Myelochroa upretii


Myelochroa upretii is a species of corticolous, foliose lichen in the family Parmeliaceae. It occurs in northern India.

Taxonomy

It was described as a new species in 2001 by the lichenologists Pradeep Divakar and John Elix. The type specimen was collected by Dalip Kumar Upreti on 21 November 1989, and is housed in the lichen herbarium at LWG. The species epithet upretii honours the collector Upreti, a lichenologist known for his contributions to Asian lichenology.

Description

Myelochroa upretii has foliose thallus that grows up to 11 cm wide. Its are, sublinear to subrotund, 2–10 mm wide, and marginally .
The lobe margins erode into somewhat soralia. The upper surface is pale mineral-grey, becoming yellow-brown when preserved in herbaria. It is flat, shiny,, and becomes with age. The upper surface lacks isidia.
The soralia originate marginally or submarginally and spread in a laminar pattern. The soredia are, and the marginal lobes are weakly rolled backwards.
The medulla is mostly white, with pale yellow in some places. The lower surface is black with a narrow brown marginal zone. The rhizines are dense, black, simple or rarely dichotomously branched, and 0.5–1.5 mm long. No apothecia or pycnidia have been observed in this species.

Chemistry

The chemistry of M. upretii is characterised by distinctive colour reactions and a specific set of secondary metabolites. The cortex is K+, while the medulla is K+, C−, P+. Chemically, the lichen contains several major lichen products including galbinic acid, salazinic acid, zeorin, and secalonic acid A as its primary medullary pigment. This last compound is particularly significant as a taxonomic marker, as it distinguishes M. upretii from closely related species like M. metarevoluta, which instead contain secalonic acid R, secalonic acid W, or pigmentosin B as their major medullary pigments. The presence of substantial quantities of galbinic acid and 16β-acetoxyhopane-6α,22-diol is also taxonomically important, differentiating this species from the chemically similar M. salazinica.

Habitat and distribution

At the time of its original publication, Myelochroa upretii was known only from its type locality in northern India, specifically in the Pithoragarh district of Uttar Pradesh, at an elevation of 1900 metres. It was collected growing on Rhododendron in an oak forest. In a later study of lichen biodiversity occurring on the tree Quercus leucotrichophora in Uttarakhand forests, M. upretii was only found at elevations above. It has also been recorded from Pithoragarh.
In contrast to M. upretii, the closely related species M. metarevoluta has a wider distribution across the eastern United States, Japan, China, and India, while M. macrogalbinica has been recorded from several locations in Uttar Pradesh and the western Himalayas in India.