Land plants can be connected to a complex, underground fungal network known popularly as 'the wood wide web." Networks emerge because mycorrhizal fungi form symbiotic partnerships with plant roots, through which the plants receive nutrients and the fungi receive carbon. It has been demonstrated that plant resources and information can be transmitted through the mycorrhizal network, and be used by other individuals.

Previous studies have found that, if a plant is attacked by a herbivore or pathogen, this often leads to other plants connected to the same fungal network upregulating their defense mechanisms. However, it has not been clear whether plants being attacked by herbivores actively signal through this network, to warn others to activate their defenses.

Active signaling between plants appears to contradict evolutionary theory, which suggests that this kind of behavior would only be favored when it provides a benefit to both the sender and the receiver of the signal. This presented a conundrum for researchers—why should a plant being attacked send signals to warn its neighbors?

To investigate this, a team of researchers led by the University of Oxford in collaboration with Vrije Universiteit Amsterdam, used mathematical models to investigate different hypothetical conditions. They found that it is extremely hard to find situations where plants would be evolutionarily selected to warn their fellows of impending attack. The likely reason for this is that plants compete with neighbors for resources such as sunlight and nutrients, and so do not benefit from helping neighboring competitors. In fact, the results indicated that plants can even be favored to signal dishonestly to harm their neighbors.