3.1 The members of the Kingdom
Approximately 98,000 fungal species have been described to date, the majority being members of the Ascomycota (about 64,000 known species) and the Basidiomycota (about 32,000 known species). These numbers will always be approximate because about 1,000 new species are described each year (an average of 1,229 species per year during 1980-89, 1,097 species per year in 1990-99, though only 850 species were described in 2007), and because not all ‘new’ descriptions are genuinely new; some have been described before under different names. In these cases the names are described as synonyms and one of them is chosen as the true name for the species (the earliest, most accurate description that follows the international rules of nomenclature) and the rest are reduced to synonymy, but they stay on the list and can never be used for any other species.
Because there are so many species of fungi for which no sexual stage is known, at least at the time when they are first described, a particular peculiarity of fungal taxonomy is the practice of assigning different generic and specific names to the asexual (called the anamorph) and sexual stages (called the teleomorph). When subsequent work establishes the connection between the two stages, two names will apply to the one organism and in this case the name that was defined first will take precedence. A particular example is that the well-known Aspergillus nidulans is an anamorph that has a teleomorph which was named Emericella. Strictly speaking, the generic name Emericella should take precedence, but it’s taken a long time for the geneticists and molecular biologists that have spent their lives working with Aspergillus nidulans to call their strains Emericella nidulans. This sort of thing can be a confusing complication to students of mycology, so you have to be aware of this peculiarity and take it in your stride because it is likely to happen more frequently as more molecular taxonomy is performed and reveals more synonyms. One thing this peculiarity of giving different names to sexual and asexual stages does do, of course, is increase the number of taxonomic names recorded for fungi.
In fact, around 300,000 species names exist, and this provides another opportunity for estimating how many real species we know about because major ‘monographs’ (the research studies in which taxonomists critically review all the species in a genus or family) suggest an average rate of synonymy of about 2.5 invalid names for each valid name. So if this ratio is applied to all 300,000 names we can estimate the upper limit of accepted known species to be about 120,000. This compares with an estimate of 1.5 million species currently present on Earth (Hawksworth, 2001).
The 21st Century Guidebook's Outline Classification of Fungi
We have an outline classification of Kingdom Fungi and related organisms in the form of a 23-page PDF file you can download and print.
Updated December 16, 2016