Ja. Reinartz et Dh. Les, BOTTLENECK-INDUCED DISSOLUTION OF SELF-INCOMPATIBILITY AND BREEDING SYSTEM CONSEQUENCES IN ASTER FURCATUS (ASTERACEAE), American journal of botany, 81(4), 1994, pp. 446-455
Aster furcatus is a rare species with extremely limited genetic variat
ion at isozyme loci. We utilized crossing experiments and seed set dat
a obtained from natural populations to verify that there is also littl
e allelic variation at the self-incompatibility (S) locus. Seed set in
several populations was limited by a low number of S-alleles. Associa
ted with a low number of S-alleles in populations was the dissolution
of the incompatibility system, manifest by individual variation in sel
f-compatibility, and by complex dominance relationships among S-allele
s. Plant self-compatibility was correlated with mean number of ovules
per inflorescence. Thus, self-compatibility appeared to be under parti
al environmental influence. Computer simulations revealed that the sha
pes of seed set distribution curves of modeled self-incompatible plant
populations depend on the number of incompatibility alleles in the po
pulations. By varying the number of S-alleles in modeled populations,
we generated seed set distribution curves similar to those of natural
populations. Genetic bottlenecks reduce the number of S-alleles and th
e proportion of compatible matings in populations of multiallelic self
-incompatible species. Self-compatible genotypes are at a selective ad
vantage in populations that lack a sufficient number of S-alleles to p
roduce compatible crosses. Aster furcatus appears to be evolving self-
compatibility as a result of bottleneck-induced losses of S-alleles.