A Self-Incompatibility System Explains High Male Frequencies in an Androdioecious Plant

Abstract

The Making of the Males Most plants have a hermaphroditic mating system with flowers with both male and female function. However, in some cases, species are invaded by a sex-specific sterility factor. When female sterility factors invade a population, it results in a mating system called androdioecy. Theoretically, these female sterile (male) individuals should occur at low frequencies because of their reduced reproductive capacity. However, some species in the olive family have a greater than expected frequency of males. Saumitou-Laprade et al. (p. 1648 ) show that, for one species, males were able to reach high frequencies because of the retention of a self-incompatibility factor within hermaphroditic individuals. In this case, hermaphroditic individuals can only mate with individuals outside of their incompatibility type, reducing their available mating partners, whereas males are able to mate with all hermaphrodites. This explains how, contrary to theory, high frequencies of males can exist within populations.