Extensive Acclimation in Ectotherms Conceals Interspecific Variation in Thermal Tolerance Limits

Area of Science:

• Physiological Ecology
• Climate Change Biology
• Herpetology

Background:

• Species' thermal tolerance limits dictate their distribution and vulnerability to climate change.
• Previous meta-analyses on thermal tolerance often used inconsistent or insufficient acclimation periods.
• This limits understanding of acclimation's role in observed thermal limit variations.

Purpose of the Study:

• To detail the time-course of critical thermal minima acclimation in the tropical reptile Carlia longipes.
• To compare C. longipes' acclimation to published data from other reptiles.
• To assess how acclimation time influences observed interspecific differences in thermal limits.

Main Methods:

• Documented the time-course of complete acclimation of critical thermal minima in Carlia longipes.
• Quantified the duration and extent of acclimation in C. longipes.
• Compared C. longipes' acclimation response to meta-analyzed data from other reptile species.

Main Results:

• Carlia longipes achieved 95% acclimation of its lower critical thermal limit in 17 weeks, a decrease of 2.4°C.
• Wild populations of C. longipes did not exhibit this acclimation over winter.
• Other reptiles showed faster (95% in 7 weeks) and greater acclimation (average 6.1°C decrease), but data for longer acclimation times are limited.

Conclusions:

• Acclimation responses can be slow and substantial, even in tropical ectotherms.
• Interspecific variation in acclimation speed and extent can obscure true thermal tolerance trends in meta-analyses.
• Controlled, lengthy acclimation is crucial for accurate physiological comparisons, as intermediate states underestimate true capacities.