Ants have been farming for at least 3 million years. New research suggests Fijian ants were the planet's first plant farmers.

As detailed in a new paper published in the journal Nature, the ant species Philidris nagasau has been nurturing Squamellaria plants and harvesting their fruit since the Pliocene Epoch.

The historic nature of the ant species' green thumb was revealed by analysis of Philidris nagasau's evolutionary history.

Squamellaria looks more like lichen than a plant. It grows in the crevices of tree bark, and the unassuming-looking Fijian ants hang out in the plant's hollow structures, the domatia.

"The story is unique," Brian Fisher, an entomologist and researcher at the California Academy of Sciences, told NPR. "We already have ants that disperse seeds, and have ants that feed plants, but we've never had a case where they farm a plant they can't live without."

Researchers have previously discovered ants that farm fungus and mealybugs. Many species seek shelter in the hollows of plants, but the Fijian ants were the first to involve themselves in the growing process.

Philidris nagasau worker ants carry seeds from adult Squamellaria plants and embed them in especially soft patches of bark on new trees. The ants ward off potential plant eaters and fertilizer the young Squamellaria plants.

For the ants, the payoff for their hard work is the plant's juicy fruit. When the plants mature and their fruits ripen, the ants feast.

Ants can nurture multiple plants on a single tree, with each plant supporting a colony.

"One often finds dozens of colonies, connected by ant highways, on a single tree," Guillaume Chomicki, a researcher at the University of Munich, said in a news release. "All of these individuals are the progeny of a single queen, whose nest is located in the center of the system."