''Diorygma sticticum'' is a species of corticolous (bark-dwelling)

script lichen A script lichen, or graphid lichen, is a member of a group of lichens which have spore producing structures that look like writing on the lichen body. The structures are elongated and narrow apothecia called lirellae, which look like short scribbles ...

in the family

Graphidaceae The Graphidaceae are a family of lichens in the order Ostropales. Distribution and ecology The vast majority of Graphidaceae species are restricted to the tropics. Most Graphidaceae species are epiphytic (i.e. they grow only on plants). Gener ...

. It was described as new to science in 2011. It is found in lowland rainforests in

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is bo ...

, and in southwestern India.

Taxonomy

''Diorygma sticticum'' was first described as a new species by lichenologists Jutarat Sutjaritturakan,

Klaus Kalb Klaus Kalb (born 1942) is a German lichenologist and an authority on tropical lichens. Biography Klaus Kalb was born in Nuremberg in 1942 and grew up in southern Bavaria. From 1960 to 1965 he studied biology, chemistry, and geography at t ...

, and

Robert Lücking Robert Lücking (born 1964) is a German lichenologist. He is a leading expert on foliicolous lichens–lichens that live on leaves. Life and career Born in Ulm in 1964, Lücking earned both his master's (1990) and PhD degree (1994) at the Univer ...

in 2011. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was found in

Khao Yai National Park Khao Yai National Park ( th, อุทยานแห่งชาติเขาใหญ่, , ) is a national park in Thailand. Established in 1962 as Thailand's first national park, it is the third largest national park in Thailand. Descri ...

in Nakhon Ratchasima province, Thailand. The species epithet, ''sticticum'', refers to its unique secondary chemistry.

Description

''Diorygma sticticum'' has a corticolous

thallus Thallus (plural: 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. Many of these organisms wer ...

that can grow up to in diameter and is 70–150

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

thick. When viewed in cross-section, the thallus reveals an upper cortex measuring 10–15 μm thick, an uneven , and groups of

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

crystals. It has a smooth to uneven, light green surface, occasionally accompanied by a white

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 species forms dense clusters of stellate , which range from 1–3 mm in length, 0.15–0.3 mm in width, and 0.1 mm in height. These lirellae have a distinct white and a concealed to partly exposed, pale brown that is thickly white-. The colourless are 10–13 by 6–8 μm in size, with a strong I+ violet-blue reaction when

stained A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make materials app ...

with

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

. The presence of stictic, hypostictic, and cryptostictic acids is a notable feature of ''Diorygma sticticum''. These lichen products contribute to the species' distinctive characteristics and differentiate it from other lichens within its genus. ''Diorygma sticticum'' is closely related to '' Diorygma microsporum'', but it can be distinguished by its secondary chemistry and geographical distribution.

Habitat and distribution

This lichen species has been found in several lowland rainforest locations in Thailand, including Khao Yai National Park in Nakhon Ratchasima province, Saraburi province, and Phu Luang Wildlife Sanctuary in Loei province. In 2020 it was reported from the

Cotigao Wildlife Sanctuary The Cotigao Wildlife Sanctuary is located in Canacona Taluka, South Goa district, of Goa, India, established in 1968. There is an eco-tourism complex at the entrance of the sanctuary that houses a nature interpretation centre, cottages, toilet ...

Goa Goa () is a state on the southwestern coast of India within the Konkan region, geographically separated from the Deccan highlands by the Western Ghats. It is located between the Indian states of Maharashtra to the north and Karnataka to the ...

, India.

References

{{Taxonbar, from=Q16981375 sticticum Lichen species Lichens described in 2011 Lichens of Indo-China Lichens of India Taxa named by Klaus Kalb Taxa named by Robert Lücking