Hypotrachyna neosingularis


Hypotrachyna neosingularis is a species of corticolous foliose lichen in the family Parmeliaceae. Described as a new species in 2001, it is found in India, where it is endemic to the Eastern Himalaya.

Taxonomy

Hypotrachyna neosingularis was formally described as a new species by the lichenologists Pradeep Divakar, Dalip Kumar Upreti, and John Elix as part of a survey of collections of the family Parmeliaceae from India. The type specimen was collected in Gangtok, Sikkim, at an unspecified elevation, growing on bark. It was collected by K.P. Srivastava in July 1959, and is housed in the lichen herbarium at LWG. The species name neosingularis refers to its close relationship with Hypotrachyna singularis, a South American species described by Mason Hale in 1975. The Indian species is distinguished from H. singularis primarily by the shape of its, its smaller spores, and differences in the chemistry of its medulla.

Description

Hypotrachyna neosingularis has foliose thallus that grows up to 8 cm wide. The thallus is loosely adnate to adnate and has a texture. Its lobes are, sublinear to irregular in shape, and measure 3–5 mm in width. The margins are eciliate and . These are rounded, can be found both along margins and on the surface, and are dense in the centre of the thallus, measuring 0.2–1.0 mm wide.
The upper surface is grey, becoming grey-brown with age, and can be flat or buckled. It is smooth, shiny, and but may develop irregular cracks over time. The species lacks isidia, soredia, and, suggesting it reproduces primarily through spores. The medulla is white. The lower surface is black to the margin with moderately dense, dichotomously branched black rhizines, which measure 1.0–2.5 mm wide.
Apothecia are common and, measuring 1.0–2.5 mm wide. They are shallowly concave, pale brown to black, with the smooth and margin at first, later becoming . The are ellipsoid and measure 8–9 by 4.5–5.5 μm. Pycnidia are black and immersed in the thallus. The conidia are weakly and measure 6–8 by 1 μm.

Chemistry

The chemistry of H. neosingularis is characterised by distinctive chemical spot tests reactions and specific secondary metabolites. The cortex is K+, while the medulla shows K−, C−, KC−, P− reactions. The lichen contains several secondary metabolites: atranorin, chloroatranorin, lichesterinic acid, and protolichesterinic acid, along with an unknown fatty acid. This chemical profile differs significantly from the related species Hypotrachyna singularis, which contains dehydroprotoconstipitatic acid, praesorediosic acid, protoconstipatic acid, constipatic acid, praesorediosic acid, lichesterinic acid, protolichesterinic acid, and an unknown fatty acid. The presence of lichesterinic acid as a major component in H. neosingularis, compared to the complex mixture of fatty acids in H. singularis, serves as an important chemical marker for distinguishing between these morphologically similar species.

Habitat and distribution

At the time of its description in 2001, Hypotrachyna neosingularis was known only from its type locality in Sikkim, India. The discovery of the species was part of a broader effort to document the lichen funga of the Indian subcontinent, which had been investigated intensively over the preceding 40 years by researchers such as Awasthi. H. neosingularis was reported from Mizoram in 2020. The species is considered endemic to the Eastern Himalaya.