Effects of artificial stabilizing selection on Drosophila populations subjected to directional selection for another trait.

Stabilizing selection for a set of morphometric wing traits was combined with directional selection for the increased expression of radius incompletus (ri) mutation of Drosophila melanogaster. Three experimental regimes were used: directional and stabilizing selection (stabilized lines); directional selection (unstabilized lines); no selection (controls). Response to selection for ri expression was similar in all selected lines but variation of this character was higher in the unstabilized lines compared to the stabilized ones. The competitive indices measured after termination of selection did not significantly differ under different treatments while fluctuating asymmetry was significantly lower in stabilized than in unstabilized lines. The possible causes of these differences are discussed.