Biogeographical history of northeastern Asiatic soricine shrews (insectivora, mammalia)

A hypothetical biogeographical history of northeastern Asiatic soricine shrews in the late Quaternary was developed by integrating their present distributions, fossil records, a hypothetical phylogeny, and geological investigations. First, a biological area cladogram of the northeastern Asiatic region was constructed by applying the vicariance hypothesis to the phylogeny of thecaecutiens/shinto group, a monophyletic group proposed by Ohdachi et al. (1997). Comparing the biological area cladogram with a geological hypothesis by Ohshima (1990,1991,1992), we hypothesized a geographical history of northeastern Asia. Species were then located on the dendrogram of the geographical history, referring to the present distributions, fossil records, and phylogeny of shrews. According to our hypothesis, higher species diversity of the northern region of northeastern Asia (Hokkaido, Sakhalin, and Eastern Siberia) was achieved by several series of colonizations and habitat expansion. On the other hand, the shrew communities of the southern region (Honshu, Sado, Shikoku, and Kyushu) were created by extinction and isolation followed by speciation.