Temperature niche shift observed in a Lepidoptera population under allochronic divergence

Area of Science:

• Ecological genetics
• Evolutionary biology
• Climate change adaptation

Background:

• Adaptive divergence can lead to populations with distinct environmental tolerances.
• Life cycle timing (allochrony) can drive ecological differentiation.
• Understanding thermal tolerance is crucial for predicting species responses to climate change.

Purpose of the Study:

• To investigate adaptive divergence in high-temperature tolerance in Thaumetopoea pityocampa populations.
• To compare thermal tolerance between sympatric populations with different life cycle timings (summer vs. winter larval development).
• To assess the impact of heat stress on larval survival and mortality.

Main Methods:

• Experimental exposure of Thaumetopoea pityocampa larvae (first and second instars) to controlled heat treatments (36-42 °C).
• Comparison of survival rates between a summer-developing population (Leiria SP) and winter-developing populations (Leiria WP, Bordeaux WP).
• Application of Cox regression models to analyze mortality hazard and identify factors influencing survival.

Main Results:

• Leiria SP demonstrated significantly higher upper survival thresholds compared to Leiria WP populations.
• Mortality hazard increased with higher temperatures and was significantly higher in winter-developing populations.
• Larval instar and population type were significant predictors of mortality risk under heat stress.

Conclusions:

• Allochronic divergence facilitates adaptive divergence in thermal tolerance in Thaumetopoea pityocampa.
• Summer-developing populations are better adapted to high temperatures, suggesting potential for adaptation to climate change.
• Individual variability within populations may play a role in facilitating selection and adaptation to thermal stress.