Evolutionary trends of the mitochondrial lineage differentiation in species of genera Martes and Mustela

We compared partial sequences (402 bp) of the mitochondrial cytochrome b ge ne in 68 individuals of martens (Martes), weasels (Mustela) and their relat ives from the Northern Hemisphere to identify the modes of geographic diffe rentiation in each species. We then compared complete sequences (1140 bp) o f the gene in 17 species of the family Mustelidae to know the spatial and t emporal modes of speciation, constructing linearized trees with transversio nal substitutions for deeper lineage divergences and with transversions and transitions for younger lineages. Our data suggested that these lineages o f Martes and Mustela differentiated in a stepwise fashion with five radiati on stages from the generic divergences (stage I) to the intraspecific diver gences (stage V), during the last 10 or 20 million years as the fossil evid ence suggests. In the lineage of Martes, the first offshoots are of Martes flavigula, M. pennanti, and Gulo gulo (stage II), the second is M. foina (s tage III), and the third are M. americana, M. martes, M. melampus, and M. z ibellina (stage IV). The divergence of the lineages of Mustela is likely to have taken place concurrently with the radiations of the Martes. These div ergence processes are attributable in part to the geographic allocation alo ng the two continents, North America and Eurasia, as well as among peripher al insular domains, such as Taiwan and the Japanese Islands. In addition, t he Eurasian continent itself was shown to have been involved in the species diversification in the martens and weasels.