Low evolutionary potential for blue-green egg colouration in a wild bird population

Area of Science:

• Evolutionary biology
• Animal behavior
• Quantitative genetics

Background:

• Female sexual traits are crucial for understanding postmating sexual selection.
• Egg coloration in blue-green laying species may signal female quality.
• The evolvability of these traits requires further investigation.

Purpose of the Study:

• To estimate the evolvability of blue-green egg coloration and egg size in spotless starlings (Sturnus unicolor).
• To assess the evolutionary potential of egg traits as postmating sexual signals.

Main Methods:

• Utilized an animal model in a Bayesian framework for heritability estimation.
• Analyzed multiple egg color descriptors (blue-green chroma, chroma, lightness) and egg size.
• Calculated the coefficient of additive genetic variance (CVA) and evolvability (IA) as proxies for evolutionary potential.

Main Results:

• Heritability (h2) for egg color descriptors and size ranged from low to moderate (0.31-0.44).
• Low values of CVA were found for all analyzed egg traits, indicating limited evolutionary potential.
• Results contrast with previous findings in other blue-green egg-laying species.

Conclusions:

• Spotless starlings exhibit modest genetic variation in egg traits, limiting their response to sexual selection.
• The evolutionary potential of egg coloration and size in this species appears constrained.
• These findings contribute to understanding the evolutionary architecture of female sexual traits.