Phylogeographic

Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals. This is accomplished by considering the geographic distribution of individuals in light of genetics, particularly population genetics.

This term was introduced to describe geographically structured genetic signals within and among species. An explicit focus on a species' biogeography/biogeographical past sets phylogeography apart from classical population genetics and phylogenetics.

Past events that can be inferred include population expansion, population bottlenecks, vicariance and migration. Recently developed approaches integrating coalescent theory or the genealogical history of alleles and distributional information can more accurately address the relative roles of these different historical forces in shaping current patterns.

The term phylogeography was first used by John Avise in his 1987 work Intraspecific Phylogeography: The Mitochondrial DNA Bridge Between Population Genetics and Systematics. Historical biogeography addresses how historical geological, climatic and ecological conditions influenced the current distribution of species. As part of historical biogeography, researchers had been evaluating the geographical and evolutionary relationships of organisms years before. Two developments during the 1960s and 1970s were particularly important in laying the groundwork for modern phylogeography; the first was the spread of cladistic thought, and the second was the development of plate tectonics theory.

The resulting school of thought was vicariance biogeography, which explained the origin of new lineages through geological events like the drifting apart of continents or the formation of rivers. When a continuous population (or species) is divided by a new river or a new mountain range (i.e., a vicariance event), two populations (or species) are created. Paleogeography, geology and paleoecology are all important fields that supply information that is integrated into phylogeographic analyses.

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