| The movement of individuals can be a critical component to many ecological and evolutionary processes. The evolution of dispersal is often driven by the balance between the costs related to dispersal (e.g. mortality risk, energy and time), and the potential benefits (e.g. competition avoidance, colonization of new habitats, and most critically, species persistence in human dominated and fragmented landscapes). Regardless of the long-standing recognition of the ecological and evolutionary significance of dispersal, a broader understanding of variation in factors influencing dispersal is necessary in order to develop a comprehensive theory explaining the evolution of dispersal strategies. Understanding the factors and accompanied challenges to dispersal is critical in the face of increased habitat fragmentation as a consequence of anthropogenic development and climate change.;I conducted a spatially explicit mark-recapture study to better understand and identify various mechanisms, both extrinsic and intrinsic to the organism, that influence dispersal in order to make population level inferences about dispersal in the stream salamander, Desmognathus brimleyorum. First, I measured aspects of habitat quality and salamander population density to test hypotheses about the extrinsic factors promoting emigration. Second, I explored whether traits intrinsic to the organism (e.g., body size, age class, growth rate) were associated with the probability of dispersal.;Emigration is a consequence of population density. Within this population there is little variation in habitat structure across the stream and as a result there seems to be little relationship between emigration and habitat quality. However, when examining specific factors used to quantify habitat quality such as substrate type there were significant relationships between emigration and substrate type, suggesting that distribution and dispersal could be influenced by reach-scale habitat, specifically the size-distribution and availability of interstitial spaces.;When examining intrinsic factors influencing dispersal I found that both growth rate and individual size has an effect on dispersal characteristics across age classes. There were significant relationships between size and growth rate of juveniles and dispersal suggesting that there are associated trade-offs for dispersing juveniles. Additionally, the consequences of dispersal for females was counter to that for juveniles suggesting that adult females benefit from dispersing. Together, both local habitat variation and salamander density (and associated costs of competition) appear to regulate dispersal decisions in females. Dispersal in juveniles; however, appears more complex and resolution will require further study and a more complete understanding of how dispersal influences salamander fitness (i.e., survival). |
