Impact of Post-Wisconsinan Range Expansions on Community Structure of North American Endemic Earthworms

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Earthworms are important constituents of most terrestrial ecosystems and have a major influence on soil structure and organic matter decomposition processes. This proposal uses a major historical event to focus on earthworms at the interface of ecology and biogeography. Differential post-glacial northward dispersal is hypothesized to have caused variation in earthworm community structure from south to north. A hierarchical approach is used to define hypotheses relating dispersal to landscape features, reproductive biology, and ecological factors. Modern climatic limitation of species ranges, competitive displacement by exotic species, and interactive structuring of communities are proposed as alternatives. A program of collecting on four south to north transects from glacial refugia across Wisconsinan glacial margins and on elevational transects south of the margins will obtain data on earthworm community structures, long-term estimates of dispersal rates, and the influence of geographic barriers on dispersal of different ecological categories of earthworms. Experiments measuring short-term dispersal rates and testing the possibility of uniparental reproduction and alternative models are proposed. A biogeographic and taxonomic data base will be created.