7.1 Alarm!

A 2019 study examined a plant called Solidago altissima. When attacked by herbivorous insects, the plant releases volatile chemicals that activate defensive responses in nearby plants of the same species.

When researchers compared populations frequently exposed to insects with those rarely attacked, they observed something surprising: in the heavily exposed populations, the chemical signal triggered defenses in all neighbouring plants, while in the less exposed populations the effect appeared only in closely related individuals.

Does Solidago “decide” whom to warn depending on how serious the danger is?

Or did different evolutionary histories select communication strategies that are more “open” or more “selective”?

When the risk is low, does it only “warn family”, and when the risk increases does it “decide” it’s better to alert everyone?

Is this extraordinary behaviour evidence of intelligence — or the result of an automatic biochemical mechanism?