Panmixia


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Related to Panmixia: panmictic

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

References in periodicals archive ?
However, the limited control by human beings over the choice of partners and the generation of litters with simultaneous fatherhoods, dramatically increase the genetic flow within populations, inbreeding reduces and increases panmixia.
Considering the eels vital cycle, panmixia is expected in each location together with no linkage disequilibrium nor differentiation between locations of the same subspecies.
The barriers to panmixia that maintain genetic population differentiation induce within-population genetic correlation.
Likewise, the multilocus test by population showed departure from panmixia in all populations with a significant (P <0.
When divergence between populations or species occurs under gene flow, the process can be viewed as a continuum from panmixia to complete reproductive isolation as time progresses (Via, 2009; Seehausen et al.
The data are also supported by analyses of nuclear microsatellites which show panmixia of all taxa at the Coeur d'Alene site.
The increasing literature on population genetics in amphidromous species has often revealed widespread panmixia, but not in all cases (e.
Likewise, population panmixia was found for a gastropod, Neritilia granosa, in anchialine caves separated by 200 km of sea in the Philippines (Kano & Kase 2004).
Despues de varias generaciones de panmixia quedo establecida una poblacion con alta variabilidad genetica.
On the other hand, a high level of genetic variability and the occurrence of panmixia were observed in Colossoma macropomum (Cuvier, 1816) (Santos et al.
Increasing the coancestry within progenies requires sampling of a larger number of seed parents to obtain an N, value equivalent to that obtained in a situation of panmixia with half-sib families,
These pedigrees were generated under assumptions that ranged from complete panmixia (fathers chosen at random from the entire linear array) to situations in which fathers were chosen from within two array locations on either side of the mother.