Using the stress response along an elevational gradient to understand habitat suitability for the Southern gray-cheeked salamander, Plethodon metcalfi
Temperature and humidity are stressors that will likely change in severity with global warming. As a result, organisms may become physiologically restricted from habitats they previously inhabited. In a previous study of unmanipulated populations of terrestrial salamanders, increases in stress were observed at lower elevation sites. These low elevation sites were consistently warmer and drier compared to high elevation sites, suggesting a link between climate and stress responses. Elevated stress levels may indicate environmental pressures and single areas of concern for species range contractions. In western North Carolina, the southern grey-cheeked salamander, Plethodon metcalfi, is an abundant, lungless species of salamander that requires a narrow microhabitat. To examine the factors driving the observed variation from unmanipulated individuals , we conducted a reciprocal transplant of low, mid, and high elevation populations within the elevational range of the species. The influence of climate on physiology was measured through changes in body mass and stress levels. Background stress levels between treatments were measured using neutrophil to lymphocyte (N:L) ratios from blood samples.
Sites varied in temperature and elevation, while the salamander enclosures remained moist throughout the study. This suggests that any physiological changes observed were the effect of temperature and elevation. We observed an increase in N:L ratio variation and shifts in mass correlating with the changes in temperature across the elevational gradient of the field site. There were no significant differences seen in average N:L ratios between treatments, but the increase in variation of N:L ratios observed suggests an effect of climate on stress that deserves further study. We observed significant decreases in mass at low elevation sites that may be indicative of alteration in energy allocation regimes in response to climatic variables. Given the changes in mass and the increase in stress variation at low elevation sites, we conclude physiologically driven range contractions may occur in those areas as the climate continues to warm.