Trees talk to each other to create toxic defences

While out in Namibia - apparently not working on #OpenTox - but working on a new Caprivi Delta conservation project a couple of years ago, and while out gathering wood, I was told the story of the Mapone trees responding to the elephant migration through the region:

..."Interestingly this Mapone wood is also eaten by elephants. According to one of our guides, when the elephants start eating some trees, the trees send out signals to each other to make their leaves bitterer so that the elephants don’t want to eat them any more. Unfortunately that also makes them frustrated and they start knocking the trees over. But that also helps with collecting the wood!"...

  This topic of chemical adaptation and communication between trees seemed really fascinating to me, but I have not yet had time to validate the story with for example finding and reading a scientific study on how Mapone trees talk to each other. On another trip another contact informed me it was because there was an interesting meal (e.g., insects) in the tree tops, and that was the reason.

In any case I still have a little voice in my head telling me this phenomena of tree language would be fascinating to understand more and even develop models for in our computational science work.

So I was intrigued last night to stumble on a documentary on Arte on plant behaviour and they described a fascinating similar case of Acacia Trees talking to each other in South Africa. Animals such as Kudu eat the leaves of these trees. In a reserve area they were puzzled by the increased incident of unexplained sudden deaths of healthy-looking Kudus. They called in Wouter Van Hoven, a professor at Pretoria, and his group to study the problem. They found, that because of fencing, the Kudu were in higher numbers than usual in this area.

 

The trees in response to increased eating of their leaves release an ethylene gas to communciate with other trees in the neighborhood. In response to this message, the trees collectively increase the concentration of tannin in their leaves by a factor of four. What had been food previously to the deer is now with the increased toxic dose a poison. So the trees basically respond to the threat and kill the kudu and thus reduce their over-population. (Aside: This gives us another inspiring Tree use case for #OpenTox (see OpenTox) - can we predict that such an increase in dose kills the animal?)

So trees really do talk to each other. Perhaps they will have some conversations together to apply their wisdom to the relentless threat of global warming coming our way.

Barry

PS: If you are doing research in this fascinating area of biology I would love to hear from you!