{{short description|Genus of lichens in the family Caliciaceae}} {{Use dmy dates|date=June 2025}} {{Use Oxford spelling|date=June 2025}} {{Automatic taxobox | image = Diplotomma chlorophaeum Jymm.jpg | image_caption = ''Diplotomma chlorophaeum'' | taxon = Diplotomma | authority = Flot. (1849) | type_species = ''Diplotomma alboatrum'' | type_species_authority = (Hoffm.) Flot. (1849) | subdivision_ranks = Species | subdivisions = | synonyms = *''Abacina'' {{au|Norman (1852)<ref name="Norman 1852"/>}} }}
'''''Diplotomma''''' is a genus of lichen-forming fungi in the family Caliciaceae.<ref name="CoL_CCXF8"/> The genus has a widespread distribution and contains 14 species. These lichens form firmly attached, crust-like patches that range from pale to dark grey and can appear smooth or cracked into an irregular mosaic pattern on their substrate. They produce black, disc-shaped fruiting bodies that start buried in the crust and later emerge to sit roughly flush with the surface, often dusted with a greyish-white powder.
==Taxonomy==
The genus was circumscribed by Julius von Flotow in 1849.<ref name="Flotow 1849"/> It was later wrapped into ''Buellia'' before being segregated from that genus by David Hawksworth in 1980.<ref name="Hawksworth 1980"/>
==Description==
''Diplotomma'' species form a firmly attached, crust-like thallus that sits on the substrate as a clearly delimited patch; in a few lichen-inhabiting (lichenicolous) taxa the thallus may be very thin or partly immersed in the host. The surface ranges from pale to dark grey and can appear smooth or cracked into an irregular mosaic. A dense outer {{lichengloss|cortex}} is packed with minute crystals that remain intact when a fragment is placed in potassium hydroxide solution (the K test). The algal partner ({{lichengloss|photobiont}}) is a single-celled green alga of the {{lichengloss|chlorococcoid}} type, which provides photosynthetic energy.<ref name="Cannon et al. 2020"/>
The sexual fruit-bodies (apothecia) start out buried in the thallus and later emerge so that the black {{lichengloss|disc}} sits roughly flush with the surface; a narrow, pale, scalloped rim of thallus tissue may encircle the disc in some species. The disc itself is often dusted with a greyish-white powder ({{lichengloss|pruina}}). Microscopic examination shows only a rudimentary {{lichengloss|true exciple}}, merging seamlessly with the underlying {{lichengloss|hypothecium}}, both of which are brown to nearly black. Thread-like paraphyses stand in the clear (I+ blue) hymenium; their tips swell and darken, giving the layer a tufted look. Each sac-like ascus contains eight ascospores that are divided by cross-walls into two or more cells (sometimes almost forming a brick pattern, {{lichengloss|muriform|submuriform}}) and have thick internal partitions ({{lichengloss|distosepta}}); mature spores are mid- to dark brown with rounded internal chambers ({{lichengloss|lumina}}). Vegetative reproduction occurs in sunken, flask-shaped pycnidia that appear as tiny brown dots; these release colourless, oval conidia capable of starting new thalli. Chemically the genus is characterised by aromatic depsides, compounds that help separate its species from superficially similar grey crustose lichens.<ref name="Cannon et al. 2020"/>
==Selected species== {{Asof|2025|June}}, Species Fungorum (in the Catalogue of Life) accepts 14 species of ''Diplotomma'': * ''Diplotomma alboatrum'' {{small|(Hoffm.) Flot. (1849)}} * ''Diplotomma cedricola'' {{small|(Werner) Etayo (2010)}} * ''Diplotomma chlorophaeum'' {{small|Szatala (1956)}} * ''Diplotomma epipolium'' {{small|(Ach.) Arnold (1869)}} * ''Diplotomma glaucoatrum'' {{small|(Nyl.) Cl.Roux (2015)}}<ref name="Roux 2015"/> * ''Diplotomma hedinii'' {{small|(H.Magn.) P.Clerc & Cl.Roux (2004)}}<ref name="Clerc 2004"/> * ''Diplotomma murorum'' {{small|(A.Massal.) Coppins (1980)}} * ''Diplotomma niveum'' {{small|(Anzi) Szatala (1956)}} * ''Diplotomma parasiticum'' {{small|(B.de Lesd.) Diederich, Cl.Roux & Haluwyn (2014)}} * ''Diplotomma pharcidium'' {{small|(Ach.) M.Choisy (1950)}} * ''Diplotomma porphyricum'' {{small|Arnold (1872)}} * ''Diplotomma rivas-martinezii'' {{small|(Barreno & A.Crespo) Barreno & A.Crespo (2000)}}<ref name="Molina & Crespo 2000"/> * ''Diplotomma venustum'' {{small|(Körb.) Körb. (1860)}} * ''Diplotomma vezdanum'' {{small|(P.Scholz & Knoph) Coppins (2002)}}
==References== {{Reflist|colwidth=30em|refs=
<ref name="Cannon et al. 2020">{{cite journal |last1=Cannon |first1=Paul |last2=Prieto |first2=Maria |last3=Coppins |first3=Brian |last4=Sanderson |first4=Neil |last5=Scheidegger |first5=Christoph |last6=Simkin |first6=Janet |year=2021 |title=Caliciales: Caliciaceae, including the genera ''Acolium'', ''Amandinea'', ''Buellia'', ''Calicium'', ''Diploicia'', ''Diplotomma'', ''Endohyalina'', ''Monerolechia'', ''Orcularia'', ''Pseudothelomma'', ''Rinodina'' and ''Tetramelas'' |journal=Revisions of British and Irish Lichens |volume=15 |pages=1–35 [24] |doi=10.34885/174}} {{Open access}}</ref>
<ref name="Clerc 2004">{{cite journal |last=Clerc |first=P. |year=2004 |title=Les champignons lichénisés de Suisse – Catalogue bibliographique complété par des données sur la distribution et l'écologie des espèces |trans-title=The lichenised fungi of Switzerland — A bibliographic catalogue supplemented with data on species distribution and ecology |journal=Cryptogamica Helvetica |volume=19 |page=292 |language=fr}}</ref>
<ref name="CoL_CCXF8">{{Catalogue of Life |id=CCXF8 |title=''Diplotomma'' |access-date=17 June 2025}}</ref>
<ref name="Flotow 1849">{{cite journal |last=Flotow |first=J.V. |title=Lichenes florae silesiae |journal=Jahresbericht der Schlesischen Gesellschaft für vaterländische Kultur |year=1849 |volume=27 |pages=98–143 |language=German}}</ref>
<ref name="Hawksworth 1980">{{cite journal |last1=Hawksworth |first1=D.L. |last2=James |first2=P.W. |last3=Coppins |first3=B.J. |year=1980 |title=Checklist of British lichen-forming, lichenicolous and allied fungi |journal=The Lichenologist |volume=12 |issue=1 |pages=1–115 |doi=10.1017/S0024282980000035|bibcode=1980ThLic..12....1H }}</ref>
<ref name="Molina & Crespo 2000">{{cite journal |last1=Molina |first1=M. del C.|last2=Crespo |first2=A. |year=2000 |title=Comparison of development of axenic cultures of five species of lichen-forming fungi |journal=Mycological Research |volume=104 |issue=5 |pages=595–602|doi=10.1017/S0953756299002014 }}</ref>
<ref name="Norman 1852">{{cite journal |last=Norman |first=Johannes M. |title=Conatus praemissus redactionis novae generum nonnullorum Lichenum in organis fructificationes vel sporis fundatae |journal=Nytt Magazin for Naturvidenskapene |year=1852 |volume=7 |pages=213–52 |language=la}}</ref>
<ref name="Roux 2015">{{cite journal |last=Roux |first=C. |year=2015 |title=Validigo de du kombinaĵoj publikigitaj far ROUX inter 2005 kaj 2014 — Validation de deux combinaisons publiées par Roux entre 2005 et 2014 |trans-title=Validation of two combinations published by Roux between 2005 and 2014 |journal=Bulletin de la Société Linnéenne de Provence |volume=66 |pages=91–92 |language=eo}}</ref>
}}
{{Taxonbar|from=Q5280002}}
Category:Caliciales Category:Lichen genera Category:Caliciales genera Category:Taxa described in 1849 Category:Taxa named by Julius von Flotow