Lynda S
1 Answer
Bob/PKB
WIKIPEDIA: (check genetic drift at WIKIPEDIA, too)
A population bottleneck is a sharp reduction in size of a population due to environmental stochastic events (such as earthquakes, floods, fires, or droughts) or human activities. Such events are able to reduce the variation in the gene pool of a population drastically, because when the population was close to extinction, the few left passed on those genes to their offspring, which became mostly dominant over the generations. If there are not enough individuals left, or the ones that survived are not able to reproduce sufficiently to re-form the species population, that population may go extinct.[1] In consequence of such population size reductions and the loss of genetic variation, the ability of a population to adapt to prevalent environment or selection like climatic change or shift in available resources is reduced. However, depending upon the causes of the bottleneck, the survivors may have been the most fit individuals, hence improving the traits within the gene pool while shrinking it. This genetic drift can change the proportional distribution of an allele by chance and even lead to fixation or loss of alleles. Due to the smaller population size after a bottleneck event, the chance of inbreeding and genetic homogeneity increases and unfavoured alleles can accumulate. Thus, an ecological bottleneck can lead to a genetic bottleneck, in which the genetic variation within a population and the potential to adapt to a changing environment decrease.
A slightly different form of a bottleneck can occur, if a small group becomes reproductively (e.g. geographically) separated from the main population, for example through a founder event. Population bottlenecks play an important role in conservation biology (see minimum viable population size) and in the context of agriculture (biological/pest control).[2]
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