Role of ecological factors and reproductive strategies in structuring freshwater mussel communities
Freshwater mussel community composition within two drainage basins in Alabama, U.S.A., was better explained by patterns of variability in the fish community and the type of strategy used by mussels for infecting host-fishes than by patterns of variability in microhabitat. Mussel species richness increased in a downstream direction, and large-stream sites were characterized by a distinctive faunal assemblage that was similar between drainages. In contrast, faunal composition of headwater sites varied widely between drainages. Patterns of mussel community variation were correlated with patterns of fish community variation but not with habitat. Densities of host-specialist mussels with elaborate host-attracting mechanisms and host-generalist mussels were independent of host-fish densities, and these mussels were present throughout the drainages. Densities of host-specialist mussels without elaborate host-attracting mechanisms were correlated positively with host-fish densities and were absent or rare in headwater and midreach streams. Haag and Warren propose that mussel species dependent on host-fish density are restricted to sites with stable numbers of hosts, but mussels not dependent on host-fish density are able to persist in areas with more unstable fish assemblages, such as headwaters.