Monday, June 4, 2007 - 2:15 PM
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Nestedness in riverine freshwater mussel communities

Brenda Rashleigh, U.S. Environmental Protection Agency, 960 College Station Road, Athens, GA 30605

The pattern of nestedness, where species present at less diverse sites are subsets of species present in locations with higher species richness, is often found in ecological communities.  The pattern may indicate the mechanism by which the communities are structured and can be used to inform conservation efforts.  Nestedness was examined in four rivers in the Tennessee River basin, using mussel data collected through the Tennessee Valley Authority’s Cumberlandian Mollusk Conservation Program.   The communities appeared significantly nested compared to randomly generated matrices.  Nestedness was not related to differences in immigration probabilities.  Site diversity increased in the downstream direction, giving some indication of structuring by differences in extinction among species.  Mussel species distributions were not related to the number or distribution of their fish hosts. Nestedness may be due to a nestedness of fish hosts in terms of their abundance, where high fish host abundance promotes the survival of rare mussel species.  The understanding of diversity in these streams can aid conservation of this imperiled fauna.  Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.