Functional connectivity defined through cost-distance and genetic analyses:: a case study for the rock-dwelling mountain vizcacha (Lagidium viscacia) in Patagonia, Argentina

Landscape connectivity can have profound consequences for distribution and persistence of populations and metapopulations. Evaluating functional connectivity of a landscape for a species requires a measure of dispersal rates through landscape elements at a spatial scale sufficient to encompass movement capabilities of individuals over the entire landscape. We evaluated functional connectivity for a rock-dwelling mammal, the mountain vizcacha (Lagidium viscacia), in northern Patagonia. Because of the strict association of mountain vizcachas with rocks, we hypothesized that connectivity for this species would be influenced by geology. We used molecular genetic estimates of gene flow to test spatially explicit models of connectivity created with GIS cost-distance analysis of landscape resistance to movement. We analyzed the spatial arrangement of cliffs with join counts and local k-function analyses. We did not capture and genotype individuals, but sampled at the population level through non-invasive collection of feces of mountain vizcachas. The model of landscape connectivity for mountain vizcachas based on geology was corroborated by the pattern of genetic structure, supporting the hypothesis that functional connectivity for mountain vizcachas is influenced by geology, particularly by the distribution of appropriate volcanic rocks. Analysis of spatial arrangement of cliffs indicated that occupied cliffs are clustered and confirmed that rivers act as barriers to dispersal for mountain vizcachas. Our methods could be used, within certain constraints, to study functional landscape connectivity in other organisms, and may be particularly useful for cryptic or endangered species, or those that are difficult or expensive to capture.