By Isobel Williams via SWNS
The gene behind the evolution of male genitalia has been identified.
Researchers have discovered the gene responsible for the rapid changes in shape and size of male external genitalia.
Secondary sexual characteristics such as peacocks’ tails and the male external genitalia of insects are known to be among the fastest evolving animal body parts.
It is thought that this is driven by sexual selection including through female choice and the different evolutionary needs of each sex to find the right mate.
Now scientists at Durham University and Oxford Brookes University have found one of the genes that contributes to genital evolution between two closely related species of fruit fly.
To get their results the team studied the genital lobes of Drosophila simulans and Drosophila mauritiana, both of which are species in a subgroup of fruit fly.
The genital lobes are used by male fruit flies to grasp the female during sex.
These parts have rapidly changed in shape and size in less than 240,000 years and those of Drosophila simulans are much bigger than those of Drosophila mauritiana.
They found that evolved higher levels of the gene called Sox21b repressed the size of the genital lobes in Drosophila mauritiana, contributing to them having smaller genitals.
The research team then edited the genome of Drosophila mauritiana and Drosophila simulans to show that changes in Sox21b changed the posterior lobe shape and size.
The results, published in the journal Current Biology, also showed that this gene affected the mating duration of these flies.
Sexual selection has been shown to drive evolutionary change in the genitalia of other insects and animals, but this is a rare case where a gene behind it has been identified.
Professor Alistair McGregor, from the Department of Biosciences at Durham University, said: “The genital posterior lobes of male fruit flies play a really important role in sex.
“Identifying genes responsible for differences in size and shape of genital structures between species allows manipulation of Drosophila male genitalia in a way that replicates the variation that exists in nature.
“We can now do more detailed behavior experiments to determine if this variation is the target of female choice, if it gives males different ability to secure mating, as an increase mating duration seems to suggest, or if this is driven by the conflicting interests of males and females.”
Dr. Daniela Santos Nunes, of Oxford Brookes University, added: “Although Drosophila simulans and Drosophila mauritiana can mate with each other, this happens very rarely and indeed D mauritiana females are much choosier than D simulans females.
“Therefore, identifying their own species by genital size, could be one way that these particular species ensure they are mating more efficiently and are therefore reinforcing the divergence of their species.
“This reveals part of the genetic basis of how male genital evolution has been driven over thousands of years due to sexual selection.”
