Collection of data
We identified published studies documenting the rate of change in whole-body measurements of the thermal tolerance of ectotherms in response to manipulation of ambient temperature (Supplementary Information). For most of the papers, data were presented in figure format only, usually as the mean tolerance of groups of individuals that had experienced the ‘new’ temperature for differing lengths of time prior to being measured for the chosen tolerance trait. We digitized such data using the WebPlotDigitizer (https://apps.automeris.io/wpd/). In addition to thermal tolerance data, we extracted information for the following variables: taxonomic class, species name, mean body mass of individuals used in the experiment, life stage (juvenile vs. adult), acclimation temperature, and type of thermal tolerance measure. For the latter variable, a range of different terms that describe behavioural responses to either high or low acute temperature exposure are employed in different studies, and are typically taxon-specific (e.g. knock-down, loss of equilibrium, paralysis and spasms, loss of righting response). All such endpoints were categorized as a behavioural response. Experiments using some measure of mortality (time until or temperature at which signs of death such as cessation of breath or heart beating occurs) were categorized as a mortality response. For experiments where body mass information was absent we used the following procedure to obtain such data. First, we searched for information on minimum and maximum adult body size (length or mass) for the species in question. If only data on body length were available, we searched for allometries between length and mass for that species, or for species within the same genus, and used these to convert body lengths to mass. We then calculated the mean of the minimum and maximum body mass values. If no data on minimum or maximum size was found, we searched for studies that presented body sizes of adult individuals during field surveys and used the mean of these. The following classes of ectotherms were represented in the data set: amphibians, reptiles, insects, thecostraca, turbellaria, osteichtyes and malacostraca. For simplicity the latter two will be referred to as fishes and crustaceans, respectively