Understanding what drives changes in species spatial distributions is a critical theme in ecology, especially because climate and landscape changes are expected to lead to rapid changes in distributional patterns at large scales. Amphibians are of particular interest because they are presumed to be sensitive to habitat change, and have limited dispersal capabilities when compared with other animals. Many amphibians have a complex life cycle, wherein a population requires both terrestrial habitat for juvenile and adult growth and survival, and aquatic habitat for reproduction. Turnover is a natural component of amphibian populations from deterministic processes is of key concern in understanding the causes of amphibian population declines. Directional changes in the landscape may alter habitat suitability for amphibians, leading to changes in community composition over time. Landscape characteristics influence patterns of wetland occupancy, and terrestrial habitat features are often at least as important as wetland characteristics in predicting amphibian habitat occupancy and turnover.
Results/Conclusions The data confirmed our expectation that the successional landscape of Mount St Helens led to differences in amphibian species occupancy dynamics. We found species-specific responses to the different landscapes, which we predicted based on each species life history characteristics. Mount St. Helens is a unique place to ask questions about the factors controlling the distribution and abundance of species, and our analysis of 10yr of occupancy data confirm that the landscape in which a set of breeding habitats are embedded exerts a primary control on the occupancy dynamics of wetland-breeding amphibians. Our study represents an investigation of the spatial dynamics of amphibian communities in early successional landscapes, and we find that the features of the landscape, including the successional state and the spacing of wetlands, underlie the occupancy dynamics of breeding amphibians.