Founder effect

The founder effect is an evolutionary phenomenon. Founder effects arise when an isolated environment is invaded by only a few members of a species, which then multiply rapidly. In the extreme case, a single fertilised female might arrive in a new environment. It is a type of population bottleneck.

Related Topics:
Evolution - Species - Population bottleneck

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The result of the small number of founders is that there is a sharp loss of genetic variation compared with the parent population. As a result, the new population may be distinctively different, genetically and phenotypically, from the parent population it derived from. In addition, there is a raised probability of inbreeding, resulting in an unusual number of defects due to recessive genes.

Related Topics:
Genetic - Genetically - Phenotypically - Inbreeding - Recessive gene

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Founder effects are common in island ecology, but the isolation need not be geographical. For example, the Amish populations in the United States, which have grown from a very few founders but have not recruited newcomers, and tend to marry within the community, exhibit founder effects: phenomena such as polydactyly (extra fingers and toes, a symptom of Ellis-van Creveld syndrome), though still rare absolutely, are more common in Amish communities than in the US population at large.

Related Topics:
Island ecology - Amish - United States - Polydactyly - Ellis-van Creveld syndrome

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In extreme cases, founder effects may lead to the speciation and subsequent evolution of new species.

Related Topics:
Speciation - Evolution

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The founder effect is a feature that can also occur in memetic evolution.

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