Effects of Early‐ and Late‐Acting Mutations on the Coevolution of Selfing Rate, Inbreeding Depression, and Overproduction of Ovules

ABSTRACT

I developed a simulation model to examine whether deleterious mutations can be maintained by a two‐stage effect (the interaction of early‐ and late‐acting mutations) when the selfing rate, inbreeding depression, and the degree of overproduction evolve. In this model, plants allocate their resources to the production of ovules, pollen, seeds, and the structures of pollen transport, and these allocation ratios evolve. Plants have early‐ and late‐acting loci, and deleterious mutations occur in these loci. I found that, for the same realized values of selfing rate, the number of early‐acting mutations maintained per locus was greater if mutations occurred in both early‐ and late‐acting loci than if mutations occurred in early‐acting loci but not in late‐acting loci. The number of late‐acting mutations maintained per locus also tended to be greater if mutations occurred in both types of loci than if mutations occurred only at late‐acting loci, although this difference was less clear. Thus, the two‐stage effect can maintain deleterious mutations, particularly early‐acting ones, even if all the traits mentioned evolve. In addition, I found that both the saturation of pollen capture and moderate variance in the number of pollination opportunities are important factors leading to the evolution of mixed mating.