Genetic Variation in Tolerance of Amphibians to Low pH

Observations of within-species variation in acid sensitivity have prompted speculation that genetic variation exists in the response of amphibians to low pH conditions. Study of embryonic acid tolerance in the wood frog, Rana sylvatica, suggests that variation in hatching success at low pH is largely influenced by maternal factors, which may or may not be genetic. There is limited evidence that direct genetic factors influence differences in acid tolerance of embryos. Data from other species are largely consistent with these findings. Among wood frog larvae, there was no evidence of a maternal influence on survival time at low pH, but direct genetic variation was present. At low pH, growth rates of amphibian larvae are inhibited. Many studies indicate that significant genetic variation exists in larval growth rates at neutral pH. Results of a preliminary study of chorus frogs indicate that variation in larval growth at low pH is also influenced by genetic factors.