The Evolutionary Significance of Pseudo-Self-Fertility

The shift from self-sterility to predominant self-fertility has occurred in a multitude of flowering plant lineages. This shift has been attributed to the partial replacement of self-incompatibility alleles at the S locus by alleles conferring self-fertility. I propose that pseudo-self-fertility (i.e., self-fertility dictated by polygenic modifiers of S gene action) may have been pivotal in the evolution of self-fertility. Pseudo-self-fertility is known in numerous species, whereas self-fertility governed by S alleles is known only in a few species, and then only in those with a history of selfing. Pseudo-self-fertility is readily increased by selection, although its expression also is influenced by the environment Pseudo-self-fertility maximizes the dual advantages of outcrossing and selfing.