Large-scale evolution of body temperatures in land vertebrates

Abstract

Body temperature is a crucial variable in animals that affects nearly every aspect of their lives. Here we analyze for the first time largescale patterns in the evolution of body temperatures across terrestrial vertebrates (tetrapods: including amphibians, mammals, birds and other reptiles). Despite the traditional view that endotherms (birds and mammals) have higher body temperatures than ectotherms, we find they are not significantly different. However, rates of body‐temperature evolution are significantly different, with lower rates in endotherms than ectotherms, and the highest rates in amphibians. We find that body temperatures show strong phylogenetic signal and conservatism over 350 million years of evolutionary history in tetrapods, and some lineages appear to have retained similar body temperatures over time for hundreds of millions of years. Although body temperatures are often unrelated to climate in tetrapods, we find that body temperatures are significantly related to day‐night activity patterns. Specifically, body temperatures are generally higher in diurnal species than nocturnal species, both across ectotherms and, surprisingly, across endotherms also. Overall, our results suggest that body temperatures are significantly linked to phylogeny and diel‐activity patterns within and among tetrapod groups, rather than just climate and the endotherm‐ectotherm divide.

Evolution of diel activity patterns in skinks (Squamata: Scincidae), the world's second‐largest family of terrestrial vertebrates

“…Vidan et al (2017) have shown that nocturnal reptiles are absent from the coldest regions in Eurasia. The body temperatures of nocturnal and cathemeral reptiles are correlated with ambient temperatures, whereas those of diurnal species are not (Meiri et al 2013), and nocturnal species generally have lower body temperatures than diurnal species (Meiri et al 2013;Moreira et al 2021). These observations suggest that low ambient temperatures may serve as a filter for the presence of nocturnal ectotherms.…”

“…2013; Moreira et al. 2021). These observations suggest that low ambient temperatures may serve as a filter for the presence of nocturnal ectotherms.…”

The Bogert effect, a factor in evolution

“…Activity temperatures, they found, did not simply correlate with the local thermal environment, and desert lizards were not exceptionally warm adapted (which had been a common viewpoint; e.g., Hesse et al 1937). Rather, the most distinguishing thermal factor among species was diel activity, with diurnal species exhibiting higher activity temperatures than their nocturnal counterparts (a pattern that still holds true; e.g., Meiri et al 2013;Moreira et al 2021). This study by Cowles and Bogert (1944) established a clear role for thermoregulation as a key mitigating factor for reptile thermal relations, which disrupted long-standing dogma that reptiles were consummately "cold-blooded" and lacked the ability to regulate their core temperature (e.g., Agassiz and Gould 1856).…”

Gut microbiome–immune system interaction in reptiles

“…Forthcoming studies are warranted to determine the core gut microbiome of the reptilian species. For instance, from the 26 species of extant crocodilians (Moreira et al, 2021), analyses of microbiome have merely been accomplished in the alligator and salt water crocodile (Keenan et al, 2013; Willson et al, 2019). Given that these species are so resilient, as well as long‐lived and display limited cellular senescence (Jones et al, 2014), studies to comprehend how their gut microbiome is connected with these attributes are necessary.…”