Effects of landscape structure on the distribution of the mountain vizcacha (Lagidium viscacia) in the Patagonian steppe (Argentina)

Metapopulation theory is used widely to analyze the dynamics of populations in fragmented habitats. Empirical studies testing predictions of metapopulation theory at regional scales, which are appropriate for conservation, are still rare. Likewise, predictions resulting from modeling in landscape ecology, which emphasizes a more spatially explicit approach, have rarely been tested empirically on real landscapes at a large scale. The objectives of this study are to evaluate the role of dispersal in the distribution of a habitat specialist in fragmented habitat, and to determine the effects of the landscape structure on dispersal. The study focuses on the mountain vizcacha (Lagidium viscacia), a rabbit-sized rodent restricted to patches of rocky habitat in the Patagonian steppe of Argentina. I evaluate the relationship between habitat structure, population structure, and social system, and explore the role of dispersal at a local scale. Then I examine the relative importance of patch-level and landscape-level factors in determining the pattern of patch occupancy by mountain vizcachas. Finally, I determine the role of landscape connectivity in the distribution of the species at a regional scale, over a 12,000 km2-area. The approach I use to determine landscape connectivity combines molecular genetic estimates of gene flow as an analog of movement rates and cost-distance analysis with GIS to model landscape resistance and facilitation of movement.; The results indicate that spatial structure of habitat affects distribution of mountain vizcachas at several scales. Within patches, mountain vizcachas are more likely to be found where rock crevices are deep and numerous. The presence of mountain vizcachas in a particular patch with appropriate rock depends on the distance and connectivity between the patch and other occupied patches. Distribution at the regional scale is a result of the pattern of connectivity at the landscape level. Connectivity for mountain vizcachas is defined by the spatial pattern of surface geology and the barrier effect of some rivers. The dependence of distribution on connectivity implicates dispersal as the key process determining distribution at the regional scale. The study emphasizes the necessity of incorporating the concept of landscape connectivity into metapopulation analyses.