Researchers from the University of Montpellier published a paper in Nature earlier this month that reveals a species of ant can lay eggs from two distinct species.
A Messor ibericus worker ant, Adobe Stock
It has long been assumed that all animals, apart from hybrids like a mule which are sterile, will have offspring of their own species. This study proves that assumption wrong, at least in the case of the Messor ibericus, a species of ant, expanding our knowledge of hybridization and reproduction.
The ant species is xenoparous, meaning they give birth to other species as part of their life cycle. M. ibericus queen ants can produce hybrid ants that are both M. ibericus and M. structor, two species of ants that diverged approximately five million years ago. This is about the same period as the human-chimp divergence, said Johnathan Romiguier, an author of the paper.
Ants create hybrid workers
Hybridization in ant colonies is not unusual. Many queen ants mate with males from another species to produce hybrid workers. The hybrid workers are usually sterile, but as their role is to work, not reproduce, that is not a problem. Hybrid workers may be stronger and healthier than purebred ants, and some queen ants who reproduce with their own species can only produce other queens, meaning they must hybridize to create worker ants.
However, this case is unusual because some M. ibericus colonies with hybrid workers are hundreds of miles from the closest M. structor colony, making sexual mating between the species impossible. As well as hybridization, the team found that these queens can create purely M. structor male ants.
The team began DNA testing M. ibericus colonies, finding that 11.5% of ants in the colony M. structor drones living in the colonies. However, all of the ants in the colonies — including the non-hybrid M. structors — had mitochondrial DNA from M. ibericus. Mitochondrial DNA is inherited from the mother, meaning the M. ibericus, M. structors and the hybrids all had M. ibericus mothers.
Not just hybrids – this queen lays eggs of a different species
Next, the team isolated M. ibericus queen ants and studied their eggs. They found approximately 10% of them were purely M. structor.
The study concluded that M. ibericus ants could produce hybrid worker ants and clone M. structor males, whose sperm they use to create more hybrids. The queen ants clone males in one of two ways: with the fertilization of an egg without a nucleus or by the elimination of the maternal genome after fertilization. The cloning of males of their own species has been observed in several ant species, but never the cloning of a male from a different species.
This phenomenon was only seen in the M. ibericus ants, not in the other four species the team studied.
