GOOD GENES AND DIRECT SELECTION IN THE EVOLUTION OF MATING PREFERENCES

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Genetics

Background:

• Mating preferences are crucial for sexual selection.
• The 'good genes' hypothesis suggests preferences evolve for traits indicating genetic quality.
• Direct natural selection can also influence the evolution of preferences.

Purpose of the Study:

• To quantitatively model the impact of good genes and direct natural selection on mating preference evolution.
• To assess the relative contributions of indirect (good genes) and direct selection on mating preferences.
• To understand the mechanisms behind exaggerated male display traits in sexually selected species.

Main Methods:

• Development of a quantitative genetic model.
• Inclusion of evolving genetic variances and covariances under an infinitesimal model.
• Simulation of the interplay between good genes and direct natural selection on mating preferences and male traits.

Main Results:

• The good genes process provides only weak indirect selection on mating preferences (≤ few percent).
• Without strong direct selection, good genes alone predict limited exaggeration of male traits (few phenotypic standard deviations).
• Substantial exaggeration occurs if preference genes are nearly selectively neutral or if direct selection is strong.

Conclusions:

• Direct selection on preference genes, via behavior or pleiotropy, is a potent driver of extreme mating preferences and exaggerated male traits.
• The good genes process alone is insufficient to explain extreme sexual selection.
• Direct selection likely plays a critical role in species with highly exaggerated sexual traits.