Mating system

A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mate, under which circumstances; recognised systems include monogamy, polygamy (which includes polygyny, polyandry, and polygynandry), and promiscuity, all of which lead to different mate choice outcomes and thus these systems affect how sexual selection works in the species which practice them. In plants, the term refers to the degree and circumstances of outcrossing. In human sociobiology, the terms have been extended to encompass the formation of relationships such as marriage.

The primary mating systems in plants are outcrossing (cross-fertilisation), autogamy (self-fertilisation) and apomixis (asexual reproduction without fertilization, but only when arising by modification of sexual function). Mixed mating systems, in which plants use two or even all three mating systems, are not uncommon.

A number of models have been used to describe the parameters of plant mating systems. The basic model is the mixed mating model, which is based on the assumption that every fertilisation is either self-fertilisation or completely random cross-fertilisation. More complex models relax this assumption; for example, the effective selfing model recognises that mating may be more common between pairs of closely related plants than between pairs of distantly related plants.

The following are some of the mating systems generally recognized in animals:

These mating relationships may or may not be associated with social relationships, in which the sexual partners stay together to become parenting partners. As the alternative term "pair bonding" implies, this is usual in monogamy. In many polyandrous systems, the males and the female stay together to rear the young. In polygynous systems where the number of females paired with each male is low and the male will often stay with one female to help rear the young, while the other females rear their young on their own. In polygynandry, each of the males may assist one female; if all adults help rear all the young, the system is more usually called "communal breeding". In highly polygynous systems, and in promiscuous systems, paternal care of young is rare, or there may be no parental care at all.

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