UBC Theses and Dissertations
On the edge : a spatial and temporal analysis of genetic variation for endangered, peripheral American badger populations Ford, Brett
Peripheral populations are often characterized by small population size and low genetic diversity, with many at risk of extirpation. Threats to these populations may be even more pronounced in human-modified landscapes and areas of recent recolonization, that further reduce resiliency to environmental change. The western American badger (Taxidea taxus jeffersonii) is an endangered mammal in Canada inhabiting the sparse grasslands of south-central British Columbia (BC). In addition to being situated at the northwestern edge of the species’ range, recent human development and vehicle-induced mortalities have limited population recovery, causing unknown consequences on the genetic variation of these peripheral populations. By collecting mitochondrial haplotypic data and microsatellite genotypic data from roughly 300 samples in BC and neighboring regions, we assess how geographical isolation, anthropogenic disturbance, and glaciation history have shaped the genetic structure of peripheral American badger populations in this region. We discovered that the genetic structure of BC American badger populations epitomizes expectations for peripheral populations, with low levels of genetic diversity, significant differentiation, and population genetic structure all intensifying with an increase in marginality. We find evidence that these patterns, which vastly contrast those observed in central populations, are likely being influenced by geographical and anthropogenic features, that were both significantly correlated with genetic distance between individuals in western BC. Roadways were identified as potential barriers to gene flow across various scales and analyses. We also provide evidence for several glacial refugia impacting population genetic structure across the American badger range, two of which may have existed in British Columbia and the greater Pacific Northwest. Taken together, our study suggests that American badgers in British Columbia exemplify dynamics of peripheral populations, with genetic variation shaped by a unique glacial history and atypical landscape matrix, vastly contrasting central populations. Mitigating the impact of anthropogenic barriers as well as increasing connectivity between populations in BC and with populations in the United States will be essential for conserving the distinct genetic diversity of this endangered species.
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