6 March 1999

Two to Tango

ALONE they’re nothing. Together, they’re the greatest double act in the
rainforest. The partnership between attine ants and the fungi that they grow in
their underground gardens is a huge success. Top billing goes to the
leafcutters, the most sophisticated of the Attini tribe. They remove more of the
vegetation in a tropical American rainforest than any other group of animals,
including mammals. Some experts estimate that leafcutters snip off as much as 20
per cent of the foliage a forest produces each year.

So what’s the secret of their success? Total commitment. The attine ants of
Central and South America and their fungal partners don’t just live together,
they have evolved together, each putting pressure on the other to change, to
improve the pair’s performance. Co-evolution has made ants and fungi

The first ant to take up fungus gardening probably accidentally discovered
that fungi growing on the bits of food it had stashed in its nest were more
nutritious than the food itself. It carried on bringing home rotting leaf
litter, not to eat but to feed the fungus, which it ate instead. Today there are
around 200 species of gardening ants. “Most still take stuff from the forest
floor: dead flowers, bits of decaying leaf, caterpillar poop,” says Ulrich
Mueller, an entomologist at the University of Maryland, College Park. The 20 or
so species of leafcutter have gone one stage further by harvesting fresh leaves,
stems and flowers.

The attines and their fungi form a true symbiosis, with both partners
benefiting from the relationship. The ants exploit a type of food they can’t
digest …


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