Fish community assembly in the Missouri River basin

I conducted a series of investigations to explain fish community structure and composition in the Missouri River basin. I first used an island biogeography approach to determine whether drainage area and isolation could account for native species richness and composition among western tributary drainages of the Missouri River. Both tributary drainage area and isolation were important for determining species richness and composition. A strong environmental gradient of increasing cold from downstream to upstream and dramatic climate fluctuations over the last 2.8 million years presumably account for these patterns. I also analyzed zoogeographic patterns in South Dakota for both historic and recent faunas and assessed faunal change between periods. Historic and recent faunas differed between the Great Plains and Central Lowlands geomorphic provinces and between neighboring river drainages. Great Plains and Central Lowlands faunas were homogenized and homogenization was also detected among river drainages. I also assessed relations between river size and assemblage structure and composition in four rivers of southwestern South Dakota. Each river increased in size from upstream to downstream, but discharge flashiness remained high. Species diversity was similar along each river, suggesting that high discharge flashiness may limit species diversity in larger river reaches. Downstream impacts of dams appeared to favor small river fishes and impact large river fishes. Faunal structure was less variable than faunal composition. I also examined assemblage structure and composition among five streams within the Cheyenne River watershed of South Dakota. Each stream had distinct geomorphological and hydrological attributes. Assemblage structure and composition varied between creeks and rivers. Creek assemblages had lower structural complexity than river assemblages. Composition also varied between creeks and among rivers. I also investigated ecomorphological diversity among assemblages of five streams of the Cheyenne River watershed of South Dakota. Faunal composition was different among streams, but all assemblages had high morphological similarity. As species richness increased, morphological similarity and diversity also increased. Morphological similarity was presumably due to the dominance of generalist fishes. Overall, environmental conditions appear to determine faunal composition in the Missouri River basin, while dispersal-isolation dynamics appear to be important for determining faunal structure.