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The Bottleneck Effect and Genetic Variability in Populations

Masatoshi Nei, Takeo Maruyama and Ranajit Chakraborty
Evolution
Vol. 29, No. 1 (Mar., 1975), pp. 1-10
DOI: 10.2307/2407137
Stable URL: http://www.jstor.org/stable/2407137
Page Count: 10
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The Bottleneck Effect and Genetic Variability in Populations
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Abstract

When a population goes through a small bottleneck, the genetic variability of the population is expected to decline rapidly but, as soon as population size becomes large, it starts to increase owing to new mutations. This problem is studied mathematically, and the results obtained indicate that the amount of reduction in average heterozygosity per locus depends not only on the 'size of bottleneck' but also on the rate of population growth. If population size increases rapidly after going through a bottleneck, the reduction in average heterozygosity is rather small even if bottleneck size is extremely small. On the other hand, the loss in the average number of alleles per locus is profoundly affected by bottleneck size but not so much by the rate of population growth. This difference occurs mainly because random genetic drift eliminates many low frequency alleles. However, the average number of alleles per locus increases faster than the average heterozygosity when population size is restored. Application of the theory developed to the Bogota population of Drosophila pseudoobscura supports Prakash's postulate that this population has grown very rapidly, starting from a few migrants from a Central or North American population.

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