Great tits differ in glucocorticoid plasticity in response to spring temperature

Area of Science:

• Endocrinology
• Ecology
• Evolutionary Biology

Background:

• Environmental temperature fluctuations impact vertebrate energy metabolism and phenotypic plasticity.
• Glucocorticoid hormones are key mediators of environmentally induced phenotypic plasticity.
• Climate change is predicted to increase temperature variability, necessitating an understanding of population-level adaptive potential.

Purpose of the Study:

• To quantify individual variation in glucocorticoid plasticity in response to environmental temperature gradients in wild great tits (Parus major).
• To assess the potential of free-living populations to cope with temperature fluctuations through plastic or evolutionary changes.

Main Methods:

• A reaction norm approach was employed, involving repeated sampling of wild great tit individuals over five years.
• Circulating glucocorticoid concentrations (baseline and stress-induced) were measured in relation to environmental temperature.
• Individual variation in the plastic response of glucocorticoid traits to temperature was analyzed.

Main Results:

• Both baseline and stress-induced glucocorticoid concentrations increased with decreasing environmental temperatures at population and individual levels.
• Significant individual differences in the plasticity of glucocorticoid responses to temperature were observed.
• Average glucocorticoid concentrations and the degree of plasticity covaried for baseline glucocorticoids.

Conclusions:

• Individual variation in glucocorticoid plasticity to temperature exists in wild vertebrate populations.
• This variation is a critical factor for assessing the adaptive capacity of populations to environmental temperature fluctuations.
• Understanding glucocorticoid plasticity is essential for predicting species' responses to climate change.