Data from: Divergence of thermal physiological traits in terrestrial breeding frogs along a tropical elevational gradient

Critical thermal limits are thought to be correlated with the elevational
distribution of species living in tropical montane regions, but with upper
limits being relatively invariant compared to lower limits. To test this
hypothesis, we examined the variation of thermal physiological traits in a
group of terrestrial breeding frogs (Craugastoridae) distributed along a
tropical elevational gradient. We measured the critical thermal maximum
(CTmax; n = 22 species) and critical thermal minimum (CTmin; n = 14
species) of frogs captured between the Amazon floodplain (250 m asl) and
the high Andes (3800 m asl). After inferring a multi-locus species tree,
we conducted a phylogenetically informed test of whether body size, body
mass, and elevation contributed to the observed variation in CTmax and
CTmin along the gradient. We also tested whether CTmax and CTmin exhibit
different rates of change given that critical thermal limits (and their
plasticity) may have evolved differently in response to different
temperature constraints along the gradient. Variation of critical thermal
traits was significantly correlated with species’ elevational midpoint,
their maximum and minimum elevations, as well as the maximum air
temperature and the maximum operative temperature as measured across this
gradient. Both thermal limits showed substantial variation, but CTmin
exhibited relatively faster rates of change than CTmax, as observed in
other taxa. Nonetheless, our findings call for caution in assuming
inflexibility of upper thermal limits, and underscore the value of
collecting additional empirical data on species’ thermal physiology across
elevational gradients.