Termite creates sustainable monoculture fungus-farming

Nov 20, 2009
Termitomyces mushrooms appearing on top of a colony of fungus-growing termites (photo: Z.W. de Beer)

(PhysOrg.com) -- Food production of modern human societies is mostly based on large-scale monoculture crops, but it now appears that advanced insect societies have the same practice. Our societies took just ten thousand years of (mainly cultural) evolution to adopt this habit and we are far from convinced that it is sustainable.

Farming ants and had tens of millions of years to evolve their fungus farming systems and here monocultures are apparently evolutionary stable. In a publication in the journal Science this week, researchers from the Laboratory of Genetics of Wageningen University and the Centre for at the University of Copenhagen take significant steps to resolve this puzzle.

The fungus-growing termites of the old-world tropics build impressive mounds consisting of thousands of workers and soldiers. These societies domesticated African Termitomyces mushrooms more than 30 million years ago and became obligatorily dependent on farming their own fungal food in their often gigantic nest mounds. The termite fungus-farming symbiosis had a single African rain-forest origin and now comprises ca 330 species. It is of major ecological importance for decomposition and mineralcycling.

A colony-founding termite queen and king normally do not acquire their first garden until they have raised the first workers. These helpers collect Termitomyces spores while foraging, together with the that they defecate in the nest to establish a garden substrate. These spores are amply available because the fungus gardens produce large mushrooms once a year on top of the termite mounds.

However, this farming practice offers a paradox: Evolutionary theory predicts that symbioses with multiple lineages per colony should be unstable, because these genotypes can be expected to compete for making mushrooms rather than collaborate to serve the termite farmers.

The inside of a colony of Macrotermes natalensis in South Africa. Fungus gardens are arranged in an interconnected network of chambers, each containing a mass of masticated plant substrate in which Termitomyces grows (photo: D.K. Aanen).

The new study shows that a very special mechanism is in place to prevent this from happening. All colonies from which multiple fungal samples were genetically analyzed contained only a single fungal in spite of gardens having been initiated from at least two and probably many more genetically different spores.

Duur Aanen, Koos Boomsma and their respective colleagues in Wageningen and Copenhagen show that genotypes that happen to be common in a garden, become even more common at the expense of rarer genotypes. This happens not because common genotypes are better direct competitors, but because they have a higher chance of having an identical genotype as neighbor. Every time this happens, such genetically identical mycelia merge, which enhances the efficiency by which they produce asexual spores that the termites eat and deposit in new garden material of the colony. This process of positive reinforcement makes every colony end up with a life-time commitment to a single fungal symbiont in spite of the population at large having many fungal genotypes.

More information: Aanen, D.K., De Fine Licht, H.H., Debets, A.J.M., Kerstes, N.A.G. Hoekstra, R.F. & Boomsma J.J. High symbiont relatedness stabilizes mutualistic cooperation in fungus-growing termites. Science 20 november 2009

Provided by Wageningen University

Explore further: Birds 'weigh' peanuts and choose heavier ones

Related Stories

Long-term co-evolution stability studied

Jun 27, 2006

U.S. biologists say the world's fungus-farming ants cultivate essentially the same fungus and aren't as critical to fungi reproduction as had been thought.

Farming and chemical warfare: A day in the life of an ant?

Nov 17, 2008

One of the most important developments in human civilisation was the practice of sustainable agriculture. But we were not the first - ants have been doing it for over 50 million years. Just as farming helped humans become ...

Scientists reveal ants as fungus farmers

Mar 24, 2008

It turns out ants, like humans, are true farmers. The difference is that ants are farming fungus. Entomologists Ted Schultz and Seán Brady at the Smithsonian’s National Museum of Natural History have published ...

Recommended for you

Birds 'weigh' peanuts and choose heavier ones

May 23, 2015

Many animals feed on seeds, acorns or nuts. The common feature of these are that they have shells and there is no direct way to know what's inside. How do the animals know how much and what quality of food ...

Estuaries protect Dungeness crabs from deadly parasites

May 22, 2015

Parasitic worms can pose a serious threat to the Dungeness crab, a commercially important fishery species found along the west coast of North America. The worms are thought to have caused or contributed to ...

An evolutionary heads-up—the brain size advantage

May 22, 2015

A larger brain brings better cognitive performance. And so it seems only logical that a larger brain would offer a higher survival potential. In the course of evolution, large brains should therefore win ...

Our bond with dogs may go back more than 27,000 years

May 21, 2015

Dogs' special relationship to humans may go back 27,000 to 40,000 years, according to genomic analysis of an ancient Taimyr wolf bone reported in the Cell Press journal Current Biology on May 21. Earlier genome ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.