Understanding how species’ thermal limits have evolved across the tree of life is central to predicting species’ responses to climate change. Here, using experimentally-derived estimates of thermal tolerance limits for over 2000 terrestrial and aquatic species, we show that most of the variation in thermal tolerance can be attributed to a combination of adaptation to current climatic extremes, and the existence of evolutionary ‘attractors’ that reflect either boundaries or optima in thermal tolerance limits. Our results also reveal deep-time climate legacies in ectotherms, whereby orders that originated in cold paleoclimates have presently lower cold tolerance limits than those with warm thermal ancestry. Conversely, heat tolerance appears unrelated to climate ancestry. Cold tolerance has evolved more quickly than heat tolerance in endotherms and ectotherms. If the past tempo of evolution for upper thermal limits continues, adaptive responses in thermal limits will have limited potential to rescue the large majority of species given the unprecedented rate of contemporary climate change.
Bibliografisk noteFunding Information:
This is a joint effort of the sWEEP working group supported by sDiv, the Synthesis Centre of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (DFG FZT 118, 02548816). We are indebted to the work of the hundreds of researchers who have published the results of their experiments on thermal limits for the wide array of taxa encompassed here. J.M.B was supported by a sDiv postdoctoral fellowship. I.M.-C. and M.A.O.-T. acknowledge funding by the Spanish Ministry of Science and Innovation (Grant PID2019-109711RJ-I00 to I.M.-C., Grant CGL2017-86926-P to M.Á. Rodríguez and Grant CGL2017-89820-P to M.A.O.-T.). J.M.S. acknowledges funding from the Natural Sciences and Engineering Council of Canada. P.C. acknowledges funding from the Natural Sciences and Engineering Council of Canada Discovery Grant Program (RGPIN-2020-05627) and he is member of the FRQ-NT network Québec-Océan.
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