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Effects of Exotic Earthworms E-mail
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Wednesday, 20 June 2007

Effects of Exotic Earthworms


 Snyder, BA1, PF Hendrix1,2, and MA Callaham Jr.3

 1Institute of Ecology, University of Georgia, Athens, GA, USA;

2Department of Crop & Soil Sciences, University of Georgia, Athens, GA, USA;

3USDA Forest Service, Southern Research Station, Athens, GA, USA

Invasion by exotic earthworm species is a well-established issue in ecology.  While the effects of invasions in regions without a native earthworm fauna are well documented, quantitative information about the effects of invasion in regions with a native earthworm fauna is sparse.  Since the first reports of these invasions in North America (Eisen 1900, Smith 1928) numerous studies have documented exotic species dominating in locations that were once dominated by native species.  No studies have been able to document extirpation of native fauna due to exotic earthworm invasion.

One reason for this may be the paradigm that currently dominates the issue of earthworm invasions in North America.  In this theory, which Kalisz and Wood (1995) use to explain exotic and native earthworm distribution patterns, native earthworms are lost due to disturbance before the exotics invade.  This disturbance theory predicts that exotics will dominate in disturbed areas and native fauna will dominate in relatively undisturbed areas.  This situation does not allow for examination of the effects of invasions on native fauna, because under the current paradigm exotics and natives are not thought to interact. 

A recent invasion of Amynthas agrestis from a roadside edge of the Great Smoky Mountains National Park (North Carolina and Tennessee, USA) appears to fit into the current paradigm, as the roadside would be certainly be considered disturbed.  However, this invasion presents the opportunity to move beyond the paradigm as the invasion proceeds into undisturbed forest.  We present preliminary results from a study in which we examine changes in biodiversity of the earthworm community due to A. agrestis invasion.  We also characterize the movement of the invasion front and use this data to begin to develop a model predicting future spread of this invasive exotic earthworm species.

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