Genital Evolution and Sexual Selection

Definition

The effects of intrasexual competition and cryptic female choice on the evolution of genitalia.

Introduction

The genitalia of internally fertilizing animals are one of the most diverse characteristics within and across taxonomic groups. In many organisms, male genitalia exhibit extravagant spines, papilla, domes, hooks, and flaps and spines. The latter are generally made of keratin and can be found in a diverse array of animals including snakes and waterfowl; in domestic cats, penile spines scrape the female reproductive tract during copulation, which stimulates oviposition or egg-laying. Females too exhibit huge variation in genitalia; in the spotted hyena Crocuta crocutafemales display a pseudo-penis that closely resembles a male penis, but is formed by the clitoris and fused labia. In many organisms, particularly insects, male genitalia have other uses aside from reproduction, such as rubbing, grasping and stroking the female organs and sensory structures such as hairs...