Xeno-partying Ants 

A new study has discovered that Iberian harvester ant queens (Messor ibericus) are capable of laying eggs that hatch into an entirely different species.  

This phenomenon, researchers believe, likely involves cloning and defies biology, prompting scientists to rethink the very concept of species.  

It works like this: When M. ibericus mate with males of the builder harvester ant (Messor structor), the M. ibericus queens store the M. structor male’s sperm, then use it to fertilize some of the eggs they lay, Smithsonian Magazine explained. M. ibericus and M. structor, while belonging to the same genus, are different species that diverged over five million years ago. 

There are a few examples of other animals, including ants, that mate with other species. But this research is made more extraordinary by the fact that this queen lays eggs of her own species and that of M. structor. 

“It’s an absolutely fantastic, bizarre story of a system that allows things to happen that seem almost unimaginable,” Jacobus Boomsma, an evolutionary biologist not involved in the research, told Nature. 

To conduct the study, researchers dug up various M. ibericus colonies from farm roads near Lyon, France, trying to find male ants. However, males are difficult to spot as there might be very few even in a colony of 10,000 ants.  

They were, in the end, able to find 132 males from 26 M. ibericus colonies. About half of those were nearly hairless, which is a hallmark of M. structor, while the others were covered in dense hair, a typical trait of M. ibericus. DNA testing confirmed that the hairy males were M. ibericus, while the bald ones were M. structor. 

The males of both species shared M. ibericus mitochondrial DNA, which comes from the mother, indicating they were all born from M. ibericus queens. However, when researchers analyzed their nuclear DNA, which comes from the father, they noticed the father was an M. structor, El País explained.  

Researchers coined the term “xenoparty” to describe this behavior, which means “foreign birth.” 

The team wanted to go observe this phenomenon in action, so they raised colonies in the lab, hoping to observe births of M. structor ants from an M. ibericus queen. 

“It was very difficult, because in lab conditions, it’s nearly impossible to have males,” study co-author Jonathan Romiguier told New Scientist. “We had something like 50 colonies and monitored them for two years without a single male being born. Then we got lucky.” 

With three M. structor born in the lab, the evidence was striking: M. ibericus queens produce males of both species. The only plausible explanation seems to be that the queen ants are cloning the M. structor males from sperm stored in a specialized organ, the spermatheca. The resulting eggs are almost totally free of M. ibericus DNA – except for mitochondrial DNA. 

Moreover, by producing males of two species, the queen guarantees that her daughters, those that become queens, can mate with either species. They use M. ibericus sperm to make new queens, while M. structor sperm serves to produce hybrid workers and new M. structor males.  

This biological feature ensures that M. ibericus always has plenty of workers, who take care of crucial tasks within the colony, such as building the nest, gathering food, and raising the larvae. 

At the same time, the clonal M. structor males need M. ibericus queens to reproduce and hybrid workers to survive, as there is no proof of M. structor mating with members of their own kind.