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In the latest issue of IMA fungus, Vol.9. no1, the hottest discussion revolves around the following aspect: do we accept a sequence-based species description of fungi or don’t we?
‘In modern ecology, when you have a substrate in your hand that contains DNA sequences of a thousand species, half of them unknown, have you discovered 500 new species or have you picked up a handful of dirt?’ is one of the questions raised in an editorial in IMA Fungus (Seifert 2017).
Well, what do you have?
A lot of mycologists are involved in the discussion. The idea was to debate this on the next IBC (International Botanical Conference) conference in 2023 in Rio de Janeiro.
However, it seems that some mycologists perceive an urgency in discussing it at the 11th International Mycological Congress (IMC11) now taking place in Puerto Rico. Two proposals have been submitted to vote on this week, aiming at allowing formal naming of fungal taxa only known from their DNA sequences: the so-called: ‘Dark matter fungi’. The DNA sequence itself would be the type of a taxon name in the absence of a specimen.
In favour of this idea are David Hawksworth and Robert Lücking, arguing that there is an urgent need for a formal nomenclature of sequence-based, voucherless Fungi, ‘given that environmental sequencing has accumulated more than one billion fungal ITS reads [..]. These unnamed Fungi could help to bridge the gap between the 115.000 to 140.000 currently accepted and 2.2 to 3.8 million predicted species, a gap that cannot realistically be filled using specimen or culture-based inventories’.
A counterproposal of other mycologists is to allow ‘candidate’ names like bacteriologists already use and several mycologists proposed in publications as: ‘virtual taxa’, ‘species hypothesis’ or ‘candidate species’.

Pedro Crous, director of Westerdijk Fungal Biodiversity Institute recognizes the problem of the unknown fungi. ‘The world will be gone and we will still be trying to put names on all fungi.’ Yet: ‘The question is: do you put names on something that you cannot see. Until proven otherwise you are giving a name to a hypothesis. You only have the names, the question is: is this the road to nowhere or is this time travel?’ Added to that, he is wondering whether this could be the end of science as we know it, since the possibility exists that in the future fungi are not described as we did previously, and not preserved in collections, and that in the end no one knows what those new fungi do. ‘What do they break down, what do they produce, what do they kill, we won’t know.’ Yet some of the new species could be the producers of promising new anti-biotics or the next important anti-cancer treatment.
In a short article by no less than 420 authors and co-authors under whom Pedro Crous, the counterproposal is published. The authors consider the propositions of Hawksworth and Lücking highly problematic and probably premature. There is always a possibility of giving two different taxa the same name, because they share identical DNA sequences at a specific locus (e.g. ITS). Or the other way around: not all members of a species can be assumed to share the same DNA sequence at a specific locus. Different sequencing techniques can result in artifacts, there are no minimum requirements mentioned, probably resulting in future mycologists having to gather additional information. All in all, the 420 authors speak about ‘creating confusion and substantial extra work for contemporary and future mycologists’ instead of solving problems.
The solution according to them: a functional system for environmental sequences under the Candidatus or species hypotheses approach, resulting from a carefully selected set of requirements to ensure high-quality data and reproducibility: that could lead to well-considered rules for coming generations: ‘so they can improve on our work and take appropriate, well informed taxonomic decisions using all available information.’

This week in Puerto Rico the game is on!