Same Colors for Different Functions: Implications for the Evolution of Carotenoid-Based Ornamentation

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Biochemistry

Background:

• Sexual ornamentation is often assumed to be costly, signaling individual quality.
• Carotenoid-based colors are hypothesized to incur significant production costs.

Purpose of the Study:

• To test if sexually selected carotenoid colors are more saturated than nonsexual colors.
• To investigate the cost of carotenoid-based plumage in canaries, goldfinches, and allies.

Main Methods:

• Comparative analysis of carotenoid-based plumage color saturation.
• Examining breast (sexual) and rump (nonsexual) coloration in select bird species.
• Assessing the codistribution of color saturation between male and female birds.

Main Results:

• Male and female color saturation showed asymmetric codistribution only in the breast, suggesting sexual selection.
• Breast color saturation was not consistently higher than rump color saturation.
• Rump color saturation was independent of breast color saturation.

Conclusions:

• Carotenoid-based coloration may not inherently bear significant costs for sexual signaling.
• Social costs, cost-free signaling mechanisms, or mate choice in socially monogamous species may drive the evolution of these signals.
• Challenges the assumption of inherent costs in carotenoid-based sexual ornamentation.