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Breeding system, genetic variability, and response to selection in Plectritis (Valerianaceae) Carey, Charles Kenneth 1981

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BREEDING SYSTEM, GENETIC VARIABILITY, AND RESPONSE TO SELECTION IN PLECTRITIS  (VALERIANACEAE)  by CHARLES KENNETH CAREY B.Sc.,.The U n i v e r s i t y o f B r i t i s h Columbia, 1976  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  in THE FACULTY OF GRADUATE STUDIES (Department o f Botany)  We a c c e p t t h i s  t h e s i s as conforming .  to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA April,  (c)  1981 -  C h a r l e s Kenneth Carey, 1981  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t  the L i b r a r y s h a l l make  it  and study.  f r e e l y a v a i l a b l e f o r reference  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s .  Iti s  understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l n o t be allowed without my  permission.  Department o f  Botany  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date  July 20, 1981  Columbia  written  - i i Abstract  P l e c t r i t i s congesta  and P. brachystemon a r e two v e r y c l o s e l y  s p e c i e s which grow s y m p a t r l c a l l y , and d i f f e r i n t h e i r b r e e d i n g :  related  system, some  a s s o c i a t e d m o r p h o l o g i c a l . ( f l o r a l ) c h a r a c t e r s , and isozyme phenotypes. congesta is  i s approximately  70% o u t c r o s s e d  l e s s than 3% o u t c r o s s e d  Plectritis  i n n a t u r e , w h i l e P. brachystemon  i n natural populations.  Theory would p r e d i c t  t h a t , a l l o t h e r t h i n g s b e i n g e q u a l , the o u t c r o s s e d  s p e c i e s would be more  v a r i a b l e g e n e t i c a l l y than t h e s e l f e d s p e c i e s .  S i n c e s e l e c t i o n a c t s on  g e n e t i c v a r i a b i l i t y , the two s p e c i e s c o u l d be expected to i t .  S i x generations  t o respond  of p l a n t s o f both s p e c i e s were grown under c o n t r o l l e d  c o n d i t i o n s , and measured f o r a number o f c h a r a c t e r s .  C o n t r o l and  ( s e l e c t i o n f o r t a l l and s h o r t h e i g h t , and f o r e a r l y and l a t e p o p u l a t i o n s were m a i n t a i n e d . maintained,  differently  one o u t c r o s s e d  Two s e t s o f P. congesta (approximately  treatment  anthesis)  p o p u l a t i o n s were  65%) and one s e l f e d  (outcrossed  approximately  1 5 % ) ; the P^ brachystemon p o p u l a t i o n s were n a t u r a l l y s e l f -  pollinating.  S e l e c t i o n p r e s s u r e i n t h e experiment was approximately  90%;  20 of t h e 200 p l a n t s i n any p o p u l a t i o n were s e l e c t e d t o form t h e next  -  g e n e r a t i o n , on the b a s i s o f h e i g h t o r f l o w e r i n g time i n t h e treatment p o p u l a t i o n s , and a t random i n the c o n t r o l p o p u l a t i o n s . The P^ congesta  p o p u l a t i o n s responded t o d i v e r g e n t s e l e c t i o n f o r h e i g h t  at a n t h e s i s , i n d i c a t i n g t h a t g e n e t i c v a r i a b i l i t y present 148 mm  i n the p o p u l a t i o n s .  The o u t c r o s s e d  f o r t h i s c h a r a c t e r was  l i n e s , PCO, d i v e r g e d 66% or  from the c o n t r o l l i n e ; t h e s e l f e d l i n e s , PCS, d i v e r g e d  There were no s i g n i f i c a n t d i f f e r e n c e s between t h e o u t c r o s s e d P. congesta  l i n e s over the course o f the experiment.  narrow sense h e r i t a b i l i t y - r e a l i s e d h e r i t a b i l i t y regression  78% o r 175  mm.  and s e l f e d  Two e s t i m a t e s o f  (b^) and p a r e n t - o f f s p r i n g  2 (h ) - q u a n t i f i e d t h i s g e n e t i c v a r i a b i l i t y :  : i n PCO b^ = 0.53,  h  2  = 0.45:  i n PCS  phenotypic  b  c  = 0.58,  2  h  = 0.44.  There was  iii  a d e c l i n e i n the  v a r i a n c e f o r h e i g h t at a n t h e s i s i n the 'P_ corigesta l i n e s  selected for this character.  In c o n t r a s t , the P. brachystemon  d i d not respond t o s e l e c t i o n f o r h e i g h t at a n t h e s i s , and  populations  appear t o have  no d e t e c t a b l e g e n e t i c v a r i a b i l i t y f o r t h i s c h a r a c t e r . Both s p e c i e s appear to have s i g n i f i c a n t g e n e t i c v a r i a b i l i t y  for  f l o w e r i n g time, as both responded to d i v e r g e n t s e l e c t i o n f o r t h i s The  PCO  l i n e s d i v e r g e d 33.5%  l i n e s d i v e r g e d 28.7%  or 31.8  or 27.3  days from the c o n t r o l l i n e , the  days, and  18.5%  congesta  i s more v a r i a b l e g e n e t i c a l l y : i n the PCO  was  b  c  = 0.75,  '  h  2  days.  = 0.72;  According  to the h e r i t a b i l i t y e s t i m a t e s ,  w h i l e i n PBS  a d e c l i n e i n the phenotypic  PCS  the P. brachystemon lines>"PBS,-  diverged  i n PCS  or 21.5  character.  b  c  lines b  = 0.49,  =0.77, h  c  and h  2  2  = 0.42.  P. =  0.60;  There  v a r i a n c e f o r f l o w e r i n g time i n a l l t h r e e  s p e c i e s groups. Of the o t h e r measured but u n s e l e c t e d c h a r a c t e r s - number of days to emergence, number of nodes at a n t h e s i s , number of primary a n t h e s i s , and  f r u i t p r o d u c t i o n - some responded to the s e l e c t i o n  with divergence,  With o t h e r s t h e r e was  a t t r i b u t e d to the s e l e c t i o n  selection;  no evidence  i n aberrant  change which c o u l d  from two  d i s p e r s i o n i n both to r e s u l t  q u a l i t a t i v e c h a r a c t e r s - f r u i t wing  c h a r a c t e r s was  congesta  response to  not s i g n i f i c a n t l y  from random d r i f t .  c h a r a c t e r s i n the P.  o u t c r o s s e d P.  be  procedure.  brachystemon l i n e s i s p r o b a b l y normally  no  f r u i t pubescence p a t t e r n phenotype - f o r any  from t h a t expected  the  ( f o r example, number of nodes at a n t h e s i s , c o r r e l a t e d  with flowering time).  phenotype and  pressure  n o t a b l y those c h a r a c t e r s which were c o r r e l a t e d w i t h  selected characters  There was  branches at  The  different  r e l a t i v e l y high increase  l i n e s compared to the  P.  i n d i c a t i v e of i n b r e e d i n g d e p r e s s i o n  congesta.  <•,.'  i n the  - iv I t appears t h a t d e s p i t e the d i f f e r e n c e i n b r e e d i n g  system, the two  P l e c t r i t i s s p e c i e s a r e a b l e to m a i n t a i n v a r i a b i l i t y by s i m i l a r  processes  ( g e n e t i c ) i n some c h a r a c t e r s , as i n f l o w e r i n g time, and by d i f f e r e n t processes  ( g e n e t i c i n P. congesta,  phenotypic  i n P_. brachystemon) i n o t h e r  c h a r a c t e r s , as i n h e i g h t a t a n t h e s i s . Thus one q u a n t i t a t i v e c h a r a c t e r , h e i g h t a t a n t h e s i s , f o l l o w s the p a t t e r n p r e d i c t e d by the b r e e d i n g  system d i f f e r e n c e , w i t h the o u t c r o s s e d P.  b e i n g much more v a r i a b l e g e n e t i c a l l y than  the s e l f e d P_ brachystemon.  T h i s agrees w i t h the l e v e l s o f v a r i a b i l i t y  observed  by Layton  e l e c t r o p h o r e t i c a l l y d e t e c t a b l e isozymes, and observed (unpublished) The  i n metrical fruit  congesta  (1980) i n  by Ganders and Maze  characters.  other q u a n t i t a t i v e c h a r a c t e r , f l o w e r i n g time, shows c o n s i d e r a b l e  g e n e t i c v a r i a n c e i n the p o p u l a t i o n s o f the s e l f e d P^ brachystemon, though l e s s than i n the p o p u l a t i o n s o f P_ congesta. relatively  The maintenance o f such  h i g h l e v e l s o f g e n e t i c v a r i a b i l i t y i n the f a c e o f the s t r o n g  i n b r e e d i n g p r e s s u r e s which must be p r e s e n t i s c e r t a i n l y a d a p t i v e , and p r o b a b l y  i n P_^_ brachystemon p o p u l a t i o n s  comes about through o c c a s i o n a l  o u t c r o s s i n g and m u l t i n i c h e s e l e c t i o n f o r v a r i a b i l i t y lines.  among the s e g r e g a t i n g  -  T a b l e of  Contents  Abstract  i i  L i s t of Tables  x  L i s t of F i g u r e s  xi  Acknowledgements  xv  Introduction  1  B r e e d i n g system and g e n e t i c v a r i a b i l i t y  2  Theoretical considerations  2  E x p e r i m e n t a l evidence  .....  6  Monogenic t r a i t s  7  Quantitative t r a i t s  9  Genetic v a r i a b i l i t y  and  the response  to s e l e c t i o n  .....  12  Theoretical considerations  12  E x p e r i m e n t a l evidence  14  B r e e d i n g system and  the response  to s e l e c t i o n  16  Theoretical considerations  16  Experimental evidence  17  Outcrossed taxa  18  I n b r e e d i n g taxa B r e e d i n g system, g e n e t i c v a r i a b i l i t y , and response to s e l e c t i o n i n P l e c t r i t i s  .....  19  the 21  M a t e r i a l s and methods  23  Source p o p u l a t i o n s  23  Growing c o n d i t i o n s  25  Measurements  ..  25  V  - vi Breeding  procedure  29  S e l e c t i o n procedure Base p o p u l a t i o n First  .....  32  .....  33  c y c l e of s e l e c t i o n  33  Subsequent c y c l e s of s e l e c t i o n  33  Progeny t e s t and o u t c r o s s i n g r a t e s i n P_j_ congesta  35  Data treatment  35  and a n a l y s e s  M e t r i c a l characters  36  Descriptive s t a t i s t i c s  36  Comparisons between d i s t r i b u t i o n s  38  Correlations  38  H e r i t a b i l i t y estimates  38  Variance w i t h i n populations  39  Other c h a r a c t e r s  39  Results  40  B r e e d i n g systems i n P l e c t r i t i s congesta P. brachystemon O u t c r o s s i n g r a t e s i n the source ( M i l l H i l l Pk. , 1977) O u t c r o s s i n g r a t e s i n the  and  40  of q u a l i t a t i v e c h a r a c t e r s  Response to s e l e c t i o n of the s e l e c t e d c h a r a c t e r s at anthesis  Means  41  of the m e t r i c a l  (quantitative) characters  Height  40  experimental  C h a r a c t e r i s t i c s of the base p o p u l a t i o n s  Frequencies  40  populations  populations  Descriptive s t a t i s t i c s  .....  41 44 44 44 44  - vii Estimates of v a r i a b i l i t y  57  Variances  57  Heritabilities  .....  Components o f v a r i a n c e Other changes  60 63  i n distribution  .....  Days t o a n t h e s i s ( f l o w e r i n g time)  64 64  Means  64  Estimates of v a r i a b i l i t y  67  Variances  67  Heritabilities  67  Components o f v a r i a n c e  70  Other changes  i n distribution  Changes i n the u n s e l e c t e d c h a r a c t e r s  .....  70  during  the experiment  71  Means  71 Days t o emergence  71  Height a t anthesis ( i n l i n e s for  selected  f l o w e r i n g time)  71  Nodes a t a n t h e s i s  74  Primary branches a t a n t h e s i s  74  Flowering  time ( i n l i n e s  selected  for height at anthesis) F r u i t production Estimates of v a r i a b i l i t y  79 79 84  Variances  84  Heritabilities  84  Components o f v a r i a n c e  89  Other changes  i n distribution  89  The  e f f e c t s o f s e l e c t i o n on c o r r e l a t i o n s the measured c h a r a c t e r s The  among 92  c o r r e l a t i o n between h e i g h t a t a n t h e s i s and f l o w e r i n g time, t h e c h a r a c t e r s under s e l e c t i o n  .....  Other c o r r e l a t i o n s  92  Changes i n q u a l i t a t i v e c h a r a c t e r s Winged and w i n g l e s s  .....  plant frequencies  124 124  Pubescence p a t t e r n s  125  Aberrant  125  characters  Comparisons between the i n t e r n a l p o p u l a t i o n s and the  control  source p o p u l a t i o n s  .....  Quantitative characters Plectritis  congesta  127 127  Correlations  130  Summary o f r e s u l t s  132  Discussion  .....  experimental  species .....  D i r e c t responses  Height  136 136  P l e c t r i t i s congesta o u t c r o s s e d P. congesta s e l f e d Plectritis  136 136  G e n e t i c v a r i a b i l i t y and the response t o s e l e c t i o n  congesta  versus  v e r s u s P^ brachystemon  136 .....  at anthesis  Flowering  time  responses t o s e l e c t i o n  137 137  .....  Confounding phenomena Indirect  125 127  P l e c t r i t i s brachystemon  The  92  139 140  .....  142  viii  - ix Unselected  characters  142  Other s e l e c t i o n s t u d i e s Independent e s t i m a t e s in Plectritis The  of g e n e t i c  e f f e c t s of b r e e d i n g  144 variability 146  system on the p o p u l a t i o n  g e n e t i c s t r u c t u r e of P l e c t r i t i s  149  P l e c t r i t i s brachystemon  150  Plectritis  156  congesta  Literature cited Appendix 1:  Appendix 2:  163  Between f a m i l y / w i t h i n f a m i l y v a r i a n c e r a t i o s i n experimental populations C o e f f i c i e n t s of v a r i a t i o n , characters  169  unselected .....  172  -  L i s t of  Tables  Table I II  III IV  V VI  VII VIII  IX  Title  Page  Growing c o n d i t i o n s  26  E s t i m a t e s of o u t c r o s s i n g r a t e s i n the e x p e r i m e n t a l populations  42  Measured c h a r a c t e r s , base p o p u l a t i o n s  43  Realised h e r i t a b i l i t y , of H i l l (1972)  61  Heritability,  c a l c u l a t e d u s i n g the method  from p a r e n t - o f f s p r i n g r e g r e s s i o n s  H e r i t a b i l i t i e s from p a r e n t - o f f s p r i n g r e g r e s s i o n s , unselected characters Frequencies  of a b e r r a n t i n d i v i d u a l s  62 90  126  Measured c h a r a c t e r s : G,. source p o p u l a t i o n s compared w i t h G^ c o n t r o l p o p u l a t i o n s  128  C o r r e l a t i o n s i n the G,. source p o p u l a t i o n s  131  X  - xi List  of F i g u r e s  Figure  Title  Page  1.  Source P l e c t r i t i s p o p u l a t i o n s : June 1977  M i l l H i l l Pk.,  2  Morphology of P l e c t r i t i s  28  3  Plectritis  30  4  F r u i t pubescence phenotypes i n winged P l e c t r i t i s congesta f r u i t s  31  5  Experimental populations maintained g e n e r a t i o n s of s e l e c t i o n , G^ to G,.  34  6  An example of data t r a n s f o r m a t i o n procedure used on m e t r i c a l c h a r a c t e r s  37  7  Frequency of v a r i o u s pubescence types i n the experimental populations a. PCO p o p u l a t i o n s , type 0 b. PCO p o p u l a t i o n s , type 1 c. PCO p o p u l a t i o n s , type 2  46  8  Frequency of v a r i o u s pubescence types experimental populations a. PCO p o p u l a t i o n s , type 3 b. PCO p o p u l a t i o n s , type 4 c. PCO p o p u l a t i o n s , type 5  i n the  48  9  Frequency of v a r i o u s pubescence types i n the experimental populations a. PCS p o p u l a t i o n s , type 0 b. PCS p o p u l a t i o n s , type 1 c. PCS p o p u l a t i o n s , type 2  50  10  Frequency of v a r i o u s pubescence types i n the experimental populations a. PCS p o p u l a t i o n s , type 3 b. PCS p o p u l a t i o n s , type 4 c. PCS p o p u l a t i o n s , type 5  52  11  Frequency of w i n g l e s s f r u i t e d p l a n t s i n the experimental populations a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s  54  12  Mean h e i g h t a t a n t h e s i s i n p o p u l a t i o n s s e l e c t e d f o r height at anthesis.  56  f r u i t wing phenotypes  through 5  24  - xii Figure  Title  Page  13  C o e f f i c i e n t s of v a r i a t i o n f o r height a t anthesis i n populations selected f o r height at anthesis  59  14  Mean number o f days t o a n t h e s i s ( f l o w e r i n g time) i n p o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time  66  15  C o e f f i c i e n t s o f v a r i a t i o n for, days t o a n t h e s i s i n p o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time  69  16  Mean number o f days t o emergence i n v a r i o u s populations a. P o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time b. Populations selected f o r height at anthesis  73  17  a. Mean selected b. Mean selected  76  18  Mean number of nodes a t a n t h e s i s i n v a r i o u s populations a. P o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time b. Populations selected f o r height at anthesis  78  19  Mean number o f p r i m a r y branches a t a n t h e s i s i n various populations a. P o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time b. Populations selected f o r height at anthesis  81  20  Mean f r u i t p r o d u c t i o n i n v a r i o u s p o p u l a t i o n s a. P o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time b. Populations selected f o r height at anthesis  83  21  C o e f f i c i e n t s o f v a r i a t i o n f o r number of days to emergence i n the e x p e r i m e n t a l p o p u l a t i o n s a. PCO b. PCS c. 'PBS  86  22  C o e f f i c i e n t s o f v a r i a t i o n f o r number o f nodes a t a n t h e s i s i n the e x p e r i m e n t a l p o p u l a t i o n s a. PCO b. PCS c. PBS  88  23  C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and f l o w e r i n g time a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  94  height at anthesis i n populations f o r f l o w e r i n g time number o f days t o a n t h e s i s i n p o p u l a t i o n s f o r height at anthesis  Figure  Title  Page  24  C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and number of p r i m a r y branches a t a n t h e s i s a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  96  25  C o r r e l a t i o n s between number o f nodes a t a n t h e s i s and number of p r i m a r y branches a t a n t h e s i s a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  98  26  C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and f r u i t production a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  100  27  C o r r e l a t i o n s between number of days to emergence and h e i g h t a t a n t h e s i s a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  103  28  C o r r e l a t i o n s between number of days to emergence and number o f nodes a t a n t h e s i s a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  105  29  C o r r e l a t i o n s between number of nodes a t a n t h e s i s and f r u i t p r o d u c t i o n a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  107  30  C o r r e l a t i o n s between number of primary branches a t a n t h e s i s and f l o w e r i n g time a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  109  31  C o r r e l a t i o n s between number of days to emergence and number of p r i m a r y branches a t a n t h e s i s a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  111  32  C o r r e l a t i o n s between number o f days to emergence and f r u i t p r o d u c t i o n a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  113  xiii  Title C o r r e l a t i o n s between f l o w e r i n g time and f r u i t production a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s C o r r e l a t i o n s between days t o emergence and f l o w e r i n g time a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s C o r r e l a t i o n s between number o f nodes a t a n t h e s i s and f l o w e r i n g time a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s C o r r e l a t i o n s between number o f p r i m a r y branches a t a n t h e s i s and f r u i t p r o d u c t i o n a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and number of nodes a t a n t h e s i s a. PCO p o p u l a t i o n s b. PCS p o p u l a t i o n s c. PBS p o p u l a t i o n s  -  XV  Acknowledgements  1 am me  deeply  g r a t e f u l to my  s u p e r v i s o r , Dr. F r e d Ganders, f o r i n t r o d u c i n g  to P l e c t r i t i s , a genus of t r u l y e n d l e s s  advice, i n t e r e s t  and  interest.  H i s knowledge  and  encouragement, and h i s w i l l i n g n e s s to d i s c u s s any  aspect  of the p r o j e c t , l a r g e or s m a l l , have added immeasurably to the q u a l i t y of the  result. I thank the members of my  t h e s i s committee, Dr. Tony G r i f f i t h s and  Gary B r a d f i e l d , f o r t h e i r p a t i e n c e and c r i t i c i s m throughout have helped me and  to c l a r i f y and  round out  advice.  to d i r e c t  i t s presentation.  T h e i r c a r e f u l and  constructive  the r e s e a r c h t o b e s t  advantage,  I am  g r a t e f u l to the members  of the Department of .^Botany at U.B.C., whose combined e x c e l l e n c e i n s t r u c t e d and  inspired  grants  to Dr.  and E n g i n e e r i n g  Research C o u n c i l of Canada  i n the form of P o s t - g r a d u a t e S c h o l a r s h i p s and  through  Ganders.  T h i s work would not have been the same without of my  has  me.  I thank the N a t u r a l S c i e n c e s f o r f i n a n c i a l support  Dr.  w i f e , A l i c e , who  d i f f i c u l t moments, and  kept me  c h e e r f u l and  shared my  the p a t i e n c e and  support  o p t i m i s t i c through the more  happiness when.things went w e l l .  - 1 Breeding  system, g e n e t i c v a r i a b i l i t y , , and response t o s e l e c t i o n i n Plectritis  (Valerianaceae).  Introduction  Genetic v a r i a b i l i t y study  i n v a r i o u s organisms has been a major o b j e c t o f  s i n c e t h e r e d i s c o v e r y o f Mendel's laws o f i n h e r i t a n c e and t h e i r  s y n t h e s i s w i t h Darwin's theory o f e v o l u t i o n by n a t u r a l s e l e c t i o n . of q u e s t i o n s  t o which answers a r e sought i n c l u d e q u e s t i o n s  to which v a r i a b i l i t y i s p r e s e n t  The k i n d  about t h e extent  i n i n d i v i d u a l s , populations,.or  the ways i n which v a r i a b i l i t y i s g e n e r a t e d , m a i n t a i n e d , o r l o s t ;  taxa;  about  and about  the e f f e c t which v a r i a b i l i t y may. have on the f i t n e s s o r s u r v i v a l o f an i n d i v i d u a l , p o p u l a t i o n , o r taxon. T h i s study  deals with the f o l l o w i n g questions  about.genetic  variability.  F i r s t , how has t h e amount o f g e n e t i c v a r i a b i l i t y u n d e r l y i n g t h e e x p r e s s i o n of q u a n t i t a t i v e l y i n h e r i t e d c h a r a c t e r s i n a p o p u l a t i o n o f p l a n t s been a f f e c t e d by the b r e e d i n g  system of t h a t p o p u l a t i o n ?  system has a f f e c t e d the amount o r n a t u r e e f f e c t be d e t e c t e d by o b s e r v i n g  Second, i f the b r e e d i n g  of genetic v a r i a b i l i t y ,  can t h i s  the response t o s e l e c t i o n i n two t a x a  between which t h e major b i o l o g i c a l d i f f e r e n c e i s i n t h e i r b r e e d i n g F i n a l l y , how does the g e n e t i c v a r i a b i l i t y present i n h e r i t e d c h a r a c t e r s compare t o t h a t o f o t h e r  i n more c o n c r e t e  i n quantitatively  (monogenic) c h a r a c t e r s , b o t h  w i t h i n and between t a x a w i t h d i f f e r e n t b r e e d i n g questions  systems?  To combine the  terms., i s a p o p u l a t i o n of i n b r e e d i n g p l a n t s more  or l e s s v a r i a b l e g e n e t i c a l l y than a p o p u l a t i o n o f "otherwise outbreeding  system?  identical"  p l a n t s with respect to q u a n t i t a t i v e l y i n h e r i t e d characters,  does i t respond more or l e s s q u i c k l y t o s e l e c t i o n p r e s s u r e s  on these  -2 c h a r a c t e r s , and does the g e n e t i c v a r i a b i l i t y , .in m u l t i g e n i c f o l l o w the same p a t t e r n s as v a r i a b i l i t y  i n monogenic  Both t h e o r e t i c a l p r e d i c t i o n s and e x p e r i m e n t a l some answers to a l l t h r e e of these  questions..  characters?  evidence  have  provided  Differences i n genetic  v a r i a b i l i t y between p l a n t s p e c i e s o f . v a r i e d . b r e e d i n g s t u d i e d by p o p u l a t i o n b i o l o g i s t s ; i n most cases  systems have been  the c h a r a c t e r s s t u d i e d have  been monogenic r a t h e r than q u a n t i t a t i v e l y i n h e r i t e d . response t o s e l e c t i o n a r e o f v i t a l i n t e r e s t  characters  Differences i n  to plant breeders;,  i n most  of t h e i r s t u d i e s the g o a l s have n o t i n c l u d e d a s s e s s i n g the e f f e c t s of the breeding  systems o f the p l a n t s i n v o l v e d , or more p a r t i c u l a r l y  species of d i f f e r i n g breeding  system.  There i s a p l a c e  comparing  (not t o say a gap)  to be f i l l e d by s e l e c t i o n s t u d i e s o f q u a n t i t a t i v e l y i n h e r i t e d c h a r a c t e r s i n natural populations;  i t i s t o be.hoped t h a t such s t u d i e s w i l l add t o  what i s known about b r e e d i n g  systems, g e n e t i c . v a r i a b i l i t y , response t o  s e l e c t i o n , and the i n t e r a c t i o n s among the t h r e e .  Breeding  system and g e n e t i c  Theoretical  A first  variability  considerations  step i n answering q u e s t i o n s  about g e n e t i c v a r i a b i l i t y i s  n e c e s s a r i l y the d e f i n i t i o n o f some of the terms.  Genetic.variability i s a  broad term which can l e a d to some c o n f u s i o n i f l o o s e l y . a p p l i e d . I t encompasses a number o f parameters i n a n y . p o p u l a t i o n , and  f r e q u e n c i e s o f a l l e l e s a t v a r i o u s gene l o c i ,  i n c l u d i n g - t h e numbers  the numbers and f r e q u e n c i e s  of v a r i o u s genotypes, and the d i s t r i b u t i o n of g e n o t y p i c t o t a l phenotypic  variance  for various characters.  components,of the  A l t h o u g h these  parameters  are n o t independent, they can be d i v i d e d i n t o two groups on the b a s i s of  - 3 whether or not  they are s u b j e c t -to s e l e c t i o n d i r e c t l y .  The  first  group I  w i l l c a l l the p o t e n t i a l components of .the g e n e t i c v a r i a b i l i t y i n a population.  In the s i m p l e s t g e n e t i c sense,.a gene l o c u s i s v a r i a b l e  (polymorphic) i f more than one the number and be observed. individual.  a l l e l e occurs  at i t . For any  f r e q u e n c i e s of a l l e l e s at v a r i o u s l o c i can These a l l e l e s w i l l be  The number and  types of o b s e r v a t i o n s ;  used i n s t u d i e s of r e a l p o p u l a t i o n s  Various  have been d e r i v e d . two  alleles,  possible.  An  the number of a l l e l e s  loci  per  of genotypes expected i n  to p a r t i c u l a r assumptions can.be . c a l c u l a t e d .  Most o f t e n the assumptions are those  behaving a c c o r d i n g  be  some examples which are commonly  In a d d i t i o n , . t h e f r e q u e n c i e s  a p o p u l a t i o n behaving a c c o r d i n g  i n d i c e s can  a r e the number or percentage of  which are observed to be polymorphic, and  in a theoretical population.  an  f r e q u e n c i e s of v a r i o u s genotypes i n any -  polymorphic l o c u s .  theoretically  combined to form the genotype of  p o p u l a t i o n can a l s o be o b s e r v e d t h e o r e t i c a l l y . d e r i v e d from these  population  The  l e a d i n g to Hardy-Weinberg ..equilibrium  populations  under study may  to the.assumptions by which the genotype  not  be  frequencies  F o r example, i f at a p a r t i c u l a r l o c u s a p o p u l a t i o n  and A^,  then t h e o r e t i c a l l y  a c t u a l p o p u l a t i o n may  t h e r e a r e t h r e e genotypes -  i n f a c t be m i s s i n g  any  t h r e e genotypes (or even both'homozygous genotypes), and i n f a c t than i t appears i n t h e o r y .  has  one  of  the  be l e s s v a r i a b l e  Many s t u d i e s of t h i s type of  genetic  v a r i a b i l i t y c a l c u l a t e genotype f r e q u e n c i e s r a t h e r than o b s e r v i n g  them i n  populations.  S i n c e a l l e l e s and  r a t h e r through t h e i r e x p r e s s i o n  genotypes are not  selected directly  but  i n phenotypes, i t should be kept i n mind  t h a t i n d i c e s which compare p o p u l a t i o n s  on t h i s b a s i s may  the g e n e t i c v a r i a b i l i t y a v a i l a b l e f o r s e l e c t i o n . problem i n s t u d i e s d e a l i n g w i t h isoenzymes;  not be  assessing  T h i s has been a p a r t i c u l a r  the s e l e c t i v e v a l u e s  of  - 4 p a r t i c u l a r isoenzyme phenotypes a r e f o r the most p a r t unknown.. I . w i l l r e f e r to-these  estimates.of  genetic.diversity  p o t e n t i a l . g e n e t i c v a r i a b i l i t y .as. e s t i m a t e s  of  (a term.which.has a more s p e c i f i c a p p l i c a t i o n i n some  of the l i t e r a t u r e of p o p u l a t i o n g e n e t i c s ) . I f the c o n t r i b u t i o n of v a r i o u s genotypes to the g e n o t y p i c the t o t a l phenotypic  component of  v a r i a n c e f o r a p a r t i c u l a r c h a r a c t e r can be  a r b i t r a r i l y or determined by experiment, then one  assigned  i s dealing with  the  second group of parameters, which I w i l l c a l l the r e a l i s e d components of the g e n e t i c v a r i a b i l i t y . be  assigned  a numerical  For any  c h a r a c t e r a p a r t i c u l a r phenotype  v a l u e , be  i t a f i t n e s s v a l u e or an a c t u a l  measurement ( h e i g h t , weight, e t c . ) , and i n a p o p u l a t i o n w i l l have.a mean and of t h i s t o t a l phenotypic and  effect  the d i s t r i b u t i o n of these  component  v a r i a n c e i s r e f e r r e d to as the g e n e t i c  variance,  of b r e e d i n g  a variance.  t h a t s e l e c t i o n may  The  values  genotypic  i t i s upon t h i s v a r i a n c e The  can  act.  system on the p o t e n t i a l g e n e t i c  variability,  or g e n e t i c d i v e r s i t y , can be p r e d i c t e d i n . t h e o r y i f a number of assumptions are i n v o k e d .  I f two  populations  are i n i t i a l l y  t h a t i s , c o n t a i n e q u a l numbers and otherwise will  i d e n t i c a l i n a l l respects,  f r e q u e n c i e s of genotypes, and  i n Hardy-Weinberg e q u i l i b r i u m , then b r e e d i n g  affect  them i n the f o l l o w i n g way.  i n d i v i d u a l s at a p a r t i c u l a r l o c u s , and  .The  frequency  are  system d i f f e r e n c e s of heterozygous  i n consequence the t o t a l number of  genotypes, w i l l q u i c k l y d e c l i n e i n the i n b r e e d i n g or autogamous p o p u l a t i o n compared to the random mating p o p u l a t i o n .  However, the t o t a l number  and  f r e q u e n c i e s of a l l e l e s , the percentage of l o c i which are p o l y m o r p h i c , and number of a l l e l e s per. polymorphic, l o c u s w i l l remain the same, as w i l l , the genotype f r e q u e n c i e s expected under Hardy-Weinberg, e q u i l i b r i u m . I f the e q u i l i b r i u m assumptions are r e l a x e d , and  realistic  and  finite  the  - 5 p o p u l a t i o n ' s i z e and drift  and  s e l e c t i o n , are a f f e c t i n g ..the p o p u l a t i o n s ,  random  s e l e c t i o n w i l l . r e d u c e . . t h e . t o t a l number:of a l l e l e s i n the  p o p u l a t i o n f a s t e r than i n the o u t c r o s s e d  one,, and.genetic  selfing  diversity  as  measured by the percentage of l o c i polymorphic, the number of a l l e l e s  per  polymorphic l o c u s , and.the expected.frequency of h e t e r o z y g o t e s  at  equilibrium w i l l  thus be reduced i n the s e l f e r r e l a t i v e to the  outcrossed  population.  degree o f . d i f f e r e n c e i n g e n e t i c d i v e r s i t y between the  The  populations  of d i f f e r e n t b r e e d i n g  two  system w i l l depend on the d i f f e r e n c e i n  t h e i r r a t e s of i n b r e e d i n g , the e f f e c t i v e p o p u l a t i o n s i z e , and  r a t e s of  selection. The  e f f e c t of the b r e e d i n g  system on the r e a l i s e d  genetic.variability  o r g e n e t i c v a r i a n c e can a l s o be p r e d i c t e d i n t h e o r y , a g a i n s u b j e c t t o a number of s i m p l i f y i n g assumptions.. I f we  s t a r t w i t h the same two  as mentioned above, w i t h , i d e n t i c a l g e n o t y p i c e q u i l i b r i u m , then b r e e d i n g  s t r u c t u r e under Hardy-Weinberg  system d i f f e r e n c e s w i l l have the f o l l o w i n g e f f e c t s .  I f • the e n v i r o n m e n t a l component of the . t o t a l phenotypic case i s taken to be z e r o , then the g e n o t y p i c of the phenotypic lost  populations  variability.  values  variance i n this  are c o n t r i b u t i n g a l l  With s e l f i n g , as heterozygous genotypes  from.the p o p u l a t i o n the v a r i a n c e of the phenotypic  r e l a t i v e to a random mating p o p u l a t i o n .  values w i l l  Thus i n b r e e d i n g on i t s own  are  increase will  increase genetic variance. . I f we  a g a i n r e l a x the e q u i l i b r i u m assumptions by assuming  f i n i t e populations  on which s e l e c t i o n i s a c t i n g , then the  p r e d i c t i o n becomes r a t h e r p r o b l e m a t i c a l . a l l e l e s due'to random d r i f t w i l l tend.to  and  The  theoretical  r e l a t i v e l y l a r g e r l o s s of  s e l e c t i o n i n f i n i t e populations  reduce the g e n e t i c v a r i a n c e .  realistic  Simultaneously,  of  selfers  inbreeding.will  i n c r e a s e the g e n e t i c v a r i a n c e r e l a t i v e to a random mating p o p u l a t i o n .  The  - 6 e f f e c t s on w i l l be  genetic variance  i n opposite  L a n d e Q.977) h a s are  d i r e c t i o n s , and  the net  To  random d r i f t  effect  / selection  c a n n o t be  generalized.  proposed a model which i n d i c a t e s t h a t i f the  s y s t e m w i l l h a v e no  variance  e f f e c t on  mutation  populations  a c t i n g , then  the  t h e amount o f a d d i t i v e g e n e t i c  maintained. summarize, such t h e o r e t i c a l  (without extensive generalized with finite  depend on  simplifying  caution.  populations  and w h e t h e r t h i s  and  and  l a r g e C i n f i n i t e ) , b u t w i t h s e l e c t i o n and  breeding  in  of inbreeding  treatments  a s s u m p t i o n s ) as  Nevertheless,  of r e a l i s t i c are  populations  a v a i l a b l e should  compared t o random m a t i n g ,  i s l i k e l y , to l e a d to a l o s s of g e n e t i c  i s accompanied by  factors unrelated  a net  be selfing  diversity,  reduction i n genetic variance  to the breeding  will  s y s t e m , s u c h as p o p u l a t i o n  size  s e l e c t i o n pressures.  Experimental  evidence  V a r i a b i l i t y has n a t u r a l and  been s t u d i e d i n p o p u l a t i o n s  domesticated.  o f many p l a n t s p e c i e s , b o t h  Discontinuities i n variation patterns  taxa form the b a s i s f o r taxonomic s t u d i e s ; g e n e t i c v a r i a b i l i t y o f improvement by  plant breeders i n economically  i n t e r a c t i o n o f g e n e t i c v a r i a t i o n and evolutionary studies. genetic v a r i a b i l i t y species The  differing  i n breeding  variability  can be  variability  roughly  parallel The  first  those  s p e c i e s ; and  i s o l a t i n g breeding  as y e t v e r y  evidence r e l a t i n g breeding two  source the  of  system  and  comparisons between c l o s e l y r e l a t e d  system are  divided into  i s the  natural s e l e c t i o n i s the'object  specifically  a r e l i m i t e d , and  experimental  genetic variance.  Studies  important  between  few.  s y s t e m and  genetic  groups i n which the estimates outlined earlier  as  of  genetic  genetic diversity  group c o n s i s t s of e v i d e n c e from monogenic  or  and  single locus  t r a i t s , whose q u a l i t a t i v e n a t u r e  s p e c i f i c phenotypic value  and  values,  and  variance, d i f f i c u l t .  estimated  e x p e r i m e n t a l l y , but  is  form of estimates  i n the  I n some c a s e s f i t n e s s v a l u e s h a v e b e e n f o r the most p a r t  the e x p e r i m e n t a l  of g e n e t i c d i v e r s i t y  i n d i c e s s u c h as  and  polymorphic locus.  s u c h as  allele  approximately may  estimates  require f a i r l y  For  these  The  characters  components o f the v a r i a n c e  and  and  multigenic,  the e s t i m a t e s  designs  o b t a i n more e x a c t  polymorphic  second group c o n s i s t s of  of genetic variance, although  elaborate experimental  evidence  the percentage of l o c i  e v i d e n c e f r o m c h a r a c t e r s w h i c h a r e k n o w n o r a s s u m e d t o be quantitatively inherited.  of  t h u s p o p u l a t i o n p a r a m e t e r s s u c h as mean  g e n o t y p e f r e q u e n c i e s , and number o f a l l e l e s p e r  makes a s s i g n m e n t  are  as w i l l b e  to eliminate estimates  or  seen  they  environmental  of the  genetic  variance.  Monogenic  traits  Because o f the ease w i t h w h i c h r e l a t i v e l y c a n be  s t u d i e d , the bulk, of s t u d i e s a l l o w i n g a comparison of  s y s t e m and etically  g e n e t i c v a r i a b i l i t y i n monogenic c h a r a c t e r s  d e t e c t a b l e enzyme v a r i a t i o n .  the isozyme data Cgenetic  recently, relating  diversity)  plant species. percentage of and  l a r g e numbers o f  and  breeding  involve electrophor-  H a m r i c k e t a l . (1979) have  levels  reviewed  of e l e c t r o p h o r e t i c v a r i a t i o n  l i f e h i s t o r y c h a r a c t e r i s t i c s i n a l a r g e number  They r e p o r t t h a t f o r t h r e e i n d i c e s of d i v e r s i t y l o c i polymorphic,  a polymorphic index  characters  number o f a l l e l e s p e r  Cfrequency of heterozygotes  W e i n b e r g e q u i l i b r i u m ) - 36 p r i m a r i l y o u t c r o s s e d t h a n 33 p r i m a r i l y s e l f e d s p e c i e s .  For  of  -  polymorphic  locus,  e x p e c t e d u n d e r Hardy--  species  showed m o r e  t h e most p a r t t h e s e  data  diversity  combine  - 8 r e l a t i v e l y u n r e l a t e d taxa i n each breeding some c o m p a r i s o n s w h i c h may b e n o t e d .  system group, b u t there are  F o r e x a m p l e , g r o u p s of  congeneric  s p e c i e s i n w h i c h l e v e l s o f g e n e t i c d i v e r s i t y have been confirmed in  the outcrossed  alba (outcrossed)  s p e c i e s than i n the s e l f e d  species include:  t o be h i g h e r  Limnanthes  a n d L . f l o c c o s a ( s e l f e d ) CBrown a n d J a i n , " 1 9 7 9 ) ;  Clarkia  r u b i c u n d a , C. amoena ( o u t c r o s s e d ) , a n d C_. f r a r i c i s c a n a ( s e l f e d ) ( G o t t l i e b , 19 73) ; G a u r a s u f f u l t a 1975) ; P h l o x (selfed)  (outcrossed)  a n d Gy t r i a r i g u l a t a  (selfed) (Levin,  d r u m i i i o n d i i , P_.^ r o e m a r j a n a ( o u t c r o s s e d ) , a n d P_j_ c u s p i d a t a  (Le-yin, 1978); Leavenworthia  a l a b a r n i c a , L. c r a s s a , L.  ( o u t c r o s s e d ) , L . u r i i f l o r a , \'h. e x j g u a , " a n d 1972) ; L y c o p e r s i c o n p i m p i n e l l j f o l i u m  L. t o r u l o s a ( s e l f e d )  (outcrossed)  L. p a r v i f l o r u m ( s e l f e d ) ( R i c k a n d F o b e s , 1 9 7 5 ) .  outcrossed  to relatively  At the c o n s p e c i f i c l e v e l ,  Ln  Oenothera, E l l s t r a n d  system from  s e l f e d , a n d t h e more h i g h l y  p o p u l a t i o n s have h i g h e r l e v e l s o f g e n e t i c d i v e r s i t y •  and L e v i n (1980) found  (Solbrig,  ( R i c k e t a l . , 1977) a n d  populations of Lycopersicon p i m p i n e l l j f o l i u m vary i n breeding relatively  stylosa  outcrossed  ( R i c k e t a l . , 1977).  t h a t t h e r e was a  significant  d i f f e r e n c e i n gene d i v e r s i t y b e t w e e n t h e more d i v e r s e , o u t c r o s s e d 0. and  t h e s e l f e d 0. m e x i c a n a .  A third  s p e c i e s , 0. 1 a c i n i a t a , w h i c h i s h i g h l y  i n b r e d b u t a permanent t r a n s l o c a t i o n h e t e r o z y g o t e , has r e l a t i v e l y diversity, not s i g n i f i c a n t l y i n t e r e s t i s the study and  different  much h i g h e r l e v e l s  f r o m 0. g r a n d i s .  o f t h e two c l o s e l y  P_j_ b r a c h y s t e m o n , w h i c h i n d i c a t e d  and M a r s h a l l ( 1 9 6 7 ) f o u n d  Of p a r t i c u l a r  related species P l e c t r i t i s  as i n d i c a t e d b y i s o z y m e d a t a  congesta  than  1980).  There are fewer s t u d i e s of other types particularly i n closely related  high  t h a t t h e o u t c r o s s e d P_^_ c o n g e s t a h a s  of genetic d i v e r s i t y  t h e s e l f e d P. b r a c h y s t e m o n ( L a y t o n ,  grandis  o f monogenic c h a r a c t e r s ,  taxa of d i f f e r e n t breeding  systems.  t h a t Avena f a t u a , which has a s l i g h f l y  Jain  higher  - 9 o u t c r o s s i n g r a t e t h a n i t s r e l a t i v e A. b a f b a t a , was p o l y m o r p h i c a t t h r e e morphologically expressed same l o c i .  l o c i , w h i l e A. b a r b a t a was m o n o m o r p h i c  However, w h i l e  there i s a s l i g h t  at the  difference i n breeding  b e t w e e n them, b o t h Avena s p e c i e s  are r e l a t i v e l y h i g h l y s e l f e d .  Plectritis  p o l y m o r p h i c f o r a monogenic f r u i t  character  congesta,  populations  a r e much more common C30 p o p u l a t i o n s  C a r e y and G a n d e r s , 1 9 8 0 ) . CL977)  levels  of polymorphism i n populations  and w e r e m o n o m o r p h i c i n p o p u l a t i o n s All  outcrossed wing  studied)  ( G a n d e r s e t a l . , 1977b;  pimpinellifolium, Rick e t a l .  f o u n d t h a t two m o n o g e n i c m o r p h o l o g i c a l  highest rates  I n Lycopersicon  In  p o l y m o r p h i c o f 32  t h a n i n s e l f e d P. b r a c h y s t e m o n C3 o f 11 p o p u l a t i o n s )  system  characters with  showed  the highest  their outcrossing  w h i c h were r e l a t i v e l y h i g h l y  o f t h e e v i d e n c e from monogenic t r a i t s  suggests that  selfed.  selfing  reduces the g e n e t i c d i v e r s i t y r e l a t i v e t o a comparable o u t c r o s s e d  population  ( m o s t o f t h i s e v i d e n c e comes f r o m i s o z y m e l o c i , w h i c h may o r may n o t b e representative of a l l l o c i ) .  T h i s i s i n agreement w i t h t h e t h e o r e t i c a l  predictions.  Quantitative  traits  D a t a on t h e g e n e t i c v a r i a b i l i t y i n s e l f e d or outcrossed monogenic t r a i t s .  are l e s s s t r a i g h t f o r w a r d than those  F i r s t , many o f t h e s e  known, t o be m u l t i g e n i c . continuously  species  of multigenic or q u a n t i t a t i v e characters  distributed  characters  on  a r e assumed, r a t h e r  T h e y m i g h t more a c c u r a t e l y b e t e r m e d m e t r i c a l o r traits.  confounded by an e n v i r o n m e n t a l  Second, these  characters  are invariably  c o m p o n e n t w h i c h may b e d i f f i c u l t  t o remove  except i n large s c a l e , c a r e f u l l y designed  experiments.  genetic v a r i a b i l i t y  a r e f u r t h e r removed f r o m t h e  genome t h a n t h o s e  than  from these  characters  Third, estimates  from monogenic c h a r a c t e r s ; t h a t i s , a l l e l e  of  frequencies,  r  polymorphic l o c i , directly study  and r a t e s o f h e t e r o z y g o s i t y  from measurements  has b e e n done.  d a t a on v a r i o u s  C1979)  of these  For these  are r a r e l y d i s c e r n i b l e  characters unless  extensive  reasons a review which b r i n g s  the measurements  Finally,  genetic together  t a x a f r o m many s t u d i e s , s u c h a s t h a t o f H a m r i c k e t a l . •  f o r i s o z y m e d a t a , i s n o t f e a s i b l e , as t h e r e i s l i t t l e  characters  of genetic v a r i a b i l i t y  under d i f f e r e n t e x p e r i m e n t a l  as w i t h m o n o g e n i c t r a i t s ,  assurance  examine a few o f t h e s e  designs  can v a l i d l y  there have been only  at this point.  be  compared.  a limited  number  which estimates refer  variance  i s being  estimated  s y s t e m s was  characters concluded  variance,  found.  i n Limrianthes  although  one may  hope t h a t  from I  will  genetic  approximately.  I n some c a s e s no s i g n i f i c a n t breeding  are of phenotypic  environmental  o f t h e g e n e t i c v a r i a b i l i t y have been e x t r a p o l a t e d ,  t o i t as g e n e t i c v a r i a b i l i t y ,  I  I n most c a s e s t h e v a r i a b i l i t y  t h a t h a s b e e n m e a s u r e d h a s n o t b e e n p a r t i t i o n e d i n t o g e n e t i c and c o m p o n e n t s , and t h e a c t u a l m e a s u r e m e n t s  that  from a wide v a r i e t y of m e t r i c a l  of s t u d i e s of c l o s e l y r e l a t e d taxa with.'dif ferent-breeding.- systems. will  10  d i f f e r e n c e between t a x a w i t h  different  B r o w n and J a i n ( 1 9 7 9 ) s t u d i e d 15 q u a n t i t a t i v e  alba (outcrossed)  that both the t o t a l  and L . f l o c c o s a ( s e l f e d ) and  amount o f g e n e t i c v a r i a b i l i t y  and t h e  p a r t i t i o n i n g of the v a r i a b i l i t y w i t h i n the taxa  ( t h a t i s , w i t h i n and between  populations  d i f f e r e n t between  This  of the taxa)  were n o t s i g n i f i c a n t l y  i s i n contrast t o the s i t u a t i o n  species, described included  above ( p . 9 ) .  f o u r L. n a n u s s u b s p e c i e s  r a t e s b e t w e e n 0 and 1 0 0 % , H a r d i n g the  found i n the isozymes i n these  Studying  genetic variance)  two  t h e L u p i n u s nanus group, w h i c h  a n d two o t h e r s p e c i e s w i t h  outcrossing  e t a l . ( 1 9 7 4 ) f o u n d no c o r r e l a t i o n  o u t c r o s s i n g r a t e a n d t h e amount o f g e n e t i c v a r i a b i l i t y  estimated  them.  ( i n this  f o r s i x quantitative characters.  In  between case  three  grass  11  s p e c i e s j Fe.sttj.ca m i c f o s t a c h y s C c o m p l e t e l y • s e l f ed) , A v e r i a f a t u a  ( h i g h l y s e l f e d ) , and ( 1 9 6 7 ) f o u n d no  Lolium mtiltiflorum  d i f f e r e n c e among t h e  ( . o u t c r o s s e d ) , K a n n e n b e r g and  three  species  Allard  i n genetic variance  for  three q u a n t i t a t i v e characters. I n some c a s e s t h e more h i g h l y o u t c r o s s e d variable.  In Lycopersicon  species  showed maximum v a r i a b i l i t y  a r e a s w h i c h c o i n c i d e d w i t h maximum i s o z y m e d i v e r s i t y minimum v a r i a b i l i t y  these observations the  characters  degenii. and  concerned.  exjgua ssp. derivative and  S t r i d . ' ( 1 9 70)  S.  f o u n d 90%  evolved  characters  maximum  rates;  a c t u a l measurements  of N i g e l l a  i n flowering  time  and  In  i t s obligately selfed  more v a r i a b l e i n t h e  viewed k e e p i n g i n mind t h a t  genetic v a r i a b i l i t y .  genetic  A.  the  I n A y e n a f a t u a and  studied 3 quantitative characters f a t u a t h a n i n A.  a c t u a l l y h i g h l y s e l f e d , and  and  A.  These  founder e f f e c t , which a l s o b arb at a J a i n  and  Marshall  but  Rogers(1971) found i n Papayer rhoeas ( o u t c r o s s e d ) ,  P.  (selfed) that  than between p o p u l a t i o n  characters,  and  in  as n o t e d a b o v e , b o t h  instance.  variability  species  variability  that the s e l f e d species  data  still  comparison i s l e s s u s e f u l . i n  the o u t c r o s s e d  traits  malheurensis i s a recently  f o u n d more g e n e t i c v a r i a n c e  barbata, the  outcrosser.  s t r u c t u r e i s probably  t o phenomena s u c h as  again  Stephanomeria  of  them t o be  of  a s e l f e d s p e c i e s , but  have been r e p o r t e d . species,  outcrossing  G o t t l i e b ( 1 9 7 7 ) m e a s u r e d 33 q u a n t i t a t i v e  extensively subject  lecoqli  geographic  noted that populations  dOerfleri,  that  malheurensis,  t a x o n whose p o p u l a t i o n  "outcrossed"  b a s e d on  s p e c i e s , s h o w e d more v a r i a b i l i t y  c o r o n a r i a , an o u t c r o s s e d  m u s t , h o w e v e r , be  are  not  p e r c e n t a g e o f g o o d p o l l e n t h a n N.  no m e a s u r e m e n t s o f t h e  and  in  i n a r e a s w i t h minimum o u t c r o s s i n g  were u n f o r t u n a t e l y  an o u t c r o s s e d  more  p i m p i n e l l i f o l i u m R i c k e t a l . (1977) n o t e d  several quantitative characters  r a t e , and  appears t o be  P.  showed t h e  (1967) the  species this  dubium,  s h o w e d more w i t h i n f o r two  and  population  quantitative  reverse,  limit  that i s less  within population v a r i a b i l i t y  and m o r e b e t w e e n p o p u l a t i o n s .  u n c l e a r w h e t h e r t h e o v e r a l l v a r i a b i l i t y was than w i t h i n  the s e l f e d s p e c i e s .  Baker  i n c o m p a t i b l e ) and'A: m a r i t i m a s s p . c a l i f o r n i c a  h i g h l y o u t c r o s s e d .taxon was  situation  found  t h a t t h e f o r m e r , more  more v a r i a b l e w i t h i n t h a n b e t w e e n p o p u l a t i o n s ,  I n a d d i t i o n , he  more g e n e t i c v a r i a b i l i t y Plectritis fruit  congesta  that A..maritima  i n t o t o t h a n A.  In  G a n d e r s and M a z e ( u n p u b l i s h e d ) showed t h e o u t c r o s s e d  than i t s outcrossed r e l a t i v e .  longissimum  showed  a s t u d y o f a number o f m o r p h o m e t r i c  t h e r e are cases where the s e l f e d  36 q u a n t i t a t i v e  ssp. maritima  within  maritima ssp. c a l i f o r n i c a .  t o be more v a r i a b l e t h a n t h e s e l f e d P.  Finally variable  found  c o n g e s t a a n d P. b r a c h y s t e m o n ,  c h a r a c t e r s by  ssp.  (self  t h e l a t t e r , more h i g h l y s e l f e d t a x o n more v a r i a b l e b e t w e e n t h a n  populations.  P.  the outcrossed  c h a r a c t e r s i n A. m a r i t i m a  c o m p a t i b l e b u t more o r l e s s o u t c r o s s e d ) w h e r e h e  and  It is  (1953) s t u d i e d a s i m i l a r  i n Armeria, looking at several quantitative maritima (self  greater within  12  brachystemon.  t a x o n i s a p p a r e n t l y more  H i l l e l e t a l . (1973) s t u d i e d  c h a r a c t e r s i n T r i t i c u m s p e l t o i d e s , ( o u t c r o s s e d ) and  ( s e l f e d ) and  concluded  genetic v a r i a b i l i t y within  t h a t the s e l f e d  families  T.  s p e c i e s showed g r e a t e r  and 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 t h a n  the o u t c r o s s e d s p e c i e s . The  o v e r a l l i m p r e s s i o n from the evidence  quantitative is  of g e n e t i c v a r i a b i l i t y  characters i s t h a t the e f f e c t of a p a r t i c u l a r breeding  i n fact d i f f i c u l t  to p r e d i c t .  i t i s possible  d i f f e r e n c e s i n t h e e n v i r o n m e n t a l c o m p o n e n t o f t h e t o t a l v a r i a n c e may the  comparison.  Genetic v a r i a b i l i t y  and  the response  Theoretical considerations  system  S i n c e i n most o f t h e c a s e s p r e s e n t e d  t h e e s t i m a t e o f g e n e t i c v a r i a n c e i s n o t an a c c u r a t e o n e ,  affecting  in  to d i r e c t i o n a l  selection  be  here that  - 13 Can  the response t o s e l e c t i o n f o ra p a r t i c u l a r c h a r a c t e r be  p r e d i c t e d b y an i n d e p e n d e n t e s t i m a t e with  the f i r s t  terms.  question, i t i s necessary  S e l e c t i o n i s any process  individuals  of genetic v a r i a b i l i t y ? at the outset  than randomly.  direction.  f o rthat character i s different  those  w h i c h do n o t s u r v i v e t o  Directional selection f o ra  c h a r a c t e r i s t h e d i f f e r e n t i a l s u r v i v a l o f i n d i v i d u a l s whose expression  as  t o d e f i n e some  i n a population which divides  s u r v i v i n g t o reproduce from those  r e p r o d u c e i n Some way o t h e r  Again,  phenotypic  f r o m t h e p o p u l a t i o n mean i n one  Response t o s e l e c t i o n i s f u n d a m e n t a l l y  any change i n t h e  g e n e t i c s t r u c t u r e o f a p o p u l a t i o n w h i c h can be a t t r i b u t e d t o s e l e c t i o n pressure.  S e l e c t i o n a c t s on p h e n o t y p e s , b u t t h e d i r e c t  s e l e c t i o n , i f any, takes because genotypic  response t o  place i n the genotypes i n a p o p u l a t i o n .  changes i n a p o p u l a t i o n  I t i s  are r e f l e c t e d i n the t o t a l  p o p u l a t i o n phenotype t h a t s e l e c t i o n r e s p o n s e s can be o b s e r v e d , and i n t h e case o f l o n g term s e l e c t i o n ,  that the s e l e c t i o n process  can continue.  T h e s e r e s p o n s e s a r e u s u a l l y o b s e r v e d as c h a n g e s i n p o p u l a t i o n mean a n d variance  f o r those  changes i n a l l e l e is  directly  c h a r a c t e r s w h i c h a r e q u a n t i t a t i v e l y i n h e r i t e d , o r as o r genotype f r e q u e n c i e s  observable  f o r c h a r a c t e r s whose  i n t h e p h e n o t y p e o f an i n d i v i d u a l .  genotype  Fisher's  fundamental theorem o f n a t u r a l s e l e c t i o n s t a t e s t h a t t h e response t o s e l e c t i o n f o ra character i n a population i s d i r e c t l y p r o p o r t i o n a l to the genetic variance  f o rthat character  i n the population.  Of i n t e r e s t  p o i n t i s the p r e d i c t i o n o f response to s e l e c t i o n f o r a character basis of estimates  of genetic v a r i a b i l i t y  i s not p o s s i b l e i n theory to which p a r t i c u l a r  unless  characters  We c o u l d assume t h a t c h a r a c t e r s variability  are completely  at this  on t h e  i n independent characters.  This  some a s s u m p t i o n s a r e made a b o u t t h e e x t e n t  a r e r e p r e s e n t a t i v e o f t h e genome a s a w h o l e . f o r w h i c h we h a v e e s t i m a t e s  of genetic V  r e p r e s e n t a t i v e o f c h a r a c t e r s which might be  - 14 subject  to s e l e c t i o n .  depend once a g a i n  success- o f the p r e d i c t i o n i n t h i s  on w h e t h e r o u r e s t i m a t e  g e n e t i c v a r i a n c e . ' As do n o t  The  outlined e a r l i e r , estimates  of genetic  or  of  diversity  n e c e s s a r i l y measure v a r i a b i l i t y w h i c h i s a v a i l a b l e f o r s e l e c t i o n t o  estimates  neglect  component o f directly  as  the  the e n v i r o n m e n t a l t o t a l phenotypic  t o c o n f o u n d any  o f the q u e s t i o n has equal  c o m p o n e n t , w h i c h may variability  prediction.  be  ( r a t e .of s e l e c t i o n , p o p u l a t i o n  s i z e , breeding  more g e n e t i c d i v e r s i t y w o u l d b e  less genetic diversity.  so  large  a  upon w h i c h s e l e c t i o n a c t s  Nevertheless,  with  variance  A rigorous theoretical  a l s o h a v e g r e a t e r g e n e t i c v a r i a n c e , and  t h a n one  do. > E v e n g e n e t i c  not yet been produced.  p o p u l a t i o n w h i c h has to  will  i s of g e n e t i c d i v e r s i t y  act upon, whereas g e n e t i c v a r i a n c e e s t i m a t e s  Being  case  treatment  a l l other.<things system),  expected i n  a general  to respond f a s t e r to s e l e c t i o n  Similarly,  a population which  greater genetic variance  i n some c h a r a c t e r s  greater genetic variance  i n o t h e r f c h a r a c t e r s , w h i c h when s e l e c t e d w o u l d  show a g r e a t e r  c o u l d be  has  p r e d i c t e d to have  response.  Experimental  evidence  T h e r e i s ample e v i d e n c e f o r r e s p o n s e t o a r t i f i c i a l b r o a d s e n s e i n many o r g a n i s m s . animal  species  as  are  t o make t h e  domestication  f o r human p u r p o s e s h a s  i n w h a t a r e now relatives  The  selection i n a  of hundreds of p l a n t  i n almost every  case i n v o l v e d  the d o m e s t i c t a x a , sometimes t o the p o i n t where  unknown o r s o d i f f e r e n t  from t h e i r domesticated  o r i g i n s of the l a t t e r extremely  Unfortunately,  the s e l e c t i o n i n v o l v e d i n these,  domestications  has  difficult often  and  changes  feral  derivatives  to t r a c e .  prehistoric,  n o t b e e n d o c u m e n t e d i n a m a n n e r t o make t h e m . u s e f u l i n  -  this  study. Artificial  s h o u l d be attempt  s e l e c t i o n , that i s s e l e c t i o n under the  c o n s i d e r e d as two  separate kinds of process.  to d u p l i c a t e the processes  to  understand  by  t h e i r p h e n o t y p e i n one  w h a t i s g o i n g on i n n a t u r e ,  and  forming  t h e i r progeny.  second type  of a r t i f i c i a l  motivated  and  aimed at p r o d u c i n g  o f g e n o t y p e s i n c r o p p l a n t s and  isolate  be  first  them i n  the subsequent g e n e r a t i o n  from  selection i s economically  animals  i n the f a s t e s t  and m o s t  populations economical  o f many s e l e c t i o n  schemes  w i t h c a r e f u l breeding programs,  that p o r t i o n of the a v a i l a b l e g e n e t i c v a r i a b i l i t y which  inbreeding, s i b matings,  S p e c i a l breeding  techniques  back c r o s s e s , etc.)  and  (diallel  selection  to  represents crosses,  regimes  ( r e c u r r e n t s e l e c t i o n , progeny t e s t i n g , e t c . ) are u s u a l l y employed i n c r e a s e s e l e c t a b l e v a r i a t i o n and  s p e e d up  artificial  s e l e c t i o n which approximates  relatively  slower process.  The  an  individuals  p a r t i c u l a r s u p e r i o r genotypes or  used, i n combination  the s u p e r i o r g e n o t y p e ( s ) .  is  involves selecting  I n d i v i d u a l o r mass s e l e c t i o n i s o n l y one  w h i c h may  The  g e n e r a t i o n (mass s e l e c t i o n ) , b r e e d i n g  s y s t e m , and  The  c o n t r o l o f humans,  of n a t u r a l s e l e c t i o n , u s u a l l y i n order  some n a t u r a l m a t i n g  way.  two  to  s e l e c t i o n f o r economic reasons  obtained  f r o m p l a n t and  s e l e c t i o n s c h e m e s may To h e l p  types  of a r t i f i c i a l  breeding  a n i m a l b r e e d i n g s t u d i e s , and  s e l e c t i o n are  not  s e l e c t i o n experiments variability  we  require should i d e a l l y  w h e r e t h e r e i s an i n d e p e n d e n t e s t i m a t e  f o r the organism,  cases.  about s e l e c t i o n , g e n e t i c v a r i a b i l i t y ,  s y s t e m as p o s e d , t h e e v i d e n c e  where the organism  can  relatively natural  p r o d u c e e c o n o m i c a l l y v a l u a b l e r e s u l t s i n some  answer the q u e s t i o n s  -  natural selection i s often a  m u t u a l l y e x c l u s i v e , t h a t i s v a l u a b l e i n f o r m a t i o n about n a t u r a l s e l e c t i o n be  15  s t u d i e d has  of  and  come f r o m genetic  a known  s y s t e m , and w h e r e t h e i n i t i a l p o p u l a t i o n s u n d e r s e l e c t i o n h a v e n o t  breeding  been  16  -  b r e d t o change t h e i r n a t u r a l l e v e l s Inbreeding  an  outcrossed  species  of y a r l a b i l i t y ,  f o r example by  or crossing a s e l f e d species.  In addition,  f o r the purposes  of comparison to the study undertaken h e r e , the s e l e c t i o n  method s h o u l d be  c o m p a r a b l e (mass  selection).  I h a v e b e e n a b l e t o f i n d o n l y one e x p e r i m e n t w h e r e s e l e c t i o n f o r a c h a r a c t e r h a s b e e n p e r f o r m e d on two diversity or variance Marshall  of  genetic  f r o m an i n d e p e n d e n t s o u r c e a r e a v a i l a b l e .  Jain  and  ( 1 9 7 0 ) s e l e c t e d f o r two e x t r e m e s o f h e a d i n g d a t e and s e e d s i z e i n  A v e n a f a t u a and A. b a r b a t a . of g e n e t i c d i v e r s i t y variance  taxa f o r which estimates  i n other  i n b o t h c a s e s A.  T h e s e a r e two s p e c i e s  from isozymes  characters  f o r w h i c h measurements  ( M a r s h a l l and J a i n ,  ( J a i n and M a r s h a l l , 1967)  f a t u a h a s b e e n shown t o b e  1969)  and  genetic  a r e a v a i l a b l e , and  t h e more v a r i a b l e s p e c i e s .  f a t u a r e s p o n d e d b e t t e r t o s e l e c t i o n f o r b o t h c h a r a c t e r s , and t h i s a g r e e s w i t h t h e p r e d i c t i o n b a s e d on t h e i n d e p e n d e n t e s t i m a t e variability. comparisons  S e l e c t i o n response i s s u f f i c i e n t l y s u c h as t h i s  ubiquitous  a r e t h e o n l y ones o f r e a l v a l u e  of  A.  result  genetic  that careful  i n answering  this  question.  Breeding  s y s t e m and t h e r e s p o n s e t o s e l e c t i o n  Theoretical  Can by  considerations  the response to s e l e c t i o n f o r a p a r t i c u l a r  the breeding  can o n l y a f f e c t  system of the organism being  selected?  Breeding  the response t o s e l e c t i o n through i t s e f f e c t  variance present outlined earlier, difficult  c h a r a c t e r be  i n the p o p u l a t i o n .  As we  the e f f e c t of breeding  predicted system  on t h e  genetic  have seen i n the d i s c u s s i o n  s y s t e m on g e n e t i c v a r i a n c e i s  to p r e d i c t i n theory, but the evidence i n d i c a t e s that s e l f e d taxa  contain less genetic diversity  than outcrossed  taxa.  The  evidence f o r  differences i n genetic variance breeding  with different  systems i s e q u i v o c a l . "  Inbreeding variance  i n an i n f i n i t e l y  relative  selection w i l l variance w i l l population, having  between p o p u l a t i o n s  large population w i l l  t o an o u t c r o s s e d  population,  and s e l e c t i o n response w i l l  been reached).  the genetic  and r e s p o n s e t o d i r e c t i o n a l  thus t h e o r e t i c a l l y be f a s t e r i n i t i a l l y . t h e o r e t i c a l l y be d e p l e t e d  increase  However,  genetic  more q u i c k l y i n t h e i n b r e d cease e a r l i e r  I f i n a f i n i t e population  ( the s e l e c t i o n l i m i t  the s e l e c t i o n pressure i s  h e a v y e n o u g h , i t i s p o s s i b l e t h a t t h e s e l e c t i o n l i m i t may b e f a r t h e r f r o m t h e mean o f t h e o r i g i n a l p o p u l a t i o n inbred the  one, as l o s s o f a l l e l e s  inbreeder  i n an o u t c r o s s e d  population  t h a n i n an  t h r o u g h h o m o z y g o s i s and random d r i f t i n  i n e a r l y generations  may p r e v e n t s e l e c t i o n o f t h e o p t i m a l  genotype.  Experimental  The on  evidence  evidence required t o d i s t i n g u i s h the e f f e c t of breeding  the response to s e l e c t i o n should  ideally  come f r o m t h e same t y p e o f  e x p e r i m e n t s as o u t l i n e d e a r l i e r u n d e r g e n e t i c v a r i a b i l i t y selection  and r e s p o n s e t o  ( p . 1 5 ) . T h e a v a i l a b l e e v i d e n c e comes m o s t l y f r o m p l a n t  s t u d i e s , and h a s t h e a t t e n d a n t "populations"  being  shortcomings i n t h i s  an o u t c r o s s e d  breeding  to i n c r e a s e v a r i a b i l i t y .  of s e l e c t i o n o t h e r  breeding  Most of t h e population  t h a t i s , even s p e c i e s which have  system have u s u a l l y been i n b r e d , o f t e n h i g h l y  n a t u r a l l y selfed species  selection i n plants  context.  selected are not representative of a natural  I n terms o f l e v e l s o f g e n e t i c v a r i a b i l i t y ;  and  systems  may h a v e b e e n o u t c r o s s e d  inbred,  a number o f ways  Most w e l l documented e v i d e n c e o f r e s p o n s e t o  comes f r o m p l a n t b r e e d i n g t h a n mass s e l e c t i o n .  s t u d i e s w h i c h u s e some  And, o f c o u r s e ,  regime  comparisons between  r-  c l o s e l y r e l a t e d t a x a of d i f f e r e n t b r e e d i n g is  f o r c e d t o d e a l w i t h e x p e r i m e n t s on p l a n t s w i t h p a r t i c u l a r  s y s t e m s as  a  The the  70 Zea  best  e x a m p l e o f l o n g t e r m mass s e l e c t i o n i n an o u t c r o s s e d  Dudley e t a l . (1974).  protein The  and  14%  generations, with  low  t h e means o f  o i l strains i n generation  grain yield  1974), increased y i e l d resistance  C28%  germination and  i n 10  (36%  (18% i n 6 c y c l e s )  (20% i n 4 c y c l e s ) cycles)  i n 4 cycles)  decreased ear  length  Another outcrossed  70 b e i n g  s p e c i e s w h i c h has  and  (Busbice  2^5  cycles) saponin  increased levels  (300%  Compton, earworm  cold  been the s u b j e c t  increased  of s u c c e s s f u l  R e s p o n s e has (38%  been  observed  in 4  cycles)  ( 7 7 % i n 2 c y c l e s ) and  et a l . , 1975), (73% i n 3  i n 2-3  of  1979).  ( V i l l e g a s et a l . / 1971), r e s i s t a n c e t o anthracnose (67% e t a l . , 1 9 7 1 ) , and  and  c y c l e s ) and  (Pedersen e t a l . j 1973).  23%,  also  i n 6 cycles  G a r d n e r , 1 9 7 9 ) , and  resistance to b a c t e r i a l w i l t  i n 2 cycles)  mays h a s  (Gardner, 1961), increased  (Barnes e t al.," 1971), i n c r e a s e d s e l f - s t e r i l i t y (103%  (24%  ( C o r t e z - M e n d o z a and H a l l a u e r ,  s e l e c t i o n for increased  fertility  Zea  (Zuber e t a l . , 1971), i n c r e a s e d (McConnell  significant  r e s p e c t i v e l y 215%,  (Arboleda-Rivera  mass s e l e c t i o n e x p e r i m e n t s i s M e d i c a g o s a t i v a . to  populations  t o show a  o f t h e means o f t h e o r i g i n a l p o p u l a t i o n .  and  is  the h i g h p r o t e i n , low p r o t e i n ,  been s u c c e s s f u l l y s e l e c t e d f o r i n c r e a s e d p r o f l i c a c y selection)  taxon  concentration  four  f o r extremes i n c o n c e n t r a t i o n have continued  o i l , and  341%,  e x p e r i m e n t s e l e c t i n g f o r o i l and  mays, summarized by  r e s p o n s e f o r 70 high  breeding  taxa  generation  selected  one  group.  Outcrossed  in  systems- a r e s c a r c e , s o  18  cycles)  i n 3 cycles)  decreased  self-  (66%  (Devine in  - 19 I n Ipomoea b a t a t a s  mass s e l e c t i o n h a s p r o d u c e d  of decreased o x i d a t i o n o f the root complex  c o m p o s e d o f a number o f e c o n o m i c a l l y  et a l . , 1976). selected  (1968)  o f s e e d s i z e (+7% i n o n e c y c l e )  f o r extremes Brassica hjrta  content  (+16%, - 1 4 % i n 8 c y c l e s )  (Sinapis alba)  characters  i na Clones  has s u c c e s s f u l l y and i n c r e a s e d  seed  has been s e l e c t e d f o r extremes and Andersson, 1 9 6 3 ) .  (Olsson  al.,  1972).  content  by d i r e c t i o n a l s e l e c t i o n (+0.3%, -10% i n 3 cycles) B e t a v u l g a r i s has been s e l e c t e d f o r extremes (+35%, - 4 0 % i n 1 3 c y c l e s )  i n the root  1979).  species  var.  (Murty e t  of dry matter 1963).  Limnanthes  t o two c y c l e s o f s e l e c t i o n f o r f l o w e r i n g t i m e ( + 1 3 % ,  a l b a has responded (Jain,  (Josefsson,  of o i l  Extremes  f l o w e r i n g time were s u c c e s s f u l l y s e l e c t e d i n B r a s s i c a campestris  brown s a r s o n  This  i s one s i t u a t i o n where a c l o s e l y r e l a t e d  ( L . f l o c c o s a ) e x i s t s and h a s been s t u d i e d  v a r i a b i l i t y , but unfortunately it  1 9 7 2 ) and changes  valuable  I n Agropyroh deseftorum Schaaf  yield.  of  fles-h (Jones,  response i n terms  ?.11%)  inbreeding  for levels of genetic  no s e l e c t i o n e x p e r i m e n t s h a v e b e e n done on  yet.  Inbreeding  There taxa.  taxa  a r e a number o f s t u d i e s o f r e s p o n s e t o mass s e l e c t i o n i n i n b r e e d i n g  I n Avena s a t i v a , response h a s been observed t o s e l e c t i o n f o r i n c r e a s e d  panicle weight plant height  (15% i n 2 c y c l e s )  (2 inches  grain yield  i n 4 cycles)  and F r e y ,  (Romero a n d F r e y ,  1973),  (+9%), width; of seed  reduced  1 9 6 6 ) , and t o one  s e l e c t i o n f o r heading date (+22%), p l a n t height  cycle of divergent -4%),  (Chandhanamutta  (+5%, - 3 % ) , seed w e i g h t  (+5%,  (+5%, - 3 % ) ,  and number o f s p i k e l e t s p e r p a n i c l e ( + 5 % , - 1 % ) ( G e a d e l m a n n and F r e y , I n Avena f a t u a s u c c e s s f u l d i v e r g e n t habit  (+13%,  -31%),  flowering  time  s e l e c t i o n has produced (+13%,  -28%),  and h e i g h t  changes t+10%,  1975).  i n growth -15%) i n  one  c y c l e (Imam and  and  i t s m o r e h i g h l y s e 1 f e d r e l a t l v e ' A, B . a r b a t a h a v e b e e n s e l e c t e d  increased 19 7 0 ) . in  and  Allard,  3 c y c l e s ) and  has  specific  s e e d w e i g h t (+34%, - 1 8 % ) ,  increased of  18%  of the  green weight of  genetics  intensity  barley.  germination E.  and  that negative  animal,  and  time  t a b a c u m r e s u l t e d i n an  increase  A l l a r d e t a l . (1968) i n t h e i r  review  report successful selection for  i n 4 c y c l e s ) , P.  and  extremes  of  v u l g a r i s (+4.5% i n 4  deWet ( 1 9 8 0 ) w e r e a b l e  f o r nearly every character i n both breeding  to  cycles)  increase species,  every  studied,  enough  system groups f o r a  p o t e n t i a l problem which should  results (in this  reported  flowering  mean  E. t r i s t a c h y a .  i s present One  -4%  be  mentioned i s  case, l a c k of response t o a r t i f i c i a l  i n - the l i t e r a t u r e . . Given the  response  investment i n time  selection) and  i n v o l v e d i n most c a r e f u l s e l e c t i o n e x p e r i m e n t s , t h i s i s p r o b a b l y  f a c t a p r o b l e m , and  outcrossed number o f and  and  case w i t h s e l e c t i o n experiments i n n e a r l y  to s e l e c t i o n to occur.  in  species  7.5%  changed the  20-100% i n 4 c y c l e s of s e l e c t i o n i n t h r e e  been the  genetic v a r i a b i l i t y  effort  (+  c o r a c a n a , and  organism, p l a n t or  Marshall,  F o u r c y c l e s o f mass s e l e c t i o n f o r  i n Njcotiana  I n E l e u s i n e , H i l u and  i n d i c a , B.  n o t be  leaves  (+31%, - 2 6 % ) ,  c o l o u r i n seeds of Phaseolus l u n a t u s ,  r a t e s by  As h a s  may  plant height  Wernsman; 1 9 6 8 ) .  lunatus  for  and W e b e r , 1 9 6 8 ) .  c y c l e s i n Sorghum b i c o l o r has  of inbreeding  of coat  s e e d s i z e i n P. and  g r a v i t y of seeds (Fehr  ( F o s t e r e t a l . , 1980).  (Matzinger  h e a d i n g d a t e ( J a i n and  f atua  been s e l e c t e d f o r e x t r e m e s o f s e e d s i z e (+10%,  s e l e c t i o n f o r 10  ( + 1 0 % , -2%)  As n o t e d e a r l i e r , b o t h A.  d e c r e a s e d s e e d s i z e and  G l y c i n e max  Divergent  19_65) .  and  A. b a r b a t a ,  i t appears from the evidence examined here t h a t  s e l f e d t a x a show c o n s i d e r a b l e  characters.  20  I t i s only  response to s e l e c t i o n f o r  from s t u d i e s  s u c h as  w h i c h comes c l o s e t o m e e t i n g t h e i d e a l  t h a t w i t h Avena conditions  l y n a t u r a l l e v e l s of g e n e t i c v a r i a b i l i t y , n a t u r a l breeding  of  systems,  not both a fatua  relativeand  - 21 mass s e l e c t i o n ,  Breeding  t h a t t h e m o s t u s e f u l c o m p a r i s o n s may  system, genetic v a r i a b i l i t y ,  and  be  drawn.  the response to s e l e c t i o n  in  Plectritis  The  o b j e c t i v e of t h i s  artificial mainly  of  this  could r e f l e c t  two'species closely  and P.  study were the  brachystemon.  Morey ( 1 9 6 2 ) ,  amount and  two  / or o r g a n i z a t i o n  f o r t h i s purpose.  i n the most r e c e n t  them s u b s p e c i e s  o f P_^ c o n g e s t a .  even given  them t h a t r a n k ,  c o n s i d e r i n g t h e m one  Cronqui^t,  19 7 3 ) .  species  species  of  Plectritis,  T h e r e a r e a number o f f e a t u r e s o f  considered  The  differ  variability.  w h i c h make t h e m i d e a l  related.  of p l a n t s which  divergent  I f d i f f e r e n c e s i n s e l e c t i o n response were  d i f f e r e n c e s i n the  p l a n t s chosen f o r t h i s  congesta  t o examine the responses t o  natural populations  system.  the u n d e r l y i n g g e n e t i c The  P.  s e l e c t i o n o f two  i n t h e i r breeding  observed,  s t u d y was  are very  The  treatment  Hitchcock  and  species  difficult  two  the  species  are  of the  genus,  o t h e r s have  (Hitchcock  to d i s t i n g u i s h  very  not  and  before  they have f l o w e r e d , s i n c e they have n e a r l y i d e n t i c a l v e g e t a t i v e h a b i t . Populations  of the  when a l l o p a t r i c  two  they  g r o w s y m p a t r i c a l l y i n a number o f v l o c a t i o n s , and  o c c u p y t h e same t y p e  e d a p h i c a l l y d r y s u b s t r a t e s on slopes and  and  coastal bluffs  and  headlands,  I t i s s a f e t o assume t h a t t h e l a r g e s c a l e  and  Nevertheless,  s p e c i e s f o r many  the p o p u l a t i o n s  of t h e  Columbia are q u i t e d i s t i n c t ,  morphological  characters  two  annual  differed  generations. species which occur  d i f f e r i n g i n a' number o f  ( f l o w e r c o l o u r and  open  selective  t h a t they have encountered i n terms of h a b i t a t have not  s i g n i f i c a n t l y b e t w e e n t h e two  British  of h a b i t a t s , that i s , t h i n ,  c l e a r i n g s i n l a n d , w i t h t h e same c o m m u n i t y o f a s s o c i a t e d  p e r e n n i a l herbs.  pressures  rocky  even  size,  in  floral  degree o f " p t o t a n d r y ,  nectar  - 22 production) Plectritis measured  which also r e f l e c t  system d i f f e r e n c e .  c o n g e s t a i s l a r g e l y c r u t c r o s s e d , w i t h a mean o u t c r o s s i n g r a t e  i n a number o f p o p u l a t i o n s a n d o v e r a number o f s e a s o n s o f 7 0 % ;  P. b r a c h y s t e m o n 2%  their basic breeding  i s h i g h l y s e l f e d , w i t h a mean o u t c r o s s i n g r a t e o f l e s s  ( C a r e y and Ganders, 1980; Ganders  e t a l . , 1977a.,  1977b.; L a y t o n ,  than  1980).  I n a d d i t i o n , t h e two s p e c i e s h a v e p r o v e d t o b e i n t e r s t e r i l e i n l a b o r a t o r y c r o s s e s , a n d no i n t e r m e d i a t e  f o r m s h a v e b e e n o b s e r v e d i n a number o f  l o c a t i o n s w h e r e t h e two g r o w s y m p a t r i c a l l y . b i o l o g i c a l d i f f e r e n c e between  In effect,  t h e two s p e c i e s  the only  major  appears t o be t h e i r  breeding  system. B o t h s p e c i e s a r e s m a l l , r e l a t i v e l y e a s y t o grow i n crowded in  greenhouses  o r c o n t r o l l e d environment chambers,  conditions  and c o m p l e t e t h e i r  life  c y c l e , s e e d t o s e e d , w i t h i n 5 months under s u i t a b l e c o n d i t i o n s . In a d d i t i o n , independent estimates f o r t h e two s p e c i e s determine l e v e l s populations  f r o m two s t u d i e s .  o f w i t h i n ; and between  of both species  of genetic v a r i a b i l i t y Isozyme  data has been analysed t o  p o p u l a t i o n d i v e r s i t y i n a number o f  ( L a y t o n , 1980) i  Morphometric c h a r a c t e r s o f t h e f r u i t s have a l s o been examined of each s p e c i e s  areavailable  (Ganders and M a z e , . u n p u b l i s h e d ) .  i n populations  Materials  Source  and  Methods  populations  The  seed f o r the base p o p u l a t i o n s  populations  Cone o f e a c h s p e c i e s )  P a r k n e a r V i c t o r i a on s o u t h e r n Both l o c a l populations open h i l l s i d e s P.  congesta,  wet  more o r l e s s  i n w i n t e r and  c a s e o f P.  e d a p h i c a l l y d r y by and  50  t h r e e p l a n t s o f P.  - 75%  of the  Columbia,  fruit  congesta  and  i n J u n e 1977.  590  case  and  The  patches  e a r l y summer, w i t h  Cytisus.  and  peren-  Nine hundred  p l a n t s o f P_ b r a c h y s t e m o n w e r e  These numbers p r o b a b l y  their  The  represent  extent  of  two  l o c a l populations  The  numbers o f f r u i t s p e r p l a n t i n t h e p o p u l a t i o n s v a r i e d f r o m 1 o r 2 from each p l a n t .  c o l l e c t e q u a l numbers o f f r u i t s  f r o m e a c h p l a n t , and  P.  to  w i n g e d and  separately. fruited.  The  I made no e f f o r t  Frequencies  f r u i t e d p l a n t s were recorded, i n ^ determine outcrossing r a t e .  the  o v e r l a p i s diagrammed i n F i g u r e  many; a l l f r u i t s w e r e c o l l e c t e d  s p e c i e s were lumped i n b u l k s a m p l e s .  the  of  brachystemon.  t o t a l numbers i n the l o c a l p o p u l a t i o n . collected  Canada.  covering  herbaceous w i n t e r annuals and  two  Hill  open, rocky h i l l s i d e s w i t h  n i a l s under s c a t t e r e d ' Quercus garryana,'Arbutus,  i n late  came f r o m  continuously i n the  i n the  a community o f g r a s s e s , b r y o p h y t e s ,  collected  species  Vancouver I s l a n d , B r i t i s h  i n i s o l a t e d pockets  of shallow s o i l ,  two  a r e p a r t o f more e x t e n s i v e p o p u l a t i o n s  i n the park,  but  of the  growing s y m p a t r i c a l l y i n M i l l  h a b i t a t i s t y p i c a l f o r the s p e c i e s :  sixty  23  congesta  fruits  to  from each  o f w i n g e d and. w i n g l e s s  f o r use wingless  A l l p l a n t s o f P.. b r a c h y s t e m o n a t t h i s  to  i n a progeny  test  f r u i t s were  bulked  locality  are  wingless  1.  - 25 Growing c o n d i t i o n s  A l l p l a n t s i n the experiment flats. soil.  were grown i n s t a n d a r d  F r u i t s w e r e p l a n t e d 1 cm deep i n a p p r o x i m a t e l y  soil prior within  Fertilizer  ( H i - S o l 20-20-20).. was a d d e d t o t h e  i n nutrient levels.  generations  (Table I ) .  A l l e x p e r i m e n t a l p o p u l a t i o n s were grown i n a s i n g l e  temperature  i n a cold  chamber, and t h e n  were i n c r e a s e d as t h e p l a n t s m a t u r e d . varied slightly  The l i g h t  light  f o r manipulation  and  light  temperature  and t e m p e r a t u r e  f r o m g e n e r a t i o n t o g e n e r a t i o n as I a t t e m p t e d  compromise between a s h o r t g e n e r a t i o n time  suited  The c o n d i t i o n s o f  w e r e s e t as much as p o s s i b l e t o s i m u l a t e n a t u r a l c o n d i t i o n s ;  the p l a n t s were germinated  best  levels i n the early  c a u s e d e x c e s s i v e g r o w t h , w h i c h made t h e p l a n t s d i f f i c u l t t o  C o n v i r o n w a l k - i n c o n t r o l l e d e n v i r o n m e n t chamber. and  of heterogeneity  The amount o f f e r t i l i z e r  a d d e d v a r i e d f r o m g e n e r a t i o n t o g e n e r a t i o n , as h i g h e r  handle  o f 10 r o w s a n d 20  t o p l a n t i n g , t o remove some p o s s i b l e s o u r c e s  and b e t w e e n f l a t s  plastic  4 cm o f s t e a m t r e a t e d  T h e f r u i t s w e r e p l a n t e d 200 t o a f l a t i n a g r i d  c o l u m n s s p a c e d 2.5 cm a p a r t .  25 x 50 cm  conditions  to find the  and a p l a n t h a b i t  best  ( s h o r t , s t o c k y p l a n t s w i t h a s t r o n g r o o t system)  (Table I) . Positions and  of the f l a t s  i n t h e g r o w t h chamber w e r e a s s i g n e d  t h e f l a t s were s h u f f l e d s e v e r a l times  position effects.  a t random  d u r i n g e a c h g e n e r a t i o n t o remove  A l l f l a t s were w a t e r e d t o s a t u r a t i o n d a i l y w i t h t a p  water u n t i l  f r u i t s e t was c o m p l e t e ,  as t h e s o i l  dried.  and t h e p l a n t s were t h e n a l l o w e d  tod i e  Measurements  A l l p l a n t s i n each treatment  p o p u l a t i o n and e v e r y  g e n e r a t i o n were  Table I . Generation  G  Growing  conditions  Fertilizer (gm/flat)  Temperature ( C n i g h t / C day)  Light (hr dark/hr  8  7/12 10/15  - 39 d a y s - balance  8/16  8  7/12 10/15  - balance  -  4  7/12 10/15  4  7/12 10/15 12/20 12/23  2  7/12 10/15 10/18 11/20  0  2  7/12 10/15 11/20  39  days  8/16  - balance  42  days  8/16  -  33 d a y s 38 d a y s 64 d a y s balance  8/16  _  28  days days 18 d a y s balance  8/16  28 d a y s 8 days balance  8/16  — 12  —*  Notes light) - g r o w t h c h a m b e r o u t o f o p e r a t i o n day 82 day 89, p l a n t s a t room t e m p e r a t u r e - s p r a y e d f o r a p h i d s ( I s o t o x ) d a y 103  -sprayed  f o r mildew  -intensity d a y 79  of l i g h t  (Benomyl) day  d u r i n g day  39  increased  measured f o r t h e f o l l o w i n g 1,  characters;  Days t o emergence  The n u m b e r o f days- b e t w e e n p l a n t i n g a n d t h e c o m p l e t e e m e r g e n c e the  cotyledons 2,  Days  above t h e s o i l to anthesis  s u r f a c e was  (flowering  flower  o n e a c h p l a n t was  3,  Height at  The h e i g h t  time)  recorded.  o f t h e p l a n t i n mm, (Figure  Number o f n o d e s a t  from the s o i l  2) was  anthesis.  day o f  surface  recorded f o r each p l a n t  on t h e f i r s t  on t h e m a i n a x i s on t h e f i r s t  anthesis  day o f a n t h e s i s  was  u n d e r e s t i m a t e o f t h e t o t a l amount o f b r a n c h i n g , b r a n c h e s , as w e l l as s e c o n d a r y , t e r t i a r y , do n o t b e g i n t o d e v e l o p u n t i l  P.  recorded.  as t h e r e  and h i g h e r  of  This  leaves i s an  a r e some p r i m a r y  order  l a t e r i n the flowering period  branches, which (Figure 2).  production  The r i p e f r u i t s w e r e  error;  highly  node.  Number o f p r i m a r y b r a n c h e s a t  Fruit  day o f  t h e nodes were counted by i d e n t i f y i n g p a i r s o f  The number o f b r a n c h e s o r b r a n c h b u d s v i s i b l e i n t h e a x i l s  6,  anthesis.  and t h e b a s e o f t h e m a i n  I n P. b r a c h y s t e i i t o n , i n w h i c h t h e u p p e r n o d e s a r e s t i l l  a t each  5,  t o the top of  anthesis  ( i n c l u s i v e ) was  compressed a t a n t h e s i s , leaves  surface  r e c o r d e d on t h e f i r s t  The number o f n o d e s b e t w e e n t h e s o i l inflorescence  first  anthesis  the main i n f l o r e s c e n c e 4,  of  recorded.  The number o f d a y s b e t w e e n p l a n t i n g and t h e o p e n i n g o f t h e  plant  27  and c o u n t e d .  This  f r u i t s , when r i p e ,  congesta requires  c o l l e c t e d from t h e main i n f l o r e s c e n c e of each figure i s subject  t o a l a r g e amount o f  are e a s i l y dislodged  artificial  from t h e p l a n t  experimental  and l o s t ,  p o l l i n a t i o n to produce f r u i t w e l l i n the  l a b o r a t o r y , so unavoidable v a r i a t i o n i n p o l l i n a t i o n l e v e l s w i l l  have  and  F i g u r e 2.  M o r p h o l o g y of  Plectritis,  affected fruit  s e t i n this- species:,  7.  F r u i t phenotypic  The  fruit  characters. f o r these  characters  f r o m e a c h p l a n t was  F r u i t s o f P.  characters.  colour  I n P.  ( b o d y and  scored  f o r a number o f  congesta, see  fruits  Figure  wings scored  c o u l d be  I  f o r wing  s e p a r a t e l y on  t h e b a s i s o f an  4),  arbitrary  the presence i n winged  of a c h a r a c t e r i s t i c i n d e n t a t i o n i n the margin of the f r u i t ' w i n g .  attempted to record  b e t w e e n p l a n t s and h o w e v e r , was s y s t e m and  too  not  the  shape of the  relatively  continuous  anomalous c h a r a c t e r s  f r u i t wing, which v a r i e d  l i t t l e within plants.  and  a m e n a b l e t o any  I n a d d i t i o n to these and  scored  case)  3 ) , pubescence p a t t e r n ( F i g u r e  c o l o u r c l a s s i f i c a t i o n u s i n g 4 c o l o u r c l a s s e s ) , and fruits  phenotypic  brachystemon were a l l monomorphic ( i n t h i s  phenotype (winged or w i n g l e s s , fruit  29  s i m p l e -measurement.  including:  i n the  cotyledons,  flowers with  cotyledons,  patterns  and  other  abnormalities i n flowering  anthers  abnormal numbers of p a r t s  c o r o l l a l o b e s , more t h a n t h r e e s t a m e n s ,  Breeding  sporadic  chlorotic seedlings, excessively  a d u l t g r o w t h h a b i t , and  c h a r a c t e r i s t i c s , m o s t commonly a b o r t e d w e l l as  various other  a b e r r a t i o n s i n t h e number o f  d a r k l y pigmented s e e d l i n g s , abnormal branching abnormalities  variation,  c o m p l e x t o a l l o w f o r an a d e q u a t e s c o r i n g  characters, I recorded  p r e s e n c e o f more o r l e s s f u s e d  The  considerably  and  l a c k o f g o o d p o l l e n , as  ( f o r e x a m p l e , more t h a n 5  etc.).  procedure  Three groups of p o p u l a t i o n s a combination  of species  and  were i n v o l v e d i n the e x p e r i m e n t , based  breeding  procedure.  Plectritis  r e q u i r e d m a n u a l p o l l i n a t i o n b e c a u s e i t i s p r o t a n d r o u s and  congesta  does  not  on  F i g u r e 3.  P l e c t r i t i s - f r u i t wing  Wingless  phenotypes.  ventral view-  d o r s a l view  - 32 a u t o m a t i c a l l y self-poll£nate s u c c e s s f u l l y i n t h e g r o w t h c h a m b e r , took one  advantage o f t h i s outcrossed  self-pollinated The  t o s e t u p two g r o u p s o f P^.-"congesta p o p u l a t i o n s ,  a n d one s e l f e d . or crossed  success  progenies  either  to r e l a t i v e l y unrelated plants (not siblings).  and u s i n g them t o p o l l i n a t e  of t h i s breeding  self-pollinates  with fine  appropriate  forceps  stigmas.  p r o c e d u r e was e v a l u a t e d b y e x a m i n i n g  i n subsequent generations.  protandrous, in  The p l a n t s i n each p o p u l a t i o n were  p o l l i n a t i o n was d o n e b y r e m o v i n g n e w l y o p e n e d a n t h e r s  from the p o l l e n parent, The  I  particular  P l e c t r i t i s brachystemon i snot  a u t o m a t i c a l l y , and s e t s f r u i t v e r y s u c c e s s f u l l y  t h e g r o w t h chamber; i t i s n o t e a s y t o o u t c r o s s , b e c a u s e o f t h e s m a l l  s i z e of the flowers.  F o r these  reasons only s e l f e d populations  brachystemon were i n v o l v e d i n t h e  Selection  The  o f P_.  experiment.  procedure  s e l e c t i o n m e t h o d was s i m p l e  i n d i v i d u a l o r mass s e l e c t i o n , i n w h i c h  c e r t a i n i n d i v i d u a l s o f one g e n e r a t i o n w e r e s e l e c t e d o n t h e b a s i s o f t h e i r phenotype t o produce seed f o r t h e next was a p p r o x i m a t e l y  The s e l e c t i o n  pressure  9 0 % , t h a t i s 20 p l a n t s w e r e s e l e c t e d f r o m t h e 200 i n a  p a r t i c u l a r p o p u l a t i o n t o form t h e next separately f o r short height  f o r each s p e c i e s group.  generation.  L i n e s were s e l e c t e d  at anthesis, t a l l height at anthesis, early  a n t h e s i s , and l a t e a n t h e s i s .  An u n s e l e c t e d  c o n t r o l l i n e was a l s o  One f l a t was p l a n t e d w i t h t h e l a s t  c o n t a i n i n g 100 i n d i v i d u a l s served  generation.  of each species  from t h e source  maintained  generation, populations;  as an e x t e r n a l c o n t r o l t o changes w h i c h might have a f f e c t e d t h e  i n t e r n a l , unselected P. c o n g e s t a  G,. s o u r c e  control lines.  These p o p u l a t i o n s  a n d P. b r a c h y s t e m o n G,. s o u r c e .  are designated  this  Base  population  The f i r s t  generation, base populations  o f 200 i n d i v i d u a l s , (PCO) , -P, c o n g e s t a  3 each f o r the 3 species selfed  e a c h g r o u p t h e r e was height population.  (PCS),  (G ) Q  c o n s i s t e d o f 9. p o p u l a t i o n s  groups:  P.  congesta  a n d P. b r a c h y s t e m o n s e l f e d  frequencies equal wingless,  from which the base p o p u l a t i o n s were  fruits  to their  i n t h e PCO  grown  populations.  a n d PCS p o p u l a t i o n s w e r e p l a n t e d i n  frequencies i n the source  population  (12.5%  87.5% w i n g e d ) .  First  cycle of s e l e c t i o n  P r o m t h e b a s e p o p u l a t i o n s , 20 p l a n t s w e r e s e l e c t e d a s p a r e n t s g e n e r a t i o n , G^.  of 200.  For  a c o n t r o l p o p u l a t i o n , an a n t h e s i s p o p u l a t i o n , a n d a The f r u i t s  Winged and w i n g l e s s  outcrossed  (PBS).  w e r e s e l e c t e d a t random f r o m t h e b u l k s a m p l e f r o m t h e s o u r c e  next  Ten f r u i t s  Selection lines  t h e 20 e a r l i e s t as- p a r e n t s .  from each were taken  f o r e a r l y and l a t e  and l a t e s t  f o r the  t o form a p o p u l a t i o n  a n t h e s i s were begun by t a k i n g  f l o w e r i n g p l a n t s i n t h e G^ a n t h e s i s  S i m i l a r l y , s h o r t and t a l l  height population.  population  l i n e s w e r e s e l e c t e d f r o m t h e GQ  T w e n t y p l a n t s w e r e s e l e c t e d a t r a n d o m f r o m t h e GQ  c o n t r o l p o p u l a t i o n t o f o r m t h e G^ c o n t r o l p o p u l a t i o n .  T h u s t h e r e w e r e 15  treatment  as i n d i c a t e d i n  Figure  33  populations  i n G^ a n d s u b s e q u e n t g e n e r a t i o n s  5.  Subsequent c y c l e s of s e l e c t i o n  I n each generation  f r o m G^ o n , t h e 20 e a r l i e s t ,  latest,  s h o r t e s t , and . /- •  t a l l e s t p l a n t s were s e l e c t e d i n t h e r e s p e c t i v e p o p u l a t i o n s  as p a r e n t s f o r  F i g u r e 5.  Experimental populations-maintained o f s e l e c t i o n , G.. t o G .  P.  congesta  through 5  generations  P. brachystemon  PCO  PCS  PBS  Control  NF=200  N=200  N==200  Early anthesis  N=200  N=200  N=200  Late anthesis  N=200  N=200  N=200  Short height  N-200  N=200  N-200  Tall height  N=200  N=200  N=200  34  the subsequent g e n e r a t i o n . ' A g a i n ,  the  by- s e l e c t i n g p l a n t s a t r a n d o m f r o m t h e i n PCO  continued  control populations,  i n a l ls e l e c t i o n s  t h e p o l l i n a t i o n s w e r e made, as f a r as p o s s i b l e , b e t w e e n s e l e c t e d  individuals  of d i f f e r e n t  produced before  families.  a plant qualified  The  f l o w e r i n g time  requirement  as a p a r e n t  some i n d i v i d u a l s w h i c h w o u l d o t h e r w i s e their  c o n t r o l l i n e s were  t h a t 10  fruits  f o r s e l e c t i o n meant  be that  h a v e b e e n s e l e c t e d on t h e b a s i s there  was  s e l e c t i o n f o r a minimum l e v e l o f f e c u n d i t y i n a d d i t i o n t o s e l e c t i o n  for  height  and  or h e i g h t were d i s q u a l i f i e d .  f l o w e r i n g time.  I n G^  s h o r t h e i g h t p r o d u c e d t o o few minimum f e c u n d i t y l e v e l , case.  f r u i t s per  so I had  Thirty-seven individuals  selected to contribute families next  generation  Progeny t e s t  The  t o g e t h e r w i t h the observed  f r o m PCS  populations  selected for  i n d i v i d u a l to even reach  s h o r t and  of v a r y i n g s i z e  35  f r o m PBS  the this  s h o r t were  ( 1 - 10 p r o g e n y ) t o  the  (GQ)  and  congesta  phenotype frequencies i n the source  population,  f r e q u e n c i e s o f w i n g e d and w i n g l e s s m o r p h s i n  allowed  a p r o g e n y t e s t w h i c h g a v e an e s t i m a t e  o u t c r o s s i n g r a t e , t , i n the source  population  of  the  (Ganders e t a l . , 1977a.).  analyses  A l l measured or s c o r e d p u n c h e d on  PBS  ,to r e d u c e t h e f a m i l y s i z e o f 10 i n  o u t c r o s s i n g r a t e i n P.  w i n g e d and w i n g l e s s  Data treatment  and  G^.  and  t h e i r progenies  t h e PCS  In effect,  of  computer cards  characters i n every  and  stored i n f i l e s  Columbia computer system f o r a n a l y s i s .  l i n e and  generation  i n the U n i v e r s i t y of  Most s t a t i s t i c a l  p e r f o r m e d u s i n g t h e MIDAS s t a t i s t i c a l p a c k a g e ( F o x  and  analyses  Guire,  were British  were  1976).  Metrical  characters  I u s e d t h e s i x m e t r i c a l c h a r a c t e r s - days t o emergence, days anthesis, height  a t a n t h e s i s , number o f n o d e s a t a n t h e s i s , number o f  p r i m a r y b r a n c h e s a t a n t h e s i s , and set of s i x transformed  f r u i t p r o d u c t i o n - t o compute a f u r t h e r  c h a r a c t e r s as  follows.  The  d e v i a t i o n o f e a c h w e r e c o m p u t e d f o r a l l s i x P. t o g e t h e r , and  to  g r a n d mean and  cOrigesta  standard  populations  f o r a l l t h r e e P., b r a c h y s t e m o n G ^ p o p u l a t i o n s t o g e t h e r .  data f o r subsequent generations, a l l populations w i t h i n a p a r t i c u l a r group were t r a n s f o r m e d  by  a multiplicative  the d i s t r i b u t i o n of the transformed p o p u l a t i o n had  t h e same mean and  An e x a m p l e i s g i v e n i n F i g u r e 6. the  f o l l o w i n g two  otherwise 1.  the  and  an a d d i t i v e  c h a r a c t e r i n the  standard  f a c t o r , so  control  This  transformation effectively  sources of v a r i a t i o n  from the d a t a , which would  o t h e r e n v i r o n m e n t a l f a c t o r s , and  uncontrolled s e l e c t i o n pressures g r o w t h c h a m b e r c o n d i t i o n s ) and w h i c h c o u l d be  p r e s u m e d t o be  that  d e v i a t i o n as t h e GQ s t a n d a r d .  common e f f e c t s o f g e n e r a t i o n t o g e n e r a t i o n f l u c t u a t i o n s and  species  (unselected)  i n t e r f e r e w i t h the i n t e r p r e t a t i o n of the e x p e r i m e n t a l  conditions  In  2.  the e f f e c t s  removes  results: i n growing of  any  ( f o r example, s e l e c t i o n f o r growth under  t o some e x t e n t  the e f f e c t s of i n b r e e d i n g  a c t i n g e q u a l l y on s e l e c t e d and  unselected  lines.  Descriptive  The  statistics  distributions  o f t h e m e t r i c a l c h a r a c t e r s , raw. and  w e r e d e s c r i b e d i n a l l p o p u l a t i o n s i n t e r m s o f number o f m e a s u r e d , maximum and m i n i m u m v a l u e s  transformed,  individuals  o b s e r v e d , p o p u l a t i o n mean,  standard  F i g u r e 6.  An e x a m p l e o f d a t a t r a n s f o r m a t i o n p r o c e d u r e u s e d o n m e t r i c a l  characters  Days t o e m e r g e n c e  "0 raw  data  transformed  standard x  s. d  18.4  4.1  x  s ,d.  correction  x'  s.d!  X. x 0.7522 + 2.776  18.4  4.17  PCO  control  20.77  5,55  PCO  early  21.03  4.47  18.6  3.36  PCO  late  21.81  5.17  19.2  3.89  PCO  short  19.43  4.08  17.4  3.07  PCO  tall  21.22  5.53  18.7.  4.16  - 38 deviation,  c o e f f i c i e n t o f v a r i a t i o n , skewness, and k u r t o s i s .  In addition,  frequency h i s t o g r a m s o f a l l d i s t r i b u t i o n s - were generated to d e p i c t  them  graphically.  Comparisons between d i s t r i b u t i o n s  For  every m e t r i c a l  c h a r a c t e r the d i s t r i b u t i o n s o f the s e l e c t e d  p o p u l a t i o n s were compared t o those o f the c o n t r o l i n the same g e n e r a t i o n ( f o r example, PCO e a r l y G^vs.. PCO c o n t r o l G^) by means o f K r u s k a l l - W a l l i s tests also tests  (non-parametric a n a l y s i s  of v a r i a n c e ) .  compared between g e n e r a t i o n s w i t h i n ( f o r example, PCS s h o r t  The transformed d a t a were  l i n e s by means o f K r u s k a l l - W a l l i s  G ^ v s . PCS s h o r t  G,_) .  Correlations  Correlations  between a l l p a i r s o f m e t r i c a l  characters within  each  p o p u l a t i o n were c a l c u l a t e d by Spearman's rank c o r r e l a t i o n p r o c e d u r e .  Heritability  estimates  2 E s t i m a t e s o f narrow sense h e r i t a b i l i t y  (h , the p r o p o r t i o n  of the  t o t a l p h e n o t y p i c v a r i a n c e i n a p o p u l a t i o n which i s a t t r i b u t a b l e t o a d d i t i v e genetic  e f f e c t s ) were c a l c u l a t e d flowering  i n the e x p e r i m e n t a l p o p u l a t i o n s f o r the  selected  characters,  time and h e i g h t a t a n t h e s i s ,  Realized  h e r i t a b i l i t y was c a l c u l a t e d  by two methods.  a f t e r the method o f H i l l  e s t i m a t e i s based on the r a t i o s o f s e l e c t i o n d i f f e r e n t i a l p r e s s u r e ) to. response i n l i n e s under d i v e r g e n t s e l e c t i o n .  (1972 ) .  This  (selection Heritabilities  w e r e a l s o c a l c u l a t e d f o r a l l m e t r i c a l c h a r a c t e r s - b y t h e -method o f p a r e n t - o f f s p r i n g r e g r e s s i o n s - i n the' c o n t r o l l i n e s  Variance within  u n i v a r i a t e ANOVA f o r t h e m e t r i c a l c h a r a c t e r s . components between f a m i l i e s and w i t h i n  Other  I960),  populations  The c o m p o n e n t s o f v a r i a n c e w i t h i n p o p u l a t i o n s  into  (Falconer,  were analyzed  The v a r i a n c e was p a r t i t i o n e d  families.  characters  Frequencies of f r u i t wing phenotypes, pubescence p a t t e r n s , and  by  b o d y c o l o u r s , p r e s e n c e o f w i n g i n d e n t a t i o n , and a b e r r a n t  were t a b u l a t e d  f o r every  population.  fruit  wing  characters  Results  Breeding  s y s t e m s i n P l e c t r i t i s - c o n g e s t a • and  Outcrossing  The was  r a t e s i n the source p o p u l a t i o n s  o u t c r o s s i n g r a t e i n t h e P.  e s t i m a t e d by  61.6%. seed.  P__ B r a c h y s t e m o n  ( M i l l H i l l Pk.,  1977)  c o n g e s t a s o u r ce p o p u l a t i o n i n  1977  t h e p r o g e n y t e s t method (Ganders e t a l . , 1977a.) t o  T h i s i s b a s e d on a t o t a l s a m p l e o f 1175 This estimate  individuals  compares w e l l w i t h o t h e r e s t i m a t e s  grown f r o m  of o u t c r o s s i n g  r a t e s i n p o p u l a t i o n s o f t h e s p e c i e s , w h i c h h a v e a v e r a g e d a r o u n d 70% et  a l . , 1 9 7 7 a * , C a r e y and Since  all  the source  G a n d e r s , 1980;  Laytonj  be  (Ganders  1980).  p o p u l a t i o n o f P ^ b r a c h y s t e m o n was  monomorphic f o r  of the m o r p h o l o g i c a l markers w h i c h might have been used i n a progeny  t e s t , no e s t i m a t e i s no  reason  of the o u t c r o s s i n g r a t e i s yet a v a i l a b l e  to expect  t h i s population to d i f f e r  substantially  measured throughout  the range of the s p e c i e s i n B r i t i s h  et  Layton  a l . ( 1 9 7 7 b , ) and  allozyme  (1980), u s i n g the  polymorphisms r e s p e c t i v e l y , estimate  r a t e i n P^ b r a c h y s t e m o n i s 2%,  and no  effect  r o u g h l y , e s t i m a t e d i n P.  congesta by examining  follows.  g r o u p , PCS,  ( h o m o z y g o u s r e c e s s i v e s ) c a n be  Ganders  f r u i t wing polymorphism t h a t the  and  average o u t c r o s s i n g exceeding  s y s t e m as p r a c t i s e d c a n p a r t i c u l a r progenies  the progenies  scored  others  5%.  populations  of the e x p e r i m e n t a l b r e e d i n g  I n the s e l f e d  There  from  Columbia.  p o p u l a t i o n s were found  O u t c r o s s i n g r a t e s i n the e x p e r i m e n t a l  The  for i t .  of wingless  to o b t a i n the frequency  be  as  fruited  plants  of winged  - 41 f r u i t e d progeny, w h i c h are n e c e s s a r i l y the r e s u l t of o u t c r o s s i n g events. This  frequency w i l l underestimate  t h e a c t u a l r a t e o f o u t c r o s s i n g , as  ( s m a l l ) p r o p o r t i o n of the w i n g l e s s the r e s u l t of o u t c r o s s e s plants.  f r u i t e d progeny are l i k e l y  t o o t h e r homozygous r e c e s s i v e o r  I n t h e o u t c r o s s e d g r o u p , PCO,  progenies  a  a l s o to  be  heterozygous  of w i n g l e s s  fruited  plants  w h i c h have b e e n c r o s s e d t o homozygous dominant w i n g e d f r u i t e d p l a n t s be  scored  to o b t a i n the frequency, x,  of wingless  these were a l l the r e s u l t of a c c i d e n t a l s e l f i n g , Be.l  - :x.  the r e s u l t  be  large,  Cthe h i g h e r  of r e c o r d .  The  and m o s t l y d e p e n d s on the  frequency  of the  case  is  frequencies i n the the  likely,  t o some p l a n t  e r r o r i n these estimates  recessive allele,  e r r o r ) ; n e y e r t h e l e s s , the e s t i m a t e s  of the a c t u a l  f r u i t e d progeny are again  the a l l e l e  If  the o u t c r o s s i n g r a t e would  of a c c i d e n t a l o u t c r o s s e s , i n t h i s  than the p o l l e n parent to  offspring.  I n p r a c t i c e t h i s e s t i m a t e i s a g a i n an u n d e r e s t i m a t e  o u t c r o s s i n g r a t e , as some o f t h e w i n g l e s s to be  fruited  can  other  likely  populations  l a r g e r w i l l be  the  are of i n t e r e s t , , a n d are g i v e n i n  Table I I .  Characteristics  of the base p o p u l a t i o n s  Descriptive statistics  The  initial  of the m e t r i c a l ( q u a n t i t a t i v e ) c h a r a c t e r s  distributions  of the v a r i o u s measured c h a r a c t e r s i n the  b a s e p o p u l a t i o n s , G g , , o f t h e two the e x p e r i m e n t a l  species are given i n Table  c o n d i t i o n s i n t h e g r o w t h c h a m b e r , P.  III.  Under  b r a c h y s t e m o n emerges  later,  g r o w s t a l l e r , p r o d u c e s m o r e n o d e s and m o r e p r i m a r y b r a n c h e s ,  later,  and  p r o d u c e s more f r u i t  t h a n P.  congesta.  of v a r i a t i o n , which are s c a l e f r e e estimates  Examining the  of the phenotypic  flowers  coefficients variability,  - 42 Table I I .  Estimates  of o u t c r o s s i n g rates i n the - experimental  populations.  P. c o n g e s t a s e l f e d  Population PCS  control  PCS  Number o f p r o g e n i e s G  o  late  G  o  PCS  short  G  o  PCS  tall  G  o  PCS  control  G  l  PCS  early  G  l  PCS  late  G  l  PCS  short  G  l  PCS  tall  G  l  G  2  PCS  control  PCS  late  G  2  PCS  short  G  2  PCS  tall  PCS  control  PCS  G  2  G  3  late  G  3  PCS  short  G  3  PCS  tall  G  3  Estimated  3  0.25  3  0.19  5  0.35  3  0.08  4  0.18  1  0.00  6  0.10  5  0.12  4  0.04  4  0.05  6  0.22  6  0.06  6  0.04  4  0.28  7  0.22 0.15  17  0.14  8 mean  P.  0.15  congesta outcrossed  PCO e a r l y  G  o  PCO  G  o  PCO l a t e ' .  G  l  PCO e a r l y  G  2  PCO  late  G  2  PCO  short  G  2  PCO  late  G  3  PCO  tall  G  3  late  1  0.80  1  0.60  3  0.59  2  0.68  1  0.29  2  0.94  1  0.67  1  0.63 mean  0.65  outcrossing  rate  Table I I I .  Measured characters:, base N  "Mean  populations. Standard deviation  Coefficient of variation  P_. c o n g e s t a  Days t o emergence  9Q5  18.40  4.177  22.70  **  855  223,87  45.121  20.15  **  855  8.91  1.108  12.43  **  855  2.71  3.417  126.09  **  Chumber] Height a t anthesis (mm) Nodes a t a n t h e s i s (number) • Primary branches (number) Days t o a n t h e s i s (number) Fruit production (number)  855  95.02  7.379  7.76  861  25.10  18.820  74.99  a  *  P. b r a c h y s t e m o n  Days t o e m e r g e n c e (number) Height a t anthesis (mm) Nodes a t a n t h e s i s (number) Primary branches (number) Days t o a n t h e s i s (number) Fruit production  304  21.08  5.729  27.17  293  302.91  72.618  23.97  293  11.80  1.656  14.03  293  6.43  6.841  106.40  292  116.76  8.088  6.93  291  61.26  28.48  68.80  Asterisks indicate coefficients of v a r i a t i o n s i g n i f i c a n t l y d i f f e r e n t f r o m t h o s e i n P b r a c h y s t e m o n ; ** a t t h e 1% l e v e l , * a t t h e 5% l e v e l , a c c o r d i n g t o m o d i f i e d F - t e s t s (Lewontin; 1966).  it  a p p e a r s t h a t P.  b r a c h y s t e m o n i s more v a r i a b l e  d a y s t o e m e r g e n c e , h e i g h t , and  t h a n P.  number o f n o d e s a t a n t h e s i s , and  v a r i a b l e f o r number o f p r i m a r y b r a n c h e s a t a n t h e s i s and T h e r e was fruit  no  significant  congesta  d i f f e r e n c e i n the  coefficient  less  flowering  time.  of v a r i a t i o n  for  production.  Frequencies  of q u a l i t a t i v e  characters  P l e c t r i t i s brachystemon i s monomorphic f o r a l l the f r u i t scored;  the scores  f o r the base populations  p a t t e r n are presented The  for  i n Figures  phenotype frequencies  7 t o 10,  population  (12.5%  discussed  fruits  wingless,  f o r pubescence  Response to s e l e c t i o n of the s e l e c t e d  later.  p l a n t e d i n GQ w e r e  87.5%  winged);  o f t h e a d u l t p l a n t s i n GQ a r e p r e s e n t e d  phenotype frequencies  at  congesta  and w i l l be  o f w i n g e d and w i n g l e s s  t h e same as i n t h e s o u r c e  Height  o f P.  characters  the  i n Figure  11  characters  anthesis  Means '  The  mean h e i g h t s  anthesis departed in  significantly  most g e n e r a t i o n s ,  PCS" s h o r t G ^  PCS  t h e P. . c o n g e s t a the, c o u r s e  of p l a n t s i n the p o p u l a t i o n s from the  the e x c e p t i o n s  tall  G , 2  and  PBS  control  being short &  PCO 2  selected for height  (unselected)  s h o r t G ^ , PCO (Figure 12).  population  tall  G ^ and  I n the case  p o p u l a t i o n s , t h e means i n t h e s e l e c t e d l i n e s d i v e r g e d  of the experiment w i t h , i n most c a s e s ,  the  tall  at  lines  being  G^  of over  - 45 F i g u r e 7.  Frequency' o f v a r i o u s pubescence t y p e s ( s e e F i g u r e 4) I n the e x p e r i m e n t a l p o p u l a t i o n s ,  a. Pubescence type 0 i n PCO  populations  b. Pubescence t y p e l i n PCO  populations  c. Pubescence type 2 i n PCO  populations  Figure  7.  .06  .04  a.  PCO  type  /  /  0 .02  o e  /  /  A /  \  v\ \  v  .06 Control  0)  fi crcu M «w fi M  Height .04 Anthesis  0)  b.  PCO  type  1  4-> 4-1  cd  cu a) o fi a) o to a) •8  P4.  .02 \j_ate  \  \ '\tall  \ >4 late  c.  PCO  type  2 early short  Generations  of  selection  < Figure  8.  -47 F r e q u e n c y o f v a r i o u s pubes-cence t y p e s  Csee F i g u r e 4) i n  the e x p e r i m e n t a l populations-.  a. P u b e s c e n c e t y p e  3 i n PCO  populations  b. . P u b e s c e n c e t y p e  4 i n PCO  populations  c. P u b e s c e n c e t y p e 5 i n PCO  populations  Figure  8.  .6  a.  PCO  type  h ^  3  ,3  short early  r  short o  cu cr a) u b.  PCO  type  4  .2  r  early  <4-l  0  Control  cu  Height a) o C cu o  Anthesis  CD  •\ ^  co  tall late 4  early c.  PCO  type  5  tall  Generations  of  selection  - 49 F i g u r e 9.  F r e q u e n c y o f v a r i o u s ...pubescence t y p e s , ( s e e F i g u r e 4) i n the experimental  populations.  a. P u b e s c e n c e t y p e  0 i n PCS  populations  b. Pubescence type  1 i n PCS  populations  c. P u b e s c e n c e t y p e  2 i n PCS  populations  gure  .04  9.  PCS  type. 0  PCS  type  1  PCS  type  2  r  Generations of  selection  F i g u r e 10... F r e q u e n c y o f v a r i o u s p u b e s c e n c e . t y p e s £he. e x p e r i m e n t a l  ( s e e F i g u r e 4) i n  populations.  a. -Pubescence  t y p e 3 i n PCS  populations  b. P u b e s c e n c e  t y p e 4 i n PCS  populations  c. P u b e s c e n c e  t y p e 5 i n PCS  populations  51  Figure  10.  a.  type  PCS  - 52  3  short  0  1  2  G e n e r a t i o n s of  3  4  selection  F i g u r e U..,  Frequency,.of? w i n g l e s s ; f r u i t e d . p l a n t s i n t h e .  populations:  a. . PCO  populations  b.  populations  PCS  experimental  /  Control Height Anthesis  — — • —  - 55 F i g u r e 12.  Mean h e i g h t , . a t a n t h e s i , s i n , , . p o p u l a t j o n s s e l e c t e d f o r . w  > h e i g h t , . a t .anthesis.- 'Means: a r e - e x p r e s s e d a s a p e r c e n t a g e o f t h e ...means, i n t h e c o n t r o l l i n e s . . : . P o p u l a t i o n s - w h i c h . . i n t e r s e c t vertical ... -  l i n e s . d i d .not d i f f e r  population  significantly  i n . t h e . same g e n e r a t i o n  the ,  from the c o n t r o l  (the v e r t i c a l  lines  do n o t  represent standard d e v i a t i o n s ) .  The  following pairs of consecutive  did  not d i f f e r  significantly:  PCO s h o r t G Q a n d G ^ G ^ a n d G ^ PCO t a l l  GQ and G  1  PCS t a l l  G  3  and G  2  PCS s h o r t G . a n d G  4  PBS t a l l  G . and G  4  5  5 C  C  populations  within  lines  taller In  t h a n . t h e c o n t r o l , a n d the:,sh.ort-: l i n e s  s h o r t e r t h a t . the. c o n t r o l .  PCO t h e d i v e r g e n c e , h y , ' t h e . : : f i f t h i " c y c l e of. s e l e c t i o n " a m o u n t e d t o 6 6 % o f  the c o n t r o l h e i g h t divergence 175 mm  by.G  (+61 mm,  l i n e s departed  -114 mm)..  -56mm).  I n PCS, t h e  The means, i n . t h e .,P. . b r a c h y s t e m o n s e l e c t e d  significantly  i nG^,  the t a l l  (+92 mm,  a m o u n t e d .to .78% o f t h e c o n t r o l h e i g h t . ( + 2 7 % , . - 5 1 % ) o r  rather fluctuating control  ( + 4 1 % , - 2 5 % ) o r 1 4 8 mm  from  the control  e r r a t i c a l l y with both and G,., and t a l l e r  l i n e ;was s h o r t e r t h a n  lines, but d i d not diverge,  l i n e s being s h o r t e r than the  than  i nG^.  the control  the short l i n e  In addition,  i n G.. a n d G , . 1 4  The mean h e i g h t s i n t h e v a r i o u s s e l e c t e d l i n e s w e r e a l s o c o m p a r e d generation to generation.and cases, G„, 3  the following being  PCO t a l l  tall  proved  t o be s i g n i f i c a n t l y  the exceptions:  i n most  PCO s h o r t G ^ v s . G Q , G ^ V S .  G ~ v s . G , PCS s h o r t . G v s . G . , PCS t a l l I 0 5 4 N  different  C  G „ v s . G _ , a n d PBS 3 2  G vs. G . . 5 4 C  Estimates  of v a r i a b i l i t y  •Variances  The v a r i a n c e s f o r b o t h  t h e raw and t r a n s f o r m e d  c o m p a r e d among a l l p o p u l a t i o n s . although  The v a r i a n c e s i n t h i s  some.of t h e e n v i r o n m e n t a l  within generations  control.  case  are phenotypic,  component h a s h o p e f u l l y been e l i m i n a t e d  the selected population values  against.an  . .  S i n c e . t h e v a r i a n c e o f a c h a r a c t e r i s dependent on  t h e mean ( i n a p o p u l a t i o n , w i t h a l a r g e r mean, t h e v a r i a n c e w i l l . a l s o to  were  b y t h e u s e o f a common e n v i r o n m e n t , a n d b e t w e e n  generations by c o r r e c t i n g unselected  values of height  tend  b e l a r g e r ) , t h e ...selected l i n e s , w e r e compared, b y means o f t h e c o e f f i c i e n t s  of - v a r i a t i o n  ( t h a t is„..,the . s t a n d a r d w d e v i a t i o n .of.:;the, mean, .as . a ..percentage  o f t h e mean) i n a m o d i f i e d F - t e s t  (Lewontin;  1966) ( F i g u r e 1 3 ) .  The  v  - 58  F i g u r e 1 3 . G p e f fi.ci.ents,,.o.f .'-yari.a.t'ion.^0,): h e i g h t ,at anthesis;~ifi .populations . , .selected for,. height.-at.;anthesls.-.. Coefficients of, v a r i a t i o n a r e expressed as a percentage of :.the c o e f f i c i e n t s : . i n . the .lines.  control  P o p u l a t i o n s which i n t e r s e c t the v e r t i c a l l i n e s d i d not  . d i f f e r s i g n i f i c a n t l y from the ..control p o p u l a t i o n i n the same .. -generation  (the v e r t i c a l l i n e s do not r e p r e s e n t  deviations).  standard  c o e f f i c i e n t s o f . . v a r i a t i o n . ±n..tbe-. s e l e c t e d . . . p o p u l a t i o n s .-were d i f f e r e n t from t h e and  c o n t r o l i n 14  o u t : o f 30  significantly..  c a s e s , n a m e l y PCO  G. ,._PCO t a l l -G-. ,..G„ , G' , andr G ., PCS' s h o r t G " and ,G. , PCS 4 1 2 4 5 3 4 cy  s h o r t G^»  and.. PBS. t a l l . G^.,  G^,  an i n c r e a s e i n v a r i a t i o n  (PCS  in  PCS  variation  (PCO  lines,  s h o r t G^, tall  and .G^..... Of.. t h e s e , s i x p o p u l a t i o n s and  PBS  l i n e s ) and  e i g h t showed a  G^,  G-,., 1  PB&  ;  showed.  decrease  tall).  Heritabilities  The  narrow sense h e r i t a b i l i t y  f o r . h e i g h t at anthesis was.estimated  two  2 ways.  N a r r o w . s e n s e ~ h e r i t a b i l i t y . ( h ) i s the p o r t i o n of the  phenotypic  variability  i n a p o p u l a t i o n w h i c h c a n be  total  attributed to.additive  g e n e t i c e f f e c t s , ( t h a t i s , g e n e t i c . e f f e c t s e x c l u d i n g dominance, e p i s t a s i s , and o t h e r i n t e r a c t i v e e f f e c t s ) . . - R e a l i s e d h e r i t a b i l i t i e s were c a l c u l a t e d . . after  t h e m e t h o d .of. H i l l  heritability 2  PCS  (b  has  e s s e n t i a l l y no  c  or h  of h e i g h t  experiment.  = 0.58)  The  i s significant and  the d i r e c t i o n  here  PCO  (b .= c  heritability  estimates  m e t h o d i s n o t meant t o be in  (1972) ( T a b l e IV) .  The  0.53).lines.  i n Table  equal between  this  IV are b r a c k e t e d because  o p p o s i t e t o t h e d i r e c t i o n o f s e l e c t i o n , as i s t h e G^) . . The  e s t i m a t e s .are q u i t e  estimated  the diverge  case  standard  large.  estimated, .heritabilities,:from...parent-off s p r i n g - r e g r e s s i o n s .(Table .  a r e i n reasonable,,agreement w i t h t h e - r e a l i s e d h e r i t a b i l i t y P.  the  P l e c t r i t i s brachystemon *  a p p l i e d . i n cases where the s e l e c t e d l i n e s  ( s e e F i g u r e . 12., PBS - l i n e s . . ih.G^.. and  The  approximately  f o r h e i g h t .under t h e c o n d i t i o n s o f  f o r PBS  d e v i a t i o n s f o r the h e r i t a b i l i t y  V)  and  I n t h e P. ..congesta : l i n e s . t h e  congesta .lines, have a f a i r l y 2 b e t w e e n t h e PCS ( h = 0.44) and PCO  estimates.  2 large h and t h e r e i s l i t t l e d i f f e r e n c e 2' ( h = 0.45) l i n e s . Plectritis  Table IV.  Realised h e r i t a b i l i t y ,  c a l c u l a t e d u s i n g the method of H i l l  P. congesta  Selection for early or l a t e a n t h e s i s  b  c  sd  u  b  S e l e c t i o n f o r short or t a l l h e i g h t  b  P. brachystemon  PCO  PCS  PBS  0.77  0.75  0.49  0.12  0.14  0.22  0.53  0.58  (0.06)  0.64  (0.34)  c  c  0.61  sd.  D  (1972).  C  Table V.  H e r i t a b i l i t y , from p a r e n t - o f f s p r i n g r e g r e s s i o n s * P.  congesta  PCO  PCS  PBS  0.60  0.72  0.42  0.53  0.55  0.48  0.45  0.44  -0.06  0.36  0.30  0.23  2  Days t o a n t h e s i s  h r  2  2 Height  at a n t h e s i s  h r  2  * Means of f o u r g e n e r a t i o n s  of c o n t r o l p o p u l a t i o n s .  i ON  b r achystemon .agaitu.has character.  63  e s s e n t i a l l y a h e r i t a b i l i t y of zero f o r t h i s  2 The r . . v a l u e s a l j s t e c h e s t i m a t e .the. p r o p o r t i o n , of,.the..total  v a r i a n c e e x p l a i n e d .by the r e g r e s s i o n , ori.in o t h e r words the goodness of  2 fit  of the • r e g r e s s i o n l i n e to t h e p a r e n t s - o f f s p r i n g p o i n t s .  f o r h e i g h t a r e f a i r l y low,  The  r  values  and q u i t e a b i t lower than those f o r f l o w e r i n g  time.  •Components of v a r i a n c e  An and  a n a l y s i s of variance-was performed f o r a l l p o p u l a t i o n s between  Gj., . p a r t i t i o n i n g the observed  (phenotypic). v a r i a n c e i n t o  w i t h i n and between f a m i l i e s i n e a c h . p o p u l a t i o n . c a s e s , such as i n p r o g e n i e s between pure b r e e d i n g  i n pure b r e e d i n g  I t i s only i n p a r t i c u l a r  l i n e s or i n the F^ of a c r o s s  lines,.. t h a t the v a r i a n c e s , so p a r t i t i o n e d can  c o n s i d e r e d p r e c i s e .estimates of. environmental  -line i s a - p r e c i s e e s t i m a t e of the environmental  The  be  or a d d i t i v e g e n e t i c  components. (Falconer., I960).. . The w i t h i n .family v a r i a n c e -in  genetic variance  components  a-.pure-breeding':  v a r i a n c e , as t h e r e i s no  present.  p o p u l a t i o n s i n t h i s experiment do not r e p r e s e n t pure b r e e d i n g  l i n e s , although  P. brachystemon i s c e r t a i n to be h i g h l y i n b r e d .  The  i n f o r m a t i o n t h a t can be obtained.from.an ANOVA.comes, t h e r e f o r e more from any  changes which might be observed.over the course  p a r t i t i o n i n g of the phenotypic theory  of the experiment i n the  v a r i a n c e between and w i t h i n f a m i l i e s .  In  ..inbreeding...will tend, .to .reduce, t h e . g e n e t i c .component of the w i t h i n ,  f a m i l y v a r i a n c e .and.-increase.-the variance.  .genetic .component of the. between .family  S e l e c t i o n , and r a n d o m - d r i f t . . w i l l , tend to decrease . the g e n e t i c  components i n b o t h w i t h i n and.between f a m i l y e s t i m a t e s .  In the  present  - 64 s i t u a t i o n y;, .where... the., genet i c , s t r u c f c u r e „of ..thei,populations.,, of,.;the two..: M  . .  s p e c i e s - i s unknown:,,:..,there, i s .^,no';':S'$mple-^•p^.e4i:e.ti.on'..of.^ t h e ..results- of ..the ,  ANOVA;  in..fact.,  the.. r e s u l t s showed v e r y . . l i t t l e . ..For. h e i g h t : a t a n t h e s i s a l l -  t h r e e s p e c i e s groups had a s i g n i f i c a n t between f a m i l y component o f v a r i a n c e i n most p o p u l a t i o n s  (Appendix 1 ) .  There were, no o b v i o u s  t r e n d s w h i c h might  have been e x p e c t e d , . . . p a r t i c u l a r l y t h e decrease..in between f a m i l y v a r i a n c e w h i c h m i g h t have b e e n expected  i n response t o s e l e c t i o n .  Other changes i n d i s t r i b u t i o n  There was no e v i d e n c e  from t h e f r e q u e n c y  histograms  of height at  a n t h e s i s i n t h e . v a r i o u s . p o p u l a t i o n s t o suggest t h a t t h e r e had B e e n c h a n g e s i n t h e d i s t r i b u t i o n .other :than ..the .changes i n .mean and v a r i a n c e . t h e r e was no e v i d e n c e  o f changes i n skewness -or k u r t o s i s ,  That i s ,  o r development  of b i m o d a l i t y i n the d i s t r i b u t i o n s .  Days t o a n t h e s i s ( f l o w e r i n g time)  Means  A s - w i t h h e i g h t . a t a n t h e s i s , the.mean f l o w e r i n g times f o r t h e s e l e c t e d populations differed  s i g n i f i c a n t l y from.the.controls  exception i n t h i s case.being  I n most c a s e s ,  PCS e a r l y G^ ( F i g u r e 14').  H i g h and.low  the s o l e selection  l i n e s i n a l l t h r e e , species..groups- diverged,.,with-.:the^early. l i n e s f l o w e r i n g s  e a r l i e r , than t h e c o n t r o l s , and t h e l a t e l i n e s f l o w e r i n g l a t e r .  The  divergence  by t h e . f i f t h , c y c l e ..of ^selection.was,,, .in -the ...case .of .PCO.,.. 33.5%. o f . t h e murnber . . of days -to. .anthesis,;.in.„the,..control.\.(«fc20%,,^13.. 5%.)... o r .31..8 ... days (+19..days, -12.8  d a y s ) . . I n PCS the .divergence was 28.7% o f t h e c o n t r o l (+16.3%, -12.4)  - 65 Figure  14  Mean .number o f . d a y s t o anthesis... ( f l o w e r i n g populations-selected as  .for f l o w e r i n g  time) i n  t i m e . . Cleans a r e e x p r e s s e d  a p e r c e n t a g e o f t h e means i n t h e c o n t r o l l i n e s . .  which .intersect the v e r t i c a l lines from t h e c o n t r o l .population vertical  lines  d i d not d i f f e r  Populations significantly  i n t h e same g e n e r a t i o n ( t h e  do n o t r e p r e s e n t s t a n d a r d  deviations).  The  following pairs of consecutive populations within  did  not d i f f e r  significantly:  PCO e a r l y • G  and  3  PCO l a t e G., a n d G „ ; G. a n d G.  1  2  3  4  PCS e a r l y G , a n d G^ Q  PCS l a t e  G  1  a n d G ; .G  and G  PBS l a t e  G  1  and G ; G  and G ;  2  2  2  2  3  3  G^ a n d  lines  Figure  14.  PBS  - 67 or 27.3 days (+15.5 .days, -11"•.8.. days J . 18.5%  of the control The  I n PBS t h e d i v e r g e n c e was  (+12.2%, -6.3%) o r 21.5 days.(+14.2 days, -7.3 d a y s ) .  mean.flowering.times'were a l s o  compared g e n e r a t i o n t o g e n e r a t i o n  w i t h i n the..selected, l i n e s , , w i t h t h e f o l l o w i n g p o p u l a t i o n s p r o v i n g nofr'to be significantly different: PCO l a t e G  2  G ^ vs.  PCS e a r l y  v s . G , and PBS l a t e G 1  2  G Q , PCS l a t e G ^ v s . G ^ , G ^ v s . G ^ ,  vs. G ^ G  3  vs. G  2  .  E s t i m a t e s of v a r i a b i l i t y Variances  The variation  v a r i a n c e s i n the p o p u l a t i o n s were c o n v e r t e d t o c o e f f i c i e n t s o f t o remove s c a l e  presented g r a p h i c a l l y  effects.  i n F i g u r e 15.  The c o e f f i c i e n t s The s e l e c t e d  c o n t r o l s by means o f the m o d i f i e d F - t e s t . f o r and  were found t o be s i g n i f i c a n t l y d i f f e r e n t G  namely PCO e a r l y G , 5  PCS l a t e G  2  2  5  >  PBS e a r l y  i n a l l cases except PCS l a t e G the  selected  selected  2  G  3  l i n e s were compared t o the  coefficients  of v a r i a t i o n , .  i n 16 of the 30 p o p u l a t i o n s ,  through G^, PCO l a t e G ^ and G  , G ^ , and G  of v a r i a t i o n are  5  >  PCS e a r l y  2  and G ^ , and PBS l a t e G  and PBS l a t e G , . the v a r i a t i o n  l i n e s than i n t h e c o n t r o l s .  G  through 5  >  Of these,  was l e s s i n  The g e n e r a l t r e n d i n a l l s i x  l i n e s was towards a decrease i n the c o e f f i c i e n t o f v a r i a t i o n .  Heritabilities  The  r e a l i s e d h e r i t a b i l i t i e s . ( T a b l e IV) a g a i n r e v e a l the b a s i c agreement  ? between the.PCO. (b .or h c brachystemon a l s o (b  = 0.49).  = 0 . 7 7 ) and PCS (b = 0 . 7 5 ) l i n e s . c  Plectritis  has a r e a s o n a b l y l a r g e h e r i t a b i l i t y . f o r f l o w e r i n g time  I n a l l .cases t h e s t a n d a r d d e v i a t i o n f o r t h e e s t i m a t e s i s  - 68 Figure 15.  . . C o e f f i c i e n t s , o f - v a r i a t i o n - f o r . :days t o a n t h e s i s ; i n , p o p u l a t i o n s selected  f o r f l o w e r i n g ..time. . . C o e f f i c i e n t s o f . / v a r i a t i o n  e x p r e s s e d as a p e r c e n t a g e o f t h e c o e f f i c i e n t s i n t h e lines. . differ  .Populations which i n t e r s e c t  control  the v e r t i c a l l i n e s d i d  s i g n i f i c a n t l y from the c o n t r o l p o p u l a t i o n i n the  g e n e r a t i o n , ( t h e v e r t i c a l l i n e s do n o t deviations).  are  represent  standard  not  same  PBS  —  c o n s i d e r a b l y •; s m a l l e r t h a n i n t h e h e r i t a b i l i t y . e s t i m a t e s  for height  70  at  anthesis. The  estimated, h e r i t a b i l i t i e s from p a r e n t - o f f s p r i n g r e g r e s s i o n s  flowering time  (Table y). are.comparable to the r e a l i s e d  e s t i m a t e s , w i t h t h e two 2  PCS  h  but  still  by  the  = 0.72)  and  P.  t h e P.  appreciable.  congesta c o n t r o l l i n e s  heritability  similar  brachystemon l i n e s l i g h t l y l e s s  Again,  goodness of f i t of the  the r e l i a b i l i t y  (PCO (h  h  2  =  of the estimates  regression lines  for  to the data  2  =  0.60,  0.42), i s indicated  2 (r ), which  2 in  t h i s c a s e shows a more r e l i a b l e e s t i m a t e  for height  at  of h  variance  As w i t h h e i g h t  at anthesis i n l i n e s  s e l e c t e d f o r h e i g h t , a l l the  selected  f o r f l o w e r i n g t i m e showed a s i g n i f i c a n t  variance  f o r f l o w e r i n g t i m e i n most p o p u l a t i o n s .  (Appendix  trend i n these  lines  b e t w e e n f a m i l y component Once a g a i n ,  parameters over the course  of the  t h e r e was  no  experiment  1).  Other changes i n  T h e r e was in  regression  anthesis.  Components o f  significant  than d i d the  no  the populations  distribution  evidence from.the frequency  s e l e c t e d f o r f l o w e r i n g time to suggest that there  been changes i n t h e d i s t r i b u t i o n .other T h a t i s , t h e r e was  h i s t o g r a m s of f l o w e r i n g  no  t h a n c h a n g e s i n mean and  distributions.  had  variance.  e v i d e n c e of changes i n skewness or k u r t o s i s ,  development of b i m o d a l i t y i n the  time  or  of  Changes i n the u n s e l e c t e d  The  71  c h a r a c t e r s -during the experiment  c h a r a c t e r s not under s e l e c t i o n - days to emergence, h e i g h t  at  a n t h e s i s i n . t h e l i n e s s e l e c t e d f o r f l o w e r i n g time, number of nodes at a n t h e s i s , number o f - p r i m a r y selected for height in  branches at a n t h e s i s , f l o w e r i n g time i n l i n e s  at a n t h e s i s , and  the same manner as the s e l e c t e d  f r u i t production  - were  analysed  characters.  Means  Days to emergence  A number of p o p u l a t i o n s  departed s i g n i f i c a n t l y from the c o n t r o l s i n  terms of the me.an- number of days to emergence: PCS  early  s h o r t G^  G  2>  G  3 >  PCS  ( F i g u r e 16).  l a t e G.^,  G^  PBS  PCO  early G^  early PBS  , PCO  t a l l G^  tall and  In a l l groups s e l e c t e d f o r e i t h e r h e i g h t . o r  G^,  PBS  flowering  time, the G,. means f o r days to emergence i n the p l u s s e l e c t e d l i n e s were g r e a t e r than the means i n the minus s e l e c t e d l i n e s , w i t h PCS  s e l e c t e d f o r f l o w e r i n g time.  the e x c e p t i o n  However, a number of l i n e s  of  experienced  r e v e r s a l s , w i t h the p l u s s e l e c t e d l i n e f a l l i n g , below, the minus ..selected line: G^.  PCS  anthesis  and  There appears to be no  H e i g h t at a n t h e s i s  PCO  height  G^.PCS h e i g h t  G^,  and  PBS  r e g u l a r t r e n d i n the changes i n emergence  (in l i n e s selected for flowering  e a r l y G_,  G , PCO  date.  time)  In the l i n e s s e l e c t e d f o r .flowering time, the .mean h e i g h t s s i g n i f i c a n t l y from the c o n t r o l s i n PCO  height  differed  l a t e -G. , G,,  PCS  -72 F i g u r e 16.  Mean .number ...of. d a y a ^ t o e m e r g e n c e . i n v a r i o u s . . p o p u l a t i o n s . M e a n s a r e . expressed-..as a . p e r e e n t a g e c o f - t h e / m e a n s lines.  i n the control  P o p u l a t i o n s w h i c h , i n t e r s e c t .the v e r t i c a l , l i n e s d i d .  not d i f f e r  significantly  from t h e c o n t r o l p o p u l a t i o n i n t h e  same g e n e r a t i o n , (.the v e r t i c a l  lines  do h o t r e p r e s e n t  standard  deviations).  a.  Mean number o f d a y s t o ..emergence i n p o p u l a t i o n s flowering  b.  time.  Mean number o f d a y s t o e m e r g e n c e i n p o p u l a t i o n s height  selected f o r  at anthesis.  selected f o r  PBS  - 74 e a r l y -G^. .PCS  late. G^, •,PBS,.early  »  G 3  »  a n  d  PBS  late G  (Figure 17).  3  The p l u s s e l e c t e d l i n e s ^ v e r e . . a l l v t a l l e . r ,,than.;.the:minus s e l e c t e d l i n e s  by  G,., b u t . a l l  PBS  late.  l i n e s were s h o r t e r . t h a n the c o n t r o l w i t h the e x c e p t i o n , o f  B o t h P.  congesta, l i n e s ..experienced,^reversals i n G^. . A g a i n ,  there  appear to be no long, term t r e n d s . i n changes i n h e i g h t at a n t h e s i s i n the lines selected for flowering  time.  Nodes at a n t h e s i s  The mean number of nodes at a n t h e s i s departed c o n t r o l s i n a l l p o p u l a t i o n s except •G^, PCS  s h o r t G^,  PCS  t a l l G^,  s t r o n g t r e n d toward d i v e r g e n c e  PCO  l a t e G^,  and.PBS t a l l G^  PCO  toward d i v e r g e n c e  except  PBS  Primary  i n p a r t to the same f a c t o r s which l e a d flowering  i s more marked i n l i n e s  branches at a n t h e s i s i n the s e l e c t e d l i n e s  somewhat e r r a t i c d e p a r t u r e s  short G ,  s h o r t G , PCS  strong trend  time.  being s i g n i f i c a n t l y . d i f f e r e n t PCO  The  above the c o n t r o l  branches at a n t h e s i s  showed l a r g e and  3  t a l l G^  a  and  between the number of nodes at a n t h e s i s and  The number of primary  G,  PBS  s h o r t G^ below i t .  time (see C o r r e l a t i o n s below) as the d i v e r g e n c e selected for flowering  There was  i n l i n e s s e l e c t e d f o r both height  i s undoubtedly due  to a s t r o n g c o r r e l a t i o n  short G ^ j G ^ , PCO-tall.  ( F i g u r e 18).  f l o w e r i n g time, w i t h a l l p l u s p o p u l a t i o n s except and a l l minus p o p u l a t i o n s  s i g n i f i c a n t l y f.rom the  2  tall  PCO  t a l l . G^.,  G , PBS  i n a l l cases G^,  PCS  from the c o n t r o l s , the means  except  early G „  e a r l y G , PBS  2  l a t e G,,  PCO PCS PBS  e a r l y G^>  PCO  l a t e G^,, G , 2  late  G ,. 3  s h o r t G , .and PBS  G^,  PCS tall  - 75 F i g u r e 17.  a.  Mean h e i g h t a t a n t h e s i s i n p o p u l a t i o n s s e l e c t e d f o r  f l o w e r i n g time.  Means a r e expressed  means i n the c o n t r o l l i n e s .  as a percentage o f the  P o p u l a t i o n s which i n t e r s e c t the  v e r t i c a l l i n e s d i d not d i f f e r s i g n i f i c a n t l y p o p u l a t i o n i n the same g e n e r a t i o n  from the c o n t r o l  ( the v e r t i c a l l i n e s  do n o t  r e p r e s e n t standard d e v i a t i o n s ) .  b.  Mean number of days to a n t h e s i s i n p o p u l a t i o n s s e l e c t e d f o r  height at anthesis.  Means a r e expressed  means i n the c o n t r o l l i n e s . vertical lines  as a percentage o f the  P o p u l a t i o n s which i n t e r s e c t the  d i d not d i f f e r s i g n i f i c a n t l y  p o p u l a t i o n i n the same g e n e r a t i o n represent standard d e v i a t i o n s ) .  from the c o n t r o l  (the v e r t i c a l  lines  do n o t  - .76 Figure  17.  140 o  u  CO 4-1 •H G CO o cu a 4J CH  C  O  100  4-1 60  rt rt  4-1 4-1 C  cu 60 o H cu a) ^! ft C cn rt rt a) v—' •H  60  r  20. r  CO  •1-1 CO a) 4-1  b.  110  h  .—* O  rt 4MJ O c 4-1 o u  CO >•> C H  Trt 3  tall short short  100  o  cu  4-1 60 O rt 4J H a) CU  «  ,g o u cu ci ft C CO  short 90  rt rt cu s  Generations of  PCO PCS PBS  selection  - 77 F i g u r e 18.  Mean number of nodes a t a n t h e s i s i n v a r i o u s p o p u l a t i o n s . Means a r e e x p r e s s e d as a percentage o f the means i n the c o n t r o l lines.  P o p u l a t i o n s which i n t e r s e c t the v e r t i c a l  not d i f f e r s i g n i f i c a n t l y generation  (the v e r t i c a l  lines did  from the c o n t r o l p o p u l a t i o n i n the same lines  do n o t r e p r e s e n t  standard  deviations).  a.  Mean number o f nodes a t a n t h e s i s i n p o p u l a t i o n s for  b.  selected  f l o w e r i n g time.  Mean number o f nodes a t a n t h e s i s i n p o p u l a t i o n s for height a t anthesis.  selected  PBS  —  G^  ( F i g u r e 19).  In most cases  t h e r e was  d i v e r g e n c e , w i t h the p l u s  s e l e c t e d l i n e s having more p r i m a r y branches than the minus l i n e s . of r e v e r s a l s were observed G^ and G^,  PCO  G^)  A number  i n the l i n e s s e l e c t e d f o r h e i g h t a t a n t h e s i s  (PBS  and most l i n e s f l u c t u a t e d e r r a t i c a l l y , o f t e n above and  below the c o n t r o l s i n d i f f e r e n t  generations.  There may  have been some e f f e c t  of s e l e c t i o n i n the l i n e s s e l e c t e d f o r f l o w e r i n g time, but otherwise were no  79  t r e n d s i n the changes of the means.  The  fact  there  t h a t the s e l e c t e d l i n e s  seem to c y c l e up and down r e l a t i v e to the c o n t r o l s from g e n e r a t i o n  to  g e n e r a t i o n r e f l e c t s changes i n the c o n t r o l s r a t h e r than i n the s e l e c t e d l i n e s , and  i n d i c a t e s the s e n s i t i v i t y of t h i s c h a r a c t e r to changes i n the  environment from g e n e r a t i o n  Flowering  to  generation.  time ( i n l i n e s s e l e c t e d f o r h e i g h t a t a n t h e s i s )  S e l e c t i o n f o r h e i g h t at a n t h e s i s appears to have had on f l o w e r i n g time. being PCO  A l l the s e l e c t e d l i n e s have d i v e r g e d somewhat, w i t h a l l  significantly different  tall G  l 9  PCS  short G^  strong c o r r e l a t i o n  some e f f e c t  PBS  from the c o n t r o l s except PCO short G  2>  and PBS  tall G  l  s h o r t G^,  G^,  ( F i g u r e 17).  between f l o w e r i n g time and number of nodes a t a n t h e s i s  can be seen i n the s i m i l a r i t y between the changes i n the means f o r the in  The  l i n e s s e l e c t e d f o r h e i g h t a t a n t h e s i s (compare F i g u r e 17 b w i t h  two  Figure  18 b ) .  Fruit  production  F r u i t p r o d u c t i o n was g r e a t d e a l of e r r o r . l i n e s departed  a c h a r a c t e r whose measurement was  As can be seen i n F i g u r e 20,  s u b j e c t to a  the means i n the s e l e c t e d  s i g n i f i c a n t l y from the c o n t r o l s i n many c a s e s , the  exceptions  - 80 F i g u r e 19.  Mean number o f primary populations.  branches a t a n t h e s i s i n v a r i o u s  Means a r e expressed  i n the c o n t r o l l i n e s .  P o p u l a t i o n s which i n t e r s e c t  l i n e s d i d not d i f f e r s i g n i f i c a n t l y i n the same g e n e r a t i o n standard  a.  the v e r t i c a l  from the c o n t r o l p o p u l a t i o n  (the v e r t i c a l l i n e s do n o t r e p r e s e n t  deviations).  Mean number of primary branches a t a n t h e s i s i n p o p u l a t i o n s selected f o r flowering  b.  as a percentage of the means  Mean number o f primary  time.  branches a t a n t h e s i s i n p o p u l a t i o n s  selected f o r height a t anthesis.  - 82 F i g u r e 20.. Mean f r u i t p r o d u c t i o n i n v a r i o u s p o p u l a t i o n s .  Means a r e  e x p r e s s e d as a percentage of the means i n the c o n t r o l  lines.  a. Mean f r u i t p r o d u c t i o n i n p o p u l a t i o n s s e l e c t e d f o r f l o w e r i n g time.  The f o l l o w i n g p o p u l a t i o n s d i d n o t d i f f e r from the  c o n t r o l i n the same g e n e r a t i o n : PCS e a r l y G  2 >  PBS l a t e G ^  G  3 >  Gy  PCO e a r l y G^, PCO l a t e G^,  G^, PCS l a t e G ^  G  3 >  PBS e a r l y G^, G  3 >  and  G^.  b. Mean f r u i t p r o d u c t i o n i n p o p u l a t i o n s s e l e c t e d f o r h e i g h t a t anthesis.  The f o l l o w i n g p o p u l a t i o n s d i d ' n o t d i f f e r from the  c o n t r o l i n the same g e n e r a t i o n : PCS s h o r t G^, G  3 >  PBS t a l l G,, G..  1  4  PCS t a l l G ^  PCO s h o r t G^, PCO t a l l G^, G G  2 >  G  3 >  G^, PBS s h o r t G , and  PBS  b e i n g PCO e a r l y G^, PCO s h o r t  G^, PCO  t a l l G^, PCS e a r l y G , 2  G , 3  PCS  late.Gj^,. G , PCS s h o r t G ^  G^, PCS t a l l G^, G^, G  3 >  PBS e a r l y  G^  PBS l a t e G^, G , PBS s h o r t  G^, and PBS t a l l G^.  I t can a l s o be seen  p a i r s of l i n e s , p l u s and minus, wander e r r a t i c a l l y b u t t o g e t h e r , t h a t most of the movement i s due to chance or e r r o r , and by the f r u i t p r o d u c t i o n i n the c o n t r o l  that  suggesting  strongly,influenced  lines.  E s t i m a t e s of v a r i a b i l i t y  Variances  The v a r i a n c e s i n the u n s e l e c t e d c h a r a c t e r s ,  expressed as c o e f f i c i e n t s  of v a r i a t i o n , a r e p r e s e n t e d i n Appendix 2, and g r a p h i c a l l y f o r days to emergence and number , of nodes a t a n t h e s i s  i n Figures  i n days to emergence shows a g e n e r a l i n c r e a s e ,  21 and 22.  w i t h wide f l u c t u a t i o n s , as  does v a r i a t i o n i n the number of p r i m a r y branches a t a n t h e s i s . anthesis  i n l i n e s selected f o r flowering  Variation  Height at  time i s l e s s v a r i a b l e i n PCO and  PCS e a r l y by G^_, and s l i g h t l y more v a r i a b l e i n PCS l a t e and PBS. i n the number of nodes a t a n t h e s i s  tended to decrease, p a r t i c u l a r l y i n  those l i n e s s e l e c t e d f o r flowering; time. l i n e s selected f o r height at anthesis but  Variation  Variation i n flowering  time i n  decreased i n the P^ congesta  lines,  f l u c t u a t e d above and below the c o n t r o l i n the P. brachystemon l i n e s .  V a r i a t i o n i n f r u i t p r o d u c t i o n a l s o changed v e r y e r r a t i c a l l y , r e f l e c t i n g the error inherent  i n the measurements.  Heritabilities  - 85 F i g u r e 21'.  Coefficients  of v a r i a t i o n  i n the experimental are expressed in  a.  b.  Coefficients  c.  of v a r i a t i o n of v a r i a t i o n  lines.  of variation  f o r number o f d a y s t o  emergence  of v a r i a t i o n  f o r number o f d a y s t o  emergence  f o r number o f d a y s t o  emergence  populations.  Coefficients i n PBS  Coefficients  emergence  populations.  Coefficients i n PCS  populations.  as a p e r c e n t a g e o f t h e c o e f f i c i e n t s  the control  i n PCO  f o r number o f d a y s t o  of v a r i a t i o n  populations.  - 87 Figure  22.. C o e f f i c i e n t s in  of v a r i a t i o n  the experimental  f o r number o f n o d e s a t a n t h e s i s  populations.  Coefficients  of v a r i a t i o n  a r e e x p r e s s e d as a p e r c e n t a g e o f t h e c o e f f i c i e n t s in  a.  the control  Coefficients i n PCO  b.  c.  of v a r i a t i o n  f o r number o f n o d e s a t a n t h e s i s  of variation  f o r number o f n o d e s a t a n t h e s i s  populations.  Coefficients i n PBS  lines.  populations.  Coefficients i n PCS  of v a r i a t i o n  of v a r i a t i o n  populations.  f o r number o f n o d e s a t a n t h e s i s  There was  o n l y one  e s t i m a t e of h e r i t a b i l i t y f o r the  89  unselected  c h a r a c t e r s from the experiment, as the r e a l i s e d h e r i t a b i l i t y procedure i s not a p p l i c a b l e .  The h e r i t a b i l i t y e s t i m a t e s  from p a r e n t - o f f s p r i n g r e g r e s s i o n s  i n the c o n t r o l l i n e s f o r these c h a r a c t e r s a r e p r e s e n t e d As i n d i c a t e d by  the c o e f f i c i e n t s of d e t e r m i n a t i o n ,  r e g r e s s i o n l i n e i s q u i t e poor i n most c a s e s . g r e a t e r than 0.2  are c o n s i d e r e d a l o n e ,  i n Table  VI.  2 r , the f i t of  the  I f the cases where r  2  is  the f o l l o w i n g h e r i t a b i l i t i e s may  be  2 estimated.  For days to emergence, h  = 0 . 4 9 i n PCO.  For nodes a t a n t h e s i s ,  2 h and  = 0.55  i n PCO,  0.57  i n PCS,  somewhat i n t e r m e d i a t e  characters.  Only PBS has 2 .  primary b r a n c h e s , h  and  0.28  i n PBS.;  these v a l u e s a r e  comparable  to the e s t i m a t e d h e r i t a b i l i t i e s f o r the s e l e c t e d reasonably  p r e c i s e estimates  f o r the number of  = 0 . 2 9 , and none of the l i n e s p r o v i d e d a r e l i a b l e  e s t i m a t e f o r the h e r i t a b i l i t y of f r u i t Components of v a r i a n c e  production.  There were s i g n i f i c a n t between f a m i l y components of v a r i a n c e i n a l l the u n s e l e c t e d c h a r a c t e r s i n a l l t h r e e s p e c i e s groups and most p o p u l a t i o n s (Appendix 1). trends over due  As w i t h the s e l e c t e d c h a r a c t e r s , t h e r e were no c o n s i s t e n t  the course of the experiment, and n o t h i n g  to suggest  changes  to s e l e c t i o n i n the p a r t i t i o n i n g of the t o t a l v a r i a n c e between  within  and  families.  Other changes i n d i s t r i b u t i o n  As w i t h the s e l e c t e d c h a r a c t e r s , t h e r e was frequency  no evidence  h i s t o g r a m s of the u n s e l e c t e d c h a r a c t e r s to suggest  i n d i s t r i b u t i o n s o t h e r than the changes i n mean and  from any  variance/  the changes  Table V I .  Heritabilities unselected  PCO  from p a r e n t - o f f s p r i n g  regressions,  characters.  control  PCS  control  PBS  control  Days t o emergence  .68  .65  .43  .14  .16  .026  .09  .0058  ,18  .03  ,21  .056  .31  .20  ,12  .018  ,32  .14  .0007-  .0000.  ,28  .082  ,14  .10  .71  .48  .43  .20  .066  .0084  .48  .48  .73  .53  .13  .052  .46  .39  .49  .46  .28  .25  .17  .059  .65  .80  .13  .087  .49  Nodes a t  x  anthesis  .55  Primary branches  .57  at  .'28  anthesis  .05  .0043  .081  .02  .22  .069  .27  .092  .34  .22  .29  .14  .076  .02  .24  .22  ,20  .18  .12  .035-  .38  .18  .13  .053  .29  Table VI, continued.  PCO c o n t r o l 2  .,2 h  .0052  -.015  .055  .11  .15  .099  .11  .079 ,  .02  -.11.  h u  Fruit  G G  2  r  G.  r  PBS 2  '  control  ,2 ' h  r  2  production  .05 3  PCS c o n t r o l  -.10  '  .0009 . .07  .15  .14  -.034  .0045  .023  -.083  .011  .055  -.033  .0059  4 G  5  The  92  e f f e c t s of s e l e c t i o n on c o r r e l a t i o n s among the measured c h a r a c t e r s  The  c o r r e l a t i o n between h e i g h t a t a n t h e s i s and  f l o w e r i n g time,  the  c h a r a c t e r s under s e l e c t i o n .  The  correlation.between  f l o w e r i n g time, was  characters, height at ,anthesis  I t decreased  more or l e s s s t e a d i l y towards no  the PBS  l i n e s , even becoming s i g n i f i c a n t l y n e g a t i v e  and PBS  s h o r t G^).  There was  some decrease  l i n e s , p a r t i c u l a r l y i n the t h i r d c y c l e , G^, showed a s i g n i f i c a n t n e g a t i v e mostly first  p o s i t i v e a g a i n , and f i v e generations  Other  The  and  1  i n i t i a l l y s i g n i f i c a n t and p o s i t i v e i n a l l t h r e e s p e c i e s  groups ( F i g u r e 23). in  the s e l e c t e d  cases  e v i d e n t i n the P_  when s e v e r a l of the  c o r r e l a t i o n , but by G^  i t is difficult  i n two  correlation (PBS  tall  congesta-. populations  the c o r r e l a t i o n s were  to d i s c e r n any  t r e n d from  the  of s e l e c t i o n .  correlations  o t h e r c o r r e l a t i o n s can be d i v i d e d  i n t o t h r e e broad  some c a s e s , the c o r r e l a t i o n s d i f f e r e d between the P. P. brachystemon l i n e s .  groups.  congesta  In  l i n e s and  the  In the c o r r e l a t i o n s between h e i g h t a t a n t h e s i s  and  number of p r i m a r y branches ( F i g u r e 24), number of nodes and number of  primary  branches ( F i g u r e 25), and h e i g h t at a n t h e s i s and f r u i t p r o d u c t i o n  (Figure  the c o r r e l a t i o n s  the  correlations  i n the PBS  i n the PCO  l i n e s were s t r o n g and p o s i t i v e , w h i l e  and PCS  l i n e s were mostly  not s i g n i f i c a n t and  not  c o n s i s t e n t l y p o s i t i v e or n e g a t i v e . In some cases  the c o r r e l a t i o n s were e s s e n t i a l l y s i m i l a r in. a l l t h r e e  s p e c i e s groups and m o s t l y  not s i g n i f i c a n t , or when s i g n i f i c a n t not  26)  Figure  23.  C o r r e l a t i o n s between h e i g h t  at anthesis  and  flowering  time.  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed f o r every population. a t the 5%  C o r r e l a t i o n c o e f f i c i e n t s which are  l e v e l are j o i n e d by a continuous l i n e ;  broken a t those g e n e r a t i o n s s i g n i f i c a n t at the 5%  significant lines  i n which the c o r r e l a t i o n was  level.  a. C o r r e l a t i o n s i n PCO  populations.  b.  C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  are not  93  early  X v ? : late S.\. t a l l V short early N  ^  G e n e r a t i o n s of s e l e c t i o n Control Height Anthesis  late early tall short  F i g u r e 24.  C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and number of primary branches a t a n t h e s i s . coefficient coefficients  Spearman's rank c o r r e l a t i o n  i s graphed f o r every p o p u l a t i o n .  Correlation  which are s i g n i f i c a n t a t the 5% l e v e l a r e j o i n e d  by a continuous  line;  l i n e s are broken a t those g e n e r a t i o n s  which the c o r r e l a t i o n was  not s i g n i f i c a n t  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  a t the 5%  level.  in  95  Figure  24.  late  .5  5 earl\ short a.  PCO  - tall  CO •H CO CU  Xi 4-1  0 c0_ 4J  n)  co cu Xi a  -.5  fl cd H >. H Cfl  •S M ft  .5 r _  CO >  b.  PCS  CO •rH. CO  tall late short early  cu  4-1  c cc)  4->  n)  -.5  1-  4-1  Xi  60 •H CU  Xi 4-1  late  a  cu  •H O •H  —  4-1  m cu  o o a o  c.  PBS  •H  cu H M O  -.Si-  I G e n e r a t i o n s of s e l e c t i o n Control Height  .  Anthesis  short tall early  -  F i g u r e 25.  C o r r e l a t i o n s between number o f nodes a t a n t h e s i s and number of p r i m a r y branches a t a n t h e s i s .  Spearman's rank c o r r e l a t i o n  c o e f f i c i e n t i s graphed f o r every p o p u l a t i o n .  Correlation  c o e f f i c i e n t s w h i c h a r e s i g n i f i c a n t a t the 5% l e v e l a r e j o i n e d by a c o n t i n u o u s  l i n e ; l i n e s a r e b r o k e n a t those g e n e r a t i o n s  w h i c h the c o r r e l a t i o n was  n o t s i g n i f i c a n t a t the 5%  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  level.  in  97  Figure  - 98  25. .5 CO  •w CO  cu  a.  PCO  Xi •U Ci  cd  CO cu Xi  a %  -.5  XI  >. u  cd  I a. CO  >  .5  CO •H CO <u Xi  b.  PCS CO Q)  O  d  -.5  I-  cu •H  a  <4-(  <-H (U O O  c  O •H J-l  short .5 r early  cd  rH (U  c.  PBS  rJ  o O  I -.5  G e n e r a t i o n s of  selection ..A  Control Height Anthesis  - 99 F i g u r e 26.  C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and f r u i t  production.  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed f o r population.  C o r r e l a t i o n c o e f f i c i e n t s which are s i g n i f i c a n t  the 5% l e v e l a r e j o i n e d by a continuous a t those g e n e r a t i o n s a t the 5%  every  line;  l i n e s are broken  i n which the c o r r e l a t i o n : was  level.  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  at  not  significant  F i g u r e 26.  -  .5  a.  short late early tall  PCO  o  -.5 I-  •rl 4->  a  T) O  u  PH  4J •H  3  H 4-1  .5  to >  early V" «short late - ' tall  CO  x  •H  b.  PCS  CO  cu  XI 4-1  a CO  xi  -.5  60 •rl 0)  Xi  cs d)  •rl CJ •rl  •4H  m  early y •==^^»-^_. l a t e ' short tall  .5  CU  o o c o  c.  PBS  •rl 4J n)  rH  cu  M rl o  CJ  -.51-  0 -  G e n e r a t i o n s of s e l e c t i o n Control Height Anthesis  100  c o n s i s t e n t l y p o s i t i v e or n e g a t i v e  w i t h i n a s p e c i e s group.  For  c o r r e l a t i o n s between days to emergence and h e i g h t a t a n t h e s i s days to emergence and number of nodes a t a n t h e s i s nodes a t a n t h e s i s and and  f r u i t production  f l o w e r i n g time ( F i g u r e 30)  p o s i t i v e , n o n - s i g n i f i c a n t , and same l i n e  101  example, (Figure  27),  ( F i g u r e 28), number of  ( F i g u r e 29), and  f l u c t u a t e between b e i n g  primary branches significant  s i g n i f i c a n t and n e g a t i v e ,  and  often within  ( f o r example, primary branches v s . f l o w e r i n g time i n PBS  the  short  shows t h i s k i n d of p a t t e r n ) , F i n a l l y , some of the c o r r e l a t i o n s were f o r the most p a r t i n a l l t h r e e s p e c i e s groups, and T h i s i s the case w i t h n e g a t i v e  remained so throughout the  experiment.  c o r r e l a t i o n s between days to emergence  number of p r i m a r y branches ( F i g u r e 31), days to emergence and ( F i g u r e 32), and  flowering  significant  time and  f r u i t production  (Figure  fruit  and  production  33).  S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s were observed c o n s i s t e n t l y between days to emergence and  flowering  time, w i t h  the e x c e p t i o n  l i n e s , i n which the c o r r e l a t i o n d i s a p p e a r e d nodes and  of  and  G,. i n the  ( F i g u r e 34), between number of  f l o w e r i n g time ( F i g u r e 35), number of p r i m a r y branches and  production  ( F i g u r e 36), and h e i g h t  the e x c e p t i o n  i n G^,  i n which the c o r r e l a t i o n  37).  I t must be remembered t h a t these are p h e n o t y p i c , r a t h e r than c o r r e l a t i o n s , and  as such are s u b j e c t  t h e r e does not appear to have been any between the v a r i o u s  to e n v i r o n m e n t a l e f f e c t s . change i n any  genotypic, Nevertheless,  of the c o r r e l a t i o n s  c h a r a c t e r s which c o u l d be a t t r i b u t e d to the e f f e c t s  of s e l e c t i o n , except perhaps i n the case of the c o r r e l a t i o n s between selected  fruit  a t a n t h e s i s and number of nodes, w i t h  of some of the p o p u l a t i o n s  dropped ( F i g u r e  PBS  characters.  the  -  Figure  27.  C o r r e l a t i o n s between number of days t o emergence and at anthesis.  s i g n i f i c a n t a t the 5%  C o r r e l a t i o n c o e f f i c i e n t s which are l e v e l are j o i n e d by a continuous  l i n e s are broken a t those g e n e r a t i o n s not  height  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed  f o r every population.  was  102  s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  line;  i n which the c o r r e l a t i o n  Figure  a.  PCO  - 103  27.  cn cn cu  •H  xi  •U c cO ^3 60  •r4 CU  X! CO  b.  PCS  > cu CJ C cu  60 H CU  a cu cn >> CO  .  T3  4-1  a  cu  •H  c.  PBS  a  •H  4-1  <4-l CU O CJ  early tall hort ate  C o  •H  4-1  cd  rH CU H H O O  Generations of  Control Height Anthesis  selection  -  Figure  28.  C o r r e l a t i o n s between number of days to emergence and of nodes a t a n t h e s i s .  Spearman's rank c o r r e l a t i o n  i s graphed f o r e v e r y p o p u l a t i o n .  Correlation  104  number coefficient  coefficients  which are s i g n i f i c a n t a t the 5% l e v e l a r e j o i n e d by a c o n t i n u o u s line; was  l i n e s are broken at those g e n e r a t i o n s  not  s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b.  C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  i n which the  correlatic  Figure 28.  .5  Generations of selection Control Height Anthesis  105  - 106 F i g u r e 29.  C o r r e l a t i o n s between number of nodes a t a n t h e s i s and production.  fruit  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed  f o r every p o p u l a t i o n .  C o r r e l a t i o n c o e f f i c i e n t s which are.  s i g n i f i c a n t a t the 5% l e v e l a r e j o i n e d by a continuous l i n e s a r e broken a t those g e n e r a t i o n s was  not s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  i n which the  line;  correlation  Figure  29. .5  " late' a.  PCO  a^, . e a r l y :short tall a o  •rl 4J O  -.5 I  0  'U  o u o.  4-> •rl P  u  4-1  CO  >  b.  PCS  CO •rl CO QJ XI 4-1  — -~  :  late early tall  c  cd  short  -4-1  cd CO  a) o a 4->  C  CU •rl  a  •rl m  <4H  o  early  .5  CJ  o  •rl  c.  PBS  ' late  (U i-l  O CJ  3  -.5  r  G e n e r a t i o n s of s e l e c t i o n Control Height Anthesis  Figure  30.  C o r r e l a t i o n s between number of p r i m a r y branches a t and  flowering  time.  Spearman's rank c o r r e l a t i o n  graphed f o r e v e r y p o p u l a t i o n . are s i g n i f i c a n t a t the 5%  correlation  was  not  anthesis  coefficient i s  Correlation coefficients  which  l e v e l are j o i n e d by a continuous  l i n e ; l i n e s are broken a t those g e n e r a t i o n s s i g n i f i c a n t a t the 5%  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  i n which level.  108  the  Figure  30.  -  .5i  a.  PCO  -.51  short  0 S  •rl  60 •rl  u CD  O  CO  > b.  PCS  CO CD  x; o  "S u >. M ec)  & !-l  a CD  •rl  o •rl m a) o o cl o •rl  c.  PBS  short f -. e a r l y '" t a l l late  CD  u  o CJ  Pi  Generations of Control Height Anthesis  selection  109  Figure  31.  C o r r e l a t i o n s between number of days to emergence and of p r i m a r y branches a t a n t h e s i s . coefficient coefficients  Spearman's rank c o r r e l a t i o n  i s graphed f o r every p o p u l a t i o n . which are s i g n i f i c a n t  by a continuous l i n e ;  number  a t the 5%  Correlation l e v e l are  joined  l i n e s are broken a t those g e n e r a t i o n s  which the c o r r e l a t i o n was  not  significant  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  a t the 5%  level.  in  110  Figure  31.  .5  a.  PCO  co QJ  tall  -.5  o  44  a  rt H rQ >,  H  rt  s  • CO rl H >ft  b.  PCS  a) o cu  \  C  —  60  H  _____  a)  a  cu _ o  x - ^ c r —  -.5  i early JxC late — s h o r t tall :  4J  CO  rt  e  QJ •A U •H 4-1 4H CU O CJ  .5  (3  O •H  c.  PBS  cu  u u o o u  Pi  early tall short  -.5 +  Generations of Control Height Anthesis  selection  F i g u r e 32.  C o r r e l a t i o n s between number of days to emergence and production.  fruit  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed  f o r every p o p u l a t i o n .  C o r r e l a t i o n c o e f f i c i e n t s which are  s i g n i f i c a n t a t the 5% l e v e l are j o i n e d by a continuous l i n e s a r e broken a t those g e n e r a t i o n s was  112  not s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations  i n which the  line;  correlation  Figure  a.  32.  -  PCO • late tall short  a  o  •H 4-1 O 3  early  -.5  T)  O  5-I  PH  4J •H 3  U  4-1  > cu a b.  PCS  0) 60  cu § 4-1 CO >^  a)  —  -.5  short -~"= l a t e early tall =  T3.  4-1 Cl CU •H CJ •H  <4-l  m cu o a CJ  o  •H  c.  PBS  (U !-l U  :••  O  a  Pi  -.5 Generations of Control Height Anthesis  selection  early - r :• s h o r t tall — - late  113  - 114 Figure  33.  C o r r e l a t i o n s between f l o w e r i n g  time and  fruit  production.  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed f o r every population.  C o r r e l a t i o n c o e f f i c i e n t s which are s i g n i f i c a n t  the 5% l e v e l are j o i n e d by. a continuous l i n e ; a t those g e n e r a t i o n s  l i n e s are broken  i n which the c o r r e l a t i o n was  a t the 5% l e v e l .  a. C o r r e l a t i o n s i n PCO  populations.  b.  C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  at  not  significant  F i g u r e 33.  a.  PCO late o  •H •U CJ  »—^ e a r l y *' s h o r t tall  -.5  s  13  O M ft U •H 3  H  m CO  > b.  PCS  c  M H QJ_ & O  4H  .5  I-  S CD •H O •rl 4-1 HH  <u o o  (3  O •H  0 .5 i-  cu  c.  PBS  u u o o  ~ —  Ai  u  1  short early tall  Pi  -.5  I-  late  G e n e r a t i o n s of s e l e c t i o n Control Height  —  Anthesis  —  - 116 Figure  34.  C o r r e l a t i o n s between number of days to emergence flowering  time.  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s  graphed f o r every p o p u l a t i o n . are s i g n i f i c a n t a t the 5%  C o r r e l a t i o n c o e f f i c i e n t s which  l e v e l are j o i n e d by a continuous  l i n e s are broken a t those g e n e r a t i o n s was  not  and  s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b.  C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  line;  i n which the c o r r e l a t i o n  F i g u r e 34-.  .5  h  tall early short late a.  PCO  G e n e r a t i o n s of Control Height Anthesis  selection  - 118 Figure  35.  C o r r e l a t i o n s between number of nodes a t a n t h e s i s flowering  time.  and  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s  graphed f o r every p o p u l a t i o n .  C o r r e l a t i o n c o e f f i c i e n t s which  are s i g n i f i c a n t at the 5% l e v e l are j o i n e d by a continuous l i n e s are broken a t those g e n e r a t i o n s was  not  s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  line;  i n which the c o r r e l a t i o n  Figure  35-.  Control Height Anthesis  -  F i g u r e 36.  C o r r e l a t i o n s between number of primary and  f r u i t production.  branches a t a n t h e s i s  Spearman's rank c o r r e l a t i o n  i s graphed f o r every p o p u l a t i o n .  coefficient  Correlation coefficients  which are s i g n i f i c a n t a t the 5% l e v e l a r e j o i n e d by a l i n e ; l i n e s a r e broken a t those g e n e r a t i o n s correlation  was  120  not s i g n i f i c a n t a t the 5%  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  i n which  level.  continuous the  Figure  36.  Generations of Control Height Anthesis  selection —  - 122 F i g u r e 37.  C o r r e l a t i o n s between h e i g h t a t a n t h e s i s and number of nodes at anthesis.  Spearman's rank c o r r e l a t i o n c o e f f i c i e n t i s graphed  f o r every p o p u l a t i o n .  C o r r e l a t i o n c o e f f i c i e n t s which a r e  s i g n i f i c a n t at the 5% l e v e l are j o i n e d by a continuous l i n e s are broken a t those g e n e r a t i o n s was  not s i g n i f i c a n t a t the 5%  level.  a. C o r r e l a t i o n s i n PCO  populations.  b. C o r r e l a t i o n s i n PCS  populations.  c. C o r r e l a t i o n s i n PBS  populations.  i n which the  line;  correlation  - 1  F i g u r e 37.  .5  a.  PCO CO •rl CO  cu  xi  9 -.5 CO  cu o  T3  CO  >  late  cu  tall early short  CO •rl CO  Xi 4-1  b.  PCS  a cd  Xi oo •rl CU  a  cu o  •rl •H  14-1  cu o o s o  late  .5  •H  x  CU M  c.  PBS  U  o o Ai Pi  -.5 G e n e r a t i o n s of s e l e c t i o n Control Height , Anthesis  short tall early  Changes i n q u a l i t a t i v e  characters  A number of q u a l i t a t i v e f r u i t l i n e s , namely numbers and from g e n e r a t i o n  c h a r a c t e r s were r e c o r d e d  to g e n e r a t i o n , numbers and  The winged and w i n g l e s s  and  likely  p e r i o d , and  frequencies  I decided  the f r e q u e n c i e s t h a t the f r u i t  congesta  fruited plants  of the  various  f r e q u e n c i e s of v a r i o u s f r u i t  f r e q u n c i e s i n the e x p e r i m e n t a l  i n F i g u r e 11, and  F i g u r e s 7 to 10.  i n the P^  f r e q u e n c i e s of winged and w i n g l e s s  pubescence p a t t e r n s , and numbers and  presented  124  colours.  populations  are  of the pubescence p a t t e r n s i n c o l o u r s c o r i n g was  to have been s u b j e c t to s y s t e m a t i c  too  change over the s i x  arbitrary generation  so have not attempted to i n c l u d e an a n a l y s i s of t h i s c h a r a c t e r . .  There a r e d e f i n i t e l y d i f f e r e n t c o l o u r morphs i n t h i s s p e c i e s which,  like  the wing shape c h a r a c t e r are f a i r l y c o n s t a n t w i t h i n p l a n t s and v a r i a b l e between, but a more r e l i a b l e and devised  to work w i t h  o b j e c t i v e s c o r i n g procedure needs to  them.  Winged and w i n g l e s s  plant  There i s no evidence  frequencies  of a n y t h i n g  other  than random d r i f t  the phenotype f r e q u e n c i e s a t the f r u i t wing l o c u s . divergence  affecting  There i s no  consistent  or o t h e r r e l a t i o n s h i p between the p l u s and minus s e l e c t e d l i n e s ,  whether s e l e c t e d f o r f l o w e r i n g time of h e i g h t a t a n t h e s i s . i n v a r i a n c e i n the observed f r e q u e n c i e s the PCO  l i n e s and  among the l i n e s  from 0 to 0.043 i n the PCS  The  increase  (from 0 to 0.020 i n  l i n e s ) i s not  significantly  d i f f e r e n t from the d i s p e r s i o n expected to r e s u l t from random d r i f t to  be  0.022 i n 4 g e n e r a t i o n s )  (Falconer,  1960).  (from  0  - 125 Pubescence p a t t e r n s  The  s i t u a t i o n with  the pubescence p a t t e r n s i s s i m i l a r  the f r u i t wing phenotypes.  There i s no apparent p a t t e r n o r t r e n d i n the  f r e q u e n c i e s which might be e x p l a i n e d by o r a t t r i b u t e d procedure.  to that with  t o the s e l e c t i o n  I n t h i s case the i n c r e a s e i n v a r i a n c e among the PCO l i n e s appears  to be s l i g h t l y l a r g e r  than among the PCS l i n e s , p a r t i c u l a r l y i n pubescence  types 2, 3, and 4, b u t as the g e n e t i c mechanism c o n t r o l l i n g the c h a r a c t e r i s unknown, the change i n d i s p e r s i o n cannot be compared t o any t h e o r e t i c a l prediction,  as i t c o u l d i n the case o f the f r u i t wing l o c u s .  expected i n such r e l a t i v e l y s m a l l , i n b r e d p o p u l a t i o n s ,  As may be  the r a r e r  phenotypes  0 and 1 have been l o s t i n many o f the l i n e s .  Aberrant  The  characters  f r e q u e n c i e s o f the v a r i o u s i n d i v i d u a l s  o r c h a r a c t e r s observed a r e  presented  i n Table VII.  frequency  compared t o the f r e q u e n c i e s observed i n the base  The  The o v e r a l l t r e n d was towards an i n c r e a s e i n populations.  PCO l a t e and PCS s h o r t l i n e s had p a r t i c u l a r l y h i g h f r e q u e n c i e s o f  abnormal types, and the P. c o n g e s t a p o p u l a t i o n s produced s i g n i f i c a n t l y more abnormals than the P. brachystemon p o p u l a t i o n s The  G,_ source  2 (x^£^_ 67.95, p < 0.0001). =  p o p u l a t i o n s had low f r e q u e n c i e s o f a b e r r a n t  to the f r e q u e n c i e s observed i n the G^ base p o p u l a t i o n s ,  types,  similar  t o which they a r e  2 comparable (X _£_ (  = 1  0.85, p = 0.4).  Comparisons between the i n t e r n a l c o n t r o l p o p u l a t i o n s and the G^ population.  source  Table VII..  Frequencies of aberrant i n d i v i d u a l s . Cotyledons  Seedlings  Three PCO  PCS  Fused PBS  PCO  PCS  Chlorotic PBS . PCO  2  PCS  6  2  Habit Dark  PBS  PCO  Pigment PCS  PBS  Others PCO  •PCS  PBS  PCO  PCS  1  1  PBS  3  3  2  1  5  12  ' 5  6  2  2  3  1  1  5  7  12  15  2  !0  11  11  3  3  2  2  5  4  •6  9  1  4  4  1  1  9  3  2  1  1  15  12  3  7  9  5  2  2  26  14  3  2  8  8  10  1  Frequency PCS PBS  PCO  PCS  PBS  Total  452  453  304  1209  .020  .007  .003  .011  680  588  796  2004  .028  .029  .008  .020  •806  785  765  2356  .038  .046  .021  .035  837  799  872  2508  .017  .024  .003  .014  919  858  974  2751  .034  .024  .006  .021  932  909  915  2756  .033  .053  .019  .034  G,. s o u r c e  75  93  168  PCO  .013  0  Total  .006  - 127 The  two  P. brachystemon,  source p o p u l a t i o n s , one o f P. congesta and one o f were grown i n o r d e r t o i n v e s t i g a t e whether u n c o n t r o l l e d  s e l e c t i o n p r e s s u r e s , random d r i f t , internal control  o r o t h e r p r o c e s s e s had a f f e c t e d the  lines.  Quantitative characters  The  s t a t i s t i c s f o r the measured c h a r a c t e r s i n the PC source G^ and  PB source G,. p o p u l a t i o n s a r e p r e s e n t e d i n T a b l e V I I I , a l o n g w i t h the s t a t i s t i c s f o r the G^ c o n t r o l s , f o r comparison.  Plectritis  congesta  The P. congesta c o n t r o l l i n e s d i d n o t change s i g n i f i c a n t l y i n mean h e i g h t a t a n t h e s i s , number o f nodes a t a n t h e s i s , o r number o f primary branches a t a n t h e s i s over the course o f the experiment.  There was a s i g n i f i c a n t  decrease  i n mean number o f days t o emergence and i n days to a n t h e s i s , which may w e l l be the r e s u l t o f some s e l e c t i v e p r e s s u r e f o r a s h o r t e n e d l i f e under the crowded c o n d i t i o n s i n the e x p e r i m e n t a l p o p u l a t i o n s .  cycle  The p h e n o t y p i c  v a r i a n c e as e s t i m a t e d by the c o e f f i c i e n t o f v a r i a n c e was unchanged i n a l l c h a r a c t e r s except the number of primary branches a t a n t h e s i s , f o r which b o t h c o n t r o l l i n e s became s i g n i f i c a n t l y more v a r i a b l e , and f l o w e r i n g time, f o r which the PCS c o n t r o l l i n e became s i g n i f i c a n t l y more v a r i a b l e .  P l e c t r i t i s brachystemon  The P_^ brachystemon c o n t r o l p o p u l a t i o n s developed  significant  Table V I I I .  Measured c h a r a c t e r s : G  5  source p o p u l a t i o n s compared w i t h  control populations.  N  Mean  Standard deviation  Coefficien variation  Days to emergence PCO c o n t r o l  G  5  195  15.344  2.4198  15.77  PCS c o n t r o l  G  5  192  15.620  2.6101  16.71  18.554*  2.9477  15.89  15.829  2.7519  17.39  17.946*  2.8028  15.62  74  PC source G,_  PBS c o n t r o l  G  187  5  93  PB source G,.  H e i g h t a t a n t h e s i s (mm) PCO c o n t r o l  G  5  157  331.19  68.334  20.63  PCS c o n t r o l  G  5  165  339.05  61.979  18.28  73  315.92  53.351  16.89  153  524.42  84.939  16.20  444.07*  55.570  12.51**  PC source G,-  PBS c o n t r o l  G  5  89  PB source G<-  Number o f nodes a t a n t h e s i s PCO c o n t r o l  G  5  159  7.9686  0.9963  12.50  PCS c o n t r o l  G  5  164  8.1829  1.4197  17.35  73  7,8219  1.1942  15.27  1.0108  9.90  9.618*  0.9944  10.34  158  5.5506  3.7204  67.03  165  5.5212  3.8407  69.56  73  6.6301  3.5099  52.94**  PC source G^  PBS c o n t r o l  G  5  153 89  PB source G,.  10.209  Number o f primary branches PCO c o n t r o l  G  5  PCS c o n t r o l G,. PC source G^  PBS c o n t r o l PB source G,.  G  5  153  10.993  5.0945  46.34  89  11.775  7.3450  62.37**  Table V I I I ,  continued.  N  Mean  Standard deviation  Coefficient of variation  Days t o a n t h e s i s PCO c o n t r o l G  5  163  73.736  5.1169  6.94  PCS c o n t r o l G  5  174  75.167  6.4217  8.54  75.616*  4.4648  5.90** ( v s . PCS)  160  93.331  4.6415  4.97  91  88.835*  5.0514  5.69  PC s o u r c e G  PBS c o n t r o l G PB s o u r c e G  73  c  5  5  * Mean v a l u e s i n t h e s o u r c e p o p u l a t i o n s i n d i c a t e d d i f f e r e n t f r o m t h e c o n t r o l p o p u l a t i o n s a t t h e 5% ** C o e f f i c i e n t s significantly  are  significantly  level.  of v a r i a t i o n i n the source populations i n d i c a t e d are d i f f e r e n t f r o m t h e c o n t r o l p o p u l a t i o n s a t t h e 1%  level.  - 130 d i f f e r e n c e s from t h e source p o p u l a t i o n over  the course  of the experiment  f o r a l l the c h a r a c t e r s except number o f primary branches. of days to emergence decreased  significantly  The mean number  i n the c o n t r o l line;, and the  mean h e i g h t a t a n t h e s i s , number o f nodes at. a n t h e s i s , and days to a n t h e s i s all  i n c r e a s e d s i g n i f i c a n t l y w i t h r e s p e c t t o the source The v a r i a n c e o f the PBS c o n t r o l was s i g n i f i c a n t l y  a t a n t h e s i s , and s i g n i f i c a n t l y decreased  population. increased i n height  i n number of p r i m a r y branches a t  a n t h e s i s ; v a r i a n c e s f o r the o t h e r c h a r a c t e r s were unchanged*  Correlations  There were no s i g n i f i c a n t which suggested  c o r r e l a t i o n s i n the G,. source  populations  t h a t t h e r e had been any change i n the c o n t r o l l i n e  the course o f the experiment  (Table I X ) .  over  Table I X .  C o r r e l a t i o n s i n the G,. source  populations.  P. congesta  Height  at anthesis  -.2163  Nodes a t a n t h e s i s  -.2769*  0.1698  Primary branches  -.3123*  0.2056*  0.3121*  Days to a n t h e s i s  0.3443*  0.0174  0.6226*  -.0234  Days t o emergence  Height a t anthesis  Nodes a t anthesis  Primary branches  P. brachystemon  Height  a t anthesis  -.4984*  Nodes a t a n t h e s i s  -.2756*  0.2987*  Primary branches  -.2936*  0.3381*  0.3864*  Days to a n t h e s i s  0.1290  -.0137  0.4910*  0.0558  Days t o emergence  Height a t anthesis  Nodes a t anthesis  Primary branches  * C o r r e l a t i o n c o e f f i c i e n t s s i g n i f i c a n t a t the 5% l e v e l .  Summary of Breeding  132  results  system i n P l e c t r i t i s  Source p o p u l a t i o n s Plectritis  congesta  had  an e s t i m a t e d  P l e c t r i t i s brachystemon the o u t c r o s s i n g r a t e was assumed to be Experimental The P.  l e s s than  In  not e s t i m a t e d ,  but  5%.  populations congesta  outcrossed populations  o u t c r o s s i n g r a t e of 65%. had  61.6%.  o u t c r o s s i n g r a t e of  an e s t i m a t e d  The P.  (PCO)  congesta  o u t c r o s s i n g r a t e of 15%.  p o p u l a t i o n s ;(PBS) had  had  an  estimated  s e l f e d populations The P.  (PCS)  brachystemon  an assumed o u t c r o s s i n g r a t e of l e s s than  5%.  C h a r a c t e r i s t i c s of the base p o p u l a t i o n s The mean v a l u e s f o r days to emergence, h e i g h t at a n t h e s i s , number of nodes at a n t h e s i s , number of primary to  emergence, and  f l o w e r i n g time were g r e a t e r i n the P.  p o p u l a t i o n s than i n the P. was  branches at a n t h e s i s , days  congesta  populations.  P.  brachystemon  brachystemon  more v a r i a b l e f o r days to emergence, h e i g h t at a n t h e s i s  nodes at a n t h e s i s , l e s s v a r i a b l e f o r primary  branches and  and  flowering  time. Response to s e l e c t i o n Selected  characters  Height  at a n t h e s i s  Means The PCO  l i n e s d i v e r g e d 66%  control  (+ 41%,  diverged PBS  or 148 mm  92mm; - 25%,  78% or 175 mm  compared to  56mm); the PCS  (+ 27%,  61 mm;  - 51%,  l i n e s showed no d i v e r g e n c e , but e r r a t i c  r e l a t i v e to the  control.  the  lines 114 mm);  the  fluctuations  - 133 Variances There were no t r e n d s i n t h e changes i n v a r i a n c e as e s t i m a t e d by c o e f f i c i e n t s showed s i g n i f i c a n t  of v a r i a t i o n ;  some p o p u l a t i o n s  i n c r e a s e s , some s i g n i f i c a n t  decreases  r e l a t i v e to the c o n t r o l . Heritabilities In PCO t h e r e a l i s e d  h e r i t a b i l i t y ( b ) was e s t i m a t e d as c  2 h e r i t a b i l i t y from p a r e n t - o f f s p r i n g r e g r e s s i o n s (h )  0.53;  was e s t i m a t e d  as 0.45.  I n PCS b  = 0.58, h  2  = 0 . 4 4 . In c PBS n e i t h e r e s t i m a t e was s i g n i f i c a n t l y d i f f e r e n t from z e r o .  Components of v a r i a n c e Significant observed  between f a m i l y v a r i a n c e components were  i n most p o p u l a t i o n s .  changes i n t h e p a r t i t i o n i n g components over to a n t h e s i s  the course  There were no t r e n d s i n  o f between / w i t h i n f a m i l y o f the experiment.  ( f l o w e r i n g time)  Means The PCO l i n e s d i v e r g e d 33.5% or 31.8 days compared to the control  (+ 20%, 19 days; - 13.5%, 12.8 d a y s ) ; the PCS  l i n e s d i v e r g e d 28.7% or 27.3 days (+ 16.3%, 15.5 days; - 12.4%, 11.8 d a y s ) ; and t h e PBS l i n e s d i v e r g e d 21.5  18.5% o r  days (+ 12.2%, 14.2 days; - 6.3%, 7.3 d a y s ) .  Variances The  t r e n d i n a l l s i x s e l e c t e d l i n e s was towards a decrease  i n the v a r i a n c e o f f l o w e r i n g time as e s t i m a t e d coefficient  by the  of v a r i a t i o n .  Heritabilities In PCO b  = 0.77, h c  2  = 0.60; i n PCS b = 0 . 7 5 , h c  2  = 0.72;  - 134 and  i n PBS b  c  =0.49, h  2  = 0.42.  Components o f v a r i a n c e Significant observed  between f a m i l y v a r i a n c e components were  i n most p o p u l a t i o n s .  changes i n t h e p a r t i t i o n i n g  There were no t r e n d s i n  o f between / w i t h i n f a m i l y  components over the course o f the experiment. Unselected  characters  Days t o emergence There were no s t r o n g t r e n d s i n changes i n means o r v a r i a n c e s . 2 Heritability Height  (h ) was estimated  a t 0.49 i n PCO c o n t r o l l i n e ;  a t a n t h e s i s ( i n l i n e s s e l e c t e d f o r f l o w e r i n g time)  There was some d i v e r g e n c e  i n the means i n t h e P___ congesta  p l u s and minus l i n e s , but no t r e n d i n t h e means i n t h e PBS l i n e s . There were no t r e n d s i n t h e changes i n v a r i a n c e s . Number o f nodes a t a n t h e s i s There was marked d i v e r g e n c e except  i n t h e means f o r a l l l i n e s  PBS s e l e c t e d f o r h e i g h t a t a n t h e s i s .  a decrease  i n v a r i a n c e was observed,  Some t r e n d toward  particularly  i n lines  2 s e l e c t e d f o r f l o w e r i n g time.  Heritability  (h ) was  estimated  as 0.55 i n PCO, 0.57 i n PCS and 0.28 i n PBS. Number o f primary  branches a t a n t h e s i s  There was some d i v e r g e n c e for height at anthesis.  i n t h e means except  f o r PBS s e l e c t e d  There were e r r a t i c , changes i n t h e  means from g e n e r a t i o n t o g e n e r a t i o n r e l a t i v e t o the c o n t r o l s . There were no t r e n d s i n changes i n t h e v a r i a n c e s .  Heritability  2 (h ) was e s t i m a t e d  as 0.29 i n PBS c o n t r o l .  Days t o a n t h e s i s ( i n l i n e s s e l e c t e d f o r h e i g h t a t a n t h e s i s )  - 135 There was marked d i v e r g e n c e v a r i a n c e s i n t h e P.. congesta  i n means and a decrease i n l i n e s ; t h e r e were no trends i n  changes i n means, o r v a r i a n c e s i n the PBS l i n e s . Fruit.production There were no trends i n changes i n means o r v a r i a n c e s i n any of the l i n e s . Correlations There were many s i g n i f i c a n t c o r r e l a t i o n s , both p o s i t i v e and n e g a t i v e , among the measured c h a r a c t e r s .  The o n l y s i g n i f i c a n t  change i n c o r r e l a t i o n s over t h e course o f t h e experiment was t h e disappearance selected Qualitative  o f t h e s t r o n g p o s i t i v e c o r r e l a t i o n between the two  c h a r a c t e r s , h e i g h t a t a n t h e s i s and f l o w e r i n g  time.  characters  There was no evidence  of a n y t h i n g o t h e r than random d r i f t  affecting  the f r e q u e n c i e s o f the f r u i t wing phenotypes and f r u i t  pubescence  p a t t e r n phenotypes over the course o f t h e experiment.  There was  some evidence  o f an i n c r e a s e of a b e r r a n t  the P. congesta  types, p a r t i c u l a r l y i n  p o p u l a t i o n s , which might be a t t r i b u t e d t o i n b r e e d i n g .  -  136  Discussion  The  questions  t o w h i c h t h i s s t u d y was  addressed are:  1.  Is  a  p o p u l a t i o n o f i n b r e e d i n g p l a n t s more o r l e s s v a r i a b l e g e n e t i c a l l y t h a n p o p u l a t i o n of otherwise quantitatively  i d e n t i c a l outbreeding  i n h e r i t e d c h a r a c t e r s ; 2.  such characters  i n the  two  populations  does the g e n e t i c v a r i a b i l i t y compare t o o t h e r  estimates  The  species  experimental  Plectritis  as  plants with respect  reflect  estimated  by  t h e d i f f e r e n c e ; and  i n the  two  P_j_ b r a c h y s t e m o n a r e a s n e a r l y i d e n t i c a l a s  breeding  likely  are n e a r l y impossible  numbers r e p o r t e d Mill Hill  of n =  populations  to be.  t h a n 5%  Genetic  i n the P^ b r a c h y s t e m o n  variability  Direct  ( M o r e y , .1963; T a y l o r a n d  i n t h e P.  and  two  selfing habitat  T h e y b o t h h a v e chromosome  have the r e q u i r e d b r e e d i n g  an o u t c r o s s i n g r a t e o f 61.6% less  I n b o t h v e g e t a t i v e h a b i t and  to d i s t i n g u i s h .  16  How  populations?  s p e c i e s w i t h r e s p e c t i v e l y o u t c r o s s i n g and  they  3.  the response to s e l e c t i o n  sexually reproducing systems are  to  Does t h e r e s p o n s e t o s e l e c t i o n f o r  of genetic v a r i a b i l i t y  c o n g e s t a and  a  Brockman, 1966).  The  system d i f f e r e n c e s , w i t h  c o n g e s t a p o p u l a t i o n , and  a rate  of  population.  the response to s e l e c t i o n  responses  Plectritis  T h e r e i s no  congesta outcrossed  e v i d e n c e o f any  versus  P_j_ c o n g e s t a s e l f e d  d i f f e r e n c e between the  two  s.ets o f  congesta  - 137 p o p u l a t i o n s i n t h e i r d i r e c t response t o s e l e c t i o n f o r e i t h e r h e i g h t at a n t h e s i s o r flowering.time,, d e s p i t e an e s t i m a t e d  difference i n  o u t c r o s s i n g r a t e under t h e e x p e r i m e n t a l  c o n d i t i o n s o f about 50% (PCO t = 0.65,  PCS t = 0.15).  equal change i n t h e means, t h a t i s ,  a divergence  There was approximately  o f 66% i n PCO,.78% i n PCS p l u s and minus l i n e s s e l e c t e d f o r  h e i g h t a t a n t h e s i s , and of.33.5% i n PCO 28.7% i n PCS p l u s and minus l i n e s s e l e c t e d f o r f l o w e r i n g time. and  s e l f e d P. congesta  groups i n t h e trends i n the c o e f f i c i e n t s o f v a r i a t i o n ,  w i t h e r r a t i c changes i n both a g e n e r a l decrease  f o r the v a r i a b i l i t y o f h e i g h t a t a n t h e s i s , and  i n both f o r the v a r i a b i l i t y o f f l o w e r i n g time.  f i n a l l y , the estimates at a n t h e s i s  There was no d i f f e r e n c e between t h e o u t c r o s s e d  of h e r i t a b i l i t y were e s s e n t i a l l y the same  ( b : PCO = 0.53, PCS.= 0.58; h : 2  c  f o r height  PCO = 0 . 4 5 , PCS-= 0.44) and  f o r f l o w e r i n g time ( b : PCO = 0.77, PCS = 0.75; h : 2  c  PCO = 0.60, PCS = 0.72).  I t i s l i k e l y t h a t the s m a l l p o p u l a t i o n s i z e s i n t h e experiment combined w i t h the i n t e n s i t y of t h e s e l e c t i o n  And,  (N = 200)  (90%) t o produce a r a t e of  i n b r e e d i n g which swamped any d i f f e r e n c e s i n i n b r e e d i n g a t t r i b u t a b l e t o d i f f e r e n c e s i n the o u t c r o s s i n g r a t e s .  I n comparisons w i t h the P. brachystemon  p o p u l a t i o n s , t h e r e f o r e , I w i l l t r e a t the P. congesta  l i n e s e s s e n t i a l l y as  d u p l i c a t e s , and r e f e r t o them t o g e t h e r .  P l e c t r i t i s congesta  Height  v e r s u s P^ brachystemon  at anthesis  There was s i g n i f i c a n t d i f f e r e n c e between P_. congesta i n response t o s e l e c t i o n f o r h e i g h t a t a n t h e s i s .  and P___ brachystemon  The p l u s and minus  d i v e r g e d 66% i n PCO and 78% i n PCS, but no c o n s i s t e n t d i v e r g e n c e  lines  resulted i n  - 138 the PBS  l i n e s , which f l u c t u a t e d e r r a t i c a l l y .  between P.  congesta  There i s no d i f f e r e n c e  and P. brachystemon i n the changes i n the  v a r i a n c e , which were e r r a t i c i n a i l t h r e e s p e c i e s groups. h e r i t a b i l i t y e s t i m a t e s , however, r e f l e c t e d P.  congesta,  phenotypic  The  realised  the s i g n i f i c a n t response i n  which r e s u l t e d i n a r e a l i s e d h e r i t a b i l i t y of 55%  compared  to  an e s t i m a t e d h e r i t a b i l i t y of zero f o r P. brachystemon, which showed no response.  In e f f e c t  t h e r e appeared to be no  genetic variance i n height  at  a n t h e s i s a v a i l a b l e f o r s e l e c t i o n i n the P. brachystemon p o p u l a t i o n , but enough g e n e t i c v a r i a n c e p r e s e n t a s i g n i f i c a n t response.  i n the P_^_ congesta  p o p u l a t i o n s to r e s u l t i n  I t i s i n t e r e s t i n g .that•• w h i l e - t h e - e s t i m a t e d  v a r i a n c e f o r h e i g h t at a n t h e s i s i s g r e a t e r i n P. v a r i a n c e measured i n . t h e base p o p u l a t i o n s was  congesta,  the  significantly  v a r i a b i l i t y or p l a s t i c i t y i n the g e n e t i c a l l y l e s s v a r i a b l e P. to suggest  phenotypic  l a r g e r i n P.  brachystemon.. T h i s anomaly c o u l d be e x p l a i n e d by an i n c r e a s e d  There i s a body of evidence  genetic  phenotypic brachystemon.  t h a t h i g h l y homozygous organisms  may  be p h e n o t y p i c a l l y more v a r i a b l e as a r e s u l t of t h e i r homozygosity, or c o n v e r s e l y t h a t h e t e r o z y g o s i t y has variability  ( A l l a r d and Bradshaw, 1964;  Dobzhansky and W a l l a c e , I n a study  a b u f f e r i n g e f f e c t on  of P.  Baker, 1974;  1953,* F a l c o n e r ; 1960;  congesta,  Lerner,  phenotypic  Bradshaw, 1965*, 1954;  Lewontin, 1957).  s i x m e t r i c a l c h a r a c t e r s - h e i g h t , dry weight,  degree of b r a n c h i n g , number of primary  branches, number of secondary branches,  and number of nodes - were a l l more v a r i a b l e i n p l a n t s homozygous f o r e i t h e r the dominant or r e c e s s i v e a l l e l e a t the f r u i t wing l o c u s , than i n p l a n t s heterozygous at the same l o c u s .  Whether the p l a n t s were grown i n a warm,  dry environment, or i n a c o o l , \<ret environment, t h i s b u f f e r i n g e f f e c t h e t e r o z y g o s i s was  apparent  (Carey and Ganders, 1980;  In Limrianthes, Brown and J a i n  (1979) found  Carey,  t h a t the s e l f e d  of  unpublished). floccosa  -  139  showed more p h e n o t y p i c p l a s t i c i t y than the o u t c r o s s e d L. a l b a . Harding  et a l . (1974) found  s i m i l a r r e s u l t s working w i t h the Lupinus  nanus  group of s u b s p e c i e s , i n which the more h i g h l y s e l f e d s u b s p e c i e s were more v a r i a b l e p h e n o t y p i c a l l y than the o u t c r o s s e d s u b s p e c i e s .  Finally,  Avena  b a r b a t a , a more h i g h l y s e l f e d s p e c i e s than i t s r e l a t i v e , A. f a t u a , i s a l s o * more v a r i a b l e p h e n o t y p i c a l l y , but m a i n t a i n s l e s s g e n e t i c v a r i a b i l i t y responds  l e s s w e l l to s e l e c t i o n  Flowering  appeared  1970).  time  The d i r e c t response between the two  ( J a i n and M a r s h a l l j 1967,  to s e l e c t i o n f o r f l o w e r i n g time a l s o  s e l e c t i o n t h e r e was  c y c l e of s e l e c t i o n .  no a p p r e c i a b l e d i f f e r e n c e , w i t h PCO, P C S , and PBS  ( F i g u r e 14).  In the f i f t h  P. brachystemon p o p u l a t i o n s ceased  (PCO) and  28.7%  the  divergence  The phenotypic v a r i a n c e s ( F i g u r e 15)  f o l l o w e d a s i m i l a r p a t t e r n , w i t h a r e l a t i v e l y steady decrease f o u r c y c l e s f o r a l l t h r e e s p e c i e s groups. fifth  continued  ( P C S ) , but  to d i v e r g e , w i t h the f i n a l  of the c o n t r o l v a l u e .  lines  compared to  c y c l e , the P. congesta l i n e s  d i v e r g e , w i t h a f i n a l d i v e r g e n c e of. 33.5%  b e i n g o n l y 18.5%  only  Through the f o u r t h c y c l e of  r e s p o n d i n g e q u a l l y w e l l t o s e l e c t i o n and d i v e r g i n g about 20%  to  differed  s p e c i e s , b u t . t h e d i f f e r e n c e s were not marked, and  i n the f i f t h  the c o n t r o l  and  over the  first  The decrease c o n t i n u e d i n the  c y c l e i n the case of the P-. congesta, but not i n the case of P.  brachystemon, i n which the p h e n o t y p i c v a r i a n c e i n c r e a s e d a g a i n . r e a l i s e d h e r i t a b i l i t y e s t i m a t e s f o r f l o w e r i n g time showed e q u a l h e r i t a b i l i t y i n the PCO l e s s , but s t i l l  and PCS .lines  (0.77  and 0.75)  a p p r e c i a b l e h e r i t a b i l i t y i n the PBS l i n e s  Finally,  approximately and  slightly  (0.49).  A l l of  the evidence i n d i c a t e s t h a t there i s s u b s t a n t i a l g e n e t i c v a r i a n c e f o r  the  - 140 f l o w e r i n g time i n b o t h P l e c t r i t i s s p e c i e s , w i t h somewhat more i n P.  congesta than i n P. brachystemon.  brachystemon was and  The  s i m i l a r to t h a t of P.  f a c t t h a t . t h e .response of  congesta f o r t h e . e a r l y  then changed a b r u p t l y i n the f i f t h g e n e r a t i o n , may  genetic variance i s organized  generations,  i n d i c a t e that  d i f f e r e n t l y i n the s e l f e d s p e c i e s .  not unexpebted; s i n c e t h e r e i s so l i t t l e  P.  o u t c r o s s i n g i n P.  p o p u l a t i o n s , the g e n e t i c v a r i a n c e i n these p o p u l a t i o n s  the  This i s  brachystemon  c o u l d be  expected  to d e r i v e l a r g e l y from d i f f e r e n c e s between f a m i l i e s , t h a t i s , between or a number of r e l a t i v e l y h i g h l y homozygous l i n e s . would then r e p r e s e n t  s e l e c t i o n response  s e l e c t i o n of f a m i l i e s r a t h e r than i n d i v i d u a l s , and  d e p l e t i o n of the v a r i a n c e and  t a i l i n g o f f of the response would  r a p i d l y , p a r t i c u l a r l y i n small populations experiment.  The  one  In c o n t r a s t , P.  occur  such as those maintained  congesta c o u l d continue  the  to m a i n t a i n  i n this  genetic  v a r i a n c e between and w i t h i n f a m i l i e s , i n s p i t e of the s e l e c t i o n p r e s s u r e , by means of the recombination segregation  i n subsequent  coming d i r e c t l y from o u t c r o s s i n g , and  from  generations.  Confounding phenomena  1  There are a number of phenomena which c o u l d p o t e n t i a l l y confound e f f e c t s of d i r e c t s e l e c t i o n on f l o w e r i n g time and h e i g h t first  at a n t h e s i s .  i s sampling e r r o r ( g e n e t i c d r i f t ) , which c o u l d operate  d i r e c t i o n of s e l e c t i o n i n v e r y s m a l l p o p u l a t i o n s .  The  used i n t h i s experiment were l a r g e enough to reduce.to possibilities  that d r i f t  could a f f e c t  There i s , however, e v i d e n c e . t h a t the u n s e l e c t e d  characters.  The  against  selective  random p r o c e s s e s may  The the  pressures  insignificance  the c h a r a c t e r s under d i r e c t  the  the  selection.  have a f f e c t e d some of  f r u i t wing phenotype and  fruit  pubescence  - 141 p a t t e r n f r e q u e n c i e s i n c r e a s e d i n v a r i a n c e among the v a r i o u s P___ congesta l i n e s over the course o f the experiment, n o t i n c o n s i s t e n t w i t h t h a t expected certainly  and the i n c r e a s e i n d i s p e r s i o n was  t o r e s u l t from random g e n e t i c d r i f t ;  t h e r e seemed t o be no c o n n e c t i o n between the changes i n p a r t i c u l a r  l i n e s and the s e l e c t i o n p r e s s u r e . A second f a c t o r which might have a f f e c t e d the response the e f f e c t o f s e l e c t i v e f o r c e s accompanying the response artificial  s e l e c t i o n , which a c t t o counter or reduce  to s e l e c t i o n i s  t o the i n t e n d e d  t h a t response.  These  c o u l d i n c l u d e , f o r example, reduced v i a b i l i t y or reduced f e c u n d i t y i n the s e l e c t e d i n d i v i d u a l s o r t h e i r progeny i n p r o p o r t i o n t o the degree they depart from the c o n t r o l mean.  to which  There was some e v i d e n c e o f a decrease  i n v i a b i l i t y and f e c u n d i t y i n some o f the extreme i n d i v i d u a l s ,  especially  those i n d i v i d u a l s which were v e r y s h o r t and those which f l o w e r e d v e r y i n a l l t h r e e s p e c i e s groups. s u r v i v a l to produce cases noted,  S i n c e the c r i t e r i a f o r s e l e c t i o n i n c l u d e d  at l e a s t ten apparently v i a b l e f r u i t s  t h a t i s , PCS s h o r t G  counter s e l e c t i o n was reduced  late  3  (except i n those  and PBS s h o r t G ) the e f f e c t o f t h i s 3  somewhat.  There was no obvious r e d u c t i o n i n  the t o t a l p o p u l a t i o n r a t e s o f g e r m i n a t i o n , s u r v i v a l , f i t n e s s , or f r u i t p r o d u c t i o n i n the l a t e r g e n e r a t i o n s , and no n o t a b l e d i f f e r e n c e between P. congesta and P. brachystemon i n the d e l e t e r i o u s e f f e c t s o f s e l e c t i o n . A t h i r d f a c t o r which might have a f f e c t e d the d i r e c t response t o s e l e c t i o n i s inbreeding depression.  I n p a r t i c u l a r , t h i s might be expected  to have a f f e c t e d the o u t c r o s s e d P. congesta.  I n b r e e d i n g i n the e x p e r i m e n t a l  p o p u l a t i o n s , which was u n a v o i d a b l e w i t h such s m a l l p o p u l a t i o n s and heavy s e l e c t i o n , might r e s u l t i n an i n c r e a s e i n homozygosity r e l a t i v e l y u n f i t homozygous r e c e s s i v e genotypes. P. brachystemon these u n f i t genotypes  which c o u l d  produce  In a s e l f i n g species l i k e  would presumably have been s e l e c t e d  - 142 a g a i n s t and  e l i m i n a t e d from n a t u r a l p o p u l a t i o n s .  were i n v o l v e d i n the c h a r a c t e r s b e i n g would be  e q u i v a l e n t to the counter  I f the u n f i t homozygotes  selected, their deleterious effect  s e l e c t i o n mentioned above, except  that  the same i n b r e e d i n g d e p r e s s i o n would be expected to a f f e c t the c o n t r o l (unselected)  l i n e s more or l e s s e q u a l l y w i t h  some evidence aberrant  the s e l e c t e d l i n e s .  of i n b r e e d i n g e f f e c t s i n the i n c r e a s e i n frequency  i n d i v i d u a l s over the course  abnormal numbers of c o t y l e d o n s  of the experiment.  or f u s e d c o t y l e d o n s ,  Plants  chlorotic  There  was  of with  seedlings,  e x c e s s i v e l y pigmented s e e d l i n g s , and p l a n t s w i t h o t h e r a b n o r m a l i t i e s i n t h e i r h a b i t a l l i n c r e a s e d i n frequency, populations. frequency  There was  no evidence  that aberrant  i n the treatment p o p u l a t i o n s  populations, generations  though some l i n e s had (PCO  l a t e and PCS  p a r t i c u l a r l y i n the P. types  congesta  increased i n  any more than i n the c o n t r o l  p a r t i c u l a r l y high frequencies  short).  The  i n most  h i g h e r f r e q u e n c i e s n o t e d i n P.  congesta as compared to P. brachystemon were to be expected, s i n c e s e l f e d s p e c i e s would be l e s s l i k e l y in  the p o p u l a t i o n .  types,  The  to r e t a i n d e l e t e r i o u s r e c e s s i v e a l l e l e s  source p o p u l a t i o n s  comparable to the f r e q u e n c i e s  the  had  low  f r e q u e n c i e s of  aberrant  i n the G Q p o p u l a t i o n s .  I n d i r e c t responses to s e l e c t i o n  Unselected  There was  characters  c o n s i d e r a b l e change i n the u n s e l e c t e d  which c o u l d be a t t r i b u t e d to s e l e c t i o n . phenotypic  frequencies  response to random d r i f t  i n the P.  c h a r a c t e r s , some of  As mentioned above, the  fruit  congesta. l i n e s seemed to change more i n  than i n response to s e l e c t i o n p r e s s u r e .  I n most  - 143 of the m e t r i c a l c h a r a c t e r s , however, t h e r e were changes i n the means t h a t c o u l d be r e l a t e d to the s e l e c t i o n p r e s s u r e .  T h i s c o u l d be seen most  o f t e n as a d i v e r g e n c e between the p l u s and minus l i n e s , w i t h a l l t h r e e p l u s lines  (PCO,  PCS,  minus l i n e s . l i n e s was line,  and PBS)  In many c a s e s ,  the d i v e r g e n c e  not accompanied by a d i v e r g e n c e  corresponding  between the p l u s and minus  of both away from the c o n t r o l  t h a t i s , e i t h e r the p l u s or the minus l i n e i n these cases was  significantly different different in  having h i g h e r mean v a l u e s than the  from the c o n t r o l , though both were s i g n i f i c a n t l y  from the o t h e r s e l e c t e d l i n e .  each of the p l u s l i n e s was  c y c l e of s e l e c t i o n ,  except  Thus, days to emergence measured  g r e a t e r than i n the minus l i n e s by  i n the PBS  than i n the minus l i n e s except  the number of nodes a t a n t h e s i s was minus l i n e s ; number of primary lines  i n the PBS  fifth  i n the PBS  greater i n  l i n e s ; i n a l l cases  g r e a t e r i n the p l u s l i n e s  branches a t a n t h e s i s was  than i n minus l i n e s except  the  l i n e s selected f o r height at anthesis;  h e i g h t a t a n t h e s i s i n the l i n e s s e l e c t e d f o r f l o w e r i n g time was the p l u s l i n e s  not  than i n the  greater i n plus  l i n e s selected f o r height at  a n t h e s i s ; and f l o w e r i n g time i n those l i n e s s e l e c t e d f o r h e i g h t a t a n t h e s i s was  g r e a t e r i n the p l u s l i n e s  f r u i t p r o d u c t i o n was  than i n the minus l i n e s .  s u b j e c t to a l a r g e e r r o r , and I found no c o n s i s t e n t  t r e n d s which c o u l d be a t t r i b u t e d to The  fact  selection.  t h a t i n g e n e r a l the u n s e l e c t e d c h a r a c t e r s tended to t r a c k the  selected characters i s r e f l e c t e d the c h a r a c t e r s .  i n the r e l a t i v e l y s t r o n g c o r r e l a t i o n s among  Thus, f l o w e r i n g time and number of nodes a t a n t h e s i s were  s t r o n g l y c o r r e l a t e d , and Height  The measurement of  a t a n t h e s i s and  the c o i n c i d e n t changes i n mean v a l u e s r e f l e c t  f l o w e r i n g time were s t r o n g l y c o r r e l a t e d i n the  t h r e e g e n e r a t i o n s , which p r o b a b l y f l o w e r i n g time observed  e x p l a i n s the i n i t i a l d i v e r g e n c e  this. first  in  i n the p l u s and minus l i n e s s e l e c t e d f o r h e i g h t a t  anthesis.  144  Days to emergence and f l o w e r i n g time were s t r o n g l y c o r r e l a t e d ,  as were h e i g h t a t a n t h e s i s and number of nodes a t a n t h e s i s . do i n d i c a t e some degree of u n d e r l y i n g g e n e t i c l i n k a g e , then the u n s e l e c t e d c h a r a c t e r s may  have been due  I f the c o r r e l a t i o n s the response of  i n p a r t e i t h e r to a d i r e c t  w i t h the s e l e c t e d c h a r a c t e r s which were themselves responding  link  to s e l e c t i o n  (nodes a t a n t h e s i s , h e i g h t a t a n t h e s i s , and days to emergence c o r r e l a t e d w i t h f l o w e r i n g time i n l i n e s s e l e c t e d f o r the l a t t e r ;  f l o w e r i n g time  and  number of nodes a t a n t h e s i s c o r r e l a t e d w i t h h e i g h t a t a n t h e s i s i n l i n e s s e l e c t e d f o r the l a t t e r ) .  A l t e r n a t i v e l y an i n d i r e c t l i n k through one  of  the u n s e l e c t e d c h a r a c t e r s c o u l d c o n c e i v a b l y have produced the response (days  t o emergence c o r r e l a t e d w i t h f l o w e r i n g time i n l i n e s s e l e c t e d f o r  height at a n t h e s i s ) .  Other s e l e c t i o n s t u d i e s  The  r e s u l t s I observed  i n t h i s experiment are comparable to the  i n such o t h e r s e l e c t i o n experiments as were designed  similarly,  results  that i s ,  w i t h mass s e l e c t i o n i n a p o p u l a t i o n t h a t has not been r a d i c a l l y a l t e r e d i n i t s g e n e t i c c h a r a c t e r i s t i c s by i n b r e e d i n g outcrossing  ( i n outcrossed  ( i n s e l f e d t a x a ) , and where g e n e r a t i o n s  more or l e s s n a t u r a l b r e e d i n g There a r e few  taxa) or by  a r e produced by  a  programme.  r e p o r t s i n the l i t e r a t u r e of a l a c k of response to  s e l e c t i o n , l a r g e l y , I suppose, because s e l e c t i o n i s s u c c e s s f u l to some degree i n most c a s e s . 20),.the  21 cases i n o u t c r o s s e d  r e c o r d e d had of 14.8%  In the s t u d i e s mentioned i n the i n t r o d u c t i o n (pp. 17 taxa f o r which a per c y c l e response  was  an average change i n the mean v a l u e of the s e l e c t e d c h a r a c t e r  per c y c l e of s e l e c t i o n .  In the s e l f i n g  t a x a , the 15 cases where a  -  - 145 per c y c l e response, was. recorded-.had .an. average,, change i n t h e mean o f 8.3%  per c y c l e .  I f t h e two . . P l e c t r i t i s s p e c i e s a r e t r e a t e d i n t h e same way,  the average p e r c y c l e change i n . t h e -mean v a l u e of the t w o . s e l e c t e d c h a r a c t e r s was a p p r o x i m a t e l y 5% iri P. congesta and a p p r o x i m a t e l y 1% i n P.  brachystemon.  Some o f t h e s e l e c t i o n s t u d i e s r e p o r t e d i n the l i t e r a t u r e used t h e same c h a r a c t e r s as I . d i d , that, i s , h e i g h t and f l o w e r i n g time, a l t h o u g h h e i g h t was not always measured a t the same stage o f the l i f e  cycle.  I n Limnanthes  alba,  an o u t c r o s s e r , s e l e c t i o n . f o r h e i g h t r e s u l t e d i n a 6% change p e r c y c l e o f selection  ( J a i n , 1979) .  Three.studies.involved selection for height i n  s e l f e d t a x a , w i t h responses r e s p e c t i v e l y of 4.5% p e r c y c l e i n A v e n a . s a t i v a (Geadelmann and F r e y , 1975), 12.5% per c y c l e i n A. f a t u a  (Imam and A l l a r d ,  1965), and 2.8%.per c y c l e i n ' Sorghum.bicolor  (Foster et a l . ,  1980); the mean  response i n s e l f e d t a x a was 6.6% per c y c l e .  Both b r e e d i n g system  groups  had a response t o s e l e c t i o n f o r t h i s c h a r a c t e r s i m i l a r i n degree t o the response o f 7.2% p e r c y c l e  (+ 66% i n PCO, + 78% i n PCS a f t e r 5 c y c l e s ) noted  i n P___ c o n g e s t a . S e l e c t i o n f o r f l o w e r i n g time has b e e n . r e p o r t e d i n a number o f s p e c i e s . Among s e l f i n g t a x a , i n Avena s a t i v a Geadelmann and Frey (1975) found a response t o s e l e c t i o n of 22% per cycle;.Imam and A l l a r d  (1965) noted a  ;  response o f 20.5% per c y c l e i n A. f a t u a ; and i n Sorghum b i c o l o r F o s t e r e t a l . (1980) found a response of 0.6% p e r c y c l e . s a r s o n Murty  I n B r a s s i c a c a m p e s t r i s v a r . brown  e t a l . (1972) observed a response of 1.7% p e r c y c l e .  response i n these t a x a i s about  12%.per  The mean  c y c l e , which i s c o n s i d e r a b l y h i g h e r  than e i t h e r the 3% p e r c y c l e response i n P. congesta o r the 2% per c y c l e response i n P. brachystemon.  The l o n g e r . t h e s e l e c t i o n c o n t i n u e s , t h e lower  w i l l be the p e r c y c l e response, as t h e t o t a l response w i l l d e p l e t i o n of g e n e t i c v a r i a n c e .  decrease w i t h the  The two experiments w i t h Avena, i n which the  -  146  per c y c l e response w a s . r e l a t i v e l y , h i g h , i n v o l v e d only.one c y c l e of s e l e c t i o n , whereas the experiments w i t h Sorghum and and  Bfassica involved  10  3 cycles respectively. Allowing  f o r these d i f f e r e n c e s between experiments, the response to  s e l e c t i o n f o r the two  characters, height  and  f l o w e r i n g time, i n both P l e c t r i t i s  s p e c i e s would seem to f a l l w e l l w i t h i n the range of observed responses i n other p l a n t  species.  To answer the f i r s t  two  questions  posed.at the b e g i n n i n g  of  the  d i s c u s s i o n , the P l e c t r i t i s brachystemon p o p u l a t i o n , which i s h i g h l y has  inbred,  significantly  l e s s genetic v a r i a b i l i t y  f o r one  character, height  at a n t h e s i s , than the P.  congesta p o p u l a t i o n , which i s  h i g h l y outbred two  but  otherwise n e a r l y i d e n t i c a l ;  s p e c i e s i n l e v e l s of g e n e t i c v a r i a b i l i t y  to s e l e c t i o n f o r h e i g h t . genetic v a r i a b i l i t y  quantitatively inherited  the d i f f e r e n c e between the  i s r e f l e c t e d i n the  In c o n t r a s t , however, t h e r e i s  response  considerable  f o r the second q u a n t i t a t i v e l y i n h e r i t e d c h a r a c t e r ,  f l o w e r i n g time, i n both p o p u l a t i o n s ,  and  this,  too, i s r e f l e c t e d i n the  response to s e l e c t i o n f o r t h i s c h a r a c t e r .  The  and  i n P l e c t r i t i s are s i m i l a r to  s e l e c t i o n response f o r b o t h c h a r a c t e r s  those found i n o t h e r p l a n t The  third  q u e s t i o n was  compare t o the e s t i m a t e s quantitative  l e v e l s of g e n e t i c  variability  species. how  independent e s t i m a t e s  of g e n e t i c  variability  d e r i v e d from the response to s e l e c t i o n f o r the  characters.  Independent e s t i m a t e s  of g e n e t i c v a r i a b i l i t y  in Plectritis  There i s ample e v i d e n c e (based m a i n l y on isozyme data) to i n d i c a t e  two  - 147 that outcrossed  taxa are more d i v e r s e , t h a t i s , more h i g h l y heterozygous  and more polymorphic on average, .than are selfed..taxa. the s t u d i e s of Layton  (1980) i n P.  agreement w i t h t h i s .  He  populations  f o r the two  P. brachystemon. measured i n two concluded  c a l c u l a t e d Nei's  f o r P.  shape, and  and.0.06 f o r  Ganders and Maze ( u n p u b l i s h e d ) ' s t u d i e d f r u i t wing c h a r a c t e r s p o p u l a t i o n s of "P^ congesta  and  one  of P_;_ brachystemon  s p e c i e s was  and  significantly  species.  d i f f e r i n the amount of phenotypic  characters:  congesta  p a r t i c u l a r p o p u l a t i o n s chosen as sources  The P^ congesta  from  and P. brachystemon i s i n  t h a t the v a r i a b i l i t y i n the o u t c r o s s e d  two  evidence  index of gene d i v e r s i t y w i t h i n  s p e c i e s to be 0.22  g r e a t e r than t h a t i n the s e l f e d The  congesta  The  variability  p o p u l a t i o n at M i l l H i l l  f o r t h i s experiment  shown i n c e r t a i n c h a r a c t e r s .  i s polymorphic f o r a number of  fruit  presence or absence of f r u i t wings, pubescence p a t t e r n , wing fruit  monomorphic:  colour.  The P. b r a c h y s t e m o n . p o p u l a t i o n , i n c o n t r a s t , i s  a l l p l a n t s produce medium brown w i n g l e s s  f r u i t s w i t h the same  pubescence p a t t e r n . The base p o p u l a t i o n s , G Q , which are presumed to be.a unselected evidence  random o r  sample of genotypes i n the source p o p u l a t i o n s , a l s o p r o v i d e some  of d i f f e r e n c e s i n v a r i a b i l i t y .  F o r the measured c h a r a c t e r s  the  c o e f f i c i e n t s of v a r i a t i o n were s i g n i f i c a n t l y d i f f e r e n t between the two i n 5 of 6 c a s e s , w i t h the c o e f f i c i e n t b e i n g number of primary  branches at a n t h e s i s and  l a r g e r i n P.  congesta  f l o w e r i n g time,  and  species  f o r the  larger i n  P. brachystemon f o r number of days to emergence, h e i g h t at a n t h e s i s , and number of nodes at a n t h e s i s . are e s s e n t i a l l y p h e n o t y p i c , reduced  These c o e f f i c i e n t s are based on v a r i a n c e s which although  the environmental  by the use of a common c o n t r o l l e d environment.  component has  been  I t i s p o s s i b l e that  the g r e a t e r v a r i a b i l i t y shown by P^ brachystemon f o r t h r e e c h a r a c t e r s i s due  to p h e n o t y p i c  plasticity,  about w h i c h I w i l l say more l a t e r .  f i n a l evidence,  independent of t h e s e l e c t i o n . e x p e r i m e n t ,  between t h e two  species i n . v a r i a b i l i t y  heritability lines.  For  slightly  of  s e l e c t e d c h a r a c t e r s . (Table V) P . brachystemon  ( e s s e n t i a l l y none as compared to 45%  by h e r i t a b i l i t y  has  f o r height  f o r P___ c o n g e s t a ) ,  and  only  l e s s g e n e t i c v a r i a n c e f o r f l o w e r i n g time (42% as compared to 60-70%  for P . congesta).  For t h e . u n s e l e c t e d  few  of h e r i t a b i l i t y  good e s t i m a t e s  characters  ( T a b l e VI)  t h e r e are  to make a comparison between P .  and P . brachystemon p o s s i b l e , except anthesis.  for differences  from the p a r e n t - o f f s p r i n g r e g r e s s i o n s i n the t h r e e c o n t r o l the two  anthesis  The  comes from the e s t i m a t e s  c o n s i d e r a b l y l e s s g e n e t i c v a r i a n c e as e s t i m a t e d at  148  too  congesta  i n the case of the number of nodes at*  I n t h i s case the h e r i t a b i l i t i e s are comparable to those  estimated 2  for  f l o w e r i n g time, w i t h P . brachystemon showing l e s s g e n e t i c v a r i a n c e  (h  =  2 0.28)  than P . congesta  (h  = 0.55), but both  i a t e h e r i t a b i l i t i e s f o r the c h a r a c t e r .  The  for  these two  not  s u r p r i s i n g c o n s i d e r i n g the s t r o n g and  species having similarities  low  i n the  to  intermed-  heritabilities  c h a r a c t e r s , f l o w e r i n g time and number of nodes a t a n t h e s i s , i s  between them, which was  consistent positive  evident i n a l l experimental  correlation  populations  (Figure-35).  I t i s i n t e r e s t i n g t h a t the c o e f f i c i e n t of v a r i a t i o n f o r number of nodes at a n t h e s i s was  g r e a t e r i n P . brachystemon G ^ t h a n i n - t h e two  p o p u l a t i o n s , w h i l e the h e r i t a b i l i t y i s g r e a t e r i n P . congesta.  estimates  P . congesta G Q  i n d i c a t e that genetic-variance'  There are s i m i l a r anomalies which were  when comparing the r e s u l t s of the s e l e c t i o n experiment w i t h c o e f f i c i e n t s of v a r i a t i o n , and  noted  the G Q  they w i l l be d i s c u s s e d i n the f o l l o w i n g  sections. The  answer t o the t h i r d  q u e s t i o n posed a t the b e g i n n i n g  then, i s t h a t the independent evidence  of g e n e t i c v a r i a b i l i t y  of the d i s c u s s i o n , i n the  two  - 149 species i s equivocal.  'Most of., t h e . c h a r a c t e r s are more v a r i a b l e i n the  o u t c r o s s e d P.  than in.-the s e l f e d P...brachystemon. . These i n c l u d e  congesta  the isozyme and  f r u i t . phenotype . polymorphisms, and -  the phenotypic  variances  i n number of p r i m a r y branches'and f l o w e r i n g time i n the base p o p u l a t i o n s grown i n c o n t r o l l e d , a n d . i d e n t i c a l environments.  These c h a r a c t e r s agree w i t h  the l e v e l s of v a r i a b i l i t y i n h e i g h t at a n t h e s i s as observed to s e l e c t i o n .  The phenotypic  i n the response  v a r i a n c e s of days to emergence, h e i g h t  a n t h e s i s , and number of nodes at a n t h e s i s i n the G Q p o p u l a t i o n s are i n the P. brachystemon p o p u l a t i o n s than i n the P. I f we  assume t h a t the environmental  congesta  at higher  populations.  components are constant  i n both  species  (perhaps a tenuous assumption) then t h i s e v i d e n c e would i n d i c a t e t h a t was  more g e n e t i c v a r i a b i l i t y  the independent evidence  i n the s e l f e r than i n the o u t c r o s s e r .  agrees c l o s e l y w i t h the observed  levels  there  None of  of  approximately  e q u a l g e n e t i c v a r i a n c e in..both s p e c i e s i n response to s e l e c t i o n  for flowering  time.  The  e f f e c t s of b r e e d i n g  system on the p o p u l a t i o n g e n e t i c s t r u c t u r e of  Plectritis  The  two  s p e c i e s of P l e c t r i t i s a r e v e r y s i m i l a r i n h a b i t and h a b i t a t ,  but are w e l l d i s t i n g u i s h e d by t h e i r b r e e d i n g b i o l o g y and p o p u l a t i o n structure.  genetic  Isozyme s t u d i e s show t h a t the g e n e t i c d i v e r s i t y i s much g r e a t e r  i n t o t a l and w i t h i n p o p u l a t i o n s  i n P.  congesta  than i n P^ brachystemon;  most of the g e n e t i c d i v e r s i t y i n P. brachystemon i s between p o p u l a t i o n s (Laytori, 1980).. S i m i l a r l y , the g e n e t i c d i v e r s i t y i n the f r u i t  phenotypic  c h a r a c t e r s - p r e s e n c e of f r u i t wings ( f o r which the g e n e t i c s are known), pubescence p a t t e r n , wing shape, and  fruit  c o l o u r ( f o r which the g e n e t i c s  are  - 150 not known) - i s g r e a t e r i n P. populations.  congesta  populations  than i n P.  With r e s p e c t to the f r u i t phenotype c h a r a c t e r s , the M i l l  p o p u l a t i o n s of P l e c t r i t i s are t y p i c a l ,  t h a t i s , P.  congesta  h i g h l y polymorphic and P. brachystemon i s monomorphic. in  brachystemon  The  is relatively isozyme p a t t e r n s  these p a r t i c u l a r p o p u l a t i o n s have not y e t been s t u d i e d . A l a r g e l y w i n g e d - f r u i t e d p o p u l a t i o n of P__ brachystemon was  v a r i a b l e f o r f r u i t wing c h a r a c t e r s than two P.  congesta;  less  comparable winged p o p u l a t i o n s  t h i s comparison d e a l t w i t h the phenotypic  c h a r a c t e r s t h a t were measured, but to  Hill  v a r i a b i l i t y of  the p a r t i c u l a r c h a r a c t e r s are  have a s m a l l or n e g l i g i b l e environmental  of  the  certain  component (Ganders and Maze,  unpublished). The  phenotypic  v a r i a b i l i t y of the two M i l l H i l l p o p u l a t i o n s as  estimated  by the v a r i a n c e s i n the G^ p o p u l a t i o n s was  g r e a t e r f o r P. brachystemon i n  some cases and f o r P.  In the cases where the  congesta  i n others.  component of t h i s v a r i a n c e c o u l d be e s t i m a t e d , r e g r e s s i o n s or by  e i t h e r by p a r e n t - o f f s p r i n g  the response to s e l e c t i o n , P___ congesta was  v a r i a b l e taxon g e n e t i c a l l y , a l t h o u g h  the more  s i g n i f i c a n t genetic variance  i n d i c a t e d f o r P. brachystemon i n number of nodes a t a n t h e s i s and time.  In two  was flowering  cases, h e i g h t a t a n t h e s i s and number of nodes a t a n t h e s i s ,  P. brachystemon was than P.  genotypic  congesta,  more v a r i a b l e p h e n o t y p i c a l l y but l e s s v a r i a b l e g e n e t i c a l l y  a r e s u l t which can o n l y be e x p l a i n e d by p o s t u l a t i n g a  r e l a t i v e l y h i g h e r element of phenotypic l e a s t under the e x p e r i m e n t a l  plasticity  i n P___ brachystemon, a t  conditions.  P l e c t r i t i s brachystemon  P l e c t r i t i s brachystemon, a h i g h l y s e l f e d s p e c i e s , appears to have l o s t  - 151 g e n e t i c d i v e r s i t y as a consequence of h a v i n g system.  evolved  a selfing  breeding  I t has n o t l o s t a l l of i t s g e n e t i c v a r i a b i l i t y f o r some c h a r a c t e r s ,  however, and  t h e r e presumably has been some s e l e c t i o n p r e s s u r e  to  maintain  g e n e t i c v a r i a n c e i n f l o w e r i n g time and number of nodes a t a n t h e s i s , w h i l e g e n e t i c v a r i a n c e f o r h e i g h t at a n t h e s i s has been l o s t . between the low g e n e t i c d i v e r s i t y as e s t i m a t e d c h a r a c t e r s , and  from isozymes and  events which occur  Occasional  outcrossing  i n h a b i t u a l l y s e l f i n g populations w i l l continue  heterozygous i n d i v i d u a l s f o r a number, of g e n e r a t i o n s ,  the f o r c e s of random d r i f t ,  i n b r e e d i n g , and s e l e c t i o n .  g e n e t i c d i v e r s i t y i n the isozymes and a n t h e s i s c o u l d be reducing  to  s u b j e c t to  I n t h i s case the  low g e n e t i c v a r i a n c e i n h e i g h t a t  the r e s u l t of s e l e c t i o n a c t i n g on these  their variability.  Conversely,  low  (  characters,  the h i g h g e n e t i c v a r i a n c e i n  f l o w e r i n g time and number of nodes c o u l d r e p r e s e n t maintained  fruit  the presence of s i g n i f i c a n t g e n e t i c v a r i a n c e i n o t h e r  c h a r a c t e r s can be e x p l a i n e d i n a number of ways.  segregate  The d i f f e r e n c e  by o c c a s i o n a l o u t c r o s s i n g and  the l e v e l of v a r i a b i l i t y  segregation.  This  explanation  r e q u i r e s t h a t the g e n e t i c d e t e r m i n a n t s of f l o w e r i n g time and number of nodes be n e a r l y n e u t r a l , and  t h a t the o u t c r o s s i n g r a t e be h i g h enough  p o p u l a t i o n s i z e s l a r g e enough to permit types.  accumulation  None of these assumptions i s r e a s o n a b l e  of these  f o r P.  and  heterozygous  brachystemon  populations. A l t e r n a t i v e l y , the low g e n e t i c d i v e r s i t y i n isozymes and  low  genetic  v a r i a n c e i n h e i g h t a t a n t h e s i s c o u l d be m a i n l y the r e s u l t of the h i g h of i n b r e e d i n g , s m a l l p o p u l a t i o n s i z e , and  random l o s s of a l l e l e s .  levels  The  r e l a t i v e l y h i g h g e n e t i c v a r i a n c e i n f l o w e r i n g time and number of nodes c o u l d be  the r e s u l t of s e l e c t i o n f o r v a r i a b i l i t y .  random f o r c e s a c t i n g on isozymes i s s t i l l  The b a l a n c e  of s e l e c t i v e  and  a s u b j e c t of much debate, but  there  i s p r o b a b l y s e l e c t i o n a c t i n g on a t l e a s t some o f the l o c i , is likely  and  152  there  to be s e l e c t i o n a f f e c t i n g h e i g h t a t a n t h e s i s to some degree i n  natural populations.  It is likely  t h a t the a c t u a l s i t u a t i o n i n P.  p o p u l a t i o n s i s somewhere between the two s e l e c t i o n a c t i n g on isozymes  extremes.  brachystemon  There i s p r o b a b l y some  and h e i g h t , but the low l e v e l s of g e n e t i c  ;  v a r i a b i l i t y i n these t r a i t s r e l a t i v e to P.  congesta r e f l e c t l a r g e l y  e f f e c t s of b r e e d i n g system and random l o s s of v a r i a b i l i t y .  The  the  relatively  h i g h g e n e t i c v a r i a n c e i n f l o w e r i n g time and nodes a t a n t h e s i s i s p r o b a b l y m a i n t a i n e d by  selection.  S e l e c t i v e f o r c e s which m a i n t a i n v a r i a b i l i t y  i n v o l v e a number o f mechan-  isms. , Those which i n v o l v e m u t a t i o n , m i g r a t i o n , or d i s a s s o r t a t i v e mating sources of new  v a r i a b i l i t y are n o t l i k e l y  as  to be the major f o r c e s i n v o l v e d i n  the s h o r t term i n P. brachystemon p o p u l a t i o n s .  A form o f s e l e c t i o n which i s  more p l a u s i b l e i n t h i s l i g h t i s h e t e r o z y g o t e advantage.  Heterozygote  advantage can be used i n a narrow sense, r e f e r r i n g to an a b s o l u t e f i t n e s s advantage of a h e t e r o z y g o t e over homozygotes under a l l c o n d i t i o n s , or i n a broad sense, where the n e t f i t n e s s advantage of the h e t e r o z y g o t e o n l y appears  as the f i t n e s s v a l u e s o f the v a r i o u s . g e n o t y p e s  space.  Heterozygote  advantage has been demonstrated  change i n time or  to operate i n P.  congesta under some c o n d i t i o n s a t the f r u i t wing l o c u s (Carey and Ganders, 1980)  and may  species.  be a f a c t o r i n p r e s e r v i n g some of the polymorphism i n t h a t  In P. brachystemon, however, t h e r e are p r o b a b l y too  h e t e r o z y g o t e s produced  i n n a t u r a l p o p u l a t i o n s to p e r m i t  few  heterozygote  advantage to be a f a c t o r i n the maintenance o f g e n e t i c v a r i a n c e .  The  f r e q u e n c y of h e t e r o z y g o t e s a t the f r u i t wing l o c u s i n one p o p u l a t i o n was e s t i m a t e d to be l e s s than 3%  (Ganders  h e t e r o z y g o t e s observed a t polymorphic  et a l . ,  1977$; the frequency o f  isozyme l o c i i n P___ brachystemon  p o p u l a t i o n s averaged 0.45%  (Layton,  1980).  There i s some  that heterozygote  advantage may  maintain variance  ( A l l a r d , J a i n and Workman, 1968;  A l l of t h i s e v i d e n c e observed  153  evidence  be o p e r a t i n g i n some s e l f i n g s p e c i e s to J a i n and A l l a r d ,  1960).  comes from c h a r a c t e r s i n w h i c h the genotypes can  be  (monogenic or simply i n h e r i t e d c h a r a c t e r s ) . Maintenance of g e n e t i c  v a r i a n c e i n q u a n t i t a t i v e l y i n h e r i t e d c h a r a c t e r s by h e t e r o z y g o t e  advantage i n  a s e l f i n g s p e c i e s r e q u i r e s even h i g h e r r a t e s of p r o d u c t i o n of the  hetero-  zygotes  The most  than  those r e q u i r e d to m a i n t a i n monogenic polymorphisms.  l i k e l y form of s e l e c t i o n to m a i n t a i n populations  g e n e t i c v a r i a b i l i t y i n P_j_ brachystemon  i s some type of p a t t e r n i n g of the s e l e c t i v e p r e s s u r e s  time or i n space.  I f m i c r o h a b i t a t s and  their associated selection  either i n pressures  occur, p a t c h i l y or form a mosaic, then the s e g r e g a t i n g l i n e s which r e s u l t from the r a r e o u t c r o s s i n g events maintained,  i n P^ brachystemon p o p u l a t i o n s c o u l d be  h i g h l y homozygous w i t h i n each m i c r o h a b i t a t but w i t h  genotypes i n d i f f e r e n t m i c r o h a b i t a t s .  different  That g e n e t i c v a r i a n c e i s d i v i d e d  among a number of homozygous l i n e s i n jP^ brachystemon i s a l s o suggested the observed  form of the response to s e l e c t i o n f o r f l o w e r i n g time.  by  A  r e l a t i v e l y l a r g e response i n the e a r l y g e n e r a t i o n s , f o l l o w e d by a r a p i d t a i l i n g o f f i n the l a s t g e n e r a t i o n , c o u l d occur as the s e l e c t e d l i n e s were reduced  i n number and v a r i a n c e between the l i n e s was  selection.  I t i s p o s s i b l e t h a t an examination  l o c i simultaneously  no  longer a v a i l a b l e f o r  of a number of the isozyme  i n i n d i v i d u a l s from P. brachystemon p o p u l a t i o n s would  r e v e a l a number of l i n e s of d i f f e r e n t m u l t i l o c u s homozygotes;  the  levels  of isozyme polymorphism d i s c o v e r e d to date i n p o p u l a t i o n s would a l l o w f o r a maximum of 11 d i f f e r e n t homozygous l i n e s per p o p u l a t i o n a t 13 isozyme (Layton,  1980).  The  isozyme d a t a i n P l e c t r i t i s have n o t b e e n a n a l y s e d  t h i s way  to determine m u l t i l o c u s genotypes, but  :  t h e r e i s evidence  loci in  from o t h e r  predominantly s e l f i n g species f o r a population l i n e s o f homozygous genotypes.  s t r u c t u r e composed o f  I n Avena b a r b a t a  i n d i c a t e d t h a t i n some p o p u l a t i o n s  154  a number of s t u d i e s have  a few m u l t i l o c u s genotypes a r e p r e s e n t  i n excess over the expected f r e q u e n c y , and appear to be adapted t o d i f f e r e n t microhabitats 1972)*  w i t h i n the h a b i t a t ( A l l a r d e t a l . , 1972; Clegg  M u l t i l o c u s o r g a n i z a t i o n i n A__ f a t u a and F e s t u c a  populations  and A l l a r d ,  microstachys  has a l s o been s t u d i e d and a s i m i l a r s i t u a t i o n n o t e d  (Allard,  1975). The  question  t h a t f o l l o w s l o g i c a l l y from the o b s e r v a t i o n  of genetic  v a r i a b i l i t y i n P___ brachystemon i s why t h e r e might be such r e l a t i v e l y s e l e c t i o n to m a i n t a i n anthesis  v a r i a b i l i t y i n f l o w e r i n g time and number of nodes a t  i n the s p e c i e s , t o the p o i n t t h a t i t i s n e a r l y as v a r i a b l e as  P. c o n g e s t a. likely  strong  S i n c e P. brachystemon i s h i g h l y s e l f - p o l l i n a t e d ,  to be a c o n n e c t i o n  the o u t c r o s s e d  species.  there i s not  w i t h p o l l i n a t o r b e h a v i o u r as might be the case i n I n P. congesta, v a r i a b i l i t y i n f l o w e r i n g time (and  number o f nodes, which a r e c o r r e l a t e d ) c o u l d serve  to extend the f l o w e r i n g  p e r i o d i n the p o p u l a t i o n ,  thus d e c r e a s i n g  the chance o f poor f r u i t  to l a c k o f synchrony w i t h  the a c t i v i t y o f p a r t i c u l a r p o l l i n a t o r s .  s e t due This i s  p a r t i c u l a r l y l i k e l y i n a s p e c i e s l i k e P.,congesta which does n o t appear to r e l y on one major p o l l i n a t o r , b u t r a t h e r a number o f p o l l i n a t o r s . One p o s s i b l e e x p l a n a t i o n  f o r the advantage t o be gained  from v a r i a b i l i t y  i n f l o w e r i n g time i n P___ brachystemon i s t h a t i t r e f l e c t s v a r i a b i l i t y i n some p h y s i o l o g i c a l o r developmental c h a r a c t e r which i s s u b j e c t t o m u l t i n i c h e selection.  A l t e r n a t i v e l y , flowering  disruptive selection.  time may be d i r e c t l y s u b j e c t  to such  F o r example, i t i s p o s s i b l e t h a t i n m i c r o s i t e s which  dry e a r l y i n the season, e a r l y f l o w e r i n g i s s e l e c t i v e l y advantageous, w h i l e i n w e t t e r m i c r o s i t e s , d e l a y i n g f l o w e r i n g may maximize f e c u n d i t y .  -  155  In c o n t r a s t to the g e n e t i c v a r i a b i l i t y p r e s e n t i n f l o w e r i n g time are the r e l a t i v e l y h i g h e r l e v e l s of p h e n o t y p i c v a r i a b i l i t y f o r h e i g h t a t a n t h e s i s observed i n J?^ brachystemon, compared T h i s p l a s t i c i t y may  to those i n P_^ congesta.  be advantageous i n p o p u l a t i o n s exposed to a mosaic o f  s e l e c t i v e f o r c e s , or i t may merely be a n o n - a d a p t i v e s i d e e f f e c t o f the i n c r e a s e d homozygosity which has accompanied the e v o l u t i o n o f a h i g h l y s e l f e d b r e e d i n g system. t h e r e may  I f homozygous genotypes a r e by n a t u r e more p l a s t i c ,  have been no way  for  brachystemon to a v o i d the i n c r e a s e d  p l a s t i c i t y were i t to have proved d i s a d v a n t a g e o u s . Phenotypic p l a s t i c i t y  c o u l d be a d a p t i v e i n a number of ways.  I t could  make p h e n o t y p i c a l l y u n i f o r m a p o p u l a t i o n of p l a n t s which a r e g e n e t i c a l l y diverse, maintaining genetic v a r i a b i l i t y  i n the f a c e o f s t a b i l i z i n g  Bradshaw (1965) has l i k e n e d t h i s to the e f f e c t s of dominance  selection.  and g i v e s  examples i n which i t may be o p e r a t i n g , namely i n P l a n t a g o m a r i t i m a (Gregor,1956) and a number of s p e c i e s examined by T u r e s s o n (1922, 1925). phenotypic p l a s t i c i t y  Alternatively,  could allow phenotypic v a r i a b i l i t y i n a population of  p l a n t s which a r e g e n o t y p i c a l l y r e l a t i v e l y u n i f o r m .  T h i s i s the p o t e n t i a l  which has been a t t r i b u t e d to some h y p o t h e t i c a l weedy or c o l o n i z i n g  species,  which would be composed of one or more g e n e r a l - p u r p o s e genotypes, a t once h i g h l y homozygous and h i g h l y p l a s t i c  (Baker, 1974).  There a r e weedy s p e c i e s  which do e x h i b i t more p h e n o t y p i c v a r i a b i l i t y i n some c h a r a c t e r s than t h e i r non-weedy r e l a t i v e s . arvensis  Examples  a r e Sonchus o l e r a c e u s (weedy) v e r s u s S.  (Lewin, 1948) and Chenopodium album  (Cumming, 1959).  (weedy) v e r s u s C.  rubrum  S i m i l a r l y t h e r e a r e o t h e r s p e c i e s p a i r s i n which the  more g e n e t i c a l l y v a r i a b l e s p e c i e s i s l e s s p h e n o t y p i c a l l y v a r i a b l e of Limnanthes, L u p i n u s , and Avena mentioned on pages 138 and 139).  (species It i s  u n f o r t u n a t e t h a t t h e r e a r e no measurements of p h e n o t y p i c v a r i a n c e y e t  - 156 a v a i l a b l e f o r natural populations  o f P___ congesta and P. brachystemon,  so i t i s n o t p o s s i b l e to compare l e v e l s uniform  (growth chamber) c o n d i t i o n s , nor t o e s t i m a t e  phenotypic  plasticity  between p o p u l a t i o n s  i n nature.  The r e l a t i v e l y  the e x t e n t o f  large  differentiation  o f P. brachystemon i n isozyme p a t t e r n s  the p r e s e n c e o f s i g n i f i c a n t fact  o f v a r i a b i l i t y under n a t u r a l and  (Layton,  g e n e t i c v a r i a n c e i n some c h a r a c t e r s , and the  t h a t n e i t h e r P. congesta n o r P. brachystemon i s p a r t i c u l a r l y  or weedy, suggest t h a t the n o t i o n o f a s p e c i e s composed o f h i g h l y homozygous, h i g h l y p l a s t i c some s e l f i n g  1980),  aggressive  general-purpose,  genotypes which has been suggested f o r  s p e c i e s i s n o t an adequate d e s c r i p t i o n o f the s i t u a t i o n i n  P. brachystemon. O c c a s i o n a l o u t c r o s s i n g and m u l t i n i c h e s e l e c t i o n among the s e g r e g a t i n g lines  f o r the g e n e t i c determinants o f f l o w e r i n g time are' likely„to have been  important,adaptive  processes  - i n P. brachystemon.  I t i s not p o s s i b l e a t  the moment t o say whether the i n c r e a s e d phenotypic  variability  a n t h e s i s i n P. brachystemon i s o r i s n o t a d a p t i v e ,  o r whether low g e n e t i c  v a r i a b i l i t y and h i g h p h e n o t y p i c  v a r i a b i l i t y f o r h e i g h t i n P___ brachystemon  and h i g h g e n e t i c v a r i a b i l i t y and low phenotypic congesta a r e - d i f f e r e n t  Plectritis  The  i n height at  v a r i a b i l i t y f o r height  i n P.  s o l u t i o n s t o the same e v o l u t i o n a r y problem.  congesta  presence o f g e n e t i c v a r i a b i l i t y  i n f l o w e r i n g time, h e i g h t a t :  a n t h e s i s , and number o f nodes a t a n t h e s i s i n P. congesta i s easy to account for  as a consequence o f the p r o c e s s e s  of recombination  accompanying the h a b i t u a l o u t c r o s s i n g i n the s p e c i e s . say whether the l e v e l s  of v a r i a b i l i t y  so m a i n t a i n e d  and s e g r e g a t i o n I t i s impossible to  a r e more or l e s s  than  - 157 expected.  S i n c e the h a b i t a t s are s i m i l a r , presumably the same type  of m u l t i n i c h e s e l e c t i v e  p r e s s u r e s p o s t u l a t e d to be o p e r a t i n g i n P.  brachystemon would a l s o a f f e c t P.  congesta.  Populations  however, would n o t be a b l e to develop g e n e t i c a l l y  of the l a t t e r ,  differentiated  local  s u b d i v i d i o n s as e a s i l y , because of the m i x i n g e f f e c t of o u t c r o s s i n g . a d d i t i o n , u n l i k e P. brachystemon, P. which c o u l d t h e o r e t i c a l l y  support  congesta has  selection  a pollination  advantage has been shown to operate  brachystemon p o p u l a t i o n s . conclude t h a t the h i g h e r  f o r P.  a t l e a s t one  Given no evidence  of  the  inbreeding depression  P^_ congesta p o p u l a t i o n s  was  than i n the  to the c o n t r a r y ; one  l e v e l s of g e n e t i c v a r i a b i l i t y and  the  P.  may  outcrossed  advantageous  in Plectritis  d i f f e r e n c e s between the two  isozyme and  P l e c t r i t i s species i n breeding  the g e n e t i c s t r u c t u r e of t h e i r  i n b r e e d i n g i n P^ brachystemon h a v i n g  it  to m a i n t a i n  congesta.  have d e f i n i t e l y a f f e c t e d  Yet  the  Heterozygote  system which generates them are b o t h s e l e c t i v e l y  F u r t h e r study  The  congesta.  congesta p o p u l a t i o n s , and  more marked i n the e x p e r i m e n t a l  breeding  to i n c r e a s e  s e t ; the o r i g i n and maintenance of g e n e t i c v a r i a b i l i t y  i n f l o w e r i n g time i s e a s i l y e x p l a i n e d i n 7^  polymorphisms i n P.  biology  f o r greater v a r i a b i l i t y i n  f l o w e r i n g time i n response to p o l l i n a t o r b e h a v i o u r , r e l i a b i l i t y of f r u i t  In  decreased  f r u i t morph c h a r a c t e r s and  populations,  the g e n e t i c d i v e r s i t y  v a r i a n c e i n h e i g h t and number of nodes t h a t  not s a c r i f i c e d a l l of i t s sources  of  the g e n e t i c v a r i a n c e i n h e i g h t .  i s obvious from the g e n e t i c v a r i a n c e i n f l o w e r i n g time and  phenotypic  system  the  brachystemon  of v a r i a b i l i t y to i t s b r e e d i n g  has  system.  More study of both and  s p e c i e s i s warranted, to c l a r i f y  to answer what may  q u e s t i o n , namely, how  be  and why  both  system  species are e q u a l l y  present.  Experiments w i t h P. brachystemon c o u l d be designed whether t h i s taxon  systematic  P. brachystemon e v o l v e d a s e l f i n g b r e e d i n g  a t some p o i n t i n the p a s t , and how s u c c e s s f u l i n sympatry a t  the d i f f e r e n c e s  the fundamental e v o l u t i o n a r y and  and why  158  to determine  does i n f a c t have a p o p u l a t i o n g e n e t i c s t r u c t u r e a f f e c t e d  by a number of d i f f e r e n t m i c r o h a b i t a t s and m u l t i n i c h e s e l e c t i o n .  First,  m u l t i l o c u s isozyme genotypes c o u l d e a s i l y be determined f o r a p o p u l a t i o n . S i n c e 13 isozyme l o c i have a l r e a d y been s t u d i e d , and  expansion  number of l o c i a v a i l a b l e f o r c h a r a c t e r i z a t i o n i s q u i t e f e a s i b l e p e r s o n a l communication), one  of  the  (Layton,  s h o u l d be a b l e to d i f f e r e n t i a t e a number of  m u l t i l o c u s genotypes, i f p r e s e n t , even w i t h i n a r e l a t i v e l y i n v a r i a b l e brachystemon p o p u l a t i o n .  P.  If microhabitat patterning i s a factor i n a  p o p u l a t i o n , i t might be p o s s i b l e to d e t e c t a t l e a s t some of i t s dimensions w i t h s u i t a b l e measurements of p h y s i c a l f a c t o r s ( s o i l , m o i s t u r e ,  micro-  topography) and b i o t i c f a c t o r s ( c o r r e l a t e d p l a n t s p e c i e s ) , and r e l a t e  the  m u l t i l o c u s isozyme p a t t e r n s to p a r t i c u l a r m i c r o h a b i t a t s , as has been done w i t h o t h e r s p e c i e s ( A l l a r d e t a l . , 1972; w i t h sympatric  P.  congesta  Allard,  1975).  Since  p o p u l a t i o n s are p o s s i b l e , one  comparisons  c o u l d do the same  t h i n g w i t h t h a t s p e c i e s , to v e r i f y whether the e f f e c t of o u c r o s s i n g been to produce the expected without One  any  has  l a r g e r number of isozyme genotypes, but  s u b d i v i d e d p a t t e r n based on m i c r o h a b i t a t d i f f e r e n c e s .  of the most i n t e r e s t i n g experiments would i n v o l v e measurements of  the p h e n o t y p i c  v a r i a n c e i n n a t u r a l p o p u l a t i o n s of both  c h a r a c t e r s used i n t h i s experiment, i n o r d e r o c c u r r i n g l e v e l s of phenotypic  plasticity.  s p e c i e s f o r the  to e s t i m a t e  the n a t u r a l l y  For example, under  experimental  - 159 c o n d i t i o n s V\_ congesta was g e n e t i c a l l y more v a r i a b l e f o r h e i g h t than was P. brachystemon, b u t p h e n o t y p i c a l l y l e s s v a r i a b l e . measure the p h e n o t y p i c if  One c o u l d  variance f o r height i n n a t u r a l populations  the d i f f e r e n t l e v e l s o f g e n e t i c v a r i a b i l i t y  d i s s i m i l a r l e v e l s of phenotypic  t o see  t r a n s l a t e / i n t o s i m i l a r or  v a r i a b i l i t y under n a t u r a l c o n d i t i o n s .  As a f i n a l example, one c o u l d extend  the s t u d i e s t o o t h e r s p e c i e s i n  the genus, which because of t h e i r f l o r a l morphology a r e presumed t o be more h i g h l y s e l f e d than P^ congesta, P. congesta two  and to o t h e r s e c t i o n s o f the ranges o f  and P_j_ brachystemon.  There a r e r e p o r t s of p o p u l a t i o n s o f the  s p e c i e s i n ; t h e more s o u t h e r l y p a r t s of t h e i r ranges which a r e more  s i m i l a r to each o t h e r than a r e any t h a t have been s t u d i e d i n B r i t i s h Columbia (Morey, 1962). observed  T h i s appears to be the case i n some p o p u l a t i o n s  r e c e n t l y i n C a l i f o r n i a , and i t would be i n t e r e s t i n g t o see how  e x t e n s i v e the apparent i n t e r m e d i a c y p o p u l a t i o n g e n e t i c s and b i o l o g y . danger i n e x t e n d i n g  i s , i n terms o f b r e e d i n g  system and  J a i n ,et a l . (1970) have p o i n t e d out the  arguments from s t u d i e s o f a p o p u l a t i o n i n one a r e a to  o t h e r s p e c i e s o r o t h e r p o p u l a t i o n s i n the same s p e c i e s ; p o p u l a t i o n s o f P. congesta  i n the southern  p a r t o f the range appear to be f a r l e s s  polymorphic w i t h i n p o p u l a t i o n s f o r some f r u i t British  c h a r a c t e r s than a r e those i n  Columbia.  Implications f o r other  The  studies  e s t i m a t i o n and comparison o f l e v e l s and o r g a n i z a t i o n o f g e n e t i c  v a r i a b i l i t y i n r e l a t i o n to breeding  systems i n v a r i o u s organisms i s an  a c t i v e a r e a o f study among p o p u l a t i o n g e n e t i c i s t s . important  to d i s t i n g u i s h between p o t e n t i a l o r hidden  In this f i e l d  i t is  genetic v a r i a b i l i t y  - 160 ( g e n e t i c d i v e r s i t y ) and r e a l i s e d or f r e e g e n e t i c v a r i a b i l i t y variance).  In the two P l e c t r i t i s  r e l a t i o n s h i p was d i v e r s i t y , and  s p e c i e s s t u d i e d here,  observed between the b r e e d i n g  g e n e t i c d i v e r s i t y and  congesta,  a reasonably  good  system, the amount of  the l e v e l of g e n e t i c v a r i a n c e p r e s e n t  comparison to the o u t c r o s s e d P.  (genetic  genetic  i n a population.  In  the s e l f e d P. brachystemon has  l e s s g e n e t i c v a r i a n c e . . There i s , however,  less  still  c o n s i d e r a b l e g e n e t i c v a r i a n c e i n the P v brachystemon f o r a t l e a s t  one  c h a r a c t e r , f l o w e r i n g time, perhaps more than one would expect from such a h i g h l y s e l f e d organism, or on the b a s i s of the l a c k of d i v e r s i t y i n the isozymes.  Moreover, the l e v e l s of p h e n o t y p i c  v a r i a b i l i t y measured i n some  of the c h a r a c t e r s i n d i c a t e more v a r i a b i l i t y i n P. brachystemon than i n P. congesta;  t h i s may  be m i s l e a d i n g , however, as i n a t l e a s t one  at a n t h e s i s )  the d i f f e r e n c e i s caused by h i g h phenotypic  than g e n e t i c  variability.  case  (height  plasticity  In s t u d i e s where isozymes are b e i n g examined, i t i s important  rather  that a  l a c k of g e n e t i c d i v e r s i t y i n isozymes not be i n t e r p r e t e d to i n d i c a t e a g e n e r a l l a c k of g e n e t i c v a r i a n c e i n a l l c h a r a c t e r s , w i t h o u t evidence.  other  Isozymes have so f a r proved to be good i n d i c a t o r s of  l e v e l s of v a r i a b i l i t y , f o r i n s t a n c e between o u t c r o s s e r s and g e n e r a l ; n e v e r t h e l e s s , amounts of g e n e t i c v a r i a n c e which a r e from an e v o l u t i o n a r y p o i n t of view can be m a i n t a i n e d monomorphism.  Isozymes w i l l and  should  continue  supporting  relative  selfers in significant  along with  to be used to  isozyme estimate  p o p u l a t i o n g e n e t i c parameters because they are more n e a r l y e s t i m a t e s  of  the  genotype than a r e c h a r a c t e r s which have a l a r g e e n v i r o n m e n t a l component to their variation. examined, and  A l l e l e f r e q u e n c i e s a t many i n d i v i d u a l l o c i can  the sampling i s r e l a t i v e l y f a s t , easy, and p r e c i s e .  c o n t r i b u t i o n to the phenotype, o t h e r  be Their  than t h e i r e l e c t r o p h o r e t i c m o b i l i t y ,  - 161 i s o f t e n unknown, and t h e i r s e l e c t i v e v a l u e s a r e c o r r e s p o n d i n g l y difficult  to i n t e r p r e t .  When s t u d i e s a r e d i r e c t e d to v a r i a b i l i t y o f q u a n t i t a t i v e c h a r a c t e r s i n populations,  t h e r o l e s of g e n e t i c v a r i a n c e and p h e n o t y p i c  environmental variance should to  be a s s e s s e d  carefully.  p l a s t i c i t y or  L a c k i n g evidence as  the g e n e t i c components o f v a r i a n c e , i t may be tempting t o argue t h a t  an o u t c r o s s e d p o p u l a t i o n which i s p h e n o t y p i c a l l y more v a r i a b l e than a s e l f e d population i s expressing higher reasoning,  l e v e l s of genetic variance.  By t h e same  a s e l f e d p o p u l a t i o n t h a t i s more v a r i a b l e than an o u t c r o s s e d one  might be regarded  as e x h i b i t i n g c h a r a c t e r i s t i c a l l y h i g h e r  phenotypic  plasticity.  phenotypic  plasticity  observations  l e v e l s of  Some o f the e a r l i e r d e s c r i p t i o n s o f i n c r e a s e d i n weedy o r s e l f i n g p l a n t s p e c i e s have been based on  of phenotypic  v a r i a n c e i n comparison w i t h r e l a t e d non-weedy  or o u t c r o s s i n g s p e c i e s , and a r e n o t accompanied by an e s t i m a t e component o f the v a r i a n c e  ( f o r example Cumming,  1959 and Lewin, 1948).  L a t e r s t u d i e s , such as those w i t h Lupinus (Harding  e t a l . , 1974), Limnanthes  (Brown and J a i n , 1979),and Avena ( J a i n and M a r s h a l l , the g e n e t i c components; d i f f i c u l t  1970), have  estimated  as they may be to o b t a i n , such  estimates  do a g r e a t d e a l t o i n c r e a s e our c o n f i d e n c e  i n s p e c u l a t i o n s about t h e  c o n t r i b u t i o n o f g e n e t i c v a r i a n c e v s . phenotypic populations  of v a r i o u s  o f the g e n e t i c  p l a s t i c i t y i n s t r a t e g i e s of  species.  S e l e c t i o n experiments may: not be the f a s t e s t way t o study  the g e n e t i c  components of v a r i a t i o n i n q u a n t i t a t i v e l y i n h e r i t e d c h a r a c t e r s . f a s t e r to do l a r g e s c a l e b r e e d i n g common  I t may be  experiments o f the type which a r e  i n crop s c i e n c e and a g r i c u l t u r a l r e s e a r c h  c r o s s i n g methods and progeny t e s t i n g methods). the advantage o f s m a l l e r space requirements,  (various c o n t r o l l e d  S e l e c t i o n experiments have  and consequently  better control  - 162 of t h e e n v i r o n m e n t a l h e t e r o g e n e i t y may be p o s s i b l e . genetic variance  i n quantitative characters  e l e c t r o p h o r e t i c s t u d i e s , i f the p o p u l a t i o n a r e t o be f u l l y u n d e r s t o o d .  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The p l a n t s p e c i e s i n r e l a t i o n to h a b i t a t and H e r e d i t a s 6: 147 - 236.  the  climate.  - 168 Villegas,  C. T., C. P. W i l s i e , a n d K. J . F r e y . 1971. Recurrent s e l e c t i o n f o r h i g h s e l f - f e r t i l i t y i n v e r n a l a l f a l f a (Medicagd s a t i v a L . ) . C r o p S c i . 11: 881 - 883.  Z u b e r , M.  S., M. L. F a i r c h i l d , A. J . K e a s t e r , V. L. F e r g a s o n , G. F. K r a u s e , E. H i l d e b r a n d , a n d P. J . L o e s c h , J r . . 1971. E v a l u a t i o n o f 10 g e n e r a t i o n s o f mass s e l e c t i o n f o r c o r n earworm r e s i s t a n c e . C r o p S c i . 11: 16 - 18.  Between f a m i l y / w i t h i n f a m i l y v a r i a n c e a.  PCO  ratios  i n experimental  populations.  populations.  Treatment  Generation  rs t o irgence  .Height at anthesis  Nodes a t anthesis  Primary branches  Days t o anthesis  Fruit production  Control  1.02* 3.13 3.82 3.11 6.34  1.82 10.82 5.71 9.44 3.85  2.30 5.13 3.21 3.91 1.93  1.31* 4.16 1.28* 3.82 1.89  2.15 8.52 6.63 6.36 2.54  1.40* 2.93 1.53* 2.39  Early anthesis  1.54* 2.43 5.82 2.89 2.99  2.53 7.05 2.60 6.61 6.63  2.99 3.74 4.68 3.71 4.49  1.87 7.44 1.63* 3.52 3.15  1.40* 2.74 1.86 3.11 2.38  1.01* 2.34 2.22 1.79  Late anthesis  1.40* 1.91 2.35 4.00 3.22  4.58 3.43 8.14 3.36 5.30  2.23 4.01 2.56 4.76 3.75  1.75 1.37* 2.73 2.14 3.18  2.07 3.11 2.51 3.95 3.35  1.24* 1.74 1.12* 3.45  Short height  2.66 1.98 1.03* 1.79 3.61  3.49 2.66 2.87 4.09 5.43  2.90 3.11 5.31 5.22 4.83  2.56 2.31 3.20 1.58* 7.84  6.44 4.72 4.54 4.41 4.47  7.30 2.25 2.37 1.54*  Tall height  4.25 3.40 6.04 2.91 2.86  1.06* 4.72 3.33 4.17 1.80  2.26 1.87 3.58 6.14 5.86  2.75 2.28 0.75* 2.73 3.60  1.59* 2.97 2.69 5.15 2.95  1.04* 2.38 1.40* 1.57*  b.  PCS  Treatment  populations. Generation  Control  G  1  G G G 5 2  3  4  G  Early anthesis  Late anthesis  G G  1  G  3  G  5  Gj^ G„ G G  Short height  G G  G  Tall height  3  4  4 5  G G G  3  G 5 4  G  Days t o rgence  Height at anthesis  Nodes a t anthesis  Primary branches  Days t o anthesis  Fruit production  2.93 9.97 6.61 11.95 6.92  1.73 3.09 1.70 6.66 2.73  3.36 9.76 6.96 11.53 6.09  0.86 * 2.40 1.85 1.57 *  2.28 5.07 3.71 1.34 * 7.01  2.59 4.00 3.35 3.94 6.58  1.95 6.78 3.38 2.73 1.94  2.84 5.34 4.64 4.05 6.73  1.44 * 3.91 2.15 1.91  1.51 * 3.62 5.27 2.60 2.00  4.41 5.40 2.91 6.96 5.14  3.39 4.50 5.24 4.45 6.43  1.17 * 1.65 * 6.99 2.74 4.22  2.59 1.87 2.13 2.51 3.66  1.17* 2.48 1.24 * 3.48  2.52 2.04 3.96  1.57 2.67 5.39  7.50 6.06 8.40  4.63 2.74 6.44  6.20 4.97 8.88  1.23 * 4.59 2.26  1.60 *  5.83  15.09  4.24  6.59  1.17 * 1.17 * 2.42 1.87 1.63 *  3.41 3.06 3.83 7.53 4.22  3.74 5.53 10.71 6.24 4.00  2.48 2.54 2.44 4.63 2.12  6.88 5.40 4.80 4.35 4.40  1.68 * 2.92 6.16 3.75 3.17  4.99 6.03 3.07 5.99 5.37  1.77 2.20 9.78 1.65 * 3.02  3.72 3.47 1.13 * 2.06  c.  PBS  Treatment  populations. Generation  Days t o rgence  Height at anthesis  Nodes a t anthesis  Primary branches  Fruit production  4.47 3.57 6.53 5.60 1.39*  1.36* 3.29 2.19 3.03  1.36 * 2.84 1.92 3.69 3.43  2.58 6.07 2.04 3.67 1.44*  0.70* 2.85 1.94 4.86  8.63 1.34* 6.01 1.95 1.71*  3.19 1.31* 3.71 3.27 4.82  3.39 2.06 2.08 4.46  5.08 5.72 3.66  2.53 4.96 1.12*  Control  2.15 2.34 3.09 2.27 1.33*  4.66 21.49 5.13 2.81 2.42  3.23 5.18 3.64 3.18 1.88  Early anthesis  0.71* 4.03 1.67 3.95 1.59*  1.19 5.93 2.55 13.17 1.95*  2.81 2.98 2.15 3.08 1.90*  Late anthesis  1.32* 1.90 4.00 1.68 1.59*  7.91 4.41 3.92 2.88 2.09  1.84 2.17 2.12 2.60 1.36*  Short height  2.60 5.33 4.57  1.86 16.20 1.57*  5.16 4.37 5.06  2.79  1.39*  1.68  1.02*  2.47 1.78 1.54* 2.86 2.28  4.59 8.66 1.47* 5.85 3.49  4.31 2.78 4.30 8.57 1.63*  4.72 5.04 2.16 3.58 2.88  Tall height  Days t o anthesis  4.19 10.69 4.83 4.76 2.59  4.63 10.36 2.30  1.91 5.57 1.20* 2.80 10.22 10.57  3.97 1.92 1.38* 3.02  Coefficients  of v a r i a t i o n ,  unselected characters. -•  PCO  .  «d  PCS  PBS  §  a. Early  Days G  Q  G  Late  Short'  Tall  Early  Late  Short  Tall  Early  Late  Short  Tall  (Control) '  22.7  22.7  18.09  20.29  17.63  22.18  26.05  27.17  21.3  18.58  17.46  37.95  32.32  24.04  19.42  2  32.47  42.03  35.36  31.79  , 30.89  30.11  35.78  32.73  17.64.  20.58  37.59  39.42  G  3  18.85  26.09  35.10  25.66  21.62  28.01  27.43  24.90  29.82  28.07  26.31  28.21  24.38  27.48  24.86  23.32  24.4  16.98  39.76  22.38  35.73  37.95  39.76  32.36  G. 4  -  .  .  ;  .  5 '  Height GQ G  l  G  2  G G. 4 3  G  to'  t o emergence  G  G  '  at anthesis  (Control)  20.16  20.16  23.97  17.31.  18.13  17.39  18.46  138.76  28.15  16.53  17.62  .22.23  25.13  21.81  29.62  14.05 17.29  20.54 16.53  15.41 17.52  20.95 21.57  19.5 "30.11  •  -  22.2 19.9  5 to  - 173 A p p e n d i x 2,  continued.  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