Theoretical and Applied Genetics 43, 59-- 65 (I 973) | b y Spriuger-Verlag 1973
Evolutionary Trends in Vicia faba L. J o s e I. CUBERO I n s t i t u t o N a c i o n a l de I n v e s t i g a c i o n e s A g r a r i a s , Centro R e g i o n a l de A n d a l u c i a , C 6 r d o b a (Spain)
Summary. 1. Distances have been calculated between t h i r t y natural populations of Viciafaba. 2. The results strongly suggest the existence of a Central Nucleus from which different trends of evolution have arisen. 3. The Central Nucleus represents the equilibrium between different genetic tendencies ; this equilibrium is postulated for the primitive populations of this species. 4. Disturbance of this balanced system can be produced by cycles of cross and self-fertilization; recombinations following these cycles are the origin of new genetic combinations so t h a t a new equilibrium is reached with a new cycle of disturbance. 5. The Muratova classification is discussed. I t is not possible to give a new classification based on these concepts, because of the great number of possible lines of evolution. The species must be considered as a whole, because there are no genetic barriers of isolation, only geographical ones and no sterility barriers have been produced between the subspecies. 6. A description of the Central Nucleus of Evolution is given.
Introduction I t is k n o w n t h a t b r o a d a n d field b e a n s h a v e b e e n c u l t i v a t e d since p r e h i s t o r i c times, from I n d i a to t h e W e s t e r n M e d i t e r r a n e a n countries. T h e y h a v e also been c u l t i v a t e d in C e n t r a l E u r o p e a n d t h e B r i t i s h Isles. E x c e p t for t h e I n d i a n ssp paucijuga, p o p u l a t i o n s h a v e n o t been i s o l a t e d u n d e r n a t u r a l c o n d i t i o n s or b y m a n . Man h a s t a k e n this species f r o m t h e original region to some countries, b u t p a r t i a l allog a m y d e p e n d s on t h e i n d i g e n o u s p o p u l a t i o n s : t h e new v a r i e t y is " a s s i m i l a t e d " m o r e or less q u i c k l y b y t h e n a t i v e ones. Thus, Vicia/aba is g o o d m a t e r i a l for s t u d y i n g t h e e v o l u t i o n of d i f f e r e n t i a t i o n where t h e r e is n e i t h e r g e o g r a p h i c n o r r e p r o d u c t i v e isolation. T h e t a x o n o m y of Vicia [aba has been s p e c i a l l y s t u d i e d b y M u r a t o v a (193 t), b u t n o b o d y has w o r k e d on its d e v e l o p m e n t as a species. R e c e n t l y , t h e exis t e n c e of a s t r o n g c e n t r a l nucleus c o m p o s e d of t h e major a n d equina p o p u l a t i o n s h a s b e e n d i s c u s s e d (Cubero, 1970), minor a n d pauci~uga being c o l a t e r a l b r a n c h e s d i r e c t e d in o p p o s i t e d i r e c t i o n s in r e l a t i o n to t h e p o s i t i o n of t h e nucleus. The p r e s e n t r e s e a r c h was u n d e r t a k e n to t r y to u n d e r s t a n d t h e d i f f e r e n t e v o l u t i o n a r y s t a t e s of this species, t h a t is, its evolut i o n a l h i s t o r y in its o r i g i n a l region.
Natural populations often consist of mixed botanical varieties. No selection was done, except t h a t atypical seeds of each sample were eliminated. At the time of observation homogeneity or heterogeneity was recorded. Seventeen characteristics have been studied (Table 2). Twelve were eliminated because they were strongly correlated with others (Table 3). For the five characteristics (numbers 6, 7, 12, 14 and 15) selected, quadratic distances were obtained (Table 4) (Rao, 1952). Results The equina p o p u l a t i o n s are v e r y closely g r o u p e d t o g e t h e r (Table 4), w i t h m i n i m a l d i s t a n c e s b e t w e e n them. F u r t h e r , this g r o u p is t h e closest to t h e o t h e r s ; its c e n t r a l p o s i t i o n is e v i d e n t . O n l y s t r a i n 28 is n o t i n c l u d e d in this g r o u p b u t , n e v e r t h e l e s s , it lies near. Minor n u m b e r 32 is q u i t e i n t e g r a t e d . T h e p o s i t i o n of
r
Material and M e t h o d s T h i r t y natural populations of Vicia faba from several geographical points have been used for this study. Of these, fourteen are classified as major, twelve as equina, two as minor and another two as pauc(iuga (using M U R A T O V A taxonomy). The origins of these populations are given in Table 1 ; the origins of the Spanish ones can be seen in Fig. I.
Fig. 1. Origins of Spanish populations
j. I. Cubero: Evolutionary Trends in Vicia faba L.
6O
Table 1. Groups and origin of populations studied (sample number refers to the Insti-
tuto Nacional de Investigaciones Agron6micas collection)
equina, is a t h i r d major g r o u p
c o m p o s e d of 1 t 2 a n d t 2 2 (C-III) ; t h e r e is a s h o r t e r dis115 major Spain (Sevilla) 24 equina Spain (CAdiz) t a n c e from t h e first to second 116 major Spain (Sevilla) 25 equina Italy g r o u p t h a n from t h e t h i r d 122 major Spain (Alicante) 26 equina Spain (Valencia) 123 equzna Spain (Valencia) 27 equina Spain (CAdiz) to e i t h e r t h e first or t h e 28 equina Morocco 137 major Spain (Badajoz) second. 32 minor Spain (Valencia) 138 equ~na I t a l y Equina a n d t h e two first t38.1 equma Italy 94 equina Morocco major g r o u p s (C-I a n d C-II) 140 major Spain (CAdiz) 103 minor U.S.A. t42 equ,na Spain (CAdiz) 104 major Spain (Guadalajara) f o r m a s t r o n g nucleus (the 143 equ~na Spain (CAdiz) 107 major Spain (Granada) t h i r d major g r o u p could be 144 equma Spain (CAdiz) 109 major Spain (Granada) i n t e g r a t e d ) from w h i c h t h e 146 major Spain (Zaragoza) 110 major Spain (Caceres) rest of t h e p o p u l a t i o n s b r a n c h 171 paucijuga I n d i a 112 major Spain (L6rida) 172 paucijuga India i 13 major Spain (L~rida) (Fig. 3).These p o p u l a t i o n s are : 203 major Greece I 14 major Spain (Sevilla) a. Paucifuga p o p u l a t i o n s (group P). T h e two specimens s t u d i e d lie t o g e t h e r , t h e m o s t e x t r e m e s a m p l e b o t h 28 a n d 32 will be discussed later. No g r a p h i c a l being t72. I t is e a s y to see t h a t its e v o l u t i o n a r y r e p r e s e n t a t i o n of t h e e q u i n a r e l a t i o n s h i p is useful. Major r e l a t i o n s h i p s are m o r e c o m p l i c a t e d (Fig. 2). p a t h - w a y d i m i n i s h e d t h e c h a r a c t e r i s t i c s v a l u e s in r e l a t i o n to t h e o v e r a l l m e a n (Table 2 a n d 4). Two g r o u p s lie n e a r equina: t h o s e f o r m e d b y l l 0 , b. Minor p o p u l a t i o n s (group A). - - T h e minor 1t3 a n d 137 (C-I) on one h a n d , a n d 1t4, 115 a n d s a m p l e t03 also shows e x t r e m e c h a r a c t e r i s t i c s : its 203 (C-II) on t h e other. I t can be seen (Table 4) t h a t d i s t a n c e from t h e c e n t r a l g r o u p s is large, b u t in in some r e s u l t s a few of these p o p u l a t i o n s are i n c l u d a different d i r e c t i o n from paucifuga (Fig. 4) ; increased a m o n g t h e equina group. Also near, b u t w i t h ed c h a r a c t e r i s t i c s are flowers p e r node, leaflets p e r its c o m p o n e n t s c l e a r l y d i f f e r e n t i a t e d from those of Table Plant
2.
Seed
Pod
Sample Number
Group (I)
Height (dm)
Number Length of leaves (cm)
Width Width Number Weight (cm) thickness of seeds (gr)
Length (mm)
Width (mm)
Thickness Width length thickness
24 25 26 27 28 32 94 t03 1o4 t07 1c9 11o 112 t13 114 115 116 122 123 t37 138 t38-1 14o t42 143 144 146 171 172 203
B 13 ]3 B B A ]3 C C C IV C CI C III CI C II CII C C III B CI ]3 B C IV B B ]3 CIV P P C II
4,6 5,6 5,4 4,4 7,6 4,8 5,3 7,6 4,1 5,2 5,9 5,4 4,0 4,4 5,3 4,8 4,3 4,0 6,0 5,O 5,2 4,9 3,5 4,7 4,5 5,1 5,0 3,0 2,5 4,1
16,4 16,8 15,6 14,6 20,4 t6,o 13,7 23,0 t3,1 11,9 18,8 13,4 12,1 12,9 13,8 14,7 t2,3 t0,4 19,8 12,5 t5,2 12,1 12,3
1,5 1,6 1,6 1,5 t,3 1,2 1,4 t,I 2,1 2,5 2,t 2,2 2,2 2,2 2,2 2,2 2,2 2,2 1,4 2,0 1,5 1,6 2,2 1,3 1,6 1,4 2,2 1,0 0,8 2,0
14,2 15,3 17,6 15,4 15,1 12,3 14,6 10,0 22,6 26,4 25,6 23,9 22,2 22,9 23,8 24,3 24,1 23,1 14,7 22,4 15,5 17,0 25,1 t3,0 16,5 14,5 25,1 8,9 6,6 22,9
10,8 11,1 12,7 tl,6 10,4 8,9 20,6
0,51 0,48 0,43 0,49 0,49 0,54 0,51 0,64 0,29 0,26 0,26 0,28 0,29 0,29 0,31 0,29 0,3O 0,29 0,50 0,30 0,49 0,40 0,29 0,54 0,45 0,48 0,27 0,66 0,75 o,3o
14,7 14,6 15,2 15,o 9,1 7,6 14,3
7,0 6,5 8,7
7,0 7,5 7,0 6,3 5,4 16,3 10,2 17,7 11,5 13,8 14,8 10,3 9,1 16,7 t2,0
7,0 9,3 6,1 7,1 8,3 5,4 7,4 6,6 11,6 3,7 3,1 9,8
1,5t 1,52 1,42 1,30 1,t2 1,23 1,11 1,24 t,75 1,91 1,79 1,62 1,89 2,08 1,80 1,83 1,93 1,73 1,13 1,70 1,32 1,49 1,85 1,22 t,46 1,46 1,72 1,19 1,10 1,79
3,0 2,2 3,0 2,6 3,1 3,2 3,0 2,3 3,8 2,4 4,2 3,2 4,2 3,4 2,9 2,2 4,7 3,8 2,8 3,0 2,5 2,6 1,8 2,6 2,8 2,7 2,8 2,3 3,0 2,7
0,76 0.90 1,t9 0,88 0,84 0,55 0,81 0,51 1,80 2,38 1,47 2,30 1,84 1,85 2,04 2,01 2,19 1,84 0,86 1,74 0,98 1,08 2,33 0,67 1,01 0,83 2,05 0,26 0,13 1,65
7,7 16,2 19,1 t6,0 17,6 17,1 17,3 t7,1 17,3 17,9 16,9 10,2 16,2 t0,9 12,3 17,9 10,0 12,2 10,4 16,3 7,1 5,1 15,8
1,51 1,53 1,72 t,55 1,43 1,32 1,45 1,19 2,48 2,79 2,57 2,65 2,64 2,64 2,32 2,48 2,5O 2,51 1,39 2,40 1,61 1,83 2,52 1,42 1,65 1,51 2,58 1,20 1,o3 2,34
(t) See the text.
Theoret. Appl. Genetics, Vol. 43, No. 2
s,.
H
~
bO~aba~.tOtOlOtO~4atO4a~a~o4at,a~,a~aba
-0,05 -0,20 --0,27 -0,tl -0,23 -0,14 -0,21 0,12 ~0,27 0,77 o,71 0,69 0,54 o,31 0,55
%87 -i
-o,ol -0,07 -0,21 -0,09 -0,07 -0,01 -0,07 0,00 -0,13 0,72 0,75 0,8o 0,59 o,41 0,60
2. L e a v e s per P l a n t
3. Pod L e n g t h
4. P o d W i d t h Width 5. Pod Thickness 6. Seeds per P o d
7. W e i g h t of one Seed
8. Seed L e n g t h
9. Seed W i d t h Thickness f0. Seed - Length Width 11. Seed - Thickness 12. Flowers per R a c e m e
13. R h a c h i s L e n g t h
14. Leaflets per L e a f
15. Leaflet L e n g t h Width 16. Leaflet Length17. Leaflet Area
t. P l a n t H e i g h t
o,52
0,06
0,59
O,37
0,45
0,06
0,82
--0,81
0,79
0,80
0,73
0,75
0,78
0,86
] 3
0,99
0,98
0,97
0,32
0,92
0,39
0,07
0,53
0,29
0,31
-0,17
0,97
--0,97
i4
~ 0 0 0 0 0 0 0 0 0 0 ~ 0 ~ 0 0 0 0 0 0 0 0 0 ~ 0 ~ 0 0 0
p p ~ p p p p p ~ p ' ~ P ~ P P P P P ~ P P ~ P ~ P ~
~.-*
,ft..
0
o,.-~
~ ~"~
~ ~., ~.
gg
ga-
s-
0,32
OA3
0,44
0A 5
0,24
-0,24
0,92
-0,88
0,91
0,89
0,88
0,34
i 5
0,30
-o,15
0,33
0,23
0,29
-0,02
0,38
-0,36
0,34
0,32
0,27
6
0,58 0,04 0,45
0,32
0,35
0,28 0,45
0,36
0,25
0,05
0,97 -0,14
O,96 -0,19
_ _
O,99
I
-O,99
O''
0,94
I 8
0
~ ~
gg
g
0,97 ** O,98
7
Table 3. C o r r e l a t i o n Coefficients
~~
] ~h:~
0,38
0,04
0,52
0,32
0,31
-0,20
0,98
-0,98
i 9
-
to
~.
11
-0,44
-o,01
-0,60
-0,39
-0,38
0,39
0,08
0,49
0,22
0,26
i
0,53
0,49
0,46
0,53
o,90
0,49
0,94
* 5%;
0,66
0,20
** 1%.
0,92
0,54
0,381 16
0,77 15
0,84 14
0,631 13
0 , 1 2 - o J91 12
-O,96
10
Level of Significance
171
gl
q
~a
e..t9
< 9
e..
J . I . Cubero : Evolutionary Trends in Vicia faba L.
62 P
t46 (C-IV) (Fig. 2). This group is heterogeneous, but it is better to have it to avoid excessive scattering. It develops positively the weight of the seeds and negatively a weak trend in seeds per pod and leaflet number per leaf (Table 5).
104
\o \
32 89
f
cm
9
\ ~
.os
--I
116/'"/-
~/
%~
Other major populations are: Sample number 104, -- It has developed in a positive way (compared with the mean) in seeds per pod, flowers per node and weight of one seed, and negatively in leaflets per leaf. It lies nearer to the C-I group than to the other central groups (Fig. 2). Sample number t 09. -- It lies nearest the C-I I I group (Fig. 2) but there are very long distances from the other groups: the longest distance obtained in this study was from t09 to paucijuga, t09 develops
IV ' ~ - - - - - ' 0 3
v"
/
109 Fig. 3. Distances from the central nucleus p
104
4.51.
p o s i t i v e l y all t h e c h a r a c t e r s e x c e p t (perhaps) t h e weight per seed, a n d shows t h e o p p o s i t e e v o l u t i o n a l t r e n d to paucijuga (Fig. 4). S a m p l e n u m b e r t16. - - This is a g r e a t d i s t a n c e from paucijuga a n d t 0 9 a n d lies n e a r b o t h C-I a n d C - I I I (Fig. 2), whose t r e n d s are r e p r e s e n t e d in t 1 6 : a g r e a t n u m b e r of seeds p e r pod, few flowers p e r n o d e (C-III), h e a v y seeds (C-I a n d C-III) a n d a large n u m b e r of leaflets per leaf (C-I) (Table 5).
Discussion Let us consider again the three isolated major populations in relation to both minor and paucijuga
Fig. 4. Relationships among extreme populations
Table 4. Quadratic Distances (D 2 Values)
25
24 1,97 1,74 t,58 11,05 2,t2 1,94 15,58 20,42 9,35 11,47 9,46 5,31 5,95 5,17 ] 8,19 16,51 4,61 3,00 ]5,46 2,10
125 2,34 1,64 11,43 L46 2,72 13,37 24,39 6,12 16,25 9,45 1o,96 7,61 4,14 4,24 23,09 8,81 3.14 5,26 1,14
1,O4
0,77
13,67 t,89 3,21 0,99 8,45 1o,45 14,03 3,34
8,18 1,95 3,84 1,t6 7,86 tl,54 19,61 2,73
26 27 28 32 94 103 t04 107 "169 11o 112 t13 114 115 116 122 t23 137 t38 138-1 t40 142 143 t44 t46 t71 172 203 '
26 1,35 5,20 3,83 0,85 12,49 16,52 7,25 14,07 4,45 7,00 2,51 2,83 4,97 tl,87 4,69 0,69 t,62 1,34 1,83 10,48 1,80 1,35 0,71 6,4t tl,27 19,65 3,36
27 7,63 4,27 1,32 17,14 21,21 8,37 19,89 7,32 8,84 3,68 3,20 4,35 14,69 5,56 2,48 2,59 0,19 0,91 9,94 0,12 2,15 1,29 7,99 7,38 14,11 2,10
i 28 12,42 4,66 15,63 21,97 20,39 28,67 9,75 2o,12 6,85 11,24 12,76 12,62 15,29 3,63 5,4t 7,73
11,42 21,96 7,18 5,99 7,54 17,47 16,98 32,05 14,23
[ 32 5,52 11,51 11,83
i 94 15,87 23,56
11,84
11,65
14,99 9,39 7,49 7,45 9,95 13,51 17,79 5,38 3,89 7,75 4,76 5,17 15,95 4,56 2,32 2,27 6,86 6,78 9,89 8,06
15,55 8,6O 9,o5 4,50 4,41 6,59 13,36 7,30 1,43 3,27 1,73 1,94 14,94 1,27 3,27 1,55 tt,59 t2,9t 21,07 4,36
i 1o3 15,86 18,50 24, 76 16,44 28,78 20,98 22,68 22,58 38,9o 24,83 8,35 17.80 15,46 18,26 21,22 17,27 9,69 9,91 14,08 21,02 37,15 23,97
104 18,48 " i 107 32,36 20,59 9,08 4,83 t9,64 11,52 13,8o 7,83 22,22 3,69 26,25 3,41 2o,51 23,3t 13,63 8,14 15,75 9,85 t5,82 6,32 20,64 6,81 24,50 6,49 21,60 1,54 22,77 10,28 10,62 7,79 16,89 7,43 8,04 2,36 t6,57 17,80 24,12 26,44 24,57 4,41
] 109 22,61 8,83 21,48 18,51 25,89 28,88 15,16 16,t3 21,90 20,59 14,71 32,45 21,36 19,84 14,16 21,56 40,46 41,13 18,23
] I10 ] -- 9_80-[ 1,86 3,93 5,69 9,63 4,97 5,92 t,93 6,54 8,59 6,70 8,84 3,88 6,73 2,68 14,29 24,54 6,84
Theoret. Appl. Genetics, Vol. 43, No. 2
J. I. Cubero: Evolutionary Trends in Vicia faba L. (Fig. 4). t04 is farther from 109 than from paucijuga or minor but, nevertheless, is a typical major. It is also interesting to consider t h a t both t04 and t09 have developed positively the number of flowers per raceme (Table 5). They are the only major populations to show this. This character (great number of flowers per raceme) is generally considered as typical of minor botanical varieties. If we accept a classification based on the shape of grain, it is necessary to concede that the rest of the characteristics are sparsely distributed in this species. The generalized systematic of Vicia/aba L. (Muratova, 193t) m a y be useful, but it is not natural. A natural system should include a more complete knowledge of the pathways followed b y the populations. How m a n y paths can there be ? If we consider n characteristics and three possibilities for each one (to augment, to diminish and to rest at the original value), there will be, obviously, 3 n trends. Actually, n u m b e r n is undetermined. In this study, out of t 7 characteristics we have maintained only five, but only three were naturally uncorrelated (the other two were slightly correlated with those three). An a t t e m p t to reduce the number of variates (Rao, 1952; Legras, 1963) has been made, but was unsuccessful, so a space of at least five dimensions is necessary to explain our results. In Cicer arietinum a reduction is possible: four variates are enough (Cubero, 1970). Perhaps some combinations of characteristics are not possible, but this is impossible to foresee. Thus, evolution in Vicia /aba seems to happen as an "explosion" in a space of n (n ~ 5) dimensions. The "explosion" is the rupture of the primitive equilibrium and the recombination of independent characters; theoretically it will have as m a n y such trends as the n u m b e r of possible combinations between them. We must now examine the elements of this assertion.
63
a. Primitive equilibrium The results show a scattering of populations from a central point wich m a y represent the ancestral form of the species. The group of populations which we have named "the central nucleus" is the nearest to t h a t hypothetical form; other populations have minimal distances from it. It is not a "passage point" from some original varieties to others (as if pauciiuga were the oldest population), but an authentic central point: 1 ~ I t maintains a m a x i m u m of potentiality or variability (it is formed b y m a n y different varieties in origin and use) ; 2 ~ if it were a "passage point" the populations which form it should be more scattered, but they lie together, forming a closed group. It would be difficult to explain how such a "passage point" is so particular. b. Recombination o/independent characteristics Original equilibrium refers to the maintenance of mean values for characteristics; these values m a y be obtained by adequate ratios of genes with positive and negative actions. Linkage between both sorts of genes maintains some populations near to the primitive values; they are the "primitive populations" which form the "Central Nucleus". Disturbance of this equilibrium between positive and negative genes changes the ratios between them so t h a t two ways for each character are possible -- to increase or to decrease the characters values. Mutations and new recombinations can enhance these trends and m a y also return the new values to the original ones, but if two or more characters are considered at the same time, it is very difficult to recover all the mean values simultaneously. When the equilibrium in the original population is broken, evolutionary changes are progressives and act as a "waterv a l v e " : they will never permit a decrease in the
Table 4. (continued) t13 114 115 116 122 t23 137 138 138-1 140 142 143 144 146 171 172 203
112 6,66I t13 7,05 2,43 ] 114 13,65 5,16 t,22 I 115 10,26 5,19 12,05 18,71 1,52 2,68 4,41 9,26 11,04 4,54 5,80 7,40 8,95 0,57 1,61 2,96 10,01 3,86 2,83 3,26 6,97 5,37 2,53 .3,97 1t%00t0,09 5,85 3,25 ]t0,40 4,64 4,41 5,40 i 9,79 3,08 5,40 6,93 8,49 5,03 4,68 6,27 10,03 5,82 6,07 7,t7 20,54 11,53 15,75 t5,95 18,52t8,93 23,38 26,90 6,3_8 4,t3 0,92 2,16
1116 7,48 15,04 8,44 16,24 17,59 28,1t 15,8t 13,64 17,28 18,69 24,47 28,59 15,38
Theoret. Appl. Genetics, Vol. 43, No. 2
1122 8,031 123 4,59 3,O6 I 137 6,3O 2,28 2,331 138 5,51 3,74 4,07 0,98i 13,3-1 12,85 12,64 7,73 7,86 9,361 t40 6,97 2,57 3,38 0,39 1,38 11,62 I 142_ 5,41 1,17 2 , 4 1 1,93 4,05 9,57 2,521 143 6,t8 O,86 3,68 t,16 t,54 t0,40 1,55 t,24 5,50 7,93 5,62 6,87 8,06 4,09 9,69 4,32 12,76 10,91 11,41 7,54 11,68 16,03 7,11 5,99 t3,51 21,58 21,24 15,61 17,10 27,41 14,15 14,75 4,19 6,55 3,36 2,01 1,07. 6,55 3,08 5,61
t44 61291 146 9,14 1--i~,18 [ 171 16,88 18,50 5,13 1172 3,99 6,73 12,88 17,67]
j. i. Cubero: Evolutionary Trends in Vicia faba L.
64
number of the old population, only a progression towards a new equilibrium. (Positive and negative genes are not necessary to explain the hypothetical equilibrium in the original population, but they are useful in developing these ideas.) Table 5. Evolutive tendencies of studied groups1 Seeds per pod B 28 A 1o3 C t04 c 1o9 C 116 P c III c iv
o - -
+ + + o + (-)
F l o w e r s
per raceme + + + + - -
-o
Weight of one grain
Leaflets perleaf
Leaflet length
-
+ +
o + o
- -
+ o + -+ +
- -
+ + -o (-)
+ o_
o o
I Tendencies with regard to Central Nucleus: +, --, 0: Respectively to increase, to diminish and to maintain the mean values. (--): Weak tendency.
c. Rupture o~ equilibrium in the original population Paragraphs a) and b) agree with our experimental results. But how is this equilibrium broken ? To answer this question, we must remember a biological characteristic of this species -- its reproductive system. F r o m Darwin (1857) onwards, the existence of partial allogamy, has been noted by m a n y authors, and also the depression of production in self-fertilization conditions (Fyfe, 1951; Fyfe and Bayley, t951; Drayner, t959; Rowlands, 1958, t960, 1961, 1964; Holden and Bond, 1960, Picard, 1960). Recently it has been suggested t h a t Vicia /aba has a homeostatic genetic system (Cubero, 1970); with only one self-fertilization, nearly all the correlations found in natural populations are weakeried or annulled. On the other hand, self-fertilization occurs naturally; the a u t o g a m y rates range from zero to about sixty per cent if we consider isolated plants (Cubero, 1969). Tt~e hybrid plants (originated by cross pollination) are self-fertile" the plants produced b y selfpollination show self-sterility (to very different degrees). The cycles of self- and cross-fertilization thus act as the "evolutive m o t o r " of this species. All the populations of Vicia /aba are in active evolution; only when a population becomes isolated and a u t o g a m y is fixed (for example, some strains of paucijuga, such as t72), does the motor stop, and also the possibilities for evolution. (The rate of a u t o g a m y is an important characteristic of populations, but it is more exact to speak of a "tendency towards allogamy or a u t o g a m y " , which can be measured in self-fertilization conditions; nevertheless, we h a v e n o t considered it in this study. I t is very much influenced b y environmental conditions.)
As the populations forming the Central Nucleus are only partially self-fertilized (i.e., not completely autogamous), we must conclude t h a t in Vicia ]aba autogamy is an acquired form of reproduction, weak a!logamy being the primitive form (i.e., allogamy without strong self-incompatibility). From the nucleus, new populations continuously reach their own individuality. Strain number 28 is a good example: it cannot be included among the " c e n t r a l " one, but it lies near; it m a y represent a new line of evolution beginning to emerge from the core of the species. Does the actual systematic of Vicia [aba agree with these results ? Two subspecies are recognized, paucijuga a n d / a b a , with three botanical varieties in the latter, followed by a multitude of forms, groups and so on. Paucijuga was separated from the rest of the species because of its geographical isolation and has developed some particularities: a strong tendency towards autogamy, a small number of leaflets per leaf, small sizes for seeds, few flowers per raceme, indehiscent pods, a large number of stems per plant, low h e i g h t . . , perhaps m a n y others. But, and this is important, no one of these characters is exclusive to paucijuga: seeds as small as those of this subspecies are found in some minor populations; the number of flowers and pod structure are like some major ones; selection towards a u t o g a m y is possible in isolated conditions; low height and low number of leaflets are found in natural populations. Recent studies have shown polygenic control for all these characters (Cubero, t969). Furthermore, paucijugacrosses very well, even exceptionally well, with other populations. It is also visited by pollinating insects. Paucijuga is, therefore, a "good subspecies" if it is characterized by a large number of characteristics instead of only a few, provided that isolation conditions remain. If agriculture, for example, carries populations o f / a b a ssp near those of paucijuga, the barrier between t h e m m a y be broken. The two subspecies m a y be maintained, but in Vicia/aba the subspecies concept is really a very weak one. Pauci/uga is really only the b o t t o m of an evolutionary trend, as there is no genetic isolation, nor intersterility, even weak. If the subspecies concept is an evolutional one, that is, a species in formation, as modern taxon o m y wants, paucijuga can n o t be maintained as this kind of taxon. I t might be better to Consider the species as a whole as only one major group, from which certain populations have become isolated only b y geographical barriers. The second and more important subspecies is/aba, with three botanical varieties distinguished according to width/length: major, equina and minor; this coeffic i e n t is negatively correlated with grain weight (Muratova, t93t). We have. seen t h a t there can be a greater distance between two ma/or populations
Theoret. Appl. Genetics, Vol. 43, No. 2
J. I. Cubero: Evolutionary Trends in Vicia faba L. t h a n b e t w e e n t h e s e t w o a n d paucijuga. F u r t h e r more, our " c e n t r a l n u c l e u s " is f o r m e d b y m o s t equina a n d m a n y t y p i c a l major p o p u l a t i o n s . I t is difficult, therefore, to m a i n t a i n t h e s e v a r i e t i e s as n a t u r a l entit i e s ; i t can be p r a c t i c a l , b u t n o t real. I t is old T a x o nomy, not Systematics. A c l a s s i f i c a t i o n b a s e d on e v o l u t i o n a r y t r e n d s is n o t p r a c t i c a l , b u t it is real. I t c a n n o t be w r i t t e n in t h e form of k e y s , b e c a u s e of t h e large n u m b e r of t r e n d s b u t it can o b v i o u s l y be an a i d to p l a n t b r e e d e r s . I t does n o t p e r m i t g r a p h i c a l r e p r e s e n t a t i o n (five d i m e n sions a t l e a s t for V. ]aba) n o r s i m p l e g e n e a l o g i c a l t r e e s (like t h e u s u a l designs in t e x t - b o o k s ) , b u t does N a t u r e r e a l l y a c t a c c o r d i n g to such a design ? T h e o n l y p r a c t i c a l p o i n t of such a s y s t e m is t h e d e s c r i p t i o n of t h e c e n t r a l nucleus of e v o l u t i o n as it m a y be useful to k n o w t h e p o t e n t i a l i t i e s k e p t in t h e species core. F o r Vicia [aba, in our e x p e r i m e n t a l c o n d i t i o n s , a n d n o t i n g t h a t n u m b e r s g i v e n are m e a n a n d n o t i n d i v i d u a l v a l u e s , this d e s c r i p t i o n is as follows : T h e C e n t r a l N u c l e u s of E v o l u t i o n of Vicia ]aba L. is f o r m e d b y p o p u l a t i o n s w i t h a seed w e i g h t r a n g i n g from 0 . 5 5 - - 2 . 0 0 g r a m s / s e e d , 2 - - 4 g r a i n s p e r p o d , coefficient w i d t h / l e n g t h of t h e seed 0,6 as m a x i m u m , l e n g t h of p o d from 5 . 5 - - 1 5 . 0 cm, 2 - - 5 flowers/ r a c e m e , 5 - - 6 leaflets p e r leaf, leaf r h a c h i s l e n g t h 6 . 5 - - 9 . 0 cm; v a r i a b l e h e i g h t a c c o r d i n g to c l i m a t i c conditions.
Received F e b r u a r y 18, 1972 Communicated by W. Seyffert and H. Stubbe
Theoret. Appl. Genetics, Vol. 43, No. 2
65
Literature
1. Cubero, J. I. : Herencia de quince caracteres cuantitativos en Vicia faba L. Tesina de Gracluaci6n en la Facultad de Ciencias de Madrid (t968). -- 2. Cubero, J. I. : Unpublished d a t a (t969). -- 3. Cubero, J. I.: Influencia de la homocigosis y heterocigosis en la fertilidad de Vicia faba L. Tesis de gradnaci6n par~ el Doctorado en la Escuela T6cnica Superior de Ingenieros Agr6nomos de Madrid (1970). -- 4. Darwin, Ch.: In: "Cross and selffertilization of plants", pag. 487 ss, ~2nd ed. London t 900. -- 5. Drayner, J. M. : Self and cross-fertility in field beans (Vicia faba L.). J. Agric. Sci. 41 , 371--378 (t959). -6. Fyfe, J. L., Bayley, W. T. J. : Plant breeding studies in leguminous forage crops. I. Natural cross-breeding in winter beans. J. Agric. Sci. 45, 141--147 (195t). -7. Holden, J. H., Bond, D. A.: Studies on the breeding system of the field bean, Vicia faba L. Heredity 15, 175--192 (1960). -- 8. Legras, J. : Pr6cis d'analyse num6a!que. Paris : Dunod t 963. -- 9. Muratova, V. : Common beans (Vicia faba L.). Suppl. 50, Bull. appl. Bot. Genet. P l a n t Breed. 285 pp. ( t 9 3 1 ) . - t0. Picard, J.: Donn6es sur l'am61ioration de la f6verole de printemps. Ann. Am61ior. Plantes lo, 121--153 (1960). -- I1. Rao, C. R.: Advanced statistical methods in biometric research. New York: John Wiley & Sons, Inc. t952. -- 12. Rowlands, D. G.: The nature of the breeding system in the field bean (Vicia faba L.) and its relationship to breeding for field. H e r e d i t y 12, t 13-- 126 (1958). -- 13. Rowlands, D. G. : F e r t i l i t y studies in the field bean (Vicia faba L.) I. Cross and self-fertility. H e r e d i t y 15, 161 -- t 73 (1960). - - t4. Rowlands, D. G. : F e r t i l i t y studies in field bean (Vicia faba L.). II. Inbreeding. H e r e d i t y 16, 497--508 (1961). -- 15. Rowlands, D . G . : F e r t i l i t y studies in the broad bean (Vicia faba L.). H e r e d i t y 19, 271--277 (1964).
Dr. Jos6 I. Cubero Instituto Nacional de Investigaciones Agrarias Centro Regional de Andalucia Finca " A l a m e d a del Obispo" A p a r t a d o Correos 240 C6rdoba (Spain)
Evolutionary Trends in Vicia faba L. J o s e I. CUBERO I n s t i t u t o N a c i o n a l de I n v e s t i g a c i o n e s A g r a r i a s , Centro R e g i o n a l de A n d a l u c i a , C 6 r d o b a (Spain)
Summary. 1. Distances have been calculated between t h i r t y natural populations of Viciafaba. 2. The results strongly suggest the existence of a Central Nucleus from which different trends of evolution have arisen. 3. The Central Nucleus represents the equilibrium between different genetic tendencies ; this equilibrium is postulated for the primitive populations of this species. 4. Disturbance of this balanced system can be produced by cycles of cross and self-fertilization; recombinations following these cycles are the origin of new genetic combinations so t h a t a new equilibrium is reached with a new cycle of disturbance. 5. The Muratova classification is discussed. I t is not possible to give a new classification based on these concepts, because of the great number of possible lines of evolution. The species must be considered as a whole, because there are no genetic barriers of isolation, only geographical ones and no sterility barriers have been produced between the subspecies. 6. A description of the Central Nucleus of Evolution is given.
Introduction I t is k n o w n t h a t b r o a d a n d field b e a n s h a v e b e e n c u l t i v a t e d since p r e h i s t o r i c times, from I n d i a to t h e W e s t e r n M e d i t e r r a n e a n countries. T h e y h a v e also been c u l t i v a t e d in C e n t r a l E u r o p e a n d t h e B r i t i s h Isles. E x c e p t for t h e I n d i a n ssp paucijuga, p o p u l a t i o n s h a v e n o t been i s o l a t e d u n d e r n a t u r a l c o n d i t i o n s or b y m a n . Man h a s t a k e n this species f r o m t h e original region to some countries, b u t p a r t i a l allog a m y d e p e n d s on t h e i n d i g e n o u s p o p u l a t i o n s : t h e new v a r i e t y is " a s s i m i l a t e d " m o r e or less q u i c k l y b y t h e n a t i v e ones. Thus, Vicia/aba is g o o d m a t e r i a l for s t u d y i n g t h e e v o l u t i o n of d i f f e r e n t i a t i o n where t h e r e is n e i t h e r g e o g r a p h i c n o r r e p r o d u c t i v e isolation. T h e t a x o n o m y of Vicia [aba has been s p e c i a l l y s t u d i e d b y M u r a t o v a (193 t), b u t n o b o d y has w o r k e d on its d e v e l o p m e n t as a species. R e c e n t l y , t h e exis t e n c e of a s t r o n g c e n t r a l nucleus c o m p o s e d of t h e major a n d equina p o p u l a t i o n s h a s b e e n d i s c u s s e d (Cubero, 1970), minor a n d pauci~uga being c o l a t e r a l b r a n c h e s d i r e c t e d in o p p o s i t e d i r e c t i o n s in r e l a t i o n to t h e p o s i t i o n of t h e nucleus. The p r e s e n t r e s e a r c h was u n d e r t a k e n to t r y to u n d e r s t a n d t h e d i f f e r e n t e v o l u t i o n a r y s t a t e s of this species, t h a t is, its evolut i o n a l h i s t o r y in its o r i g i n a l region.
Natural populations often consist of mixed botanical varieties. No selection was done, except t h a t atypical seeds of each sample were eliminated. At the time of observation homogeneity or heterogeneity was recorded. Seventeen characteristics have been studied (Table 2). Twelve were eliminated because they were strongly correlated with others (Table 3). For the five characteristics (numbers 6, 7, 12, 14 and 15) selected, quadratic distances were obtained (Table 4) (Rao, 1952). Results The equina p o p u l a t i o n s are v e r y closely g r o u p e d t o g e t h e r (Table 4), w i t h m i n i m a l d i s t a n c e s b e t w e e n them. F u r t h e r , this g r o u p is t h e closest to t h e o t h e r s ; its c e n t r a l p o s i t i o n is e v i d e n t . O n l y s t r a i n 28 is n o t i n c l u d e d in this g r o u p b u t , n e v e r t h e l e s s , it lies near. Minor n u m b e r 32 is q u i t e i n t e g r a t e d . T h e p o s i t i o n of
r
Material and M e t h o d s T h i r t y natural populations of Vicia faba from several geographical points have been used for this study. Of these, fourteen are classified as major, twelve as equina, two as minor and another two as pauc(iuga (using M U R A T O V A taxonomy). The origins of these populations are given in Table 1 ; the origins of the Spanish ones can be seen in Fig. I.
Fig. 1. Origins of Spanish populations
j. I. Cubero: Evolutionary Trends in Vicia faba L.
6O
Table 1. Groups and origin of populations studied (sample number refers to the Insti-
tuto Nacional de Investigaciones Agron6micas collection)
equina, is a t h i r d major g r o u p
c o m p o s e d of 1 t 2 a n d t 2 2 (C-III) ; t h e r e is a s h o r t e r dis115 major Spain (Sevilla) 24 equina Spain (CAdiz) t a n c e from t h e first to second 116 major Spain (Sevilla) 25 equina Italy g r o u p t h a n from t h e t h i r d 122 major Spain (Alicante) 26 equina Spain (Valencia) 123 equzna Spain (Valencia) 27 equina Spain (CAdiz) to e i t h e r t h e first or t h e 28 equina Morocco 137 major Spain (Badajoz) second. 32 minor Spain (Valencia) 138 equ~na I t a l y Equina a n d t h e two first t38.1 equma Italy 94 equina Morocco major g r o u p s (C-I a n d C-II) 140 major Spain (CAdiz) 103 minor U.S.A. t42 equ,na Spain (CAdiz) 104 major Spain (Guadalajara) f o r m a s t r o n g nucleus (the 143 equ~na Spain (CAdiz) 107 major Spain (Granada) t h i r d major g r o u p could be 144 equma Spain (CAdiz) 109 major Spain (Granada) i n t e g r a t e d ) from w h i c h t h e 146 major Spain (Zaragoza) 110 major Spain (Caceres) rest of t h e p o p u l a t i o n s b r a n c h 171 paucijuga I n d i a 112 major Spain (L6rida) 172 paucijuga India i 13 major Spain (L~rida) (Fig. 3).These p o p u l a t i o n s are : 203 major Greece I 14 major Spain (Sevilla) a. Paucifuga p o p u l a t i o n s (group P). T h e two specimens s t u d i e d lie t o g e t h e r , t h e m o s t e x t r e m e s a m p l e b o t h 28 a n d 32 will be discussed later. No g r a p h i c a l being t72. I t is e a s y to see t h a t its e v o l u t i o n a r y r e p r e s e n t a t i o n of t h e e q u i n a r e l a t i o n s h i p is useful. Major r e l a t i o n s h i p s are m o r e c o m p l i c a t e d (Fig. 2). p a t h - w a y d i m i n i s h e d t h e c h a r a c t e r i s t i c s v a l u e s in r e l a t i o n to t h e o v e r a l l m e a n (Table 2 a n d 4). Two g r o u p s lie n e a r equina: t h o s e f o r m e d b y l l 0 , b. Minor p o p u l a t i o n s (group A). - - T h e minor 1t3 a n d 137 (C-I) on one h a n d , a n d 1t4, 115 a n d s a m p l e t03 also shows e x t r e m e c h a r a c t e r i s t i c s : its 203 (C-II) on t h e other. I t can be seen (Table 4) t h a t d i s t a n c e from t h e c e n t r a l g r o u p s is large, b u t in in some r e s u l t s a few of these p o p u l a t i o n s are i n c l u d a different d i r e c t i o n from paucifuga (Fig. 4) ; increased a m o n g t h e equina group. Also near, b u t w i t h ed c h a r a c t e r i s t i c s are flowers p e r node, leaflets p e r its c o m p o n e n t s c l e a r l y d i f f e r e n t i a t e d from those of Table Plant
2.
Seed
Pod
Sample Number
Group (I)
Height (dm)
Number Length of leaves (cm)
Width Width Number Weight (cm) thickness of seeds (gr)
Length (mm)
Width (mm)
Thickness Width length thickness
24 25 26 27 28 32 94 t03 1o4 t07 1c9 11o 112 t13 114 115 116 122 123 t37 138 t38-1 14o t42 143 144 146 171 172 203
B 13 ]3 B B A ]3 C C C IV C CI C III CI C II CII C C III B CI ]3 B C IV B B ]3 CIV P P C II
4,6 5,6 5,4 4,4 7,6 4,8 5,3 7,6 4,1 5,2 5,9 5,4 4,0 4,4 5,3 4,8 4,3 4,0 6,0 5,O 5,2 4,9 3,5 4,7 4,5 5,1 5,0 3,0 2,5 4,1
16,4 16,8 15,6 14,6 20,4 t6,o 13,7 23,0 t3,1 11,9 18,8 13,4 12,1 12,9 13,8 14,7 t2,3 t0,4 19,8 12,5 t5,2 12,1 12,3
1,5 1,6 1,6 1,5 t,3 1,2 1,4 t,I 2,1 2,5 2,t 2,2 2,2 2,2 2,2 2,2 2,2 2,2 1,4 2,0 1,5 1,6 2,2 1,3 1,6 1,4 2,2 1,0 0,8 2,0
14,2 15,3 17,6 15,4 15,1 12,3 14,6 10,0 22,6 26,4 25,6 23,9 22,2 22,9 23,8 24,3 24,1 23,1 14,7 22,4 15,5 17,0 25,1 t3,0 16,5 14,5 25,1 8,9 6,6 22,9
10,8 11,1 12,7 tl,6 10,4 8,9 20,6
0,51 0,48 0,43 0,49 0,49 0,54 0,51 0,64 0,29 0,26 0,26 0,28 0,29 0,29 0,31 0,29 0,3O 0,29 0,50 0,30 0,49 0,40 0,29 0,54 0,45 0,48 0,27 0,66 0,75 o,3o
14,7 14,6 15,2 15,o 9,1 7,6 14,3
7,0 6,5 8,7
7,0 7,5 7,0 6,3 5,4 16,3 10,2 17,7 11,5 13,8 14,8 10,3 9,1 16,7 t2,0
7,0 9,3 6,1 7,1 8,3 5,4 7,4 6,6 11,6 3,7 3,1 9,8
1,5t 1,52 1,42 1,30 1,t2 1,23 1,11 1,24 t,75 1,91 1,79 1,62 1,89 2,08 1,80 1,83 1,93 1,73 1,13 1,70 1,32 1,49 1,85 1,22 t,46 1,46 1,72 1,19 1,10 1,79
3,0 2,2 3,0 2,6 3,1 3,2 3,0 2,3 3,8 2,4 4,2 3,2 4,2 3,4 2,9 2,2 4,7 3,8 2,8 3,0 2,5 2,6 1,8 2,6 2,8 2,7 2,8 2,3 3,0 2,7
0,76 0.90 1,t9 0,88 0,84 0,55 0,81 0,51 1,80 2,38 1,47 2,30 1,84 1,85 2,04 2,01 2,19 1,84 0,86 1,74 0,98 1,08 2,33 0,67 1,01 0,83 2,05 0,26 0,13 1,65
7,7 16,2 19,1 t6,0 17,6 17,1 17,3 t7,1 17,3 17,9 16,9 10,2 16,2 t0,9 12,3 17,9 10,0 12,2 10,4 16,3 7,1 5,1 15,8
1,51 1,53 1,72 t,55 1,43 1,32 1,45 1,19 2,48 2,79 2,57 2,65 2,64 2,64 2,32 2,48 2,5O 2,51 1,39 2,40 1,61 1,83 2,52 1,42 1,65 1,51 2,58 1,20 1,o3 2,34
(t) See the text.
Theoret. Appl. Genetics, Vol. 43, No. 2
s,.
H
~
bO~aba~.tOtOlOtO~4atO4a~a~o4at,a~,a~aba
-0,05 -0,20 --0,27 -0,tl -0,23 -0,14 -0,21 0,12 ~0,27 0,77 o,71 0,69 0,54 o,31 0,55
%87 -i
-o,ol -0,07 -0,21 -0,09 -0,07 -0,01 -0,07 0,00 -0,13 0,72 0,75 0,8o 0,59 o,41 0,60
2. L e a v e s per P l a n t
3. Pod L e n g t h
4. P o d W i d t h Width 5. Pod Thickness 6. Seeds per P o d
7. W e i g h t of one Seed
8. Seed L e n g t h
9. Seed W i d t h Thickness f0. Seed - Length Width 11. Seed - Thickness 12. Flowers per R a c e m e
13. R h a c h i s L e n g t h
14. Leaflets per L e a f
15. Leaflet L e n g t h Width 16. Leaflet Length17. Leaflet Area
t. P l a n t H e i g h t
o,52
0,06
0,59
O,37
0,45
0,06
0,82
--0,81
0,79
0,80
0,73
0,75
0,78
0,86
] 3
0,99
0,98
0,97
0,32
0,92
0,39
0,07
0,53
0,29
0,31
-0,17
0,97
--0,97
i4
~ 0 0 0 0 0 0 0 0 0 0 ~ 0 ~ 0 0 0 0 0 0 0 0 0 ~ 0 ~ 0 0 0
p p ~ p p p p p ~ p ' ~ P ~ P P P P P ~ P P ~ P ~ P ~
~.-*
,ft..
0
o,.-~
~ ~"~
~ ~., ~.
gg
ga-
s-
0,32
OA3
0,44
0A 5
0,24
-0,24
0,92
-0,88
0,91
0,89
0,88
0,34
i 5
0,30
-o,15
0,33
0,23
0,29
-0,02
0,38
-0,36
0,34
0,32
0,27
6
0,58 0,04 0,45
0,32
0,35
0,28 0,45
0,36
0,25
0,05
0,97 -0,14
O,96 -0,19
_ _
O,99
I
-O,99
O''
0,94
I 8
0
~ ~
gg
g
0,97 ** O,98
7
Table 3. C o r r e l a t i o n Coefficients
~~
] ~h:~
0,38
0,04
0,52
0,32
0,31
-0,20
0,98
-0,98
i 9
-
to
~.
11
-0,44
-o,01
-0,60
-0,39
-0,38
0,39
0,08
0,49
0,22
0,26
i
0,53
0,49
0,46
0,53
o,90
0,49
0,94
* 5%;
0,66
0,20
** 1%.
0,92
0,54
0,381 16
0,77 15
0,84 14
0,631 13
0 , 1 2 - o J91 12
-O,96
10
Level of Significance
171
gl
q
~a
e..t9
< 9
e..
J . I . Cubero : Evolutionary Trends in Vicia faba L.
62 P
t46 (C-IV) (Fig. 2). This group is heterogeneous, but it is better to have it to avoid excessive scattering. It develops positively the weight of the seeds and negatively a weak trend in seeds per pod and leaflet number per leaf (Table 5).
104
\o \
32 89
f
cm
9
\ ~
.os
--I
116/'"/-
~/
%~
Other major populations are: Sample number 104, -- It has developed in a positive way (compared with the mean) in seeds per pod, flowers per node and weight of one seed, and negatively in leaflets per leaf. It lies nearer to the C-I group than to the other central groups (Fig. 2). Sample number t 09. -- It lies nearest the C-I I I group (Fig. 2) but there are very long distances from the other groups: the longest distance obtained in this study was from t09 to paucijuga, t09 develops
IV ' ~ - - - - - ' 0 3
v"
/
109 Fig. 3. Distances from the central nucleus p
104
4.51.
p o s i t i v e l y all t h e c h a r a c t e r s e x c e p t (perhaps) t h e weight per seed, a n d shows t h e o p p o s i t e e v o l u t i o n a l t r e n d to paucijuga (Fig. 4). S a m p l e n u m b e r t16. - - This is a g r e a t d i s t a n c e from paucijuga a n d t 0 9 a n d lies n e a r b o t h C-I a n d C - I I I (Fig. 2), whose t r e n d s are r e p r e s e n t e d in t 1 6 : a g r e a t n u m b e r of seeds p e r pod, few flowers p e r n o d e (C-III), h e a v y seeds (C-I a n d C-III) a n d a large n u m b e r of leaflets per leaf (C-I) (Table 5).
Discussion Let us consider again the three isolated major populations in relation to both minor and paucijuga
Fig. 4. Relationships among extreme populations
Table 4. Quadratic Distances (D 2 Values)
25
24 1,97 1,74 t,58 11,05 2,t2 1,94 15,58 20,42 9,35 11,47 9,46 5,31 5,95 5,17 ] 8,19 16,51 4,61 3,00 ]5,46 2,10
125 2,34 1,64 11,43 L46 2,72 13,37 24,39 6,12 16,25 9,45 1o,96 7,61 4,14 4,24 23,09 8,81 3.14 5,26 1,14
1,O4
0,77
13,67 t,89 3,21 0,99 8,45 1o,45 14,03 3,34
8,18 1,95 3,84 1,t6 7,86 tl,54 19,61 2,73
26 27 28 32 94 103 t04 107 "169 11o 112 t13 114 115 116 122 t23 137 t38 138-1 t40 142 143 t44 t46 t71 172 203 '
26 1,35 5,20 3,83 0,85 12,49 16,52 7,25 14,07 4,45 7,00 2,51 2,83 4,97 tl,87 4,69 0,69 t,62 1,34 1,83 10,48 1,80 1,35 0,71 6,4t tl,27 19,65 3,36
27 7,63 4,27 1,32 17,14 21,21 8,37 19,89 7,32 8,84 3,68 3,20 4,35 14,69 5,56 2,48 2,59 0,19 0,91 9,94 0,12 2,15 1,29 7,99 7,38 14,11 2,10
i 28 12,42 4,66 15,63 21,97 20,39 28,67 9,75 2o,12 6,85 11,24 12,76 12,62 15,29 3,63 5,4t 7,73
11,42 21,96 7,18 5,99 7,54 17,47 16,98 32,05 14,23
[ 32 5,52 11,51 11,83
i 94 15,87 23,56
11,84
11,65
14,99 9,39 7,49 7,45 9,95 13,51 17,79 5,38 3,89 7,75 4,76 5,17 15,95 4,56 2,32 2,27 6,86 6,78 9,89 8,06
15,55 8,6O 9,o5 4,50 4,41 6,59 13,36 7,30 1,43 3,27 1,73 1,94 14,94 1,27 3,27 1,55 tt,59 t2,9t 21,07 4,36
i 1o3 15,86 18,50 24, 76 16,44 28,78 20,98 22,68 22,58 38,9o 24,83 8,35 17.80 15,46 18,26 21,22 17,27 9,69 9,91 14,08 21,02 37,15 23,97
104 18,48 " i 107 32,36 20,59 9,08 4,83 t9,64 11,52 13,8o 7,83 22,22 3,69 26,25 3,41 2o,51 23,3t 13,63 8,14 15,75 9,85 t5,82 6,32 20,64 6,81 24,50 6,49 21,60 1,54 22,77 10,28 10,62 7,79 16,89 7,43 8,04 2,36 t6,57 17,80 24,12 26,44 24,57 4,41
] 109 22,61 8,83 21,48 18,51 25,89 28,88 15,16 16,t3 21,90 20,59 14,71 32,45 21,36 19,84 14,16 21,56 40,46 41,13 18,23
] I10 ] -- 9_80-[ 1,86 3,93 5,69 9,63 4,97 5,92 t,93 6,54 8,59 6,70 8,84 3,88 6,73 2,68 14,29 24,54 6,84
Theoret. Appl. Genetics, Vol. 43, No. 2
J. I. Cubero: Evolutionary Trends in Vicia faba L. (Fig. 4). t04 is farther from 109 than from paucijuga or minor but, nevertheless, is a typical major. It is also interesting to consider t h a t both t04 and t09 have developed positively the number of flowers per raceme (Table 5). They are the only major populations to show this. This character (great number of flowers per raceme) is generally considered as typical of minor botanical varieties. If we accept a classification based on the shape of grain, it is necessary to concede that the rest of the characteristics are sparsely distributed in this species. The generalized systematic of Vicia/aba L. (Muratova, 193t) m a y be useful, but it is not natural. A natural system should include a more complete knowledge of the pathways followed b y the populations. How m a n y paths can there be ? If we consider n characteristics and three possibilities for each one (to augment, to diminish and to rest at the original value), there will be, obviously, 3 n trends. Actually, n u m b e r n is undetermined. In this study, out of t 7 characteristics we have maintained only five, but only three were naturally uncorrelated (the other two were slightly correlated with those three). An a t t e m p t to reduce the number of variates (Rao, 1952; Legras, 1963) has been made, but was unsuccessful, so a space of at least five dimensions is necessary to explain our results. In Cicer arietinum a reduction is possible: four variates are enough (Cubero, 1970). Perhaps some combinations of characteristics are not possible, but this is impossible to foresee. Thus, evolution in Vicia /aba seems to happen as an "explosion" in a space of n (n ~ 5) dimensions. The "explosion" is the rupture of the primitive equilibrium and the recombination of independent characters; theoretically it will have as m a n y such trends as the n u m b e r of possible combinations between them. We must now examine the elements of this assertion.
63
a. Primitive equilibrium The results show a scattering of populations from a central point wich m a y represent the ancestral form of the species. The group of populations which we have named "the central nucleus" is the nearest to t h a t hypothetical form; other populations have minimal distances from it. It is not a "passage point" from some original varieties to others (as if pauciiuga were the oldest population), but an authentic central point: 1 ~ I t maintains a m a x i m u m of potentiality or variability (it is formed b y m a n y different varieties in origin and use) ; 2 ~ if it were a "passage point" the populations which form it should be more scattered, but they lie together, forming a closed group. It would be difficult to explain how such a "passage point" is so particular. b. Recombination o/independent characteristics Original equilibrium refers to the maintenance of mean values for characteristics; these values m a y be obtained by adequate ratios of genes with positive and negative actions. Linkage between both sorts of genes maintains some populations near to the primitive values; they are the "primitive populations" which form the "Central Nucleus". Disturbance of this equilibrium between positive and negative genes changes the ratios between them so t h a t two ways for each character are possible -- to increase or to decrease the characters values. Mutations and new recombinations can enhance these trends and m a y also return the new values to the original ones, but if two or more characters are considered at the same time, it is very difficult to recover all the mean values simultaneously. When the equilibrium in the original population is broken, evolutionary changes are progressives and act as a "waterv a l v e " : they will never permit a decrease in the
Table 4. (continued) t13 114 115 116 122 t23 137 138 138-1 140 142 143 144 146 171 172 203
112 6,66I t13 7,05 2,43 ] 114 13,65 5,16 t,22 I 115 10,26 5,19 12,05 18,71 1,52 2,68 4,41 9,26 11,04 4,54 5,80 7,40 8,95 0,57 1,61 2,96 10,01 3,86 2,83 3,26 6,97 5,37 2,53 .3,97 1t%00t0,09 5,85 3,25 ]t0,40 4,64 4,41 5,40 i 9,79 3,08 5,40 6,93 8,49 5,03 4,68 6,27 10,03 5,82 6,07 7,t7 20,54 11,53 15,75 t5,95 18,52t8,93 23,38 26,90 6,3_8 4,t3 0,92 2,16
1116 7,48 15,04 8,44 16,24 17,59 28,1t 15,8t 13,64 17,28 18,69 24,47 28,59 15,38
Theoret. Appl. Genetics, Vol. 43, No. 2
1122 8,031 123 4,59 3,O6 I 137 6,3O 2,28 2,331 138 5,51 3,74 4,07 0,98i 13,3-1 12,85 12,64 7,73 7,86 9,361 t40 6,97 2,57 3,38 0,39 1,38 11,62 I 142_ 5,41 1,17 2 , 4 1 1,93 4,05 9,57 2,521 143 6,t8 O,86 3,68 t,16 t,54 t0,40 1,55 t,24 5,50 7,93 5,62 6,87 8,06 4,09 9,69 4,32 12,76 10,91 11,41 7,54 11,68 16,03 7,11 5,99 t3,51 21,58 21,24 15,61 17,10 27,41 14,15 14,75 4,19 6,55 3,36 2,01 1,07. 6,55 3,08 5,61
t44 61291 146 9,14 1--i~,18 [ 171 16,88 18,50 5,13 1172 3,99 6,73 12,88 17,67]
j. i. Cubero: Evolutionary Trends in Vicia faba L.
64
number of the old population, only a progression towards a new equilibrium. (Positive and negative genes are not necessary to explain the hypothetical equilibrium in the original population, but they are useful in developing these ideas.) Table 5. Evolutive tendencies of studied groups1 Seeds per pod B 28 A 1o3 C t04 c 1o9 C 116 P c III c iv
o - -
+ + + o + (-)
F l o w e r s
per raceme + + + + - -
-o
Weight of one grain
Leaflets perleaf
Leaflet length
-
+ +
o + o
- -
+ o + -+ +
- -
+ + -o (-)
+ o_
o o
I Tendencies with regard to Central Nucleus: +, --, 0: Respectively to increase, to diminish and to maintain the mean values. (--): Weak tendency.
c. Rupture o~ equilibrium in the original population Paragraphs a) and b) agree with our experimental results. But how is this equilibrium broken ? To answer this question, we must remember a biological characteristic of this species -- its reproductive system. F r o m Darwin (1857) onwards, the existence of partial allogamy, has been noted by m a n y authors, and also the depression of production in self-fertilization conditions (Fyfe, 1951; Fyfe and Bayley, t951; Drayner, t959; Rowlands, 1958, t960, 1961, 1964; Holden and Bond, 1960, Picard, 1960). Recently it has been suggested t h a t Vicia /aba has a homeostatic genetic system (Cubero, 1970); with only one self-fertilization, nearly all the correlations found in natural populations are weakeried or annulled. On the other hand, self-fertilization occurs naturally; the a u t o g a m y rates range from zero to about sixty per cent if we consider isolated plants (Cubero, 1969). Tt~e hybrid plants (originated by cross pollination) are self-fertile" the plants produced b y selfpollination show self-sterility (to very different degrees). The cycles of self- and cross-fertilization thus act as the "evolutive m o t o r " of this species. All the populations of Vicia /aba are in active evolution; only when a population becomes isolated and a u t o g a m y is fixed (for example, some strains of paucijuga, such as t72), does the motor stop, and also the possibilities for evolution. (The rate of a u t o g a m y is an important characteristic of populations, but it is more exact to speak of a "tendency towards allogamy or a u t o g a m y " , which can be measured in self-fertilization conditions; nevertheless, we h a v e n o t considered it in this study. I t is very much influenced b y environmental conditions.)
As the populations forming the Central Nucleus are only partially self-fertilized (i.e., not completely autogamous), we must conclude t h a t in Vicia ]aba autogamy is an acquired form of reproduction, weak a!logamy being the primitive form (i.e., allogamy without strong self-incompatibility). From the nucleus, new populations continuously reach their own individuality. Strain number 28 is a good example: it cannot be included among the " c e n t r a l " one, but it lies near; it m a y represent a new line of evolution beginning to emerge from the core of the species. Does the actual systematic of Vicia [aba agree with these results ? Two subspecies are recognized, paucijuga a n d / a b a , with three botanical varieties in the latter, followed by a multitude of forms, groups and so on. Paucijuga was separated from the rest of the species because of its geographical isolation and has developed some particularities: a strong tendency towards autogamy, a small number of leaflets per leaf, small sizes for seeds, few flowers per raceme, indehiscent pods, a large number of stems per plant, low h e i g h t . . , perhaps m a n y others. But, and this is important, no one of these characters is exclusive to paucijuga: seeds as small as those of this subspecies are found in some minor populations; the number of flowers and pod structure are like some major ones; selection towards a u t o g a m y is possible in isolated conditions; low height and low number of leaflets are found in natural populations. Recent studies have shown polygenic control for all these characters (Cubero, t969). Furthermore, paucijugacrosses very well, even exceptionally well, with other populations. It is also visited by pollinating insects. Paucijuga is, therefore, a "good subspecies" if it is characterized by a large number of characteristics instead of only a few, provided that isolation conditions remain. If agriculture, for example, carries populations o f / a b a ssp near those of paucijuga, the barrier between t h e m m a y be broken. The two subspecies m a y be maintained, but in Vicia/aba the subspecies concept is really a very weak one. Pauci/uga is really only the b o t t o m of an evolutionary trend, as there is no genetic isolation, nor intersterility, even weak. If the subspecies concept is an evolutional one, that is, a species in formation, as modern taxon o m y wants, paucijuga can n o t be maintained as this kind of taxon. I t might be better to Consider the species as a whole as only one major group, from which certain populations have become isolated only b y geographical barriers. The second and more important subspecies is/aba, with three botanical varieties distinguished according to width/length: major, equina and minor; this coeffic i e n t is negatively correlated with grain weight (Muratova, t93t). We have. seen t h a t there can be a greater distance between two ma/or populations
Theoret. Appl. Genetics, Vol. 43, No. 2
J. I. Cubero: Evolutionary Trends in Vicia faba L. t h a n b e t w e e n t h e s e t w o a n d paucijuga. F u r t h e r more, our " c e n t r a l n u c l e u s " is f o r m e d b y m o s t equina a n d m a n y t y p i c a l major p o p u l a t i o n s . I t is difficult, therefore, to m a i n t a i n t h e s e v a r i e t i e s as n a t u r a l entit i e s ; i t can be p r a c t i c a l , b u t n o t real. I t is old T a x o nomy, not Systematics. A c l a s s i f i c a t i o n b a s e d on e v o l u t i o n a r y t r e n d s is n o t p r a c t i c a l , b u t it is real. I t c a n n o t be w r i t t e n in t h e form of k e y s , b e c a u s e of t h e large n u m b e r of t r e n d s b u t it can o b v i o u s l y be an a i d to p l a n t b r e e d e r s . I t does n o t p e r m i t g r a p h i c a l r e p r e s e n t a t i o n (five d i m e n sions a t l e a s t for V. ]aba) n o r s i m p l e g e n e a l o g i c a l t r e e s (like t h e u s u a l designs in t e x t - b o o k s ) , b u t does N a t u r e r e a l l y a c t a c c o r d i n g to such a design ? T h e o n l y p r a c t i c a l p o i n t of such a s y s t e m is t h e d e s c r i p t i o n of t h e c e n t r a l nucleus of e v o l u t i o n as it m a y be useful to k n o w t h e p o t e n t i a l i t i e s k e p t in t h e species core. F o r Vicia [aba, in our e x p e r i m e n t a l c o n d i t i o n s , a n d n o t i n g t h a t n u m b e r s g i v e n are m e a n a n d n o t i n d i v i d u a l v a l u e s , this d e s c r i p t i o n is as follows : T h e C e n t r a l N u c l e u s of E v o l u t i o n of Vicia ]aba L. is f o r m e d b y p o p u l a t i o n s w i t h a seed w e i g h t r a n g i n g from 0 . 5 5 - - 2 . 0 0 g r a m s / s e e d , 2 - - 4 g r a i n s p e r p o d , coefficient w i d t h / l e n g t h of t h e seed 0,6 as m a x i m u m , l e n g t h of p o d from 5 . 5 - - 1 5 . 0 cm, 2 - - 5 flowers/ r a c e m e , 5 - - 6 leaflets p e r leaf, leaf r h a c h i s l e n g t h 6 . 5 - - 9 . 0 cm; v a r i a b l e h e i g h t a c c o r d i n g to c l i m a t i c conditions.
Received F e b r u a r y 18, 1972 Communicated by W. Seyffert and H. Stubbe
Theoret. Appl. Genetics, Vol. 43, No. 2
65
Literature
1. Cubero, J. I. : Herencia de quince caracteres cuantitativos en Vicia faba L. Tesina de Gracluaci6n en la Facultad de Ciencias de Madrid (t968). -- 2. Cubero, J. I. : Unpublished d a t a (t969). -- 3. Cubero, J. I.: Influencia de la homocigosis y heterocigosis en la fertilidad de Vicia faba L. Tesis de gradnaci6n par~ el Doctorado en la Escuela T6cnica Superior de Ingenieros Agr6nomos de Madrid (1970). -- 4. Darwin, Ch.: In: "Cross and selffertilization of plants", pag. 487 ss, ~2nd ed. London t 900. -- 5. Drayner, J. M. : Self and cross-fertility in field beans (Vicia faba L.). J. Agric. Sci. 41 , 371--378 (t959). -6. Fyfe, J. L., Bayley, W. T. J. : Plant breeding studies in leguminous forage crops. I. Natural cross-breeding in winter beans. J. Agric. Sci. 45, 141--147 (195t). -7. Holden, J. H., Bond, D. A.: Studies on the breeding system of the field bean, Vicia faba L. Heredity 15, 175--192 (1960). -- 8. Legras, J. : Pr6cis d'analyse num6a!que. Paris : Dunod t 963. -- 9. Muratova, V. : Common beans (Vicia faba L.). Suppl. 50, Bull. appl. Bot. Genet. P l a n t Breed. 285 pp. ( t 9 3 1 ) . - t0. Picard, J.: Donn6es sur l'am61ioration de la f6verole de printemps. Ann. Am61ior. Plantes lo, 121--153 (1960). -- I1. Rao, C. R.: Advanced statistical methods in biometric research. New York: John Wiley & Sons, Inc. t952. -- 12. Rowlands, D. G.: The nature of the breeding system in the field bean (Vicia faba L.) and its relationship to breeding for field. H e r e d i t y 12, t 13-- 126 (1958). -- 13. Rowlands, D. G. : F e r t i l i t y studies in the field bean (Vicia faba L.) I. Cross and self-fertility. H e r e d i t y 15, 161 -- t 73 (1960). - - t4. Rowlands, D. G. : F e r t i l i t y studies in field bean (Vicia faba L.). II. Inbreeding. H e r e d i t y 16, 497--508 (1961). -- 15. Rowlands, D . G . : F e r t i l i t y studies in the broad bean (Vicia faba L.). H e r e d i t y 19, 271--277 (1964).
Dr. Jos6 I. Cubero Instituto Nacional de Investigaciones Agrarias Centro Regional de Andalucia Finca " A l a m e d a del Obispo" A p a r t a d o Correos 240 C6rdoba (Spain)
