Population genetic structure ofSorex unguiculatusandSorex caecutiens(Soricidae, Mammalia) in Hokkaido, based on microsatellite DNA polymorphism

Abstract

AbstractWe investigated the genetic structure ofSorex unguiculatusandSorex caecutienspopulations in Hokkaido, Japan, using hypervariable microsatellite DNA markers. We used five microsatellite loci to type 475S. unguiculatusindividuals from 20 localities on the Hokkaido mainland and four localities from each of four offshore islands (and 11 shrews from one locality in southern Sakhalin for a particular analysis). We used six microsatellite loci to type 240S. caecutiensindividuals from 13 localities on the Hokkaido mainland. Genetic variation was high in mainland populations of both species and low in the island populations ofS. unguiculatus. Allelic richness and island size were positively correlated forS. unguiculatus, suggesting that genetic drift occurred on those islands due to small population size. In addition, four insular populations ofS. unguiculatuswere genetically differentiated from the mainland populations, although clear phylogeographic clustering was not confirmed among populations on the Hokkaido mainland for eitherS. unguiculatusorS. caecutiens. Heterozygosity excess was observed in more than half of the populations including the mainland populations of the two species, suggesting recent bottleneck events in these populations. Population dynamics of the shrews might be explained by a metapopulation scheme. According to autocorrelation analysis, the extent of non‐random spatial genetic structure was approximately 100 km. Isolation by distance was observed inS. unguiculatus, but not inS. caecutiensalthough there is a positive trend. The lack of correlation forS. caecutiensmight have been due to small sample size. Thus, no obvious differences in population genetic structure were found between the two species on the Hokkaido mainland in the present study, while previous investigations using mitochondrial DNA sequences inferred that these two species might have rather different biogeographic histories.