Restriction fragment length polymorphism of nuclear rDNA in Sorex caecutiens/shinto group (Eulipotyphla, Soricidae)

We estimated phylogenetic relationships among shrews of the Sorex caecutiens/shinto group (Eulipotyphla, Soricidae) from various locations through its range, based on restriction fragment length polymorphism (RFLP) analysis of the nuclear ribosomal RNA gene (rDNA) spacer region. Seven rDNA-RFLP repetitive types (repetypes) were recognized among 15 shrews examined. Restriction patterns of Sorex caecutiens Laxmann, 1788 and S. shinto Thomas, 1905 were distinguishable from each other, but the separation was not statistically supported in the maximum parsimony analysis. The RFLP repetype from Cheju Island was close to that of S. caecutiens from the Eurasian continent, indicating that the shrew of Cheju should be classified as S. caecutiens. Within S. caecutiens, there were two alternative phylogenetic hypotheses. According to a parsimonious tree and a simple network, the Hokkaido population was regarded to be derived from the Sakhalin population, which in turn was derived from the continental population. Alternatively, it was inferred that the continent and Hokkaido populations were firstly separated from the ancestral population, and then shrews from both populations immigrated into Sakhalin and hybridization occurred there. The latter hypothesis seems to be more plausible because it is more congruent with a previous mitochondrial phylogeny.