Asymmetric response to directional selection for licking behavior of Drosophila melanogaster males.

Selection for high and low licking rate was carried out on courting males of a cage-population of Drosophila melanogaster for 21 generations. The males were tested against a standard female tester genotype in every generation. The low-scoring line responded linearly to selection, reaching a plateau after eight generations. The attempt to raise the licking rate above the level of the base population was not effective. The realized heritability of the L and H line over the first seven generations was 41.0 and 0.4%, respectively. From the fourth generation onward, the two lines differed significantly. Reciprocal crossing between the two lines indicated the absence of X-chromosome and maternal effects. There was no significant dominance. The selection for licking in males had no discernible effect on female sexual activity. H-line males mated significantly faster with standard females than L-line males.