3 Lichens, vital components of the ecosystem, are distinct mutualistic groups of autotrophic organisms (Baniya & Bhatta, 2021). They are widely distributed and highly diversified. They occur in a wide range of habitats throughout the world and are considered pioneer colonizers of the terrestrial ecosystem (Negi and Upreti, 2009). Some species of lichens are found in both the freshwater stream and marine intertidal zones (Hawksworth, 2000). Based on where they occur, lichens can be categorized into corticolous (on the tree bark), follicolous (on the leaf), saxicolous (on the rock) and terricolous (on the soil) lichens. The thallus of lichens shows morphological variation and exists in different growth forms such as crustose, leprose, squamulose, foliose and fruticose (Upreti et al., 2015). Lichens have the ability to obtain water and nutrient directly from their surrounding air. As a consequence, they are more sensitive to changing environmental conditions (Gausalaa, 2014). Hence, alteration in lichens diversity is assumed to indicate the changes in environmental conditions (Shukla et al., 2014). Furthermore, the changes in topographical variables and environmental factors are reported to affect the Banko Janakari, Vol 32 No. 2, 2022 Pp 3‒18https://doi.org/10.3126/banko.v32i2.50892 Distribution pattern of corticolous lichens in different areas of Kathmandu valley, Nepal This study attempts to document the lichen species and their distribution in different areas of Kathmandu valley, Nepal. Twenty sampling sites with different degrees of air pollution categorized as disturbed (industrial, heavy traffic and residential areas) and undisturbed areas (clean area) were selected for the study. Sampling was done using the quadrat method. To enumerate the total number of lichen species found in Kathmandu valley, lichen specimens were collected from inside as well as outside the quadrats. A total of 97 species of corticolous lichens belonging to 21 families and 44 genera were recorded from the study sites. Parmeliaceae was the largest family followed by Graphidaceae. The importance value analysis showed that Candelaria concolor (115.2), Dirinaria aegialita, Lepraria sp., Phaeophyscia hispidula var. hispidula and Physcia sorediosa (106.02) are the most common and dominant lichen species in Kathmandu valley. Among the most common and dominant lichen species, Candelaria concolor, Dirinaria aegialita, Phaeophyscia hispidula var. hispidula and Physcia sorediosa were found concentrated in heavy traffic areas whereas Lepraria sp. in the industrial areas. A higher number of lichen species (70%) was recorded in undisturbed areas than in disturbed areas (50%). These study confirm that the distribution of lichen flora is strongly influenced by degrees of pollution. This in turn suggests that lichens can be used as bio indicators of air quality in the Kathmandu valley. Keywords Coverage, flora, importance value, pollution, quadrat N. Karmacharya 1*, D. K. Upreti 2, and M. K. Chettri 3 Received: 5, May 2022 Revised: 24, November 2022 Accepted: 14, December 2022 Published: 31, December 2022 1 Botany Department, Padma Kanya Multiple Campus, Tribhuvan University, Kathmandu, Nepal, * Email:karmacharya129@gmail.com 2 Lichenology Laboratory, CSIR-National Botanical Research Institute, Lucknow (UP), India 3 Botany Department, Amrit Campus, Tribhuvan University, Lainchaur, Kathmandu, Nepal Banko Janakari, Vol 32 No. 2 4 Karmacharya et al. distribution, diversity and abundance of the lichens (Hauck, 2011). Therefore, lichens are globally recognized and utilized as bioindicators of a variety of environmental conditions (Garty, 2001; Gupta et al., 2014; De Silva & Senanayake, 2015). Besides, lichens are of high economic value and are used as food, medicines, natural remedies, perfumes, dyes, etc. (Upreti et al., 2015; Devkota et al., 2017; Crawford, 2019; Yang et al., 2021). Furthermore, lichens are chemically rich and produce more than 1000 different types of secondary metabolites. Among them, more than 90% are unique to themselves and show a variety of biological activities (Elix & Stocker- Wӧrgӧtter, 2008). Globally, about 20,000 species of lichens are known so far, of which India harbors 2,963 species (Islary et al., 2022). The lichens of different parts of Nepal had been studied by various native and foreign lichenologists for several years and 1,129 taxa have been recorded so far (Baniya et al., 2022). Sharma (1995) estimated 2,000 lichen species in Nepal. The copious presence of lichens in the country is due to the diverse topographic condition together with varied climatic conditions (Jha et al. 2017). Although several lichenological explorations have been undertaken in the central, western and eastern regions of Nepal (Sharma, 1995; Baniya et al., 2001; Olley & Sharma, 2013; Rai et al., 2016; Chongbang et al., 2018), only a few have undertaken a thorough collection of lichens from the Kathmandu valley (Baniya & Bhatta, 2021). Hence, the present study aims to enumerate the corticolous lichens in Kathmandu valley and analyze their distribution pattern in areas with different degrees of pollution i.e., disturbed (industrial, heavy traffic, residential) and undisturbed (clean) areas within Kathmandu valley. Materials and methods Study areas The study areas were located in the Kathmandu valley (27042’ N and 85020’ E) of Bagmati Province, central Nepal. Twenty sampling sites under four study areas with different degrees of air pollution categorized as disturbed (industrial, heavy traffic and residential areas) and undisturbed areas (clean areas) were selected for the study (Figure 1). Sampling was done during dry season i.e., October 2016 ‒ January 2017. As we were interested in corticolous (bark- inhabiting) lichens, sampling sites were chosen based on the availability of lichens on the bark of the host trees. Collection of lichen specimens Specimens of lichens were collected from all the sampling sites. At each site, five old and big trees (having more than 80-120 cm trunk diameter) were selected within the area of 100 x 100 m based on the availability of lichens on the tree barks. Sampling was carried out by placing a quadrat of 20 x 20 cm (having 4 sub-quadrats of 10 x 10 cm) on four sides of the tree trunk at a height of 1.5 m (breast height) above the ground level, without overlapping (Asta et al., 2002; Pinokiyo et al., 2008; Conti, 2008). The standard size of the quadrat was determined by the species-area curve method (Asta et al., 2002). Altogether 400 quadrats were laid on 100 trees in 20 sampling sites (i.e., 20 quadrats in each sampling site). The coverage and frequency of each lichen species within each quadrat were recorded. All the available lichen specimens were collected from each quadrat. To enumerate the lichen species found in Kathmandu valley, specimens present outside of the quadrats were also collected. For this, specimens present on any trees with an area of 100 x 100 m at each sampling site (up to ca. 2200 m altitudes in clean areas) were collected. Altogether 230 lichen specimens, including 136 specimens inside the quadrats, were collected from 20 sampling sites under four study areas (industrial, heavy traffic, residential and clean areas) of Kathmandu Valley. Forest conservation rules and strategies were followed while collecting the specimens and a very small quantity of lichen specimens was collected for identification. The collected specimens together with their primary identification information like color, substrate type, quadrat number, collection number, and name of the sampling site were placed in individual paper bags and curated according to the standard protocol of Awasthi (2000). Banko Janakari, Vol 32 No. 2 5 Karmacharya et al. Figure 1: Map of the study area showing the location of 20 sampling sites Banko Janakari, Vol 32 No. 2 6 Karmacharya et al. Lichen identification Identification of lichen specimens was carried out at the lichenology laboratory of the Council of Scientific & Industrial Research-National Botanical Research Institute, Lucknow, India. The lichen specimens were identified on the basis of their morphology, anatomy and chemistry. The morphological and anatomical details of the specimens were studied using standard light microscopy techniques under Stereomicroscope LEICATM S8APO and optical microscope LEICATM DM500 respectively. The chemistry of the lichens was studied by spot color test, UV- light and thin layer chromatography (TLC) with solvent system A using protocol of Elix and Ernst- Russel (1993) and Orange et al. (2001). Authentication and documentation of identified lichen species Identification, changes of nomenclature and novelties of the species were authenticated using monographs, relevant keys, literature and checklists (Awasthi, 1991, 2007; Wolseley & Aptroot, 2009; Jagadeesh Ram & Sinha, 2009, 2011; Singh & Sinha, 2010; Mishra et al., 2011; Aptroot, 2012; Olley & Sharma, 2013; Ingle et al., 2017; Kantvilas et al., 2018). Nomenclature changes with current name of each species was also checked using the website address (http:// www.indexfungorum.org/Names/Names.asp). After identification, the herbarium of each species was prepared following the protocol of Nayaka (2014) and labeled with the name and family of species, detail of locality, date of collection, name of collector and collection number. All the prepared herbaria were deposited at the National Herbarium and Plant Laboratories, Godawari, Kathmandu, Nepal. Calculation of importance value Assemblage of lichens was quantitatively analyzed by determining their importance values. The importance values (IV) of lichen species were calculated according to Printos et al. (1993, 1995), which were the sum total of relative coverage (RC) and relative frequency (RF). IV = RC + RF The RC and the RF were calculated by using the following formulae. RC = (coverage of individual species/sum of coverage of all species) x 100 RF = (frequency of individual species/sum of frequency of all species) x 100 Results Lichen species found in Kathmandu valley A total of 97 species of epiphytic lichens (including 61 species inside the quadrats) belonging to 21 families and 44genera were identified (Table 1). Among the families reported, Parmeliaceae was the largest family with 8 genera and 20 species followed by Graphidaceae with 7 genera and 20 species. Physciaceae, a very common family reported from all the study areas including areas with high anthropogenic activities, was the third largest family with 5 genera and 16 species. The photobiont study showed that the lichen species with green algae (Trebouxia and Trentepohlia) as photobiont dominated the study areas. The cyanophycean lichens with blue-green algae (photobiont – Nostoc) exhibited their poor distribution as represented by only one family Collemataceae with two species and reported from shady and moist places of the Balaju industrial site, Ranibari site and Suryabinayak site. Banko Janakari, Vol 32 No. 2 7 Karmacharya et al. Table 1: Lichen species found in Kathmandu valley showing their family name, name of lichen species, their accession number and growth form SN Name of family Name of lichen species Accession number Growth form 1 Parmeliaceae Bulbothrix isidiza (Nyl.) Hale 17-174B Foliose Bulbothrix meizospora ((Nyl.) Hale 17-176 Foliose Bulbothrix setschwanensis (Zahlbr.) Hale 16-126 Foliose Canoparmelia pustulescens (Kurok.) Elix. 16-096A Foliose Canoparmelia texana (Tuck.) Elix & Hale 16-116 Foliose Hypotrachyna cirrhata (Fr.) Divakar, A. Crespo, Sipman, Elix & Lumbsch 17-145 Foliose Hypotrachyna majoris (Vain.) Hale 17-181 Foliose Hypotrachyna physcioides (Nyl.) Hale 17-177 Foliose Myelochroa subaurulenta (Nyl.) Elix & Hale 17-172 Foliose Myelochroa xantholepis (Mont. & Bosch) Elix & Hale 16-096B Foliose Parmelinella wallichiana (Taylor) Elix & Hale 17-168 Foliose Parmotrema austrosinense (Zahlbr.) Hale 16-028 Foliose Parmotrema praesorediosum (Nyl.) Hale 16-026A Foliose Parmotrema pseudonilgherrense (Asahina) Hale 17-175 Foliose Parmotrema reticulatum (Taylor) Choisy 16-094 Foliose Parmotrema tinctorum (Nyl) Hale 16-069 Foliose Remototrachyna awasthii (Hale & Patwardhan) Divakar & A. Crespo 16-061 Foliose Remototrachyna flexilis (Kurok.) Divakar & A. Crespo 16-100 Foliose Usnea eumitrioides Motyka 17-146 Fruticose Usnea orientalis Motyka 17-205A Fruticose 2 Graphidaceae Allographa cleistoblephara (Nyl.) Lücking & Kalb 16-016 Crustose Allographa leprographa (Nyl.) Lücking & Kalb 16-133A/c Crustose Diorygma hieroglyphicum (Pers.) Staiger & Kalb 16-148 Crustose Diorygma junghuhnii (Mont. & Bosch.) Kalb, Staiger & Elix 16-089 Crustose Graphina anguina (Mont.) Müll. Arg 16-093A/b Crustose Graphis antillarum Vain 17-207C Crustose Graphis breussii G. Neuwirth & Lücking 16-093C Crustose Graphis cincta (Pers.) Aptroot 16-046 Crustose Graphis galactoderma (Zahlbr.) Lücking 17-158B Crustose Graphis lineola Ach. 16-109B Crustose Graphis paradisserpens Sipman and Lücking 16-093A/a Crustose Graphis paraserpens Lizano and Lücking 16-182 Crustose Graphis perticosa (Kremp) A. W. Archer 16-163A Crustose Graphis pinicola Zahlbr. 17-200A Crustose Graphis proserpens Vain 17-149 Crustose Graphis stenotera Vain. 16-093B Crustose Pallidogramme chrysenteron (Mont.) Staiger, Kalb & Lücking 17-163B Crustose Pallidogramme divaricoides (Räs.) Pushpi Singh & Kr.P. Singh 16-089B Crustose Phaeographis leiogrammodes (Kremp.) Mull. Arg. 17-196A Crustose Thalloloma subvelata (Stirt.) D.J. Galloway 17-196B Crustose Banko Janakari, Vol 32 No. 2 8 Karmacharya et al. SN Name of family Name of lichen species Accession number Growth form 3 Physciaeae Heterodermia diademata (Taylor) D.D.Awasthi 16-132 Foliose Heterodermia firmula (Linds.) Trevis. 16-088A Foliose Heterodermia incana (Stirt.) D.D.Awasthi 17-221 Foliose Heterodermia speciosa (Wulfen) Trevis. 17-142 Foliose Hyperphyscia adglutinata Var. pyrithrocardia (Mull. Arg.) D.D. Awasthi 16-120 Foliose Hyperphyscia minor (Fée) D.D. Awasthi 16-059 Foliose Hyperphyscia isidiata Moberg 16-108D Foliose Phaeophyscia hispidula var. hispidula (Ach.) Essl. 16-003A Foliose Phaeophyscia pyrrhophora (Poelt) D.D. Awasthi & M. Joshi 16-127A Foliose Physcia abuensis D.D. Awasthi & S.R. Singh 16-068 Foliose Physcia aipolia (Ehrh. ex Humb.) Fürnr 16-029 Foliose Physcia crispa (Nyl) 16-014 Foliose Physcia dubia (Hoffm.) Lettau 16-064A Foliose Physcia integrata (Nyl.) Arnold 16-98 Foliose Physcia sorediosa (Vain.) Lynge 16-010B Foliose Polyblastidium japonicum (M. Satô) Kalb 17-195 Foliose 4 Arthoniaceae Arthothelium subruanum Makhija & Patw 17-160 Crustose Herpothallon flavominutum Jagad. Ram, G.P. Sinha & Elix 16-091 Crustose Herpothallon granulosum Jagad. & G.P. Sinha 17-197 Crustose Herpothallon himalayanum Jagad. & G.P. Sinha 16-089C Crustose Herpothallon isidiatum Jagad. and G. P. Sinha Crustose Herpothallon philippinum (Vain.) Aptroot & Lücking 16-042 Crustose Herpothallon sticticum Jagad. & G.P. Sinha 17-186 Crustose Stirtonia psoromica Aptroot & Wolseley 17-207A Crustose 5 Ramalinaceae Bacidia incongruens (Stirt.) Zahlbr. 16-090A Crustose Bacidia rubella (Hoffm.) A. Massal 17-190 Crustose Phyllopsora corallina (Eschw.) Müll. Arg. 16-066B Squamulose Phyllopsora furfuracea (Pers.) Zahlbr. 17-153 Squamulose Ramalina conduplicans Vain. 17-144 Fruticose 6 Caliciaceae Dirinaria aegialita (Afzel. ex Ach.) B.J. Moore 16-010B/b Foliose Dirinaria consimilis (Stirt.) D.D. Awasthi 16-123A/b Foliose Pyxine reticulata (Vain.) Vain. 16-035 Foliose Pyxine subcinerea Stirt. 16-123B Foliose 7 Pertusariaceae Lepra leucosorodes (Nyl.) I. Schmitt, B.G. Hodk. & Lumbsch 16-147 Crustose Pertusaria melastomella Nyl 17-164 Crustose 8 Lecanoraceae Lecanora achroa Nyl. 16-095 Crustose Lecanora chlarotera Nyl. 17-182E Crustose Lecanora interjecta Mull. Arg. 17-166A Crustose Lecanora leprosa Fée Essai 17-182B Crustose 9 Cladoniaceae Cladonia cervicornis (Ach.) Flot. 17-151A Fruticose Cladonia corniculata Ahti & Kashiw. 17-151B Fruticose Cladonia subradiata (Vain.) Sandst. 17-154 Fruticose 10 Candelariaceae Candelaria concolor (Dicks.) Arnold 16-001 Foliose Candelaria indica (Hue) Vain. 16-124A Foliose Banko Janakari, Vol 32 No. 2 9 Karmacharya et al. SN Name of family Name of lichen species Accession number Growth form 11 Collemataceae Leptogium burnetiae Dodge 17-171 Foliose Leptogium wilsonii Zahlbr. 16-015 Foliose 12 Pyrenulaceae Pyrenula astroidea (Fée) R.C. Harris 16-186 Crustose Pyrenula submastophora Ajay Singh & Upreti 16-92 Crustose 13 Byssolomataceae Byssoloma subdiscordans (Nyl.) P. James 16-90 Crustose 14 Leprocaulaceae Leprocaulon coriense (Hue) Lendemer & B.P. Hodk. 16-087B Crustose 15 Teloschistaceae Opeltia flavorubescens (Huds.) S.Y. Kondr. & Hur 16-046B/b Crustose 16 Chrysothrichaceae Chrysothrix candelaris (L.) J.R. Laundon 16-020 Leprose 17 Coccocarpiaceae Coccocarpia erythroxyli (Spreng.) Swinscow & Krog 17-178 Foliose 18 Coenogoniaceae Coenogonium lutescens (Vezta & Malcolm) Malcom 17-154 Crustose 19 Malmideaceae Malmidea granifera (Ach.) Kalb, Rivas Plata & Lumbsch 17-171A Crustose 20 Stereocaulaceae Lepraria sp. 16-018 Leprose 21 Trypetheliaceae Polymeridium submuriforme Aptroot 16-072 Crustose Among the 44 genera reported, Graphis was the largest genus with 11 species followed by Herpothallon and Physcia with six species each, and Parmotrema with five species (Table 1). The study of growth forms revealed that Kathmandu valley has almost an equal number of crustose (44 species) and foliose (43 species) lichens (Table 1). The crustose lichens (45%) dominated the areas followed by foliose lichens (44%) (Figure 2). The foliose and crustose lichens showed their diversity in all the disturbed and undisturbed areas including high elevation in clean areas. Whereas, the fruticose form of lichens was reported only from the high elevation in clean areas. Figure 2: Lichen species found in Kathmandu valley by their growth forms Importance value (IV) of lichen species The study revealed that there is considerable variation in lichen species composition and abundance among 20 sampling sites across four study areas of Kathmandu Valley (Table 2). Among the 61 species identified inside the quadrats, 43 (70%) species were reported from clean (undisturbed) areas while 31 (50%) species were reported from disturbed areas (industrial, heavy traffic and residential areas). The most common and dominant species of the Valley were Candelaria concolor (IV ranges from 3.5 to 115.2), Dirinaria aegialita (IV ranges from 14.2 to 45.9), Lepraria sp. (IV ranges from 5.9 to 74.1), Phaeophyscia hispidula var. hispidula (IV ranges from 7.3 to 67.7) and Physcia sorediosa (IV ranges from 9.4 to 106.02) (Table 2). These species were reported from all the study areas and have a high importance value in most of the sampling sites of disturbed areas (industrial, heavy traffic and residential areas) than in undisturbed (clean) areas. Among the all species recorded in quadrates, Candelaria concolor was found with the highest importance value (115.2) at heavy traffic areas followed by Physcia sorediosa (106.02) in the same area and both species were reported from 95% of sampling sites, with exception of the Phulchoki sampling site, a clean area. Contrary to this, the species like Banko Janakari, Vol 32 No. 2 10 Karmacharya et al. Bacidia incongruens and Remototrachyna flexilis have the lowest importance value (1.0) followed by Hypotrachyna cirrhata (2.3) and Leptogium burnetiae (2.4) in clean areas. Among the species of all twenty sampling sites, 52.5% of the species were confined to only one sampling site. The rest of the species were relatively restricted in particular sites. Table 2: Impotance Value of lichen species (n = 20) for each sampling site in the study areas. (* name of sampling site: figure 1) Name of lichen species Industrial areas Heavy traffic areas Residential areas Clean areas 1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Allographa cleistoblephara 2.7 Allographa leprographa 32.5 Bacidia incongruens 1.0 Bulbothrix isidiza 9.2 21.1 Bulbothrix setschwanensis 9.6 10.1 Byssoloma subdiscordans 14.3 Candelaria concolor 90.3 11.5 7.3 15.2 55.3 64.4 16.0 115.2 22.9 100.5 5.5 22.1 23.3 24.6 10.1 22.2 17.7 5.4 3.5 Candelaria indica 13.7 Canoparmelia pustulescens 6.5 24.5 24.8 Canoparmelia texana 20.1 16.2 12.2 15.3 3.5 33.3 4.8 Chrysothrix candelaris 7.5 6.9 15.3 12.0 16.1 2.2 16.1 17.0 Diorygma hieroglyphicum 10.3 Diorygma junghuhnii 5.7 30.5 Dirinaria aegialita 24.5 45.91 14.2 15.3 21.0 20.0 35.9 42.8 17.7 42.1 16.1 15.4 Dirinaria consimilis 15.4 Graphina anguina 8.6 Graphis breussii 2.8 Graphis cincta 10.2 5.4 5.2 1.5 Graphis lineola 5.5 Graphis stenotera 4.2 Herpothallon flavominutum 18.6 Herpothallon granulosum 10.0 44.2 Herpothallon himalaya 11.8 Herpothallon isidiatum 41.8 Herpothallon philippinum 21.5 55.4 Heterodermia diademata 11.0 2.3 Heterodermia firmula 10.4 Heterodermia speciosa 11.4 Banko Janakari, Vol 32 No. 2 11 Karmacharya et al. Name of lichen species Industrial areas Heavy traffic areas Residential areas Clean areas 1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Hyperphyscia adglutinata Var. pyrithrocardia 32.0 30.0 7.2 12.9 Hyperphyscia isidiata 6.7 Hyperphyscia minor 25.3 4.77 30.3 21.8 9.4 6.1 Hypotrachyna cirrhata 2.3 Lecanora achroa 16.7 5.4 Lecanora chlarotera 4.7 Lepraria sp. 27.4 74.1 41.14 29.9 15.9 28.9 16.8 34.5 21.7 21.2 45.6 5.9 11.0 Leptogium burnetiae 2.4 Leptogium wilsonii 3.0 13.9 Lithocalla ecorticata 38.70 Myelochroa xantholepis 5.0 Opeltia flavorubescens 5.2 Pallidogramme divaricoides 11.8 Parmotrema austrosinense 7.1 Parmotrema praesorediosum 2.9 19.4 5.3 7.8 12.4 6.6 6.6 Parmotrema reticulatum 7.6 21.6 Parmotrema tinctorum 4.5 6.7 1.8 2.8 7.5 Phaeophyscia hispidula var. hispidula 12.4 25.3 67.7 61.6 25.6 26.9 16.3 7.3 25.3 8.8 43.3 7.4 Phaeophyscia pyrrhophora 3.0 Phyllopsora corallina 33.2 Physcia abuensis 7.7 Physcia aipolia 3.7 13.3 Physcia crispa 35.1 45.3 Physcia dubia 20.0 12.7 69.6 2.2 13.4 11.6 1.5 6.2 Physcia integrata 1.6 15.9 Physcia sorediosa 52.8 35.6 35.7 25.2 106.02 37.7 14.8 42.1 43.2 66.3 22.6 75.7 32.5 47.7 39.6 50.8 12.5 14.5 9.4 Polymeridium submuriforme 37.9 Pyrenula astroidea 8.1 Pyrenula submastophora 4.1 Pyxine reticulata 9.7 7.5 8.3 Pyxine subcinerea 37.4 11.7 18.0 6.1 Remototrachyna awasthii 9.1 5.5 Remototrachyna flexilis 1.0 Banko Janakari, Vol 32 No. 2 12 Karmacharya et al. Discussion Lichen species found in Kathmandu valley This study revealed that a total of 97 species of corticolous lichens are found in Kathmandu valley (Table 1). Previously, Baniya et al. (2001) enumerated 99 species of lichens from Shivapuri (clean forest area), Kathmandu and Sikles, Pokhara. But in this case, 97 species of bark-inhabiting lichens were reported only from Kathmandu valley. This number is quite high in comparison to the previous study from Kathmandu valley alone, which may be due to the variation in topography and heterogeneity in a climate with diverse vegetation in the study areas which provides good habitat for the luxuriant growth of lichens. The rich lichen flora in a particular region was dependent upon their growth, development, diversity and a wide range of interrelated environmental factors (Brunialt & Giordani, 2003; Sequiera & Muktesh, 2008). Similarly, Chonbang et al., (2018) observed that the distribution of lichen community was significantly affected by elevation gradient, different land use types and variations in canopy openness in the Kanchenjunga Conservation area, eastern Nepal. In recent years, many Nepalese lichenologists have enumerated and studied the distribution pattern of lichen flora in different parts of the country. In this contest, Baniya & Gupta (2002) reported 77 species from Thodimai of Annapurna Conservation Areas and 78 species from the buffer zone of Makalu-Barun National Park. Similarly, Devkota (2008) enumerated 32 species of lichens from Phulchowki Hill, Lalitpur. In the same way, Baral (2015) reported 68 species from Sagarmatha National Park and 13 species from Manaslu Conservation Area. Among the species recorded from Kathmandu Valley, 18 lichen species of Graphidaceae are new records for Nepal (Karmacharya et al., 2018). Similarly, Rai et al. (2016) added 28 species of lichens from Dadeldhura, Mahakali Zone, as new to Nepal. These findings indicate the occurrence of rich lichen flora in the country and many areas are still unexplored lichenologically. Among the 21 families reported in this study, Parmeliaceae and Graphidaceae, which exhibited the same number of species were the largest families in the Kathmandu valley. Globally these two families are the largest with 2,765 lichen species under Parmeliaceae and 2,161 species under Graphidaceae (Lucking et al., 2016). Similarly, the finding of Singh & Sinha (1997) also supported our study as they reported Parmeliaceae (199 species) is the largest family in India. This study recorded the corticolous lichens with the green algae as a photobiont in most of the study areas whereas cyanophycean lichens with blue-green algae as photobiont showed poor diversity representing only two species of a single-family Collymataceae. Cyanophycean lichens are shade-adopted and moisture- dependent. Hence these two cyanolichens were found in shade and moisture conditions. Many numbers of shade-loving and moisture-tolerant cyanophycean lichens including Collemataceae were observed in the Bolampatti II forest range, in Tamil Nadu, India (Balaji and Hariharan, 2013). Among the growth form studied, crustose lichens dominate the study areas followed by foliose lichens. Contrary to this, Chongbang et al. (2018) observed a higher number of foliose lichens compared to other growth forms in the Kanchenjunga Conservation area of eastern Nepal. This difference in growth forms might be due to the variation in habitat as Kathmandu valley is a polluted urban area whereas Kanchejunga is a comparatively clean area. They also observed that the area was dominated by corticolous lichens and showed poor diversity of cyanophycean lichens supporting this study. In the study, fruticose lichens were reported only from higher altitudes. This finding is comparable to Pinokiyo et al. (2008), who observed a higher abundance of crustose lichens than other growth forms and an absence of fruticose lichens at lower altitudes of Arunachal Pradesh in northeast India. Fruticose lichens prefer areas having good air quality with appropriate light conditions (Wolseley and Pryor, 1999). Lichen diversity The study of importance value (table 2) investigated the effect of different areas of pollution gradients on the distribution and diversity of corticolous lichens. The distribution Banko Janakari, Vol 32 No. 2 13 Karmacharya et al. and species richness of corticolous lichens were not uniform and were found different in different study areas of Kathmandu valley. Undisturbed (clean) areas have rich lichen diversity and supported more species compared to sampling sites of disturbed (polluted) areas (industrial, heavy traffic and residential areas) (Table 2). Similar results have been obtained by various researchers (Das et al., 2013; Agnanet al., 2017; Khastini et al., 2019). Pinokiyo et al. (2008), also observed a higher number of corticolous lichen species in the dense forest of the undisturbed central zone than in areas along the roadsides located towards the periphery of the Sanctuary in northeast India. Distribution and diversity of epiphytic lichen flora are influenced by changes in microclimate, air quality, local sources of disturbance, alteration in environmental pollution and habitat fragmentation (Brunialti & Giordani, 2003; Moen & Jonsson, 2003; Jayalal et al., 2015; Das et al., 2013; Khastini et al., 2019). In the present study, the occurrence of a higher number of lichen species in undisturbed areas could be due to the presence of forest patches with dense vegetation, suitable environmental conditions, sufficient moisture, unpolluted air and undisturbed stratum (Purvis, 2000; Nayaka, 2014; Jayalal et al., 2015). On the contrary, the decrease of lichen species in disturbed (polluted) areas may be the cause of industrial activities, the density of road traffic and anthropogenic activities which influence the epiphytic vegetation to decline (Gombert, et al. 2004; Seaward, 2008; Llop et al., 2012; Das et al., 2013; Sett & Kundu, 2016; Khastini et al., 2019). Weerakon et al., (2020) observed that the diversity and community composition of corticolous lichens were strongly influenced by the richness of tree species, vegetation type and disturbance in the study area. The present study revealed that the most common and dominant group of lichens species in Kathmandu valley were Candelaria concolor (Dicks.) Arnold, Dirinaria aegialita (Afzel. ex Ach.) B.J. Moore, Lepraria sp., (Afzel. ex Ach.) B.J. Moore, Phaeophyscia hispidula var. hispidula (Ach.) Essl. and Physcia sorediosa (Vain.) Lynge. These species were reported from all the study areas of different degrees of pollution levels (Industrial, heavy traffic, residential and clean areas) and have comparatively high importance values in disturbed areas (Table 2). Candelaria concolor and Lepraria sp. are nitrophilous species and are able to thrive in both polluted and clean areas (Fibrous et al., 2017). Similarly, Dirinaria aegialita and members of lichen belonging to physciaceae (Phaeophyscia hispidula var. hispidula and Physcia sorediosa) are pollution- tolerant species and able to exist in areas with high anthropogenic activity (Shukla & Upreti, 2011; Nag et al., 2020; Díaz et al., 2021). Among these species, Candelaria concolor and Physcia sorediosa exhibited the highest importance value in polluted areas indicating more tolerant species than other species. Hence, the high IV value of these species can be used as suitable indicators for monitoring air quality. Epiphytic lichens are good indicators to monitor air quality as they are very sensitive to changing environments (Das et al., 2013; Jayalal et al., 2015; Varela et al., 2018; Loppi, 2019). The species like Bacidia incongruens, Remototrachyna flexilis, Hypotrachyna cirrhata and Leptogium burnetiae which showed their occurrence in undisturbed (clean) areas having no industries, less traffic and minimum anthropogenic activities can be considered sensitive species. Similarly, the lichen species having high importance value and mostly growing in more or less polluted sites with industrial, heavy traffic and anthropogenic activities (disturbed areas) can be considered pollution-tolerant species (Mishra et al., 2016). In this way, the distribution and diversity of tolerant and sensitive lichens species help to distinguish the high and less polluted localities in the study areas. Conclusion The study showed that a total of 97 species of corticolous lichens are found in Kathmandu valley indicating the lichen species richness of study areas. The areas with rich lichen diversity indicate a low level of environmental pollution whereas the areas with poor lichen diversity indicates a high level of pollution. The most dominant species of the valley are Candelaria concolor, Dirinaria aegialita, Lepraria sp., Phaeophyscia hispidula var. hispidula and Physcia sorediosa, which Banko Janakari, Vol 32 No. 2 14 Karmacharya et al. can be considered pollution-tolerant species whereas the species like Bacidia incongruens, Remototrachyna flexilis, Hypotrachyna cirrhata and Leptogium burnetiaeare are rare species that can be considered pollution-sensitive species. In this way, the present study helps us to learn about tolerant and sensitive species of the valley. The findings of this research provide a suitable platform for monitoring the air quality of Kathmandu Valley using these species for future purposes. Acknowledgments Neena Karmacharya is thankful to the University Grant Commission, Bhaktapur, Nepal for the award of a Ph.D. fellowship and grant and Nepal Association of Science and Technology (NAST) and Indian National Science and Technology (INSA) for the financial support to visit CSIR– National Botanical Research Institute, Lucknow, India. The Department of Botany, Amrit Campus, Tribhuvan University, Kathmandu, Nepal and CSIR–National Botanical Research Institute, Lucknow, India are also highly acknowledged for providing laboratory facilities for lichen identification. References Agnan, Y., Probst, A., & Séjalon-Delmas, N. (2017). Evaluation of lichen species resistance to atmospheric metal pollution by coupling diversity and bioaccumulation approaches: A new bioindication scale for French forested areas. 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