Polygenic control of a mating signal in Drosophila.

Recent findings show that traits which influence speciation in the melanogaster subgroup of Drosophila can be determined by relatively few loci and/ or be sex-linked. Using backcrosses between D. simulans and D. mauritiana, we show that an acoustic mating signal which plays an important role in courtship (the interpulse interval of the 'lovesong') has a polygenic determination. There is no evidence of single genes of large effect, a disproportionate contribution of the sex chromosome or epistasis. The probability of finding single genes with a large effect on sexual isolation may vary with the mode of signalling involved.