Chroodiscus

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Genus of lichens

title: "Chroodiscus" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["graphidaceae", "taxa-described-in-1883", "graphidales-genera", "taxa-named-by-johannes-müller-argoviensis", "lichen-genera"] description: "Genus of lichens" topic_path: "general/graphidaceae" source: "https://en.wikipedia.org/wiki/Chroodiscus" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Genus of lichens ::

| image = | image_caption = | taxon = Chroodiscus | authority = (Müll.Arg.) Müll.Arg. (1890) | type_species = Chroodiscus coccineus | type_species_authority = (Leight.) Müll.Arg. (1890) | synonyms_ref = | synonyms = *Ocellularia sect. Chroodiscus

  • Phyllobrassia

Chroodiscus is a genus of leaf-dwelling lichens in the family Graphidaceae. These lichens form thin, smooth crusts directly on living leaves and are characterized by distinctive star-shaped fruiting bodies that split into triangular segments, with centres ranging from grey to bright scarlet-red depending on their chemical composition. The genus is found throughout tropical regions worldwide, growing in the shaded understory of rainforests from lowland areas to mountain cloud forests, where they serve as sensitive indicators of undisturbed forest conditions.

Taxonomy

Chroodiscus was first introduced by the Swiss lichenologist Johannes Müller Argoviensis in 1883 as a section of the genus Ocellularia. In his original description, Müller characterized the section by its layer being phyllactideum (containing green algae arranged in a specific pattern) and its apothecia (fruiting bodies) being pale or variously coloured. He described the type species, Ocellularia argillacea, as having a clay-coloured to pale or greenish-clay coloured thallus that was very thin, smooth, and interrupted by small globular swellings. The apothecia were measured at 0.2 to 0.5 millimetres wide and described as having broad, prominent margins. In 1890 he promoted the section to generic status.

Description

Chroodiscus forms a thin, smooth to slightly glossy crust (thallus) that grows directly on living leaves (foliicolous) and lacks a true . Its ascomata are strikingly : minute discs that split into several triangular lobules which then curl back to give a star-shaped outline; the exposed centre ranges from grey to scarlet-red, according to pigment chemistry. A pale, borders each disc, while the clear hymenium contains lax, branched paraphyses and no . The asci are Thelotrema-type (thin-walled, iodine-negative) and usually release eight hyaline ascospores that are transversely 3–7-septate, thin-walled and non-amyloid (about 12–30 × 4–7 μm). Many species synthesise orange-red anthraquinones or stictic acid-derivatives that tint the discs; others are chemically inert.

Species differ mainly in disc colour, spore size and chemistry: for example, C. argillaceus has grey discs and stictic acid, whereas C. mirificus develops vivid red discs rich in anthraquinones. The combination of star-shaped discs, absence of periphysoids and thin-walled, non-amyloid spores separates Chroodiscus from superficially similar genera such as Chapsa, Astrochapsa and Pseudochapsa, whose discs lack the lobules or whose spores react differently with iodine.

Ecology

The genus is strictly pantropical: records span Central and South America, West and Central Africa, Madagascar, India, Southeast Asia and north-east Australia. All known species are obligately foliicolous, colonising the shaded, humid understory of evergreen rainforests from lowland plains up to the montane cloud forest belt. A phenotype-based phylogeny indicates a South American origin in the mid-Cretaceous (roughly 120–100 Ma) followed by stepwise dispersal through Africa, India and Southeast Asia, with most present-day taxa now restricted to a single continent. Because they depend on intact, moist canopy microclimates, Chroodiscus species are considered sensitive indicators of undisturbed tropical forest and tend to disappear after forest clearance or prolonged drought.

Species

, Species Fungorum (in the Catalogue of Life) accepts 19 species of Chroodiscus:

References

References

  1. "''Chroodiscus''".
  2. (2008). "''Chroodiscus subhimalayanus'', a new species from India". Mycotaxon.
  3. (1992). "Neue foliicole Flechten I". Nova Hedwigia.
  4. (2000). "Studies on the lichen family Thelotremataceae in Tasmania. The genus ''Chroodiscus'' and its relatives". The Lichenologist.
  5. Lücking, Robert. (1999). "Addiciones y correcciones al conocimiento de la liquenoflora de Costa Rica. La familia Asterothyriaceae y el género ''Chroodiscus''". Cryptogamie, Mycologie.
  6. (2002). "Facultative parasitism and reproductive strategies in ''Chroodiscus'' (Ascomycota, Ostropales)". Stapfia.
  7. (2008). "Clave y guía ilustrada para géneros de Graphidaceae". GLALIA.
  8. (2008). "Historical biogeography and phenotype–phylogeny of ''Chroodiscus'' (lichenised Ascomycota: Ostropales: Graphidaceae)". Journal of Biogeography.
  9. Müller, J.. (1883). "Lichenologische Beiträge XVIII". Flora.
  10. Müller, J.. (1890). "Lichenes Epiphylli Novi".
  11. (2009). "Four new taxa of ''Chroodiscus'' (thelotremoid Graphidaceae) from Southeast Asia". The Bryologist.
  12. (1999). "Additions to the foliicolous lichen flora of the Ivory Coast and Guinea (Tropical West Africa)". Nordic Journal of Botany.
  13. "Synonymy: ''Chroodiscus'' (Müll. Arg.) Müll. Arg., Lich. Epiph. Novi: 18 (1890)". [[Species Fungorum]].
  14. Vězda, A.. (1975). "Foliicole Flechten aus der Republik Guinea (W-Afrika). III". Acta Musei Silesiae.

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graphidaceaetaxa-described-in-1883graphidales-generataxa-named-by-johannes-müller-argoviensislichen-genera