Phacopsis

Phacopsis is a genus of lichenicolous lichens. They grow on parasitically on members of the lichen family Parmeliaceae, of which they are also a member. Phacopsis species appear as partially immersed shiny brown to black apothecia that cause gall-like deformations on the thallus of the host lichen. Phacopsis are distinguished from each other by the shape of their spores, the colour and amyloid staining reaction of the hypothecium (a tissue layer under the spore-bearing hymenium), and the identity of their host lichen.

This article is about the genus of fungi. For the defunct legume genus, see Astragalus.

Phacopsis
Closeup of Phacopsis vulpina gall on Letharia sp.
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Lecanoromycetes
Order: Lecanorales
Family: Parmeliaceae
Genus: Phacopsis
Tul. (1852)
Type species
Phacopsis vulpina
Tul. (1852)

Taxonomy

Phacopsis was circumscribed by Edmond Tulasne in 1852 as a segregate of genus Abrothallus. Tulasne included three species: P. clemens, P. varia, and P. vulpina.[1] The last of these species was chosen as the type by Frederic Clements and Cornelius Shear (1931),[2] and by John Axel Nannfeldt (1932).[3] The other two species originally included in Phacopsis by Tulasne have since been referred to the genus Arthonia.

The higher-level classification of Phacopsis has changed several times in its taxonomic history. It has been placed in the order Arthoniales,[4] in the families Graphidaceae,[2] Lecanoraceae,[5] and also the Acarosporaceae.[6] Molecular phylogenetic analysis revealed its true placement in the family Parmeliaceae. This relationship is an example of adelpho-parasitism, in which the host species is closely related to the parasite.[7] Phacopsis is thought to have evolved from its ancestors during the Miocene (23.03 to 5.333 MYA).[8]

Description
Microscopy of Phacopsis vulpina asci. Several spores are visible in some of the asci, and the non-amyloid zone above the axial body is visible in some instances.

All species are endokapylic, meaning they possess a thallus in which no morphologically distinct lichenized structure is formed. Their apothecia are circular to irregular in shape, and may be dispersed or aggregated. The excipulum (the outer margin of the apothecium) range from colourless to blackish-brown, and often comprises "a few rows of cells which may be difficult to recognize". The hypothecium (a layer of dense hyphal tissue just below the hymenium) is colourless to blackish-brown. In some species, the hyphae in the hypothecium have a violet staining reaction with iodine; this characteristic can be used to distinguish between some species. The hymenium is colourless, pale brownish, or pale olivaceous. Asci (spore-bearing cells) are more or less club-shaped, and contain eight spores. They are surrounded by a thin outer amyloid wall layer and a thicker, non-amyloid inner wall layer; a non-amyloid zone rests above the axial body of the ascus.[9]

The ascospores are colourless, lack septa, and have smooth walls with occasional thickening at either end. The spores have a range of shapes; depending on the species, the following shapes have been recorded: ellipsoid, ovoid (egg-shaped), fusiform (spindle-shaped), lemon-shaped, falciform (sickle-shaped), fabiform (bean-shaped), and partly curved. The pycnidia of Phacopsis are immersed in the thallus of the host. Pycnospores have a bacilliform shape.[9]

Distribution

Members of the host family, Parmeliaceae, are found worldwide and the family has centres of distribution in Asia and in the Southern Hemisphere; Phacopsis probably occurs wherever the host does. A 1995 survey of Phacopsis accepted 13 taxa (eight species and several varieties) found on 41 host species on 20 genera. Many of Phacopsis species are poorly known, and have only been found at their type locality.[9]

Species

Phacopsis species are distinguished from each other by the characteristics of their ascospores, the colour and amyloid reaction of the hypothecium, and the identity of their host.[9] The following list of Phacopsis species indicates its name, taxonomic authority and year of publication, type locality, and host species (or genus).

  • Phacopsis australis Aptroot & Triebel (2002)[10] – southern Africa; host=Xanthoparmelia
  • Phacopsis cephalodioides (Nyl.) Triebel & Rambold (1988) – Denmark; host=Hypogymnia physodes
  • Phacopsis falcispora Triebel & Rambold (1995) – South Africa; host=Usnea maculata
  • Phacopsis lethariellae Hafellner & Rambold (1995) – Canary Islands; host=Lethariella intricata
  • Phacopsis menegazziae Triebel & Rambold (1995) – Nepal; host=Menegazzia terebrata
  • Phacopsis oroarcticae Zhurb. (2010)[11] – Severnaya Zemlya; host=Brodoa oroarctica
  • Phacopsis prolificans (Müll. Arg.) Triebel & Rambold (1992) – Japan; host=Platismatia interrupta
  • Phacopsis rufa (Müll.Arg.) Triebel (1992) – Australia; hosts=Cetrelia and Punctelia
  • Phacopsis thallicola (A.Massal.) Triebel & Rambold (1988) – New Zealand; hosts=Cetrelia sanguinea, Flavoparmelia caperata, Flavoparmelia praesignis, Parmotrema eurysacum, Rimelia cetraria
  • Phacopsis usneae C.W.Dodge (1948) – Kerguelen Islands; host=Usnea trachycarpa
  • Phacopsis vulpicidae Zhurb. & Diederich (2019)[12] – Renchinlkhümbe (Mongolia); host=Vulpicida
  • Phacopsis vulpina Tul. (1852) – France; host=Letharia

Several species formerly placed in Phacopsis have since been transferred to other genera. These include:

  • Phacopsis doerfeltii Alstrup & P.Scholz (1998) now Nesolechia doerfeltii (Alstrup & P.Scholz) Diederich (2018)[13]
  • Phacopsis huuskonenii Räsänen (1948) now Protousnea huuskonenii (Räsänen) Divakar, A.Crespo & Lumbsch (2017)[14]
  • Phacopsis lesdainii Vouaux (1914) now Echinodiscus lesdainii (Vouaux) Etayo & Diederich (2000)[15]
  • Phacopsis macrospora Uloth (1861) now Cercidospora macrospora (Uloth) Hafellner & Nav.-Ros. (2004)
  • Phacopsis mulleri Willey (1892) now Skyttella mulleri (Willey) D.Hawksw. & R.Sant. (1988)[16]
  • Phacopsis oxyspora (Tul.) Triebel & Rambold (1988) now Punctelia oxyspora (Tul.) Divakar, A.Crespo & Lumbsch (2017)[14]

References
  1. Tulasne, L.-R. (1852). "Mémoire pour servir à l'histoire organographique et physiologique des Lichens". Annales des Sciences Naturelles Botanique. Sér. 3 (in Latin). 17: 124.
  2. Clements, Frederic E.; Shear, Cornelius L. (1931). The Genera of Fungi (2nd ed.). New York: Hafner Publishing. p. 306.
  3. Nannfeldt, J.A. "Studien über die Morphologie und Systematik der nichtlichenisierten inoperculaten Discomyceten". Nova Acta Regiae Societatis Scientiarum Upsaliensis (in German). 8 (2): 1–368.
  4. Eriksson, OE; Hawksworth, David L. (1987). "An alphabetical list of the generic names of the ascomycetes - 1987". Systema Ascomycetum. 6 (1): 1–109.
  5. Hafellner, Josef (1987). "Studien über lichenicole Pilze und Flechten V. Über die Gattung Phacopsis Tul. emend. Körber (Lecanorales)". Herzogia (in German). 7: 343–352.
  6. Kirk PM, Cannon PF, David JC, Stalpers JA. (2001). Ainsworth & Bisby's Dictionary of the Fungi (9th ed.). Oxon, UK: CABI Bioscience. ISBN 978-0-85199-377-5.CS1 maint: uses authors parameter (link)
  7. Peršoh, Derek; Rambold, Gerhard (2002). "Phacopsis — A lichenicolous genus of the family Parmeliaceae" (PDF). Mycological Progress. 1 (1): 43–55. doi:10.1007/s11557-006-0004-0. S2CID 9935563.
  8. Divakar, Pradeep K.; Crespo, Ana; Wedin, Mats; Leavitt, Steven D.; Hawksworth, David L.; Myllys, Leena; et al. (2015). "Evolution of complex symbiotic relationships in a morphologically derived family of lichen-forming fungi". New Phytologist. 208 (4): 1217–1226. doi:10.1111/nph.13553. PMID 26299211.
  9. Triebel, Dagmar; Rambold, Gerhard; Elix, John A. (1995). "A conspectus of the genus Phacopsis (Lecanorales)". The Bryologist. 98 (1): 71–83. doi:10.2307/3243643. JSTOR 3243643.
  10. Aptroot, André; Triebel, Dagmar (2002). "A new Phacopsis species on Paraparmelia and Xanthoparmelia in southern Africa". Nova Hedwigia. 74 (3–4): 405–409. doi:10.1127/0029-5035/2002/0074-0405.
  11. Zhurbenko, Mikhail P. (2010). "New and interesting lichenicolous fungi from Eurasia. II" (PDF). Mycosphere. 1 (3): 213–222.
  12. Zhurbenko, Mikhail P.; Enkhtuya, Ochirbat; Javkhlan, Samiya (2019). "A first synopsis of lichenicolous fungi of Mongolia, with the description of five new species". Plant and Fungal Systematics. 64 (2): 345–366. doi:10.2478/pfs-2019-0023.
  13. Diederich, Paul; Lawrey, James D.; Ertz, Damien (2018). "The 2018 classification and checklist of lichenicolous fungi, with 2000 non-lichenized, obligately lichenicolous taxa". The Bryologist. 121 (3): 340–425. doi:10.1639/0007-2745-121.3.340. S2CID 92396850.
  14. Divakar, Pradeep K.; Crespo, Ana; Kraichak, Ekaphan; Leavitt, Steven D.; Singh, Garima; Schmitt, Imke; Lumbsch, H. Thorsten (2017). "Using a temporal phylogenetic method to harmonize family- and genus-level classification in the largest clade of lichen-forming fungi". Fungal Diversity. 84: 101–117. doi:10.1007/s13225-017-0379-z. S2CID 40674310.
  15. Etayo, Javier; Diederich, Paul (2000). "Echinodiscus lesdainii gen. et comb. nov., a new name for Phacopsis lesdainii Vouaux (lichenicolous Ascomycetes, Leotiales)". Bulletin de la Société des naturalistes luxembourgeois: 63–66.
  16. Hawksworth, David L.; Santesson, Rolf (1988). "Skyttella, a new genus for Phacopsis mulleri Willey (syn. Agyrium flavescens Rehm)" (PDF). Graphis Scripta. 2 (2): 33–37.


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