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Genetic Variation and Phenotypic Evolution During Allopatric Speciation
The American Naturalist
Vol. 116, No. 4 (Oct., 1980), pp. 463-479
Stable URL: http://www.jstor.org/stable/2460440
Page Count: 17
You can always find the topics here!Topics: Evolution, Population genetics, Phenotypes, Genetics, Genetic variation, Genetic mutation, Population mean, Genetic drift, Speciation, Ecological competition
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Quantitative genetic models of phenotypic evolution in small isolated populations are presented, from the initial founding event to continued random genetic drift and natural selection toward a new optimum phenotype. The basic features of complex morphologies included are polygenic inheritance with multiple allelism, pleiotropy, recombination and mutation. Gene flow, inbreeding depression, gene interaction, and genetic homeostasis are also discussed. Simpson's adaptive zones for phenotypes (analogous to Wright's adaptive topography for gene frequencies) are formulated probabilistically for small populations. It is concluded that Mayr's theory of allopatric speciation overemphasized both the genetic cohesion of widespread species and the founder effect on heterozygosity and quantitative genetic variation. However, data on the strength of natural selection and the spontaneous mutability of quantitative characters, in conjunction with the models, provide a feasible microevolutionary mechanism for substantial and geologically rapid phenotypic evolution in small isolated populations.
The American Naturalist © 1980 The University of Chicago Press