# Ostropomycetidae

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Subclass of fungi

Ostropomycetidae The script lichen species Graphis scripta Scientific classification Kingdom: Fungi Division: Ascomycota Class: Lecanoromycetes Subclass: Ostropomycetidae Reeb, Lutzoni, & Cl.Roux (2004) Orders Baeomycetales Graphidales Gyalectales Odontotrematales Ostropales Pertusariales Sarrameanales Schaereriales Thelenellales

The **Ostropomycetidae** are a [subclass](/source/Subclass_(biology)) of mostly [lichen](/source/Lichen)-forming fungi in the class [Lecanoromycetes](/source/Lecanoromycetes). It contains nine [orders](/source/Order_(biology)) and 37 [families](/source/Family_(taxonomy)).[1]

[Arctomiaceae](/source/Arctomiaceae) is the only family in the Ostropomycetidae that associates with [cyanobacteria](/source/Cyanobacteria) of the order [Nostocales](/source/Nostocales) as its main [photobiont](/source/Photobiont) partner.[2]

## Taxonomy

The subclass was [circumscribed](/source/Circumscription_(taxonomy)) in 2004 by Catherine Reeb, François M. Lutzoni, and [Claude Roux](/source/Claude_Roux). This classification was based on [molecular phylogenetics](/source/Molecular_phylogenetics) studies combining nuclear [ribosomal RNA](/source/Ribosomal_RNA) genes (SSU and LSU) with the protein-coding gene *[RPB2](/source/RPB2)*. In their study, adding *RPB2* to the ribosomal markers was intended to improve resolution and support for deeper relationships among major ascomycete [lineages](/source/Lineage_(evolution)), including lichen-forming groups, and it was in this context that Ostropomycetidae was introduced as a new subclass.[3]

The taxonomic framework is anchored by the type order [Ostropales](/source/Ostropales), which includes the type family [Stictidaceae](/source/Stictidaceae) (synonymous with Ostropaceae) and its type genus *[Stictis](/source/Stictis)*. In the protologue, Ostropomycetidae was characterised broadly enough to include both lichen-forming and non-lichen-forming fungi; when lichenised, members typically have crustose, squamulose, or filamentous thalli, with a green-algal photobiont (either [chlorococcoid](/source/Glossary_of_lichen_terms#chlorococcoid) or *[Trentepohlia](/source/Trentepohlia_(alga))*). The fruiting bodies are described as apothecia or, in some lineages, perithecia, and the [asci](/source/Ascus) bear eight or fewer colourless spores that may be simple, transversely septate, or [muriform](/source/Glossary_of_lichen_terms#muriform) (divided into many small compartments). [Phylogenetic](/source/Phylogenetic) analyses in the same study resolved two major evolutionary lineages within the subclass: the [Pertusariales](/source/Pertusariales)-[Icmadophilaceae](/source/Icmadophilaceae) clade and a group consisting of the Ostropales, [Baeomycetales](/source/Baeomycetales), and [Hymeneliaceae](/source/Hymeneliaceae).[3]

## Description

The Ostropomycetidae are a subclass of fungi that can exist either as non-lichenised forms or as lichens with a variety of body types, including [crust-like](/source/Crustose_lichen), scaly ([squamulose](/source/Squamulose_lichen)), or filamentous [thalli](/source/Thallus). When lichens are present, their [photosynthetic](/source/Photosynthetic) partners ([photobionts](/source/Glossary_of_lichen_terms#photobionts)) are usually [green algae](/source/Green_algae) of a simple, rounded shape ([chlorococcoid](/source/Glossary_of_lichen_terms#chlorococcoid)) or algae of the genus *[Trentepohlia](/source/Trentepohlia_(alga))*, known for their orangeish hue.[3]

The reproductive structures ([ascomata](/source/Ascomata)) of these fungi can be found embedded in the lichen's surface ([immersed](/source/Glossary_of_lichen_terms#immersed)), sitting on top of it ([sessile](/source/Glossary_of_lichen_terms#sessile)), or raised on a stalk ([pedunculate](/source/Glossary_of_lichen_terms#pedunculate)). They take the form of open, disc-like [fruiting bodies](/source/Fruiting_bodies) called [apothecia](/source/Apothecia)—these can present in different styles, such as cryptolecanorine and [lecanorine](/source/Glossary_of_lichen_terms#lecanorine) forms, and sometimes appear as [lecideine](/source/Glossary_of_lichen_terms#lecideine) when partially immersed. In some members, the reproductive structures may instead resemble flask-shaped [perithecia](/source/Perithecia).[3]

Inside the ascomata are special sac-like cells ([asci](/source/Ascus)), each typically holding eight or fewer spores ([ascospores](/source/Ascospore)). These spores are colourless and can be [simple](/source/Glossary_of_lichen_terms#simple) (without internal divisions), divided by transverse walls, or arranged into more complex, brick-like partitions ([muriform](/source/Glossary_of_lichen_terms#muriform)). Thin, thread-like supporting filaments called [paraphyses](/source/Paraphyses) may be simple or may branch and reconnect ([anastomose](/source/Glossary_of_lichen_terms#anastomose)), providing structural support.[3]

The asci can have one or two layers ([unitunicate](/source/Glossary_of_lichen_terms#unitunicate) or [bitunicate](/source/Glossary_of_lichen_terms#bitunicate)) but function as if they have a single layer. They may or may not contain a [tholus](/source/Glossary_of_lichen_terms#tholus) (a structure in the ascus tip), and this tholus can sometimes react with [iodine](/source/Iodine), making it appear bluish ([amyloid](/source/Amyloid_(mycology))). Additionally, some asci have an "ocular chamber"—a distinct region at the tip that helps release spores—while others do not.[3]

## Chemistry

As with many lichen-forming fungi, members of Ostropomycetidae produce a wide range of [secondary metabolites](/source/Secondary_metabolite): small [organic compounds](/source/Organic_compound) that are not required for basic growth, but can help lichens cope with stresses and mediate interactions with other organisms. In lichenology these substances matter because their presence and distribution often track particular lineages, so chemical [characters](/source/Glossary_of_lichen_terms#characters) have long been used alongside [morphology](/source/Morphology_(biology)) and DNA evidence in [taxonomy](/source/Taxonomy_(biology)) and [systematics](/source/Systematics). The lichen partnership also brings additional biosynthetic capacity: the photobiont (green alga or [cyanobacterium](/source/Cyanobacterium)) and associated microbes can contribute to, or influence, the overall chemical profile found in the thallus.[4]

Across the subclass, reported metabolites span several familiar lichen-chemical families. A recent synthesis of the literature summarised 202 structurally characterised compounds from Ostropomycetidae lichens (drawn from 14 studied families), with roughly half belonging to phenolic [derivatives](/source/Derivative_(chemistry)) such as simple [phenols](/source/Phenol), [depsides](/source/Depside), [tridepsides](/source/Tridepside), and [depsidones](/source/Depsidone). Much of the remaining diversity falls under [polyketide](/source/Polyketide)-derived groups (including [lactones](/source/Lactone), [phthalides](/source/Phthalide), [dibenzofurans](/source/Dibenzofuran), [chromones](/source/Chromone), and [xanthones](/source/Xanthone)), with additional records of [fatty acids](/source/Fatty_acid), [terpenoids](/source/Terpenoid) (including sesquiterpenes), [sterols](/source/Sterol), and a small number of non-ribosomal [peptides](/source/Peptide). Many of these compounds have been screened in laboratory assays for activities such as [antibacterial](/source/Antibacterial), [antifungal](/source/Antifungal), [antiviral](/source/Antiviral), [antioxidant](/source/Antioxidant), and [anti-inflammatory](/source/Anti-inflammatory) effects. Because many lichens grow slowly, researchers often rely on cultured fungal partners (mycobionts) as an alternative way to obtain enough material for chemical study.[4]

## Taxa of uncertain classification

The following taxa are of uncertain classification ([incertae sedis](/source/Incertae_sedis)) in the Ostropomycetidae:[1]

Family incertae sedis:

- [Epigloeaceae](/source/Epigloeaceae) Zahlbr. (1903)

Genera incertae sedis:

- *[Amphorothecium](/source/Amphorothecium)* P.M.McCarthy, Kantvilas & Elix (2001)[5] – 1 sp.

- *[Anzina](/source/Anzina)* Scheid. (1982)[6] – 1 sp.

- *[Aspilidea](/source/Aspilidea)* Hafellner (2001)[7] – 1 sp.

- *[Bachmanniomyces](/source/Bachmanniomyces)* D.Hawksw. (1981)[8] – 8 spp.

- *[Dictyocatenulata](/source/Dictyocatenulata)* Finley & E.F.Morris (1967)[9] – 1 sp.

- *[Malvinia](/source/Malvinia)* Döbbeler (2003)[10] – 1 sp.

- *[Pleiopatella](/source/Pleiopatella)* Rehm (1908)[11] – 1 sp.

## References

1. ^ [***a***](#cite_ref-2024_Outline_1-0) [***b***](#cite_ref-2024_Outline_1-1) Hyde, K.D.; Noorabadi, M.T.; Thiyagaraja, V.; He, M.Q.; Johnston, P.R.; Wijesinghe, S.N.; et al. (2024). ["The 2024 Outline of Fungi and fungus-like taxa"](https://www.researchgate.net/publication/385939154). *Mycosphere*. **15** (1): 5260–5267. [doi](/source/Doi_(identifier)):[10.5943/mycosphere/15/1/25](https://doi.org/10.5943%2Fmycosphere%2F15%2F1%2F25). [hdl](/source/Hdl_(identifier)):[1854/LU-8660838](https://hdl.handle.net/1854%2FLU-8660838).

1. **[^](#cite_ref-Miadlikowska_et_al._2014_2-0)** Miadlikowska, Jolanta; Kauff, Frank; Högnabba, Filip; Oliver, Jeffrey C.; Molnár, Katalin; Fraker, Emily; et al. (2014). ["A multigene phylogenetic synthesis for the class Lecanoromycetes (Ascomycota): 1307 fungi representing 1139 infrageneric taxa, 317 genera and 66 families"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4185256). *Molecular Phylogenetics and Evolution*. **79**: 132–168. [doi](/source/Doi_(identifier)):[10.1016/j.ympev.2014.04.003](https://doi.org/10.1016%2Fj.ympev.2014.04.003). [PMC](/source/PMC_(identifier)) [4185256](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4185256). [PMID](/source/PMID_(identifier)) [24747130](https://pubmed.ncbi.nlm.nih.gov/24747130).

1. ^ [***a***](#cite_ref-Reeb_et_al._2004_3-0) [***b***](#cite_ref-Reeb_et_al._2004_3-1) [***c***](#cite_ref-Reeb_et_al._2004_3-2) [***d***](#cite_ref-Reeb_et_al._2004_3-3) [***e***](#cite_ref-Reeb_et_al._2004_3-4) [***f***](#cite_ref-Reeb_et_al._2004_3-5) Reeb, V.; Lutzoni, F.; Roux, C. (2004). "Multilocus phylogenetic circumscription of the lichen-forming fungi family Acarosporaceae and its position within the Ascomycota". *Molecular Phylogenetics and Evolution*. **32** (3): 1036–1060. [doi](/source/Doi_(identifier)):[10.1016/j.ympev.2004.04.012](https://doi.org/10.1016%2Fj.ympev.2004.04.012). [PMID](/source/PMID_(identifier)) [15288074](https://pubmed.ncbi.nlm.nih.gov/15288074).

1. ^ [***a***](#cite_ref-Wang_et_al._2025_4-0) [***b***](#cite_ref-Wang_et_al._2025_4-1) Wang, Yunhui; Hao, Chengyue; Jiang, Shuhao; Ju, Yanhu; Li, Wei; Jia, Zefeng (2025). ["A comprehensive review on chemical structures and bioactivities of Ostropomycetidae lichens"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12113121). *Journal of Fungi*. **11** (5) 369. [doi](/source/Doi_(identifier)):[10.3390/jof11050369](https://doi.org/10.3390%2Fjof11050369). [PMC](/source/PMC_(identifier)) [12113121](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12113121). [PMID](/source/PMID_(identifier)) [40422703](https://pubmed.ncbi.nlm.nih.gov/40422703).

1. **[^](#cite_ref-McCarthy_et_al._2001_5-0)** McCarthy, P.M.; Kantvilas, G.; Elix, J. A. (2001). "*Amphorothecium*, a new pyrenocarpous lichen genus from New South Wales, Australia". *The Lichenologist*. **33** (4): 291–296. [doi](/source/Doi_(identifier)):[10.1006/lich.2001.0330](https://doi.org/10.1006%2Flich.2001.0330).

1. **[^](#cite_ref-Scheidegger_1985_6-0)** Scheidegger, C. (1985). "Systematische Studien zur Krustenflechte *Anzina carneonivea* (Trapeliaceae, Lecanorales)" [Systematic studies on the crustose lichen *Anzina carneonivea* (Trapeliaceae, Lecanorales)]. *Nova Hedwigia* (in German). **41** (1–4): 191–218.

1. **[^](#cite_ref-Hafellner_&_Türk_2001_7-0)** Hafellner, J.; Türk, R. (2001). ["Die liechenisierten Pilze Österreichs – eine Checkliste der bisher nachgewiesenen Arten mit Verbreitungsangaben"](https://www.researchgate.net/publication/309282880). *Stapfia* (in German). **76**: 3–167 [149].

1. **[^](#cite_ref-Hawksworth_1981_8-0)** Hawksworth, D.L. (1981). "The lichenicolous Coelomycetes". *Bulletin of the British Museum for Natural History*. **9** (1): 1–98 [10].

1. **[^](#cite_ref-Morris_&_Finley_1967_9-0)** Morris, Everett F.; Finley, David E. (1967). "Two new genera of stilbellaceous Fungi". *American Midland Naturalist*. **77** (1): 200–204. [doi](/source/Doi_(identifier)):[10.2307/2423439](https://doi.org/10.2307%2F2423439). [JSTOR](/source/JSTOR_(identifier)) [2423439](https://www.jstor.org/stable/2423439).

1. **[^](#cite_ref-Döbbeler_2003_10-0)** Döbbeler, P. (2003). ["Ascomycetes on *Dendroligotrichum* (Musci)"](http://ascofrance.com/uploads/forum_file/Nova-Hedwigia-2003-v76-p1-0001.pdf) (PDF). *Nova Hedwigia*. **76**: 1–44.

1. **[^](#cite_ref-Rehm_1908_11-0)** Rehm, H. (1908). "Ascomycetes novi". *Annales Mycologici* (in German). **6** (4): 313–325 [314].

Taxon identifiers Ostropomycetidae Wikidata: Q2035955 Wikispecies: Ostropomycetidae AusFungi: 60013148 AusLichen: 30016222 EPPO: 1OSTRL IndexFungorum: 501505 ITIS: 936330 MycoBank: 501505 NBN: NHMSYS0020535786 NCBI: 388283 NZOR: befa0407-fcb0-4118-9921-242aaaa71444 Open Tree of Life: 877964 SpeciesFungorum: 501505 Tropicos: 100450498 WoRMS: 437335

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Adapted from the Wikipedia article [Ostropomycetidae](https://en.wikipedia.org/wiki/Ostropomycetidae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ostropomycetidae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.