Queen ant makes males of one other species for daughters to mate with

Some of the eggs laid by Iberian harvester ant queens comprise males of one other species, the builder harvester ant – and these males father the entire staff within the colony.

“This statement sounds really, really crazy, like impossible,” says Jonathan Romiguier on the University of Montpellier in France. And but, he found, it’s true.

Romiguier turned intrigued by Iberian harvester ants (Messor ibericus) when he found that each one the employees in M. ibericus nests have been hybrids, with about half of their DNA matching that of the builder harvester ant (Messor structor).

The most certainly clarification, it appeared, was that M. ibericus queens have been mating with M. structor males. This sort of factor occurs in another ant species. No one is aware of why, however there are two competing explanations that look like most certainly. One is that hybrids of carefully associated species profit when the genes of every species compensate for a number of the different’s flaws, an idea often called hybrid vigour.

Another risk is that it would resolve a peculiar downside that M. ibericus shares with another harvester ant species: each time M. ibericus queens mate with M. ibericus males, all of their offspring turn out to be queens. This is likely to be because of a genetic quirk that ensures its personal inheritance however is devastating for the colony, which wants staff with a purpose to survive. Breeding with one other species could also be a method to circumvent this.

However, M. ibericus colonies happen in lots of areas throughout the Mediterranean area the place there aren’t any M. structor colonies, together with on the island of Sicily. Yet Romiguier and his colleagues did discover some odd-looking, hairless M. structor males in M. ibericus nests. So the place have been they coming from?

Genetic evaluation of the unusual males supplied a complicated clue. A tiny little bit of DNA that’s inherited solely from the mom, the mitochondrial DNA, in these structor males was the one bit that clearly belonged to M. ibericus, revealing their mom was an M. ibericus queen.

This prompt that an egg of an M. ibericus queen can comprise a male from one other species. To check this concept, Romiguier introduced dozens of M. ibericus colonies into his lab. “It was very difficult, because in lab conditions, it’s nearly impossible to have males,” he says. “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 males born within the lab, the proof was unmistakable: M. ibericus queens have been producing males of each species. The solely potential clarification for this seems to be that the queen ants are cloning the M. structor males from sperm saved in a specialised organ known as a spermatheca. The ensuing eggs are nearly solely devoid of M. ibericus DNA, excluding mitochondrial DNA, which is absent from sperm.

This additionally explains the place that M. structor sperm is coming from: by producing two species of males, the queen ensures that her daughters that turn out to be queens themselves can mate with males of each species. They use M. ibericus sperm to make new queens, whereas M. structor sperm is used to provide hybrid staff and new M. structor males.

There are a few examples from other animals – together with some ants, clams and stick bugs – the place a feminine’s eggs are hijacked by the sperm of a male from one other species, which eliminates the DNA from the egg and forces her to provide a person she is unrelated to. Yet this advantages solely the males. This is the one identified case of men and women from completely different species that depend upon one another to breed.

“The M. ibericus queens absolutely need their clonal males. Otherwise, they can’t have workers,” says Romiguier. And the clonal M. structor males want M. ibericus queens to breed and hybrid staff to outlive – there isn’t a proof they’re ever mating with their very own form.

Although the findings appear nearly unbelievable, they’ve satisfied different specialists. “The authors have done a very rigorous study of the ants in question,” says Nathan Lo on the University of Sydney. “Their results strongly support their conclusions.”

He suspects that as a result of the clonal males by no means combine genes with different lineages, they’re progressively accumulating unhealthy genetic mutations they can’t do away with. “So at some point the lineage may start to deteriorate, especially as environments change.”

Romiguier agrees that this peculiar state of affairs may ultimately collapse. But as a lot because it appears as if these M. ibericus females and M. structor males could have painted themselves into an evolutionary nook with their harmful liaison, for now, their tryst seems to be a hit – they’ve unfold all through the Mediterranean area, throughout huge areas the place M. structor colonies have by no means made it.

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