Temperature variability and metabolic adaptation in terrestrial and aquatic ectotherms

• Published in: Journal of thermal biology 2023-07, Vol.115, p.103565-103565, Article 103565
• Main Authors: Carter, Mauricio J., Cortes, Pablo A., Rezende, Enrico L.
• Format: Article
• Language: English
• Subjects: Global distribution; Metabolic rates; Temperature variability; Thermal adaptation; Thermodynamics
• ISSN: 0306-4565
• DOI: 10.1016/j.jtherbio.2023.103565

Thermodynamics is a major factor determining rates of energy expenditure, rates of biochemical dynamics, and ultimately the biological and ecological processes linked with resilience to global warming in ectothermic organisms. Nonetheless, whether ectothermic organisms exhibit general adaptive metabolic responses to cope with worldwide variation in thermal conditions has remained as an open question. Here we combine a model comparison approach with a global dataset of standard metabolic rates (SMR), including 1,160 measurements across 788 species of aquatic invertebrates, insects, fishes, amphibians and reptiles, to investigate the association between metabolic rates and environmental temperatures in their respective habitats. Our analyses suggest that variation in SMR after removing allometric and thermodynamic effects is best explained by the temperature range encountered across seasons, which always provided a better fit than the average temperature for the hottest and coldest month and mean annual temperatures. This pattern was consistent across taxonomic groups and robust to sensitivity analyses. Nonetheless, aquatic and terrestrial lineages responded differently to seasonality, with SMR declining – 6.8% °C−1 of thermal range across seasons in aquatic organisms and increasing 2.8% °C−1 in terrestrial organisms. These responses may reflect alternative strategies to mitigate the impact of increments in warmer temperatures on energy expenditure, either by means of metabolic reduction in thermally homogeneous water bodies or effective behavioral thermoregulation to exploit temperature heterogeneity on land. •Energy turnover rates in ectothermic organisms are sensitive to environmental temperatures, yet it remains unclear how different lineages adapt to contrasting thermal environments.•We studied how metabolism varies geographically across ectotherms taxa, providing evidence of adaptation to temperature variability across ectothermic lineages.•Whereas terrestrial organisms exhibit elevated metabolic rates to take advantage of environmental heterogeneity in temperatures, aquatic organisms adopt a strategy of metabolic reduction to save energy during warm seasons.