Evidence for lower plasticity in CT_MAX at warmer developmental temperatures

Area of Science:

• Evolutionary Biology
• Climate Change Biology
• Physiological Ecology

Background:

• Phenotypic plasticity is crucial for species survival under climate change.
• The climatic variability hypothesis predicts greater plasticity in variable environments.
• Empirical evidence for this hypothesis remains limited.

Purpose of the Study:

• To investigate the capacity of ten Drosophila species to enhance their critical thermal maxima (CTMAX) through phenotypic plasticity.
• To determine if climatic variability influences the degree of thermal plasticity.
• To assess the fitness implications for tropical species under warming conditions.

Main Methods:

• Exposing ten Drosophila species to four fluctuating developmental temperature regimes (13-33°C).
• Measuring increases in critical thermal maxima (CTMAX) via developmental acclimation and adult heat hardening.
• Analyzing the relationship between climatic variables and thermal plasticity, and assessing egg-to-adult viability.

Main Results:

• Most species demonstrated increased CTMAX through acclimation and hardening.
• No overall relationship was found between climatic variables and absolute plasticity.
• Plasticity varied with developmental temperature, with tropical species showing reduced CTMAX and viability at warmer temperatures.

Conclusions:

• Phenotypic plasticity provides a limited (<0.60°C shift in CTMAX) response to warming, potentially offering short-term population persistence.
• Tropical species may be more vulnerable to climate change than predicted due to reduced thermal tolerance and fitness at higher temperatures.
• The long-term adaptive capacity of phenotypic plasticity in the face of rapid climate change remains uncertain.