Pre-settlement Snail Fauna on the Sandbanks Baymouth Bar, Lake Ontario, Compared with Nearby Contemporary Faunas

Résumé

The terrestrial snail fauna in a pre-settlement soil layer, radiocarbon dated at approximately 1065–1560 years old, on the baymouth bar at Sandbanks Provincial Park, Lake Ontario, was compared with 4 nearby contemporary snail faunas from forested dunes.The pre-settlement sample differed in snail diversity, with 23 species compared with 9–20 species in contemporary samples. Six species were unique to the pre-settlement sample: Carychium exile, Euconulus fulvus, Gastrocopta armifera, Gastrocopta corticaria, Vallonia parvula, and Vertigo sp. The number of individual snails was much greater at the pre-settlement site when corrected for difference in size of sample area. The reason for the higher diversity, greater number of individuals, and different fauna associated with the pre-settlement area is unclear, but may be attributed to reduction and changes in the litter layer at the contemporary comparison sites caused by European earthworms. This work suggests that major erosional and depositional events occurred on Great Lakes shoreline dunes in the past and that these can be used to study post glacial mollusc faunas and past ecological processes, with some potentially significant results.