Doctor of Philosophy (PhD)
Ecologists and evolutionary biologists attempt to understand processes that determine distribution, abundance, and diversification of taxa through space and time. Genetic variation can provide insight into mechanisms governing the distribution and structure of natural populations, and population responses to environmental change, which in turn can have important consequences for the maintenance of species diversity. For my dissertation, I studied genetic variation of a seed-dispersing bat, Artibeus lituratus (Chiroptera: Phyllostomidae), in a heterogeneous landscape in South America, with the objective of understanding environmental and spatial forces responsible for the distribution and dynamics of populations. First, I designed thousands of primer pairs to amplify microsatellite loci for A. lituratus, for which no markers were previously available, and tested a subset on A. lituratus and 6 related phyllostomid species. I then used these data as tools to compare genetic structure in highly fragmented Alto Paraná Atlantic forest in eastern Paraguay to that in mostly contiguous forest in neighboring Misiones, Argentina. Results indicated weak genetic differentiation, and no significant correlation between genetic and geographic distance in fragmented or continuous forest. Comparison of empirical and simulated landscapes indicated empirical results were consistent with regular long-distance dispersal and high migration rates. I then determined unique and shared effects of forest configuration (measured at five spatial scales), environmental, and spatial factors on the distribution of genetic variation. Environmental factors reflecting tree composition, climate and forest structure strongly accounted for variation in genetic diversity, as did fragmentation measured at intermediate scales. Almost no variation in genetic structure was explained. Results were consistent with high levels of gene flow, which could be preventing or significantly delaying reduction in population connectivity, and strong influence of environment and fragmentation on genetic diversity, potentially mediated via population size. These findings indicated the importance of accounting for effects of multiple demographic processes, and at multiple spatial scales. My results advance our understanding of how populations respond to landscape alterations and natural environmental heterogeneity, and do so for a relatively poorly studied group of vertebrates, in a highly threatened ecosystem.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
McCulloch, Eve Sutherland, "Environmental and landscape determinants of population genetic structure and diversity of the great fruit-eating bat, Artibeus lituratus, in Atlantic forest remnants in South America" (2012). LSU Doctoral Dissertations. 1464.
Stevens, Richard D.