Long-Term Evolution Under Heatwave Conditions in the Seed Beetle, Callosobruchus maculatus

Area of Science:

• Evolutionary Biology
• Climate Change Ecology
• Insect Physiology

Background:

• Heatwaves are increasing in frequency and intensity, posing significant threats to various taxa.
• Previous research on heatwave impacts often overlooks long-term evolutionary responses and focuses on short-term effects.

Purpose of the Study:

• To investigate the long-term effects of multigenerational heatwave exposure on life history traits.
• To assess the adaptive capacity of populations to recurrent heatwaves.

Main Methods:

• Utilized the seed beetle (Callosobruchus maculatus) model system.
• Exposed populations to 43 generations of fluctuating temperatures with intermittent heatwaves (+2°C, 42°C peak for 7 days/generation).
• Assayed development time and lifetime reproductive success (LRS) under both heatwave-evolved and control conditions.

Main Results:

• Populations evolved under heatwave conditions showed similar development times but reduced LRS compared to controls.
• When assayed at a constant benign temperature (29°C), beetles from both thermal regimes exhibited slower development but comparable LRS.
• Long-term heatwave exposure incurred a minimal fitness cost that was mitigated under benign conditions.

Conclusions:

• Multigenerational heatwave exposure can lead to adaptive responses, though potentially with trade-offs.
• The fitness costs associated with heatwave adaptation may be context-dependent and reversible.
• This study highlights the importance of long-term, multigenerational experiments for understanding population responses to climate change.