Predicting the physiological performance of ectotherms in fluctuating thermal environments

Area of Science:

• Physiological ecology
• Climate change biology
• Developmental biology

Background:

• Organismal plasticity is crucial for survival in variable environments.
• Climate change exacerbates thermal variability, impacting developing organisms.
• Few studies assess fluctuating environments' effects on performance or validate predictive frameworks.

Purpose of the Study:

• To test if constant temperature reaction norms predict embryonic and larval anuran performance in fluctuating temperatures.
• To investigate the influence of stress and acclimation on performance predictability in variable thermal conditions.
• To compare predictions with empirical data for striped marsh frogs (Limnodynastes peronii).

Main Methods:

• Measured embryonic and larval performance of striped marsh frogs at constant temperatures (18, 22, 26, 30, 34°C).
• Developed empirical models based on constant temperature data.
• Predicted performance at fluctuating temperatures (18-28°C and 18-34°C) and compared with observed performance.

Main Results:

• Models based on constant temperatures poorly predicted performance in fluctuating thermal environments.
• Growth and development were faster in variable conditions than predicted, suggesting benefits of acute extreme temperature exposures.
• Performance predictability was higher in less variable thermal environments, aligning with theoretical expectations.

Conclusions:

• Extrapolation from constant temperature studies can lead to inaccurate conclusions about organismal performance in fluctuating environments.
• Naturalistic thermal conditions are essential for accurately assessing thermal plasticity and informing life-history evolution models.
• Understanding physiological responses to thermal variability is critical for predicting species' responses to climate change.