Disruptive sexual selection in Colias eurytheme butterflies

Area of Science:

• * Evolutionary Biology
• * Chemical Ecology
• * Entomology

Background:

• * Sexual selection typically stabilizes traits, reducing variation within a species.
• * However, the male courtship pheromone in Colias eurytheme butterflies exhibits high variability.
• * This pheromone is composed of three key chemical constituents with varying proportions.

Purpose of the Study:

• * To investigate the impact of sexual selection on the variability of male pheromone composition in Colias eurytheme.
• * To understand the mechanisms driving the high intraspecific variation of this polygenic trait.

Main Methods:

• * Analysis of male courtship pheromone composition in Colias eurytheme.
• * Correlation of pheromone profiles with mating success across different female morphs (alba and orange).

Main Results:

• * Sexual selection on male pheromone composition paradoxically increases trait variability.
• * Males with specific pheromone profiles achieve disproportionate mating success with distinct female morphs (alba vs. orange).
• * This differential mating success impedes the stabilization and canalization of the pheromone trait.

Conclusions:

• * Sexual selection can maintain or increase trait diversity, contrary to the typical stabilizing effect.
• * The interaction between male pheromone variation and female morph preference drives this evolutionary phenomenon.
• * Understanding these dynamics is crucial for comprehending the evolution of complex traits in Lepidoptera.