Pyrenodesmia variabilis

The species was first scientifically described in 1794 by Christiaan Hendrik Persoon, who called it Lichen variabilis. Abramo Bartolommeo Massalongo transferred the taxon to the genus Pyrenodesmia in 1852, a genus he circumscribed to include a group of four species (P. agardhiana, P. chalybaea, P. olivacea, and P. variabilis), all of which lacked anthraquinones (a class of secondary metabolites common in the family Teloschistaceae), and contained instead the insoluble lichen pigment {{lichengloss|Sedifolia-gray}}.

As its species epithet suggests, this lichen has a variable appearance. Several infraspecific taxa have been proposed (i.e., varieties and forms), but their taxonomic status remains unresolved. The species has been proposed for inclusion in several different genera in its early taxonomic history; in some instances authors have suggested that it would be better classed as a variety or form of another species. It has subsequently acquired an extensive synonymy. The genus Pyrenodesmia was resurrected by Ulf Arup and colleagues in 2013. Pyrenodesmia includes members of the former Caloplaca variabilis species complex; the uniting chemical characteristic of this group of lichens were shown to be phylogenetically distinct.

File:Caloplaca variabilis (Pers.) Müll. Arg 918275.jpg containing eight polarilocular {{lichengloss|ascospores}} with wide septa]]

Pyrenodesmia variabilis has a crust-like (crustose) thallus, which is grey to grey-brown, generally thin and somewhat smooth. Rarely, the colour is white. The thallus is {{lichengloss|areolate}}, meaning it has small, rounded, distinct patches. The central area of the thallus is darker than its edges, which may be bordered by a black prothallus. The {{lichengloss|photobiont}} partner is a member of the green algal genus Trebouxia.

Its apothecia, the fruiting bodies, are up to 1 mm in diameter. These apothecia are either sparsely scattered or densely crowded on the thallus surface, and they are {{lichengloss|sessile}}, meaning they are attached directly without a stalk. Initially flat, they tend to become slightly convex as they mature. The apothecia often have a thick, persistent margin with a grey-blue powdery ({{lichengloss|pruinose}}) appearance. The {{lichengloss|disc}} of the apothecia is black, while the {{lichengloss|epithecium}}, the layer above the spore-producing asci, is pale. The paraphyses, which are slender filament-like structures in the hymenium (spore-producing layer), broaden and become stouter towards their tips, reaching about 3 μm in diameter.

The {{lichengloss|ascospores}} of Pyrenodesmia variabilis number eight per ascus and are ellipsoid in shape, measuring 14–16 by 7–9 μm. They are {{lichengloss|polarilocular}}, with a septum (an internal dividing partition) that is 2–3 μm wide and can sometimes be as long as a third of the total length of the spore. When the thallus is treated with a solution of potassium hydroxide (i.e., the K spot test), it shows no reaction (K–), while the epithecium turns purple upon contact with this chemical (K+ purple).

Pyrenodesmia variabilis thrives on nutrient-rich limestone environments, flourishing on both natural boulders and human-made stonework. It is often found on horizontal surfaces such as the tops of chest tombs and the copings of walls and bridges. It is generally {{lichengloss|epilithic}}, meaning that it grows on the surface of rocks, but in a few instances, it has been recorded as {{lichengloss|endolithic}}–growing in the interior of rocks, under and around the rock crystals.

This species is widespread throughout England and Wales, including the English Midlands, with a distribution that extends sporadically to Scotland and Ireland. It also occurs in Bulgaria, Greece, Ukraine, and Russia. Pyrenodesmia variabilis is also found in the Northern Hemisphere, reaching as far as Central America. Its Asian distribution includes Nepal. In Western Asia, it occurs in Iraq and Turkey.

{{Reflist|colwidth=30em|refs=

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{{cite journal |last1=Baniya |first1=Chitra Bahadur |last2=Bhatta |first2=Pooja |year=2021 |title=Exploration of Lichen in Nepal |journal=Journal of Plant Resources |volume=19 |issue=1 |pages=19–54}}

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{{cite journal |last1=Christensen |first1=Steen N. |title=New or rarely reported lichens for Thraki, Greece II |journal=Herzogia |volume=33 |issue=1 |year=2020 |doi=10.13158/heia.33.1.2020.68 |pages=68–74}}

{{Catalogue of Life |id=4QRNT |title=Pyrenodesmia variabilis (Pers.) A. Massal. |access-date=6 February 2024}}

{{cite book |title=The Lichens of Great Britain and Ireland |edition=2nd |editor-last1=Smith |editor-first1=C.W. |editor-last2=Aptroot |editor-first2=A. |editor-last3=Coppins |editor-first3=B.J. |editor-last4=Fletcher |editor-first4=F. |editor-last5=Gilbert |editor-first5=O.L. |editor-last6=James |editor-first6=P.W. |editor-last7=Wolselely |editor-first7=P.A. |year=2009 |chapter=Caloplaca Th. Fr. (1860) |last1=Fletcher |first1=A. |last2=Laundon |first2=J.R. |location=London |publisher=The Natural History Museum |isbn=978-0-9540418-8-5 |page=262}}

{{cite journal |last1=Frolov |first1=Ivan |last2=Vondrák |first2=Jan |last3=Košnar |first3=Jiří |last4=Arup |first4=Ulf |title=Phylogenetic relationships within Pyrenodesmia sensu lato and the role of pigments in its taxonomic interpretation |journal=Journal of Systematics and Evolution |year=2020 |volume=59 |issue=3 |doi=10.1111/jse.12717 |pages=454–474}}

{{cite journal |last=Karim |first=Shram H. |last2=Salih |first2=Salah A. |last3=Al-Zubaidy |first3=Adel A. |title=A checklist of lichens from Iraq, with four new records of lichens from Iraq |journal=Lindbergia |volume=2021 |issue=1 |year=2021 |doi=10.25227/linbg.01140 |pages=1–6 |doi-access=free}}

{{cite journal |last=Kondratyuk |first=S.Y. |last2=Popova |first2=L.P. |last3=Khodosovtsev |first3=O.Y. |last4=Lőkös |first4=L. |last5=Fedorenko |first5=N.M. |last6=Kapets |first6=N.V. |title=The fourth checklist of Ukrainian lichen-forming and lichenicolous fungi with analysis of current additions |journal=Acta Botanica Hungarica |volume=63 |issue=1-2 |year=2021 |doi=10.1556/034.63.2021.1-2.8 |pages=97–163 [138]}}

{{cite journal |last=Massalongo |first=A.B. |year=1852 |title=Monografia dei licheni blasteniospori |journal=Atti dell'Istituto Veneto Scienze |series=ser. 2 |volume=3(App. 3) |page=125}}

{{cite journal |last1=Muggia |first1=Lucia |last2=Grube |first2=Martin |last3=Tretiach |first3=Mauro |title=A combined molecular and morphological approach to species delimitation in black-fruited, endolithic Caloplaca: high genetic and low morphological diversity |journal=Mycological Research |volume=112 |issue=1 |year=2008 |doi=10.1016/j.mycres.2007.02.001 |pages=36–49}}

{{cite journal |last=Persoon |first=C.H. |year=1794 |title=Einige Bemerkungen über die Flechten |trans-title=Some remarks on lichens |journal=Annalen der Botanik (Usteri) |volume=7 |pages=1–32 [26] |language=de}}

{{cite web |title=Synonymy. Current Name: Pyrenodesmia variabilis (Pers.) A. Massal., Atti Inst. Veneto Sci. lett., ed Arti, Sér. 2 3(App. 3): 125 (1852) |url=https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=403035 |publisher=Species Fungorum |access-date=6 February 2024}}

{{cite journal |last1=Volker |first1=John |last2=Güvenç |first2=Şaban |last3=Türk |first3=Ayşen |year=2020 |title=Additions to the checklist and bibliography of the lichens and lichenicolous fungi of Turkey |journal=Archive for Lichenology |volume=19 |pages=1–32 [23] |url=https://www.researchgate.net/344741387}}

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{{Taxonbar|from=Q28006440 |from2=Q10440570 |from3=Q107925160 |from4=Q108484444 |from5=Q108240513}}

Category:Teloschistales

Category:Lichen species

Category:Lichens described in 1794

Category:Lichens of Europe

Category:Lichens of North America

Category:Lichens of Central America

Category:Lichens of Western Asia

Category:Taxa named by Christiaan Hendrik Persoon