Determining critical periods for thermal acclimatisation using a distributed lag non-linear modelling approach

Area of Science:

• Environmental physiology
• Ecology
• Climate change biology

Background:

• Global climate change causes rapid thermal shifts, threatening species survival.
• Thermal acclimatisation can mitigate climate change impacts, but its temporal dynamics in natural settings are poorly understood.
• Laboratory studies often fail to capture the natural environmental variability influencing acclimatisation.

Purpose of the Study:

• To investigate how the timing and magnitude of past thermal exposures influence thermal tolerance in natural environments.
• To apply a novel modelling approach to field data for a deeper understanding of thermal acclimatisation dynamics.

Main Methods:

• Utilised field data from two Scottish freshwater Ephemeroptera species.
• Employed a distributed lag non-linear model (DLNM) to analyse the influence of past thermal exposures on thermal tolerance.
• Assessed the impact of temperature change timing (hours to days vs. weeks) and magnitude on acclimatisation.

Main Results:

• Rapid heat hardening effects were observed, correlating with high rates of temperature change over hours to days.
• Temperature change magnitude influenced acclimatisation over weeks, but not short-term responses.
• Evidence suggests de-acclimatisation of heat tolerance occurs in response to cooler environments.

Conclusions:

• Novel insights into the temporal dynamics of thermal acclimatisation in natural environments were provided.
• The distributed lag non-linear model (DLNM) is a powerful tool for studying thermal physiology in the wild.
• Recommendations for improved laboratory experiment design based on field data insights were made.