Sexual Domestication: These Ants Clone Another Species to Survive

[Press Release] - Published on September 4, 2025 in Press Room, Science and 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 this fundamental principle now has an exception. In the harvester ants Messor ibericus, females must produce offspring of two different species. In addition to producing males of their own species to sire 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 conducting detailed laboratory observations of about 50 colonies housed in artificial nests. It was only after these analyses and observations that it was demonstrated that males laid by the same mother belonged to different species, with completely distinct genomes and morphologies. The genomes of these two “brothers” indeed exhibit 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 key criteria for distinguishing between ant species, and here again, the difference is strikingly evident between two individuals that nonetheless share the same mother: one is extremely hairy, while the other is virtually hairless.

The Phenomenon of Sexual Domestication

How could such an unprecedented situation—two brothers of different species—have come about? Everything suggests that this is the result of a phenomenon new to science: sexual domestication. Among harvester ants, it is not unusual for a queen to engage in what is known as spermatophagous 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 track down males of another species to exploit their sperm. But, much like humans domesticating livestock, they eventually mastered the reproduction of these males that they once exploited in the wild. This domestication of the males was made possible by their ability to clone a male of another species from just his sperm. From generation to generation, it became possible to maintain a clonal line of males directly within their nest. Thanks to this line of domesticated clones, there is no longer any need to live in the same geographic area as another species. This is why colonies of Messor ibericus can single-handedly produce millions of hybrid workers that have invaded the entire Mediterranean region. Key fact: Just as a domestic pig differs from its wild ancestor, the wild boar, the domesticated clones differ morphologically and genetically from the so-called wild males found in colonies of their original species.

A New Mode of Reproduction

Although humans have been able to artificially clone other species, until now there were no known examples of animal species in which females would naturally need to clone another species. In this study, it is proposed to refer to these females as xenopares, a term signifying that they must produce offspring of another species as part of their life cycle. This introduces the concept of xenoparity (from the Greek xeno-, “foreign, different,” and -parity, “to give birth”), a term that defines this new mode of reproduction.

This discovery reveals a form of colonial life 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.