The number of described fungal species

"Over 150,000" indicates an order of magnitude of names regarded as described species, not a fixed counter of nature. The data comes from nomenclatural registers such as Index Fungorum and Species Fungorum. Every year new descriptions, combinations and corrections are added, and specialists tidy up synonyms. For that reason the value is given as a safe lower bound and carries a verification date.

A name does not always correspond to one biological species in a simple way. The same organism may historically have been given several names, particularly where the sexual and asexual stages were described separately. Conversely, DNA analysis may divide a broadly understood species into several lineages. A nomenclatural database records naming acts, while a taxonomic catalogue interprets which of them are currently accepted. The figure therefore depends on the definition adopted and on how far the work has progressed.

The pool includes more than cap fungi. It contains yeasts, moulds, pathogens of plants and animals, lichen-forming fungi and numerous microscopic groups. The value should not be compared one to one with the number of entries in a field atlas, which deliberately selects organisms relevant to a particular area and user.

The most important comparison concerns the scale of what we do not know. Against a global estimate of 2.2–3.8 million, the described set amounts to roughly four to seven per cent of the predicted total. Even that proportion is an approximation of two variable figures. It does not mean that the remaining species are waiting in equal portions in every forest. It shows that taxonomy is still documenting basic diversity, and that stable registers, collections and publications are the infrastructure needed to measure it.

A name, a species and a record are different units

The 155,000 value is a dated Kew benchmark, not a live readout from one database. Nomenclatural registers also hold synonyms, name combinations and historical entries, so a count of “names” cannot automatically be treated as a count of accepted species. Conversely, lineages known only from sequence data may not yet possess a formal name.

Against the 2.5-million best estimate, the described share is about 6.2%. This expresses the scale of the taxonomic task but cannot predict when the catalogue will be “complete”: the rate of description, standards of evidence and the expected total diversity all change over time.