Circadian rhythms of female mating activity governed by clock genes in Drosophila.

The physiological and behavioral activities of many animals are restricted to specific times of the day. The daily fluctuation in the mating activity of some insects is controlled by an endogenous clock, but the genetic mechanism that controls it remains unknown. Here we demonstrate that wild-type Drosophila melanogaster display a robust circadian rhythm in the mating activity, and that these rhythms are abolished in period- or timeless-null mutant flies (per(01) and tim(01)). Circadian rhythms were lost when rhythm mutant females were paired with wild-type males, demonstrating that female mating activity is governed by clock genes. Furthermore, we detected an antiphasic relationship in the circadian rhythms of mating activity between D. melanogaster and its sibling species Drosophila simulans. Female- and species-specific circadian rhythms in the mating activity of Drosophila seem to cause reproductive isolation.