Intraspecific phylogeny and geographical variation of six species of northeastern Asiatic Sorex shrews based on the mitochondrial cytochrome b sequences

Intraspecific phylogeny and genetic variation were investigated based on nu cleotide sequences of the mitochondrial cytochrome b gene in six soricine s hrew species, Sorex unguiculatus, S. caecutiens, S. shinto, S. gracillimus, S. minutissimus and S. hosonoi, collected primarily from northeastern Asia . Maximum likelihood trees and a phylogenetic network were generated to est imate intraspecific phylogenies. S. minutissimus showed high congruence bet ween phylogenetic position and geographical origin and S. gracillimus showe d low congruence. In contrast, there was no congruence between phylogeny an d geography in S. unguiculatus and the S. caecutiens from Sakhalin-Eurasia. Positive correlation between genetic and geographical distances was found in S. minutissimus and S. gracillimus, but not in the other species (or reg ional populations). The results of the phylogenetic and genetic analyses su ggest that S. minutissimus and S. gracillimus have occupied their present r anges for a longer time than the other species if we assume a stepping-ston e model of population structure. In addition, there was no contradiction be tween the present investigations and the hypotheses of multiple immigration by S. gracillimus and a single immigration by S. unguiculatus into Hokkaid o Island. It is proposed that these six northeastern Asian species experien ced different historical processes of range expansion and dispersal despite the fact that some of them currently show similar patterns of distribution .