Scripts used in R from Testing the metabolic homeostasis hypothesis in amphibians.

A number of hypotheses about compensatory mechanisms that allow ectothermic animals to cope with the latitudinal decrease in ambient temperature (<i>T</i>_A) have been proposed during the last century. One of these hypotheses, the ‘metabolic homeostasis’ hypothesis (MHH), states that species should show the highest thermal sensitivity of the metabolic rate (<i>Q</i>_10-SMR) at the colder end of the range of <i>T</i>_As they usually experience in nature. This way, species should be able to minimize maintenance costs during the colder hours of the day, but quickly take advantage of increases in <i>T</i>_A during the warmer parts of the day. Here, we created a dataset that includes <i>Q</i>_10-SMR values for 58 amphibian species, assessed at four thermal ranges, to evaluate three predictions derived from the MHH. In line with this hypothesis, we found that: (i) <i>Q</i>_10-SMR values tended to be positively correlated with latitude when measured at lower <i>T</i>_As, but negative correlated with latitude when measured at higher <i>T</i>_As, (ii) <i>Q</i>_10-SMR measured at lower <i>T</i>_As were higher in temperate species, whereas <i>Q</i>_10-SMR measured at higher <i>T</i>_As were higher in tropical species, and (iii) the experimental <i>T</i>_A at which <i>Q</i>_10-SMR was maximal for each species decreased with latitude. This is the first study to our knowledge showing that the relationship between <i>Q</i>_10-SMR and latitude in ectotherms changes with the <i>T</i>_A at which <i>Q</i>_10-SMR is assessed, as predicted from an adaptive hypothesis.This article is part of the theme issue ‘Physiological diversity and global patterns of biodiversity in a time of global climate change: testing and generating key hypotheses involving temperature and oxygen’.