Landscape genetic analysis of population structure and factors influencing gene flow in a southern peripheral population of boreal woodland caribou (Rangifer tarandus caribou)

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 landscape factors influencing gene flow in threatened boreal woodland caribou (Rangifer tarandus caribou) based on genotypes for 337 individuals sampled at the southern extent of their distribution in Ontario. The impact of isolation by distance (IBD) and isolation by resistance (IBR) on gene flow was examined using resistance surface optimization and linear mixed-effects modelling. Genetic clustering algorithms failed to identify a biologically meaningful pattern of population substructure, consistent with the observed weak genetic differentiation of individuals across the study area. Although the inferred optimum resistance scenario differed based on the choice of genetic distance metric, roads were consistently included in the top resistance models. While our results support a growing body of evidence indicating a negative influence of roads on gene flow in woodland caribou, future studies are recommended to validate these finding given the conservation implications for this iconic boreal species.