Abstract 331 – Spatiotemporal changes in genetic diversity and structure of Asian black bear (Ursus thibetanus) over 30 years in Nagano, Japan

Ririko Koido, Misako Kuroe, Ryosuke Kishimoto, Yoshiaki Tsuda

As genetic structure of species is formed in space and time, it is important to evaluate
spatiotemporal patterns of genetic diversity not only for understanding the species’ distribution
and dispersal history but also to propose conservation management programs. However, since
most genetic diversity studies are conducted at a single time point, genetic monitoring of
species over time is crucial in conservation biology. In Japan, the highest number of human-
bear accidents and culling occurred in 2023, requiring bear monitoring and reliable
conservation management strategies. In order to monitor the bear populations and evaluate
the potential risk of management on genetic diversity, we conducted a spatiotemporal genetic
analysis of 617 black bears from 6 regions throughout Nagano, Japan. In particular, by collecting
not only genetic samples but also tooth samples and estimating the birth year for each
individual, we evaluated temporal patterns in spatial genetic structure based on individual’s
birth year over 30 years from 1986. Based on the analysis of 16 microsatellites and
mitochondrial DNA variations, although the STRUCTURE analysis detected 17 genetic clusters in
the 6 regions, clear temporal patterns were not detected in the cluster frequencies. The largest
genetic differentiation among 6 regions was maintained over 30 years across the Chikuma River
which is the longest river in Japan, acting as a genetic and geographic barrier. Only in
Yamanouchi town out of 6 regions, significant correlations between pairs of pairwise genetic
distance and birth year difference, and relatedness and geographic distance among individuals
were detected. Furthermore, although temporal change of genetic diversity was revealed, we
have not yet clarified the impact of current bear management on genetic diversity because of
the effect of spatiotemporal dispersal. This study demonstrated that combining genetic data
and age estimation can be useful for wildlife monitoring and management.