Scientists have confirmed that one of Earth's most remarkable living beings—a massive forest of quaking aspen trees in Utah known as Pando—is between 16,000 and 80,000 years old, solidifying its place among the planet's most ancient organisms.
The forest, whose Latin name means "I spread," is actually a single living thing: one tree that has cloned itself tens of thousands of times. Spanning 42.6 hectares of Utah's Fishlake National Forest, Pando consists of approximately 47,000 individual stems all connected by a single, vast root system.
"If you were to visit Pando, it would just look like a normal forest," William Ratcliff, an evolutionary biologist at the Georgia Institute of Technology in Atlanta and co-author of the study, told Newsweek. "But while the trees last only about 200 years, they continually regenerate new trees from the root system, which kind of lives forever."
What makes Pando particularly unique is its genetic makeup. The tree is triploid, meaning its cells contain three copies of each chromosome instead of the usual two.
This unusual characteristic prevents Pando from reproducing sexually with other trees, leading it to create perfect copies of itself instead.
However, these clones aren't entirely identical. As cells divide, they can accumulate genetic mutations, creating slight variations that provide scientists with valuable information about the tree's evolutionary history.
By analyzing DNA samples in a painstaking yearslong research mission, the team collected from roots, bark, leaves, and branches throughout the forest, identifying nearly 4,000 genetic variants that had emerged over millennia of cloning.
The findings, posted on the bioRxiv preprint server, revealed surprising patterns in how these mutations spread throughout the forest.
While researchers expected nearby trees to share more genetic similarities, the relationship between physical proximity and genetic similarity was weaker than anticipated across the forest as a whole.
"You would expect that the trees that are spatially close are also closer genetically," Rozenn Pineau, a plant evolutionary geneticist at the University of Chicago and co-author of the new study, told Nature. "But this is not exactly what we find."
Ratcliff added, "This result was so surprising. At a large scale, Pando is very well mixed."
The findings show that if you pick two trees far apart in the forest, they're as likely to be genetically similar as two close together—a pattern that holds until you look at scales under 15 meters or so.
The study also provides insights into Pando's remarkable longevity. The researchers suggest that its triploidy might contribute to "bigger cells, bigger organisms, better fitness," according to Pineau.
The findings hint at the existence of protective mechanisms that help plants and trees prevent the accumulation of harmful genetic mutations.
To put Pando's age in perspective, Ratcliff said, "It makes the Roman Empire seem like a recent phenomenon (...) it was a blip." The forest's extensive lifespan and unique characteristics continue to intrigue scientists, with many calling for further research into this extraordinary organism.
The research, which has not yet been peer-reviewed, represents a significant step forward in understanding one of nature's "wonders of the world," as Ratcliff put it.
"This organism has persisted for tens of thousands of years. It's seen ice ages come and go, mass extinction events, and it's still here. It highlights a kind of resilience that is rare in nature," he said.
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Reference
Pineau, R. M., Mock, K. E., Morris, J., Kraklow, V., Brunelle, A., Pageot, A., Ratcliff, W. C., & Gompert, Z. (2024). Mosaic of Somatic Mutations in Earth's Oldest Living Organism, Pando (p. 2024.10.19.619233). bioRxiv. https://doi.org/10.1101/2024.10.19.619233
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