A species of ant found scurrying across southern Europe is the first animal found that clones males of another species.
In a discovery that rewrites the rules of reproduction, scientists have found that queen ants in southern Europe can generate male clones of an entirely different species. The finding challenges long-held assumptions about species barriers and reveals a reproductive system unlike anything ever seen before.
The species at the center of this phenomenon is the Iberian harvester ant (Messor ibericus). In these colonies, all workers are hybrids, created when queens mate with males from a related species, Messor structor. Without this cross-species fertilization, colonies cannot survive. But researchers were puzzled to find thriving M. ibericus colonies in regions where no M. structor ants existed.
“That was very abnormal — kind of a paradox,” said Jonathan Romiguier, evolutionary biologist at the University of Montpellier and co-author of the study, published September 3 in Nature.
The answer proved extraordinary. Instead of relying on outside males, the queens were laying eggs that developed into M. structor males themselves. These males then fathered the hybrid workers needed to sustain the colony.
It’s the first recorded instance in the animal kingdom of one species routinely producing offspring of another species as part of its life cycle. The team has dubbed this strange system “xenoparity” — literally, “the birth of another.”
Initially dismissed as impossible, the evidence piled up. Researchers sequenced DNA from males in dozens of colonies and confirmed that some carried the mitochondrial DNA of M. ibericus queens, despite being genetically M. structor. In controlled lab colonies, they watched queens produce males of both species — sometimes within the same brood. Roughly 9% of eggs carried M. structor DNA, with the queen contributing none of her own nuclear material.
“It was almost like science fiction,” said Denis Fournier, an evolutionary biologist at the Free University of Brussels, who was not involved in the study. “Most of us learn that species boundaries are firm, yet here is a system where ants cross them as part of normal life. It’s jaw-dropping.”
Scientists think this reproductive trick evolved sometime in the last 5 million years, after M. ibericus and M. structor split on different evolutionary paths. Why it developed remains a mystery, though it may have been a way to sidestep “royal cheater” genes in M. ibericus males, which bias reproduction toward producing only queens instead of workers.
For now, researchers are trying to unravel the mechanism: at what point does the queen’s genetic material get erased, and how exactly does the cloning process work?
“This discovery is a great reminder to stay open to the unexpected,” Fournier said. “Now that we know such a system is possible, other strange findings in nature may suddenly make sense.”