Localization of genes affecting species differences in male courtship song between Drosophila virilis and D. littoralis.

The males of six species of the Drosophila virilis group (including D. virilis) keep their wings extended while producing a train of sound pulses, where the pulses follow each other without any pause. The males of the remaining five species of the group produce only one sound pulse during each wing extension/vibration, which results in species-specific songs with long pauses (in D. littoralis about 300 ms) between successive sound pulses. Genetic analyses of the differences between the songs of D. virilis and D. littoralis showed that species-specific song traits are affected by genes on the X chromosome, and for the length of pause, also by genes on chromosomes 3 and 4. The X chromosomal genes having a major impact on pulse and pause length were tightly linked with white, apricot and notched marker genes located at the proximal third of the chromosome. A large inversion in D. littoralis, marked by notched, prevents more precise localization of these genes by classical crossing methods.