Mutant, Parasitic Impostor Queens Lurk in Ant Colonies

To thrive, ant colonies depend on everybody pulling their weight. For raider ants, this implies diligent scouts monitor down different nests, then direct lots of of savage foragers to assault. They return with pincers gripping useless younger ants to feed the settlement. Clones are produced. The colony thrives.

However raider ants are amongst about 50 species tormented by impostors: parasitic ants that resemble queens. They greedily eat the colony’s meals, however shirk their very own foraging duties, and might solely hatch extra parasites as an alternative of employees after they reproduce. How the pretend queens emerge has lengthy puzzled scientists.

“It’s an actual thriller how this stuff arrive,” mentioned Ken Ross, an evolutionary geneticist on the College of Georgia.

A examine revealed Tuesday in Present Biology gives an answer. A “supergene” that mutates quickly, between a single era of raider ants, is probably going liable for the royal impostors. The invention arose from a shocking commentary in a lab at Rockefeller College, the place Waring Trible and his graduate adviser, Daniel Kronauer, studied colonies of raider ants.

“These bizarre, mutant queens simply confirmed up,” mentioned Dr. Trible, now at Harvard, who led the examine. Remoted from the remainder of the colony in a petri dish, it was plain to see: A number of of the ants had wings.

It’s a typical trait for queens in lots of species, nevertheless it was odd as a result of raider ants don’t usually have wings, or queens.

“Seeing these winged females was very surprising, very placing, instantly,” Dr. Trible mentioned. “I instantly thought it was one thing genetic.”

He set about sorting by means of the ten,000-ant colony. His needle-in-a-haystack search discovered a complete of 14 impostor queens, which he then let reproduce. Their progeny have been all the time the winged parasites.

Dr. Trible and his colleagues devoted years to finding out the mutants and attempting to determine their origin. One other geneticist, Sean McKenzie, compiled the common ants’ entire genome, whereas Dr. Trible analyzed the mutants’ genome. Evaluating the genomes let Dr. Trible see the place the common and mutant ants differed.

In each varieties of ants, one chromosome carries a set of genes which can be all inherited collectively and might management essential traits and features, referred to as a supergene. Common ants have one copy of the supergene and one other model that’s mutated and recessive. However the impostor queens have two copies of the mutated supergene.

“Such a mutation in people would possible kill you,” Dr. Trible mentioned. “The chromosome is so degenerated. It’s a extremely nasty mutation.”

However for these ants, what doesn’t kill them makes them develop wings.

It’s “overwhelmingly possible” that the supergene controls the expansion of impostor queens, however extra focused analysis is required to substantiate the discovering, Dr. Trible mentioned.

For many years, the widespread considering was that complicated traits or behaviors, corresponding to parasitism or the variety of queens in a colony, could be decided by the mixed affect of many genes, mentioned Dr. Ross, who found the primary supergene in ants and wasn’t concerned within the new examine. However scientists now know, he mentioned, that “there could also be plenty of genes, however they are typically locked up in supergenes.” Meaning complicated traits can depend upon only a single issue, “which is simply wonderful,” he mentioned.

Whereas scientists have recognized not less than 5 different ant supergenes, this may be the primary to regulate caste, or whether or not ants turn into employees, foragers or queens; the others have been tied to social conduct. Why ants turn into adults of a sure caste is an open query. This supergene seems to have eliminated the parasites’ means to be employees and permits them to play a task not sometimes discovered within the raider species.

“Isolating a caste-based mutant is a extremely highly effective instrument,” Dr. Trible mentioned. Mutants, he mentioned, might be an essential window into the in any other case black packing containers of evolution.

That is additionally the primary time parasitic ants of the identical species as their host have been noticed. Whereas there are various parasitic ants, till now they’ve been a separate species from their host, maybe evolving slowly over time from the unique species to turn into their parasite. The brand new examine reveals {that a} parasitic mutation can happen inside a species and throughout a single era, upending earlier hypotheses that such transitions take 1000’s of years or longer.

“It was a single step, nevertheless it wasn’t trivial,” Dr. Ross mentioned.