# Pleopsidium

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{{Short description|Genus of lichen-forming fungi}}
{{Automatic taxobox
| image = Gold Cobblestone Lichen (1246287349).jpg
| image_caption = ''[Pleopsidium flavum](/source/Pleopsidium_flavum)''
| taxon = Pleopsidium
| authority = [Körb.](/source/K%C3%B6rb.) (1855)
| subdivision_ranks = Species
| subdivision = ''[P. chlorophanum](/source/Pleopsidium_chlorophanum)''<br />
''[P. corrugatulum](/source/Pleopsidium_corrugatulum)''<br />
''[P. discurrens](/source/Pleopsidium_discurrens)''<br />
''[P. flavum](/source/Pleopsidium_flavum)''<br />
''[P. gobiense](/source/Pleopsidium_gobiense)''<br />
''[P. oxytonum](/source/Pleopsidium_oxytonum)''<br />
''[P. stenosporum](/source/Pleopsidium_stenosporum)''
''[P. tumidulum](/source/Pleopsidium_tumidulum)''
| synonyms_ref = <ref name="urlFungorum: Pleopsidium"/>
| synonyms = *''Gussonea'' {{au|[Tornab.](/source/Tornab.) (1848)}}
*''Acarosporomyces'' {{au|[Cif.](/source/Cif.) & [Tomas.](/source/Tomas.)}}
*''Biatorellopsis'' {{au|[C.W.Dodge](/source/C.W.Dodge) (1965)}}<ref name=Dodge1965/>
}}

'''''Pleopsidium''''' is a [genus](/source/genus) of [lichen](/source/lichen)-forming [fungi](/source/fungi) in the family [Acarosporaceae](/source/Acarosporaceae) (order Acarosporales). The widespread genus was [circumscribed](/source/circumscription_(taxonomy)) by lichenologist [Gustav Wilhelm Körber](/source/Gustav_Wilhelm_K%C3%B6rber) in 1855.<ref name=Koerber1855/> After a 2025 revision of the genus, it comprises eight species.

==Taxonomy==
In 2025, a taxonomic revision of the genus from China clarified species limits and expanded the genus's recognised diversity. Based on combined [morphological](/source/morphology_(biology)), chemical and [DNA sequence](/source/DNA_sequence) data, the authors identified a lineage of species lacking characteristic [fatty acid](/source/fatty_acid)s and formally described two new taxa, ''Pleopsidium tumidulum'' and ''P.&nbsp;corrugatulum''. These new species, together with ''P.&nbsp;gobiense'', form a strongly supported [clade](/source/clade) distinct from other fatty acid‑containing members of the genus. The revision provides updated diagnostic characters and phylogenetic context to improve identification and classification of ''Pleopsidium'' species.<ref name="Ai et al. 2025"/>

==Description==

''Pleopsidium'' is a genus of [crustose lichen](/source/crustose_lichen)s, typically forming small, patchy crusts divided into separate, block-like sections ({{lichengloss|areoles}}). Around the edges, these lichens may develop elongated or somewhat shaped ({{lichengloss|effigurate}}) lobes. The upper surface can be smooth or faintly wrinkled, and is most often a bright, vibrant yellow, though some specimens appear paler and slightly greenish. Beneath this surface layer, the [photosynthetic](/source/photosynthetic) partner is a [green alga](/source/green_alga)l cell type known as {{lichengloss|chlorococcoid}} algae, arranged in a continuous layer. The upper {{lichengloss|cortex}}—the thin protective "skin"” on top—is made of small, closely packed cells ({{lichengloss|prosoplectenchymatous}}), but there is no lower cortex on the underside.<ref name="Knudsen et al. 2021"/>

The reproductive structures, the [apothecia](/source/apothecia), sit either on the surface or are slightly embedded. Initially they are flat, gradually becoming more dome-shaped over time. These structures are often surrounded by a distinctive {{lichengloss|thalline margin}}, especially in younger apothecia. The exposed centre ({{lichengloss|disc}}) of the apothecium varies from yellow to brownish-yellow. Inside, numerous thin, branched, and [septate](/source/septum) threads called {{lichengloss|paraphyses}} help support the spore-producing tissue. The [asci](/source/ascus) (spore sacs) are club-shaped, contain over a hundred spores each, and have a characteristic dome at their tip. They display a blue reaction when treated with a combination of [potassium](/source/potassium) (K) and [iodine](/source/iodine) (I) chemicals. The spores themselves are [ellipsoid](/source/ellipsoid)al, colourless, and do not have internal divisions.<ref name="Knudsen et al. 2021"/>

In addition to [sexual reproduction](/source/sexual_reproduction) through spores, ''Pleopsidium'' also reproduces via tiny, flask-shaped structures called [pycnidia](/source/pycnidia), which are hidden within the thallus. These produce small, ellipsoidal [conidia](/source/conidia) (asexual spores) that narrow slightly at one end.<ref name="Knudsen et al. 2021"/>

Chemically, ''Pleopsidium'' species contain [rhizocarpic acid](/source/rhizocarpic_acid) as well as specific [fatty acid](/source/fatty_acid)s known as [acaranoic](/source/acaranoic_acid) and [acarenoic acid](/source/acarenoic_acid)s. Ecologically, these lichens are typically found growing on rocks ([saxicolous](/source/saxicolous_lichen)) in cool and humid environments, where they can often be identified by their distinctive bright yellow crusts.<ref name="Knudsen et al. 2021"/>

==Species==
* ''[Pleopsidium chlorophanum](/source/Pleopsidium_chlorophanum)'' {{au|(Wahlenb.) Arnold (1878)}}
* ''[Pleopsidium corrugatulum](/source/Pleopsidium_corrugatulum)'' {{au|C.C.Miao, Xin Yu Wang & Li S.Wang (2025)}}
* ''[Pleopsidium discurrens](/source/Pleopsidium_discurrens)'' {{au|(Zahlbr.) Obermayer (1996)}}
* ''[Pleopsidium flavum](/source/Pleopsidium_flavum)'' {{au|(Bellardi) Körb. (1855)}}
* ''[Pleopsidium gobiense](/source/Pleopsidium_gobiense)'' {{au|(H.Magn.) Hafellner (1993)}}
* ''[Pleopsidium oxytonum](/source/Pleopsidium_oxytonum)'' {{au|(Ach.) Rabenh. (1857)}}
* ''[Pleopsidium stenosporum](/source/Pleopsidium_stenosporum)'' {{au|(Stizenb. ex Hasse) K.Knudsen (2011)}}
* ''[Pleopsidium tumidulum](/source/Pleopsidium_tumidulum)'' {{au|M.Ai, Xin Yu Wang & Li S.Wang (2025)}}

==References==
<references>

<ref name="Ai et al. 2025">{{cite journal |last=Ai |first=Min |last2=Miao |first2=Cong Cong |last3=Worthy |first3=Fiona R. |last4=Nurtai |first4=Lazzat |last5=Zhang |first5=De Ning |last6=Zhang |first6=Sheng Bang |last7=Han |first7=Gui Lan |last8=Wang |first8=Li Song |last9=Wang |first9=Xin Yu |title=A new revision of the lichen genus ''Pleopsidium'' (Acarosporales, Acarosporaceae) in China reveals two new species |journal=MycoKeys |year=2025 |volume=120 |pages=255–276 |doi=10.3897/mycokeys.120.161566 |doi-access=free|pmc=12365682 }}</ref>

<ref name=Dodge1965>{{cite journal |last=Dodge |first=C.W. |title=Lichenological notes on the flora of the Antarctic continent. VI. New taxa from the Antarctic continent and adjacent islands |journal=Transactions of the American Microscopical Society |year=1965 |volume=84 |pages=507–529 |doi=10.2307/3224798 |jstor=3224798}}</ref>

<ref name=Koerber1855>{{cite book |last=Körber |first=G.W. |title=Systema lichenum Germaniae |year=1855 |page=113 |location=Breslau, Germany |publisher=Trewendt & Granier |language=la |url=https://www.biodiversitylibrary.org/page/23747791}}</ref>

<ref name="Knudsen et al. 2021">{{cite book |last1=Knudsen |first1=K. |last2=Kocourková |first2=J. |last3=Cannon |first3=P. |last4=Coppins |first4=B. |last5=Fletcher |first5=A. |last6=Simkin |first6=J. |year=2021 |title=Acarosporales: Acarosporaceae, including the genera ''Acarospora'', ''Caeruleum'', ''Myriospora'', ''Pleopsidium'', ''Sarcogyne'' and ''Trimmatothelopsis'' |series=Revisions of British and Irish Lichens |volume=12 |pages=5–6 |url=https://britishlichensociety.org.uk/sites/default/files/Acarosporaceae.pdf}}{{Open access}}</ref>

<ref name="urlFungorum: Pleopsidium">{{cite web |title=Synonyms: ''Pleopsidium'' Körb., Syst. lich. germ. (Breslau): 113 (1855) |url=http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=4221 |publisher=Species Fungorum. CAB International |access-date=2012-03-17}}</ref>

</references>

{{Taxonbar|from=Q7204599}}

Category:Acarosporales
Category:Lecanoromycetes genera
Category:Lichen genera
Category:Taxa named by Gustav Wilhelm Körber
Category:Taxa described in 1855

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