When we think about pollination, it’s easy to picture a bee or a butterfly covered in pollen, flitting from flower to flower in a dance of nature. However, if we take a step back in time, around 105 million years ago during the Cretaceous period, things were very different. Back then, bees, butterflies, and other insects we associate with modern pollination did not yet exist. Instead, most of the world’s terrestrial ecosystems were dominated by gymnosperms—non-flowering plants like pines, cycads, and firs. Surprisingly, these plants had their own pollination system in place, one that involved insects, albeit very different from those we see today.
An international team of researchers recently uncovered a groundbreaking discovery in the El Soplao cave in Cantabria, Spain. Within this cave, they found several amber-preserved flies that are believed to have fed on nectar and pollinated gymnosperms around 105 million years ago, providing a glimpse into a long-lost chapter of Earth’s ecological history. The study, published in the prestigious Current Biology, shines light on the symbiotic relationship between plants and insects in a time when flowering plants (angiosperms) had not yet fully taken over the planet.
Plants and Insects: An Ancient Symbiosis
Pollination, at its core, is a process of mutual benefit between plants and insects. Plants attract insects, often using sweet nectar as a lure, to transport pollen from one flower to another. This enables fertilization and ensures the continuation of plant species. In modern ecosystems, this process is dominated by flowering plants, with bees, butterflies, beetles, and flies playing vital roles in this exchange. However, in the Cretaceous period, things looked very different.
During the Cretaceous, gymnosperms were the dominant plant group. These plants, which include pines, firs, and cycads, are not flowers but produce seeds in cones, relying on the wind for pollination. While wind-pollination was the primary method for these plants to reproduce, it is now clear that insects, too, played a role in this ancient system.
As the discovery of these amber flies demonstrates, some insects during this time had a specialized role in the pollination of gymnosperms, though this was a far cry from the intricate relationships that exist between insects and flowering plants today. These new findings offer crucial insights into how pollination evolved and how it may have contributed to the eventual rise of angiosperms—the flowering plants that dominate the world today.
Flies: The Unsung Pollinators of the Cretaceous
The fossils found in the amber from El Soplao cave are remarkably well-preserved, providing an incredibly detailed look at life during the Cretaceous period. The research team identified two species of flies, belonging to the now-extinct family Zhangsolvidae, which is believed to have been wiped out long before the rise of dinosaurs. What makes these flies particularly interesting is their long, specialized proboscis—a feeding organ that allowed them to extract nectar from plants. This adaptation is particularly significant because it mirrors the behavior of modern-day hummingbirds, which also feed on nectar while hovering.
The presence of this specialized proboscis, preserved with such fine detail through computed tomography and transmission electron microscopy, provided the researchers with a unique opportunity to understand the feeding mechanisms of these ancient insects. The flies’ ability to feed from plants by approaching them in beating flight—similar to the way hummingbirds hover—demonstrates a form of pollination that would have been quite effective for gymnosperms.
What makes this discovery even more fascinating is that one of the flies was found with hundreds of pollen grains from Bennettitales, an extinct order of gymnosperms. These findings suggest that these flies were not only feeding on nectar but were actively involved in the pollination process, transferring pollen from one gymnosperm plant to another. This close relationship between these ancient flies and gymnosperms is a crucial piece of the puzzle for understanding how pollination worked in the Cretaceous period and how it may have contributed to the survival and reproduction of non-flowering plants.
The Transition to Angiosperms and the Role of Insects
During the Cretaceous period, the Earth was undergoing significant changes. The most notable was the rise of angiosperms—flowering plants that would come to dominate terrestrial ecosystems. However, during the time when the amber flies were active, angiosperms had not yet reached the dominance they would later achieve. Instead, gymnosperms continued to reign supreme, with insects like these amber flies filling a niche as their pollinators.
This discovery raises an important question: why have amber insects carrying angiosperm pollen not been found in similar fossilized states? The answer lies in the timing of the transition from gymnosperms to angiosperms. The researchers suggest that the fossils found in Cantabria represent a crucial moment in Earth’s history when the earliest insects were likely starting to adapt to pollinate flowering plants. While gymnosperms may have dominated the landscape, angiosperms were beginning their rise, and insects may have started to experiment with new types of plants as sources of nectar and pollen.
If these flies were already feeding on gymnosperms and transferring pollen in the Cretaceous, it stands to reason that the transition to pollination by insects in angiosperms was already underway at that time. This evidence provides a crucial link between the two plant groups, suggesting that the rise of angiosperms was not an abrupt event but rather a gradual process that saw the diversification of both plants and their insect pollinators.
The fact that these flies were feeding on gymnosperms while also possibly interacting with the early angiosperms signals the beginning of a new era of plant-pollinator relationships. The shift from wind-pollination to insect-mediated pollination likely played a key role in the evolutionary success of flowering plants, offering them more targeted and efficient means of reproduction. As the diversity of flowering plants grew, so too did the diversity of insect species adapted to pollinate them, eventually leading to the complex ecosystems we see today.
The Evolution of Pollination and Its Importance Today
The relationship between insects and plants is a foundational aspect of ecosystems worldwide. Pollinators such as bees, butterflies, and flies provide essential services to plants, ensuring the continuation of species and the diversity of life on Earth. In the present day, pollination supports the production of fruits, seeds, and plants that humans and animals rely on for food, shelter, and medicine.
However, this intricate web of life is now facing significant challenges. The decline of pollinators, driven by habitat loss, climate change, pesticide use, and other human activities, threatens the balance of many ecosystems. The discovery of these ancient pollinators serves as a reminder of the long and complex history of plant-insect interactions and the vital role they play in sustaining life on Earth.
Understanding the evolution of pollination from the Cretaceous period to the present day helps highlight the delicate balance between plants and their pollinators. As we continue to face environmental challenges, studying ancient ecosystems and the relationships that sustained them can provide valuable insights into how we can protect our planet’s biodiversity and ensure the survival of pollinators for future generations.
More information: “Long-Proboscid Flies as Pollinators of Cretaceous Gymnosperms.” DOI: dx.doi.org/10.1016/j.cub.2015.05.062