Meeting Abstract

93-3  Saturday, Jan. 6 10:45 – 11:00  Constraints and trade-offs in endotherm thermal regulation: implications for climate adaptations BALK, MA*; BURGER, JR; FRISTOE, TS; KHALIQ, I; HOF, C; SMITH, FA; National Museum of Natural History; University of North Carolina; Washington University, St. Louis; Senckenberg Biodiversity and Climate Research Centre ; Senckenberg Biodiversity and Climate Research Centre ; University of New Mexico BalkM@si.edu

Surprisingly, the thermal tolerances of species often do not match the range of environmental temperatures experienced within in the geographic range. Although a variety of hypotheses have been proposed to link thermal physiology and the thermal niche, support for these relationships is not consistent between taxonomic groups. According to the Scholander-Irving model of thermal physiology, a trade-off between the upper (T_UC) and lower (T_LC) bounds of the thermal neutral zone is predicted for endotherms. Such a trade-off may explain the discordance between species’ thermal tolerance and their thermal environment. Here, we employ a dataset of 297 mammal and 134 non-migratory bird thermal physiology to test for the predicted trade-off as well as investigate its role in the mismatch between species’ thermal physiology and their thermal environment. We show that a trade-off does indeed exist between upper and lower thermal critical temperatures for the majority of mammals and birds. Further, we find that the trade-off is asymmetrical with an increase in T_UC corresponding to a disproportionate increase in T_LC. Additionally, the trade-off plays a significant role in the mismatch between species’ thermal tolerances and their thermal environment. Evidence of this trade-off means that strong physiological constraints limit adaptations to extreme environmental temperatures.