Psoroma

Psoroma is a genus of lichen-forming fungi in the family Pannariaceae. The widespread genus contains about 30 species,^[4] most of which are found in south temperate regions.^[5]

Psoroma
Psoroma hypnorum
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Lecanoromycetes
Order:	Peltigerales
Family:	Pannariaceae
Genus:	Psoroma Ach. ex Michx. (1803)
Type species
Psoroma hypnorum (Vahl) Gray (1821)
Synonyms[1]
Phloeopannaria Zahlbr. (1941)[2] Psoromatomyces Cif. & Tomas. (1953)[3]

Taxonomy

The genus was circumscribed by the French botanist André Michaux in 1803.^[6]

Some species formerly in Psoroma were transferred to the new genera Psorophorus and Xanthopsoroma in 2010.^[7] The genus Joergensenia was erected in 2008 to contain the species formerly known as Psoroma cephalodinum.^[8]

Description

The genus Psoroma is characterised by its small scale-like thallus, with an underlying layer that is barely noticeable. It houses a green algal photobiont, possibly the algae Myrmecia, which collaborates with the fungus to perform photosynthesis. Psoroma species have cephalodia, structures containing the cyanobacterium Nostoc.^[9]

The reproductive organs, known as ascomata, are apothecial in form—essentially sessile and somewhat cup-shaped with a raised, enduring edge. Within these structures, the supporting filaments, or paraphyses, may be simple or branch towards their tips, which do not expand or form a cap, staining a dusky blue when iodine is applied. The spore-producing asci are elongated, either club-shaped or cylindrical, featuring a distinctive structure at their tips where a central tube stains blue with iodine within a lighter-staining area, surrounded by a clear amyloid ring.^[9]

Spores produced by Psoroma are single-celled, colourless, and often contain one or two large oil droplets. Their shape is ellipsoidal, with a surface that is warty or ridged, and somewhat pointed at the ends. For asexual reproduction, Psoroma develops pycnidia, which are pale brown, and produces simple, rod-shaped, colourless conidia.^[9]

Chemically, Psoroma usually lacks detectable secondary metabolites (lichen products) through thin-layer chromatography, although in rare cases, porphyrilic acid and related compounds may be present.^[9]

Species

As of March 2024^[update], Species Fungorum (in the Catalogue of Life) accepts 28 species of Psoroma.^[4]

Psoroma sphinctrinum

• Psoroma absconditum Øvstedal (2008)^[10]
• Psoroma antarcticum S.G.Hong & Elvebakk (2018)^[11] – Antarctica
• Psoroma asperellum Nyl. (1869)
• Psoroma caliginosum Stirt. (1877)
• Psoroma capense Elvebakk, S.G.Hong & Rämä (2020) – South Africa^[12]
• Psoroma cinnamomeum Malme (1925)
• Psoroma cyanosorediatum P.M.Jørg. (2004)
• Psoroma dichroum (Hook.f. & Taylor) P.M.Jørg. (2014)
• Psoroma echinaceum P.M.Jørg. & Wedin (1999)^[13]
• Psoroma esterhuyseniae Elvebakk (2020) – South Africa^[12]
• Psoroma filicicola P.M.Jørg. & Sipman (2006)
• Psoroma fruticulosum P.James & Henssen (1983)^[14]
• Psoroma geminatum P.M.Jørg. (1999)^[13]
• Psoroma hirsutulum Nyl. ex Cromb. (1875)
• Psoroma hypnorum (Vahl) Gray (1821)^[15]
• Psoroma inflatum Elvebakk (2021)^[16] – New Zealand
• Psoroma macquariense C.W.Dodge (1970)^[17] – Antarctica
• Psoroma macrosporum (P.M.Jørg. & Palice) P.M.Jørg. (2014)
• Psoroma multifidum P.M.Jørg. (2004)^[15]
• Psoroma nigropunctatum Elvebakk & Elix (2021)^[18] – Australia
• Psoroma nivale Fryday, Elvebakk, F.L.Anderson & J.Gagnon (2019)^[19] – Quebec, Canada
• Psoroma obscurius (Nyl.) P.M.Jørg. (2014)
• Psoroma orphninum (Hue) P.M.Jørg. (2014)
• Psoroma paleaceum (Fr.) Nyl. (1855)
• Psoroma pholidotoides (Nyl.) Trevis. (1869)
• Psoroma polychidioides (Zahlbr.) P.M.Jørg. (2014)
• Psoroma saccharatum Scutari & Calvelo (1995)^[20] – Argentina
• Psoroma sphinctrinum (Mont.) Nyl. (1855)
• Psoroma xanthorioides (P.M.Jørg.) P.M.Jørg. (2014)
• Psoromaria rosulata (P.M.Jørg. & D.J.Galloway) P.M.Jørg. & H.L.Andersen (2015)
• Psoromaria versicolor (Müll.Arg.) P.M.Jørg. & H.L.Andersen (2015)

References

1. "Psoroma Ach. ex Michx. 1803". MycoBank. International Mycological Association. Retrieved 2012-02-25.
2. Zahlbruckner, A. (1941). "Lichenes Novae-Zelandiae a cl H. H. Allan eiusque collaboratoribus lecti". Denkschriften der Akademie der Wissenschaften (Wien), Math.-nat. Kl. (in German). 104: 249–380 [275].
3. Ciferri, R.; Tomaselli, R. (1953). "Saggio di una sistematica micolichenologica". Atti dell'Istituto Botanico della Università e Laboratorio Crittogamico di Pavia (in Italian). 10 (1): 25–84.
4. "Psoroma". Catalogue of Life. Species 2000: Leiden, the Netherlands. Retrieved 31 March 2024.
5. Kirk, P.M.; Cannon, P.F.; Minter, D.W.; Stalpers, J.A. (2008). Dictionary of the Fungi (10th ed.). Wallingford, UK: CAB International. p. 575. ISBN 978-0-85199-826-8.
6. Michaux, A. (1803). Flora Boreali-Americana (in Latin). Vol. 2. p. 321.
7. Elvebaak, A.; Robertsen, E.H.; Park, C.H.; Hong, S.G. (2010). "Psorophorus and Xanthopsoroma, two new genera for yellow-green, corticolous and squamulose lichen species, previously in Psoroma". The Lichenologist. 42 (5): 563–585. doi:10.1017/S0024282910000083.
8. Passo, A.; Stenroos, S.; Calvelo, S. (2008). "Joergensenia, a new genus to accommodate Psoroma cephalodinum (lichenized Ascomycota)". Mycological Research. 112 (12): 1465–1474. doi:10.1016/j.mycres.2008.06.025. PMID 18675347.
9. Cannon, P.; Aptroot, A.; Coppins, B.; Sanderson, N.; Simkin, J. (2021). Peltigerales: Pannariaceae, including the genera Fuscopannaria, Leptogidium, Nevesia, Pannaria, Parmeliella, Pectenia, Protopannaria and Psoroma (PDF). Revisions of British and Irish Lichens. Vol. 9. p. 14.
10. Øvstedal, D.O.; Gremmen, N.J.M. (2008). "Additions and corrections to the lichens of Heard Island". The Lichenologist. 40 (3): 233–242. doi:10.1017/S002428290800741X.
11. Park, Chae Haeng; Hong, Soon Gyu; Elvebakk, Arve (2018). "Psoroma antarcticum, a new lichen species from Antarctica and neighbouring areas". Polar Biology. 41 (6): 1083–1090. Bibcode:2018PoBio..41.1083P. doi:10.1007/s00300-018-2265-x.
12. Elvebakk, Arve; Hong, Soon Gyu; Park, Chae Haeng; Rämä, Teppo (2020). "Psoroma capense and P. esterhuyseniae (Pannariaceae), two new alpine species from South Africa". The Lichenologist. 52 (5): 345–352. doi:10.1017/S0024282920000377. hdl:10037/20103.
13. Jørgensen, P.M.; Wedin, M. (1999). "On Psoroma species from the Southern Hemisphere with cephalodia producing vegetative dispersal units". Lichenologist. 31 (4): 341–347. doi:10.1017/S0024282999000456.
14. Henssen, A.; Renner, B.; Marton, K.; James, P.W.; Galloway, D.J. (1983). "Studies in the lichen genus Psoroma 2. Psoroma fruticulosum and Psoroma rubromarginatum". Mycotaxon. 18 (1): 29–48.
15. Jørgensen, P.M. (2004). "Further contributions to the Pannariaceae (lichenized Ascomycetes) of the Southern Hemisphere". Bibliotheca Lichenologica. 88: 229–253.
16. Elvebakk, Arve (2021). "Psoroma inflatum, a new alpine lichen from New Zealand" (PDF). Australasian Lichenology. 89: 49–53.
17. Dodge, C.W. (1970). "Lichenological notes on the flora of the Antarctic Continent and the Subantarctic islands. IX-XI". Nova Hedwigia. 19 (3–4): 439–502.
18. Elvebakk, Arve; Elix, John A. (2021). "Psoroma nigropunctatum sp. nov., an alpine lichen in south-eastern Australia related to P. buchananii" (PDF). Australasian Lichenology. 89: 54–61.
19. Fryday, Alan M.; Elvebakk, Arve; Anderson, Frances L.; Gagnon, Jean Y. (2019). "Psoroma nivale (Pannariaceae, lichenized Ascomycota) a new species with dark, elongate squamules and bacilliform ascospores from arctic Québec, Canada". The Lichenologist. 51 (5): 419–429. doi:10.1017/S0024282919000288. hdl:10037/18052.
20. Scutari, N.C.; Calavelo, S. (1995). "A new species of Psoroma (pannariaceae, lichenized Ascomycotina) from Tierra del Fuego, Argentina". Annales Botanici Fennici. 32 (1): 5–61 [56].