"Female fruit flies with superior genes that allow them to lay more eggs were so attractive to male suitors they spent most of the time fending off male suitors rather than actually laying eggs," says Steve Chenoweth. (Credit: NASA's Marshall Space Flight Center/Flickr)

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Why the sexiest flies don’t have time to lay eggs

Being too sexually attractive has real drawbacks for female fruit flies. It appears the guys just can’t leave them alone long enough to lay eggs.

“We found that sexually attractive females were overwhelmed by male suitors,” says Steve Chenoweth, associate professor of biological sciences at University of Queensland.

“Female fruit flies with superior genes that allow them to lay more eggs were so attractive to male suitors they spent most of the time fending off male suitors rather than actually laying eggs. The end result was that these supposedly ‘superior’ genes could not be passed on to the next generation.”

The findings show a large number of genes appear to be a double-edged sword for females.

The genes increase flies’ egg-laying ability but also have the unfortunate side effect of boosting sexual attractiveness to a level where males can’t leave them alone.

For the study, published in the journal Current Biology, researchers allowed different groups of flies to adapt to a new environment in the lab for 13 generations. They manipulated the number of potential mates that males and females had in each group, to control the potential harassment rate.

At the end of the experiment, researchers sequenced the genomes of the flies and found a number of genes that became more common when harassment was not allowed, but these same genes became rare when male harassment was allowed to occur as usual.

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As such, increased male attention held the population back and stopped the flies from adapting as well as they could.

“We have known for some time of these harmful interactions between males and females,” Chenoweth says. “However, we hadn’t realized there may be a large number of genes fueling the interactions, or that these types of genes hamper a species’ ability to adapt to new conditions.”

Future directions for the study include pinpointing the exact types of gene functions involved and to understand the broader consequences of male-female interactions and their relevance to the evolutionary history of other species.

Other researchers from University of Queensland and from University of Ottawa contributed to the study. An Australian Research Council Fellowship, the Natural Sciences and Engineering Research Council of Canada, and University of Queensland funded the work.

Source: University of Queensland

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