''Pliariona'' is a fungal

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 ...

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 comprises the single species ''Pliariona montagnei'', a

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) script lichen widely distributed across various

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

regions.

Taxonomy

''Pliariona'' was originally

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 the Italian lichenologist Abramo Bartolommeo Massalongo in 1860, to contain a script lichen species that was originally named ''Graphis montagnei'' by the Dutch botanist Roelof Benjamin van den Bosch. The genus ''Pliariona'' was reinstated in 2013 based on

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies that revealed distinct lineages within the

. These studies showed that species previously grouped under the same genus due to morphological similarities were not always closely related. For example, ''Pliariona montagnei'' (formerly known as ''Thecaria montagnei'') and '' Thecaria quassicola'', despite their superficial resemblance, were found to be genetically distant and not

congeneric Congener may refer to: * Congener (biology), organisms within the same genus * Congener (chemistry), related chemicals, e.g., elements in the same group of the periodic table * Congener (beverages), a substance other than ethanol produced during t ...

. The reinstatement of ''Pliariona'' as a separate genus is supported by molecular evidence and key taxonomic characteristics that distinguish it from related genera. These distinguishing features include an apothecial (the spore-producing surface lacking a powdery coating) and a dark red

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 ...

(the fertile layer of the fungus).

Description

''Pliariona montagnei'' has a thallus that ranges in colour from olive to dull green, with a glossy appearance. The surface texture varies from smooth to warty, often reflecting the contours of the underlying bark . The species is characterised by its numerous

ascomata An ascocarp, or ascoma (: ascomata), is the fruiting body (sporocarp (fungi), sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded ascus, asci, each of which typically contains four to ...

(fruiting bodies), which are and in form. These reproductive structures are predominantly , though some display occasional branching, and measure up to 0.6 mm by 0.5 mm. The ascomata feature an open that is red and epruinose, surrounded by a well-developed . This exciple is fully (blackened), measuring 130 to 250

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

, and is covered by a thick, unbroken . The

, which measures 150–200 μm in height, is red-pigmented and densely . Within this layer, the asci (spore-bearing sacs) each contain a single

ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...

. These ascospores are ,

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 ...

al to oval in shape, and measure 125–155 μm by 25–40 μm. Initially

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 ...

and 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 ...

, the spores develop a brownish or

mottled Mottle is a pattern of irregular marks, spots, streaks, blotches or patches of different shades or colours. It is commonly used to describe the surface of plants or the skin of animals. In plants, mottling usually consists of yellowish spots on p ...

appearance as they mature. The species contains the compound isohypocrelline, though the biological significance of this substance in ''P. montagnei'' remains unclear. The combination of these morphological and chemical characteristics distinguishes ''P. montagnei'' from other superficially similar species within the Graphidaceae.

Habitat and distribution

''Pliariona montagnei'' exhibits a wide distribution across various tropical and subtropical regions. The species has been documented in Australia, West Africa, Japan, the Philippines, India, Indonesia, the Solomon Islands,

Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (; ), is an island country in Melanesia located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of northern Australia, northeast of New Caledonia, east o ...

, and

Norfolk Island Norfolk Island ( , ; ) is an States and territories of Australia, external territory of Australia located in the Pacific Ocean between New Zealand and New Caledonia, directly east of Australia's Evans Head, New South Wales, Evans Head and a ...

. It has more recently been recorded in Vietnam, specifically in Đắk Lắk province, within Chư Yang Sin National Park. The species is

, growing on tree bark. In the Vietnamese location where it was observed, ''P. montagnei'' was found at an elevation of about 780 metres above sea level.

References

{{Taxonbar, from1=Q107289447 , from2=Q108263326 , from3=Q59587260 , from4=Q107901571 , from5=Q107708171 , from6=Q105498147 , from7=Q10695946 Graphidales Graphidales genera Lichen genera Taxa described in 1860 Taxa named by Abramo Bartolommeo Massalongo