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Scanning electron micrographs of the posterior lobe of Drosophila simulans (top) and Drosophila melanogaster (bottom) extending from the genital arch onto the clasper.Credit: Kentaro Tanaka
Drosophila melanogaster has given scientists new insights into the genetic basis of the rapid evolution of male external reproductive organs driven by sexual selection.
Secondary sexual characteristics, such as the peacock’s tail and the male external genitalia of insects, are known to be the most rapidly evolving animal body parts.
This is thought to be caused by sexual selection, including female selection, and the different evolutionary needs of each sex to find suitable mates and maximize fitness.
Now, scientists from Durham University and Oxford Brookes University in the UK have discovered one of the genes that contributes to the evolution of reproductive organs between two closely related species of fruit flies. Research is published in diary current biology.
The researchers looked at the posterior lobes of the male reproductive organs of Drosophila simulans and Drosophila mauritiana. Both are species of Drosophila melanogaster, a subgroup of Drosophila melanogaster.
These leaves have changed rapidly in shape and size within 240,000 years, and the leaves of Drosophila simulans are much larger than those of Drosophila mauritiana.
They found that high levels of the evolved gene Sox21b suppress the size of reproductive leaves in Drosophila mauritiana, contributing to smaller reproductive leaves than in Drosophila simulans.
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Bright-field microscopy image of the male external genitalia of Drosophila melanogaster. Credit: Javier Figueras Jiménez.
Because the posterior lobe is used by males to grasp female flies during sexual intercourse, the findings could help us better understand the genomic effects of sexual selection on changes in genital shape and size. Researchers say it could be helpful.
Sexual selection has been shown to drive evolutionary changes in the reproductive organs of other insects and animals, but this is a rare case in which the genes behind it have been identified.
The research team edited the genomes of Drosophila mauritiana and Drosophila simulans and showed that changes in Sox21b change the shape and size of the posterior lobe. This also affected the mating period of these flies.
Project leader Professor Alistair McGregor from Durham University’s School of Life Sciences said: “The posterior lobe of the Drosophila male reproductive tract plays a very important role in sex.
“By identifying the genes responsible for differences in the size and shape of reproductive structures between species, we will be able to manipulate the Drosophila male reproductive organs in a way that recapitulates the variation that exists in nature.
“We now know whether this mutation is a target of female selection, gives males a different ability to secure mating, as the extended mating period suggests, or whether this is due to competing interests of females. More detailed behavioral experiments can be conducted to determine whether this is caused by “men and women.” ”
Study co-author Dr Daniela Santos-Nunez, from the School of Biomedical Sciences at Oxford Brookes University, said: ‘Although Drosophila simulans and Drosophila mauritiana can mate with each other, this only happens very rarely. In fact, Drosophila melanogaster females often mate.” I like it better than the female D simulation.
“Identifying one’s species by genital size may therefore be one way to ensure that these particular species mate more efficiently, thereby strengthening species divergence.” there is.
“This reveals part of the genetic basis for how sexual selection has driven the evolution of male reproductive organs over thousands of years.”
For more information:
Sox21b underlies the rapid diversification of novel male genital structures among Drosophila species. current biology (2024). DOI: 10.1016/j.cub.2024.01.022. www.cell.com/current-biology/f … 0960-9822(24)00022-8