Trait interactions and compensatory response to multiple stressors: comparing amphibian populations across an elevation gradient.
Garcia, Tiffany*,1, Paoletti, David1, Blaustein, Andrew1, 1 Oregon State University, Corvallis, OR
ABSTRACT- Larval amphibians inhabiting complex aquatic habitats often face multiple dangers simultaneously. When multiple environmental stressors are present, individuals can mediate potential conflicts by relying on coupled responses from both behavioral and physiological traits. Ultraviolet-B (UV-B) radiation and predation risk can cause changes in amphibian body coloration and behavior. Interactions between body color and behavior in response to these stressors may vary across species and population (i.e. elevation and corresponding UV-B exposure rates). We quantified activity rate and color change in two amphibian species from high and low elevation populations: the Pacific Treefrog (Hyla regilla) and the Long-toed Salamander (Ambystoma macrodactylum). We exposed larval individuals to predator chemical cues (Taricha granulose) and naturally relevant levels of UV-B radiation for six days. Significant species and population differences were found. Low elevation Hyla regilla individuals mediated stress by coupling decreased activity rates to reduce predation risk with dark body coloration to reduce UV-B damage. High elevation Hyla individuals showed no response UV-B, but decreased activity in response to predation risk. Low elevation Ambystoma macrodactylum individuals also coupled color and behavior by adopting cryptic coloration when predation risk was present and decreasing activity in response to UV-B. Individuals from high elevation Ambystoma populations showed no specific color response to either stress, but increased activity in the presence of predation risk. Species and population differences in trait interaction strategies may be due to differences in the strength of selection across habitats. Individuals from low elevation populations respond to both stressors with a coupled color and behavior strategy, effectively decreasing risk. High elevation populations respond differently, showing no color or behavior response to UV-B and only utilizing activity defenses against predation risk.
Key words: trait interactions, amphibians, predation risk
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