Incipient speciation in Drosophila melanogaster involves chemical signals

Abstract

The sensory and genetic bases of incipient speciation between strains of Drosophila melanogaster from Zimbabwe and those from elsewhere are unknown. We studied mating behaviour between eight strains – six from Zimbabwe, together with two cosmopolitan strains. The Zimbabwe strains showed significant sexual isolation when paired with cosmopolitan males, due to Zimbabwe females discriminating against these males. Our results show that flies' cuticular hydrocarbons (CHs) were involved in this sexual isolation, but that visual and acoustic signals were not. The mating frequency of Zimbabwe females was highly significantly negatively correlated with the male's relative amount of 7-tricosene (%7-T), while the mating of cosmopolitan females was positively correlated with %7-T. Variation in transcription levels of two hydrocarbon-determining genes, desat1 and desat2, did not correlate with the observed mating patterns. Our study represents a step forward in our understanding of the sensory processes involved in this classic case of incipient speciation.

Genetic and Neural Mechanisms that Inhibit Drosophila from Mating with Other Species

“…Chemosensory cues encoded by cuticular hydrocarbons (CHs) profoundly influence social behavior in flies (Antony and Jallon, 1982; Billeter et al, 2009; Coyne et al, 1994; Ferveur, 2005; Grillet et al, 2012; Higgie et al, 2000; Jallon and David, 1987; Savarit et al, 1999). We asked whether cuticular extracts from D. simulans, virilis, and yakuba females inhibited courtship by D. melanogaster males.…”

Hydrocarbon divergence and reproductive isolation in Timema stick insects

“…For example, in Chorthippus parallelus grasshoppers, male hydrocarbon variation, but not other potential mate-choice signals, was significantly linked with the degree of assortative mating among individuals from 12 populations [48]. Similarly, in Chrysochus beetles [49], and some Drosophila vinegar flies (e. g., [50,51]), mating between individuals from closely-related species or strains is affected in part by variation in cuticular hydrocarbon profiles. In Timema , assuming individuals indeed detect aspects of hydrocarbon profiles, decreased propensity to accept mates with lower hydrocarbon profile similarity would limit the likelihood of potentially costly interspecific matings.…”

desat1

“…48 However, in Zimbabwean strains, both sexes produce substantial amounts of C5-CHs [5,9-HD in females; 5-tricosene (5-T) in males]. 49 Zimbabwean females show a strong sexual isolation against cosmopolitan males which is partly due to the male CH profile.…”