The effects of increased phenotypic variance on the evolutionary outcomes of generalized major-gene models.

The study of generalized major-gene models has been extended to accommodate selective, assortative mating mechanisms. In this formulation the consequences of amplified phenotypic variance on the major gene frequency are investigated. It is shown that the rate of approach to the equilibrium state is slowed under attenuated assortative mating tendencies and/or with increased environmental noise. Also, an increased phenotypic variance induces more skewness in the nature of the gene frequencies, i.e. a less 'central' polymorphic expression. Where strong positive assortative mating occurs, a population fixation state results. Negative assortment generally facilitates the stability of a 'central' polymorphism.