If only the plant had been better connected (Image: Stefan Ernst/Getty)

It is not just humans that like a natter with their nearest and dearest – plants pay most attention to their closest relatives.

When an insect bites a leaf, many plants release volatile chemicals to prime their neighbours for attack. The defences this triggers vary – some plants respond by attracting predatory insects that eat the herbivores, others make themselves less tasty.

Now Richard Karban of the University of California, Davis, has shown that for the sagebrush, responses to these warning signals can vary with relatedness.


At the start of three growing seasons, Karban’s team exposed different branches of the same plants to volatile chemicals. The substances came from relatives of the same species whose leaves had been clipped to trigger chemical release.

By the end of the seasons, herbivores had done less damage to the branches exposed to chemicals from close relatives than to those receiving signals from more distant relatives – the warning probably prompting the plants to release herbivore-deterring chemicals, says Karban.

He has previously shown that the blend of volatiles varies enormously between individuals – “so much so that big peaks in some individuals are undetectable in others”, he says.

However, there is some similarity between family members. Karban thinks this variability is being exploited by the plants as a kind of family-specific signature, to prevent eavesdroppers from listening in and to give those that share the same genes a greater chance of survival.

Some plants are genetically more resistant to being eaten than others, so it makes sense that plants should care more about their kin’s fate than that of the general population.

“It is very elegant work,” says Susan Dudley from McMaster University in Ontario, Canada, who has shown that plants competing for space in a small pot are less aggressive if they are related to their neighbours.

She thinks this kind of kin-recognition is probably common among many plants.

Journal Reference: Proceedings of the Royal Society B, doi: 10.1098/rspb.2012.3062