Article

Founder Effect Speciation

Alan R. Templeton

in Evolutionary Biology

ISBN: 9780199941728
Published online January 2014 | | DOI: https://dx.doi.org/10.1093/obo/9780199941728-0044
Founder Effect Speciation

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The origin of species (speciation)—the process by which two or more species evolve from a single ancestral species—is a central problem in evolutionary biology. During the evolutionary synthesis of the 20th century, the dominant theory of speciation for those working on sexually reproducing animals was allopatric speciation. Allopatric speciation posits that an ancestral species becomes subdivided into two or more geographical subpopulations by changing climates, colonization of new areas, the erection of geological barriers, etc. If these geographical subpopulations have little to no genetic interchange, they will begin to evolve separately. Speciation then arises as an incidental by-product of the independent evolution occurring within the geographical isolates. Evolution within species (microevolution) was often envisioned as being dominated by natural selection leading to adaptive divergence between the geographical isolates. However, the modern synthesis made it clear that microevolution involved many processes in addition to natural selection. One of these processes was genetic drift, the random changes in a population’s gene pool (the set of alleles or gametes collectively shared by a reproducing population) that inevitably arise from random sampling of a finite number of gametes to form the next generation. Just by chance, a particular form of a gene can decrease or increase in frequency in the population, including being completely lost or fixed. The impact of random sampling increases as the population size decreases. One special case of strong genetic drift is the founder effect, in which a population is established by a small number of founding individuals from a much larger ancestral population. Strong genetic drift in the founder population could lead to an immediate evolutionary divergence from the ancestral population. This accelerated divergence is the essence of founder effect speciation models. Founder effect speciation is a special case of allopatric speciation in which one of the geographical isolates was established from a small number of individuals. This does not mean that other microevolutionary forces, such as natural selection, are not operating, but rather that the founder effect enhances and accelerates microevolutionary divergence in concert with natural selection and other microevolutionary forces, thereby making speciation more likely.

Article.  10486 words. 

Subjects: Evolutionary Biology

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