The gardening bug | Environment| All topics from climate change to conservation | DW | 12.02.2018
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Natural phenomenon

The gardening bug

Agriculture is often viewed as the basis of human civilization. But there are some other — rather unlikely — farmers out there in the animal kingdom.

From ancient Egypt and China to the Babylonians and the Olmecs: agriculture played a key role in the development of human civilization all around the world. At first glance, the cultivation of food would seem to be a uniquely human trait. But as it transpires, there are other animals out there who grow their own food too.

Perhaps surprisingly, they aren't the most intelligent or highly developed species in the animal kingdom. You'd be hard-pressed to find a chimp, dolphin or elephant farming their food. But you will find thousands of bug species that do.

A case in point are the ambrosia beetles. There are about 3,000 different known species of these bugs but they all have one thing in common: their symbiotic relationship with their sole source of nourishment, the ambrosia fungi.

So what does all this have to do with agriculture? Well, the modus operandi of these bugs, which are often only a few millimeters in size, is to dig tunnels in the wood of sick or dead trees.

Once their galleries — as these tunnels are called — are established, the insects sow the spores of ambrosia fungi. The bugs carry these spores in specially-adapted compartments on their bodies known as mycangium.

Ambrosiakäfer (Imago/blickwinkel)

Ambrosia beetles can be tiny, often just a few milimeters. But they are avid gardeners

The fungi take root and grow, extracting nutrients from the wood. Meanwhile, the insects tend to their fungal crop like careful gardeners, even controlling the tunnels' humidity.

The bugs feed on the fungi, which in turn rely on the beetles for transport to new suitable habitats and favorable living conditions. When the beetle larvae are all grown up and ready to venture out into the world on their own, they gather as many spores as they can carry to seed a fungal garden in a dead tree of their own.

Beetle and fungus: neither has ever been found anywhere without the other.

This may all seem quite exotic, but ambrosia beetles are far from alone in their passion for gardening. Leafcutter ants grow fungi as well, as do some termites — although, unlike the ambrosia beetle, none live exclusively from their crop.

And in case you still think we humans were incredibly innovative when we started growing crops and domesticating animals some 10,000 to 15,000 years ago, consider the termite. These insects have been growing fungi for a whopping 31 million years. Kind of humbling, isn't it?


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