Selection in two-sex structured populations

Ecological and evolutionary dynamics are both driven by the fundamental demographic processes of birth, death, and development. Demography is therefore central to understanding how ecological and evolutionary processes interact when they occur on similar time scales (so called eco-evolutionary interactions). In this thesis, we introduce a model that combines the powerful demographic framework of matrix population models with basic Mendelian genetics. Chapters 2 and 3 consider linear matrix population models; chapters 4 and 5 consider density-dependent models. Chapters 2 and 4 introduce a one-sex model; chapters 3 and 5 introduce a two-sex model with sexual dimorphism in any life-history characteristic.
We derive sufficient conditions for a protected genetic polymorphism for all four cases in these four chapters. In chapter 3 we show that heterozygote superiority in genotype-specific population growth rate (λ) is a necessary and sufficient condition for a protected polymorphism when there is no sexual dimorphism in demographic rates and when the primary sex ratio is one. Similarly, in chapter 4 we find that density-dependent selection in the presence of sexual dimorphism can lead to selection for lower equilibrium stage abundances in all stages, and therefore also reduce any weighted sum of the stage abundances.