In a sci-fi twist, ant queens defy evolution by cloning males of another species

The same queen of the Iberian harvester ant (Messor ibericus) gave birth to both a hairy male (Messor ibericus, left) and a hairless male (Messor structor, right), even though they belong to distantly related species (Image: Jonathan Romiguier, Yannick Juvé and Laurent Soldati)

In a find that is rewriting the textbooks, researchers have discovered that southern European queen ants can clone males from a wholly different species. The discovery, which was called "jaw-dropping" by researchers, defies conventional wisdom regarding the species divide and reproduction patterns in nature.

A baffling paradox leads to a breakthrough

Scientists investigating Iberian harvester ants (Messor ibericus) were perplexed when they detected successful colonies without any sign of Messor structor, a distantly related ant whose males are typically needed to support the colony. “That was very, very abnormal. I mean, it was kind of a paradox,” study co-author Jonathan Romiguier, an evolutionary biologist at the University of Montpellier, told Live Science. The team initially suspected a sampling error but identified 69 regions where this unusual pattern occurred.

Their investigation revealed that queen M. ibericus ants were laying eggs that hatched into male M. structor ants. These males then fertilised the queens’ eggs, producing hybrid worker ants. The findings, published on Sept. 3 in Nature, mark the first known case of any animal producing offspring of another species as part of its regular life cycle.

How do ants clone another species?
Ant colonies are highly structured societies where most members are sterile female workers. Queens typically mate once in their lives, storing sperm to produce future generations of queens, workers, and males. However, when M. ibericus queens mate with males of their own species, they only produce new queens. Scientists believe this is due to “selfish” male genes that prioritise producing fertile queens, known as “royal cheaters.” To bypass this genetic trap, the queens require sperm from M. structor males to generate workers.

The absence of M. structor colonies near many M. ibericus nests made this dependency puzzling. To resolve the mystery, researchers collected 132 males from 26 colonies and found that some had the genetic profile of M. structor despite being born in M. ibericus colonies. Mitochondrial DNA analysis confirmed that these M. structor males shared the same mothers as their M. ibericus nestmates. “This was the detail that made me realise that ‘maybe we are on to something very, very, very big,’” Romiguier said.

Further experiments supported the claim. Laboratory queens produced eggs containing M. structor DNA, and over 18 months, one queen was observed producing males of both species. The results showed that the queens were cloning M. structor males without passing on their own nuclear DNA.

Redefining reproduction and species boundaries
The research team has called this new reproductive process “xenoparity,” meaning “birth of a different species.” Denis Fournier, an evolutionary biologist and ecologist at the Free University of Brussels, who was not involved in the study, said the discovery “is almost like science fiction.” He told Live Science: “Most of us learn that species boundaries are firm, yet here is a system where ants regularly cross them as part of normal life.”

The cloning mechanism likely evolved sometime after M. ibericus and M. structor diverged around 5 million years ago, although the exact timing remains unclear. Researchers now aim to uncover how the maternal DNA is removed during the cloning process.

“This discovery is a great reminder to stay open to the unexpected,” Fournier said, adding that it could explain puzzling past observations in evolutionary biology. It also raises new questions about cooperation, conflict and dependency in nature — and suggests that species barriers may be far more flexible than scientists once believed.