Thermal Tolerance in Ectothermic Species

Ectothermic organisms depend on environmental temperature to regulate physiological processes, making thermal tolerance a cornerstone of their ecology and evolution. Thermal tolerance defines the temperature range within which individuals maintain performance, growth and reproduction. This range is shaped by genetic adaptation, phenotypic plasticity and acclimation capacity, and can vary between life stages, populations and species. As global temperatures rise and heat extremes become more frequent, understanding how ectotherms adjust or fail to adjust to novel thermal regimes is crucial. Patterns of thermal tolerance influence species distributions, community dynamics and ecosystem functioning, and underpin forecasts of biodiversity responses to climate change. Interactions with other stressors, such as oxygen availability or moisture deficits, further modulate vulnerability. Recent advances integrate field measurements, laboratory assays and modelling to reveal trade‐offs between heat resistance and other life-history traits, and to identify evolutionary constraints on upper thermal limits. This knowledge informs conservation strategies, ranging from habitat management to assisted migration, and underlies climate impact assessments across marine, freshwater and terrestrial biomes.

Research from Nature Portfolio

Studies have demonstrated that closely related butterfly species differ in high-temperature performance, with one species showing superior growth-season traits and microclimate selection behaviours that enhance summer fitness, while the other exhibits greater overwintering success. These findings highlight seasonal specialisation as a driver of divergent population dynamics. Another investigation into arthropod thermal adaptation combined theory and data to reveal that shifts in peak performance temperatures for key life-history traits are constrained by trade-offs, limiting the rate at which populations can evolve heat tolerance. A global dataset of diverse species supports the prediction that juvenile development and adult fecundity respond hierarchically to warming, setting a framework for forecasting adaptive capacity. Foundational work on the evolution of thermal limits across thousands of species has shown that upper thermal tolerances are evolutionarily conserved, whereas cold limits are more evolutionarily labile, suggesting deep-time legacies influence present-day vulnerability to warming.

Thermal Tolerance in Ectothermic Species publication trend

The graph below shows the total number of articles in thermal tolerance in ectothermic species across all publications each year (not limited to Nature Index journals).

Technical terms

Ectotherm: An organism that relies on external heat sources to regulate body temperature and physiological functions.

Critical thermal limit: The upper or lower temperature beyond which an organism loses essential physiological function or dies.

Thermal performance curve: A graphical representation of an organism’s performance (e.g. growth, reproduction) across a range of temperatures.

Acclimation: Physiological adjustments made by an organism in response to sustained changes in ambient temperature, improving tolerance.

Phenotypic plasticity: The capacity of a genotype to produce different phenotypes under varying environmental conditions, including thermal regimes.

References

1. Seasonal specialization drives divergent population dynamics in two closely related butterflies. Nature Communications (2023).
2. Variation in temperature of peak trait performance constrains adaptation of arthropod populations to climatic warming. Nature Ecology & Evolution (2024).
3. The evolution of critical thermal limits of life on Earth. Nature Communications (2021).
4. Ecological debts induced by heat extremes. Trends in Ecology & Evolution (2024).
5. Long‐term forecast of thermal mortality with climate warming in riverine amphipods. Global Change Biology (2023).
6. Predicting climate change impacts on poikilotherms using physiologically guided species abundance models. Proceedings of the National Academy of Sciences of the United States of America (2023).