# Gymnoderma

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***Gymnoderma*** is a [genus](/source/Genus) of [lichen](/source/Lichen)-forming [fungi](/source/Fungi) in the family [Cladoniaceae](/source/Cladoniaceae). Originally established in 1860 by the Finnish lichenologist [William Nylander](/source/William_Nylander_(botanist)), this small genus is characterised by forming mats of small, yellow-green scales dotted with spherical brown [fruiting bodies](/source/Fruiting_bodies). The genus is distinguished from related lichens by a unique microscopic feature: its spore-containing structures ([asci](/source/Ascus)) turn deep blue when [stained](/source/Staining) with iodine, which is uncommon among members of the Cladoniaceae.

## Taxonomy

The genus was [circumscribed](/source/Circumscription_(taxonomy)) by the Finnish lichenologist [William Nylander](/source/William_Nylander_(botanist)) in 1860.[1] Nylander assigned *[Gymnoderma coccocarpum](/source/Gymnoderma_coccocarpum)* as the [type species](/source/Type_species) in 1869; this species was originally collected from the [Himalayas](/source/Himalayas).[2] Historical confusion affected allied names: [Edvard Vainio](/source/Edvard_Vainio)'s genus *Baeoderma* (type: *Baeoderma madagascareum*, based on Nylander's *Heterodea madagascarea*) has been overlooked in some sources but is referable to *Gymnoderma*. Re-examination of [Mascarenes](/source/Mascarenes) material from [Mauritius](/source/Mauritius) and [Réunion](/source/R%C3%A9union) shows that Nylander's African [taxon](/source/Taxon) is the same species as *G. coccocarpum*, extending *Gymnoderma* to Africa; this [synonymy](/source/Synonym_(taxonomy)) rests on [morphology](/source/Morphology_(biology)), as matching [DNA sequences](/source/DNA_sequence) were not available for those island specimens. Earlier misplacements, for example confusion with *[Bunodophoron madagascareum](/source/Bunodophoron_madagascareum)*, have been clarified.[3]

Multi-[locus](/source/Locus_(genetics)) phylogenies of Cladoniaceae place *Gymnoderma* in a [clade](/source/Clade) close to *[Carassea](/source/Carassea)* and *[Pycnothelia](/source/Pycnothelia)*, [sister](/source/Sister_taxon) to the much larger genus *[Cladonia](/source/Cladonia)*. Within the Cladoniaceae, the key diagnostic for *Gymnoderma* is its entirely amyloid [ascus](/source/Ascus) (the spore sac), a feature repeatedly reported and used to delimit the genus.[3]

## Description

The [thallus](/source/Thallus) forms overlapping (small, leaf-like scales) with a green-yellow upper surface and a white lower surface; the margins are (finely scalloped). [Podetia](/source/Podetia) (the upright stalks that many *Cladonia* relatives develop) are absent or very short in *Gymnoderma*, and when present they are solid and arise at the squamule margins. Fruiting bodies ([apothecia](/source/Apothecia)) are common; they are pale brown, more or less spherical, and (sitting directly on the thallus without a stalk). In practical terms, a mat of yellow-green scales dotted with small brown balls is a typical field appearance for the genus.[3]

Microscopically, the ascus is entirely [amyloid](/source/Amyloid_(mycology)) (meaning it turns a deep blue when [stained](/source/Staining) with iodine solution) which is an uncommon state in Cladoniaceae and helps separate *Gymnoderma* from superficially similar genera.[3]

## Species

- *[Gymnoderma coccocarpum](/source/Gymnoderma_coccocarpum)* [2]
- *[Gymnoderma favosum](/source/Gymnoderma_favosum)* [4]
- *[Gymnoderma insulare](/source/Gymnoderma_insulare)* [5]
- *[Gymnoderma sinuatum](/source/Gymnoderma_sinuatum)* [6]

Some species once classified in *Gymnoderma* have since been transferred to other genera. These include:

- *Gymnoderma lineare* = *[Cetradonia linearis](/source/Cetradonia_linearis)*[7]
- *Gymnoderma melacarpum* = *[Neophyllis melacarpa](/source/Neophyllis_melacarpa)*[8]
- *Gymnoderma rugosum* = *[Stereum rugosum](/source/Stereum_rugosum)*[9]

## References

1. Nylander, W. (1860). ["De Lichenibus nonnullis europaeis"](https://www.biodiversitylibrary.org/page/53210) [On some European lichens] (in Latin). *Flora (Regensburg)*. **43**: 545–547.

1. Nylander, W. (1869). [*Synopsis Methodica Lichenum Omnium hucusque Cognitorum, Praemissa Introductione Lingua Gallica*](https://bibdigital.rjb.csic.es/viewer/12891/?offset=#page=26&viewer=picture&o=bookmark&n=0&q=) [A methodical synopsis of all lichens known to date, with an introduction prefaced in the French language] (in Latin). Vol. 2. p. 26.

1. Pino-Bodas, Raquel; Ahti, Teuvo; Stenroos, Soili (3 April 2020). ["Taxonomic Notes on Pycnothelia Dufour and Gymnoderma Nyl. (Cladoniaceae) in Madagascan Region"](https://helda.helsinki.fi/bitstream/10138/316719/1/Madagascan_Pycnothelia.pdf). *Cryptogamie, Mycologie*. **41** (5): 109–118. [doi:10.5252/cryptogamiemycologie2020v41a5](https://doi.org/10.5252/cryptogamiemycologie2020v41a5). [hdl:10138/316719](https://hdl.handle.net/10138/316719). [ISSN 0181-1584](https://www.worldcat.org/issn/0181-1584). Retrieved 18 October 2025.

1. Hoffmann, Georg Franz (1811). [*Vegetabilia in Hercyniae subterraneis collecta*](https://archive.org/details/Vegetabilia-in-Hercyniae-subterraneis-collecta-iconibus-descriptionibus-et-observa-PHAIDRA_o_331697/page/n73/mode/2up) [Plants collected in the underground spaces of the Harz Mountains] (in Latin). Nuremberg: Impensis Joan. Frid. Frauenholz. p. tab. 16.

1. Yoshimura, Isao & Sharp, Aaron J. (1968). "A revision of the genus *Gymnoderma*". *American Journal of Botany*. **55** (5): 635–640. [doi:10.2307/2440620](https://doi.org/10.2307/2440620). [JSTOR 2440620](https://www.jstor.org/stable/2440620)

1. Humboldt, F.W.H.A. von. (1793). [*Florae Fribergensis Specimen plantas cryptogamicas praesertim subterraneas exhibens*](https://www.biodiversitylibrary.org/page/58251940) (in Latin). Berlin: H.A. Rottmann. p. 109.

1. ["Records details: *Gymnoderma lineare* (A. Evans) Yoshim. & Sharp, Am. J. Bot. 55: 639 (1968)"](http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=345047). [Index Fungorum](/source/Index_Fungorum). Retrieved 18 October 2025.

1. ["Records details: *Gymnoderma melacarpum* (F. Wilson) Yoshim., J. Jap. Bot. 48: 287 (1973)"](http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=342106). [Index Fungorum](/source/Index_Fungorum). Retrieved 18 October 2025.

1. ["Records details: *Gymnoderma rugosum* (Pers.) Hoffm., Veg. Herc. subterr.: 29, tab. 16:2 (1811)"](http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=497277). [Index Fungorum](/source/Index_Fungorum). Retrieved 18 October 2025.

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