promiscuous fruit flies

Promiscuous females and their role in evolution

Today: How female promiscuity changes male behaviour

Scientists genetically manipulated female fruit flies to make them more promiscuous, and then observed what impact this had on the male fruit flies’ sexual behaviour.

  • Saturday 19 January: watch out for a story about some shady behaviour from cane toads. It’s being published in Scientific Reports and is under embargo until 9pm ADST tonight. Contact us if you’d like an embargoed copy of this release.
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You can read more about the fruit flies story below, including contact details of the scientist to interview.

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Promiscuous females and their role in evolution

Males have to make less of an effort to mate with promiscuous female fruit flies, making the quality and quantity of their semen all the more important in the competition to fertilise the females’ eggs.

This also leads to male flies repeatedly mating with the same female, according to a paper published overnight in Nature Communications, by researchers from Macquarie University, the University of Oxford and the University of East Anglia, who looked into the eyes of thousands of fruit flies.

Over the last 50 years, biologists have realised that females in most animal species mate with multiple males during their lifetimes, in contrast to the Victorian-era fairytale of the monogamous female. However they didn’t know how this behaviour influences how fruit flies and other species evolve.

Macquarie’s Dr Juliano Morimoto and colleagues from the UK wanted to test the theory that increasing female promiscuity would reduce male competition before mating, while increasing their competition to fertilise the female’s eggs after mating.

To do this, they first genetically manipulated female Drosophila melanogaster fruit flies to increase their promiscuity.

By deleting a sex peptide receptor, they reduced the time the females weren’t sexually receptive after mating and therefore led to them mating more frequently.

Hundreds of the more promiscuous females were marked with paint and their interactions with male flies monitored. The researchers painstakingly counted the thousands of offspring produced and identified their fathers based on eye colour.

“We found that when females mate promiscuously, male attractiveness is less important,” says Juliano. “Instead, having a large ejaculate might be what males need to win the war.”

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