Evolutionary capacity of upper thermal limits: beyond single trait assessments

Area of Science:

• Evolutionary biology
• Ecology
• Physiology

Background:

• Ectotherm distribution is influenced by thermal tolerance.
• Limited understanding exists regarding species' capacity to evolve thermal limits.
• Previous studies suggest restricted adaptive capacity to warming, but used univariate estimates.

Purpose of the Study:

• To estimate the multivariate evolutionary potential for upper thermal limits in Drosophila melanogaster.
• To investigate if adaptive capacity to heat tolerance varies with the type of thermal stress.
• To test previous findings within a multivariate evolutionary context.

Main Methods:

• Utilized a paternal half-sibling breeding design in Drosophila melanogaster.
• Assessed heat tolerance through static (basal and hardened) and ramping assays.
• Analyzed additive genetic variances and G-matrix for evolutionary potential.

Main Results:

• Additive genetic variances for heat tolerance were significant only for static measures.
• G-matrix analysis indicated that evolution of heat tolerance is primarily driven by static measures.
• Ramping heat tolerance showed minimal contribution to the evolutionary response.

Conclusions:

• The capacity for species to evolve upper thermal limits may depend on the specific type of thermal stress encountered.
• Multivariate analysis reveals differential evolutionary potential across different measures of heat tolerance.
• Findings highlight the importance of considering multiple stress types when predicting evolutionary responses to climate change.