Data from: Geographic variation of body size in new world anurans: energy and water in a balance

The validity of Bergmann's rule, perhaps the best known
ecogeographical rule, has been questioned for ectothermic species. Here,
we explore the interspecific version of the rule documenting body size
gradients for anurans across the whole New World and evaluating which
environmental variables best explain the observed patterns. We assembled a
dataset of body sizes for 2761 anuran species of the Western Hemisphere
and conducted assemblage-based and cross-species analyses that consider
the spatial and phylogenetic structure in the data. In accordance with
heat and water-related explanations for body size clines, we found a
consistent association of median body size and potential
evapotranspiration across the New World. A relevant role of water
availability also emerges, suggesting the joint importance of body size
for thermoregulation and hydroregulation in anurans. Anurans do not follow
a simple Bergmannian pattern of increasing size towards high latitudes.
Consistent with previous regional findings, our Hemisphere-wide analyses
detect that the geographic variation in anuran body sizes is highly
dependent on a trade-off between heat and water balance. The observed
size-climate relationships possibly emerge from the interplay between
thermoregulatory abilities and the benefits inherent to reduced
surface-to-volume ratios in larger species, which decrease the rates of
evaporative water loss and favour heat retention. Our results also show
how temperature becomes important for species that are directly in contact
with the substrate and water, like burrowing and terrestrial anurans,
while arboreal species exhibit a body size cline linked with potential
evapotranspiration.