Abstract
BackgroundSex-biased dispersal is widespread among mammals, including the brown bear (Ursus arctos). Previous phylogeographic studies of the brown bear based on maternally inherited mitochondrial DNA have shown intraspecific genetic structuring around the northern hemisphere. The brown bears on Hokkaido Island, northern Japan, comprise three distinct maternal lineages that presumably immigrated to the island from the continent in three different periods. Here, we investigate the paternal genetic structure across northeastern Asia and assess the connectivity among and within intraspecific populations in terms of male-mediated gene flow.ResultsWe analyzed paternally inherited Y-chromosomal DNA sequence data and Y-linked microsatellite data of 124 brown bears from Hokkaido, the southern Kuril Islands (Kunashiri and Etorofu), Sakhalin, and continental Eurasia (Kamchatka Peninsula, Ural Mountains, European Russia, and Tibet). The Hokkaido brown bear population is paternally differentiated from, and lacked recent genetic connectivity with, the continental Eurasian and North American populations. We detected weak spatial genetic structuring of the paternal lineages on Hokkaido, which may have arisen through male-mediated gene flow among natal populations. In addition, our results suggest that the different dispersal patterns between male and female brown bears, combined with the founder effect and subsequent genetic drift, contributed to the makeup of the Etorofu Island population, in which the maternal and paternal lineages show different origins.ConclusionsBrown bears on Hokkaido and the adjacent southern Kuril Islands experienced different maternal and paternal evolutionary histories. Our results indicate that sex-biased dispersal has played a significant role in the evolutionary history of the brown bear in continental populations and in peripheral insular populations, such as on Hokkaido, the southern Kuril Islands, and Sakhalin.
Highlights
Sex-biased dispersal is widespread among mammals, including the brown bear (Ursus arctos)
Sex-biased dispersal by the brown bear could have markedly affected the insular brown bear populations, and differentially affected the evolutionary history in the insular and continental populations. The hypothesis that both male and female brown bears colonized from the Eurasian Continent to Hokkaido multiple times together was supported; male-mediated gene flow played a role for homogenizing patrilineal genetic variation and resulted in the geographically indistinct paternal phylogeographic structure of brown bears in Hokkaido
Paternal phylogeography on Hokkaido Island Based on paternal DNA, Hokkaido brown bears were highly differentiated from populations in continental Eurasia and North America, indicating a lack of genetic connectivity with the continental populations (Fig. 2a; Tables 2 and 3)
Summary
Sex-biased dispersal is widespread among mammals, including the brown bear (Ursus arctos). Previous phylogeographic studies of the brown bear based on maternally inherited mitochondrial DNA have shown intraspecific genetic structuring around the northern hemisphere. Some previous phylogeographic studies of the brown bear based on maternally inherited mitochondrial DNA (mtDNA) showed extensive intraspecific geographical genetic structuring in maternal lineages [23,24,25,26,27]. The brown bear population on Hokkaido Island, northern Japan, an insular population peripheral to the Eurasian Continent, is composed of three distinct allopatrically distributed mtDNA lineages [25, 28] These three maternal lineages apparently diverged on the Eurasian Continent prior to migration onto Hokkaido via land bridges in three different glacial periods, with a southern Hokkaido lineage having colonized first, followed by eastern and central Hokkaido lineages
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