Nonlinear frequency-dependent selection at a single locus with two allelesand two phenotypes

The paper investigates the discrete frequency dynamics of two phenotype dip loid models where genotypic fitness is an exponential function of the expec ted payoff in the matrix game. Phenotypic and genotypic equilibria are defi ned and their stability compared to frequency-dependent selection models ba sed on linear fitness when there are two possible phenotypes in the populat ion. In particular, it is shown that stable equilibria of both types can ex ist in the same nonlinear model. It is also shown that period-doubling bifu rcations emerge when there is sufficient selection in favor of interactions between different phenotypes.