The Role of Life History Strategies and Drying Events in Shaping Mussel Communities: A Multiscale Approach
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Life history strategies have long been used in ecological analyses and theories but have only recently been applied to frameworks for freshwater mussels, which are a highly imperiled group of organisms. One of the most severe threats for mussels in Texas is dewatering of their habitat brought on by increased frequency and intensity of droughts due to global warming together with increased anthropogenic water demand. Freshwater mussels are particularly sensitive to drying events because they are relatively sessile and cannot easily escape disturbance events. Therefore, the primary objective of this dissertation was to examine the role drying events and life history strategies play in structuring mussel communities by using a multi-scale approach spanning spatial, temporal, and organizational dimensions. Chapter 1 examined the connection between life history strategies and the individual responses of unionid freshwater mussels to drying events. This chapter proposed a life history-based framework for predicting responses of mussels to drying events. Chapter 2 assessed long-term changes in mussel community structure across multiple tributaries in the Colorado River basin, Texas after a severe drought event. This chapter showed that mussels declined post-drought, but the severity of decline depended on antecedent conditions in each tributary, including the most severe declines occurring in streams with the lowest discharge and highest estimated water temperatures. Chapter 3 combined spatially extensive surveys in the San Saba River and a life history approach to examine the factors driving the distribution of mussels at two spatial scales, including within and between river segments. The results showed that mussels with different life history strategies exhibited patchy and predictable distributional patterns and suggested the importance of environmental control including hydrological disturbances. Chapter 4 provides a synthesis and a conceptual model that can be applied to predict the distribution and structure of mussel metacommunities in rivers subject to drying events based upon life history strategies and other selective forces.