Polymeridium
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Dothideomycetes
Order: Trypetheliales
Family: Trypetheliaceae
Genus: Polymeridium
(Müll.Arg.) R.C.Harris (1980)
Type species
Polymeridium contendens
(Nyl.) R.C.Harris
Synonyms
  • Arthopyrenia sect. Polymeridium Müll.Arg. (1883)
  • Exiliseptum R.C.Harris (1986)

Polymeridium is a genus of lichen-forming fungi in the family Trypetheliaceae.[1] Species in the genus are corticolous (bark-dwelling) and typically occur in tropical areas.

Taxonomy

The genus was originally circumscribed as a section of the genus Arthopyrenia by Swiss lichenologist Johannes Müller Argoviensis in 1883. Richard Harris elevated it to generic status in 1980.[2] In his 1993 revision of the genus, Harris identified 19 species. Utilizing a broad species concept, he acknowledged the presence of variations in chemistry and hamathecial inspersion within individual species.[3] André Aptroot and Marcela Cáceres again revised the genus in 2014, using the absence or presence of lichexanthone and the absence or presence of hamathecial inspersion as distinguishing characters for species. The monotypic genus Exiliseptum was incorporated into Polymeridium, as it only differs in one characteristic from several Polymeridium species and does not possess any unique features. As a result of this work, the number of species in the genus increased from 27 to 53.[4]

Description

Polymeridium is characterized by a white to yellowish or grey thallus, which is usually ecorticate (i.e., it lacks a cortex). Its ascomata, the fruiting bodies of the lichen, are simple or fused, appearing as black, spherical to pyriform structures that emerge from the substratum. The ostiole, or opening of the ascomata, can be apical to lateral, brown to black, or exhibit a red anthraquinone colour.[4]

The hamathecium, which refers to the filamentous tissue within the ascomata, is colourless and may contain hyaline or red oil droplets that turn green when treated with potassium hydroxide (KOH) solution. Ascospores are the reproductive spores of the lichen and typically occur in groups of 4 to 8 per ascus. They are colourless, ellipsoid to fusiform in shape, with rounded to subacute ends, and symmetrically 3 to 13-septate to muriform. The ascospores are not constricted at the septa and are sometimes surrounded by a thin to 2–5 μm-thick gelatinous sheath. The septa within the ascospores are not thickened, and the lumina are rectangular and slightly rounded, but not diamond-shaped.[4]

Conidiomata, or structures that produce conidia (asexual spores), are rather rare in the genus Polymeridium. In terms of secondary chemistry, the thallus occasionally contains lichexanthone, while anthraquinones are rarely present in the ostiole or hamathecium.[4]

Species

References

  1. ↑ Wijayawardene, Nalin; Hyde, Kevin; Al-Ani, Laith Khalil Tawfeeq; Somayeh, Dolatabadi; Stadler, Marc; Haelewaters, Danny; et al. (2020). "Outline of Fungi and fungus-like taxa". Mycosphere. 11: 1060–1456. doi:10.5943/mycosphere/11/1/8. hdl:10481/61998.
  2. ↑ Tucker, Shirley C.; Harris, Richard C. (1980). "New and noteworthy pyrenocarpous lichens from Louisiana and Florida". The Bryologist. 83 (1): 1–20. doi:10.2307/3242389. JSTOR 3242389.
  3. ↑ Harris, R.C. (1993). "A revision of Polymeridium (Muell. Arg.) R.C.Harris (Trypetheliaceae)". O Boletim do Museu Paraense Emílio Goeldi, Série Botânica. 7: 619–644.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Aptroot, A.; Cáceres, M.E.S. (2014). "A refined species concept in the tropical microlichen genus Polymeridium (Trypetheliaceae) doubles the number of known species, with a world key to species". Nova Hedwigia. 98: 1–29.
  5. ↑ Aptroot, A.; Ferraro, L.I. (2000). "A new species of Polymeridium (Trypetheliaceae), non-lichenized Ascomycetes from the Macrosistema Iberá, Corrientes, Argentina". Bonplandia. 10 (1–4): 139–141.
  6. 1 2 Aptroot, André; Menezes, Aline Anjos; de Lima, Edvaneide Leandro; Xavier-Leite, Amanda Barreto; Cáceres, Marcela Eugenia da Silva (2013). "New species of Polymeridium from Brazil expand the range of known morphological variation within the genus". The Lichenologist. 45 (4): 545–552. doi:10.1017/s0024282913000200.
  7. 1 2 Aptroot, André; Mendonça, Cléverton de Oliveira; Andrade, Danyelly Santos; Silva, Jeanne dos Reis; Martins, Suzana Maria de Azevedo; Gumboski, Emerson; Fraga, Carlos Augusto Vidigal; Cáceres, Marcela Eugenia da Silva (2016). "New Trypetheliaceae from northern and southern Atlantic rainforests in Brazil". The Lichenologist. 48 (6): 713–725. doi:10.1017/s0024282916000037.
  8. ↑ Aptroot, A.; Weerakoon, G. (2018). "Three new species and ten new records of Trypetheliaceae (Ascomycota) from Sri Lanka". Cryptogamie, Mycologie. 39 (3): 373–377. doi:10.7872/crym/v39.iss3.2018.373.
  9. ↑ Aptroot, André; Ertz, Damien; Etayo Salazar, Javier Angel; Gueidan, Cécile; Mercado Diaz, Joel Alejandro; Schumm, Felix; Weerakoon, Gothamie (2016). "Forty-six new species of Trypetheliaceae from the tropics". The Lichenologist. 48 (6): 609–638. doi:10.1017/s002428291600013x.
  10. ↑ Flakus, Adam; Kukwa, Martin; Aptroot, André (2016). "Trypetheliaceae of Bolivia: an updated checklist with descriptions of twenty-four new species". The Lichenologist. 48 (6): 661–692. doi:10.1017/s0024282915000559.
  11. ↑ Etayo, Javier; Aptroot, André (2017). "New and interesting lichens from Panama". The Bryologist. 120 (4): 501–510. doi:10.1639/0007-2745-120.4.501.
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