Acclimatization of skin resistance to water loss within a lungless salamander: Implications for activity
In response to climate change, organisms can tolerate the new environment, emigrate, or acclimatize. When emigration is not possible, survival may depend on their capacity to acclimatize by modifying physiology in ways that increase the potential duration for foraging and mating activities. Here, I investigated how salamanders acclimatize to environmental cues by modifying physiological traits that have the potential to influence their fitness. Hydration state limits foraging activity of salamanders; therefore, salamanders that can increase skin resistance to water loss (Rs) might increase potential time for activity and offset energetic costs associated with harsh environments. I leveraged the natural variation of temperature and humidity along an elevational gradient to test variation of Rs within the Southern gray-cheeked salamander (Plethodon metcalfi). To test the capacity to acclimatize, I then conducted a reciprocal transplant along an elevational gradient to measure if variation was due to plasticity or local adaptation. To measure Rs, I used an advanced flow through system capable of controlling humidities and measuring changes in water vapor pressure. I also calculated changes in potential activity due to acclimatization under environmental conditions that salamanders experience in nature.
The results suggested that salamanders use temperature and humidity as cues to increase Rs. In the laboratory, Rs remained constant at cool temperatures, but under warm temperatures, Rs increased as air became dry. Similarly, there was a negative correlation between Rs and the elevation at which the individual was captured. Because low elevations were typically warmer and drier than high elevations, the results suggest that salamanders may use temperature as a cue for a drier environment. The reciprocal transplant experiment demonstrated that salamanders responded similarly to environmental conditions regardless of the elevational at which they were captured. These responses also influence potential activity throughout their elevational range. Specifically, the higher values of Rs at low elevations result in a doubling of potential activity time at low elevations. Together, these results suggest that salamanders within this population can acclimatize by increasing Rs in response to their environment. Considering acclimatization might improve our understanding of the capacity of organisms to respond to climate change. Future research will focus on incorporating acclimatization into mechanistic species distribution models to predict the effects of climate change on the distribution and abundance of salamander populations.