# Lithographa

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{{Short description|Genus of fungi}}
{{Use dmy dates|date=June 2025}}
{{Use Oxford spelling|date=June 2025}}
{{Automatic taxobox
| image =
| image_caption =
| taxon = Lithographa
| authority = [Nyl.](/source/Nyl.) (1857)
| type_species = ''Lithographa petraea''
| type_species_authority = (Nyl.) Nyl. (1856)
| subdivision_ranks = Species
| subdivision =''[L. graphidioides](/source/Lithographa_graphidioides)''<br />
''[L. olivacea](/source/Lithographa_olivacea)''<br />
''[L. opegraphoides](/source/Lithographa_opegraphoides)''<br />
''[L. serpentina](/source/Lithographa_serpentina)''<br />
''[L. skottsbergii](/source/Lithographa_skottsbergii)''<br />
''[L. tesserata](/source/Lithographa_tesserata)''
}}

'''''Lithographa''''' is a [genus](/source/genus) of [lichen](/source/lichen)-forming [fungi](/source/fungi) in the family [Xylographaceae](/source/Xylographaceae).<ref name="CoL_CDKFF"/> These [rock-dwelling lichens](/source/saxicolous_lichen) form tightly attached crusts that crack into small tile-like patches, typically appearing in shades of grey, brown, or nearly black. The genus includes six species found primarily in cold regions and high mountains, where they grow on hard rock surfaces in harsh environments. They reproduce through distinctive elongated or round fruiting bodies that appear as dark slits or discs embedded in the crusty surface.

==Taxonomy==

The genus was [circumscribed](/source/circumscription_(taxonomy)) in 1857 by the Finnish lichenologist [William Nylander](/source/William_Nylander_(botanist)), with ''Lithographa petraea'' assigned as the [type species](/source/type_species).<ref name="Nylander 1857"/> This species is now known as ''[Lithographa tesserata](/source/Lithographa_tesserata)''.<ref name="IF: Lithographa petraea"/> Nylander characterized ''Lithographa'' as having a [thallus](/source/thallus) that is evanescent (disappearing) or scarcely visible, with swollen [apothecia](/source/apothecia), a rim-like {{lichengloss|epithecium}}, thick convex margins, spore sacs containing numerous spores, and very slender, somewhat branched [paraphyses](/source/paraphyses).<ref name="Nylander 1857"/>

Rounded, sometimes gyrose apothecia in the related genus ''[Lambiella](/source/Lambiella)'' set it apart from slit-disc ''Lithographa''. Phylogenetic work places ''Lithographa'' in the same [clade](/source/clade) as bark-dwelling ''[Ptychographa](/source/Ptychographa)'', and both differ from ''[Wadeana](/source/Wadeana)'', which has a weaker exciple, reddish apothecia and a filamentous [green alga](/source/green_alga) (''[Trentepohlia](/source/Trentepohlia_(alga))'') as its {{lichengloss|photobiont}}.<ref name="Cannon et al. 2021"/>

==Description==

''Lithographa'' forms a tightly attached crust that cracks into small, tile-like patches ({{lichengloss|areoles}}). Each patch is coated by an {{lichengloss|epinecral layer}}—a thin film of dead fungal cells that lends a {{lichengloss|matt}} finish—and may be fringed by a barely visible {{lichengloss|prothallus}}, the pale [hypha](/source/hypha)l growth that first [colonises](/source/colonisation_(biology)) the rock. Thallus colour varies from pale grey through brown to almost black. Internally, the fungal partner houses minute, spherical [green alga](/source/green_alga)e (a {{lichengloss|chlorococcoid}} photobiont). Chemical analyses reveal a suite of [orcinol](/source/orcinol)-derived compounds, including both [depside](/source/depside)s and β-orcinol [depsidone](/source/depsidone)s.<ref name="Cannon et al. 2021"/>

The reproductive bodies are [apothecia](/source/apothecia) that range from elongate, slit-like {{lichengloss|lirellae}} to small angular or round {{lichengloss|discs}}. They sit flush with, or slightly above, the thallus and never bear a {{lichengloss|thalline rim}}; instead, the visible border is a {{lichengloss|true exciple}}—a dark, opaque ring of densely fused [hypha](/source/hypha)e that radiate outward from the base. The disc itself is a narrow, black fissure. Inside, the clear [hymenium](/source/hymenium) turns blue with iodine [staining](/source/staining), a sign of [amyloid](/source/amyloid_(mycology)) material in the [ascus](/source/ascus) walls, while a sparse mesh of branched [paraphyses](/source/paraphyses) threads the spore layer. [Asci](/source/ascus) are club-shaped and always eight-spored; when stained, the sides of the ascus apex turn dark blue, but a broad central plug remains unstained, a pattern shared with the ''[Trapelia](/source/Trapelia)'' type. Mature [ascospore](/source/ascospore)s are typically single-celled (aseptate), colourless and [ellipsoid](/source/ellipsoid)al; two southern-hemisphere species develop somewhat {{lichengloss|muriform}} spores, although it is suspected that they may not belong to this genus. Many species also produce immersed [pycnidia](/source/pycnidia) that release slender, rod-shaped [conidia](/source/conidia), but these structures are absent in the type species, ''L.&nbsp;tesserata''.<ref name="Cannon et al. 2021"/>

==Species==
*''[Lithographa graphidioides](/source/Lithographa_graphidioides)'' {{au|(Cromb.) Imshaug ex Coppins & Fryday (2006)}}<ref name="Coppins & Fryday 2006"/>
*''[Lithographa olivacea](/source/Lithographa_olivacea)'' {{au|Fryday (2004)}}<ref name="Fryday 2004"/>
*''[Lithographa opegraphoides](/source/Lithographa_opegraphoides)'' {{au|Coppins & Fryday (2006)}}<ref name="Coppins & Fryday 2006"/>
*''[Lithographa serpentina](/source/Lithographa_serpentina)'' {{au|Coppins & Fryday (2006)}}<ref name="Coppins & Fryday 2006"/>
*''[Lithographa skottsbergii](/source/Lithographa_skottsbergii)'' {{au|(Zahlbr.) Fryday & Coppins (2007)}}<ref name="Fryday & Coppins 2007"/>
*''[Lithographa tesserata](/source/Lithographa_tesserata)'' {{au|(DC.) Nyl. (1857)}}<ref name="Nylander 1857"/>

==References==
{{Reflist|colwidth=30em|refs=

<ref name="CoL_CDKFF">{{Catalogue of Life |id=CDKFF |title=''Lithographa'' |access-date=16 June 2025}}</ref>

<ref name="Coppins & Fryday 2006">{{cite journal |last1=Coppins |first1=Brian J. |last2=Fryday |first2=Alan M. |title=New or previously misunderstood species of ''Lithographa'' and ''Rimularia'' (Agyriaceae) from the southern subpolar region and western Canada |journal=The Lichenologist |volume=38 |issue=2 |year=2006 |pages=93–107 |doi=10.1017/S0024282906005512|bibcode=2006ThLic..38...93C }}</ref>

<ref name="Fryday 2004">{{cite journal |last1=Fryday |first1=A.M. |year=2004 |title=New species and records of lichenized fungi from Campbell Island and the Auckland Islands, New Zealand |journal=Bibliotheca Lichenologica |volume=88 |pages=127–146}}</ref>

<ref name="Fryday & Coppins 2007">{{cite journal |last1=Fryday |first1=Alan M. |last2=Coppins |first2=Brian J. |title=A second species of ''Lithographa'' with submuriform ascospores |journal=The Lichenologist |volume=39 |issue=3 |year=2007 |doi=10.1017/S0024282907006810 |pages=245–250 |bibcode=2007ThLic..39..245F |url=https://www.researchgate.net/publication/228678488}}</ref>

<ref name="Cannon et al. 2021">{{cite book |last1=Cannon |first1=P. |last2=Fryday |first2=A. |last3=Spribille |first3=T. |last4=Coppins |first4=B. |last5=Vondrák |first5=J. |last6=Sanderson |first6=N. |last7=Simkin |first7=J. |year=2021 |title=Baeomycetales: Xylographaceae, including the genera ''Lambiella'', ''Lithographa'', ''Ptychographa'' and ''Xylographa'' |series=Revisions of British and Irish Lichens |volume=17 |page=6 |url=https://britishlichensociety.org.uk/sites/default/files/Xylographaceae.pdf}}{{Open access}}</ref>

<ref name="IF: Lithographa petraea">{{cite web |title=Record Details: ''Lithographa petraea'' (Nyl.) Nyl., Act. Soc. linn. Bordeaux 21(4): 393 (1857) [1856] |url=https://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=394679 |publisher=[Index Fungorum](/source/Index_Fungorum) |access-date=16 June 2025}}</ref>

<ref name="Nylander 1857">{{cite journal |last=Nylander |first=W. |year=1857 |title=Prodromus lichenographiae Galliae et Algeriae |journal=Actes de la Société Linnéenne de Bordeaux |volume=21 |page=393 |language=la |url=https://www.biodiversitylibrary.org/page/3355875}}</ref>

}}

{{Taxonbar|from=Q6648027}}

Category:Baeomycetales
Category:Baeomycetales genera
Category:Lichen genera
Category:Taxa named by William Nylander (botanist)
Category:Taxa described in 1857

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