Genetic basis and evolution of species-specific courtship song in the Drosophila auraria complex

The interpulse interval (IPI) of courtship song in the Drosophila auraria complex is the only parameter that is consistently species-specific among the several courtship elements examined within the complex. The genetic basis of the species-specific courtship song was examined by analysing the song of interspecific hybrids and of backcross progeny. IPI of all interspecific hybrids except two showed intermediate values, suggesting autosomal control of species-specific IPI. However, significant deviation for shorter IPI from midparent was found in thirteen out of 20 crosses. The chromosomal analysis between D. auraria and D. biauraria revealed that the two major autosomes had significantly large effects on IPI, but the sex chromosome and cytoplasm had no effect. Since no interaction was detected, it is concluded that each autosome acts additively in the determination of species-specific IPI. The common ancestors of the D. auraria complex may also have had autosomal control of IPI, which has been conserved during speciation in the complex.