Print PageThe pervasive effects of factors such as habitat degradation and loss, disease and unsustainable harvesting have highlighted the need for on-going management and restoration of animal populations throughout the world. Increasing extinction rates and decreasing population sizes have made comprehensive wildlife management plans critical for successful protection of existing species. This study focuses on a population genetic analysis of five bighorn sheep (Ovis canadensis) herds in and around Rocky Mountain National Park: Continental Divide, Never Summer, St. Vrain, Big Thompson and Mummy. The Mummy herd suffered a severe pneumonia outbreak in the mid 1990s followed by a significant die-off. Since that time, recruitment has remained low and the population has failed to rebound. One theory is that this sudden reduction in herd size created a genetic bottleneck and subsequent inbreeding depression. Alternatively, environmental stressors such as malnutrition, disease and habitat fragmentation from roads or trails may also be driving this trend. Quantification of population genetic parameters allows for a clearer understanding of genetic variation within each herd, relative variation among herds as well as how geneflow is affecting substructure within this metapopulation. These data assist informed management decisions and effective protection of Rocky Mountain bighorn sheep now and into the future.
Results/Conclusions
Non-invasive field collection techniques provided DNA from 137 total individuals for genotyping at 13 microsatellite markers as well as sequencing of two mitochondrial regions (COI and D-Loop). Allelic distributions and Fis calculations indicate that that no herd, including the Mummy, shows a clear signal of recent genetic bottlenecks or inbreeding (Mean Fis = -0.01 to 0.12) and that variation at individual loci is generally consistent among herds. Comparisons of overall Fst values for both microsatellite loci (Fst = 0.047) and mitochondrial haplotypes (Fst = 0.25) indicate low population substructure maintained by moderate levels of gene flow. Pair-wise Fst values for both microsatellites (0.021 to 0.09) and mitochondrial DNA (0.02 to 0.44) show a pattern of increasing isolation by distance where the Continental Divide is a partial barrier to gene flow between herds. These data further indicate that the consistent levels of genetic variation among herds are maintained primarily via ram migration while ewes are generally philopatric within this metapopulation. These data support the theory that the Mummy herd’s failure to thrive is likely due to environmental factors. Thus, restoration efforts should be focused on ameliorating these potential causes while transplantation is unlikely to increase long-term persistence of these herds.
