Mycorrhiza of the fungus Rhizophagus irregularis. (Photo courtesy of Loreto Oyarte Galvez.)
A new study suggests that plants may benefit from hiding signs of impending danger from each other rather than warning of it, or even misleading each other about the absence of danger.
“Plants can benefit from dishonest signalling by harming their local competitors, misleading them and forcing them to spend resources on defences against herbivores,” said lead author Thomas Scott, an evolutionary theorist at the University of Oxford. “Our findings suggest that plants are more likely to act deceptively towards their neighbours than to be altruistic.”
Previous research has shown that when one plant is attacked by herbivores or disease, its neighbors can activate their own defense responses, which can include producing chemicals that make the plant toxic or less attractive to herbivores or insects. These defense responses are energy-intensive, so plants will not activate them unless absolutely necessary.
However, supporting one's neighbors makes no sense from an evolutionary perspective, since plants are constantly competing with each other for sunlight and nutrients.
For the study, published Jan. 21 in the journal PNAS, the scientists modeled the evolutionary plausibility of plants acting altruistically and compared it with the likelihood of signaling for other reasons. Their mathematical models explored various hypothetical scenarios to identify situations that might prompt them to warn their neighbors of a threat.
The researchers concluded that it is much more evolutionarily advantageous for plants to deceive about being attacked, sending distress signals even when all is well and misleading their neighbors into wasting their resources.
Illustration of the symbiotic relationship between a plant and a fungus in a mycorrhizal network.
Plants are able to exchange information through a vast underground fungal network that connects their roots, called the mycorrhizal network — sometimes called the “web of trees.” According to the research organization Society for the Protection of Underground Networks (SPUN), between 80% and 90% of all plant species are connected to a mycorrhizal network.
These fungi form symbiotic partnerships with plant roots, whereby the plants receive nutrients and the fungi receive carbohydrates produced by the plants through photosynthesis. The study suggests that information about plant resources can be transferred through these networks.
The research team offers two explanations for why previously observed distress signals might have originated from plants. The first is
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