Genetic status of fragmented populations of the Asian black bear Ursus thibetanus in western Japan

The population genetic status of the Asian black bear Ursus thibetanus in the western part of Japan was examined using microsatellite DNA markers. Although three fragmented populations have been recognized in this region, i.e., the western Chugoku (WC), eastern Chugoku (EC), and northern Kinki (NK) populations, it was recently pointed out that the NK population has also been divided into two subpopulations, the western (WNK) and the eastern (ENK) populations. We examined the genetic status of these four populations based on their heterozygosities and the genetic distances (F-sr) between them. The mean observed heterozygosity, i.e., genetic diversity, of the six microsatellite loci examined, was significantly lower in WC (0.272; n = 52) and WNK (0.311; n = 66) than that in ENK (0.445; n = 67), respectively. Reflecting geographic distances among populations, F-sr was higher between WC and WNK (0.244) and between WC and ENK (0.229) than that between WNK and ENK (0.066), respectively. There was also low but significant genetic differentiation between the two nearest populations (WNK and ENK). Although the status of EC was not conclusively determined because of its small sample size (n = 24), its genetic diversity seemed to be at a level similar to that of WC and WNK. These results suggest that WC, which is isolated from the others, has been losing genetic diversity, and that WNK, which had been thought to form a relatively large population together with ENK, might be isolated genetically from other populations. WNK, as well as WC and EC, should be conserved intensively.