Effects of selfing on the evolution of sexual reproduction

Abstract

Selfing has multiple effects on the evolution of sex through both direct and indirect selection. Using population genetic models, this study investigates the effects of sprorophytic and gametophytic selfing on the evolution of a modifier of sex. Results show that although indirect selection due to segregation and selection against genome-wide deleterious mutations can favor sexual reproduction under gametophytic selfing, it greatly inhibits the evolution of both asexual and sexual reproduction under spropophytic selfing. Both sporophytic and gametophytic selfing also reduce the fitness of sexually reproduced offspring relative to asexually reproduced offspring, which can cause direct selection against sexual reproduction. Selfing also weakens selection against sex caused by the transmission disadvantage and mate limitation. However, under sporophytic selfing, indirect selection due to segregation is much stronger than other types of selection, but is comparable to other types of selection under gametophytic selection. The results offer novel insights on the evolution of diverse reproductive modes in plant populations, and suggest that the evolution of the rate of sexual reproduction may precede the evolution of selfing in angiosperms and gymnosperms.