Sexual domestication: ants that clone another species to survive

[Press release] - Published on September 4, 2025 in Press Room, Science-Society

Life has always seemed to follow a simple rule: an individual can only give birth to individuals of its own species. However, a recent discovery shows that there is now an exception to this fundamental principle. In Messor ibericus harvester ants, females must produce individuals of two different species. In addition to producing males of their own species to father future queens, they must also clone males of another species to produce all the workers. This is the first known case of a species that must clone another species to ensure its survival.

This work is the result of five years of research at the University of Montpellier. It involved sampling more than 120 populations across Europe, sequencing nearly 400 individuals, and carefully observing around 50 colonies in artificial nests in the laboratory. These analyses and observations demonstrated that males born to the same mother belonged to different species, with completely distinct genomes and morphologies. The genomes of these two "brothers" show differences comparable to those observed in species that have been separated for more than 5 million years. The number and presence of hairs are often decisive criteria for differentiating between ant species, and here again, the difference is extremely striking for two individuals from the same mother: one is extremely hairy, while the other is almost hairless.

The phenomenon of sexual domestication

How could such an unprecedented situation, involving two brothers of different species, have evolved? Everything suggests that it is the result of a phenomenon that is new to science: sexual domestication. Among harvester ants, it is not unusual for a queen to practice what is known as sperm parasitism. This form of parasitism involves using the sperm of males from another species to produce her workers. This mode of reproduction has one major drawback: like hunters who depend on their prey for survival, queens must hunt down males of another species to exploit their sperm. But, just as humans domesticated livestock, they eventually mastered the reproduction of these males that they once exploited in the wild. This domestication of males was made possible by their ability to clone a male of another species from its sperm alone. From generation to generation, it became possible to maintain a clonal line of males directly in their nest. Thanks to this line of domesticated clones, there was no longer any need to live in the same geographical area as another species. This is why Messor ibericus colonies can single-handedly produce millions of hybrid workers that have invaded the entire Mediterranean region. Noteworthy fact: just as a pig differs from its wild ancestor, the boar, domesticated clones differ morphologically and genetically from the so-called wild males found in colonies of their original species.

A new mode of reproduction

While humans have been able to artificially clone other species, until now there have been no known examples of animal species in which females naturally need to clone another species. In this study, it is proposed that these females be called xenoparous, a term meaning that they must produce individuals of another species as part of their life cycle. This introduces the concept of xenoparity (from the Greek xeno-, "foreign, different," and -parity, "to bear children, to give birth"), a word that defines this new mode of reproduction.

This discovery reveals a colonial life form of unparalleled complexity, with queens capable of giving birth to an incredible diversity of individuals, differing not only in caste or sex, but also in species. In evolution, organisms that were once separate sometimes unite to form a more complex entity, a phenomenon known as a major evolutionary transition in individuality. In the case of xenoparity, two species have become sexually interdependent within the same colony, illustrating how such a transition can occur through a process of sexual domestication.