On the maintenance of polygenic variance in a migrating population

We carry on computer simulations in order to discuss the maintenance of pol ygenic variance in a model with migrating finite diploid population, non-ov erlapping generations and non-random mating, submitted to stabilizing selec tion and to spontaneous mutations. We sweep a wide spectrum of mutation rat es and monitor: the phenotypic values distribution, its skewness and kurtos is Fisher coefficients as well as the percentage of heterozygotes. We show that, for mutation rate less than 10(-4), the phenotypic distribution becom es highly leptokurtic so that spontaneous mutations cannot realistically ba lance the effect of the stabilizing selection on the phenotype and that iso lation by distance, as modelled herein, can maintain a greater percentage o f heterozygotes. (C) 1999 Elsevier Science B.V. All rights reserved.