Among- and Within-Individual Variance in Metabolic Thermal Reaction Norms

Area of Science:

• Physiology
• Ecology
• Evolutionary Biology

Background:

• Temperature significantly impacts metabolic rate (MR) in ectotherms.
• Understanding variation in thermal sensitivity of MR is key for predicting evolutionary adaptation.

Purpose of the Study:

• To quantify the repeatability of metabolic thermal sensitivity among individual Drosophila melanogaster.
• To investigate the relationship between average MR and thermal sensitivity within individuals.

Main Methods:

• Repeated overnight measurements of MR at two temperatures (~24°C and ~27°C) in adult male fruit flies.
• Statistical analysis accounting for age, body mass, and locomotor activity.

Main Results:

• Significant repeatability was found for both average MR and thermal sensitivity of MR.
• Individuals with higher MR showed greater increases in MR with rising temperature.
• Average MR and thermal sensitivity were positively correlated within individuals.

Conclusions:

• Individual variation in metabolic thermal sensitivity is repeatable in Drosophila melanogaster.
• This repeatability is a prerequisite for the evolution of metabolic thermal sensitivity.
• Findings provide a foundation for predicting ectotherm responses to global warming.