Alex R. Gunderson, Michael E. Dillon and Jonathon H. Stillman

It has long been known that animals can physiologically adjust to changing temperatures (without evolutionary change), a process known as “thermal acclimation.” It is generally assumed that thermal acclimation is beneficial, but it has proven difficult to empirically demonstrate the benefits, if they exist, under natural conditions. This is a pressing issue given that human-driven climate change is causing environmental temperatures to rise across the globe, and acclimation has the potential to mitigate the effects.

We estimated the benefits of acclimation for the heat tolerance of 103 ectotherm populations (“cold-blooded” animals including reptiles, insects, and amphibians) by comparing overheating risk under natural thermal variability, assuming animals can acclimate, relative to overheating risk assuming that that they cannot acclimate. Our analyses combined experimentally measured heat tolerance plasticity for each population with decades of habitat temperatures measured at weather stations near each population.

We found that acclimation can reduce the overheating risk of ectotherm populations; however, we also found that the benefits of acclimation are “incomplete.” This means that as temperatures rise, plasticity cannot prevent the overheating risk of populations from increasing. Acclimation is therefore not a “silver bullet” that will allow animals to overcome the detrimental effects of global warming.

Image caption: Photo provided by authors.
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