Biology:Asteristion
| Asteristion | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Graphidales |
| Family: | Graphidaceae |
| Genus: | Asteristion Leight. (1870) |
| Type species | |
| Asteristion erumpens Leight. (1870)
| |
| Species | |
|
A. alboannuliforme | |
Asteristion is a genus of lichen-forming fungi in the family Graphidaceae.[1] It has seven species. Previously considered a synonym of either Phaeotrema or Thelotrema, molecular evidence led to its resurrection as a distinct genus. Asteristion lichens are corticolous (bark-dwelling), featuring a continuous thallus with a loose to hardened [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] and a [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] containing calcium oxalate crystals. The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], or fruiting bodies, are characterized by their large, often [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] appearance and the presence of distinct [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]. The secondary chemistry of these lichens includes major concentrations of stictic acid and minor to trace amounts of associated substances.
Taxonomy
Asteristion belongs to the tribe Wirthiotremateae in the family Graphidaceae. This tribe, revised in 2017 to account for newly clarified phylogenetic relationships, contains the genera Wirthiotrema, Austrotrema, Asteristion, and Nadvornikia. These genera are characterized by having the substance stictic acid, in addition to minor or trace amounts of related substances. Originally considered a synonym of either Phaeotrema or Thelotrema,[2] Asteristion was later recognized as a section of Thelotrema by Tatsuo Matsumoto in 2000.[3] Molecular evidence and extended phylogenetic analysis reported in the 2017 study have since revealed that the type species, Asteristion erumpens, does not belong to Thelotrema or any other recognized genus. Consequently, Asteristion has been resurrected as a distinct genus, which currently comprises seven species that were formerly members of the Chapsa platycarpa species complex.[2]
The genus name Asteristion derives from the star-like appearance of the recurved [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] commonly found in this genus, particularly evident in the type species.[2]
Description
Asteristion lichens are corticolous, featuring a continuous, epiperidermal thallus with a smooth to uneven surface and no prothallus. The thallus comprises a loose to prosoplectenchymatous cortex, a [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] with calcium oxalate crystals, and a thin epi- to endoperidermal medulla. The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] in Asteristion lichens is Trentepohlia, a green algal genus.[2]
The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] in these lichens are rounded to angular and immersed to [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]. The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], which ranges in colour from flesh to brown and is white-[[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], can be covered or exposed. The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] is distinct, fissured to recurved, and separated from the [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] by a narrow split, forming a prominent rim around the disc. The thalline margin is white to pale brown and entire to recurved.[2]
Asteristion lichens have an entire, hyaline to pale yellow, [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] excipulum, separated from the covering thalline layer by a split. A [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] is absent, and the [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] is [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] and hyaline. The hymenium is hyaline and clear, while the [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] is grey and granular. The paraphyses are unbranched with smooth apices, and [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] are present. The asci are fusiform, with fusiform to ellipsoid ascospores that are transversely septate to [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], somewhat [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] with lens-shaped [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], and hyaline to brown. Ascospores may be non-amyloid or amyloid. [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] have not been observed to occur in Asteristion lichens.[2]
The secondary chemistry of these lichens includes major concentrations of stictic acid and minor to trace amounts of related substances.[2]
Asteristion species can be distinguished from other genera in the Wirthiotremateae tribe by their large, often [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] ascomata and the presence of distinct periphysoids (lateral paraphyses). They may resemble Chapsa and its allies, such as Astrochapsa, but can be differentiated by the presence of a distinctly free excipulum forming a double margin, as opposed to a fused excipulum in Chapsa.[2]
Species
(As of April 2023), Species Fungorum (in the Catalogue of Life) accept seven species of Asteristion.[1]
- Asteristion alboannuliforme (Nagarkar, Sethy & Patw.) I.Medeiros, Lücking & Lumbsch (2017)
- Asteristion alboolivaceum (Vain.) I.Medeiros, Lücking & Lumbsch (2017)
- Asteristion australianum I.Medeiros, Lücking, Mangold & Lumbsch (2017)
- Asteristion cupulare (Müll.Arg.) I.Medeiros, Lücking & Lumbsch (2017)
- Asteristion leucophthalmum (Nyl.) I.Medeiros, Lücking & Lumbsch (2017)
- Asteristion platycarpoides (Tuck.) I.Medeiros, Lücking & Lumbsch (2017)
- Asteristion platycarpum (Tuck.) I.Medeiros, Lücking & Lumbsch (2017)
The taxon Asteristion erumpens Leight. (1870) is now named Phaeotrema erumpens.[4]
References
- ↑ 1.0 1.1 "Asteristion". Species 2000: Naturalis, Leiden, the Netherlands. https://www.catalogueoflife.org/data/taxon/34BT.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Medeiros, Ian D.; Kraichak, Ekaphan; Lücking, Robert; Mangold, Armin; Lumbsch, H. Thorsten (2017). "Assembling a taxonomic monograph of tribe Wirthiotremateae (lichenized Ascomycota: Ostropales: Graphidaceae)". Fieldiana Life and Earth Sciences 9: 1–31. doi:10.3158/2158-5520-16.9.1. https://www.biodiversitylibrary.org/bibliography/169194.
- ↑ Matsumoto, T. (2000). "Taxonomic studies of the Thelotremataceae (Graphidales, lichenized Ascomycota) in Japan: (1) Genus Thelotrema". Journal of the Hattori Botanical Laboratory 88: 1–50.
- ↑ "Record Details: Asteristion erumpens Leight., Trans. Linn. Soc. London 27(2): 163 (1870) [1871"]. Species Fungorum. https://www.speciesfungorum.org/Names/NamesRecord.asp?RecordID=377793.
Wikidata ☰ Q96648099 entry
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