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Abstract
Biodiversity is the variation of life at all levels of biological organization (Gaston and Spicer 2004). However, it is rare that biodiversity is actually studied at all levels of organization. To form a more cohesive picture of biodiversity, this means that we must consider data ranging from genes to species (or even higher taxonomic units), and from various spatial scales. It is only with data from multiple spatial scales that we begin to understand how species are distributed in a region, how species diversity is generated and maintained, and how evolution within species shapes patterns in communities. Here we investigate patterns of species and genetic diversity in communities of freshwater mussels (Unionidae) in the southeast United States. We approach this problem by combining numerical models with empirical data from regional and community scales. My methods combine the fields of biogeography, community ecology, and population genetics to elucidate the driving forces that maintain biodiversity in freshwater communities. Our results provide evidence for a regional vicariant event that is responsible for structuring diversity in freshwater mussels and possibly other freshwater taxa. Numerical simulations provide evidence for the non-neutral structuring of mussel communities influenced by both positive and negative density dependence. Patterns of genetic diversity within populations support the contemporary formation of species within the Altamaha River in Georgia with moderate spatial structuring of populations. In conclusion we find that by collecting data on 2 aspects of biodiversity, species diversity and genetic diversity, we are able to form a complete picture of forces shaping diversity in the southeast United States. Future goals of our study are to test hypotheses of mechanisms structuring freshwater communities, providing valuable data for comparison across drainages and taxa.