Lichen genus Usnea (Parmeliaceae, Ascomycota) in Uttarakhand, India

Abstract

Usnea is a widespread fruticose lichen popularly known for its medicinal properties across the world. Though it has been mentioned in many floristic studies reported from Uttarakhand, India, no detailed taxonomic account has been conducted for the past two decades. The present study was based on specimens deposited in lichen herbarium of National Botanical Research Institute (LWG), personal herbarium of D.D. Awasthi (AWAS) and herbarium of the department of botany, Lucknow University (LWU). A total of 28 species, including seven new additions to Uttarakhand, namely U. dendritica Stirt., U. lucea Mot., U. norketti G. Awasthi, U. pseudosinensis Asahina, U. sinensis Mot., U. spinosula Stirt., U. subflorida Stirt.are presented along with key to species. Introduction The lichen genus Usnea Dill ex Adans belonging to family Parmeliaceae (Ascomycota) (Eriksson 2005), is a cosmopolitan fruticose lichen commonly found hanging from trees. Usnea can easily be recognised by its thread like morphology, central cartilaginous axis and presence of usnic acid (Clerc 1998, Ohmura 2001, 2012). The variation in morphological characters such as colour of the thallus, thickness of main branch and length of thallus, makes it difficult to distinguish one species of Usnea from another. According to Clerc (1998), morphological features of Usnea that are constant and that don't change with the changing environmental conditions of the geographical area should be used to distinguish species of Usnea. Such characters include pigmentation of basal part of the thallus, cortex and medulla; density of fibrils, shape of the branches, branching type and ratio of cortex, medulla and axis (C/M/A) in longitudinal section. Lichen genus Usnea is represented by occurrence ca. 300 species in the world (Ohmura 2012) and India represents 60 species (Singh & Sinha 2010). Motyka (1938) published the first world monograph of genus Usnea and divided Usnea into six subgenera viz., Protousnea Motyka, Neuropogon (Nees & Flot.)Motyka, Lethariella Motyka, Chlorea (Nyl.) Motyka, Eumitria (Stirt.) Motyka and Euusnea Jatta. All these subgenera later became independent genera except Eumitria (Stirt.) Motyka and Euusnea Jatta, which were in combination considered as the genus Usnea