Polymorphisms in cyclically-varying environments.

We analysed both continuous and discrete two-allele models of cyclically-varying environments with an arbitrary degree of dominance. In continuous models, the gene frequency fluctuates with the period of the environmental oscillation. For the discrete case, the calculations were carried out to second order in selection. In contrast to the continuous models, and depending on the amount of dominance and the intitial gene frequency, fixation is possible as well as polymorphism.