Polymorphism maintenance in populations with mixed random mating and apomixis subjected to stabilizing and cyclical selection

We analysed a diploid population model with a mixed breeding system that in cludes panmixia and apomixis. Each individual produces a part (ss) of its p rogeny by random mating, the remainder (1-ss) being a result of precise cop ying (vegetative reproduction or apomixis) of the parental genotype. Both c onstant and periodically varying selection regimes were considered. In the main model, the selected trait was controlled by two diallelic additive or semidominant loci, A/a and B/b, whereas the parameter of breeding system (s s) was genotype-independent. A numerical iteration of the evolutionary equa tions were used to evaluate the proportion (V) of population trajectories c onverging to internal (polymorphic) fixed points. The results were the foll owing. (a) A complex pattern of dependence of polymorphism stability on int eraction among the breeding system, recombination rate, and the genetic arc hitecture of the selected trait emerged. (b) The recombination provided som e advantage to sex at intermediate period lengths and strong-to-moderate se lection intensities. (c) The complex limiting behavior (CLB) was quite comp atible with sexual reproduction, at least within the framework of pure gene tic (not including variations in population density) models of multilocus v arying selection. (C) 2001 Academic Press.