A Comparison of Genetic Diversity in North American Brown Bears

To determine if threatened brown bear (Ursus arctos) populations of Montana and Wyoming have lower levels of genetic variation than other North American populations, we examined mitochondrial DNA (mtDNA) and nuclear microsatellite DNA diversity in 220 brown bears from 5 areas: Kodiak Island, Alaska; Kluane National Park, Canada; Eastern Slope of the Rockies (East Slope), Canada; Yellowstone ecosystem (YE), Wyoming and Montana; and Northern Continental Divide Ecosystem (NCDE), Montana and British Columbia. Nei's genetic diversity (h) was estimated by analyzing 296 base pairs of control region sequence data from mtDNA and by nuclear microsatellite analysis of 8 independent loci. Genetic diversity was lowest in the Kodiak Island sample. The YE and East Slope samples had intermediate levels of mtDNA diversity and microsatellite diversity. Kluane and NCDE samples had high levels of mtDNA diversity and microsatellite diversity. Genetic diversity in the YE and NCDE samples was lower than in the Kluane sample; however, these differences were statistically signficant (P < 0.05) for only 1 microsatellite locus in the YE sample. In contrast, the Kodiak Island sample had significantly less diversity (P < 0.05) than the Kluane sample at the mtDNA locus and 6 microsatellite loci. Because genetic diversity has been suggested as critical for the evolutionary fitness of wild populations, the management implications of these results are examined and discussed.