Long before colorful flowers emerged, some ancient plants attracted pollinators with heat, making them glow in infrared light. Recent research highlights how these plants, particularly cycads, heated up their cones during reproduction to signal nocturnal insects, like beetles, who could pick up on this warmth from a distance.
Today, cycads are rare and found mainly in tropical regions. Interestingly, they haven’t changed much over the past 200 million years. Wendy Valencia-Montoya, a cycad expert at Harvard, describes them as “dinosaur plants.” Their structure, producing both pollen and seeds in unique cones, makes them quite fascinating.
A couple of centuries ago, botanists first noted these plants could get noticeably warmer—up to 25 degrees Fahrenheit above the surrounding air. This process is metabolically demanding but serves to attract pollinators. Recent findings show that different cones heat up at distinct times, thus guiding insects toward them. Researchers even observed beetles responding to these temperature changes, confirming the attraction was real.
To deepen our understanding, Valencia-Montoya’s team used 3D printing to create fake cones heated with sand. Surprisingly, they found that even without direct contact, insects were drawn to the infrared glow of these replicas. This suggests the visibility of infrared light alone can guide pollinators, especially those with specialized antennae capable of detecting slight temperature variations, akin to the heat sensors in snakes.
Notably, this capability seems tailored to specific cycad species, indicating a deep evolutionary relationship. As Nicholas Bellono from Harvard notes, infrared radiation may be one of the oldest signals used in pollination, linking modern beetles to their ancient counterparts.
The interactions between plants and pollinators don’t just rely on visuals; it’s a complex dance of signals. As new pollinator species evolved, plants adapted their signaling methods, shifting from heat to color. This adaptability has allowed flowering plants to flourish with varied colors, transforming the landscape.
Roger Seymour, from the University of Adelaide, emphasizes that the findings offer significant insights into this ancient relationship. He suggests that the warmth could also serve as an energy source for insects, making the experience even more enticing for them.
Irene Terry, an ecologist at the University of Utah, adds that while scents—including sweet and spicy aromas—are important for attracting pollinators, this study beautifully highlights the role of infrared light. She points out that many insects, like mosquitoes, have adapted to use infrared for navigation, hinting at a much broader spectrum of visibility in the insect world that we can’t perceive.
Imagine being a prehistoric beetle guided by the warm glow of these ancient plants in the twilight. This infrared signal has persisted through millions of years, illustrating the enduring relationship between these plants and their pollinators. It’s a remarkable reminder of the complex history of life on Earth.
