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A population bottleneck may also cause a founder effect, though it is not strictly a new population. The founder effect occurs when a small group of migrants—not genetically representative of the population from which they came—establish in a new area.
Population bottleneck followed by recovery or extinction. A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling.
The founder effect is a special case of a population bottleneck, occurring when a small group in a population splinters off from the original population and forms a new one. The random sample of alleles in the just formed new colony is expected to grossly misrepresent the original population in at least some respects. [44]
Another possible cause of genetic divergence is the bottleneck effect. The bottleneck effect is when an event, such as a natural disaster, causes a large portion of the population to die. By chance, certain genetic patterns will be overrepresented in the remaining population, which is similar to what happens with the founder effect. [4]
Wahlund effect; Regression toward the mean; Multinomial distribution (Hardy–Weinberg is a trinomial distribution with probabilities (, (), ())) Additive disequilibrium and z statistic; Population genetics; Genetic diversity; Founder effect; Population bottleneck; Genetic drift
Population size is directly associated with amount of genetic drift, and is the underlying cause of effects like population bottlenecks and the founder effect. [1] Genetic drift is the major source of decrease of genetic diversity within populations which drives fixation and can potentially lead to speciation events. [1]
A bottleneck can reduce or eliminate genetic variation from a population. Further drift events after the bottleneck event can also reduce the population's genetic diversity. The lack of diversity created can make the population at risk to other selective pressures. [36] A common example of a population bottleneck is the Northern elephant seal ...
Founder effect— the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. [3] [4] It is a special case of genetic drift, where subsequent generations may have less genetic variation than the original population, which leads to fixation.