Can plants hear their pollinators?

Francesca Barbero, a professor of zoology at the University of Turin, and her collaborators -- an interdisciplinary mix of entomologists, sound engineers, and plant physiologists from Spain and Australia -- studied these signals to develop noninvasive and efficient methods for monitoring pollinator communities and their influences on plant biology and ecology.

Barbero will present her findings and their impacts on Wednesday, May 21, as part of the joint 188th Meeting of the Acoustical Society of America and 25th International Congress on Acoustics, running May 18-23.

"Plant-pollinator coevolution has been studied primarily by assessing the production and perception of visual and olfactory cues, even though there is growing evidence that both insects and plants can sense and produce, or transmit, vibroacoustic signals," said Barbero.

Barbero and her collaborators played recordings near growing snapdragons of the buzzing sounds produced by a Rhodanthidium sticticumbee (sometimes called a snail-shell bee) to monitor the flowers' reactions. The researchers found that the sounds of bees, which are efficient snapdragon pollinators, led the snapdragons to increase their sugar and nectar volume, and even alter their gene expression that governs sugar transport and nectar production.

The flowers' response may be a survival and coevolution strategy, especially if the plants can affect the time pollinators spend within their flowers to increase their fidelity.

"The ability to discriminate approaching pollinators based on their distinctive vibroacoustic signals could be an adaptive strategy for plants," said Barbero. "By replying to their proper vibroacoustic signal -- for instance, an efficient pollinator's -- plants could improve their reproductive success if their responses drive modifications in pollinator behavior."

While it's clear that buzzing sounds can trigger plants' responses, it's less clear whether plant acoustics can also influence insect behavior -- for example, whether sounds from plants can draw in a suitable pollinator.

"If this response from insects is confirmed, sounds could be used to treat economically relevant plants and crops, and increase their pollinators' attraction," said Barbero.

The team is conducting ongoing analyses comparing snapdragon responses to other pollinators and nectar robbers.

"The multitude of ways plants can perceive both biotic factors -- such as beneficial and harmful insects, other neighboring plants -- and abiotic cues, like temperature, drought, and wind in their surroundings, is truly astonishing," Barbero said.

The project, "Good Vibes: How do plants recognise and respond to pollinator vibroacoustic signals?" (grant RGP0003/2022), is funded by the Human Frontier Science Program and is a collaborative effort between the University of Turin, I²SysBio in Valencia, and the Centre for Audio, Acoustics and Vibration at the University of Technology Sydney.