When water meets temperature: ecological and evolutionary implications of thermo-hydroregulation

The regulation of body temperature (thermoregulation) and water balance (hydroregulation) are key processes underlying ecological and evolutionary responses to climatic conditions in animal populations. Despite a long standing tradition of biophysical models of joint water and temperature regulation, the ecological and evolutionary implications of thermoregulation and hydroregulation have so far mostly been studied independently. In terrestrial or semi-terrestrial animals, thermoregulation and hydroregulation however closely interact and combined temperature and water constraints should directly influence individual performances. We emphasize the unifying concept of thermo-hydroregulation to address the functional integration of body temperature and water balance regulation. This concept refines our mechanistic understanding of the physiological and behavioral flexibility of animals in a changing world dominated by concurrent trends in temperature and water availability. This integrative approach has implications on a range of ecological and evolutionary processes such as space use and dispersal, resource-based trade-offs and optimal life history tactics.