8 - Metapopulations and Coalescent Theory

Abstract

The coalescent theory, or the study of gene genealogies, provides the framework for empirical molecular population genetics. It is a rapidly moving field that at once draws upon the long history of population genetics theory and responds to the latest advances in biotechnology. The essence of the coalescent theory is that it models the genealogical history of a sample of genetic data and, via that history, makes predictions about the patterns of variation that might be observed among members of the sample. During the development of the coalescent approach between the early 1970s and the early 1980s, there was a switch in the prospective view taken by classical population genetics to a new one that begins with a sample and looks backward in time. The immense practical benefit of this was that it was no longer necessary to describe the properties of an entire population and then imagine sampling from it in order to make predictions about a sample of genetic data; only the direct ancestors of the sample mattered. This chapter describes the basic features of coalescence in unstructured populations to discuss how this forms a basis for inference about population history, and then to discuss the ways in which metapopulation structure changes these basic features and what, in turn, the prospects are for historical inference in metapopulations.