The advancement of landscape genetics, an increasingly sophisticated and rapidly evolving combination of population genetics and landscape ecology, has made possible refined analyses of contemporary evolutionary processes. We analyzed the distribution of microsatellite alleles at 11 loci to characterize patterns of neutral evolutionary processes among Puma. concolor (mountain lion) populations and individuals in Oregon. We sampled individuals across their statewide range with no prior assumptions of population boundaries and used an individual-based Bayesian approach to locate groups of individuals that cluster together genetically. Additionally, landscape resistance was quantified using an objective approach, whereby individual pairwise genetic distances were correlated with a variety of landscape resistance parameters for four landscape variables (slope, road density, human population density, and vegetation type). Our specific aims were to utilize intensive genetic sampling of individual P. concolor across the state of Oregon to test hypotheses regarding the presence/absence of P. concolor subspecies (or distinct genetic lineages) in the state. We hypothesized that adjacent locations of putative subspecies would naturally lead to introgression among extant lineages; we specifically address whether differences in multivariate landscape resistance contribute to isolation or facilitate introgression between divergent groups of individuals.
Results/Conclusions
Results from STRUCTURE indicate that P. concolor in Oregon are best described as two distinct, spatially organized genetic clusters (Fst=0.150, p<0.05). The distribution of these clusters follows a northeast-to-southwest axis, along which genomic ancestry coefficient values change in a sigmoid trajectory (p<0.001). This cline in genomic values, as well as a normal distribution of significant interallelic nonrandom associations, indicates ongoing introgression between discrete lineages. Of the four landscape variables that were predicted to affect gene flow patterns, only slope and vegetation type showed significant correlation with individual pairwise genetic distances. Groups of individuals pure for one or the other cluster are associated with high-quality habitat, with the area of introgression covering a large expanse of matrix near the center of the study area.