EFFECTS OF ACIDITY ON THE REPRODUCTIVE SUCCESS AND BREEDING SITE SELECTION OF TWO AMPHIBIANS.

S.E. Turner and A.M. Turner. Department of Biology, Clarion University of Pennsylvania, Clarion, PA 16214

The effects of acid deposition on aquatic ecosystems are especially acute in the Allegheny Plateau of Western Pennsylvania. We studied breeding site selection and reproductive success of the spotted salamander, Ambystoma maculatum, and the wood frog, Rana sylvatica, breeding in woodland ponds. Pond pH ranged from 3.8 to 6.2. For spotted salamander eggs, we found that hatching success was greater than 90% in ponds with a pH of greater than 4.8, and less than 15% in ponds with a pH of less than 4.8. Analysis of the characteristics of breeding sites chosen by wood frogs and spotted salamanders showed little evidence for site discrimination based on measured physical and chemical variables. In particular, the median pH of breeding ponds was similar to non-breeding ponds for both spotted salamanders and wood frogs. Taken together, these data show that although wood frogs and spotted salamanders are fairly tolerant of acidity, ponds with very low pH are common and may function as ecological traps for breeding amphibians.