Landscape genetic analysis of population structure and barriers to gene flow in a managed forest range of boreal woodland caribou (Rangifer tarandus caribou)

Abstract Reductions in gene flow due to anthropogenic habitat fragmentation are often associated with reduced genetic diversity and increased population structuring in wildlife populations. We assessed fine-scale population structure and barriers to gene flow in threatened boreal woodland caribou (Rangifer tarandus caribou) in one of their southernmost ranges that contains both actively managed and unmanaged forests. A total of 763 non-invasively collected fecal DNA samples were genotyped at 12 microsatellite loci. Genetic clustering algorithms failed to identify a biologically meaningful pattern of population substructure, consistent with the observed pattern of isolation by distance (IBD). Population graphs identified two sites at the southern range periphery as genetically isolated from the remainder of the range. At the range level, genetic differentiation among sampling locations was best predicted by a combination of wildfire disturbance and geographic distance. Overall, this study suggests that woodland caribou are weakly genetically differentiated across the Brightsand Range, with both isolation by distance and isolation by resistance contributing to variation in allele frequencies.