No abstract

DNA fingerprinting and mitochondrial DNA analyses have not been used in combination to study relatedness in natural populations. We present an approach that involves defining the mean fingerprint similarities among individuals thought to be unrelated because they have different mtDNA genotypes. Two classes of related individuals are identified by their distance in standard errors above this mean value. The number of standard errors is determined by analysis of the association between fingerprint similarity and relatedness in a population with a known genealogy. We apply this approach to gray wolf packs from Minnesota, Alaska, and the Northwest Territories. Our results show that:(1) wolf packs consist primarily of individuals that are closely related genetically, but some packs contain unrelated, non-reproducing individuals; (2) dispersal among packs within the same area is common; and (3) shortrange dispersal appears more common for female than male wolves. The first two of these genetically-based observations are consistent with behavioral data on pack structure and dispersal in wolves, while the apparent sex bias in dispersal was not expected.

Understanding the factors that influence the rate at which natural populations lose genetic diversity is a central aspect of conservation genetics because of the importance of genetic diversity in maintaining evolutionary potential and individual fitness. Concerns about loss of genetic diversity are particularly relevant to large carnivores, such as brown bears ( Ursus arctos ), that are distributed at low densities and are highly susceptible to human-caused population fragmentation. We used eight highly variable nuclear microsatellite markers to study current levels of genetic variation across the North American range of brown bears. The highest levels of within-population genetic diversity ( H e ϭ 0.76) were found in northern populations in the core of the North American distribution. Diversity was significantly lower in populations at the southern fringe of the distribution, in the Northwest Territories, and in southwest Alaska. Diversity was lower still in the Yellowstone Ecosystem population ( H e ϭ 0.55), an isolated remnant of the larger distribution that recently extended south from the Canadian border into Mexico. The insular population on the Kodiak Archipelago had very low genetic diversity ( H e ϭ 0.26). The Yellowstone and Kodiak data suggest that the effective population size for brown bears is much smaller than previously suspected. These results indicate that the levels of diversity in most undisturbed populations can be maintained only through connections to populations on the scale of the current North American distribution. At the same time, the Kodiak data demonstrate that populations well under the size recommended for long-term conservation can persist and thrive for thousands of years, although the probability of such persistence remains unknown. Variación en la Diversidad Genética a lo largo del Rango de Distribución del Oso Café de NorteaméricaResumen: Entender los factores que influeyen en la tasa a la cual las poblaciones naturales pierden diversidad genética es un aspecto central de la genética de la conservación debido a la importancia de la diversidad genética en el mantenimiento del potencial evolutivo y la condición individual. Las preocupaciones sobre la pérdida de la diversidad genética tiene particular relevancia para los carnivoros mayores, como lo es el oso café ( Ursus arctos ), que se distribuye a bajas densidades y que es altamente susceptible a la fragmentación poblacional causada por humanos. Para estudiar los niveles actuales de variación genética a lo largo del rango de distribución de los osos cafés, usamos ocho marcadores microsatélite nucleares altamente variables. Los niveles mas altos de diversidad genética intrapoblacional ( H e ϭ 0.76) se encontraron en poblaciones del Norte en el centro de la distribución en Norteamérica. La diversidad fue significativamente menor en poblaciones limítrofes sureñas, en los territorios del Noroeste y el Suroeste de Alaska. La diversidad fue mas baja aún en la población de Yellowstone ( H e ϭ 0.55), un remanente de una distribución...

A large microsatellite data set from three species of bear (Ursidae) was used to empirically test the performance of six genetic distance measures in resolving relationships at a variety of scales ranging from adjacent areas in a continuous distribution to species that diverged several million years ago. At the finest scale, while some distance measures performed extremely well, statistics developed specifically to accommodate the mutational processes of microsatellites performed relatively poorly, presumably because of the relatively higher variance of these statistics. At the other extreme, no statistic was able to resolve the close sister relationship of polar bears and brown bears from more distantly related pairs of species. This failure is most likely due to constraints on allele distributions at microsatellite loci. At intermediate scales, both within continuous distributions and in comparisons to insular populations of late Pleistocene origin, it was not possible to define the point where linearity was lost for each of the statistics, except that it is clearly lost after relatively short periods of independent evolution. All of the statistics were affected by the amount of genetic diversity within the populations being compared, significantly complicating the interpretation of genetic distance data.

The genetic variability of gray wolves (Canis lupus) from northwestern Canada was assessed through starch-gel electrophoresis. Of 27 protein systems examined, 25, representing 37 presumptive loci, were consistently scorable; 7 proteins (5 were consistently scorable) exhibited polymorphism. The level of heterozygosity (3.0%) was medial relative to values reported for natural populations of Carnivora and high relative to values reported for natural populations of canids. An overall pattern of few deviations from Hardy–Weinberg expectations and some spatial heterogeneity was observed. Wolves associated with different caribou herds exhibited a low level of differentiation (FST = 0.029). The pattern of variability supports the view of a large panmictic population resulting from extensive movements of individuals and packs and from natural and human impacts on pack structure and formation.