Sexual selection, population density, and availability of mates

The evolution of sexual features designed to attract individuals of the opposite sex is studied. When limitation of sexual choice by physical availability of mates is accounted for, the exact distribution of the number of alternative mates available to a choosing individual (usually female) proves crucial for the evolution of sexual attractiveness. Selection for or against the attractive type or maintenance of a protected polymorphism of types in the population are shown to be dependent upon this distribution. It is further demonstrated that high high population density is always favorable to the evolution of the attractive type. Some ecogenetical aspects of sexual selection and population density are suggested.