P r o c . R . S o c . ( L o n d . ) B 178:277-299 B e n n e t t , M . D . 1972. N u c l e a r DNA c o n t e n t and minimum g e n e r a t i o n t i m e i n h e r b a c e o u s p l a n t s . P r o c . R . S o c . ( L o n d . ) B 181:1091 35 B e n n e t t , M.D. 1973. N u c l e a r c h a r a c t e r s S y m p . B i o l . 25:344-366.  i n p l a n t s . Brookhaven  B e n n e t t , M . D . And J . B . S m i t h . 1972. The e f f e c t s o f p o l y p l o i d y on m e i o t i c d u r a t i o n and p o l l e n development i n c e r e a l a n t h e r s . P r o c . R . S o c . ( L o n d . ) B 181:81-107 B e n n e t t , M . D . And J . B . S m i t h . 1976. N u c l e a r DNA amounts i n a n g i o s p e r m s . P h i l . T r a n s . R . S o c . B 274:227-274 B i e r , V . K . And W. M u l l e r . 1969. DNA-Messungen b e i I n s t e k t e n und. e i n e H y p o t h e s e u b e r r e t a r d i e r t e E v o l u t i o n und b e s o n d e r e n D N S - R e i c h t u m im T i e r r e i c h . B i o l . Z e n t r a l b l . 88:425-449.  95  Bishop,J.O.  1974. The gene numbers game. C e l l  2:81-86  B o c h e r , T.W. 1951. S t u d i e s on m o r p h o l o g i c a l p r o g r e s s i o n and e v o l u t i o n i n the v e g e t a b l e kingdom. Dan.Biol.Medd. 18(13):1-51 . Bowen, H.J.M. 1962. R a d i o s e n s i t i v i t y o f h i g h e r p l a n t s and c o r r e l a t i o n s w i t h c e l l w e i g h t and DNA c o n t e n t . R a d i a t . B o t . 1 :223-228. B r i t t e n , R . J . And E . H . D a v i d s o n . 1969. Gene r e g u l a t i o n f o r h i g h e r c e l l s : a theory. Science 165:349-357 B r i t t e n , R . J . And E . H . D a v i d s o n . 1971. R e p e t i t i v e and nonr e p e t i t i v e DNA s e q u e n c e s a n d a s p e c u l a t i o n on t h e o r i g i n s of e v o l u t i o n a r y n o v e l t y . Q u a r t . R e v . B i o l . 46:111-133 B u r l e y , J . 1965. K a r y o t y p e a n a l y s i s o f S i t k a s p r u c e , P i c e a s i t c h e n s i s (Bong.) C a r r . S i l v a e G e n e t . 14:127-132. C a r l s o n , W.R. 1978. The B chromosome o f c o r n . 16:5-23.  Ann.Rev.Genet.  C a v a l i e r - S m i t h , T . 1978. N u c l e a r v o l u m e c o n t r o l by n u c l e o s k e l e t a l DNA, s e l e c t i o n f o r c e l l v o l u m e and c e l l g r o w t h r a t e , and t h e s o l u t i o n o f t h e DNA C - v a l u e p a r a d o x . J . C e l l Sc i . 34:247-278. C a v a l i e r - S m i t h , T . 1980a. r - and K- t a c t i c s i n t h e e v o l u t i o n o f p r o t i s t d e v e l o p m e n t a l s y s t e m s : c e l l and genome s i z e , p h e n o t y p e d i v e r s i f y i n g s e l e c t i o n , and c e l l c y c l e p a t t e r n s . Biosystems 12:43-59. Cavalier-Smith,T.  1980b. How  selfish  i s DNA? N a t u r e  285:617-618.  Chao,L. And E.C.Cox. 1983. C o m p e t i t i o n between h i g h and low m u t a t i n g s t r a i n s of E. C o l i . E v o l u t i o n 37(1 ) :125-134. C h a r l e s w o r t h , B. 1976. R e c o m b i n a t i o n m o d i f i c a t i o n i n a f l u c t u a t i n g e n v i r o n m e n t . G e n e t i c s 83:181-195. Chooi,W.Y. 1971. V a r i a t i o n i n n u c l e a r DNA V i c i a . G e n e t i c s 68:195-211.  content  Commoner,B. 1964. R o l e s o f d e o x y r i b o n u c l e i c a c i d N a t u r e 202:960-968. Cox, E.C. And T.C. G i b s o n . rates i n chemostats.  i n t h e genus in inheritance.  1974. S e l e c t i o n f o r h i g h G e n e t i c s 77:169-184.  mutation  C r i c k , F. 1971. G e n e r a l model f o r t h e chromosomes o f h i g h e r o r g a n i s m s . N a t u r e 234:25-27.  96  Crow, J . F . 1958. Some p o s s i b i l i t i e s f o r m e a s u r i n g s e l e c t i o n i n t e n s i t i e s i n man. H u m . B i o l . 3 0 : 1 - 1 3 . D a w k i n s , R. 1976. The S e l f i s h Gene. O x f o r d U n i v .  Press.  D a w k i n s , R. 1978. R e p l i c a t o r s e l e c t i o n a n d t h e e x t e n d e d p h e n o t y p e . Z . T i e r p s y c h o l . 47:61-76. D a w k i n s , R . 1982. The e x t e n d e d p h e n o t y p e : t h e gene a s t h e u n i t o f s e l e c t i o n . F r e e m a n , San F r a n s i s c o . D o b z h a n s k y , T. 1970. The g e n e t i c s o f t h e e v o l u t i o n a r y C o l u m b i a U n i v . P r e s s , N.Y.  process.  D o n a c h i e , W.D. 1974. C e l l d i v i s i o n i n b a c t e r i a . I N M e c h a n i s m a n d R e g u l a t i o n o f DNA R e p l i c a t i o n , e d . A.R. K o l b e r a n d M. K o h i j a m a . P l e n u m P r e s s , N.Y. D o o l i t t l e , W . F . And C . S a p i e n z a . 1980. S e l f i s h g e n e s , t h e p h e n o t y p e p a r a d i g m a n d genome e v o l u t i o n . N a t u r e 2 8 4 : 6 0 1 603. Dover,G.  1980. I g n o r a n t  DNA? N a t u r e 2 8 5 : 6 1 8 - 6 2 0 .  D o v e r , G a b r i e l . 1982. M o l e c u l a r d r i v e : a c o h e s i v e e v o l u t i o n . N a t u r e 299:111-117.  mode o f s p e c i e s  E b e l i n g , A . W . , N.B. A t k i n , a n d P.Y. S e t z e r . 1 9 7 1 . Genome s i z e s o f t e l e o s t e a n f i s h e s : i n c r e a s e s i n some d e e p - s e a f i s h e s . Amer.Nat. 105:549-561. E d s t r o m , J . - E . 1975. E u k a r y o t i c e v o l u t i o n b a s e d on i n f o r m a t i o n i n chromosomes on a l l e l e f r e q u e n c i e s . J . T h e o r . B i o l . 52:163-174. E l - L a k a n y M . H . , a n d 0. S z i k l a i . 1 9 7 1 . I n t r a s p e c i f i c v a r i a t i o n i n n u c l e a r c h a r a c t e r i s t i c s of Douglas f i r . Adv.Front.Plant S c i . 28:363-378. Endow.S. And J . G . G a i l . 1975. D i f f e r e n t i a l r e p l i c a t i o n o f s a t e l l i t e DNA i n p o l y p l o i d t i s s u e s o f D r o s o p h i l a v i r i l i s . Chromosoma 5 0 : 1 7 5 - 1 9 2 . E v a n s , G.M., a n d H. R e e s . 1 9 7 1 . M i t o t i c c y c l e s i n d i c o t y l e d o n s and m o n o c o t y l e d o n s . N a t u r e 2 3 3 : 3 5 0 - 3 5 1 . E v a n s , G.M., H. R e e s , C L . S n e l l a n d S. S u n . 1972. The r e l a t i o n b e t w e e n n u c l e a r DNA amount a n d t h e d u r a t i o n o f t h e m i t o t i c c y c l e . Chromosomes Today 3:24-31. F e l s e n s t e i n , J . 1974. The e v o l u t i o n a r y a d v a n t a g e o f r e c o m b i n a t i o n . G e n e t i c s 78:737-756.  97  F e l s e n s t e i n , J . And S. Yokoyama. 1976. The e v o l u t i o n a r y advantage of r e c o m b i n a t i o n . Genet i c s 83:845-859. F i n e r t y , J . P . 1980. The p o p u l a t i o n e c o l o g y o f c y c l e s i n s m a l l mammals: mathemat i c a l t h e o r y a n d b i o l o g i c a l f a c t - . Y a l e U n i v . P r e s s . 234 p p . F i s h e r , R.A. 1958. The g e n e t i c a l t h e o r y o f n a t u r a l s e l e c t i o n (2nd e d . ) . D o v e r , N.Y. 291 pp. F l a v e l l , R.B., M. B e n n e t t , J . S m i t h a n d D.B. S m i t h . 1974. Genome s i z e and t h e p r o p o r t i o n of r e p e a t e d n u c l e o t i d e sequence DNA i n p l a n t s . B i o c h e m . G e n e t . 12:257-269. G h i s e l i n , M . T . 1974. A r a d i c a l S y s t . Z o o l . 23:536-544.  solution  G h i s e l i n , M . T . 1981. C a t e g o r i e s , l i f e , 4:269-313.  t o the species and t h i n k i n g .  problem.  Behav.Brain  G i b s o n , T.C., M.L. S c h e p p e a n d E.C. C o x . 1970. F i t n e s s o f an E. c o l i m u t a t o r g e n e . Sc i e n c e 169:686-688. Gilbert,W.  1978. Why g e n e s i n p i e c e s ? N a t u r e  271:501.  G i l l e s p i e , J . H . 1978. A g e n e r a l m o d e l t o a c c o u n t f o r enzyme v a r i a t i o n i n n a t u r a l p o p u l a t i o n s . V . The SAS-CFF m o d e l . Theor.Popul.Biol.14:1-45. G i l l e s p i e , J . H . 1981. M u t a t i o n m o d i f i c a t i o n i n a environment. E v o l u t i o n 35(3):468-476.  random  G r i m e , J . P . And M . A . M o w f o r t h . 1982. V a r i a t i o n i n genome s i z e -an e c o l o g i c a l i n t e r p r e t a t i o n . N a t u r e 2 9 9 : 1 5 1 - 1 5 3 . H a l d a n e , J . B . S . 1957. The c o s t -of n a t u r a l s e l e c t i o n . 55:511-524.  J.Genet.  H i n e g a r d n e r , R . T . 1968. E v o l u t i o n o f c e l l u l a r DNA c o n t e n t i n T e l e o s t f i s h e s . A m e r . N a t . 102:517-523. H i n e g a r d n e r , R . 1974a. C e l l u l a r DNA c o n t e n t Comp.Biochem.Physiol. 47A:447-460.  of the m o l l u s c a .  H i n e g a r d n e r , R . 1974b. C e l l u l a r DNA c o n t e n t Comp.Biochem.Physiol. 49B:2l9-226.  of the echinodermata.  H i n e g a r d n e r , R . 1976. E v o l u t i o n o f genome s i z e . Pp.179-199 I N Molecular Evolution ,F.J.Ayala(ed.).Sinauer Assoc.Inc.,Sunderland,Mass. H i n e g a r d n e r , R . , and D.E. R o s e n . 1972. C e l l u l a r DNA c o n t e n t a n d t h e e v o l u t i o n o f t e l e o s t e a n f i s h e s . A m e r . N a t . 106:621-644.  98  Ho,M.W. And P . T . S a u n d e r s . 1979. B e y o n d n e o - D a r w i n i s m -- an e p i g e n e t i c a p p r o a c h t o e v o l u t i o n . J . T h e o r . B i o l . 78:573591. H o l m q u i s t , R., M. Goodman, T. C o n r o y and J . C z e l u s n i a k . 1983. The s p a t i a l d i s t r i b u t i o n o f f i x e d m u t a t i o n s w i t h i n g e n e s c o d i n g f o r p r o t e i n s . J . M o l e c . E v o l . 19:437-448. H s u , T.C. 1975. A p o s s i b l e f u n c t i o n o f c o n s t i t u t i v e h e t e r o c h r o m a t i n : t h e b o d y g u a r d h y p o t h e s i s . Genet i c s 79:137-150. H u l l , D a v i d L. 1980. I n d i v i d u a l i t y and A n n . R e v . E c o l . S y s t . 11:311-332.  selection.  James, A.P. 1959. The s p e c t r u m o f s e v e r i t y of m u t a n t e f f e c t . I . H a p l o i d e f f e c t s i n y e a s t . G e n e t i c s 43:1309-1324. James, A.P. 1960. The s p e c t r u m o f s e v e r i t y of m u t a n t e f f e c t s . I I . H e t e r o z y g o u s e f f e c t s i n y e a s t . Genet i c s 45:1627-1647. J e f f r e y s , A . J . 1981. R e c e n t s t u d i e s o f gene e v o l u t i o n u s i n g r e c o m b i n a n t DNA. Pp1-48 IN G e n e t i c E n g i n e e r i n g V o l 2, R . W i l l i a m s o n ( e d . ) , A c a d . P r e s s , N.Y. J o n e s , R.N., and L.N. Brown. 1976. Chromosome e v o l u t i o n and v a r i a t i o n i n Crepis. Heredity-36:91-104. J o n e s , G.H., and H. R e e s . 1967. Chromosome e v o l u t i o n H e r e d i t y 20:1-18. J o n e s , R.N., and H. R e e s . 1968. N u c l e a r DNA H e r e d i t y 23:591-605.  variation  Kadir,  Phalaris  Z.B.A. 1974. DNA v a l u e s i n t h e genus ( G r a m i n e a e ) . Chromosoma 45:379-386.  DNA  in Lolium. in Allium.  K a p l a n , R . H . And W.S. C o o p e r . 1984. The e v o l u t i o n o f developmental p l a s t i c i t y i n reproductive c h a r a c t e r i s t i c s : an a p p l i c a t i o n o f t h e " a d a p t i v e c o i n - f l i p p i n g " p r i n c i p l e . Amer.Nat. 1 2 3 ( 3 ) : 393-410. K a r l i n , S., and J . M c G r e g o r . 1974. T o w a r d s a t h e o r y o f t h e e v o l u t i o n of m o d i f i e r g e n e s . T h e o r . P o p u l . B i o l . 5:59-103. K e r k i s , J . 1938. The f r e q u e n c y o f m u t a t i o n s a f f e c t i n g B u l l . A c a d . S c i . USSR ( B i o l . ) 1938:75-96.  viability.  K i m u r a , M. 1956. A model o f a g e n e t i c s y s t e m w h i c h l e n d s t o c l o s e r l i n k a g e by n a t u r a l s e l e c t i o n . E v o l u t i o n 10:278-287. K i m u r a , M. 1960. Optimum m u t a t i o n r a t e a n d d e g r e e o f d o m i n a n c e a s d e t e r m i n e d by t h e p r i n c i p l e o f minimum g e n e t i c l o a d . J . G e n e t i c s 57:21-34.  99  K i m u r a , M. 1967. On t h e e v o l u t i o n a r y a d j u s t m e n t m u t a t i o n r a t e s . G e n e t . R e s . 9:23-34.  of  spontaneous  L a m p r e c h t , H. 1964. S p e c i e s c o n c e p t s and t h e o r i g i n of s p e c i e s . The two c a t e g o r i e s o f g e n e s -- i n t r a - and i n t e r s p e c i f i c ones. A q i . H o r t ique Genet i c a 22:272-280. L a r s o n , A l l a n . 1981. A r e e v a l u a t i o n of t h e r e l a t i o n s h i p b e t w e e n genome s i z e and g e n e t i c v a r i a t i o n . A m e r . N a t . 1 1 8 : 1 1 9 - 1 2 5 . L a y z e r , D . 1980. G e n e t i c v a r i a t i o n Amer.Nat. 115(6):809-826. L e i g h , E . 1970. N a t u r a l 104:301-305. L e i g h , E g b e r t . 1973. The Supp. 73:1-18.  and p r o g r e s s i v e  s e l e c t i o n and m u t a b i l i t y . evolution  evolution. Amer.Nat.  of m u t a t i o n r a t e s . G e n e t i c s  L e v i n , D . A . And S.W. F u n d e r b u r g . 1979. Genome s i z e i n angiosperms: temperate versus t r o p i c a l s p e c i e s . 1 14:784-795.  A m e r.N a t.  L e v i n s , R. 1962. T h e o r y o f f i t n e s s i n a h e t e r o g e n e o u s e n v i r o n m e n t I . The f i t n e s s s e t and a d a p t i v e f u n c t i o n . Amer.Nat. 96:361-373. L e v i n s , R. 1963. T h e o r y o f f i t n e s s i n a h e t e r o g e n e o u s e n v i r o n m e n t I I . D e v e l o p m e n t a l f l e x i b i l i t y and n i c h e s e l e c t i o n . Amer.Nat. 97:75-90. L e v i n s , R. 1964a. environment 7:224-240.  Theory of f i t n e s s i n a heterogeneous I I I . The r e s p o n s e t o s e l e c t i o n . J . T h e o r . B i o l .  L e v i n s , R. 1964b. T h e o r y o f f i t n e s s i n a h e t e r o g e n e o u s e n v i r o n m e n t I V . The a d a p t i v e s i g n i f i c a n c e o f gene E v o l u t i o n 18:635-638.  flow.  L e v i n s , R. 1965. T h e o r y o f f i t n e s s i n a h e t e r o g e n e o u s e n v i r o n m e n t V. O p t i m a l g e n e t i c s u s t e m s . G e n e t i c s 904.  52:891-  L e v i n s , R. 1967. T h e o r y o f f i t n e s s i n a h e t e r o g e n e o u s e n v i r o n m e n t V I . The a d a p t i v e s i g n i f i c a n c e o f m u t a t i o n . G e n e t i c s 56:163-178. L e v i n s , R. 1968. E v o l u t i o n i n C h a n g i n g Univ. Press, Princeton. L e w i n , R . 1982. M o l e c u l a r d r i v e : how 218:552-553.  Environments.  real,  how  Princeton  important? Science  1 00  L e w o n t i n , R.C. 1965. S e l e c t i o n i n a n d o f p o p u l a t i o n s . IN J.A.Moore ( e d . ) I d e a s i n modern b i o l o g y P r o c . V o l . 6 , Nat.Hi-st.Press,N.Y. M a y n a r d S m i t h , J . 1971. The o r i g i n a n d m a i n t e n a n c e o f s e x . IN G r o u p S e l e c t i o n , e d . G.C. W i l l i a m s . A l d i n e - A t h e r t o n , Chicago. M a y r , E. 1978. E v o l u t i o n . S c i . A m e r . Medawar, P.B.  239:46-55.  1967. The A r t o f t h e S o l u b l e . M e t h u e n , L o n d o n .  M e r g e n , F., a n d B.A. T h i e l g e s . 1967. I n t r a s p e c i f i c v a r i a t i o n i n n u c l e a r volume i n f o u r c o n i f e r s . E v o l u t i o n 21:720-724. M i k s c h e , J . P . 1971. I n t r a s p e c i f i c v a r i a t i o n o f DNA p e r c e l l between P i c e a s i t c h e n s i s (Bong.) C a r r . P r o v e n a n c e s . Chromosoma 32:343-352. M i k s c h e , J . P . , and Y. H o t t a . 1973. DNA b a s e c o m p o s i t i o n a n d r e p e t i t i o u s DNA i n s e v e r a l c o n i f e r s . Chromosoma 41:29-36. M i r s k y , A . E . And H. R i s . 1951. The d e o x y r i b o n u c l e i c a c i d c o n t e n t of a n i m a l c e l l s a n d i t s e v o l u t i o n a r y s i g n i f i c a n c e . J.Gen.Physiol. 34:451-462. M u k a i , T. 1964. The g e n e t i c s t r u c t u r e o f p o p u l a t i o n s o f D r o s o p h i l a melanogaster I . Spontaneous mutation r a t e o f p o l y g e n e s c o n t r o l l i n g v i a b i l i t y . Genet i c s 50:1-19. Nagl,  W. 1974. R o l e o f h e t e r o c h r o m a t i n i n t h e c o n t r o l of c e l l c y c l e d u r a t i o n . N a t u r e 249:53-54.  Ohno, S. 1969. The s p o n t a n e o u s m u t a t i o n r a t e r e v i s i t e d a n d t h e p o s s i b l e p r i n c i p l e o f p o l y m o r p h i s m g e n e r a t i n g more p o l y m o r p h i s m . C a n . J . G e n e t . C y t o l . 11:457-467. Ohno,S. 1970. E v o l u t i o n by gene d u p l i c a t i o n . S p r i n g e r - V e r l a g , N.Y. Ohno,S. 1972. So much " j u n k " DNA S y m p . B i o l . 23:366-370.  i n o u r genome. B r o o k h a v e n  O r g e l , L . E . , a n d F . H . C . C r i c k . 1980. S e l f i s h DNA: p a r a s i t e . N a t u r e 284:604-607.  the ultimate  P a t t e e , H . H . ( e d . ) 1973. H i e r a r c h y T h e o r y : t h e c h a l l e n g e o f c o m p l e x s y s t e m s . G e o r g e B r a z i l l e r , N.Y. 156pp. P i e r c e , B . A . And J . B . M i t t o n . 1980. The r e l a t i o n s h i p between genome s i z e a n d g e n e t i c v a r i a t i o n . A m e r . N a t . 116:850-861.  101  P o w e l l , J . 1971. G e n e t i c p o l y m o r p h i s m s i n v a r i e d S c i e n c e 174:1035-1036.  environments.  P r i c e , G . R . 1972. F i s h e r j s f u n d a m e n t a l t h e o r e m made c l e a r . Hum.Genet. 36:129-^40. P r i c e , H . J . 1976. E v o l u t i o n o f DNA B o t a n . R e v . 42:27-57.  content  i n higher  Annals  plants.  R e e s , H . , and M . H . H a z a r i k a . 1969. Chromosome e v o l u t i o n i n L a t h y r u s . Chrom.Today 2:158-165. R o u g h g a r d e n , J . 1979. T h e o r y o f p o p u l a t i o n g e n e t i c s and e v o l u t i o n a r y e c o l o g y : and i n t r o d u c t i o n . M a c M i l l a n , S a l t h e , S . N . 1983. An e x t e n s i o n a l d e f i n i t i o n i n d i v i d u a l s . Amer.Nat. 121:139-144.  of  N.Y.  functional  Simon,H.A. 1962. The a r c h i t e c t u r e o f c o m p l e x i t y . P r o c . A m e r . P h i l o s o p h i c a l S o c . 106:467-482. Simon,H.A. 1973. The o r g a n i z a t i o n o f c o m p l e x s y s t e m s . IN H i e r a r c h y T h e o r y , G e o r g e B r a z i l l e r , N.Y. 156pp. S l o b o d k i n , L . B . 1964. The s t r a t e g y o f e v o l u t i o n . A m e r i c a n S c i e n t i s t 52:342-357. S l o b o d k i n , L . B . 1968. Toward a p r e d i c t i v e t h e o r y of. e v o l u t i o n . R . C . L e w o n t i n ( e d . ) , P o p u l a t i o n b i o l o g y and e v o l u t i o n , Syracuse Univ. Press. S m i t h , J . B . And M . D . B e n n e t t . 1975. DNA v a r i a t i o n Ranunculus. Heredity 35(2):231-239.  IN  i n t h e genes of  S o m p y r a c , L., a n d C. M a a l o e . 1973. A u t o r e p r e s s o r model f o r c o n t r o l o f DNA r e p l i c a t i o n . A t u r e , N e w B i o l . 2 4 1 : 1 3 3 - 1 3 5 . Sparrow, A.H., K.P. B a e t c k e , D.L. S h a v e r and V. P o n d . 1968. The r e l a t i o n s h i p o f m u t a t i o n r a t e p e r r o e n t g e n t o DNA content per chromosome and to interphase chromosome volume. G e n e t i c s 59:65-78. S p a r r o w , A.H., and J . P . M i k s c h e . 1961. C o r r e l a t i o n volume a n d DNA content with higher plant c h r o n i c r a d i a t i o n . S c i e n c e 134:282-283.  of nuclear tolerance to  S p a r r o w , A . H . , H . J . P r i c e and A . G . U n d e r b r i n k . 1972. A survey of DNA c o n t e n t p e r c e l l and p e r chromosome o f p r o k a r y o t i c and eukaryotic organisms: some e v o l u t i o n a r y c o n s i d e r a t i o n s . B r o o k h a v e n .Symp .Biol . 2 3 : 4 5 1 - 4 9 4 . S t a n l e y , S.M. 1975. C l a d e s v e r s u s c l o n e s i n have s e x . S c i e n c e 190(4212):382-383.  evolution:  why  we  1 02  Stanley, S.M. 1979. M a c r o e v o l u t i o n : Freeman, San F r a n c i s c o . Stebbins, G.L. 1966. Chromosomal Science 152:1463-1469.  pattern  variation  and  and  process.  evolution.  Strauss, N.A. 1971. Comparative DNA r e n a t u r a t i o n k i n e t i c s i n Amphibians. Proc.Nat1.Acad.Sci. 68:799-802. Templeton, A.R. 1981. Some comments on "Genetic v a r i a t i o n and progressive e v o l u t i o n " by D. Layzer. Amer.Nat. 117:10491051. Thoday,J.M. 1953. Components 7:96-113.  of  fitness.  Symp.Soc.Exp.Biol.  Thompson, P.E. 1962. Asynapsis and D. melanoqaster. Genet i c s 47 : 337-349.  mutability  in  Underbrink, A.G., A.H. Sparrow and V. Pond. 1968. Chrosomes and cellular sensitivity I I . Use of i n t e r r e l a t i o n s h i p s among chromosome volume, n u c l e o t i d e content and Do of 120 diverse organisms in predicting radiosensitivity. Radiat.Bot. 8:205-238. V a l e n t i n e , J.W. 1976. Genetic strategies of a d a p t a t i o n . IN Molecular E v o l u t ion, F . J . Ayala (ed.), Sinauer Assoc. Inc., Mass. Van't H o f f , J . And A.H. Sparrow. 1963. The r e l a t i o n s h i p between DNA content, nuclear volume, and m i t o t i c c y c l e time. P r o c . N a t l . A c a d . S c i . U.S. 49:897-902. Vrba,E. 1980. E v o l u t i o n , s p e c i e s and f o s s i l s : evolve? South A f r i c a n J . S c i . 76(2):61~84.  how  does  life  Vrba,E. 1983. Macroevolutionary t r e n d s : new p e r s p e c t i v e s on the roles of a d a p t a t i o n and i n c i d e n t a l effect. Sc ience 221:387-389. Waddington, C H . 1957. The s t r a t e g y of the genes. The MacMillan Co., N.Y.,ix+262pp. Waddington, C H . 1974. A c a t a s t r o p h e Ann.N.Y.Acad.Sci. 231:32-41. Waddington, CH. developmental  theory  of  evolution.  And E. Robertson. 1966. S e l e c t i o n f o r c a n a l i z a t i o n . Genet.Res. 7:303-312.  Walker,P.M.B. 1968. How d i f f e r e n t are animals? Nature 219:228-232.  the DNAs  from  related  1 03  Warburton,F.E. 1967. A model of n a t u r a l s e l e c t i o n b a s e d t h e o r y of g u e s s i n g games. J . T h e o r . B i o l . 16:78-96. W i l l i a m s , G.C. 210pp.  on t h e  (ed.) 1971. G r o u p S e l e c t i o n A l d i n e - A t h e r t o n ,  N.Y.  Yang, D.P., and E.O. Dodson. 1970. The amounts of nuclear DNA and the duration o f DNA s y n t h e s i s p e r i o d (S) i n r e l a t e d d i p l o i d and a u t o t e t r a p l o i d s p e c i e s of oats. Chromosoma 31:309-320. Yunis,J.J. DNA,  And W.B.Yasmineh. 1971. H e t e r o c h r o m a t i n , and c e l l f u n c t i o n . S c i e n c e 174:1200-1209.  satellite  Z u c k e r k a n d l , E . 1976. Gene c o n t r o l i n e u k a r y o t e s and t h e c-value p a r a d o x : " e x c e s s " DNA a s an impediment t o t r a n s c r i p t i o n of c o d i n g s e q u e n c e s . J . M o L e c . E v o l . 9:73-104.  104  APPENDIX I. F I T N E S S , PERSISTENCE, AND  I the  am  convinced that  t i m e s c a l e d e p e n d e n c e of  this oversight  i s the  I  will  of  s e l e c t i o n with  t r y to  confusion time  the  favors  is  of  the  next,  only  the  proportions the  a  the  follow  failure  to  i t with  an  that  confusion. results  example  of  t o d i s t i n g u i s h among d i f f e r e n t  mean  truism  short  "that  or  one  (Dawkins  t e r m , say  phenomena  of v a r i o u s  relative  If  defined  fittest" in  we  those  see  1982).  f r o m one are  properties  e f f e c t i v e r a t e of  assumes  that  in  Looking  the  changes  in  f i t n e s s gets  defined  reproduction. our  longer  relative  contributes  rate  to  of  s t a t e of  world  the  term the  proportion  (plainly  different  definition  not of  the  passing  ability  e n v i r o n m e n t a t any  increase).  adaptedness  Unless  increases  s o , e.g.  sex  and  of to  definition  Instead  of  of  no  sex  compared one  anything  the  ) we  will  truism.  time cope  time that  a d a p t a b i l i t y i n the  f i t n e s s to s a t i s f y  t i m e s c a l e s p r o d u c e d i f f e r e n t r e s u l t s of different  a  to  c h a n g e , i . e . a d a p t a b i l i t y , becomes more i m p o r t a n t a d a p t e d n e s s t o the  at  generation  relative  c h a r a c t e r i s t i c s , and  i m p l i e s change, then over the  (e.g.  enormous amount of  the q u a l i t a t i v e change i n the  t i m e s c a l e , and out  s e l e c t i o n , and  to  t o s e l e c t i o n " , t o d e l i b e r a t e l y make " n a t u r a l s e l e c t i o n  population  with  r e s u l t s of  been p a i d  scales.  relevant  with  enough a t t e n t i o n has  s o u r c e of an  illustrate  arising  Fitness  as  not  TIME SCALES  same  need a  Different  selection, requiring  a  fitness.  h a v i n g the  word " f i t n e s s "  be  so m a l l e a b l e ,  and  1 05  therefore  vague,  properties the  short  as  take  are convenient, time s c a l e n o t i o n  adaptedness. Dawkins the  to  word " f i t n e s s "  properties  meaning  of  i t i s probably better of  differential  whatever  to leave  i t as  reproduction  even w i t h  this  and  constraint  has a t l e a s t f i v e d i f f e r e n t d e f i n i t i o n s . F o r t o s e l e c t i o n on l o n g e r  or " p e r s i s t a b i l i t y "  Crandall,  the  (1982) shows t h a t  relevant  "persistence"  on  could  t i m e s c a l e s t h e words  p e r h a p s be u s e d .  S t e a r n s a n d Dudman ( i n p r e p ) r e c e n t l y  constructed  two  c o m p u t e r m o d e l s , a n d t e s t e d t h e w o r t h of v a r i o u s d e f i n i t i o n s  of  f i t n e s s a s p r e d i c t o r s o f t h e o u t c o m e . The two m o d e l s d i f f e r e d  in the  spatial  microscopic  scale  model  in  viewed  which the  the world  world  was  as c o n s i s t i n g of a  number o f p a t c h e s , w h e r e a s t h e m a c r o s c o p i c w o r l d an  infinite  number  "productivity" microscopic  of  was  model t h e  persistence"  --  and  patches. best  best  predictor  This  indicated  a  m o d e l s , w h i c h t o my m i n d was extinction  in  the  the  predictor, was  will  finite  results  appropriate  latter whereas  model i n the like  a  p a t c h e s was i n c r e a s e d  qualitative embodied  difference in  the  in  without t h e two  possibility  model. And, j u s t as a s p a t i a l  of  scale  a "persistence",  I  t h a t a t e m p o r a l s c a l e t h a t makes e x t i n c t i o n a f a c t o r  make " f i t n e s s " a The  finite  v i e w was one o f  "something  t h a t made e x t i n c t i o n a f a c t o r made " f i t n e s s " am c l a i m i n g  The  t h e two m e a s u r e s were f o u n d n o t t o be t h e  same e v e n a s t h e number o f f i n i t e bound.  In  the  viewed.  "persistence".  of n a t u r a l s e l e c t i o n and, i n consequence, the  properties  to  be  embodied  in  "fitness",  are  d e p e n d e n t on t h e t i m e s c a l e o v e r w h i c h t h e r e s u l t s a r e v i e w e d . As  an  example  of the confusion  possible  i f time s c a l e i s  106  not  taken  i n t o account, consider  Lewontin's  (1965)  statement:  " . . . t h e c o u r s e of e v o l u t i o n i s determined by a similar maximizing principle b o t h w i t h i n and b e t w e e n p o p u l a t i o n s . W i t h i n p o p u l a t i o n s t h e r e s u l t of n a t u r a l s e l e c t i o n , by and large, i s t o c h a n g e t h e f r e q u e n c y of g e n o t y p e s t o m a x i m i z e t h e i n t r a p o p u l a t i o n f i t n e s s . Between p o p u l a t i o n s i t i s the probability of survival that i s maximized and t h e n e t r e s u l t i s a compromise between t h e s e f o r c e s , the degree to which one or the other i s i m p o r t a n t d e p e n d i n g upon t h e a u t e c o l o g y of t h e s p e c i e s . " The  different  perceives  at  "maximizing  different  different  goals  switching  from  levels  one  level  the  two  versus a  long  whole  its  views the  any  are  level  can  s i z e , or s i z e  really  be  of  short  Lewontin  fact  term gains  changed  the  selection.  "short  term  gain  short  term  for  t e r m s of a v e r a g e f i t n e s s  (W),  selection:  r e l a t i v e to other the  in  sides  "gain"  in  the  to  that  of n a t u r a l  just  not  two  of  t e r m what m a t t e r s i s n o t  record  to the  results  t e r m p e r s i s t e n c e " . The  population  absolute longer  on  but  t o a n o t h e r L e w o n t i n has  maximizing p r i n c i p l e s  compromise  that  o f o r g a n i z a t i o n a r e due  of n a t u r a l s e l e c t i o n ,  t i m e s c a l e o v e r w h i c h he The  principles"  i n the  populations.  history  (W,size),  of  but  But  the that  of  over a  population, i t manages t o  persist. Similarly, lineage  within  proportion is  not  on  of  the  the  short  a  are  in  population But  i n the  term  gains  absolute long  run  numbers what  number o r r e l a t i v e number of o f f s p r i n g , exceeds the  number of  deaths  of  but --  a or  matters that that  the the  persists.  When considered fitness.  the  population.  number o f o f f s p r i n g lineage  a lower l e v e l ,  looking only He  at  short  selection term  overlooked  gain, the  fact  within  populations  embodied that  in in  the the  Lewontin notion  long  term  of the  1 07  genotypes and  traits  are  those  the  population  favored by s e l e c t i o n  within  a  population  enhancing p e r s i s t e n c e or p r o b a b i l i t y of s u r v i v a l . level  Lewontin  saw  only  the  "maximization" of p r o b a b i l i t y of s u r v i v a l and population  i n c r e a s e s and  other  long  important  in a p o p u l a t i o n - l e v e l d e f i n i t i o n of " f i t n e s s " analogous  The  results  of  concept  level  considered.  of  the  n a t u r a l s e l e c t i o n d i f f e r depending on  organization  "Fitness"  to  (W) .  time s c a l e over which they are examined. They do not the  term  not the short term  f e a t u r e s that would be  " i n d i v i d u a l " , or w i t h i n - p o p u l a t i o n  belongs  " p e r s i s t e n c e " on the e v o l u t i o n a r y  at  which  on  a  one.  On  depend  selection  shorter  time  is  the on  being scale,  . 1 0 8  APPENDIX II_ THE FUNCTIONAL HIERARCHY  The of  word  'fitness'  phenotypes  Natural  that  i s intended  natural  to reflect  selection  favors  (Dawkins  1982).  s e l e c t i o n i s t h e n e t r e s u l t o f many p r o c e s s e s a t work i n  a population.  Some p r o c e s s e s a r e s l o w e r  advantageous  with  over the longer of  the property(ies)  change.  respect  than o t h e r s .  A  quality  t o a s l o w p r o c e s s becomes  important  t e r m a s t h a t p r o c e s s becomes an i m p o r t a n t  Thus,  time  important,  and  what  selection,  so ' f i t n e s s '  cause  s c a l e d e t e r m i n e s what p r o c e s s e s c a n be  properties should  will  be  be d e f i n e d  favored  by  time s c a l e  natural  dependently  (see Appendix I ) . What  are a l l the properties that  embody? Can we somehow make a l i s t their  importance  equivalently,  over  longer  we  describe  can  of  fitness potentially properties  and how  longer  time  the  results  s e l e c t i o n change w i t h  time s c a l e ? This w i l l  of  habit  the  traditional  order  scales? of  of Or,  natural  i n v o l v e breaking out  of c o n f i n i n g n a t u r a l s e l e c t i o n t o a  t i m e s c a l e o f one g e n e r a t i o n , relative  in  could  when t h e most i m p o r t a n t  e f f e c t i v e reproductive  rate  (the usual  quality i s  definition  of  f itness).  The  Selfish Individual Let  us  generation. survive  to  first  consider  a  time  scale  An o r g a n i s m h a s c e r t a i n q u a l i t i e s maturity  as  phenotype c o u l d a r i s e that  shorter  t h a n one  that enable i t to  i t must do t o r e p r o d u c e . N o t e t h a t a invests highly  in  these  qualities,  109  spending nothing an  all  of  energies  for reproductive  individual  individual We  self-maintenance  investment. Reproduction risk,  and  leaving  always  probably  costs  lowering  its  survival rate.  by  recognize  natural  t i m e s c a l e -maintenance greatest  on  organism i n energy or  generally  favored  we and  selection  reproduction  that  representation  that  such a s t r a t e g y on  expect a balance  number of  Note  being  its  we  then  to  be  favored,  greater  proportion  of  next  to  be  generation  between  selfthe  generation. increasing  t o be  'success',  proportional  i . e . to i n d i c a t e  on a wi t h i n - g e n e r a t i o n t i m e s c a l e ,  s t r a t e g y of p u t t i n g a l l e n e r g i e s appear  investment  consider  in a population  'selected',  in  generation  not  such that a zygote c o n t r i b u t e s  zygotes to the if  the  would  into  self-preservation  the  would  s i n c e these s t r a t e g i s t s would comprise a  the a d u l t p o p u l a t i o n  than  of  the  zygote  populat ion. 'Individual' that are from  being  one  fitness). can can  s a i d t o be  selected?  or  being  it  not  selected  semi-conserved  take  If the  the risk  individuals is (e.g.  to  our  not  The on  the  entity that  individual and  g e n e s t h e y c,ar.ry  even p e r s i s t ,  is  scale  usual  a  how and the  (1976,  all-important,  generation, w i t h no  is  i s Dawkins'  spend the energy t o  within  so  that p e r s i s t s ,  time  g e n o t y p e . That  self-maintenance  f i t according  but  (consider Hamilton's i n c l u s i v e  be  S e l e c t i o n of  are  next  o r g a n i s m s do  basic point.  strategies  to the  individual  v i e w e d as  should  sorted out,  The  genotype, 1982)  s e l e c t e d , or  generation  they be  s e l e c t i o n i s a misnomer. I t i s not i n d i v i d u a l s  why  reproduce? and  favors  reproduction)  trans-generation  view  that of  1  natural I  s e l e c t i o n and could  p a y i n g too problem  t h e n our  The  criticized  much a t t e n t i o n  j_s  qualities  be  d e f i n i t i o n of  one  that  of  a  success  longer-than-usual  selection  will  (one-generation) i m p o r t a n t , and genetic  favor  are  emphasize  that  the  going to t a l k about  more  or  less  the  successful,  is c r i t i c a l .  i t requires  variation  genotypes  adaptability) with  in  "favors".  that may  be  may  be  less  we  over  is  future  now  maintaining becomes of  Undirected production  fitter  i n the  p r e s e n t . So  we  world,  maintenance  less  have changed the  Adaptability  and  p r o d u c t i o n of  f i t at  which  in  adaptability  production  population. the  in a changing  involved  Genetic  the  a  scale,  properties  i m m e d i a t e f i t n e s s , or  time s c a l e  selection  time  fitness.  genetic variants' implies  the  I f we  me  or  Self i s h Lineage  natural  odds  a s e m a n t i c game h e r e ,  to words. Let  make some p h e n o t y p e s  d e f i n i t i o n of  On  and  fitness.  for playing  semantics.  1 0  fit  view  the  adaptability  results  q u a l i t i e s that worth  some  genotypes,  (important  " a d a p t e d n e s s " , and  for  is  at  by  changing  of  natural  natural  cost  of  selection  in  terms  of  immediate f i t n e s s . Note  the  concurrent  scale. Within a generation to generation variation  i t i s the  change i t i s the  lineage,  'selected  i n d i v i d u a l . From  p r o d u c t i o n becomes a v i r t u e , and genotype  for variation production. and  over  the  unit' with  long  term  the --  selected the  time  generation  g e n o t y p e . O v e r many g e n e r a t i o n s  s o m e t h i n g more i n c l u s i v e t h a n t h e sacrificed  in  genetic unit  is  latter  is  I have c a l l e d t h i s u n i t  the  rt looks s e l f i s h  the  --  not  111  genotype, and not t h e i n d i v i d u a l .  Another S e l f i s h  Level?  We now have t h r e e fitness could longer  increasing selection an  scale rate,  time favors  environment  that exerts with The  they  and scale  that  importance  production.  can  take  place  the s e l e c t i o n pressure  i n a changing  itself.  that  with  effective  The  effect  i n changing the p r o p e r t i e s that  i s n o t due t o t i m e  of  natural  I t i s t h e change  over a longer  time  favoring the a b i l i t y  in  period  to  cope  requires v a r i a t i o n production.  production  is  to  permit  genetic  environment.  i s one l a s t  the environment  change,  increasing  variation  ' f u n c t i o n ' of v a r i a t i o n  There  of  a r e : self-maintenance,  change ( a d a p t a b i l i t y ) ,  adaptation  If  embody. I n o r d e r  time  reproduction  d i f f e r e n t p r o p e r t i e s t h a t a d e f i n i t i o n of  strategy  that  i s one o f v a r y i n g  I would l i k e  r a t e s and/or  i t m i g h t be " u s e f u l " t o v a r y  to consider. direction  of  t h e f r e q u e n c y and k i n d of  variant production  (i.e.  if  the  p r o d u c e d by one l i n e a g e were r a r e l y s u i t e d t o  the  way t h e e n v i r o n m e n t was c h a n g i n g ,  variants  successful unit  t o produce m e t a v a r i a t i o n ) .  scheme w o u l d b e g i n  consisting  of  these  adaptable t o the current think  that the species  considered  variant production  lineage  with  a  way,  more  t o p r e d o m i n a t e . The more i n c l u s i v e lineages  pattern  of  would thereby  become more  environmental  change.  I  c o r r e s p o n d s t o t h i s more i n c l u s i v e u n i t ,  s i n c e t h e member p o p u l a t i o n s generally  a  That  to  can  be  and  share  lineages the  modified.  many These  of  a  species  are  m e c h a n i s m s by w h i c h include  s t r u c t u r e , a s s o r t a t i v e n e s s of m a t i n g , and d i s p e r s a l  breeding  tendencies.  Table 4.  P r o p e r t i e s r e q u i r e d f o r p e r s i s t e n c e under v a r i o u s environmental  Environmental Conditions  conditions.  Persistence-related Properties  Persisting Entity  d u r a b i l i t y and self-maintenance (phenotypic f l e x i b i l i t y )  individual  The i n d i v i d u a l i s v u l n e r a b l e t o c e r t a i n d e s t r u c t i v e f o r c e s and l a c k o f s u p p l i e s f o r metabolism.  CONSTANT over time and heterogenous i n space  reproduction  genotype  S i n c e i n d i v i d u a l s occupy d i f f e r e n t l o c a t i o n s i n space, r e p r o d u c t i o n c r e a t e s " s p a t i a l r e f u g e s " f o r t h e genotype.  CHANGING over time and homogeneous i n space  variation  lineage  Without s p a t i a l r e f u g e s , a genotype w i l l go e x t i n c t . W i t h i n a l i n e a g e , o n l y the v a r i a n t genotypes t h a t a r e t o l e r a n t t o t h e change will persist.  CHANGING i n r a t e and/or d i r e c t i o n of change  metavariation  species  Metavariation i n e f f e c t explores d i f f e r e n t v a r i a t i o n p r o d u c t i o n schemes f o r the one b e s t s u i t e d t o the p a r t i c u l a r k i n d o f environmental change.  CONSTANT over and space  time  Comment  113  The  environments  and  strategies  s u m m a r i z e d i n T a b l e 4. N o t e t h a t required  for  persistence  higher  in  described level  successively  above  are  strategies  are  more  environments, which roughly  correspond  scales.  e n v i r o n m e n t s , where t h e  I n more c o m p l i c a t e d  o f u n i t s a t one of  l e v e l of  persistence  is  organization  higher,  u n i t s at  level  The  the  only to the  possible  and  longer  persistence  becomes i m p o s s i b l e , by  system that  moving  time  one  a  kind  level  generates the  of  ephemeral  below.  Ex i s t e n t i a l Game I  find  it  conceptually  p r o b l e m of o b s e r v a t i o n . existent existing (Note  from  one  that  these  1. c o u l d  these be  could  high  degree  be  to  description  forms  t i m e t o a n o t h e r . Some p r e v i o u s l y  a b s e n t , o r c h a n g e d . Some m i g h t are  highly  things  be  dependent  we  see  re-created  come i n t o b e i n g  living  permitting  on  a t any  by  new. our  time  the  abiotic  imbue l i v i n g  1 9 6 8 ) . We Of  persist.  i n t h e more d i s t a n t p a s t  do  not the  This  see  can  r u l e out  those we  justifies  o f e v o l u t i o n as an  their  systems w i t h  things  and  PERSISTENCE.  t h i n g s , because of  o f o r g a n i z a t i o n , we  'persistability'.  living  a  or  oriented properties (see A y a l a  in  constantly  have  c a s e of  a t e v o l u t i o n as  observe changes i n the  " f o r m s " . ) The  have some q u a l i t y In the  u s e f u l to look  categories  environment, 2.  We  point  f o r m s m i g h t be  d e f i n i t i o n s of  to  organization  to longer  complicated  do  complexity (1).  and  Persistence-  internal  teleology  forms  with  see,  their  p u r p o s e seems  Slobodkin's  metaphorical  existential  less  game among  or  no  "players"  11 4  with various  persistence-oriented  Unfortunately, are,  Slobodkin  was  properties,  not  players  are  i s determined  is a  "player"  way  of  Functional It  by  what  strategies  'lower'  game". T a b l e 4 g i v e s  that  short be  term.  rearranged  hierarchy  (1978)  i f they  i n Figure  that  organisms,  funct i o n a l one. This  categories  is  dependent of the  cost  not  production  extinction  and  i n the  s t r a t e g i e s of Table 4 can  i n t o the h i e r a r c h i c a l c o n t r o l system or funct i o n a l  organs,  Others  s t r a t e g i e s of  (survival  variation  6.  Although  a hierarchical organization  evolutionary  "players"  But s e l f - m a i n t e n a n c e does  The p e r s i s t e n c e - o r i e n t e d  a structural hierarchy tissues,  rate  self-maintenance  Likewise,  are superfluous  portrayed  recognize  the  the persistence-oriented  strategy,  reproduction.  adaptability  of  basic strategies.  i n d i v i d u a l ) as w e l l as f e c u n d i t y . require  level  Hierarchy  i s clear  the  level  are allowed,  game a r e . E a c h  Table 4 a r e 'nested'. E f f e c t i v e reproduction on  population  k e e p i n g a more i n c l u s i v e , l o n g e r - l i v e d  i n the " e x i s t e n t i a l  corresponding t o various  The  and  The p r e s e n t a p p r o a c h makes i t c l e a r t h a t who t h e  i . e . what t h e r u l e s o f t h e e x i s t e n t i a l strategy  "strategies".  c l e a r a b o u t who t h e p l a y e r s  a n d he m i x e d e x a m p l e s o f i n d i v i d u a l  considerations.  or  explanations have  b a s e d on  suggested  of b i o l o g y ,  i s described populations,  i s awkward  in  i t i s common  view  i ti s usually  (molecules,  cells,  ecosystems), of  to  the  not a  fact  that  a r e i n terms of f u n c t i o n .  suggested function  reorganizing rather  than  " r e p l i c a t o r " as a g e n e r a l  biology  around  structure.  Dawkins  term f o r a " u n i t of  Persisting 'Unit'  METAVARIATION NEXT TIME  SPECIES  <D  VARIATION NEXT TIME  VARIATION  c  O CL  (/)  LINEAGE  <D  s-  Ss o <D  REPRODUCTION NEXT TIME  REPRODUCTION  NUMBERS'  GENOTYPE  NUMBERS NEXT TIME  I N D I V I DUAL  PHENOTYPES  ^Maintenance  o f numbers  F i g u r e 6.  ( s h o r t term) r e q u i r e s maintenance  A hierarchical control  of reproductive  system o f b i o l o g i c a l  fitness  (longer  persistence-oriented  term),  strategies.  11 6  selection".  Hull  "replicator" stem  (1980)  thinks  description  from  of  the  pair  the  u s u a l '""one-generation  slop  from  variability  is  less-than-perfect  (1974) a l s o s u g g e s t s t h a t b i o l o g i c a l  t h e main r e a s o n s why t h e u s u a l  species d e f i n i t i o n isolation  terms terms  time  scale  profoundly  little  replication. Ghiselin  categories  be  'defined "This  in  i s one  f o r m u l a t i o n of the b i o l o g i c a l  i s so a t t r a c t i v e .  obviously  over-  considered  terms of t h e c a u s e s of e v o l u t i o n , and s u g g e s t s t h a t of  of  m e c h a n i s m o f n a t u r a l s e l e c t i o n . They  emphasize r e p r o d u c t i o n , and than  the  a n d " i n t e r a c t o r " a r e more a p p r o p r i a t e . These  directly  more  that  Gene f l o w a n d  influence  the  reproductive properties  of  o r g a n i sms." A h i e r a r c h y o f p h y s i o l o g i c a l r e s p o n s e s y s t e m s was by  Bateson  (1963),  populations  into  a n d s p e c i e s by S l o b o d k i n  metavariation fitness  and e x t e n d e d  as  as a  logical  survival  the  (persistence)  ecological  (1964,  extension.  realm  of  1968). I have added  Thoday  (1953)  probability,  d i s c u s s i o n o f t h e "components o f f i t n e s s "  described  and  defined in his  he made s e v e r a l o f t h e  same p o i n t s I have made. To my k n o w l e d g e , F i g u r e  6 i s the  first  g r a p h i c a l p o r t r a y a l of such a f u n c t i o n a l h i e r a r c h y . Figure  6  puts  the process  of r e p r o d u c t i o n  I t a l s o shows us a s c a l e o f p r o c e s s e s  of  one  theory  moves up t h e h i e r a r c h y . H i e r a r c h y  1973)  tells  be more processes  at  the  in  short  top  to  term  (Simon  patterns,  be more i m p o r t a n t  e v o l u t i o n a r y p a t t e r n s . What t h i s  implies  place  of very  to  decreasing  us t o e x p e c t t h e f a s t e r p r o c e s s e s  important  look  for explanation  in perspective.  is  speeds  as  1962, P a t t e e  a t the bottom t o and  the  slower  i n the long that  the  term,  logical  long term p a t t e r n s  like  1 17  the  mode of  evolution  metavariation special  (e.g.  level.  can  be  important  in  inclusive longer  in  time  of  is  f a s t p r o c e s s e s of  at  selection". i s the  Lewontin's statement  construe drift  and  the  So  to  processes more  t a l k i n g about e v o l u t i o n ,  over  t a l k i n g about " s e l e c t i o n "  vice-versa.  in Appendix  slower  successively  same as  " u n i t s " , and  the  effective.  longer terms c o r r e s p o n d  scales  more i n c l u s i v e  less  the  illustrates a duality:  the  "units  which  more or  Figure 6 also  gradual)  I n s t e a d , most c u r r e n t e x p l a n a t i o n s  situations  selection  punctuated vs.  (See  my  discussion  of of  I.)  Fitness I  think  biology  the  favored  is  desired  by  translated e.g.  it  the  p r o b l e m s and  of  this  same  concept  of  assume  or  It  have  different  time  scales.  "fitness"  give  in  evolutionary  "those  when  qualities  this  notion  empirically  effective  explained  is  is  more  ambiguities arise. is  that  fitness  selection".  vigor  confusion  different  to  something  physiological  adopt  meaning  natural into  investigators  correct  by  tractable,  reproductive rate,  I n my  o p i n i o n at  the  fact  perspectives  and  least  that  to  that some  different  unconsciously  That f a c t would a s s u r e t h a t rise  is  different  the  empirical  definitions. The it  must  d e f i n i t i o n s of be  above  w i t h the  so  numerous t h a t  s p e c i f i e d which d e f i n i t i o n p e r t a i n s .  g r e a t e r c o n c i o u s n e s s of shown  f i t n e s s are  how  time s c a l e  the of  the  time scale  "favoritism"  of  o b s e r v a t i o n , and  i n any  work  I recommend a  being considered.  I  natural  changes  selection  have g i v e n  a  range  have  of  1 18  strategies different  or time  p r o p e r t i e s t h a t are d i f f e r e n t i a l l y scales.  On  the  longest  m e t a v a r i a t i o n becomes a v a l u a b l e s t r a t e g y .  of  emphasized by time  scales,  1 19  APPENDIX I I I  A COMPUTER MODEL FOR COMPARING VARIATION PRODUCTION STRATEGIES IN VARIOUS ENVIRONMENTS  This  computer  program  evolutionary  "game". The  populations  with  living The  strategy  "players"  different  in arbitrarily of  i s written  player  variation.  It  different  fixed  following  description,  letters.  can  (In the actual  reproducing "strategies",  one-dimensional  environments.  i s f i x e d f o r a g i v e n r u n -- t h i s  compare  variation  exploratory  asexually  p r o g r a m c a n n o t compare t h e v i r t u e s a n d c o s t s fixed  an  variation production  specified,  each  are  as  the  costs  production  variable  of  adjustable  and b e n e f i t s of  strategies.  names  and  In  are printed  program code they a r e lower  the  in capital  case.)  Var i a t i o n P r o d u c t i o n T h e r e a r e two p o s s i b l e strategy. The  One i s t h e p r o p o r t i o n  other  arbitrarily  vary only  a  f i x the  proportion  thirds)  The l a t t e r  and  i n the deviation  of  vary  are symmetrical  will  segment  be r e f e r r e d of  a  that  population  the  (undirected), offspring  offspring offspring bimodal, from the  c h a r a c t e r i s t i c of a  "step-size".  before  variant.  phenotypes.  variant  only  of the v a r i a n t  t o as i t s  production  are  offspring  p h e n o t y p e . The p a r t i c u l a r d e v i a t i o n  given player shows  to  ( a t two  distributions.  parental  of o f f s p r i n g  i s the d i s t r i b u t i o n of v a r i a n t  I t was d e c i d e d  and  components t o a v a r i a t i o n  Figure  8  ( a ) , and a f t e r (b)  120  P H E N O T Y P E  Figure  (p)  7. Reproduction of t h e p o r t i o n of the p o p u l a t i o n t h a t h a s a p h e n o t y p e o f '25'. T h i s p o p u l a t i o n h a s a s t e p - s i z e of 6. The o f f s p r i n g w i t h p h e n o t y p e '31' w i l l d i e w i t h o u t r e p r o d u c i n g i f t h e e n v i r o n m e n t r e m a i n s t h e same.  121  r e p r o d u c t i o n . V a r i a t i o n p r o d u c t i o n s t r a t e g i e s were  modelled  in  t h i s manner b e c a u s e of t h e p o t e n t i a l  f o r s t u d y i n g what t h e  offspring  I t s h o u l d be a c o m p o s i t e of  several of  distribution  should  s t e p - s i z e s d e p e n d e n t on t h e p r o b a b i l i t i e s of  the  environmental  lethality  of  of s l i g h t l y  modelled  e f f e c t s of m u t a t i o n s  is  of  very  variation  approximation  The  o t h e r s showed t h a t t h e d i s t r i b u t i o n  deleterious, neutral,  mode  i s bimodal.  and  One  mode i s t h a t  gives  a  reasonable  distribution.  environment  f u n c t i o n . The triangular determined  was  modelled  as  f o r m of t h e a d a p t i v e peak  (LINEAR)  or  PARABOLIC.  a  symmetrical  (PFORM) c a n  The  breadth  set  as  of t h e peak i s  units"  from the o p t i m a l phenotype  the n e a r e s t phenotype w i t h z e r o f i t n e s s . Narrowing t h e peak by d i m i n i s h i n g TOLRAD i n c r e a s e s t h e  o f v a r i a t i o n p r o d u c t i o n . The  a d a p t i v e PEAK c a n  the p e r m i s s i b l e range of 0 t o  relationship  between  e n v i r o n m e n t has o r may  be  fitness  by t h e v a r i a b l e TOLRAD ( " t o l e r a n c e r a d i u s " ) , w h i c h i s  the d i s t a n c e i n "phenotypic  over  The  Environment The  of  The  l e t h a l mutations.  strategy  The of  b e n e f i c i a l mutations.  d e l e t e r i o u s and  production  to t h i s  occurrence  c o n d i t i o n s f o r which each i s o p t i m a l .  work o f James (1959) and  other  be.  ideal  n o t be  PEAK  and  100 TIME  a c a r r y i n g c a p a c i t y (KK)  shared  by  the  breadth  immediate c o s t s  be moved a n y w h e r e  phenotypic can  to  be  which  units.  Any  specified.  The  may  the p o p u l a t i o n s i n a g i v e n  (ONEPOP:=1) run.  Dynamics Any  initial  frequency  d i s t r i b u t i o n may  be  specified  for a  122  p o p u l a t i o n , e i t h e r by e n t e r i n g i t anew, o r previously  stored d i s t r i b u t i o n . Reproduction  of  (discrete)  every  generation.  As  i n d i v i d u a l s of a g i v e n p h e n o t y p e may different  fitnesses  cumulative  e f f e c t s were i g n o r e d . The  to the next only  by  value  referring  (survival of  the  *  to  occurs at the  a  start  t h e a d a p t i v e peak moves, experience  d u r i n g a g e n e r a t i o n . For  generation  the  by  a  variety  simplicity,  of  these  c o n t r i b u t i o n of a p h e n o t y p e fecundity)  fitness  was  function  determined  at the time  of  r e p r o d u c t i o n . F i t n e s s i s a f u n c t i o n o n l y of p h e n o t y p e ,  and  of  adaptive  v a r i a t i o n p r o d u c t i o n scheme. P h e n o t y p e s o u t s i d e t h e  peak d i e w i t h o u t reproduce the  l e a v i n g progeny. Phenotypes underneath the  as p r e s c r i b e d by  the  population(s) relative  of g e n e r a t i o n s  not  t o be  run can  fitness  f u n c t i o n and  the s i z e  t o t h e c a r r y i n g c a p a c i t y . The be  peak of  number  specified.  Output The of t h e data  program r e q u e s t s a run d e s c r i p t i o n which  run summary p r i n t e d w i t h t h e o u t p u t . The  becomes  available  part output  are: 1. p o p u l a t i o n s i z e s o v e r  time,  2. mean  the  phenotypes  phenotype, over 3.  relative  of  populations,  average  fitnesses  (i.e. relative  f a c i l i t i e s are modularized  k i n d s o f d a t a may model  is  optimal  rates  of  so t h a t e a c h o f t h e  four  time,  4. mean s t e p - s i z e f o r a l l p o p u l a t i o n s o v e r output  the  time,  i n c r e a s e ) of t h e p o p u l a t i o n s o v e r  The  and  be  constructed  requested for  easy  separately. extension  and time.  Furthermore, of  runs  the  through  123  a d d i t i o n a l g e n e r a t i o n s . A f t e r s u c h a c o n t i n u a t i o n h a s been the  original  output  and t h e a d d i t i o n a l output  s e p a r a t e l y , or together. A l l output  c a n be  c o n s i s t s of  a  run,  requested  paired  data  t a b l e and p l o t .  Program Language This  model  i s a system of programs r u n n i n g  at t h e B i o s c i e n c e s Data C e n t r e , under  the  Berkeley  Berkeley  U n i v e r s i t y of B r i t i s h  UNIX V7 o p e r a t i n g  P a s c a l , t h e Bourne s h e l l ,  the program  on a PDP 11/45 Columbia,  system. I t i s w r i t t e n i n  a n d Awk. See  Figure  13 f o r  listings.  E x a m p l e Run Figure. entered  8 shows an e x a m p l e r u n o f t h e c o m p u t e r m o d e l .  by t h e u s e r a r e p r e f i x e d  PEAKGAME  was  called  in  order  with  an  to alter  PEAK, PFORM, TOLRAD o r ONEPOP. O t h e r w i s e , been  started  by  calling  GAME.  The  angle  changing  environment.  t h e model  of  the  offspring  production  greater  of  (Figure with  variation  variation  with  greater  peak. F o r  relative production.  production  The o u t p u t  of t h e  12.  populations  11)  strategies in a  change, a g r e a t e r  land outside the adaptive  generations correlated  r a t e of e n v i r o n m e n t a l  have  A l l p o p u l a t i o n s were s t a r t e d  i s p i c t u r e d i n F i g u r e s 9 through At t h i s  could  example r u n modelled t h e  w i t h t h e same s i z e and p h e n o t y p e d i s t r i b u t i o n . run  ">".  the specifications f o r  e f f e c t s of t h r e e d i f f e r e n t v a r i a t i o n p r o d u c t i o n constantly  bracket  Lines  tracked  fitness  the was  proportion variation first  four  negatively  The  populations  with  the  environment  more  124  closely  ( F i g u r e 10). A f t e r  f a r e d w o r s e , as measured relative  mean  fitness  greater variation  the f o u r t h g e n e r a t i o n , p o p u l a t i o n by  population  (Figure  p r o d u c t i o n . By  apparent  that  population  variation  p r o d u c t i o n , has  compromise f o r t h i s  "+", the  environment.  9)  and  11),  than the p o p u l a t i o n s  with  the  end  with best  size  an  of  (Figure  "X"  the  run  intermediate  it  is  r a t e of  "adaptedness/adaptability"  >peakgame e n t e r PEAK f u n c t i o n o f TIME, >peak:=30+2*time; to1rad:=10: off  t o l r a d , {pform, o n e p o p ) onepop:=1;  in  Pascal:  t o work... ( T h e p e a k d y n a m i c s a r e now w r i t t e n i n t o t h e p r o g r a m , and t h e p r o g r a m i s c o m p i l e d and r u n . The p r o g r a m b e g i n s : )  This  is  run i s a new run i s a c o n t i n u a t i o n of the l a s t ( d a t a i n f i l e pd) a c o n t i n u a t i o n o f some o t h e r r u n ( d a t a i n f i l e o t h e r t h a n pd) uses a stored player d i s t r i b u t i o n 1,2,3 o r 4:  Enter >4 W h i c h f i l e has t h e s t o r e d p l a y e r d i s t r i b u t i o n ? >di s t 7 E n t e r number o f p l a y e r s (< = 6) >3 E n t e r the s t e p - s i z e of piayer h 1: >2 player #2: >4 player #3: >7 Magic L i n e : p e a k : = 3 0 + 2 * t i m e ; t o l r a d : = 1 0 ; onepop:=1; W r i t e d e s c r i p t i o n of t h i s run: >constant r a t e of change Number o f g e n e r a t i o n s t o be r u n ? >20 players step-size 1 2 2 4 3 7 g e n e r a t i o n s : 0 t o 20 = 20 d e s c r i p t i o n : c o n s t a n t r a t e of Magic L i n e : peak:?30+2*time; tolrad:=10; Does e v e r y t h i n g >y  look  O.K.?  change onepop:=1;  (y/n)  ro  (population  sizes  are p r i n t e d at  >steplot 1 2 ( p r o d u c e s F i g u r e s 9 and >f1tnesses ( p r o d u c e s F i g u r e 11) >meanstep (produces Figure 12) END OF EXAMPLE RUN  10,  t h e end  of each  generation)  respectively)  ro Ch  step-size piayers 2 1 4 2 7 3 g e n e r a t 1 o n s : 0 t o 20 20 d e s c r i pt1 on: c o n s t a n t r a t e of Mag i c L i n e : peak:=30+2*t1me tolrad:=10; ECH0== > po i n t x : s t e p - s 1 z e o f 2 1 . 50.98 170.469 2 . 3 . 351.718 4. 407.523 5 . 396.209 6 . 363.758 7 . 318.968 8 . 270.765 9 . 222.921 177.914 10. 1 1 . 136.999 12 . 101.896 13 . 72.994 50.594 14 . 15 . 33.968 16 . 22.209 14.128 17 . 8.802 18 . 5. 369 19. 3 . 222 20. po 1 n t + : s t e p - s 1 z e o f 4 50.98 1. 153.557 2 . 3 . 290.326 315.935 4. 5 . 296.898 6 . 289.886 7 . 298.499 8 . 326.026 9. 365.152 4 14.908 10. 1 1 . 463.65 513.459 12 . 13 . 552.504 14 . 588.925 15 . 614.211 16 . 6 3 9 . 8 5 5 17 . 653.794 18 . 670.905 19 . 679.037 692.164 20.  point  point point point  change 700-  ^  B30-  ..  onepop:=1;  rt:step-sizeof7 1. 50.98 2. 1 19. 126 3 . 181 .851 4 . 169 .067 5 . 141 .474 6 . 126 .307 7 . 1 19 .704 8 . 120. 448 9 . 125. 323 10. 131 . 2 1 1 . 134 .552 12. 136 .963 13. 136 .863 14 . 133 .451 15 . 128 . 77 16 . 124 . 233 17 . 1 18 . 47 18. 1 1 1.934 19. 105 .85 20. 100 .546  5E0  490  CD  450  111  Ld CD •>  3 SO  ZD EBO  210  x:20 x y p a i r s : s t e p - s i z e o f 2 +:20 x y pa 1 r s : s t e p - s i z e o f 4 r t : 2 0 xy p a i r s : s t e p - s i z e o f 7  14070 >  B-  10>  IE •  GENERATIONS  F i g u r e 9. time.  S i m u l a t i o n model o u t p u t : Command: s t e p l o t  1.  population sizes  over  14-  IE-  IB-  players step-size 1 2 2 4 3 7 generations: 0 t o 20 = 20 d e s c r i p t i o n : c o n s t a n t r a t e of change Magic Line: p e a k : = 3 0 + 2 * t i m e : t o l r a d : = 1 0 ; onepop:=1;  EO-  :DATA point  18-  ECH0= np: 1 . 30 32 2 . 34 3 . 36 4. 38 5 . 6. 40 42 7. 44 8 . 46 9. 48 10. 11 . 50 52 12 . 54 13 . 14 . 56 58 15. 60 16. 62 17 . 64 18 . 66 19. 68 20. po i n t x s t e p - s i z e o £ 2 1 . 30 2 . 30 796 3. 31 687 32 345 4 . 33 268 5. 34 603 6. 36 205 7. 37 961 8. 39 792 9. 4 1 659 10. 43 535 11. 45 421 12. 47 308 13. 49 205 14. 51 109 15. 53 026 16. 54 948 17. 56 883 18. 58 823 19. 60 773 20.  point  point  point point point point  +:step-sizeof4 1 30 31 064 2 . 32 396 3 . 33 702 4 . 35 339 5. 37 216 6 . 39 224 7 . 41 233 8 . 43 276 9. 45 263 10. 47 27 11 . 49 228 12 . 51 219 13 . 53 169 14 . 55 166 15 . 57 126 16 . 59 129 17 . 61 094 18 . 63 106 19 . 65 078 20. r t: step-stzeof7 1 30 2 . 31 626 33 44 1 3 . 4 . 35 244 37 14 5. 39 086 6 . 41 128 7 . 43 192 8 . 45 21 1 9. 47 186 10. 49 201 11 . 51 201 12 . 53 149 13 . 14 . 55 158 57 186 15 . 16. 59 182 61 14 17 . 63 156 18 . 65 16 19. 67 1 16 20.  1G14 • D  la-  -<  ic-  UJ LLJ LD  np:20 xy p a i r s : x:20 xy pairs:step-s1zeof2 + : 20 xy p a i r s : s t e p - s i z e o f 4 r t : 2 0 xy p a i r s : s t e p - s i z e o f 7  Figure 10. Simulation model output: average phenotypes over time. Command: s t e p l o t 2.  ro CO  DATA point  ECHO==> x 1. 2 . 3 . 4. 5. 6 . 7 . 8. 9 . 10. 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 .  1 . 1 . 1 . 1 . .940304 .851567 .777206 .735084 .702394 .689079 .671621 .665733 .65026 .643744 .6276 18 .622576 .607 128 ..60267 .588731  1 . 2 . 3 . 4. 5 . 6 . 7 . 8 . 9 . 10. 11 . 12 . 13. 14 . 15 . 16 . 17 . 18 . 19 .  .900791 .916362 .939192 .966579 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 . 1 .  po i nt  point point point point  rt : 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8. 9 . 10. 11 . 12 . 13. 14 . 15 . 16 . 17 . 18 . 19.  i-o .698813 .739878 .80239 .860688 .914389 .920377 .921259 .928987 .921351 .917736 .919174 .928652 .914769 .925199 .926101 .93328 .920733 .934322 .931877  0-9  LO  CO Ld  0-B 0-7 0-B  LiJ  0.3 .. LJJ  0-4  x:19 xy p a l r s : +:19 xy p a i r s : r t : 1 9 xy p a i r s :  LxJ  o-a D-l  0-1  0-0  B-  IO-  IE-  GENERATIONS Figure  11. S i m u l a t i o n model o u t p u t : r e l a t i v e a v e r a g e fitnesses over time. Command: f i t n e s s e s .  14-  IB-  IB"  c!0.  5-0 4-5 .. DATA  ECH0==>  point  x: 1 . 2 . 3 . 4. 5 . 6 . 7 . 8 . 9 . 10. 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 . 20.  point  x:20 xy  4-0 .. 33333 0371 80837 65509 55906 55306 62176 74878 90206 05217 17636 27528 34708 38703 40977 4 175 4 1602 40195 38824 37088  M 1—1 cn  M  \  x x x x x-.x  3-5 3-0 ..  I  CL UJ I—  2-5 -.  LO  5-0 -.  1-5 1-0 .  pairs:  0-5 ..  B•  10 •  IE-  14-  IB-  IB. tlD-  GENERATIONS Figure  1 2 . S i m u l a t i o n model o u t p u t : a v e r a g e over time. Command: m e a n s t e p .  "step-sizes"  £ °  Figure  13. The  s imu1 a t i o n model  program  1i s t i n g s .  PEAKGAME v7=yes echo e n t e r PEAK f u n c t i o n o f TIME, r e a d m l i ne echo o f f t o work. . . ' >&2 c a t <<+ >sgame.p  tolrad,  {pform,  onepop)  in Pascal:'  >&2  (* e n d o f S h e l l , s t a r t o f P a s c a l *) program stepgame ( 1 n p u t , o u t p u t , d a t a , s t o r e , r 1 , r2); l a b e l 13; const f u z z = 1.Oe-10: minp= 0; maxp= 100: p l a y e r s = 6; (* c o n s t r a i n e d b y p l o t s y m b o l s *) 1 1 n e l e n = 128; b1ank= ' ' ; maxr= 0.5; kk = 1000; type s t r i n g = a r r a y t 1 •1inelen] of char; fname = a r r a y [ 1 . . 1 4 ] o f c h a r ; var f l a g 1 , f l a g 2 : boolean; cho1ce,i,j,k,maxtIme,new,old,p,s,ss,maxss,playin,t1nc,t1me: i nteger; p f o r m , 1 i n e a r , p a r a b o l i c , o n e p o p , 1 o w p , h i g h p , p r e v l o w , p r e v h i gh: i n t e g e r ; k i ds,pav,peak,prop,r,1ambda,tolrad,totnum: rea 1 ; letter: char; step: a r r a y [ 1 . . p i a y e r s ] of integer; 1 astnum.num,sum: a r r a y [ 1 . . p i a y e r s ] o f r e a l ; p o p : a r r a y [ 1 . .2 , 1 . . p i a y e r s , m 1 n p . . m a x p ] o f r e a l ; lab: a r r a y [ 1 . . p i a y e r s ] of char; e x t i n c t : a r r a y [ 1 . . p i a y e r s ] of boolean; b l u r b , f 1 : s t r i ng; d a t a , s t o r e , r 1 ,r2 : t e x t ; f n : fname;  ttinclude  "strings.!"  (* ========== *) procedure var special: beg i n spec i a l [ 1 ] : spec1al[4]: d o i t:= 0;  setup(f:fname); doit.i: integer; a r r a y ! 1 . . 6 ] of char; = ' o ' ; s p e c i a 1 [ 2 ] : = ' u ' ; s p e c i a 1 [ 3] : = ' t ' = ' p ' ; s p e c i a l [ 5 ] : = 'u';spec i a l [ 6 ] : = ' t '  to  f o r i : = 1 t o 6 do I f s p e c i a l [ i ] < > f [ 1 ] t h e n d o i t : = do1t+ 1; i f doit>0 then r e w r i t e ( o u t p u t , f ) ; wr i t e l n ( o u t p u t ) ; writeln(output, ' players step-size'); f o r 1: = 1 t o p l a y i n do w r i t e l n ( o u t p u t , 1 . s t e p [ i ] ) ; wr 1 t e l n f o u t p u t , ' g e n e r a t i o n s : ' , t i m e : 1 , ' t o ',maxtime: 1, = ',maxt1 me-1ime: 1 ) ; wr1te(output,'description: ' ) ; putstr(output,blurb,'1'); wr1te1n(output,'Magic Line:'); w r 1 t e l n ( o u t p u t , ' $ml1ne ' ) ; writeln(output); rewr i t e ( o u t p u t , ' / d e v / t t y ' ) ; end;  (* ========== *) procedure saveprop(sfn:fname); var s,p:i nteger; begin rewrit°(store,5fn); wr1teln(store,time,play1n); f o r s:=1 t o p l a y i n do w r 1 t e ( s t o r e , s t e p [ s ] ) ; w r 1 t e l n ( s t o r e ) ; f o r s:=1 t o p l a y i n d o beg i n f o r p:=minp t o maxp do w r i t e 1 n ( s t o r e , p o p [ o l d , s , p ] : 1 : 5 ) : wr i t e l n ( s t o r e , 1 a s t n u m f s ] : 2 0 ) ; end; end; (* s a v e p r o p *)  (* ========== *)  procedure readprop(fn:fname;switch:1nteger) ; (* s w i t c h : 0 read only the p l a y e r d i s t r i b u t i o n (* 1 r e a d p l a y e r d i s t r i b u t i o n and time and a p l a y e r s var temp:real; begi n reset(data,fn); if not eof(data) t h e n i f s w i t c h <>0 then begin readln(data,time,play1n); f o r s:=1 t o p l a y i n do r e a d ( d a t a , s t e p [ s ] ) ; readln(data); end else begin readln(data); readln(data); end e l s e w r 1 t e l n ( ' D u m m y T h e f i l e i s empty. ' ) ; temp:= 0; f o r s:=1 t o p l a y i n d o beg i n  *) *)  00  ro  for  p:== m i np t o maxp do If n o t e o f ( d a t a ) then begin readln(data,pop[old,s,p]); temp:= temp+ p o p [ o l d , s , p ] ; end e l s e wr 1 t e l n ( ' E r r o r . F i l e r a n o u t a t P= ' , p ) : readln(data, 1astnum[s]); i f abs(temp- 1 a s t n u m [ s ] ) > f u z z then beg i n w r 1 t e l n ( E r r o r . P l a y e r t o t a l r e a d i n does not match t h a t w r 1 t e l n ( temp= ',temp) wr1teln( lastnum[s]= 1astnumt s ] ) ; end; temp:= 0; end; end; (* r e a d p r o p  beg i n ( *'. i n i t i a l i z a t i o n s  stored.');  *)  t i m e : = 0; p f o r m : = 0; 1 I n e a r : = O; p a r a b o l i c : 1; (* dummies, w o u l d p r o p e r l y make a TYPE * o n e p o p : = 0; (* 0 means t h e y a r e i n d e p e n d e n t subpopu1 a t i o n s *) ( * m1i ne a s s i g n s p e a k f u n c t i o n , f o r m , and t o l e r a n c e r a d i u s , and d e t $ m l i ne o l d : = 1; new:= 2 ; totnum:= 0: maxss:= 0; p r e v l o w : = m i np; p r e v h i g h : = maxp; 1  f lag1 = f a l s e ; f lag2 = f a l s e ; f o r i =1 t o 14 do writeln; wr1teln( wr i t e l n ( wr i t e l n ( wr1teln( wr1teln( wr i t e 1 n ( read(choi case  fn[1]:  whether p l a y e r s  share  carrying capacity  kk  *)  blank;  wr i t e l n ; Th i s r u n ' ) ;  is Enter ce ) ;  c h o i c e of 1: f l a g 2 : =  1 s a new r u n -i s a c o n t i n u a t i o n o f t h e l a s t ( d a t a i n f i l e pd) -a c o n t i n u a t i o n o f some o t h e r r u n ( d a t a i n f i l e o t h e r t h a n pd) -u s e s a s t o r e d p l a y e r d i s t r i b u t i o n -1,2,3 o r 4: ' ) ;  true;  1' ) 2') 3) 4)  LO CO  2: b e g i n f1[1]:= p'; f1[2]:= ' c f ; f.lagl : = t r u e ; end; 3: b e g i n w r i t e l n ( ' E n t e r name o f f i l e where d a t a i s s t o r e d : ' ) ; g e t s t r ( i n p u t , f 1 , 'w'); flag1:= true; end ; 4: b e g i n writeln('Which f i l e has t h e s t o r e d p l a y e r d i s t r i b u t i o n ? g e t s t r ( i n p u t , f 1 , ' w' );flag1:= true; f1ag2:= t r u e ; end; end; (* f l a g l (* f l a g 2 if  flag2 then  => i s n o t a new r u n , s t o r e d p l a y e r d i s t r i b u t i o n => n e e d p r o m p t i n g f o r p l a y e r s a n d s t e p - s i z e  begin w r i t e l n ( ' E n t e r number o f p l a y e r s (<=6) r e a d l n ; read(p1 a y i n ) ; w r i t e l n ( ' E n t e r the s t e p - s i z e o f ' ) ; f o r 1:=1 t o p l a y i n do begin wr1teln('piayer #',1:1,':'); readln; r e a d ( s t e p [ i ] ) ; end; end; o  for  j:=1 t o p l a y i n do begi n l a s t n u m [ j ] : = 0; num[j ] := 0; s u m [ j ] : = 0; f o r i:=1 t o 2 d o f o r k:=minp  t o maxp do p o p [ i , j . k ] : =  0;  end; 1: =1 ; while (f1[1]<>blank)and(f1[1]<>'"')and(1<=14) beg i n fn[i]:= f1[1]; i : =i+1 ; end; 1f f l a g l then begin i f f l a g 2 then readprop(fn,0)  do  '):  * *  else „  else  1f  flag2  begin readprop(fn,1); r e w r i t e ( r 1 , ' r e s 1'); rewrite(r2,'res2') end; t o p l a y i n do totnum:= totnum+  f o r s:=1 lastnum[s]; end begin wr i t e l n ; wr1teln('The i n i t i a l t o l e r a n c e r a n g e 1s b e t w e e n p h e n o t y p e s wr i t e 1 n ; wr i t e l n( ' E n t e r : p l a y e r ft, p h e n o t y p e , numbers ' ) ; w r i t e l n ( ' ( 0 f o r p l a y e r H when d o n e ) ' ) : r e a d l n ; r e a d ( s , p , p r o p ); w h i 1 e s<>0 do beg 1 n pop[old,s,p]:= prop; (* i f any s,p i s u s e d more totnum:= totnum+ p r o p ; 1astnum[s]:= lastnum[s]+ prop; sum[s]:= sum[s]+ prop*p; readln; read(s,p,prop); end; end;  ,peak-tolrad:1,'  an  once,  totals  and  will  ',peak+tolrad:1);  be wrong  *)  then begin rewrite(r1, 'results1'); rewr1te(r2, 'results2'); end;  wr1teln; w r i t e l n ( Magic L i n e : ' ) ; wr1teln(' $mline ' ) ; wr1teln('Write d e s c r i p t i o n of t h i s run:'); readln: getstr(i nput.blurb.'l); w r i t e 1 n ( ' N u m b e r o f g e n e r a t i o n s t o be r u n ? ' ) ; readln; read(tinc); (* m i g h t n o t n e e d t h e r e a d l n h e r e maxtime:= time+tinc; setup('/dev/tty'); w r i t e l n ( ' D o e s e v e r y t h i n g l o o k O.K.? (y/n)'); readln; read(1etter); i f l e t t e r = ' n ' t h e n g o t o 13;  setup('setup'); lab[1]:= x lab[2]:='+'; 1ab[3] lab[4]:='1 lab[5]:='u'; lab[6] wr1te1n(r1 i?l a b e l =on' ); wr i t e 1 n ( r 1 ®>x 1 ab= " g e n e r a t i o n s " wr i t e l n ( r 1 @ylab="numbers" ' ) ; wr1teln(r2 <al a b e l =on' );  *)  co cn  wr 1 t e l n( r 2 , '<s>xl ab= " p h e n o t y p e " ' ); wr 1 t e l n( r 2 , '<»y 1 ab = " g e n e r a t 1 o n s " ' ) ; w r 1 t e l n ( r 2 . ' @ y s o r t ' ); f o r i : = 1 t o p l a y i n do (* u s e f u l f o r d a t a e c h o o n l y -- d o e s n ' t a p p e a r o n p l o t s *) begi n i f l a s t n u m [ i ] > 0 then e x t i n c t [ i ] : = f a l s e e l s e e x t i n c t [ 1 ] : = true; i f s t e p f i ] > m a x s s t h e n tnaxss : = s t e p [ i ] ; wr i t e l n ( r 1 , @ p t 1 1 1 e = ' , 1 a b [ 1 ] , ' : s t e p - s i z e _ o f _ ' , s t e p f i]:1); w r i t e l n ( r 2 , ' @>pt i 11 e = ' , l a b [ 1 ] , ' : s t e p - s i z e _ o f _ ' , s t e p f i ] : 1 ) ; if not f l a g l then begi n w r i t e l n ( r 1 , l a b f 1 ] , t ime,' ',lastnumf1]:1:3); writeln(r2,labf i],(sumfi]/lastnum[i]):1:3, ' ' ,time): sumt1]:= 0; end; end; (* t h e p e r - g e n e r a t i o n s t u f f ================================================ *) w h i l e time<maxtime do beg i n $m1ine (* p e a k a s a f u n c t i o n o f t i m e *) lowp:= round(peak-tolrad+O.5); highp:= round(peak+tolrad-O.5); i f lowp<minp t h e n lowp:= minp; (* a l l o w s peak t o s t a r t w i t h p a r t o f i t s *) i f highp>maxp t h e n h i g h p : = maxp; (* e n t i r e t o l e r a n c e r a n g e o u t s i d e minp-maxp *) i f p r e v 1 o w < l o w p t h e n lowp:= p r e v l o w ; i f p r e v h i g h > h i g h p then highp:= p r e v h i g h ; f o r s:=1 t o p l a y i n d o i f n o t e x t 1 n c t ( s ] t h e n f o r p:= lowp t o h i g h p do begi n i f pform=parabolic then lambda:= 1 - s q r ( ( p - p e a k ) / t o l r a d ) (* p a r a b o l i c f n o f d i s t t o peak *) else lambda:= 1-abs(p-peak ) / t o l r a d ; (* f u n c t i o n o f d i s t a n c e f r o m peak *) i f lambda<0 t h e n lambda:= 0; i f onepop=0 (* e f f e c t s o f *) t h e n k i d s : = p o p f o l d , s , p ] * 1ambda*(1+maxr*(1- 1 a s t n u m f s ] / k k ) ) / 3 (* i n d e p e n d e n t c r o w d i n g e l s e k i d s : = p o p f o l d , s , p ] * 1ambda*(1+maxr*(1 - t o t n u m / k k ) ) / 3 ; (* j o i n t c r o w d i n g *) ss:= s t e p [ s ] ; popfnew,s,p]:= poptnew,s.p]+ k i d s ; n u m [ s ] : = num[s]+ k i d s ; s u m [ s ] : = sum[s]+ k i d s * p ; i f (p+ss)<=maxp t h e n begin pop[new,s,p+ss]:= poptnew,s,p+ss]+ k i d s ; num[s]:= num[s]+ k i d s ; sum[s]:= sum[s]+ k i d s * ( p + s s ) ; end; i f (p-ss)>=minp then begi n popfnew,s,p-ss]:= pop[new,s,p-ss]+ k i d s ; num[s]:= num[s]+ k i d s ;  *)  £J o>  sum[s]:= sum[s]+ k 1 d s * ( p - s s ) ; end; p o p f o l d , s , p ] : = 0; p r e v l o w : = r o u n d ( p e a k - t o l r a d + 0 . 5 ) - maxss; i f p r e v l o w < m i n p t h e n prev1ow:=minp; prevhigh:= round(peak+tolrad-0.5)+ maxss; i f prevh1gh>maxp t h e n p r e v h i g h : = m a x p ; end; t i m e : = t i m e + 1; (* o u t p u t a n d p l o t g e n e r a t i o n s t u f f . c l e a r sum a n d num *) w r i t e l n ( r 2 , 'n',peak:1:3,t ime); (* t i m e i s number o f g e n e r a t i o n s g o n e *) (* r e a d o u t i s s t a t e a t t h e e n d o f t i m e t h g e n e r a t i o n *) wr1teln(output); w r i t e l n ( o u t p u t , ' *** ' . t i m e ) ; totnum:= 0; f o r i:=1 t o p l a y i n d o beg 1 n write(output,num[i]:1:3, ' ) ; i f (num[i]=0) and (not e x t i n c t [ i ] ) then begl n w r i t e l n ( ' P l a y e r ' , i , ' h a s gone e x t i n c t . T i m e : ' . t i m e ) ; ext i n e t [ i ] : = true; end; writeln(r1,lab[i],time,' ',num[11:1:3); i f n u m [ i ] = 0 t h e n pav:=0 e l s e pav:= s u m [ i ] / n u m [ i ] ; wr 1 t e l n ( r 2 , 1 a b [ i ] , p a v : 1 : 3 , ' ' . t i m e ) ; (* e x t i n c t p l a y e r s w i l l h a v e p h e n o t y p e z e r o totnum:= totnum+ n u m [ i ] ; lastnum[i]:= num[i]; num[i]:=0; s u m [ i ] :=0; end: o l d : = new; new:= 3 - o l d ; end; (* e n d w h i 1 e * )  *)  saveprop('pd'); 13: e n d . + : end of P a s c a l , r e s t a r t pi sgame.p mv o b j game game  of Shell  co —i  AUXILIARY ********** v7=yes  steplot  p a r [par2  par3  PROGRAMS  ...]  :Explanation of parameters: 1 p l o t s p o p u l a t i o n s i z e s versus generations of the o r i g i n a l run 2 p l o t s average phenotypes over generations f o r o r i g i n a l run 3 does 1 f o r c o n t i n u a t i o n r u n 4 does 2 f o r c o n t i n u a t i o n r u n 5 does 1 f o r o r i g i n a l and c o n t i n u a t i o n runs t o g e t h e r 6 does 2 f o r o r i g i n a l and c o n t i n u a t i o n runs t o g e t h e r P r i o r t o a second c o n t i n u a t i o n run, and each subsequent c o n t i n u a t i o n r u n , t h e c o n t i n u a t i o n d a t a must b e a p p e n d e d t o t h e o r i g i n a l d a t a by i s s u i n g t h e command " t a c k " , b e c a u s e o n l y o n e s e t o f c o n t i n u a t i o n d a t a 1s m a i n t a i n e d at any time. cat cat  resultsl results2  for do  1 in  case $ i 1) ( c a t 2) ( c a t 3) ( c a t 4) ( c a t 5) g r e p (cat 6) g r e p (cat *) e c h o esac cat cat  > >  rl.plot r2.plot  in s e t u p ; q p l o t - j o i n r1 . p l o t ) wrap setup; qplot -join r 2 . p l o t ) wrap setup; qplot s e t u p ; q p l o t - j o i n r e s 2 ) | wrap 42 -v <a r e s 1 \ c a t >> r l . p l o t setup; qplot - j o i n r l . p l o t ) wrap -v @ r e s 2 \ c a t >> r 2 . p l o t setup; qplot - j o i n r 2 . p l o t ) wrap $i i s a wierd parameter  resultsl results2  > >  42 42  pr pr p r -3 p r -3  -3 -3  42  pr  -3  42  pr  \  1 pr; lpr; 1 pr; ; 1 pr; ; lpr; ; lpr; ;  rl.plot r2.plot  done  ********** v7=yes : uses : plot  fitnesses  peakgame o u t p u t f i l e r e s u l t s l r e l a t i v e f i t n e s s e s over time  c a t <<+ > f 1 t . p i o t ipxl ab= " g e n e r a t i o n s " @ y 1 a b = " r e 1 a t i v e mean P1abe1=on  fitness"  t o c a l c u l a t e and  co  00  ©join + awk - f f i t a w k . a r e s u l t s l qplot  fit.plot  >>  fit.plot  | wrap 42 f p r -3 J I p r  ********** meanstep v7=yes : u s e s peakgame o u t p u t f i l e r e s u l t s l t o c a l c u l a t e the average s t e p s i z e f o r each g e n e r a t i o n .  and p l o t  c a t <<+ > m s t e p . p l o t @>y 1 ab= "mean s t e p - s i z e " @xlab="generat ions" @j o i n  awk - f a v s t e p . a r e s u l t s l > > m s t e p . p l o t q p l o t m s t e p . p l o t / wrap 42 / p r -3 / l p r  ********** f i t a w k . a BEGIN { l a s t = 1 . ; sum=0. NF==3. &&  $2 = l a s t  ; flag=0.  ; maxf=  0.)  {for(i  i n num) { p r o p [ i ] = num[1]/sum i f ( f l a g = 0 . && p r e v [ 1 ] = 0 . ) f a b s [ 1 ] = p r o p [ i ] / p r e v [ 1 } e l s e f a b s [ i ] = 0. i f ( f a b s [ i ] > m a x f ) maxf= f a b s t i ] prevf i]=prop[i] } if (flag=0.) f o r ( i i n fabs) print sym[i], last-1., fabs[i]/maxf maxf= 0. l a s t = $2 sum= 0. f l a g = 1. >  NF==3. && END  $2==1ast  {sym[$1]=$1; num[$1]=$3;  sum += $3}  {for(i  if  i n num) { p r o p [ i ] = num[i]/sum if (flag=0. prev[l]=0.) fabs[i]= prop[i]/prev[i] e l s e f a b s f i ] = 0. i f ( f a b s [ i ] > m a x f ) maxf= f a b s [ i ] p r e v [ i ] =prop[i] ) (flag=0.) f o r ( i i n fabs) print sym[i], last-1., fabs[i]/maxf  CO to  } ********** BEGIN  avstep.a  (flag=0.)  NF==1.  { i f (1ndex($1,":") = 0.){ s= i n d e x ( $ 1 , " = " ) step[substr($1,s+1..1.)]= >  NF==3. &&  flag==0.  < flag=1.;  substr($1,1ength($1),1.)  last=$2  }  NF==3. SS $2 = l a s t  { f o r ( i i n p r o d ) sum+ = print 1ast,sum/cnt cnt=0. sum=0. last=$2 }  prod[1]  NF==3. &S $2 = = l a s t  {sym[$1]=$1;  * s t e p [ $ 1 ] ; c n t + = $3}  END  prod[$1J=$3  { f o r ( i i n p r o d ) sum+= p r o d f l ] ;  **********  print  last,  sum/cnt)  tack  v7=yes :appends c o n t i n u a t i o n d a t a : c o n t i n u a t i o n runs. grep grep  -v -v  @ r e s 1 ] c a t >> @ r e s 2 \ c a t >>  to original  resultsl results2  run data,  for additional  

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