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. 2016. Pre-settlement snail fauna on the Sandbanks baymouth bar, Lake Ontario, compared with nearby contemporary faunas. Canadian Field-Naturalist 130(2): 152-157.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 postglacial mollusc faunas and past ecological processes, with some potentially significant results.

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Ambient rain in southern Ontario has a volume‐weighted average pH of approximately 4.2. Tomato (Lycopersicon esculentum Mill var. ‘Chico III’) seedlings were exposed to simulated acidic rain in specially designed chambers. The inoculum of Pseudomonas tomato (Okabe) Alstatt, causal agent of bacterial speck, was sprayed on plants before or after exposure to acidic rain of pH 2.5, 3.5, and 4.5, as well as on plants not exposed to the simulated acidic rain. Speck symptoms (small, dark, brown spots with yellow halos) were found on all inoculated plants. Exposure of plants to simulted acidic rain inhibited speck development, but the inhibition was greater on plants exposed to acidic rain after inoculation than on those exposed to acidic rain before inoculation. Spot necrosis, a typical response to acidic rain, occurred on up to 15 to 20% of the leaf area on all tomato plants treated with acidic rain at pH 2.5. Plants also showed a decrease in growth (height and fresh and dry weights) with an increase in rain acidity. Leaves injured by simulated acidic rain and examined histopathologically displayed cellular malformations including hyperplasia and hypertrophy. Pseudomonas tomato failed to grow on acidified King B medium or Difco nutrient broth adjusted to pH 3.5 or lower.