Data from: Scaling of thermal tolerance with body mass and genome size in ectotherms: a comparison between water-and air-breathers

Global warming appears to favour smaller-bodied organisms, but whether
larger species are also more vulnerable to thermal extremes, as suggested
for past mass-extinction events, is still an open question. Here, we
tested whether interspecific differences in thermal tolerance (heat and
cold) of ectotherm organisms are linked to differences in their body mass
and genome size (as a proxy for cell size). Since the vulnerability of
larger, aquatic taxa to warming has been attributed to the oxygen
limitation hypothesis, we also assessed how body mass and genome size
modulate thermal tolerance in species with contrasting breathing modes,
habitats and life stages. A database with the upper (CTmax) and lower
(CTmin) critical thermal limits and their methodological aspects was
assembled comprising more than 500 species of ectotherms. Our results
demonstrate that thermal tolerance in ectotherms is dependent on body mass
and genome size and these relationships became especially evident in
prolonged experimental trials where energy efficiency gains importance.
During long-term trials, CTmax was impaired in larger-bodied
water-breathers, consistent with a role for oxygen limitation. Variation
in CTmin was mostly explained by the combined effects of body mass and
genome size and it was enhanced in larger-celled, air-breathing species
during long-term trials, consistent with a role for depolarization of cell
membranes. Our results also highlight the importance of accounting for
phylogeny and exposure duration. Especially when considering long-term
trials, the observed effects on thermal limits are more in line with the
warming-induced reduction in body mass observed during long-term rearing
experiments.