Novel physiological data needed for progress in global change ecology

Abstract

Studies examining the underlying causes of the distributions of species and their future trajectories under climate change have benefitted from the accumulation of measurements of thermal tolerance across the tree of life. However, gaps in the global coverage of heat-tolerance data for ectotherms persist on four critical fronts. First, most large-scale analyses treat heat tolerance as a fixed species trait despite that population-level variation can equal or exceed cross-species variation. Second, terrestrial non-arthropod invertebrates and aquatic ectotherms other than bony fish have been poorly sampled, particularly in boreal and tropical regions, the Indian Ocean and the mesopelagic-deep ocean. Third, the study of climate impacts on the heat tolerance of terrestrial ectotherms has often neglected the interaction of environmental temperatures with water availability. And fourth, the mechanisms driving the dependence of heat tolerance on oxygen supply-demand remain largely unknown. We contend that filling those data and knowledge gaps requires novel strategies for the ecophysiological sampling of the range of understudied populations and species that occupy the length of climatic gradients globally. Such developments are essential for comprehensively predicting species responses to climate change across aquatic and terrestrial biomes.