Long before flowers painted the planet in brilliant colors, some of Earth’s earliest plants were glowing—not with pigment, but with heat. A new study from the lab of OEB’s Naomi Pierce and MCB’s Nicholas Bellono, led by former graduate student and now junior fellow Wendy Valencia-Montoya, reveals that ancient cycads used infrared radiation—an invisible form of warmth—to attract their beetle pollinators. The work, published in Science (PDF), uncovers what may be the most ancient form of plant–animal communication ever described.
“Infrared radiation is an ancient pollination signal,” says Valencia-Montoya, who was spotlighted in a feature story last summer. “Long before flowers evolved color and scent, plants and insects were already communicating through heat.”
The discovery began years ago in the Amazon rainforest, where Valencia-Montoya worked with the World Wildlife Fund studying endangered plants and beetles. “I was fascinated by how these beetles always seemed to find the right plants—even when there were no flowers, no color, no obvious scent,” she recalls. “That curiosity led me to cycads, the oldest living seed plants on Earth.”
A Hidden Heat Signal
Cycads, with their palm-like leaves and large cones, first appeared more than 250 million years ago—long before the rise of flowering plants. Working in the field, Valencia-Montoya and her collaborators measured the surface temperatures of cycad cones over several days. They found a striking pattern: male cones heated up first, followed hours later by females, following a precise circadian rhythm.
When the cones warmed up, they emit infrared radiation that beetles can sense from afar. Using infrared cameras, the researchers observed swarms of beetles converging on the “glowing” cones as they warmed, then departing when the heat faded. Laboratory experiments confirmed that the insects were responding not to scent or humidity, but to warmth alone. Artificial 3D-printed cones, heated to match the temperature profiles of real ones, successfully lured beetles even without any chemical cues.
The Molecular Basis of Infrared Detection
To uncover how the beetles sensed these invisible signals, the team combined microscopy, molecular biology, and electrophysiology. They discovered that the insects’ antennae are tipped with microscopic heat-sensing microscopic organs packed with neurons tuned to subtle changes in temperature.
At the molecular level, a protein called TRPA1 acted as a thermal switch, activating when the beetle detected the specific temperature range of its host plant. “Each beetle species has a slightly different version of this gene,” Valencia-Montoya explains, “and those differences are tuned to the heating patterns of the plants they pollinate.”
This mechanism also highlights an intriguing case of convergent evolution: snakes and mosquitoes use similar TRPA1 channels to detect infrared radiation from their prey or hosts. “What’s remarkable here is that infrared sensing evolved not for hunting or defense,” she says, “but for cooperation—plants and beetles working together to reproduce.”
The Earliest Chapter in Pollination
By comparing the thermal and molecular data from modern cycads with fossil records, Valencia-Montoya and colleagues found evidence that heat production by plants and infrared signaling predates the evolution of colorful flowers. As pollinators like bees and butterflies became more abundant and developed more elaborate, trichromatic color vision, plants shifted from heat-based cues to visual pigments—a transition that reshaped ecosystems worldwide.
“We think of pollination as a story of color and scent,” says Valencia-Montoya. “But our findings reveal an even older chapter—one written in signals hidden to human perception.”
The team also found an evolutionary trade-off: plants that invest energy in producing heat tend not to produce bright colors, and vice versa. “It’s as if nature had to choose between glowing and painting.”
Following Curiosity from the Rainforest to the Lab
For Bellono, whose lab studies how organisms sense and respond to their environments, Valencia-Montoya’s journey reflects the heart of scientific discovery.
“This is an amazing story of one dedicated person following her deep curiosity about nature from a childhood age,” says Bellono. “Wendy grew up in Colombia and then worked in the Amazon with beetles and cycads long before she planned on a career in science. Then she came here to study this interesting interaction, with no idea what she’d find or what the blueprint for a study would be. She went out into the field, made observations, brought her findings back to the lab for rigorous molecular investigation, and then leveraged all this information together with evolutionary analyses to reveal one of the oldest pollination signals uniting plants and animals, essential to terrestrial life. It’s an exciting study with respect to both its breadth and depth—a testament to Wendy’s curiosity, persistence, collaborative nature, and open-minded thinking.”
Pierce, whose lab has long explored the evolution of plant–insect interactions, sees Valencia-Montoya’s study as a landmark example of integrative biology.
“Wendy has done a fabulous, multi-dimensional project that represents a true collaboration between OEB and MCB—from identifying and determining the function of the exquisitely tuned TRPA1(B) receptors in the beetle pollinator’s antennae to surveying the evolution of thermogenic plants across the tree of life,” she says. “Wendy shows how metabolically expensive it is for ancient gymnosperms like cycads to produce infrared pollination signals, and how this is reflected in the trade-off between the rather drab, heat-producing cones and spathes of thermogenic plants to the brilliantly colored flowers that are characteristic of most of the flowering plants we see today. It’s a rare scientist who can traverse with ease both the molecular and the evolutionary ends of the biological spectrum, and it’s just thrilling to see all of this come together in a single article.”
Standing in a rainforest clearing surrounded by cycads and their beetle visitors, Valencia-Montoya says she still feels that same sense of wonder that started it all. “When you watch them at dusk, it feels almost magical,” she says. “We discovered an additional cue in the astonishing sensory world of pollinators. This one is even more special as it is one of the oldest pollination mutualisms, the relatives of both these plants and insects have been interacting and evolving together for hundreds of millions of years.”
Beetle pollinators are attracted to the warm glow of cycad plants in this potential cover submitted by the Bellono Lab. Artwork by Lillian Soucy.
