Geographic range limits in salamanders: Interactions between physiological and behavioral systems

Understanding the relationship between species distributions and their underlying mechanisms is a major question in ecology and evolutionary biology. The mechanisms involved and the degree to which they affect distributions vary among and within species. Examining the diversity of these mechanisms through behavioral, physiological, and integrative approaches can further our knowledge of the evolution of such traits and the maintenance of biodiversity and geographic distributions. Many of these traits may be conserved after speciation, therefore examination should be thorough, involve many species, and incorporate a phylogenetic approach.;The salamanders in the genus Plethodon are an ideal system to test predictions about mechanisms limiting geographic distributions and permitting species coexistence. In the laboratory, they acclimate quickly and exhibit realistic behaviors, and have been important models for understanding biotic interactions in the field. Furthermore, they are particularly sensitive to abiotic conditions because of they are lungless and rely on cutaneous respiration, coupled with maintaining a fully terrestrial lifestyle.;Four experimental studies that examine the thermal sensitivity of behavior and physiology of species in the genus Plethodon are reported in my dissertation. First, I determined the thermal sensitivity of aggression between two sympatric species. Second, I examined how energy assimilation differs intraspecifically in respect to geographic gradients. Third, I explored energy assimilation at the population level between different color morphs of a polymorphic species. Lastly, I explored interspecifically how thermal metrics of energy assimilation are related to range size.;I found that aggression increased with increasing temperatures and that thermal sensitivity of aggression differed depending on species. Within a species, latitudinal gradients, but not elevational gradients, produced different thermal sensitivities. Within a single population, energy assimilation did not differ between color morphs. Lastly, I found that thermal optimum and thermal performance breadth were correlated with latitude and elevation among species of Plethodon..;The research that I have conducted has given valuable insight in to the physiology and behavior of a highly specious genus. The data within this dissertation should be most useful in other contexts, particularly the production of data intensive mechanistic models of species distributions.