Gene flow
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In population genetics, gene flow is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequenc
Marine iguana of the Galapagos Islands evolved via allopatric speciation, through limited gene flow and geographic isolation.
Genetic drift
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Genetic drift is the change in the frequency of an existing allele in a population due to chance.
Gene flow
…considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important…
The Effects of Genetic Drift on Different Population Sizes
Changes in a population's allele frequency following a population bottleneck: the rapid and radical decline in population size has reduced the population's genetic variation.
When very few members of a population migrate to form a separate new population, the founder effect occurs. For a period after the foundation, the small population experiences intensive drift. In the figure this results in fixation of the red allele.
Darwin's finches by Gould