{{Short description|Species of lichen-forming fungus}} {{Use dmy dates|date=September 2025}} {{Use Oxford spelling|date=September 2025}} {{Speciesbox | image = Varicellaria lactea 1751992101.jpg | image_caption = | taxon = Varicellaria lactea | authority = (L.) I.Schmitt & Lumbsch (2012) | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = {{Collapsible list|bullets=on |''Lichen lacteus'' {{au|L. (1767)}} |''Lepra lactea'' {{au|(L.) F.H.Wigg. (1780)}} |''Variolaria lactea'' {{au|(L.) Pers. (1794)}} |''Psora lactea'' {{au|(L.) P.Gaertn. (1802)}} |''Pertusaria communis'' var. ''lactea'' {{au|(L.) Rabenh. (1840)}} |''Parmelia sordida'' f. ''lactea'' {{au|(L.) Torss. (1843)}} |''Lecanora rimosa'' f. ''lactea'' {{au|(L.) Schaer. (1850)}} |''Zeora stenhammarii'' * ''lactea'' {{au|(L.) Körb. (1855)}} |''Pertusaria lactescens'' b ''lactea'' {{au|(L.) Mudd (1861)}} |''Zeora rimosa'' f. ''lactea'' {{au|(L.) Kremp. (1861)}} |''Zeora lactea'' {{au|(L.) Arnold (1870)}} |''Pertusaria lactea'' {{au|(L.) Arnold (1872)}} |''Pertusaria lutescens'' var. ''lactea'' {{au|(L.) Zahlbr. (1927)}} |''Ochrolechia lactea'' {{au|(L.) Matzer & Hafellner (1990)}} |''Lichen lacteus'' {{au|Sibth. (1794)}} |''Lepra lactea'' {{au|DC. (1805)}} |''Parmelia tartarea'' var. ''lactea'' {{au|Torss. (1843)}} |''Lecanora pallescens'' f. ''lactea'' {{au|(Torss.) Schaer. (1850)}} |''Lepraria lactea'' {{au|(Torss.) Hue (1892)}} }} }}
'''''Varicellaria lactea''''' is a crustose lichen in the family Varicellariaceae.<ref name="CoL_7FHW4"/> It forms a relatively thick, white to grey‑white, {{lichengloss|matt}} crust that breaks into small, tile‑like patches and carries scattered white, powdery soralia (patches that shed tiny propagules); sexual fruiting bodies are rare, and when present they produce a single very large spore, with the lichen containing lecanoric and variolaric acids. Ecologically it is chiefly rock‑dwelling on lime-free siliceous and volcanic rocks in humid, shaded situations, and is widespread in Europe with confirmed records from the Azores, South Korea, and Alaska. First described by Carl Linnaeus in 1767 as ''Lichen lacteus'', the name was fixed by a neotype designated in 1994 and the species was transferred to ''Varicellaria'' in 2012 following a multi‑gene revision that separated the genus from ''Pertusaria'' in the strict sense. It is usually distinguished from the related ''V. hemisphaerica'' by its rock substrate and the presence of variolaric acid, whereas ''V. hemisphaerica'' is mainly bark‑dwelling and lacks that compound.
==Taxonomy==
The lichen was formally described as a new species by Carl Linnaeus in his 1767 work ''Mantissa plantarum''. In the protologue Linnaeus characterised it as a white, leprous lichen with hemispherical, same-coloured tubercles. He recorded the habitat as "everywhere on cliffs and stones", credited to Johan Zoëga, and added that the tubercles are "rather large".<ref name="Linnaeus 1767"/>
No original Linnaean material is preserved in the Linnaean Herbarium. To stabilise usage of the name, Per Magnus Jørgensen and colleagues designated a neotype.<ref name="Jørgensen et al. 1994"/> Imke Schmitt and H. Thorsten Lumbsch give its full citation—Sweden, Västergötland, Mularp, 6 Aug 1922, Vrang [= Malme, ''Lich. Suec.'' Exs. 848] (UPS)—which fixes the modern application of the name.<ref name="Schmitt et al. 2012"/> In the same 2012 treatment recasting ''Pertusaria'' and relatives, Schmitt and Lumbsch effected the new combination ''Varicellaria lactea'' (basionym ''Lichen lacteus'') and listed earlier placements under ''Lepra'', ''Variolaria'', ''Psora'', ''Zeora'', ''Pertusaria'', and ''Ochrolechia''.<ref name="Schmitt et al. 2012"/>
Their multi-gene analysis showed that the lecanoric acid, disc-apotheciate "Varicellaria group" forms a distinct, well-supported clade separate from ''Pertusaria'' in the strict sense, and they therefore broadened the circumscription of ''Varicellaria''. The key separates ''V. lactea'' from the bark-dwelling ''V. hemisphaerica'' chiefly by substrate and chemistry: ''V. lactea'' is sorediate on rock, usually with lecanoric and variolaric acids (rarely on bark), whereas ''V. hemisphaerica'' is on bark (rarely on rock) with lecanoric acid only.<ref name="Schmitt et al. 2012"/>
==Description==
''Varicellaria lactea'' forms a spreading, relatively thick thallus (the main body of the lichen) that appears white to greyish-white. Around the edges, a paler border called the {{lichengloss|prothallus}} is often visible, sometimes showing faint concentric zoning. The upper surface is typically smooth to slightly roughened and has a dull, {{lichengloss|matt}} appearance. It usually breaks up into a regular pattern of small, tile-like pieces known as {{lichengloss|areoles}}, which in this species are fairly coarse, measuring about 0.3–0.8 mm across. These can be flat but are often noticeably convex and vary in shape from rounded to angular.<ref name="Cannon et al. 2021"/> thumb|right|Close-up of the crustose thallus, showing cracked areoles with white soralia (scale bar = 1 mm) The lichen reproduces mainly by means of soralia, which are small, powdery patches that produce dispersal granules called soredia. The soralia are white, slightly raised, and usually 0.5–1.5 mm in diameter; they may be surrounded by a fragile collar of thallus tissue and sometimes appear floury or efflorescent. They are mostly scattered evenly across the thallus but can occasionally grow close together. The soredia themselves are tiny, about 100–160 micrometres (μm) wide, although they can cluster into larger aggregations.<ref name="Cannon et al. 2021"/>
Sexual reproductive structures are very uncommon in this species. When present, they occur as wart-like swellings that resemble soralia but are a little wider (0.4–0.7 mm). Each of these swellings usually contains one {{lichengloss|disc}}-shaped apothecium, rarely two. The discs are pale brown and at first covered by a frosty coating of white {{lichengloss|granules}}; they are often surrounded by a ragged collar of thallus tissue that also produces soredia. Within these apothecia, the spore-bearing sacs (asci) contain only a single ascospore each. The spores are exceptionally large, measuring 180–240 μm long and 60–100 μm wide, with very thick walls (up to 33 μm), and lack the fine internal banding seen in some other lichens. The asexual conidia are much smaller, rod-shaped structures only about 4.5 μm long and 0.5 μm wide.<ref name="Cannon et al. 2021"/>
Chemical spot tests provide useful characters for identification: the thallus reacts red with C and KC reagents, shows no colour change with K or Pd, and may fluoresce faintly bluish-green under ultraviolet light. These reactions correspond to the presence of the secondary metabolites (lichen products) lecanoric acid and variolaric acid.<ref name="Cannon et al. 2021"/>
==Habitat and distribution==
''Varicellaria lactea'' is chiefly saxicolous (rock-dwelling), occurring on hard, lime-free, siliceous rocks in humid, shaded to semi‑shaded positions, often on steep faces; it is also recorded on volcanic substrates such as basalt.<ref name="ITALIC 2025"/><ref name="DALIB 2025"/><ref name="Rodrigues et al. 2024"/> Field and phylogenetic work shows that the species is overwhelmingly rock‑dwelling, with the few reports from bark now understood to reflect confusion with the related corticolous ''V. hemisphaerica''; substrate rather than chemistry is the main separator between the two.<ref name="Kosecka & Oset 2024"/>
The species is widespread across Europe and locally frequent from lowlands into montane belts, and it also occurs in Macaronesia (Azores) on basaltic rock.<ref name="DALIB 2025"/><ref name="ITALIC 2025"/><ref name="Rodrigues et al. 2024"/> Beyond Europe, modern revisions confirm it from East Asia (South Korea) and from North America, where it was first documented for the United States in Alaska and has since been recorded in Alaskan national parks on overhanging and vertical rock walls.<ref name="Park et al. 2017"/><ref name="Tønsberg 2018"/><ref name="McCune et al. 2018"/>
==See also== * List of lichens named by Carl Linnaeus
==References== {{Reflist|colwidth=30em|refs=
<ref name="Cannon et al. 2021">{{cite book |last1=Cannon |first1=P. |last2=Kukwa |first2=M. |last3=Coppins |first3=B. |last4=Fletcher |first4=A. |last5=Sanderson |first5=N. |last6=Simkin |first6=J. |year=2021 |title=Pertusariales: Ochrolechiaceae, including the genera Lepra, Ochrolechia and Varicellaria |series=Revisions of British and Irish Lichens |volume=5 |page=16 |url=https://britishlichensociety.org.uk/sites/default/files/Ochrolechiaceae.pdf}} {{Open access}}</ref>
<ref name="CoL_7FHW4">{{Catalogue of Life |id=7FHW4 |title=''Varicellaria lactea'' (L.) I. Schmitt & Lumbsch |access-date=15 September 2025}}</ref>
<ref name="DALIB 2025">{{cite web |title=''Varicellaria lactea'' |year=2025 |website=Atlas of Czech Lichens (DALIB) |publisher=Institute of Botany, Czech Academy of Sciences |url=https://dalib.cz/en/taxon/info/Varicellaria%20lactea |access-date=15 September 2025}}</ref>
<ref name="ITALIC 2025">{{cite web |title=''Varicellaria lactea'' (L.) I. Schmitt & Lumbsch |year=2025 |last1=Nimis |first1=P.L. |last2=Conti |first2=M. |last3=Martellos |first3=S. |website=ITALIC – The Information System on Italian Lichens |publisher=University of Trieste |url=https://italic.units.it/index.php?num=2453&procedure=taxonpage |access-date=15 September 2025}}</ref>
<ref name="Jørgensen et al. 1994">{{cite journal |last1=Jørgensen |first1=Per M. |last2=James |first2=Peter W. |last3=Jarvis |first3=Charles E. |title=Linnaean lichen names and their typification |journal=Botanical Journal of the Linnean Society |volume=115 |issue=4 |year=1994 |pages=261–405 [326] |doi=10.1111/j.1095-8339.1994.tb01784.x}}</ref>
<ref name="Kosecka & Oset 2024">{{cite journal |last1=Kosecka |first1=Magdalena |last2=Oset |first2=Magdalena |year=2024 |title=A shift in substrate requirement might cause speciation of the lichenised fungi, ''Varicellaria hemisphaerica'' and ''V. lactea'' (Pertusariales, Ascomycota) |journal=Scientific Reports |volume=14 |issue=1 |article-number=23514 |doi=10.1038/s41598-024-74937-w|pmid=39384908 |pmc=11464505 |bibcode=2024NatSR..1423514K }}</ref>
<ref name="Linnaeus 1767">{{cite book |last=Linnaeus |first=C. |year=1767 |title=Mantissa Plantarum |page=132 |publisher=Lars Salvius |location=Stockholm |language=la |url=https://www.biodiversitylibrary.org/page/44260926}}</ref>
<ref name="McCune et al. 2018">{{cite journal |last1=McCune |first1=Bruce |last2=Arup |first2=Ulf |last3=Breuss |first3=Othmar |last4=Di Meglio |first4=Emily |last5=Di Meglio |first5=John |last6=Esslinger |first6=Theodore L. |last7=Magain |first7=Nicolas |last8=Miadlikowska |first8=Jolanta |last9=Miller |first9=Amy E. |last10=Muggia |first10=Lucia |last11=Nelson |first11=Peter R. |last12=Rosentreter |first12=Roger |last13=Schultz |first13=Matthias |last14=Sheard |first14=John W. |last15=Tønsberg |first15=Tor |last16=Walton |first16=James |year=2018 |title=Biodiversity and ecology of lichens of Katmai and Lake Clark National Parks and Preserves, Alaska |journal=Mycosphere |volume=9 |issue=4 |pages=859–930 |doi=10.5943/mycosphere/9/4/10|doi-access=free }}</ref>
<ref name="Park et al. 2017">{{cite journal |last1=Park |first1=J.S. |last2=Park |first2=S.-Y. |last3=Park |first3=C.-H. |last4=Kondratyuk |first4=S.Y. |last5=Oh |first5=S.-O. |last6=Hur |first6=J.-S. |year=2017 |title=Taxonomic revision of the lichen genera ''Pertusaria'', ''Varicellaria'', and ''Variolaria'' (Pertusariales, Ascomycota) in South Korea |journal=Mycobiology |volume=45 |issue=4 |pages=270–285 |doi=10.5941/MYCO.2017.45.4.270 |pmid=29371795 |pmc=5780359 |bibcode=2017Mycob..45..270P }}</ref>
<ref name="Rodrigues et al. 2024">{{cite journal |last1=Rodrigues |first1=A.F. |last2=Soares |first2=A.O. |last3=Borges |first3=I. |year=2024 |title=Lichen novelties from Corvo Island (Azores, Portugal) |journal=Biodiversity Data Journal |volume=12 |article-number=e140418 |doi=10.3897/BDJ.12.e140418 |doi-access=free |pmid=39781542 |pmc=11707517}}</ref>
<ref name="Schmitt et al. 2012">{{cite journal |last1=Schmitt |first1=Imke |last2=Otte |first2=Jürgen |last3=Parnmen |first3=Sittiporn |last4=Sadowska-Deś |first4=Anna |last5=Lücking |first5=Robert |last6=Lumbsch |first6=Thorsten |title=A new circumscription of the genus ''Varicellaria'' (Pertusariales, Ascomycota) |journal=MycoKeys |issue=4 |year=2012 |doi=10.3897/mycokeys.4.3545 |doi-access=free |pages=23–36}}</ref>
<ref name="Species Fungorum synonymy">{{cite web |title=GSD Species Synonymy. Current Name: ''Varicellaria lactea'' (L.) I. Schmitt & Lumbsch, in Schmitt, Otte, Parnmen, Sadowska-Deś, Lücking & Lumbsch, MycoKeys 4: 31 (2012) |url=https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=800041 |publisher=Species Fungorum |access-date=14 September 2025}}</ref>
<ref name="Tønsberg 2018">{{cite journal |last=Tønsberg |first=T. |year=2018 |title=''Varicellaria lactea'' new to the U.S.A. from Alaska |journal=Opuscula Philolichenum |volume=17 |pages=1–5 |doi=10.5962/p.386170 |url=https://www.biodiversitylibrary.org/page/63500883|doi-access=free }}</ref>
}}
{{Taxonbar |from1=Q21303130 |from2=Q108301833 |from3=Q108484402 |from4=Q10716233 |from5=Q21303516 |from6=Q107978182}}
Category:Pertusariales Category:Lichen species Category:Lichens described in 1767 Category:Lichens of Europe Category:Lichens of Subarctic America Category:Fungal taxa named by Carl Linnaeus