Testing concordance and conflict in spatial replication of landscape genetics inferences
The degree to which landscape genetics results can be extrapolated to different areas of a species range is poorly understood. Here, we used a broadly distributed ectothermic lizard (Sceloporus occidentalis, Western Fence lizard) as a model species to evaluate the full role of topography, climate, vegetation, and roads on dispersal and genetic differentiation. We conducted landscape genetics analyses in five areas within the Sierra Nevada mountain Genetic distances calculated from thousands of ddRAD markers were used to optimize landscape resistance surfaces and infer the effects of landscape and topographic features. Across study areas, we found a great deal of consistency in the variables impacting genetic connectivity, but also noted site-specific differences in the factors in each study area. High-elevation colder areas were consistently found to be barriers to gene flow, as were areas of high ruggedness and slope. High temperature seasonality and high precipitation during the winter wet season also presented a substantial barrier to gene flow in a majority of study areas. The effect of other landscape variables on genetic differentiation was more idiosyncratic and depended on specific attributes at each site. Across study areas, canyons were always substantially implicated as facilitators to dispersal and key features linking populations and maintaining genetic connectivity across landscapes. We emphasize that spatial data layers are complex and multidimensional, and a careful consideration of associations between variables is vital to form sound conclusions about the critical factors affecting dispersal and genetic connectivity across space.