On the correlated evolution of ecological lifestyle and thermal tolerance

The breadth of thermal tolerance delineates the upper (CTmax/Tuc) and lower (CTmin/Tlc) temperatures relevant to survival and/or persistence of organisms, and it is a correlate of extinction risk under climate change. Theory suggests that tolerance breadth evolves with the range of environmental temperatures. For instance, a narrow tolerance breadth is classically observed in tropical vs temperate species, and tropical ectotherms may feature increased extinction risk under climate change due to the proximity of CTmax and mean environmental temperatures. Here, we underscore that an organism’s lifestyle influences the extent of thermal fluctuation in its environment. We predict that subterranean species feature a narrower thermal tolerance breadth than surface-dwelling species, as the former evolve under dampened thermal variance. Using thermal limits data, we test this hypothesis in reptiles, mammals, and arthropods. Subterranean species (n = 5 – 37 per taxon) featured reduced tolerance ..., , # Data from: On the correlated evolution of ecological lifestyle and thermal tolerance

#### Summary of study

A species thermal tolerance breadth (TTB) delineates the upper and lower temperatures (CTmax and CTmin for ectotherms and Tuc and Tlc for endotherms) that an organism can tolerate, thus TTB can be used as a correlate of extinction risk under climate change, as it reflects an organism's ability to cope with temperature extremes. Theory suggests TTB evolves with the range of environmental temperatures. Classically, a relatively narrow TTB is observed in tropical vs temperate species. As a result, tropical ectotherms may feature increased extinction risk under climate change due to the proximity of their upper thermal limits (CTmax) and mean environmental temperatures.

In this study, we underscore that an organism's lifestyle influences the extent of thermal fluctuation in its environment, and we predict that subterranean species have narrower TTBs than surface-dwelling species, ...,