Friday Fungus: Meeting the farming insects...

Ambrosia beetle farms (which you don't really want on your fig tree)

There are several insects that have, over the millenia, developed the intensive farming of fungus. And it all makes for a fascinating story:

Skinny lines of ants snake through the rainforest carrying leaves and flowers above their heads--fertilizer for industrial-scale, underground fungus farms. Soon after the dinosaur extinctions 60 million years ago, the ancestors of leaf-cutter ants swapped a hunter-gatherer lifestyle for a bucolic existence on small-scale subsistence farms. A new study at the Smithsonian Tropical Research Institute (STRI) in Panama revealed that living relatives of these earliest fungus-farming ants still have not domesticated their crop, a challenge also faced by early human farmers.

All of which suggests that said insects aren't really all that hot at this farming lark (although by 'non-domesticated' we don't really mean wild but rather that the ants still have the fngal equivalent of crab apples despite that 60 million years of farming said mushrooms). Hence:

"We found that the selfish interests of more primitive ancestors of leaf-cutting ants are still not in line with the selfish interests of their fungal partner, so complete domestication hasn't really happened yet."

That being said, the leaf-cutter ants have a complex and sophisticated farming system that acts to minimise the production of fruiting heads (mushrooms to you and I) in favour of producing more of the hyphae that the ants actually eat.

So can we learn anything from these insect farmers? In some ways we can although mostly by reinforcing the value of long-established faming and crop management techniques. Here's some European research into ambrosia beetles:

Initial observations suggest ambrosia beetles plant different fungus varieties in a specific order, similar to crop rotation strategies employed by human farmers. They also utilize bacteria to promote the growth of their fungal crops and to combat pathogens.

"It was also really surprising to find out that in the fruit-tree pinhole borer, the ambrosia beetle species that I mainly study, the major fungus crop consists of a single strain that can be found across the whole of Europe," said Biedermann. "Humans also grow a few very successful cultivars of their crops."

These beetles lug around the spores for the fungus, caputure and use bacteria that kill off damaging pathogens and are careful to protect the interest of their farming environment, the host tree. This last point is perhaps a lesson to us humans in that the beetles that make their homes on living trees don't crop fungus:

'Another fascinating result was that fungi are only found in beetles that colonise dead trees. Beetles that dwell in trees that are still alive do not carry fungi as they would probably kill their host tree.’

The beetles also make use of endophytes - microorganisms that live in plant tissue and repel herbivores - to protect their gardens. And in a fun way the beetles experiment with naturally occurring anti-biotics to further protect and enhance their gardens.

We've barely scratched the surface of what we can learn from insects and the things we can extract from the bizarre world of fungi.

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