Virility Deficiency and the Sex-Ratio Trait in DROSOPHILA PSEUDOOBSCURA. II. Multiple Mating and Overall Virility Selection.

Previous studies on fitness components of Drosophila have shown the over-whelming importance of virility selection. In this study, virility selection is further partitioned into two components-one with respect to virgin females and the other with respect to nonvirgin females. The relative importance of the two components to the overall virility selection depends on the remating tendency of females which is investigated here. A theoretical model is then proposed to estimate virility selection under the condition of frequent female remating. The model is tested experimentally. When this model is applied to the Sex-Ratio system of D. pseudoobscura, Sex-Ratio males are found to suffer substantial virility reduction. The significance of this finding to the Sex-Ratio problem is discussed.