DISTRIBUTIONS OF POND-BREEDING ANURANS: AN OVERVIEW OF MECHANISMS

Abstract

Concern over the fate of amphibians has led to increasing attention on the mechanisms that underly their distribution. Among pond-breeding anurans, surveys have revealed that most species are restricted to a minority of ponds, but distributions can shift over time. The mechanisms for these patterns fall into two broad classes: variation in environmental attributes among ponds, and the impact of spatial context surrounding ponds. There is abundant evidence that embryonic and larval anurans are sensitive to variation in a large number of abiotic and biotic variables. In some cases these effects on performance have been linked to variation among natural ponds, and compelling evidence suggests that anuran distributions may be restricted by the action of local conditions. While these explanations are often discussed in terms of single variates (e.g., hydroperiod), field experiments suggest that elimination will often result from the joint action of multiple factors (e.g., low pH and high metal concentrations)....