Fungi cannot enter the EDGE index because the data are not there

An indicator with no fungal list behind it

The EDGE Index — evolutionarily distinct and globally endangered — is one of the measures used to track progress under the Global Biodiversity Framework. It directs attention to species that sit alone on the tree of life and are also in trouble. There is no EDGE list for fungi. A paper that appeared online on 7 April 2026 in Conservation Letters sets out, with numbers, what limits any attempt to build one.

Susana P. Cunha, Susana C. Gonçalves, Steven P. Bachman, Eimear Nic Lughadha, James R. S. Westrip, Cátia Canteiro and Greg M. Mueller assessed the extinction risk of 94 fungal species using IUCN Red List Criteria. Fifty-six came back Data Deficient, 28 Least Concern, nine in threatened or near threatened categories, and one Not Evaluated — 94 in all. The article carries a March 2026 issue date (volume 19, issue 2, article e70041) but reached the web on 7 April, with the DOI registered the following day. The paper itself is open access under CC BY 4.0.

Why single-species genera

An EDGE score has two halves, and the evolutionary half is the awkward one for fungi. It is normally calculated from a phylogeny: how much of the tree of life would go with a species if it went. The published abstract records no such calculation. What it records is the sampling rule: the team drew its 94 species from monotypic genera — genera in which only one species is currently recognised — on the grounds, in the abstract's own careful phrasing, that such species are expected to have high evolutionary distinctiveness.

That is a proxy, and it is worth naming as one. A genus can hold a single species because the species really has no close relatives, or because nobody has yet described the ones it does have, or because a revision has not caught up with the sequencing. Reading this study as a list of the 94 most evolutionarily distinctive fungi would be reading something the authors did not write.

Data Deficient is a verdict on the evidence

Data Deficient is the category assessors reach for when the record is too thin to support any other. It is a statement about what is known, not about how the species is faring. A Data Deficient fungus may be common, or may be nearly gone; the point is that the evidence does not settle it. Here the category took 56 of the 94 assessments, close to three in five — that proportion is our arithmetic on the published counts, not a figure the paper states in that form.

The abstract attributes the pattern to severe knowledge gaps in fungal distribution, ecology and taxonomy, gaps that get in the way of evidence-based policy, and closes by arguing that basic mycological research is what would close them. The nine deserve care too: they were assigned to threatened or near threatened categories, and Near Threatened is not a threatened category under the IUCN system. The published counts give no breakdown of those nine, so none is offered here.

The readings this result will not support

The 94 are not the fungi on the Red List; they are the species this team assessed. The IUCN announcement of 27 March 2025 records that 482 newly assessed fungi brought the fungal total on the Red List to 1,300, of which at least 411 are at risk of extinction, against 169,420 species on the list as a whole. Fungi therefore account for well under one per cent of all assessments — again our own division, of two figures in that same release.

This is a journal paper, not an IUCN publication and not a Red List update. It does not create a fungal EDGE list, and it does not argue that the shortfall is caused by a lack of interest; it points at missing distribution, ecology and taxonomy, and at the research that would supply them. Those are different claims, and this paper can be cited only for the second.

One more thing is worth saying plainly. Every number above comes from the abstract as carried in the Crossref metadata record for the article. The full text could not be opened: the publisher's site refuses automated requests with an HTTP 403, and the only other location the open-access registries hold is a directory entry that points straight back at the same page. Open access does not here mean that a second copy exists to fetch. So no species list appears here, no figure from the study, and no account of why any individual assessment ended in Data Deficient.

What a reader can check

The scale of the gap is easiest to see in the chart at the top of this page. It comes from a different paper, one whose author list includes Susana P. Cunha and Susana C. Gonçalves, the first two authors of the study discussed here. Beside the bars for animals and plants, the fungal bar is a line lying on the axis. What cannot be checked is these particular 94 assessments: the list of them stayed in the full text we could not reach. Red List assessments are otherwise public documents — each species page states the criteria applied, the evidence they rest on and the date of the last review.

For anyone who keeps their own records, the practical lesson is unglamorous. What a Data Deficient assessment is missing is usually ordinary: a date, a precise location, the habitat and the substrate, whether the site produces again in later years, and a photograph good enough to identify something from. Records do not change categories by themselves — a category changes only through a formal reassessment, made by designated assessors against the same criteria. But they are the material without which that reassessment has nothing to stand on, and they are the one part of this that an ordinary observer supplies.