Hundreds of thousands of fungi are denied scientific names

Drying soil samples immediately upon collection under field conditions in Norway.
Photo Credit: Sten Anslan

Fungi that do not form fruiting bodies and that we can’t cultivate in the laboratory cannot be given scientific names. This has left them essentially ignored by science. In a study coordinated from the university of Gothenburg, researchers analyzed a large dataset of fungal DNA sequences from global soil samples and found that these intangible fungi seem to dominate the fungal kingdom.

The concept of dark biodiversity denotes species that are recovered through DNA sequencing of substrates such as soil and water – but where no individuals of those species have ever been observed.

It has been known for more than a decade that the fungal kingdom is home to dark biodiversity, but the magnitude of this dark fungal diversity has been the subject of much speculation. A new study from the University of Gothenburg, published in the journal MycoKeys, addresses the question based on 8 million fungal DNA sequences from global soil sampling. The study turns our understanding of the fungi on its head by showing that the fungal kingdom may be almost exclusively dark.

DNA extraction from soil samples in the laboratory.
Photo Credit: Sten Anslan

300,000 unknown fungi

The study revealed nearly half a million fungal species, of which close to 300,000 represented dark fungal diversity – species that do not have scientific names and cannot get such names at present.

“It’s problematical that the rules that govern the naming of fungi require that they either form tangible physical structures such as fruiting bodies or that we can cultivate them in the laboratory. This seems to hold true for only a tiny proportion of all fungi. Attempts to modify these rules to better reflect the full fungal kingdom have been rejected, largely because DNA sequences are perceived as a threat to the traditional way of describing and naming fungi,” says biologist Henrik Nilsson at the University of Gothenburg. 

The authors of the study hope for change in the wake of their results. If not, the study argues, knowledge building of our living world will be severely stymied. This will, in turn, have ramifications for other sciences, such as geology and climatology.

“For instance, how do the dark fungi obtain their energy and nutrients? What ecological processes and associations do they partake in? Right now, these are not factored into our geo-ecological models for flow of mass and energy in ecosystems, that’s for sure. As long as the dark fungi are swept under the carpet, we cannot hope to do a good job with any of our models,” says Henrik Nilsson.

Studies of the evolution and phylogeny of fungi will similarly be crippled if the dark fungi are excluded.

Sparse royal tree

“Ignoring the dark fungi in such efforts is like trying to estimate the lineage of the Swedish royal house after first having dismissed more than half of all persons who should have been considered for inclusion. The result would be a very inaccurate and misleading royal tree, that much is certain,” says Henrik Nilsson.

The study proposes a set of criteria to ensure that the naming of dark fungi meets the same degree of scientific reproducibility and robustness that characterizes naming in the less troublesome parts of the fungal kingdom. The criteria proposed would only govern the naming of dark fungi, leaving mycological naming convention in the lighter parts of the fungal tree of line untouched.

“I’m guessing that our observations won’t be the last word on the matter, but we certainly hope that they give rise to a much-needed in-depth debate," says Henrik Nilsson. It is high time for fungal researchers to start taking dark fungal diversity seriously. Specifically, we hope that the international mycological congress of 2024 will vote to allow naming also of these fungi. Our knowledge of the enigmatic fungal kingdom would be able to take giant strides forward after a positive resolution of this question.”

Published in journal: MycoKeys

Source/Credit: University of Gothenburg

Reference Number: mcb041423_01

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