Master of Science (MS)


Biological Sciences

Document Type



The Southeastern United States has the most diverse and imperiled freshwater mussel (Unionidae) fauna in the world. The community structure and decline of these organisms is the result of complex interactions between biotic and abiotic factors, but the limited spatial scale of most community studies has failed to elucidate the underlying mechanisms shaping community structure. Basing community assessments solely on microhabitat variables alone has lead to stark contradictions in management recommendations and opposing definitions of habitat requirements for these organisms. However, with the introduction of GIS technology into aquatic management, it is now feasible to include variables from larger spatial scales and investigate previously undetectable mechanisms influencing unionid community structure. In my study, I tested the hypothesis that patterns of mussel species richness and abundance in the Tickfaw, Tangipahoa Bogue Chitto and West Pearl rivers in south-eastern Louisiana were related to a combination of local-scale habitat variables, riparian-scale land use and geology variables, and sub-segment scale land use and geology variables. ANOVA results indicated a significant difference between the upper three sub-segments and lower three sub-segments of these rivers. The Principal Component Factor Analysis (PCFA) results revealed that geology, land-use and fine sediment are components working together across spatial scales to produce a hydrologic variability mechanism, and a simple regression model based on the factor scores of each site was successful in predicting abundance and species richness. Through comparing the ANOVA results with the factor score results for each site, I conclude that hydrologic variability, defined by geology type and land-use as well as fine sediment, is influencing the pattern in freshwater mussel abundance and species richness found in the Florida Parishes of Louisiana.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kenneth Brown