''Acanthotrema'' 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 ...

s 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 ...

. The genus was

circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...

by German lichenologist Andreas Frisch in 2006, with '' Acanthotrema brasilianum'' assigned as 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 ...

. ''Acanthotrema'' species are commonly found in

rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...

s ranging from

lowland Upland and lowland are conditional descriptions of a plain based on elevation above sea level. In studies of the ecology of freshwater rivers, habitats are classified as upland or lowland. Definitions Upland and lowland are portions of a ...

montane Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...

environments.

Description

''Acanthotrema'' has a grey-olive

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 dense, that can occasionally split. The are , taking on angular-rounded to () forms, with a visible and a margin that is lobulate and merged. ''Acanthotrema'' lacks a , and its has a , structure. -tipped are present, as are unbranched with spinulose tips. The of ''Acanthotrema'' range from

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 and come in shapes ranging from

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 ...

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 ...

, with thin septa and rectangular . They are non-

amyloid Amyloids are aggregates of proteins characterised by a fibrillar morphology of typically 7–13 nm in diameter, a β-sheet secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the human ...

. This lichen genus does not contain any secondary chemical compounds. Characteristics that differentiate ''Acanthotrema'' apart from other genera that possess similar fruiting structures are its chroodiscoid apothecia, spinulose periphysoids, and paraphyses. Ascospores in ''Acanthotrema'' have notably thin walls, a characteristic shared only with the genus ''

Chroodiscus ''Chroodiscus'' is a genus of leaf-dwelling lichens in the family Graphidaceae. These lichens form thin, smooth crusts directly on living leaves and are characterized by distinctive star-shaped fruiting bodies that split into triangular segme ...

''. However, ''Chroodiscus'' does not have periphysoids, possesses paraphyses with smooth apices, and is strictly

foliicolous Foliicolous refers to the growth habit of certain lichens, algae, fungi, liverworts, and other bryophytes that prefer to grow on the leaves of vascular plants. ''Foliicolous'' simply means 'growing upon leaves' whilst epiphyllous derives from the ...

(leaf dwelling). While certain '' Chapsa'' species, such as '' C. astroidea'', may bear a resemblance to ''Acanthotrema'' due to the similarity in apothecia and the near-thin-walled, non-amyloid ascospores, these taxa consistently have paraphyses with smooth apices.

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 ...

accepts six species of ''Acanthotrema'': *'' Acanthotrema alboisidiatum'' *'' Acanthotrema bicellulare'' *'' Acanthotrema brasilianum'' *'' Acanthotrema frischii'' *'' Acanthotrema kalbii'' *'' Acanthotrema minus'' – Brazil

References

{{Taxonbar, from=Q4672063 Graphidaceae Lichen genera Graphidales genera Taxa described in 2006 Taxa named by Andreas Frisch