Patch size and isolation influence genetic patterns in black-and-white ruffed lemur (Varecia variegata) populations

Land use in Madagascar has resulted in extensive deforestation and forest fragmentation. Endemic species, such as the black-and-white ruffed lemur (Varecia variegata), may be vulnerable to habitat fragmentation due to patchy geographic distributions and sensitivities to forest disturbance. We tested for genetic differentiation among black-and-white ruffed lemur groups in two sites in a large forest patch and three sites in smaller patches. We also investigated the relationship between the genetic diversity of populations and patch configuration (size and isolation), as well as the presence or absence of past genetic bottlenecks. We collected blood (n = 22 individuals) or fecal (n = 33) samples from lemurs and genotyped the extracted DNA for 16 polymorphic microsatellites. Bayesian cluster analysis and F-ST assigned individuals to three populations: Ranomafana (two sites in continuous forest), Kianjavato (two fragments separated by 60 m of non-forest), and Vatovavy (a single fragment, more isolated in time and space). Vatovavy showed significantly lower allelic richness than Ranomafana. Kianjavato also appeared to have lower allelic richness than Ranomafana, though the difference was not significant. Vatovavy was also the only population with a genetic bottleneck indicated under more than one mutation model and a significant F-IS value, showing excess heterozygosity. These results indicate that a small geographic separation may not be sufficient for genetic differentiation of black-and-white ruffed lemur populations and that patch size may influence the rapidity with which genetic diversity is lost following patch isolation.