Asynchronic flowering in self-incompatible annuals

Abstract

Presentation of pollen and stigmas at different times by individuals of a population is likely to exert a profound influence on its genetic structure. We have analysed the changes undergone in (1) asynchrony and (2) single locus heterozygosity, under the irruption of self-incompatible variants in a population of random-mating hermaphroditic annuals. Equations relating genotypic frequencies with time-dependent gamete availability parameters were obtained. These were run in a numerical example over 20 generations, starting from a mixed population showing different degrees of asynchrony depending on the mode of inheritance of this trait. Five cases were analysed, differing in the degree of dominance. Self-incompatibility starts to be expressed in the first generation. Dominance for early- and late-flowering times was negatively associated with asynchrony, due to the existence of self-incompatible variants. A higher degree of potential genetic variability was observed in the locus controlling pollen availability than in the one controlling ovules in advanced generations under this reproductive system.