Biologists have long assumed a simple rule: a female produces offspring of her own species. It basically goes without saying; and yet, Messor ibericus has different ideas.
Its queens lay two kinds of sons, one that looks like their own species, and another that is genetically and physically part of a different species, Messor structor. This phenomenon is so striking that researchers have coined a new term for it: xenoparity, meaning “to give birth to the foreign.”
How Does This Even Happen?
Jonathan Romiguier and colleagues at the University of Montpellier weren’t looking for sci-fi scenarios when they began studying European harvester ants. But their genetic surveys kept turning up with some weird results. Across southern Europe, they found worker ants that were hybrids, containing both ibericus and structor genetic material. Stranger still, these hybrids appeared in regions where M. structor males didn’t even live.
In some places, the two species coexist. This has given M. ibericus queens an abundant supply of M. structor males to mate with. This seemed to be the most likely explanation for what Romiguier’s surveys were showing. But it couldn’t explain why these hybrids appeared in areas where structor males didn’t live.
So, the researchers took colonies into the lab to observe them, and that’s when they found out what was really happening. From a single queen, they watched two very different males crawl out of the same nest: a hairy ibericus and a nearly hairless structor. Genetically, both were sons of the same queen. The queen wasn’t just raising her own species, she was literally producing another one. She was essentially cloning males from another species.
This is even more bizarre because the two species diverged more than five million years ago. That’s about as far away as humans and chimps. But the oddities don’t even stop there.
When the researchers put the structor males created by the ant queen into a regular structor colony, they were killed. The reason was that although they were genetically similar, they carried the pheromones of their ibericus cousins, and for ants, pheromones are a strong language.
Why (and How) Do the Ants Do This?
This is the first time a female of one species has been observed cloning members of another. But the ibericus queens seem to have a good reason for this. Whenever they mate with ibericus males, all of the offspring become queens. This seems to be a genetic quirk of the species to ensure that queens are always available, but it also raises a problem: you can’t have a colony with all queens, you need workers too.
Breeding with other species seems to circumvent this, and structor was the closest option. But what happens when you don’t have a structor male around? Well, apparently, you just make your own. The structor males are permitted to stay in the ibericus colony and then mate with the queen. Yep, the queen mates with the offspring from another species that it itself has delivered and that’s not a sentence I thought I’d ever write.
But the more stunning thing is how they do it.
Cloning (producing genetically identical offspring) isn’t all that rare in the insect world. But these queens take it further. Instead of simply copying themselves, they use a trick called androgenesis, a kind of genetic sleight-of-hand that lets them clone another species.
Normally in ants, males come from unfertilized eggs and carry only their mother’s DNA. But in Messor ibericus, something different happens: when the queen lays an egg, the DNA material is somehow jettisoned. The queen uses sperm it has previously stored from structor and this sperm takes over, providing the sole nuclear genome for the embryo. The result is a male that is genetically structor but still carries ibericus mitochondria, as mitochondria is genetically inherited from the maternal side.
This also perfectly explains what researchers were observing in the field.
What Even Is a Species Anymore?
It’s easy to dismiss this as some bizarre thing that some ants do, but it’s so stunning it challenges our very idea of what an individual species is. You can look at it as a single colony which functions as a two-species superorganism, with each species locked into the other’s lifecycle. But you can also look at it as a form of domestication, with ibericus queens seemingly creating docile structor males and using them only for breeding. The researchers even found that these cloned males are morphologically distinct from wild structor—slimmer, hairless, genetically uniform.
This can even be compared to how mitochondria came to be in the first place, which is the result of an ancient symbiosis: free-living bacteria took up residence inside larger cells, and over time became permanent power-generating organelles. In both cases, a foreign genome is not just tolerated but integrated into another life form’s reproductive cycle.
In the end, it’s a poignant reminder that there’s very much we don’t know about the animal world, and the world of insects in particular. Just when we’ve grasped the basic rules of biology, ants quietly show us exceptions beneath our feet. They remind us that evolution is less a rigid code and more a restless tinkerer, forever inventing strange new ways of life.
The study was published in Nature.
