3.1 The members of the Kingdom
Approximately 120,000 fungal species have been described to date, the majority being members of the Ascomycota (over 64,000 known species) and the Basidiomycota (over 32,000 known species). These numbers will always be approximate because about 1,000 new species are described each year (and have been for several decades), 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 (the earliest, first validly published name that follows the international rules of nomenclature) is chosen as the true name for the species 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. An 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 have taken precedence, but the geneticists and molecular biologists that had spent their lives working with Aspergillus nidulans were unwilling to call their strains Emericella nidulans. This sort of thing can be a confusing complication to students of mycology, so you must be aware of this historical peculiarity and take it in your stride. One thing this peculiarity of giving different names to sexual and asexual stages did, of course, is increase the number of taxonomic names recorded for fungi. Fortunately, this practice ended in 2011; so, Aspergillus is the right name for A. nidulans and not Emericella.
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. 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 up to 3.8 million species currently present on Earth (Hawksworth & Lücking, 2017; see Section 1.7 above), which leaves up to 3.6 million species of fungi still to be found and described.
We have an Outline Classification of Fungi (and related organisms), prepared in 2018, which appears as Appendix 1 of the printed version of this text; you can download a PDF of this from the hyperlink in the next Resources Box. In the rest of this chapter we will concentrate on the biology of the organisms classified as fungi.
Resources Box The 21st Century Guidebook's Outline Classification of Fungi 2018 We have an outline classification of Kingdom Fungi and related organisms in the form of a 18-page PDF file (with live hyperlinks to references) you can download from the hyperlink below: |
Updated January, 2020
