Male flies with stalked eyes and short eye stalks are less attractive to females but fight more fiercely, scientists find

In flies with stalked eyes, the longer eye stalks attract ladies. Females prefer males with longer eyes, and other males are less likely to fight them for access to females. But some males have one copy of the X chromosome, which still causes short eye stalks.

Scientists studying why this mutation has not died out, despite sexual selection, have discovered that the flies may be compensating for their shorter eye stalks with increased aggression.

“This is the first time I have become aware that there is evidence of a link between a selfish gene and aggressive behavior,” said Dr. Josephine Reinhardt of the State University of New York-Geneseo, corresponding author of the article in Frontiers in ethology.

“These motor X chromosomes are quite interesting because they illustrate how parts of our genetic code don’t necessarily work together, but have their own selfish interests. This is an extreme example, but just carrying one of these chromosomes selfish behavior has an impact on many aspects of the biology of these animals, even their behavior.

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There are two different types of X chromosome present in stalk-eyed flies. The

“The motor X chromosome has a huge natural advantage because it transmits more than the 50-50 genetic rule that most of us learned in high school biology,” Reinhardt explained.

“Up to 100% of a male’s offspring eventually inherit the has not occurred, we are interested in understanding what other traits might counteract this advantage.

Male stalk-eyed flies defend access to mates by intimidating them and fighting. To test whether flies carrying the motor X are more aggressive, scientists used populations of flies carrying either type of . So the researchers compared competitors with similar eye stalks and then filmed their contests. and analyzed their behavior.

They found not only that fighting behaviors were more common when the two flies were very similar in terms of eye stalk size, but that these behaviors were more frequently observed in males carrying the X driver. Males who used these fighting behaviors more were more likely to win contests. . Scientists also observed that men with the motor X chromosome were more likely to win if they engaged more in fighting than in displays.

“When fighters are mismatched, fights tend to end quickly, with the smaller male retreating,” Reinhardt said. “When a male with the driver X chromosome fights a male with similarly sized eye stalks, he is more aggressive. But because driver

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This could explain why short-eyed flies were able to mate. Longer eye stalks signal a larger body and a more dangerous opponent, which is why flies with shorter eye stalks typically withdraw from contests.

If males carrying the motor by their opponent.

While this added aggression could be dangerous, it could also help flies obtain mating opportunities they wouldn’t otherwise have. However, this cannot completely counteract sexual selection. Modeling the spread of the

“I would say that this study constitutes a first discovery,” warned Reinhardt.

“A larger study could be done in which we specifically test the increase in high-intensity behavior that we observed here in a larger sample. Additionally, this is a laboratory study, it is not therefore not entirely clear to what extent it would apply to field behavior. Finally, females were not tested.

“If the driving the case.”