GENES AFFECTING COURTSHIP SONG AND MATING PREFERENCE IN DROSOPHILA MELANOGASTER, DROSOPHILA SIMULANS AND THEIR HYBRIDS.

Abstract

The male courtship songs of two closely related species, Drosophila melanogaster and Drosophila simulans, are clearly different (Ewing and Bennet-Clark, 1968; Von Schilcher and Manning, 1975; Kawanishi and Watanabe, 1980). In these studies it was found that the inter-pulse interval (ipi) is a species-specific character in Drosophila and the ipi of D. simulans is generally longer than that of D. melanogaster. Von Schilcher and Manning (1975) compared the ipi's of both species with that of hybrid males carrying the D. simulans X chromosome. Since the ipi's of this hybrid and D. simulans were almost identical, they concluded that the ipi is controlled by genes on the X chromosome, as in D. pseudoobscura and D. persimilis (Ewing, 1969). Males of D. melanogaster and D. simulans also differ sharply in their abilities to discriminate between females of the two species, D. simulans males having strong preferences for D. simulans females, but D. melanogaster males showing little discrimination (Wood and Ringo, 1980). Interspecific hybrid males carrying the D. simulans X chromosome preferred to mate with D. simulans females, but their preferences were not as strong as those of D. simulans, suggesting that this character is influenced by autosomal genes (Wood and Ringo, 1980). Unfortunately, Wood and Ringo (1980) were only able to produce interspecific hybrid males carrying the X chromosome of D. simulans, since the X chromosome of D. melanogaster is lethal to hybrid males. Recently, Watanabe (1979) discovered a mutant of D. simulans, Lethal hybrid rescue (Lhr), which renders viable the hybrid males between D. melanogaster females and D. simulans males, even though these hybrid males have the X chromosome of D. melanogaster. The purpose of this study was to examine the ipi of courtship songs of hybrid males carrying the X chromosome of D. melanogaster or D. simulans in order to analyze the genetic basis of this character. Mating preferences of these hybrid males for females of various genotypes were directly observed to clarify the role of the X chromosome in the ethological isolation between D. melanogaster and D. simulans.