The Herpetological Journal

pp. 173-178
Authors: Smith, Geoffrey R. & Burgett, Amber A.

Abstract: Given its large geographic range and its ability to use a variety of aquatic systems, the tadpoles of American bullfrogs (Lithobates catesbeianus) are likely exposed to a variety of background anuran communities and anthropogenic stressors. To examine how changes in the environmental context affect American bullfrogs, we manipulated the presence and overall density of American toad (Anaxyrus americanus) and Gray treefrog (Hyla versicolor) tadpoles to alter the biotic environment, and manipulated nutrients (nitrate and phosphate) to alter the abiotic environment, mimicking the effects of agricultural run-off. At low background tadpole densities, enrichment had a positive effect on American bullfrog tadpole mass when the background tadpole community consisted of Gray treefrog tadpoles only, but had a negative effect when the community contained American toad tadpoles (either alone or with Gray treefrogs). The situation was reversed at high background tadpole densities. Nutrient enrichment decreased survivorship in American bullfrog tadpoles. Our results suggest that the wide variety of environmental contexts in which American bullfrog tadpoles are found throughout their native and non-native ranges are likely to affect their success.

Keywords: NITRATE, HYLA VERSICOLOR, PHOSPHATE, ANAXYRUS AMERICANUS, LITHOBATES CATESBEIANUS