The distribution of sexual function in the flowering plant: from monoecy to dioecy.

In flowering plants, male and female functions are usually closely associated in the same flowers, as predicted by resource allocation theory. However, the benefits of outbreeding can lead to unisexual flowers and the physiological control of their distribution across the plant (monoecy). Monoecy is thought to be a major route to dioecy (separation of sexual function of different individuals). The developmental and functional problems associated with unisexual flowers may thus be solved at the level of the evolution of monoecy. Consequently, the evolution of dioecy from monoecy requires mutations in only a single gene. Here various scenarios (conceptual models) are presented for the evolution of monoecy and dioecy, including scenarios consistent with known cases of single-gene control of dioecy, such as in