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By Deborah Netburn

Los Angeles Times

Could ants get any cooler?

These amazing insects have been known to create rafts and bridges with
their bodies and tend to vast fungus gardens. Now, a new study
suggests they have also been farming plants for millions of years.

High in the trees of the island nation of Fiji, evolutionary biologist Guillaume Chomicki, a post-doc at the University of Munich in Germany, discovered a specialized community of ants that actively cultivate six
species of plants.

DNA evidence suggests this farming behavior could go back as far as 3
million years, he said.

To put that in perspective, the earliest known evidence of human
farming dates back to 23,000 years ago.

The ant-farmed plants are all members of the Squamellaria family, also
known as “ant-plants.” They are epiphytic, meaning they grow on other
plants, usually trees.

In a paper published Monday in Nature Plants, Chomicki describes how
the industrious ants, a species called Philidris nagasau, are involved
in nearly every aspect of the ant-plants’ life cycle.

Even before the Squamellaria’s fruit is ripe, the ants begin gathering
its seeds by cutting through the fruit’s wall. Next, the ants sow the
seeds in holes in the tree bark and guard them until they begin to
sprout.

When the seedlings reach about } of an inch high, they begin to
develop a soft, bulbous structure between the roots and the stem known
as a domatium or “ant-house.” As soon as the domatium is big enough,
the ants enter a cavity in it to defecate, providing the young plant
with much-needed fertilizer.

So, what do the ants get in return for all this attentiveness?

First and foremost, a place to live.

As the Squamellaria continues to grow, its domatium grows as well,
eventually getting up to 8 to 16 inches across and sometimes even
bigger. This structure is designed to be a perfect home to ants,
Chomicki said.

He described the inside as having “an incredibly complex system of interconnected galleries, which looks like a brain.”

All those folds maximize the nesting surface available to the ants.
That’s good for the ants and good for the long-term health of the
plant, Chomicki said. The more ants that live in the domatium, the
more ant-fertilizer the plant receives.

Some species of Squamellaria sweeten the deal for the ants even more
by providing sugar rewards that drip from their leaves.

Over the course of his research Chomicki said he never encountered
this species of ants not living in one of the six species of plants
that they were observed to cultivate, nor did he see the plants living
without the ants. That suggests the two organisms are now mutually
dependent, he said.

This is not the first time farming behaviors have been observed in the
animal kingdom.

The hairy chested-yeti crab that lives along hydrothermal vents deep
in the ocean, farms sulfur-oxidizing bacteria on the hair of its chest
and harvests it using a comb-like structure in its mouth.

Three-toed sloths in Costa Rica have been shown to encourage green
algae to grow on their fur to supplement their nutrient-poor leafy
diet.

And leaf cutter ants are well known for keeping vast fungal farms that
provide them with food.

However, Chomicki said the ant farmers of Fiji are the first known
ants to farm plants rather than fungus.

He added that there is still more he would like to learn about the
relationship between the ant farmers and their crops. For example, he
noticed that the ants only defecate in particular cavities in the
domatium. He suspects that the plant produces a chemical that tells
the ant where to do their business.

He’s also curious to learn more about the genes that allow the plants
to use the nutrients in the ant poop.

http://www.thedailyworld.com/news/ants-have-been-farming-plants-for-millions-of-years-long-before-people/

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