Fine-scale genetic structure of the ringtail (Bassariscus astutus) in a Sky Island mountain range

Abstract

Landscape complexity provides opportunities for local adaptation and creates population genetic structure at limited geographic scales. We determined if fine-scale genetic structure was evident in a population of ringtails (Bassariscus astutus) inhabiting the Guadalupe Mountains, a small, isolated, and ecologically diverse mountain range in the southwest United States. We hypothesized that ringtails would exhibit either a genetic pattern of isolation by distance (IBD), because their small body size would most likely limit dispersal distances, or a pattern of isolation by resistance (IBR), because the topographical complexity of the mountain range would result in complex dispersal patterns. To investigate for the presence of fine-scale genetic structure in this population, we genotyped 153 ringtails at 15 microsatellite loci and described genetic structure using 2 Bayesian clustering techniques. Six genetic clusters were identified revealing complex spatial genetic structure within a localized geographic area. We used partial Mantel tests to test for a correlation between genetic distance and geographic distance or resistance distance but found no evidence for a genetic pattern related to IBD or IBR. We subsequently tested for an association between genetic structure and isolation by environment (IBE) using a discriminant function analysis and classified a high proportion of individuals (> 91%) to their observed genetic cluster based exclusively on landscape features. We also used a nonparametric, multivariate analysis of variance to further explore the role of land-cover type and found that plant association explained 26% of the genetic variation. These results suggest that IBE influences the genetic structure of ringtails at local geographic scales, a finding that deserves consideration in conservation planning.