Migration and Selection
Since many natural populations are divided into subpopulations, it is important to investigate the effects of the joint action of selection and migration. We shall suppose that the population occupies a number of distinct niches, each of which has its own selection pattern. The niches may be defined by any pertinent set of environmental variables. If a population is distributed in clusters, this scheme provides a reasonable model for geographical variation. The study of the spatial variation of gene frequencies, however, requires more advanced analysis; see Nagylaki (1989c) and references therein. In this chapter, we shall confine ourselves to the easier problem of the maintenance of genetic diversity. For time-dependent environments, we examined this question in Sect. 4.5 by introducing the concept of protected polymorphism. We shall use the same approach here to expound multi-niche selection.
KeywordsMigration Manifold Posit Rium Haldane
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