ABSTRACT
Mating in sexually reproducing species is rarely an equal-opportunity event. Some individuals, relative to others, have access to more mates or mates of higher quality (here, a term strictly reserved for advantages having to do solely with reproduction). One reason for variation in mating success is that members of the other sex prefer mates who possess traits not possessed by all. A second reason is that individuals vary in their abilities to intimidate competitors of their own sex. Selection that results from differences in traits affecting access to number and quality of mates is sexual selection.
