What do epiphytic lichens of Guwahati city indicate?

Abstract

Lichens are composite organisms consisting of a symbiotic association of a fungus with a photosynthetic partner, either a green alga or a Cyanobacteria, grow in diverse climatic conditions and on equally diverse substrata and are widely distributed in almost all the phytogeographical regions of the world. An ‘annotated checklist’ published by the Botanical Survey of India (BSI) documents 2303 species belonging to 305 genera and 74 families in India1. Lichens are a major section of species that are sensitive to changes in atmospheric nutrient conditions2 and have been used as bioindicators of pollution over a long period of time, especially sulphur dioxide (SO2)3. Fruticose lichens are known to be the most sensitive to air pollution, followed by foliose and crustose forms. The vanishing of sensitive lichen species due to changes in microclimatic conditions and air pollution has been reported from Indian cities of Bangalore4 and Kolkata5. Due to the fast rate of disappearance of flora for a range of reasons like habitat loss, air pollution, changes in the microclimatic conditions and uncontrolled harvest, lichen biologists have initiated a discourse to creating ‘protected areas’ for conservation of lichens6. Systematic studies on lichens in India, however, are still sporadic. More so, there are instances of limited studies in the northeastern region of India, which is also a biological hotspot.