PLANTS send out SOS signals when they are under attack. If insects are feeding on them, some plants emit volatile chemicals that attract enemies of the insects. What is surprising, though, is that neighbouring plants not being eaten also send out distress signals to call in these “bodyguards”.
Why so-called secondary signallers do it has been a mystery, but now Yutaka Kobayashi and Norio Yamamura of Kyoto University, Japan, think they have solved it.
The answer is family values, or in evolutionary parlance, kin selection. “My hypothesis views secondary signallers as crying for help to save their family,” says Kobayashi.…
