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Exotic Earthworm Invasions in North America: Ecological and Policy Implications

2002; Oxford University Press; Volume: 52; Issue: 9 Linguagem: Inglês

10.1641/0006-3568(2002)052[0801

1525-3244

Paul F. Hendrix, Patrick J. Bohlen,

Insect Utilization and Effects

ArticlesE arthworms are the best known and, in many situations, the most important animals that live in soil.Over 3500 earthworm species have been described worldwide, and it is estimated that further surveys will reveal this number to be much larger (Reynolds 1994, Fragoso et al. 1999).Distinct taxonomic groups of earthworms have arisen on every continent except Antarctica, and, through human transport, some groups have been distributed worldwide (Jamieson 1988, Reynolds 1994).The earthworm fauna of North America, including Canada, the continental United States, Mexico, and the islands of the Caribbean, consists of both native (Nearctic and Neotropical) and exotic species imported from many other regions of the world (Fender 1995, Fragoso et al. 1995, James 1995, Reynolds 1995).Any given locality may be inhabited by all native species, all exotic species, a combination of native and exotic species, or by no earthworms at all.Relative abundance and species composition of local fauna depend greatly on soil, climate, vegetation, topography, land use history, and especially on past invasions by exotic species.Much of our knowledge of the earthworm fauna of North America is based on the work of Gordon E. Gates who, over a 60-year career, collected, described, and cataloged many of the currently recognized taxa, both native and exotic.Beginning in 1949, Gates collaborated with the US Department of Agriculture (USDA), Bureau of Plant Quarantine (now Animal and Plant Health Inspection Service, or APHIS) to intercept oligochaetes found in "plant-associated materials" (mostly soil) being imported into the United States.Over a 32-year period , Gates (1976Gates ( , 1982) ) acquired thousands of specimens and was able to determine that earthworms from all over the world were continually being imported.There is no reason to expect that this situation has changed since 1982.Indeed, as with exotic plants, fungi, and insects (Ruesink et al. 1995, Campbell 2001, Mack and Lonsdale 2001), growing global commerce may be increasing the likelihood that exotic earthworms will be introduced, both inadvertently with the importation of soil-containing materi-als (e.g., agricultural and horticultural products; Gates 1976, 1982, Boag and Yeates 2001, Ehrenfeld and Scott 2001) and intentionally for use in commercial applications (e.g., waste management and land bioremediation; Lee 1995, Edwards 1998).Because previous invasions by exotic earthworms have had significant impacts on soil processes and plant communities in native ecosystems (e.g., Alban and Berry 1994, Groffman and Bohlen 1999, Hale et al. 2000), there may be reason for concern over continued unrestricted importation of earthworms.Regulatory activities have not been effective in reducing earthworm introductions in most areas of the world (Boag and Yeates 2001), probably because legal restrictions traditionally have not targeted earthworms or their propagules.There presently are no specific regulations concerning earth-