Sexual isolation between Drosophila simulans and D. mauritiana : D. simulans females do not discriminate against intact-wing D. mauritiana males

Female mate choice plays an important role in sexual isolation. The present study examined sexual isolation using D. simulans and D. mauritiana in conditions where females had no opportunity to compare males versus where females were able to choose males. The sound produced by wing vibration in males (courtship song) affects female receptivity in Drosophila . Females of both species copulated with intact conspecific males more than intact heterospecific males and wingless conspecific and heterospecific males. Drosophila mauritiana females copulated only with intact conspecific males within 30-min observations period without comparing other males, suggesting that absolute criteria are used for decision-making to accept courting males. Females of D. simulans copulated with intact D. mauritiana males as well as wingless D. simulans or D. mauritiana males in no-choice conditions. In a choice situation, D. simulans females copulated with intact D. mauritiana males as well as wingless D. mauritiana males when the females were courted by both types of males, suggesting that D. simulans females accept intact D. mauritiana males as if they are mute. Females of D. simulans copulated with intact D. simulans males as well as intact D. mauritiana males when they were courted by males of either type, whereas they copulated with intact D. simulans males more than intact D. mauritiana males in true choice situations. These results suggest that females make a comparative review of courting males before accepting a male and that conspecific song is a factor in criteria affecting female selectivity.