Mate discrimination and cuticular hydrocarbons in Drosophila elegans and D. gunungcola

In Drosophila elegans, two morphs are known, the brown-morph occurring from southern China to Indonesia and the black-morph occurring in the Ryukyu Islands, Japan, and Taiwan, and brown-morph populations at high altitudes in Indonesia at least sympatrically occur with a sibling species D. gunungcola. Sexual isolation has developed between the two morphs of D. elegans to some extent; females of the black-morph have a higher concentration of pentacosenes on cuticle than those of the brown-morph, and males of these morphs discriminate between the females based on this difference. In this study, it was examined whether sympatry and allopatry with D. gunungcola have resulted in the differentiation of mate recognition system in D. elegans. No significant difference was observed in the degree of mate discrimination between a sympatric pair of D. elegans and D. gunungcola and their allopatric pairs. Thus, no support was obtained for the above notion. Males of the brown- and black-morphs of D. elegans discriminate between females of own morphs and D. gunungcola. However, brown-morph males did not discriminate between females of the black-morph and D. gunungcola, and also black-morph males did not discriminate between females of the brown-morph and D. gunungcola. This may be attributed to that D. gunungcola females retained an intermediate level of pentacosenes between brown- and black-morph females.