''Asteristion'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

-forming

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the family

Graphidaceae The Graphidaceae are a family of lichen-forming fungi in the order Graphidales. The family contains nearly a hundred genera and more than 2000 species. Although the family has a cosmopolitan distribution, most Graphidaceae species occur in tropic ...

. It has seven species. Previously considered a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of either ''

Phaeotrema ''Phaeotrema'' is a genus of lichen-forming fungi in the family Graphidaceae. The genus was circumscribed in 1887 by Johannes Müller Argoviensis, with '' P. subfarinosum'' assigned as the type species. Species , Species Fungorum (in the C ...

'' or ''

Thelotrema ''Thelotrema'' is a genus of lichen-forming fungi in the family Graphidaceae, the family to which all taxa in the former Thelotremataceae now belong. Members of the genus ''Thelotrema'' are commonly called barnacle lichens. Description ''Thelo ...

'',

molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

evidence led to its resurrection as a distinct genus. ''Asteristion'' lichens are

corticolous This glossary of mycology is a list of definitions of terms and concepts relevant to mycology, the study of fungi. Terms in common with other fields, if repeated here, generally focus on their mycology-specific meaning. Related terms can be found ...

(bark-dwelling), featuring a continuous

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

with a loose to hardened and a containing

calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula or . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydr ...

crystals. The , or fruiting bodies, are characterized by their large, often appearance and the presence of distinct . The secondary chemistry of these lichens includes major concentrations of

stictic acid Stictic acid is an aromatic organic compound, a product of secondary metabolism in some species of lichens. Stictic acid is the subject of preliminary biomedical research. Stictic acid has cytotoxic and apoptotic effects ''in vitro ''In v ...

and minor to trace amounts of associated substances.

Taxonomy

''Asteristion'' belongs to the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Wirthiotremateae in the family

. This tribe, revised in 2017 to account for newly clarified

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

relationships, contains the genera ''

Wirthiotrema ''Wirthiotrema'' is a genus of lichen-forming fungi in the family Graphidaceae. The genus was circumscribed in 2010 by Eimy Rivas Plata, Klaus Kalb, Andreas Frisch, and H. Thorsten Lumbsch, with '' Wirthiotrema glaucopallens'' assigned as the t ...

'', ''

Austrotrema ''Austrotrema'' is a genus of lichen-forming fungi in the family Graphidaceae. It is primarily found in the Australian-Southeast Asian region. The genus is characterized by small, pore-like with a double margin, faintly amyloid ascospores, and ...

'', ''Asteristion'', and '' Nadvornikia''. These genera are characterized by having the substance

, in addition to minor or trace amounts of related substances. Originally considered a

of either ''

'' or ''

'', ''Asteristion'' was later recognized as a

section Section, Sectioning, or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sig ...

of ''Thelotrema'' by Tatsuo Matsumoto in 2000.

Molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

evidence and extended phylogenetic analysis reported in the 2017 study have since revealed that the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''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 In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

. The genus name ''Asteristion'' derives from the star-like appearance of the recurved commonly found in this genus, particularly evident in the type species.

Description

''Asteristion'' lichens are

, featuring a continuous, epiperidermal

with a smooth to uneven surface and no

prothallus A prothallus, or prothallium, (from Latin ''pro'' = forwards and Greek ''θαλλος'' (''thallos'') = twig) is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young ...

. The thallus comprises a loose to prosoplectenchymatous cortex, a with

crystals, and a thin epi- to endoperidermal medulla. The in ''Asteristion lichens'' is '' Trentepohlia'', a

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

l genus. The in these lichens are rounded to angular and immersed to . The , which ranges in colour from flesh to brown and is white-, can be covered or exposed. The is distinct, fissured to recurved, and separated from the by a narrow split, forming a prominent rim around the disc. The thalline margin is white to pale brown and entire to recurved. ''Asteristion'' lichens have an entire,

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

to pale yellow, excipulum, separated from the covering thalline layer by a split. A is absent, and the is and hyaline. The

hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in oth ...

is hyaline and clear, while the is grey and granular. The paraphyses are unbranched with smooth apices, and are present. The asci are

fusiform Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...

, with fusiform to

ellipsoid An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional Scaling (geometry), scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a Surface (mathemat ...

ascospores that are transversely

septate In biology, a septum (Latin for ''something that encloses''; septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatrial se ...

to , somewhat with lens-shaped , and hyaline to brown. Ascospores may be non-amyloid or amyloid. have not been observed to occur in ''Asteristion'' lichens. The secondary chemistry of these lichens includes major concentrations of

and minor to trace amounts of related substances.

Comparison with related genera

''Asteristion'' species can be distinguished from other genera in the Wirthiotremateae tribe by their large, often 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''.

Species

Species Fungorum ''Index Fungorum'' is an international project to index all formal names (Binomial nomenclature, scientific names) in the fungus Kingdom (biology), kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partn ...

(in the

Catalogue of Life The Catalogue of Life (CoL) is an online database that provides an index of known species of animals, plants, fungi, and microorganisms. It was created in 2001 as a partnership between the global Species 2000 and the American Integrated Taxono ...

) accept seven species of ''Asteristion''. * ''

Asteristion alboannuliforme ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym of either '' Phaeotrema'' or ''Thelotrema'', molecular evidence led to its resurrection as a distinct genus. ''A ...

'' * ''

Asteristion alboolivaceum ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym (taxonomy), synonym of either ''Phaeotrema'' or ''Thelotrema'', molecular phylogenetics, molecular evidence led ...

'' * ''

Asteristion australianum ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym of either '' Phaeotrema'' or ''Thelotrema'', molecular evidence led to its resurrection as a distinct genus. ''A ...

'' * ''

Asteristion cupulare ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym of either '' Phaeotrema'' or ''Thelotrema'', molecular evidence led to its resurrection as a distinct genus. ''A ...

'' * ''

Asteristion leucophthalmum ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym of either '' Phaeotrema'' or ''Thelotrema'', molecular evidence led to its resurrection as a distinct genus. ''A ...

'' * ''

Asteristion platycarpoides ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym of either '' Phaeotrema'' or ''Thelotrema'', molecular evidence led to its resurrection as a distinct genus. ''A ...

'' * ''

Asteristion platycarpum ''Asteristion'' is a genus of lichen-forming fungi in the family Graphidaceae. It has seven species. Previously considered a synonym of either '' Phaeotrema'' or ''Thelotrema'', molecular evidence led to its resurrection as a distinct genus. ''A ...

'' The taxon ''Asteristion erumpens'' is now named '' Phaeotrema erumpens''.

References

{{Taxonbar, from=Q96648099 Graphidaceae Graphidales genera Taxa described in 1870 Lichen genera Taxa named by William Allport Leighton