Flies With Brothers Make Gentler Lovers Say Oxford Scientists

Posted on January 23, 2014

Flies mating

Oxford University scientists says they have determined that flies living with their brothers cause less harm to females during courting than those living with unrelated flies. The scientists say male flies with brothers have a "more relaxed attitude to mating." The study was published here in the journal Nature.

Dr. Tommaso Pizzari of Oxford University's Department of Zoology, who led the study, says in a release, "In large populations brothers don't need to compete so much with each other for female attention since their genes will get passed on if their sibling mates successfully anyway. Their more relaxed attitude to mating results in fewer fights and they also harm the females less as their courting is not so aggressive. When unrelated flies are together, the females are constantly being pestered for sex, which may leave them little time to eat or rest."

The researchers placed trios of virgin male flies with single virgin females and allowed them to feed and mate freely. The flies were placed in different groups depending on their relatedness: AAA, AAB and ABC. AAA groups contained three full brothers, AAB groups had two brothers and one unrelated male and ABC groups contained three unrelated males.

The researchers found that the AAA groups were the most relaxed and spent less time harassing the female flies. The AAB groups had one male fly (the unrelated B fly) that was more sexually active. The males in the ABC groups competed fiercely for female attention and the level of aggressiveness damaged the overall health of the group and reduced the lifespan of all the flies.

Dr. Pizzari says, "As the AAB studies showed, a renegade fly that gets blown into a group of related flies will probably be more sexually active. The related flies in the group will be more complacent about sex since they can be fairly confident that their brothers will be passing along genetic information anyway, meaning less competition for the renegade. The aggressive sexual behaviour of this outsider will result in more fights and lower lifespans for the group as a whole, but will benefit the individual as he will father more offspring."

Photo: Amy Xinyang Hong & Cedric Tan

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