Summary
A population genetics model of a gene locus that is pleiotropic in the sense that it causes assortative mating and also affects fitness on an environmental gradient shows that assortative mating substantially alters the adaptive response of the population. Assortative mating loci are not likely to be polymorphic at a given locale because the genotypes of the minority allele are less likely to find mates. As an assortative mating type such as an early flowering plant colonises along a selection gradient, minority disadvantage inhibits the adaptive response of the population. If selection is not intense, the population will not adapt. Once the colonial population reaches a locale where selection overcomes monority disadvantage, divergence occurs. Once initiated, divergence is accelerated by assortative mating. The combined effects of selection and assortative mating can result in rapid speciation (elimination of heterozygotes) or in the formation of a stable hybrid zone between mating types.
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Acknowledgements
Acknowledgements.-I thank A. Bradley Eisenbrey, Patrick English and Gerard Joswiak for critically reading the manuscript. This work was done at the University of Sussex under the sponsorship of a NATO Postdoctoral Fellowship in Science. Part of this work was supported by National Science Foundation Grant No. DEB 77-15352.
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Moore, W. Assortative mating genes selected along a gradient. Heredity 46, 191–195 (1981). https://doi.org/10.1038/hdy.1981.26
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DOI: https://doi.org/10.1038/hdy.1981.26
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