Invasion Complexities: The Diverse Impacts of Nonnative Species on Amphibians

Since the first documented declines of amphibian species, researchers have learned how nonnative species can depress amphibian populations and lead to local extinctions. Here, we explore the dimensions of invasions in the context of evolutionary history, anthropogenic disturbance, and climate change. Recent studies indicate that the nonnative groups that have most negatively affected amphibians are plants, fishes, and other amphibians. We review current work aimed at determining the direct and indirect effects of nonnative species on amphibian health, genotypes, and native ecosystem structure, as well as research examining invasions from a community level perspective. We also describe synergistic effects between abiotic, biotic, and nonnative factors. Recent studies have documented the intricacies of invasions and how numerous aspects of invasions can interact additively and complementarily to the detriment of the native ecosystem. Understanding the complexity of invasions means considering if and how biological, environmental, and ecological processes within ecosystems are being reshaped as a result of introduced species. Assessing the ecology and ecosystem dynamics of invasions at multiple levels, from the genome to the ecosystem, is paramount to the conservation, restoration, and future research of invaded amphibian ecosystems.