14/09/2025
In 2017, Romiguier and his colleagues discovered that the worker ants of M. ibericus had unexpectedly diverse DNA, perhaps a sign their queens had mated with distantly related males. Further genetic analysis hinted at another surprise. The hybrid workers’ fathers seemed to belong to M. structor, another species altogether.
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Interspecies mating is known in a few ant species, where the s***m of a queen’s own species can produce larvae that become new queens but not sterile workers. The queens have solved this challenge by also mating with males of another species to produce workers, and M. ibericus queens seemed to be using this strategy, too. But there was something puzzling. Colonies were thriving even in regions outside of the range of M. structor, such as the northern Mediterranean coast and the Italian island of Sicily, where the closest M. structor colonies are more than 700 kilometers away. “It was impossible to imagine,” Romiguier says.
To figure out what was happening, Romiguier had to collect some males, which is harder than it sounds. Harvester colonies can contain 10,000 ants, with only a few males around during specific times of the year. Romiguier and his colleagues dug up some 50 nests along farm roads near Lyon, France, before they finally got their first quarry.
After collecting 132 males from 26 M. ibericus colonies, they found that about half of the males were nearly hairless and resembled M. structor. These males also had the nuclear genomes of M. structor but the mitochondria of M. ibericus, proving the males had hatched from eggs laid by M. ibericus queens.
The researchers think the M. ibericus queens are cloning the M. structor males. The queens allow the M. structor s***m to enter their eggs, but at some point they remove their own genes from the egg’s nucleus to prevent fertilization, thereby ensuring the egg develops into a male and not a sterile female worker. By keeping these cloned males on hand, M. ibericus ant colonies can live in places that lack M. structor. This trick is “a bit mind-bending,” says Chris Smith, an evolutionary biologist at Utah State University.
Bizarre discovery of interspecies cloning “almost impossible to believe,” biologists say