Species Habitat Specificity Impacts the Thermosensitivity of Evaporative Water Loss in Sympatric Rattlesnakes.

Maintaining water balance is critical for organismal survival. For many species, evaporative water loss comprises the majority of total water loss, and evaporative water loss is strongly influenced by temperature. Evaporative water loss can vary considerably among species and has been shown to be influenced by habitat aridity and species distribution. Therefore, species with distributions encompassing higher or more variable temperatures may have adapted to reduce the temperature sensitivity of evaporative water loss, yet variation in temperature sensitivity of evaporative water loss remains poorly understood. Accordingly, we investigated impacts of temperature on evaporative water loss in four sympatric species of Sonoran Desert rattlesnakes with varying species distributions and extent of aridity tolerance. While evaporative water loss was positively correlated with temperature in all species, higher temperatures differentially impacted evaporative water loss. At the highest temperature, the species with the broadest distribution in terms of both range and habitat variability had significantly higher evaporative water loss than the other populations, and the species with a distribution mostly limited to more arid climates was less sensitive to moderate temperature changes than were the other species. Overall, our study demonstrates that evaporative water loss in sympatric, closely related congeners can be differentially impacted by temperature. Our results contribute knowledge regarding how arid-adapted species may thrive in xeric conditions and lend insight into how warming and drying conditions may differentially impact species.