Dominance and the potential for seasonally balanced polymorphism

Abstract

AbstractGenic dominance is a key component of fitness in diploid genotypes. Modelers exploring the conditions for balanced polymorphism under seasonal selection have argued that a reversal of dominance (where the fitness regime cyclically alternates the direction of dominance between a pair of alleles) is a powerful stabilizer of biallelic variation across a broad space of selection intensities. An alternative genetic mechanism, cumulative overdominance (in which the fitness regime maintains a constant direction of dominance), has been argued to preferentially stabilize alleles characterized by strong selection intensities, while requiring an implausibly strict parity under weak selection. Previous analytical conclusions were typically made under the assumption of symmetries for the dominance parameters. Here I investigate generalized dominance schemes for a bivoltine population in order to compare the proportional contribution of these genetic mechanisms to the stabilization of selective polymorphism. In particular, I derive the potential for polymorphism (a measure of the total parameter space conferring stability) for the generalized sex-independent model in four parameters.