Genetics is of obvious relevance to describing the partitioning of organic diversity within and between natural populations. Unfortunately, the amount of variation detected in many wildlife species using traditional markers like allozymes or mtDNA has been insufficient to address these ecological-scale questions. I developed a suite of hypervariable microsatellite markers in bears, and set out to determine their potential by studying a number of population-level problems. New methods for data analysis were also developed. The performance of six distance measures and the utility of microsatellites for studying evolutionary problems was tested using empirical data. Microsatellites appeared to be very powerful at an ecological scale, but may be of little value in evolutionary studies. Our methods based on likelihoods-of-occurrence of multilocus genotypes provided an excellent genetic distance measure, and have considerable potential for studying dispersal patterns.

A survey of polar bear populations demonstrated that populations defined using movement data do have a genetic basis, despite the long-distance movements that these animals are capable of. Patterns of ice distribution appeared to be the main cause for significant genetic discontinuities. The large brown bears of coastal Alaska, including the mitochondrially unique bears of the ABC Islands, were shown not to be genetically isolated from interior "grizzly bear" populations. These data from insular populations also illuminated patterns of male and female dispersal over various widths of ocean crossings. In contrast to coastal brown bears, Kodiak brown bears and Newfoundland black bears appeared to be ecologically isolated, and had extreme low levels of intrapopulation genetic diversity. These data, together with results from the recently isolated Yellowstone brown (grizzly) bear population, indicated that effective population size is very small in these species. As a result, short-term genetic goals for the conservation of isolated populations will only be met with very large populations, and meeting long-term genetic goals would require continued gene flow across large distributions. However, the anecdotal evidence from insular populations suggests that these genetic goals may be overly restrictive.