Effects of population dynamics on genetics in mosaic landscapes

Abstract

When a species is limited to a subset of patch types in a mosaic landscape, the patch structure may subdivide it into a number of local populations interconnected by some amount of migration. If so, both the demographic and genetic characteristics of those populations are under dual local (due to birth and death events within the patch) and regional (due to immigration from other patches) control. If local populations suffer a high rate of extinction, but are replaced by the simultaneous colonization of empty patches, the system is known as a metapopulation. Attempts to model the genetic charactersitics of metapopulations have focused on whether the sampling processes associated with the founding of populations differ from the generation to generation processes of genetic drift and gene flow that are associated with more stable populations. With frequent turnover of populations the distribution of genetic variation within and among patches is determined largely by the colonization process and less so by events after colonization. Equally important are the size of colonizing groups and whether the individuals comprising a colonizing group are drawn together from a single source path or separately from several sources. When the number of occupied patches is relatively small, the frequent turnover of populations enhances the rate at which genetic variation is lost from the metapopulation as a whole. The genetic models assume that extinction and colonization are balanced such that the metapopulation will persist indefinitely. Ecological models of metapopulations focus on the conditions that will permit that persistence. This chapter questions whether the conditions under which the genetic models predict that extinction and colonization would have their greatest effects are those that would also permit persistence. -Author