Evolutionary change and population dynamics are linked through the birth and death processes that drive them both. Demography is therefore central to understanding evolution and a truly eco-evolutionary framework must provide a map from genotype to phenotype, from phenotype to demographic processes, and from demography to (stage)x(genotype) dynamics (fitness, in a general sense). In this talk, we present a new model framework which incorporates basic Mendelian genetics into the powerful demographic framework of matrix population models. Any kind of ecological process can be included in the demographic component of the model: age- or stage-classified life histories of arbitrary complexity, linear or non-linear (density-dependent) dynamics, constant or time-varying (periodic or stochastic) environments. In addition, the model can incorporate genes that differentially affect males and females, and hence describes the evolution of sexually dimorphic traits.
Results/Conclusions
We solve the problem of the maintenance of heritable variation in the presence of eco-evolutionary interactions, by deriving conditions for a protected polymorphism. We show that only under special circumstances is heterozygote superiority in fitness, as measured by genotype specific population growth rate, a necessary or a sufficient condition for a genetic polymorphism. As a consequence, average fitness in the population does not always increase and populations can go extinct due to evolutionary suicide.
As an example, we present results on the maintenance of a colour polymorphism and the effect of assortative mating in the common buzzard (Buteo buteo). By varying the level of assortative mating in the model from purely random mating to perfect assortative mating, we show that assortative mating negatively impacts the population growth rate.
In this approach, each genotype has its own set of demographic rates. Therefore, selection may operate through differences in age- or stage-specific survival, fertility, or development. The flexibility of this approach provides a basis for studying a range of eco-evolutionary questions.