For centuries, scientists have debated the early stages of plant colonization on land, and now a landmark discovery suggests a surprising partner was essential: lichens. New research confirms that a mysterious fossil, Spongiophyton, represents an ancient lichen that thrived around 410 million years ago, likely preparing the ground for vascular plants—the ancestors of modern trees and flowers—to flourish. This overturns previous assumptions that lichens evolved after land plants had already established themselves.
The Long-Standing Mystery of Spongiophyton
Before forests and prairies, early land was dominated by microbial mats. Vascular plants, the first complex land plants, were just emerging. Spongiophyton fossils, found worldwide, have puzzled paleontologists for over a century. Was it an early type of algae, or something else entirely? The answer remained elusive because lichens, being soft-bodied organisms, rarely leave clear fossil traces.
Chemical Evidence Reveals the Truth
The breakthrough came through analyzing the chemical composition of organic material within the fossils. Lichens are a symbiotic partnership between fungi and algae or cyanobacteria. Unlike algae, which have cell walls, lichens contain chitin—a material also found in insect exoskeletons—and this chitin is rich in nitrogen. The research team at Harvard University found a consistent nitrogen signal in Spongiophyton fossils, proving their fungal nature. Further analysis revealed branching patterns characteristic of growing fungal cells (hyphae), solidifying the lichen identification.
Why This Matters: The Role of Lichens in Early Ecosystems
This discovery isn’t just about identifying an old fossil; it rewrites our understanding of early land ecosystems. Lichens are nature’s original soil builders, breaking down rocks and sediments into nutrient-rich substrates. Vascular plants rely on these nutrients to grow, funneling them from the ground up through their tissues. By existing before and alongside early plants, lichens likely weathered rocks, stabilized sediments, and created the first protosoils, essentially preparing the landscape for plant life to expand.
“It’s a major shift in how we view the complexity of life’s first steps onto land,” says study lead author Bruno Becker-Kerber.
A More Complete Story of Life on Land
The timeline now suggests lichens evolved shortly after the initial spread of vascular plants (around 420 million years ago) and just before the emergence of the earliest forests (around 390 million years ago). This means the story of life moving onto land isn’t just a “plant story”; it’s a fungal-plant story, with lichens playing a crucial, previously underestimated role. The discovery emphasizes that the transition to terrestrial life was a complex interplay between multiple organisms, not just plants alone.
