Fungalpedia – Note 2635, Muellerella
Muellerella Hepp ex Müll. Arg.
Citation when using this data: Meng QF et al. – Fungalpedia.
Index Fungorum, Faceoffungi, MycoBank, GenBank, Fig 1.
Classification: Chaetothyriales genera incertae sedis, Chaetothyriomycetidae, Eurotiomycetes, Pezizomycotina, Ascomycota, Fungi
Synonymy:
= Muellerellomyces Cif. & Tomas., Atti Ist. bot. Univ. Lab. crittog. Pavia, sér. 5 10(1) 33, 60 (1953)
= Pleothelis M. Choisy, Bull. mens. Soc. linn. Soc. Bot. Lyon 18: 140 (1949)
= Polycarpella Theiss. & Syd., Annls mycol. 16(1/2) 28 (1918)
= Spolverinia sect. Muellerella A. Massal., Flora, Regensburg 57: 351 (1874)
= Sychnogonia Körb., Syst. lich. germ. (Breslau) 332 (1855)
= Thelidiola C.W. Dodge, Nova Hedwigia 15: 299 (1968)
Muellerella was established by Müller (1862), and with M. polyspora as the type species. It is characterized by black apothecia, polysporous asci and brown spores (Müller 1862). Lumbsch (2007, 2010) and Wijayawardene et al. (2018) placed this genus within Verrucariaceae (Verrucariales). However, the phylogenetic analysis by Muggia et al. (2015b) showed that this genus forms a monophyletic lineage with Licheodiplis strains and sister to Epibryaceae within Chaetothyriales (Chaetothyriomycetidae). In addition, the co-occurrence of Lichenodiplis and Muellerella species on other hosts was confirmed based on an in-depth screening of herbarium collections by Muggia et al. (2015b). Diederich et al. (2018a) reclassified it within the Chaetothyriales genera incertae sedis, a viewpoint subsequently accepted by Wijavawardene (2020, 2022). This genus is characterized by the conspicuous black, sometimes slightly shiny, perithecioid, ostiolate ascomata, with multispore asci containing 1-septate, ellipsoid, brown ascospores.
Ciffrri et al. (1953) introduced Muellerellomyces with M. polysporae, which was later considered a synonymy with Muellerella polyspora (Ciffrri et al. 1953, Lamb 1963). Muellerella pygmaea was transferred from Microthelia pygmaea Körb. which had previously been transferred to Tichothecium pygmaeum (Körb.) Körb. However, Tichothecium pygmaeum was synonymized with Pleothelis myriocarpa Choisy, the type species of Pleothelis (Körber 1865a, Lamb 1963). Thus, Pleothelis was also synonymized with Muellerella.
Muellerella lichenicola was originally introduced by Sommerf (1826) and later synonymized with Polycarpella cookei (Linds.) Theiss. & Syd., the type species of Polycarpella by Theissen et al. (1918). Consequently, Polycarpella became a synonym of Muellerella. Another synonym, Sychnogonia, introduced by Körber (1855), was rejected in favor of Thelopsis Nyl. (1855). As a result, the species S. erratica and S. pygmaea were transferred to Muellerella as M. erratica and M. pygmaea, respectively, making Sychnogonia another synonymy of Muellerella (Körber 1865a).
Accroding to Index Fungorum (2025), there are 37 records in Muellerella. Eight species have been transferred to other genera, and eight are varieties which are not included in this list. Muellerella atricola has been combined with M. lichenicola, and both M. haplospora and M. opegraphicola have been combined with M. polyspora. To date, 19 species are recognized in this genus, and 16 of which are lichenicolous.
Type species: Muellerella polyspora Hepp ex Müll. Arg.
Other accepted species: Species Fungorum – search Muellerella.
Figure 1 – Muellerella polyspora redrawn from Müller (1862). a Section of ascomata. b Ascus. c Ascospores. Scale bars: a = 50 μm, b = 10 μm, c = 5 μm.
References
Ciffrri R, Tomaselli R. 1953 – Saggio di una sistematica micolichenologica. Atti del’Istituto Botanico e del Laboratorio Crittogamico dell’Università di Pavia 5 (10), 25–84.
Körber GW 1855 – Systema lichenum Germaniae. 1–458.
Lamb IM. 1963 – Index Nominum Lichenum Inter Annos 1932–1960. Divulgatorum, 1–810.
Lumbsch HT, Huhndorf SM. 2007 – Outline of Ascomycota—2007. Myconet 13, 1–58.
Nylander W. 1855 – Essai d’une nouvelle classification des lichens: Second mémoire. Mémoires de la Société Impériale des Sciences Naturelles de Cherbourg 3, 161–202.
Sommerfelt S 1826 – Supplementum florae lapponicae. 1–331.
Theissen Fv, Sydow H. 1918 – Vorentwürfe zu den Pseudosphaeriales. Annales Mycologici 16 (1–2), 1–34.
Entry by
Meng QF, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand and School of Public Health, Zunyi Medical University, Guizhou 563000, China.
Published online 23 June 2026