Quantitative genetics of seminal receptacle length in Drosophila melanogaster

The length of the female's primary sperm-storage organ, the seminal recepta cle, has undergone rapid divergence within the Drosophila genus. Quantitati ve genetic analysis of seminal receptacle length was carried out on two lab oratory strains of Drosophila melanogaster that had undergone artificial se lection for both increased and decreased organ length. Realized heritabilit ies were 0.176 and 0.270 for the two experiments. Parental strains, F-1, F- 1r (reciprocal), F-2, backcross, and backcross reciprocal generations were used in a line-cross (generation means) analysis. This analysis revealed th at additive, dominance, and additive-by-dominance epistasis contributed sig nificantly to the means. No significant maternal effects were found. Varian ce analysis indicated that a completely additive model was adequate to expl ain the variances observed in these lines. Castle-Wright minimal estimates of 5.25 and 1.91, segregating loci responsible for mean differences, were f ound for the two respective experiments. There were significant positive co rrelations between additive effects of seminal receptacle length and thorax length in both experiments. The correlated evolution of sperm and seminal receptacle length is discussed.