Thermal Preference and Species Range in Mountaintop Salamanders and Their Widespread Competitors

Abstract

Temperature tolerance can be a critical factor in determining amphibian species range over both latitudinal and elevational gradients; however, range limits across latitudes and elevations are not always congruent. For some mountaintop endemic and widespread salamanders in the Southern Appalachians, elevational distributions suggest the hypothesis that mountaintop species should be more cold tolerant, whereas latitudinal patterns are consistent with the hypothesis that widespread species should be more cold tolerant or tolerate a wider range of temperatures. We tested these hypotheses with year-round surveys of two mountaintop endemic species, Big Levels salamanders (Plethodon sherando) and Peaks of Otter salamanders (Plethodon hubrichti), at high- and low-elevation sites where they overlap with the widespread Eastern Redback salamander (Plethodon cinereus). We fit hierarchical Bayesian models to salamander surface counts across natural variation in soil temperature and moisture to compare temperatures that maximized surface counts (“peak activity temperature”) and the range of temperatures at which each species was active (“activity window”). We found that P. sherando and P. cinereus showed similar peak activity temperatures in areas of overlap, though P. sherando had a wider activity window as compared to P. cinereus. For P. hubrichti, we found a similar to somewhat higher peak activity temperature compared to P. cinereus, though P. cinereus had a wider activity window. We found no consistent differences in responses to soil moisture across species pairs. Our results suggest that elevational zonation in salamanders can result from a variety of processes and may not always reflect differences in relative temperature preferences.