Life history variation along an elevational gradient in Plethodon montanus: implications for conservation

Abstract

Climate change represents a significant threat to amphibians, which are already imperiled. However, for many species, the relationship between demographic vital rates (survival and growth) and climate is unknown, which limits predictive models. Here we describe the life history variation of Plethodon montanus using capture-recapture data over a period of four years, at five sites along an elevational gradient to determine how survival and growth vary with temperature, precipitation, and how these relationships vary with elevation. We used a hierarchical model to estimate asymptotic size and growth rate, and used a spatial Cormack-Jolly-Seber model to estimate probability of capture and survival, as well as dispersal variance. Our results show that during the active season, growth and survival rates are both positively affected by precipitation, while survival was positively affected by temperature at all elevations, the relationship between growth rates and temperature varied along the elevational gradient. Generally at lower elevations, higher temperatures led to a decrease in growth while at higher elevations the opposite was true. During the inactive season we found elevational variation in the relationship between survival and the amount of snow; at low elevations snowfall was low but survival decreased with increasing snowfall while at higher elevations increasing snowfall lead to higher survival. Our results demonstrate that understanding how the environment can affect salamander demography to develop mechanistic models, will require knowledge of the actual environmental conditions experienced by a given population as well as an understanding of the overall differences in climate at a given site.