Genetic distinctness and variation in the Tsushima Islands population of the Japanese marten, Martes melampus (Carnivora: Mustelidae), revealed by microsatellite analysis.

A carnivoran mammal endemic to Japan, the Japanese marten (Martes melampus) is native in forested regions on Honshu, Shikoku, Kyushu (main islands of Japan), and the Tsushima Islands. The Tsushima population is classified as a different subspecies (M. m. tsuensis) from populations on the main islands (M. m. melampus). To elucidate the genetic structure of the Tsushima population, we genotyped 101 individuals from the Tsushima Islands and 43 individuals from Honshu and Kyushu using 10 microsatellite loci, and performed population genetic analyses on the genotype data. Genetic diversity was lower in the Tsushima population than in three geographic populations on the main islands: heterozygosity was 0.189-0.364 in the former, compared to 0.457-0.747 in the latter. In addition, high pairwise Fst values (0.485-0.682) and Nei's standard distance (0.550-1.183) between the Tsushima and main-island populations indicated a high degree of genetic differentiation. Finally, a Bayesian clustering analysis showed that the Tsushima population is apparently differentiated from the main-island populations and comprises two genetic clusters. A factorial correspondence analysis corroborated these results. Our results suggest that restricted gene flow or inbreeding may have reduced genetic diversity in the Tsushima population, which has been geographically isolated from the main-island populations since the formation of Tsushima Strait.