Why fungal names are changing?

Why fungal names are changing?

On page 91 of the printed Atlas of Clinical Fungi you will find a remarkable table: the names of the fungi in the 2nd edition (2000) compared with those in the new edition (2020). Two decades between both publications, and only about one-third of the species still has the same name. These perpetual name changes are one of the reasons that clinicians tend to get lost in the dark fungal forest. Why the names are changing, and could this not be prevented?

Taxonomists certainly do not do this just for fun. There are three main reasons for changes. (1) In our previous blog we explained that many changes are caused by methodical advance: today, we can simply recognize fungi with more precision than in the past, when we only had a microscope to our disposal. (2) Sequence data show that fungi with a similar appearance may be totally unrelated and thus cannot be maintained in the same genus. (3) The text below explains the role of reference material.

Carolus Linnaeus in 1753 invented a simple and consistent naming system for the living organisms. A cat (Felis catus) is easily recognized by later workers, but with many plants or insects you are less sure that you have the same species. Therefore reference materials were deposited in museums and herbaria. Such a deposited, publicly accessible specimen is called a type. A type is the nomenclatural gold standard: only the oldest name based on that material is valid; all later names for the same species are obsolete.

Typification of microorganisms was problematic, because of a dried 300-year-old fungus often not much more remains than some grains of sand. We had to wait until Louis Pasteur (1822-1895) introduced axenic culturing of microbes. The oldest fungal cultures that are still alive today date back from the late 19th century. However, the majority of common fungi were then already described. Thus, for many of the prevalent species, no reference point in a the form of a type is available. This led to numerous debates about species definitions (Hofstetter et al. 2019; Nenoff et al. 2018; Chowdhary et al. 2019).

What to do in such cases? There are two options. One is simply to say that without a type we don’t know what that species was, and discard the name as “doubtful”. At the end of the Atlas (page 1553) you will find a huge “Index of doubtful names …” with many abandoned names which in part still circulate in the medical literature. The species is then represented by the second oldest name for which a type is available. But it would not be a good idea to abandon widely used names such as Aspergillus fumigatus (1850) or Trichophyton tonsurans (1848) just because the type is unclear. An alternative solution is therefore to indicate another specimen, which matches with the original description, and deposit this as “neotype”. The neotype has then the same status as the original type: nomenclatural gold standard for the species. When the original type is still available but just consists of something unusable like some grains of sand, an “epitype” can be deposited (Ariyawansa et al. 2014; Crous et al. 2014). For epitypes, cultures are usually available, allowing modern research and diagnostics.

Taxonomic studies aim to stabilize nomenclature as much as possible by fixing the typification of species and thereby also of genera, families and orders (de Hoog et al. 2017; Quan et al. 2020). Stabilize may mean change. Summerbell et al. (2018) noted that the name Acremonium potronii, introduced by Vuillemin in 1910 (Atlas p. 568), has been used for different fungi in the literature, and that there is no type material to verify which interpretation was correct. Given the confusion in the literature, the authors decided to use the second oldest name with a type culture: Oospora egyptiacum (van Beyma 1933), which was sequenced and which is now known as Acremonium egyptiacum (Gams 1970). This name has now been adopted in the online version of the Atlas.


  • Ariyawansa H, Hawksworth DL, Hyde KD, et al. (2014) Epitypification and neotypification: guidelines with appropriate and inappropriate examples. Fung. Div. 69, doi:10.1007/s13225-014-0315-4.
  • Chowdhary A, Singh A, Singh PK, et al. (2018) Perspectives on misidentification of Trichophyton interdigitale / Trichophyton mentagrophytes using internal transcribed spacer region sequencing: Urgent need to update the sequence database. Mycoses 62: 11-15.
  • Crous PW, Giraldo A, Hawksworth DL, et al. (2014) The genera of fungi: fixing the application of type species of generic names. IMA Fungus 5: 141–160.
  • de Hoog GS, Dukik K, Monod M, et al. (2017). Towards a novel multilocus phylogenetic system for the dermatophytes. Mycopathologia 182: 5-31.
  • Gams W (1971) Cephalosporium-artige Schimmelpilze.
  • Hofstetter V, Buyck B, Eyssartier G, et al. (2019) The unbearable lightness of sequenced-based identification. Fung. Div. 96: 243–284.
  • Nenoff P, Verma SB, Urhrlass S, et al. (2018) A clarion call for preventing taxonomical errors of dermatophytes using the example of the novel Trichophyton mentagrophytes genotype VIII uniformly isolated in the Indian epidemic of superficial dermatophytosis. Mycoses 61, doi:10.1111/myc.12848.
  • Quan Y, Shi D, Ahmed SA, et al. (2020). Novel ancestral black yeast species in Chaetothyriales with ant-associated life style. Fung Biol. 125, Doi:10.1016/j.funbio.2020.11.006.
  • Summerbell RC, Gueidan C, Guarro J, et al. (2018) The protean Acremonium. A. sclerotigenum / egyptiacum: revision, food contaminant, and human disease. Microorganisms 6: 88, 10.3390/microorganisms6030088.
  • van Beyma FH (1933) Beschreibung einiger neuer Pilzarten aus dem Centraalbureau voor Schimmelcultures II – Baarn (Holland). Zentralbl. Bakt. ParasitKde, Abt 2, 89:236-243.