Thermal adaptation revisited: How conserved are thermal traits of reptiles and amphibians?

• Published in: Journal of experimental zoology. Part A, Ecological and integrative physiology Ecological and integrative physiology, 2021-01, Vol.335 (1), p.173-194
• Main Authors: Bodensteiner, Brooke L., Agudelo‐Cantero, Gustavo A., Arietta, A. Z. Andis, Gunderson, Alex R., Muñoz, Martha M., Refsnider, Jeanine M., Gangloff, Eric J.
• Format: Article
• Language: English
• Subjects: amphibians; climate change; conservatism; evolution; plasticity; reptiles; thermal physiology
• ISSN: 2471-5638; 2471-5646
• DOI: 10.1002/jez.2414

Ectothermic animals, such as amphibians and reptiles, are particularly sensitive to rapidly warming global temperatures. One response in these organisms may be to evolve aspects of their thermal physiology. If this response is adaptive and can occur on the appropriate time scale, it may facilitate population or species persistence in the changed environments. However, thermal physiological traits have classically been thought to evolve too slowly to keep pace with environmental change in longer‐lived vertebrates. Even as empirical work of the mid‐20th century offers mixed support for conservatism in thermal physiological traits, the generalization of low evolutionary potential in thermal traits is commonly invoked. Here, we revisit this hypothesis to better understand the mechanisms guiding the timing and patterns of physiological evolution. Characterizing the potential interactions among evolution, plasticity, behavior, and ontogenetic shifts in thermal physiology is critical for accurate prediction of how organisms will respond to our rapidly warming world. Recent work provides evidence that thermal physiological traits are not as evolutionarily rigid as once believed, with many examples of divergence in several aspects of thermal physiology at multiple phylogenetic scales. However, slow rates of evolution are often still observed, particularly at the warm end of the thermal performance curve. Furthermore, the context‐specificity of many responses makes broad generalizations about the potential evolvability of traits tenuous. We outline potential factors and considerations that require closer scrutiny to understand and predict reptile and amphibian evolutionary responses to climate change, particularly regarding the underlying genetic architecture facilitating or limiting thermal evolution. Selection on thermal traits acts across life‐history stages in reptiles and amphibians, with fitness influenced by performance consequences of these sequential responses. However, the degree of physiological evolution will be dependent on various evolutionary constraints, such as shared physiological pathways and genetic architecture. Research Highlights Here, we review how interactions among evolution, plasticity, behavior, and ontogeny shape thermal physiological traits in reptiles and amphibians, finding that these traits are not as evolutionarily rigid as once believed across phylogenetic scales.