Editing Disassortative mating (section)

{{short description|Preferential mating pattern between individuals with dissimilar phenotypes (e.g., size, colour)}}
'''Disassortative mating''' (also known as '''negative assortative mating''' or '''heterogamy''') is a mating pattern in which individuals with dissimilar [[phenotypes]] mate with one another more frequently than would be expected under [[random mating]]. Disassortative mating reduces the mean genetic similarities within the population and produces a greater number of [[heterozygotes]]. The pattern is character specific, but does not affect allele frequencies.<ref>{{cite journal |last1=Lewontin |first1=Richard |last2=Kirk |first2=Dudley |last3=Crow |first3=James |title=Selective mating, assortative mating, and inbreeding: Definitions and implications |journal=Eugenics Quarterly |date=1963|volume=15 |issue=2 |pages=141–143 |doi=10.1080/19485565.1968.9987764 |pmid=5702329 }}</ref> This nonrandom mating pattern will result in deviation from the [[Hardy-Weinberg principle]] (which states that genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences, such as "mate choice" in this case).

Disassortative mating is different from [[outbreeding]], which refers to mating patterns in relation to [[genotypes]] rather than phenotypes.

Due to homotypic preference (bias toward the same type), [[assortative mating]] occurs more frequently than disassortative mating.<ref>{{cite journal |last1=Thiessen |last2=Gregg |title=Human assortative mating and genetic equilibrium: An evolutionary perspective |journal=Ethology and Sociobiology |year=1980 |volume=1 |issue=2 |pages=111–140 |url=|doi=10.1016/0162-3095(80)90003-5}}</ref><ref>{{cite tech report |last1=Wallace |first1=B |title=The role of heterozygosity in drosophila populations |date=January 1958 |osti=4289507}}</ref> This is because homotypic preferences increase relatedness between mates and between parents and offspring that would promote cooperation and increases inclusive fitness. With disassortative mating, heterotypic preference (bias towards different types) in many cases has been shown to increase overall fitness.<ref>{{cite journal |last1=Burley |first1=Nancy |title=The meaning of assortative mating |journal=Ethology and Sociobiology |year=1983 |volume=4 |issue=4 |pages=191–203 |doi=10.1016/0162-3095(83)90009-2}}</ref> When this preference is favored, it allows a population to generate and/or maintain polymorphism (genetic variation within a population).

The fitness advantage aspect of disassortative mating seems straightforward, but the evolution of selective forces involved in disassortative mating are still largely unknown in natural populations.