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Microsatellite analysis of population structure in Canadian polar bears


  • David Paetkau is working on the application of microsatellites to a variety of population genetic questions in bears. He is student in Curtis Sh. ObecKs lab where an emphasis is currently being placed on the development of microsatellites for studying ecological and population genetic problem in a variety of wildlife species. Wendy Calvert and Ian Stirling work with the Canadian Wildlife Service- as biologist and senior research scientist, respectively, - and have over 40 years combined experience studying polar bears in the Canadian Arctic. Dr Stirling is also an adjunct professor at the University of Alberta.

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Attempts to study the genetic population structure of large mammals are often hampered by the low levels of genetic variation observed in these species. Polar bears have particularly low levels of genetic variation with the result that their genetic population structure has been intractable. We describe the use of eight hypervariable microsatellite loci to study the genetic relationships between four Canadian polar bear populations: the northern Beaufort Sea, southern Beaufort Sea, western Hudson Bay, and Davis Strait - Labrador Sea. These markers detected considerable genetic variation, with average heterozygosity near 60% within each population. Interpopulation differences in allele frequency distribution were significant between all pairs of populations, including two adjacent populations in the Beaufort Sea. Measures of genetic distance reflect the geographic distribution of populations, but also suggest patterns of gene flow which are not obvious from geography and may reflect movement patterns of these animals. Distribution of variation is sufficiently different between the Beaufort Sea populations and the two more eastern ones that the region of origin for a given sample can be predicted based on its expected genotype frequency using an assignment test. These data indicate that gene flow between local populations is restricted despite the long-distance seasonal movements undertaken by polar bears.

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