To thrive, ant colonies rely on everyone pulling their weight. For raider ants, this means diligent scouts track down other nests, then direct hundreds of savage foragers to attack. They return with pincers gripping dead young ants to feed the settlement. Clones are produced. The colony thrives.
But raider ants are among about 50 species plagued by impostors: parasitic ants that resemble queens. They greedily eat the colony’s food, but shirk their own foraging duties, and can only hatch more parasites instead of workers when they reproduce. How the fake queens emerge has long puzzled scientists.
“It’s a real mystery how these things arrive,” said Ken Ross, an evolutionary geneticist at the University of Georgia.
A new study offers a solution. A “supergene” that mutates rapidly, between a single generation of raider ants, is likely responsible for the royal impostors. The discovery arose from an observation in a lab at Rockefeller University, where Waring Trible and his graduate adviser, Daniel Kronauer, studied raider ants.
“These weird, mutant queens just showed up,” said Trible, now at Harvard University, who led the study. Isolated from the rest of the colony in a petri dish, it was plain to see: Several of the ants had wings.
It’s a typical trait for queens in many species, but it was odd because raider ants don’t normally have wings, or queens.
“Seeing these winged females was very shocking, very striking, right away,” Trible said. “I immediately thought it was something genetic.”
He set about sorting through the 10,000-ant colony. His needle-in-a-haystack search found a total of 14 impostor queens, which he then let reproduce. Their progeny were always the winged parasites.
Trible and his colleagues devoted years to studying the mutants and trying to figure out their origin. Another geneticist, Sean McKenzie, compiled the regular ants’ whole genome, while Trible analysed the mutants’ genome. Comparing the genomes let Trible see where the regular and mutant ants differed. — NYT
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