Localization of genes affecting species differences in male courtship songbetween Drosophila virilis and D-littoralis

The males of six species of the Drosophila virilis group (including D. viri lis) keep their wings extended while producing a train of sound pulses, whe re the pulses follow each other without any pause. The males of the remaini ng five species of the group produce only one sound pulse during each wing extension/vibration, which results in species-specific songs with long paus es (in D. littoralis about 300 ms) between successive sound pulses. Genetic analyses of the differences between the songs of D. virilis and D. littora lis 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 an d 4. The X chromosomal genes having a major impact on pulse and pause lengt h 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 c lassical crossing methods.