Responses of Spotted Salamander, Ambystoma maculatum, populations in central Ontario to habitat acidity

Reproductive success of the Spotted Salamander, Ambystoma maculatum, was monitored in twenty ephemeral ponds in central Ontario that had varying pH, alkalinity, and calcium concentrations. Mean pH of the ponds ranged from 4.55 to 6.37 and alkalinity from -0.4 to 12.2 mg/L CaCO; (calcium carbonate). Hatching success ranged from 0 to 99%. Stepwise multiple linear regression analysis selected alkalinity and pond area as predictors of the total number of egg masses/ pond and the total number of eggs hatched/ pond. The best predictor of hatching success was pH. Hatching success was 80% in a pond at pH 4.51. This was significantly lower than the 88% hatching success observed in a pond at pH 6.15. Larvae exposed in a pond at pH 4.97 had greater survival (64%) in enclosures where CaCo, was added and the pH elevated to 5.30 than in enclosures without CaCO, additions (46% survival). Eggs collected from one pond at pH 4.51 and another pond at pH 6.21 had similar hatching success when exposed at pH 4.51. This suggests that the egg stage of both populations of salamanders was equally tolerant of acidity. Survival of larvae collected as eggs from a pond with pH 4.51 was greater (62%) than larvae collected as eggs from a pond with pH 6.15 (46%) when both were exposed to pH 4.51. These results imply that larvae from the population breeding in the acidic pond were more tolerant of increased acidity than those from the population breeding in the less acidic pond.