Biodiversity at the intraspecific level: The comparative phylogeographic approach
Résumé
Biodiversity, or biological diversity encompasses species richness as well as intraspecific genetic variation. The knowledge of intraspecific variation is of prime importance for biotechnologists who want to use a wild species as a genetic resource. A total of eight comparative phylogeographic studies available at the moment are reviewed in order to deduce general rules governing the geographic distribution of intraspecific biodiversity. Three studies are continent-wide surveys, in North America or in Europe, while the others deal with more restricted areas. Although the overall information is still scarce, two interesting trends have been deduced. First, the level of intraspecific polymorphism seems to be lower at higher latitude, particularly in areas glaciated during Pleistocene cold periods, and most of the variation lies in areas that corresponded to refugia during range contractions. Second, the evidence for concordance of phylogeographic patterns among taxa are controversial; all the studies concerning a limited geographic area suggest a certain level of concordance, whereas the continent-wide surveys argue more for nonconcordant patterns. In order to survey as much as possible of the intraspecific genetic variation, I suggest sampling in widespread localities, and to pay special attention to areas that are thought to be refugia during cold periods. (C) 1998 Elsevier Science B.V. All rights reserved.