Introduced and when?
I’ve been thinking again about Cepaea hortensis (Müller, 1774) in eastern Ontario. For several years now I’ve known about a colony of this species outside of Ottawa that Fred Schueler of the Bishops Mills Natural History Centre showed me.
In our book on introduced snails and slugs (Grimm et al. 2010), we thought that this and other eastern Ontario populations were recent introductions, perhaps some intentionally brought there by Wayne Grimm as an experiment on colonization. This is certainly a possibility, as he is now linked to an introduced population of the related Cepaea nemoralis (Linnaeus, 1758) to Frederick County, Maryland (Örstan et al. 2011).
Nowadays, C. hortensis is thought to be native (in the sense that it isn’t a colonial- or Viking-era introduction) to the northeast coast (Pearce et al.2010). This species, which in North America, is nearly lives close to the coast, occurs up the St Lawrence River as far east as Quebec City (Pearce et al. 2010) or a little farther (my record east of city; and at Beaconsfield in Montreal).
Are all eastern Ontario populations of C. hortensis introduced? I don’t know. But recently, I came across mention of Cepaea in the old literature that at least invites speculation.
A Mr Gilbert C. Heron was a member of the Ottawa Field-Naturalists’ Club, and in 1880 he published one of the early lists of land snails for the Ottawa area in the Transactions of that club. The full paper is available on the Biodiversity Heritage Library. In a discussion of species remaining to be found in Ottawa, Mr Heron wrote:
Of those undiscovered shells, one of the most interesting to me is Helix nemoralis or hortensis, which is known to have been seen a few miles to the south of this city eight years ago.
It’s difficult to know what the species is from this account; at that time, C. hortensis and C. nemoralis were not always considered specifically distinct (but rather varieties). It’s reasonable to assume that this was Cepaea, but without specimens or a location, it is unlikely we’ll ever know for sure the species involved.
If we assume that the snails Heron mentioned are Cepaea hortensis, can we assume that this population is native if it was observed in 1872? Probably not — Ontario has a long colonial history — but if correct, then C. hortensis has been in Ontario longer than we had thought.
If the population was C. nemoralis, which is also likely, then it would be, by far, the earliest record of the species in Ontario.
- Grimm, F.W., R.G. Forsyth, F.W. Schueler, & A. Karstad. “2009” . Identifying Land Snails and Slugs in Canada: Introduced Species and Native Genera. Canadian Food Inspection Agency, Ottawa. iv+168 [dated 2009, published April 2010].
- Heron, G.C. 1880. On the land and fresh-water shells of the Ottawa. Ottawa Field-Naturalists’ Club, Transactions 1 (1): 36–40, 62 pl. 2 [part]. Link to BHL
- Örstan, A., Sparks, J.L. & Pearce, T.A. 2011. Wayne Grimm’s legacy: A 40-year experiment on the dispersal of Cepaea nemoralis in Frederick County, Maryland. American Malacological Bulletin 29:139-142. Link to PDF
- Pearce, T.A., Olori, J.C., and Kemezis, K.W. 2010. Land Snails from St. Elzear Cave, Gaspé Peninsula, Quebec: Antiquity of Cepaea hortensis in North America. Annals of Carnegie Museum 79 (1): 65–78.