Macroevolutionary Patterning in Glucocorticoids Suggests Different Selective Pressures Shape Baseline and...

Area of Science:

• Evolutionary biology
• Endocrinology
• Vertebrate physiology

Background:

• Glucocorticoid (GC) hormones are key mediators of vertebrate phenotypes.
• Circulating GC concentrations exhibit significant variation across species.
• Understanding GC evolutionary patterns is crucial for comprehending adaptation.

Purpose of the Study:

• To investigate macroevolutionary patterns in GC levels across tetrapods.
• To test hypotheses regarding GC variation and evolution.
• To determine if selective pressures consistently shape GC evolution.

Main Methods:

• Macroevolutionary analysis of GC levels in tetrapods.
• Testing seven specific hypotheses on GC variation.
• Evaluating GC evolution in relation to environmental and life-history factors.

Main Results:

• Baseline GC levels correlate with 'supportive' roles: higher in smaller organisms, demanding environments, and species with fewer reproductive opportunities.
• Stress-induced GC levels correlate with 'protection' roles: lower during breeding in species with fewer reproductive opportunities.
• Distinct selective pressures shape baseline and stress-induced GCs in challenging environments.

Conclusions:

• Selective pressures consistently influence GC evolution across broad taxonomic scales.
• GC evolution demonstrates a balance between supporting responses to challenges and protecting against GC-induced costs.
• Baseline and stress-induced GC regulation are influenced differently by environmental and life-history factors.