Urbanization is a major threat to global biodiversity, and its impacts are projected to increase over the coming decades. Apex predators are useful indicator species of the impacts of urbanization at the wildland-urban interface, as they require a sustainable and abundant prey base, as well as high habitat connectivity to support their large home ranges. We tested whether urbanization impacts genetic connectivity and diversity in a large, apex predator with a broad geographic range, the mountain lion (Puma concolor) in the Rocky Mountains of Colorado, USA. Genetic samples were collected from 134 mountain lions across two study areas; (1) the rural Western Slope on the Uncompahgre Plateau, and (2) the Front Range adjacent to the major urban center of Denver. We used double-digest, restriction site-associated DNA sequencing (ddRADseq) to genotype mountain lions at 12,444 single nucleotide polymorphism (SNP) loci to evaluate effective population sizes, genetic diversity, and gene flow. We also correlated key landscape factors with genetic distance measures to test landscape genomic hypotheses. We hypothesized that mountain lions along the wildland-urban interface would have smaller effective population sizes, lower levels of genetic diversity, and more landscape factors related to urbanization that restrict gene flow, relative to rural areas.
Results/Conclusions
Population genomic results suggest high elevation ridgelines along the Continental Divide provide at least a partial barrier to mountain lion dispersal and gene flow across the state. Measures of genetic diversity were similar in the Western Slope and Front Range, suggesting rapid urbanization around Denver is not yet impacting the adaptive potential of mountain lions on the adjacent Front Range. However, effective population sizes were smaller in the Front Range, suggesting mountain lions may be restricted by increased exurban development and human presence. Landscape genomics revealed different habitat factors restricting gene flow in rural versus urban habitats, with the exception of riparian corridors being positively associated with gene flow across both regions. High forest cover was positively associated with gene flow only on the Western Slope, and unpaved roads appear to be used for dispersal in this rugged, rural region. In contrast, impervious surfaces and low elevation habitats restricted gene flow in the Front Range, suggesting urbanization is impacting gene flow at this wildland-urban interface. More broadly, our results demonstrate how even apex predators considered relatively tolerant of human activities can be impacted by nearby urbanization, and provide guidance for developing wildlife movement corridors in a rapidly urbanizing world.