Thursday, 7 June 2007

Back again...Farmer Ants

Well, yes. I know it has been a while since I last wrote anything. But it has been a hectic past couple of weeks, so you must forgive me. But anyway, onto the post.

Rereading Carl Zimmer's 'Evolution: The Triumph of an Idea', which I have in the glorious illustrated edition, I came across a short section on Leaf-cutter ants. These ants it seems are the true original farmers, beating us by around 50-65 million years. They use an interesting system of ant-fungus mutualism, whereby the ants actively cultivate the fungus, much like the way we cultivate corn, wheat or any other crop plant. The fungus obviously gets the benefit of protection deep within the ant's nest, and they also get their nutrients brought to them. They have become so dependant on the ants, that they can no longer survive without them.

But what is the benefit to the ants, I hear you cry? Well, each day a host of big ants stream out of their nest across the rain-forest floor. Their goal; to collect leaves and other organic matter. Once collected, the big ants pass the plant matter to a smaller ants, who tear up the leaves. These are past to even smaller ants who chew the leaves further. This continues until the leaves become a fine paste which is then spread onto the fungus. The fungus breaks down the plant matter in a way the ants cannot. The ants however can harvest the most nutritious parts of the fungus.

But it doesn't stop there; they even have their own fungicides. You see, an entire beneficial fungus plantation can be wiped out by an infestation of fungi which attack their fungus. This is where the fungicide comes in. The ants have a thin powdery layer of a bacteria called Streptomyces. This bacteria produces compounds that kill off invading fungi. But the fungi can evolve resistance to the fungicide, in much the same way pests evolve resistance to our pesticides. But handily as the bacteria is also living, and thus also subject to evolution, it can mutate, keeping its ability to kill the unwanted fungi. We could do well to learn from this, as Zimmer puts it, "In other words, ants are using the laws of coevolution to their advantage, while we end up turning them against us".


1) Evolution: The Triumph of an Idea, p 204-207, Carl Zimmer, ISBN 0 434 00909 I
2) Wikipedia, Ant-fungus mutualism
3) Wikipedia, Leaf-Cutter ants


Max said...

Unfortunately any religous zealout will claim this system is too complex to have not been designed by God. Even as it serves as a compelling example of evolution.

Xander said...

True, but I've heard of religious zealots saying that if evolution is true, then 'in a couple of years a car will turn into a hot-air balloon'. So I don't think there's anything we could talk about that they wouldn't try to use to 'disprove' evolution.