Sexual selection

Definition

A mode of natural selection driven by differential mating success, arising from competition among individuals of the same sex for access to mates (intrasexual selection) or from mate choice by one sex for members of the opposite sex (intersexual selection). In arthropods, sexual selection generates diverse phenotypic outcomes including exaggerated weaponry, elaborate courtship displays, pheromonal signaling, and conspicuous ornamental traits that may reduce survival but enhance reproductive fitness.

Etymology

Coined by Charles Darwin in 1859, distinguishing selection pressures arising from reproductive competition from those arising from environmental survival (natural selection).

Example

Male stag beetles (Lucanidae) possess enlarged mandibles used in combat with rival males for access to females, illustrating intrasexual selection; female moths detect and orient toward species-specific sex pheromones released by males, demonstrating intersexual selection through chemical signaling.

Related Terms

• natural selection
• Mate choice
• Intrasexual selection
• Intersexual selection
• sexual dimorphism
• lek
• Sperm competition
• Courtship behavior
• pheromone
• fitness

Usage Notes

Distinguished from natural selection by its exclusive focus on reproductive success rather than survival or resource acquisition. In insects and arachnids, sexual selection frequently operates through chemical, acoustic, or visual channels that differ markedly from vertebrate systems. The term is sometimes misapplied to any reproductive behavior; precise usage reserves it for traits that evolved specifically because they confer mating advantages. Sexual selection can oppose natural selection when ornamental traits increase predation risk.