The occurrence of facultative paedomorphosis in urodeles has been attributed to both abiotic and biotic conditions in a variety of species, with a few researches supporting one or both of these effects. However, no previous study has determined the evolutionary consequences of paedomorphic individuals in terms of lifetime reproductive success. Determining the reproductive costs and benefits of paedomorphosis is important to understand the evolution of complex life cycles such as amphibian metamorphosis. In addition, the environmental causes of paedomorphosis in the proposed study organism, Ambystoma tigrinum nebulsum, are unknown. The goal of the proposed research is to determine the evolutionary consequences and environmental correlates of paedomorphosis in a high-elevation population of this species. I will investigate environmental effects on morph type (metamorph or paedomorph) as well as growth rate, survival, and population density by mark and recapture census and measuring several abiotic and biotic variables. By observing breeding behavior under both natural and experimental conditions, I will determine the frequency of interbreeding and male-male competition/mate choice within and between morphs, as well as determine if morphs differ in reproductive success. The influence of larval density on offspring morph type will be determined by rearing offspring at three densities.
