The Study of Genetic Differentiation among Island and Mainland Populations of the Striped Field Mouse (Apodemus agrarius Pallas, 1771) on the Basis of Microsatellite Polymorphism

Allelic diversity and genetic differentiation level among the populations of the striped field mouse Apodemus agrarius in different parts of the species range was assessed using microsatellite analysis (at six loci). The striped field mice from the four islands of Peter the Great Bay (Sea of Japan) and samples from the populations of large isolated continental areas, i.e., eastern (six samples from the localities in the south of the Russian Far East, one combined sample from Central China) and western (one combined sample from Belgorod oblast), were studied. Island and continental populations were found to contain a large number of common microsatellite alleles (62 alleles out of 84 identified). In island populations, as compared to the continental ones, depletion of the allelic composition and higher disparity of allele frequencies, including that of the unique alleles, were observed. The obtained data point to the higher differentiation level of the striped field mouse populations on the islands wich were separated from the mainland and from each other by the straits in the Holocene, compared to the differentiation among the populations inhabiting the large western and eastern isolated continental areas. Continental isolates are genetically differentiated from each other to approximately the same extent as spatially separated populations in the south of the Russian Far East and Central China within the eastern isolate. The obtained results suggest relatively recent (possibly during the Holocene climatic optimum) penetration and rapid dispersal of the striped field mouse across Western Siberia and Europe, or the existence of several “waves of invasion” in the western direction in the history of the species.