Does Stress Alter Competition Between Species and Thereby Affect Amphibian Communities in Aquatic and Terrestrial Habitats?

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Interactions among species, including competition, predation, and parasitism, can have important consequences for determining the structure of natural communities. Thus, factors that alter the strength of such interactions can have a variety of effects. The goal of this research is to examine how presence of an insecticide in aquatic systems can alter competitive interactions between two anuran species and thereby alter community composition. Factors that increase levels of stress on one species may alter the strength of the interaction and give one species an advantage over the other. Such changes could lead to local extirpation of the less competitive species. This hypothesis will be tested by rearing tadpoles in artificial ponds that simulate natural conditions. This will allow an evaluation of the separate and additive effects of competition and stress (caused by introduction of low-levels of an insecticide) on larval development and survival, and on subsequent growth and survival in the terrestrial environment. This research has broad implications for understanding how amphibians, and other animals, respond to habitat alterations that are caused by human activities (e.g. chemicals that enter aquatic systems from agricultural runoff). Amphibians have, as a group, experienced significant population declines in many parts of the world but a full understanding of factors that contribute to those declines is lacking. Results of this research may help explain at least some of those declines. By linking basic and applied ecology, this research will lead to a greater understanding of ecological processes that structure communities and provide better ways to manage and protect biological diversity.