20 Sexual Selection

In this chapter we explore the routes that link differences between the sexes to sexual selection. Why is sexual selection often stronger in one sex? Why is the choosier sex usually less sexually competitive? What is the relationship between sexual selection and parental care? We outline -key theoretical models that apply to most taxa and account for the origin and evolution of sexual differences in parental care, mating effort, sexual conflict, and choosiness. This theoretical backdrop sets the scene for empirical studies that usually focus on quantifying current levels of sexual selection (Shuster & Wade 2003), identifying genetic constraints on the evolution of sexual traits (Blows 2007) and measuring the sex-specific costs and benefits of mate choice, mating rates, and alternative male mating tactics. These topics are covered in detail in chapters 21-25.