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Occurrence of the Copse Snail, Arianta arbustorum (Helicidae), on Prince Edward Island: An Addition to the North American Range of a Purported Potential Pest
Donald F. McAlpine and Robert G. Forsyth

Northeastern Naturalist, Volume 21, Issue 1 (2014): N5–N7

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N5 2014 Northeastern Naturalist Notes Vol. 21, No. 1 D.F. McAlpine and R.G. Forsyth Occurrence of the Copse Snail, Arianta arbustorum (Helicidae), on Prince Edward Island: An Addition to the North American Range of a Purported Potential Pest Donald F. McAlpine1,* and Robert G. Forsyth1,2 Abstract - We report the first occurrence of Arianta arbustorum (Copse Snail) on Prince Edward Island, expanding its well-established presence in eastern Canada. Although listed as an exotic mollusc for which prevention of introduction to the US is a priority, the evidence from Canada to date suggests a low pest potential for this species. It is unlikely that eradication efforts in North America would be effective; thus, the Copse Snail may be a poor candidate for pest -prevention efforts in the US. As a result of increased global travel and trade, the introduction of species to regions outside their native range has accelerated over the past half-century (Meyerson and Mooney 2007). Such introductions are now considered one of the principal threats to native biodiversity (Simberloff et al. 2005). In a preliminary risk assessment, Cowie et al. (2009) listed Arianta arbustorum (L.) (Copse Snail) 43rd among 46 non-marine invasive gastropods for which the prevention of introduction and establishment in the US was a priority. At one time considered extirpated in North America (Pilsbry 1939), this terrestrial snail appears to have been established locally for at least some decades at sites in southern Ontario and New Brunswick, and for perhaps more than a century on Newfoundland (McAlpine et al. 2009). Because information about current or anticipated distributions is used to set priorities for the control of non-native species (Byers et al. 2002), it is important to document range changes of any potential pest. There is general agreement that invasive species display a lag time between colonization and establishment and the onset of rapid population growth and subsequent range expansion. However, it is not clear if the lag phase is real, or simply a failure of researchers to observe the beginning of exponential increase (Sakai et al. 2001). This uncertainty emphasizes the need to document changes in the range and abundance of non-native species during the early phases of establishment. Here we report the first documented occurrence of the Copse Snail on Prince Edward Island, and comment on whether it would be useful to include this species in a revised US list of potential mollusc pests. On 2 July 2013, Stacey Kuypers collected 2 specimens of Copse Snail about 33 m apart along the grassy edge of the Confederation Trail, Summerside, Prince County, PE, Canada (46o40714N -63o.80357W; New Brunswick Museum [NBM] mollusc collection 8901). On 19 July 2013, D.F. McAlpine visited the same site, and after 2 h of searching, collected a single specimen (NBM 8902; Fig. 1) from under bark on the floor of a hedgerow adjacent to agricultural land that bordered the walking trail. No Copse Snails were observed in the open, although another helicid snail, Cepaea hortensis (O.F. Müller) (White-lipped Snail) was abundant. This 1New Brunswick Museum, 277 Douglas Avenue, Saint John, NB, Canada E2K 1E5. 21890 McKinley Court, Kamloops, BC, Canada V2E 2L9. *Corresponding author - donald.mcalpine@nbm-mnb.ca. Manuscript Editor: Robert Hershler Notes of the Northeastern Naturalist, Issue 21/1, 2014 2014 Northeastern Naturalist Notes Vol. 21, No. 1 N6 D.F. McAlpine and R.G. Forsyth section of trail passes through a mosaic of agricultural lands, suburban housing, wetlands, and isolated patches of mixed forest. The trail, developed in the 1990s, is a former railway bed that ceased to carry railway traffic by 1989. In developing their list of priority molluscs for prevention of introduction to the US, Cowie et al. (2009) included only species judged to have the potential to cause damage to agriculture or natural ecosystems. They did not include species that were already established in the country, unless their distribution was so restricted that eradication was possible. McAlpine et al. (2009) showed that while Copse Snails are intercepted relatively infrequently on imports to the US and Canada, the cumulative number of animals involved is significant. At the time Cowie et al. (2009) developed their list, they would have been unaware that the Copse Snail was already well-established in Canada. Our own observations of this species in four Canadian provinces suggest that although populations may be expanding, to date there is no evidence that the Copse Snail can be considered a pest species in Canada. In Britain and Ireland, the species has been reported from herbage and ground litter in woods, lush roadsides, river floodplains, and sea cliffs (Kerney 1999). Human disturbance of natural communities may increase susceptibility to invasion of exotic species (Sakai et al. 2001). In North America, we have found that Copse Snails are generally restricted to human-modified habitats, especially disturbed woodland, woodland edges, and Figure 1. Habitat (A) and Arianta arbustorum (B) at Summerside, PE, Canada. The walking trail formerly supported a railway line. N7 2014 Northeastern Naturalist Notes Vol. 21, No. 1 D.F. McAlpine and R.G. Forsyth waste ground adjacent to such areas (McAlpine et al. 2009). Habitat on Prince Edward Island is heavily fragmented (Silva et al. 2003) and is primarily a mosaic of agricultural lands, remnant woodlands, and hedgerows. Such habitats may provide widespread opportunity for Copse Snails to become established, which suggests that the occurrence documented here may not be an isolated one on Prince Edward Island. The apparent association of the species with rail-lines or former rail-lines on Newfoundland (McAlpine et al. 2009) and Prince Edward Island also suggests trains as a possible means of dispersal in North America. Cowie et al. (2009) ranked the Copse Snail relatively low in terms of pest potential, and thus far, evidence in Canada supports this assessment. Combined with what we now consider the low probability of eradication in North America, the Copse Snail appears to be a poor candidate for pest-prevention ef forts in the US. Acknowledgments. We are grateful to Stacey Kuypers for contacting us to identify snails and for agreeing to collect material of A. arbustorum for us, and to Rosemary Curley, Forests, Fish, and Wildlife Division, Prince Edward Department of Agriculture and Forestry, who accepted and temporarily cared for live specimens on our behalf. Literature Cited Byers, J.E., S. Reichard, J.M. Randall, I.M. Parker, C.S. Smith, W.M. Lonsdale, I.A.E. Atkinson, T.R. Seastedt, M. Williamson, E. Chornesky, and D. Hayes. 2002. Directing research to reduce the impacts of nonindigenous species. Conservation Biology 16:630–6 40. Cowie, R.H., R.T. Dillon, Jr., D.G. Robinson, and J.W. Smith. 2009. Alien non-marine snails and slugs of priority quarantine importance to the United States: A preliminary risk assessment. American Malacological Bulletin 27:113–132. Kerney, M. 1999. Atlas of Land and Freshwater Molluscs of Britain and Ireland. Harley Books, Essex, UK. McAlpine, D.F., F.W. Schueler, J.E. Maunder, R.G. Noseworthy, and M.C. Sollows. 2009. Establishment and persistence of the Copse Snail, Arianta arbustorum (L.) (Gastropoda: Helicidae) in Canada. The Nautilus 123:14–18. Meyerson, L.A., and H.A. Mooney. 2007. Invasive alien species in an era of globalization. Frontiers in Ecology and the Environment 5:199–208. Pilsbry, H.A. 1939. Land Molluscs of North America (North of Mexico). Monographs of the Academy of Natural Sciences of Philadelphia 3:1–573. Sakai, A.K., F.W. Allendorf, J.S. Holt, D.M. Lodge, J. Molofsky, K.A. With, S. Baughman, R.J. Cabin, J.E. Cohen, N.C. Ellstrand, D.E. McCauley, P.O’Neil, I.M. Parker, J.N. Thompson, and S. G. Weller. 2001. The population biology of invasive species. Annual Review of Ecology and Systematics 32:305–332. Silva, M., L.A. Hartling, S.A. Field, and K. Tether. 2003. The effects of habitat fragmentation on amphibian species richness on Prince Edward Island. Canadian Jo urnal of Zoology 81:563–573. Simberloff, D., I.M. Parker, and P.N. Windle. 2005. Introduced species policy, management, and future research needs. Frontiers in Ecology and the Environment 3:12–20