Dioecious

Dioecy (Greek: διοικία "two households"; adjective form: dioecious) is a characteristic of a species, meaning that it has distinct male and female individual organisms or colonies, meaning that a colony contains only either male or female individuals. Dioecious reproduction is biparental reproduction. Dioecy is one method that excludes self-fertilization and promotes allogamy (outcrossing), and thus tends to reduce the expression of recessive deleterious mutations present in a population.Flowering plants have several other methods of excluding self-fertilization, called Self-incompatibility.

In zoology, dioecious species may be opposed to hermaphroditic species, meaning that an individual is of only one sex, in which case the synonym gonochory is more often used. Dioecy may also describe colonies, such as the colonies of Siphonophorae (Portuguese man-of-war), which may be either dioecious within a species or monoecious. Dioecious colonies contain members of only one sex, whereas monoecious colonies contain members of both sexes.

Most animal species are dioecious (gonochoric).

Dioecy occurs in a wide variety of plant families. However it is more common in woody plants and heterotrophic species.

There are several alternatives to dioecy for sexual reproductive structure organization in plants including bisexual flowers, monoecy, gynomonoecy, andromonecy. These are described at Plant reproductive morphology.

Land plants have alternation of generations, for which the sporophyte generation produces spores rather than gametes. Strictly speaking, the sporophytes of land plants do not have either male or female reproductive organs. The gametophytes of flowering plants are of a single sex; the male gametophytes are contained within the pollen, and the female gametophytes are contained within ovules. The sporophyte generation is called dioecious when each sporophyte has only one kind of spore-producing organ whose spores ultimately give rise to either all male gametes (sperm) or all female gametes (eggs). Slightly different terms, "dioicous" and "monoicous", may be used for the gametophyte generation, although "dioecious" and "monoecious" are also used.

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