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