Molecular and behavioral analysis of sex-linked courtship song variation in a natural population of Drosophila melanogaster

Genes controlling the "lovesong" in Drosophila are particularly interesting under a evolutionary point of view as they could be involved in the reproductive isolation between closely related species and, as a consequence, in the speciation process. We carried out a survey of sex-linked molecular and behavioral courtship song variation in 27 lines derived from a natural population of Drosophila melanogaster in Italy. We sequenced a 983 bp fragment of cacophony(cac), a calcium channel gene controlling aspects of the courtship song. The same region was also sequenced in a D. simulans strain. Only 5 non-coding sites were polymorphic among the D. melanogaster lines, and no amino acid substitutions were found between the two species. Statistical tests applied to the data did not reveal any significant deviations from a neutral model. Using the same lines we also carried out an analysis of three different song parameters which are known to be affected by the cac(S) song mutation: interpulse-interval (IPI), pulse amplitude (PA) and cycles per pulse (CPP). We found significant differences among the lines in IPI and PA, and for the latter a significant association with one of the polymorphic sites of cac.