Panmixia

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Panmixia

 

the free crossbreeding of individuals within a population or some other intraspecific group.

Complete panmixia exists only when each individual has the possibility to mate with any individual of the opposite sex. However, in nature pairs do not form for crossbreeding by chance. The choice of partners is conditioned chiefly by similarity in behavior and physiology; the partner chosen also inhabits the same part of the area of distribution. In the latter case, divergences from complete panmixia may be the result of crossbreeding between close relatives (inbreeding). Therefore, when one refers to panmixia in natural groups of individuals, and first and foremost in populations, what is usually meant is the extent to which panmixia occurs: it must be more common within a given group than among individuals of neighboring groups.

The extent to which panmixia occurs varies among species and depends on differences in the manner of reproduction. Some species form long-term, sometimes lifelong, pairs; other species form pairs only for the reproductive season. Some species, such as many galliforms, do not form lasting pairs; in other species, for example, many insects and arachnids, the females are fertilized only once in their lives. Species in which fertilization takes place externally, such as fishes and amphibians, do not form pairs. Here, a cluster of eggs from a single female may be fertilized by spermatozoa from different males. To whatever extent it occurs, panmixia safeguards the genetic and evolutionary unity of intraspecific groupings and of the species as a whole. The term “panmixia” was introduced in 1885 by A. Weismann.

REFERENCE

Weismann, A. Die Continuität des Keimplasmas als Grundlage einer Theorie der Vererbung, 2nd ed. Jena, 1892.

A. V. IABLOKOV

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And lastly, statistical support was strongest for a panmictic model of gene flow.
It is likely that tomcod from throughout the Hudson River constitute a single panmictic population, and thus, the allelic variants underlying the resistant phenotypes are likely to be homogeneously distributed throughout the Hudson River population.
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virginica inhabiting the Gulf coast do not belong to a single panmictic unit.
Smallness of the panmictic unit of Triatoma infestans (Hemiptera: Reduviidae).
1995, 1999) showed that harbor porpoise in both the eastern North Pacific and North Atlantic were not panmictic and that movement was sufficiently restricted resulting in genetic differences.
The basic idea is that in a randomly mating or panmictic population, with no mutation or selection, the proportion of heterozygotes and homozygotes at each locus should be simple probabilistic functions of allele frequencies (observed heterozygosity equals expected heterozygosity).
meningitidis is effectively panmictic as a result of frequent horizontal genetic exchange (23), but that of some groupings, such as epidemic serogroup A meningococci, is largely clonal (24).