Thermal adaptation of pelage in desert rodents balances cooling and insulation (Q6688753)

Phenotypic convergence across distantly related taxa can be driven by similar selective pressures from the environment or intrinsic constraints. The roles of these processes on physiological strategies, such as homeothermy, are poorly understood. We studied the evolution of thermal properties of mammalian pelage in a diverse community of rodents inhabiting the Mojave Desert, U.S.A. We used a heat flux device to measure the thermal insulation of museum specimens and determined whether thermal properties were associated with habitat preferences while assessing phylogenetic dependence. Species that prefer arid habitats exhibited significantly lower conductivity and thinner pelage relative to species with other habitat preferences. Despite having thinner pelage, the low conductivity imparted comparable insulation to species with other habitat preferences. Thus, arid species retain insulative pelage while simultaneously benefitting from thin pelage that promotes heat loss via convective cooling. We found no evidence of intrinsic constraints or phylogenetic dependence. Heat flux models designed to simulate body temperature regulation demonstrated that arid specialists saved 14.5% of their annual energy required for homeothermy by evolving lower conductivity, providing support for adaptive evolution of pelage. Our study indicates that selection for lower energetic requirements of homeothermy has shaped evolution of pelage thermal properties.