Perturbation experiments have become an important tool of community ecologists trying to understand what factors determine the distribution and abundance of species. Biotic perturbations, such as the introduction of new species into communities, are of particular interest. How a community responds to a new species and how that species integrates itself into the existing framework of interactions are especially useful in inferring mechanisms of community organization. Predation and competition are important interactions within streamside salamander communities. These commnunities are partially sympatric with a large predatory fish, the brook trout, providing a biotic perturbation relevant to natural distributions. Predation and competition are important interactions within this salamander community. Impact of trout likely involves both predation and competition and may affect the community via direct and indirect effects. Community organization, species interactions and responses to brook trout will be studied using three approaches. Natural experiments will provide data on the effects of long-term co-occurrence. Replicated field experiments allow rigorous testing of the hypothesis that brook trout affect community organization in streamside salamanders. Factorial experiments in an array of artificial streams will determine the nature and relative importance of interactions.
