Dioecy

Dioecy (from Ancient Greek διοικία (dioikía) 'two households'; adj. dioecious) is a characteristic of species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is biparental reproduction. Dioecy has costs, since only the females directly produce offspring. It is a way to prevent self-fertilization and promote allogamy (outcrossing), and thus tends to reduce the expression of recessive deleterious mutations. Plants have several other ways to prevent self-fertilization including, for example, dichogamy, herkogamy, and self-incompatibility.