Ririko Koido, Kyoto University

In recent years, conflicts between humans and the Asian black bear (Ursus thibetanus) have become a serious social issue in the main island of Japan (Honshu), where its distribution range has expanded. In contrast, the population on Shikoku Island remains small and requires urgent conservation attention. Understanding spatial variation in genetic characteristics is essential for elucidating the factors that shape the species’ genetic structure across Japan, and for developing regionally appropriate management and conservation strategies. In this study, we evaluated genetic diversity and population structure of the black bear using genotype data on nuclear microsatellite loci from 1,857 individuals sampled across the species’ entire distribution range in Japan. Bayesian clustering analysis revealed approximately 16 genetic groups, hereafter referred to as regional populations. The genetic discontinuities among these regional populations appear to reflect the influence of landscape heterogeneity, including basin structures, mountain ranges, and anthropogenic land use. Populations in central Honshu exhibited high genetic diversity and large effective population size (Ne), indicating relatively stable demographic conditions. In contrast, populations in western Japan and northeastern Honshu showed lower genetic diversity and substantial variation in Ne, suggesting regional differences in vulnerability and demographic stability. Importantly, rare alleles maintained in some isolated populations contributed to nationwide genetic diversity, indicating that even small or isolated populations play a critical role in maintaining long-term evolutionary potential. These findings highlight the importance of incorporating regional genetic information into management and conservation frameworks to balance population control and conservation in Japan.