Synchronised sex

 作者:公羊颍     |      日期:2019-03-08 02:19:02
By Menno Schilthuizen WHEN the biological clocks of males and females are out of sync, their sex lives suffer. Or at least it does if they are melon flies, Japanese entomologists have found. They say that differences in daily rhythms might even promote the evolution of new species. Takahisa Miyatake and Toru Shimizu of Okinawa Prefectural Agricultural Experimental Station made their discovery while studying the melon fly Bactrocera cucurbitae, a notorious pest of melons, courgettes and other members of the gourd family. By selective breeding from flies that were quickest to mature and mate, they built up a population of fast-developing individuals. In a similar way, they also bred a line of slow developers. After 25 generations, the slow developers’ larvae took more than 12 days to mature, while the fast developers matured in just 6 days. To their surprise, Miyatake and Shimizu noticed that this was not the only difference between the two lines. In nature, the melon flies mate around dusk. But among the fast developers, sexual activity peaked in late afternoon, one hour before dusk, while the slow developers only started getting interested in sex around three-and-a-half hours after nightfall. “Apparently, both rhythms are regulated by the same clock gene,” says Miyatake. To see how this would influence the ability of the slow and the fast lines to crossbreed, the researchers marked flies from both lines, put them together in cages, and watched to see which mated with which. As expected, most matings took place between males and females from the same line. The finding, which will be reported in the journal Evolution, suggests that differences in body clocks could cause new species to evolve. Miyatake says the behaviour of some species suggest they may have arisen this way. “Many closely related species of insect differ in their daily mating time,” he says. “For example, the only thing that separates two other flies, Bactrocera tryoni and Bactrocera neohumeralis, is the fact that the former mates at dusk, the latter in the daytime.” “This is interesting work,” says Jeffrey Feder, an evolutionary geneticist who studies fruit flies at the University of Notre Dame in Indiana. “It is very exciting that Miyatake and Shimizu have shown how selection on the larvae can affect the mating pattern in adults and prevent crossbreeding.” Feder agrees that the effect could be important in the evolution of new species, especially when insects undergo a shift in lifestyle. For example, if a population of flies starts feeding on a new fruit that rots quickly, this could select for fast-developing larvae with a different mating time and which would not breed with the ancestral stock. “This is getting at the heart of what Darwin was saying in On the Origin of Species,