On the maintenance of polygenic variance in a migrating population

We carry on computer simulations in order to discuss the maintenance of polygenic variance in a model with migrating finite diploid population, non-overlapping generations and non-random mating, submitted to stabilizing selection and to spontaneous mutations. We sweep a wide spectrum of mutation rates and monitor: the phenotypic values distribution, its skewness and kurtosis Fisher coefficients as well as the percentage of heterozygotes. We show that, for mutation rate less than 10−4, the phenotypic distribution becomes highly leptokurtic so that spontaneous mutations cannot realistically balance the effect of the stabilizing selection on the phenotype and that isolation by distance, as modelled herein, can maintain a greater percentage of heterozygotes.