Gene flow

<p>In <a href="/facts/Population_genetics/v55qAnKu">population genetics</a>, gene flow (also known as migration and <a href="/facts/Allele/8FxCS9KA">allele</a> flow) is the transfer of <a href="/facts/Genetic_variation/f2wzYLbI">genetic</a> material from one <a href="/facts/Population/ArxshNuB">population</a> to another.  If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation"  to prevent populations from diverging due to <a href="/facts/Genetic_drift/lvoEEctX">drift</a>. Populations can diverge due to <a href="/facts/Natural_selection/JXTte6en">selection</a> even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations.  Migrants change the distribution of genetic diversity among populations, by modifying <a href="/facts/Allele_frequencies/gRApYaIy">allele frequencies</a> (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. Gene flow has been thought to constrain <a href="/facts/Speciation/pmRTQbTK">speciation</a> and prevent range expansion by combining the gene pools of the groups, thus preventing the development of differences in genetic variation that would have led to differentiation and <a href="/facts/Adaptation/5K2gNpDB">adaptation</a> for this reason. In some cases dispersal resulting in gene flow may also result in the addition of novel genetic variants under positive selection to the <a href="/facts/Gene_pool/kYRN6qIa">gene pool</a> of a species or population (adaptive introgression.)
</p><p>There are a number of factors that affect the rate of gene flow between different populations. Gene flow is expected to be lower in species that have low dispersal or mobility, that occur in fragmented habitats, where there is long distances between populations, and when there are small population sizes. Mobility plays an important role in dispersal rate, as highly mobile individuals tend to have greater movement prospects. Although animals are thought to be more mobile than plants, pollen and seeds may be carried great distances by animals, water or wind. When gene flow is impeded, there can be an increase in <a href="/facts/Inbreeding/KRoRX08G">inbreeding</a>, measured by the <a href="/facts/Inbreeding_Coefficient/FRqB6sAW">inbreeding coefficient</a> (F) within a population. For example, many island populations have low rates of gene flow due to geographic isolation and small population sizes. The <a href="/facts/Black-footed_Rock-wallaby/CcCNeqjk">Black Footed Rock Wallaby</a> has several inbred populations that live on various islands off the coast of Australia. The population is so strongly isolated that lack of gene flow has led to high rates of inbreeding.
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Gene flow open-in-new

Gene flow