Competition at the range boundary in the slimy salamander: using reciprocal transplants for studies on the role of biotic interactions in spatial distributions.

1. Determining the factors that influence the distribution of species has been a longstanding goal in the field of ecology. New techniques such as ecological niche modelling have the potential to aid in addressing many broad questions in ecology, evolutionary biology, and behavioural ecology. 2. This study combines broad-scale ecological niche models with fine-scaled studies of biotic interactions to examine how abiotic and biotic interactions affect the spatial distribution of the terrestrial salamander species Plethodon glutinosus (northern slimy salamander), in a potential contact zone shared with Plethodon mississippi (Mississippi slimy salamander). 3. The core habitat in the interior portion of the range of P. glutinosus and the contact zone are distributed in unique environmental niche space. 4. The form of competition, inter- or intraspecific, significantly affected mass loss of adult salamanders. Salamanders lost more mass when interacting with a heterospecific. 5. Abiotic conditions strongly influenced the impact of competition on salamanders. Under stressful environmental conditions at the field site located in the contact zone, salamanders lost more mass than at the field site located in the interior of the range. 6. Furthermore, adult salamanders from range-edge populations and core populations (from the interior of the range) differed in their respective abilities to compete under the abiotic conditions in the contact zone.