Old clones
A group of international researchers discovered that an eelgrass colony is about 1400 years old. They managed this feat due to the developing an new age determination method for clones that they published in Nature and Ecology & Evolution.
For organisms that multiply by cloning themselves it is difficult to determine their age. For example, when they last germinated from seeds. In order to change that the researchers turned to somatic genetic variation. This is the variation that a genome accumulates in their stem cells due to for example UV-radiation. So not the mistakes that slip in due to copying the DNA when the cell divides.
Researchers already are using somatic genetic variation to determine how long ago a common ancestor of two species lived. But in order to also use it to determine the age of clones a few adjustments were needed. The researchers found these through modelling. In this way they also discovered that the accuracy of the calculations is influenced by the number of stem cells an organism has.
The researchers calculated the age of clones using the speed with which somatic genetic variations accumulate
After adjusting the calculation, it was time to find out if the method works. For the calibration of the method the researchers used two eelgrass colonies with known age, 4 and 17 years. First the researchers determined which tissue best to collect for sampling. For this the researchers studied the growth centres, there where the stem cells are located. They observed that most of the cells for the leaves originated from the stem cells in the growth centre.
Through sampling leaves of individual clones in both colonies the researchers could find out how much variation there was between the clones and colonies. From this they could calculate the speed with which somatic genetic variations accumulate. With this speed the researchers calibrated the formula.
Subsequently the researchers sampled worldwide 15 eelgrass colonies. Although the majority of the colonies turned to be less than 40 years old. There were also 4 exceptions that were older than 270 years, with one being even older that 1400 years. The researchers hope that this method can contribute to research about how robust clonal colonies are.
Literature
Yu, L., Renton, J., Burian, A. et al. A somatic genetic clock for clonal species. Nat Ecol Evol (2024). https://doi.org/10.1038/s41559-024-02439-z
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