Geographic Variation in Acid Tolerance of Connecticut Wood Frogs

Abstract

Acid waters are often toxic to amphibians, but the ability of these animals to survive in acidic conditions varies considerably within and among species. We examined geographic variation in the acid tolerance of wood frog (Rana sylvatica) embryos and larvae from eight ponds in Connecticut, which differed in their levels of acidity. Embryos produced by adult frogs from the different ponds varied significantly in the ability to hatch in acidic solutions. Hatching success of the embryos was not correlated with the acid levels in the ponds. Tadpole survival in low pH solutions also differed among the ponds, and acid tolerance of tadpoles was correlated with pond pH (tadpoles produced by adults from acidic ponds tended to be more acid tolerant). Results of genetic crosses among frogs from different ponds suggested that the geograhic differences in acid tolerances of embryos are not genetically determined, but population differences in the tolerance of tadpoles to acidity appear to have some genetic basis.