GENETIC-STUDIES OF ASSORTATIVE MATING - A SIMULATION STUDY .2. ASSORTATIVE MATING IN UNSELECTED POPULATIONS

Effects of 25 generations of positive and negative phenotypic assortat ive mating were compared with that of random mating in unselected (all individuals reproducing) and randomly chosen (25% of individuals repr oducing) populations of various size. The trait under assortation was controlled by either 100 or 2500 loci. Twenty-five generations of posi tive assortative mating in large unselected populations (effective pop ulation size equal to 1600) caused an accumulating increase in additiv e genetic variance (V-A), causing V-A to become 440% of the base popul ation's V-A. Negative assortative mating had a small asymptotic effect in the opposite direction, causing V-A to become 72% of the base popu lation's V-A. Changes in V-A were due almost exclusively to gametic ph ase (linkage) disequilibrium. Positive and negative assortative mating were able to slightly increase or decrease the inbreeding coefficient and the degree of homozygosity. Number of loci, population size and s tructure had either negligible effects in combination with negative as sortative mating or worked in the direction of accentuating the effect s of positive assortative mating. (C) 1997 Scandinavian University Pre ss.