This enormous forest of clones is a single living being, perhaps the largest and oldest on the planet

In the mountains of the state of Utah, United States, there is a special aspen forest that extends up to 45 hectares. If you walk through it, you would have to cross a set of 47,000 trees. This site hides a genetic secret: each trunk in the place is actually the stem of an original seedling of Populus tremuloides that one day it arrived there and spread.

That forest is called Pando, although it is also nicknamed “the trembling giant” due to the species of tree it contains (aspen). It belongs to the class of giant living beings that on the surface look like clusters of individual elements, but which, underground, are united by roots. Pando is a clonal colony. Each tree is genetically the same as the rest. They were all born and raised in an interconnected root. The cycle will continue as long as nothing harms the ‘shaking giant’.

There is a forest of clones and science wants to know how long. Biologists know that clonal plants must live much longer than any other living thing. There are several estimates of Pando’s true age, but scientific opinions are divided. The first dating mentioned that it must have been 80,000 years old. Some more adventurous ones (now discarded) estimated a million years. The University of Chicago in Illinois has a new DNA-based estimate that they hope to end the decades-long debate.

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What genetic variations say

The researchers sequenced more than 500 samples of the tree to verify its age and obtain clues about how it has adapted throughout its life. According to their study, Pando must be between 16,000 and 80,000 years old. With this information, it is possible to consider this Utah aspen forest as one of the oldest currently living organisms in the world. The University of Chicago work has yet to be reviewed by the scientific community, but can be consulted on the prepublications server bioRxiv.

The age shown by the phylogenetic models can also be verified with the presence of pollen from Populus tremuloides in the lake sediments (the material that accumulates at the bottom of rivers) of Lake Fish, near Pando. It also coincides with some of the previous studies that calculated age based on their growth rate and even taking into account prehistoric climate change events.

The researchers also found up to 4,000 genetic variations in the collected samples. This finding confirms that, although the Pando clones are genetically the same, genetic mutations accumulate in each stem. The oldest ones have some and the most recent ones others. “This work improves the understanding of the accumulation and dispersion of mutations within and between ramets of long-lived organisms that reproduce clonally,” says the scientific article.

The ‘trembling giant’ is not the only living being of enormous proportions. In Oregon, United States, there is a honey mushroom that is also a 9.6 square kilometer clonal colony. The study of long-lived plant organisms will help understand how they protect their genome despite reproducing asexually.