The diversity and distribution of polypores (Basidiomycota: Aphyllophorales) in wet evergreen and shola forests of Silent Valley National Park, southern Western Ghats, India, with three new records

The present study was conducted to document the diversity and distribution of polypores in wet evergreen and shola forests of Silent Valley National Park, Kerala State, in the southern Western Ghats, India. A combination of opportunistic and plot-based sampling was carried out in order to maximize the documentation of polypore distribution. The study was conducted throughout the entire study period of 2013–2015. Fifty-seven polypore species in 29 genera belonging to seven families were documented from the national park. The wet evergreen forest was enriched with 52 species whereas the shola forest harboured 20 polypore species. Fifteen species were found in both ecosystems while five species were exclusively found in the shola forest. The Polyporaceae was the dominant family with 30 species, followed by Hymenochaetaceae with 16 species, and Fomitopsidaceae and Meripilaceae with three species each. Ganodermataceae and Schizoporaceae made their presence with two species each while only one species was reported under family Meruliaceae. Among the polypores documented, 42 species were annuals and 15 were perennials. While analyzing the rot characteristics of the recorded polypores, it was found that white rot polypores have notable dominance over brown rot polypores. Out of the 57 species analysed, 52 polypores were white rotters and only five species were brown rotters. During the present study, three species (Phylloporia pectinata, Trametes menziesii, and Trametes ochracea) were found to be new records from the southern Western Ghats. An identification key was developed for the polypores documented from Silent Valley National Park based on micro and macro morphological features.


INTRODUCTION
The polypores are fascinating and specialized woodrotting macrofungi that play a major role in decomposition and biomass turnover in forest ecosystems. Wood rotting polypores are important elements of forest ecosystems since they decompose wood and coarse wood debris, and play a primary and central role in nutrient cycling. Most polypores depend on woody substrates while the rest are terrestrial. Most of them inhabit living wood as parasites subsequently killing them slowly and continue as saprophytes while the remaining are true saprophytes. Taxonomically, polypores are macro fungi under the division Basidiomycota and order Polyporales. They produce holobasidia and ballistosporic basidiospores typically on the inside of the tubes lining the underside of fructifications (Leelavathy & Ganesh 2000). The importance of polypores and the diversity of polypores in tropical forests were not known or not properly assessed. The tropics are a very rich source of potentially useful polypores, many of which probably have not even been recognized, described, or named (Yamashita et al. 2015).
The first Indian record of a member of polyporales was by Klotzsch (1832) when he described a total of four polypores from India. In 1833, Klotzsch described 25 polypores from the Himalayan valleys. Sundararaman & Marudarajan (1925) reported 11 species of polypores from Chennai. Butler & Bisby (1931) brought together all the records of Indian fungi in their valuable compilation The Fungi of India, which included 293 polyporoid species under 16 genera. Bakshi (1971) gave an account of 355 species of polypores belonging to 15 genera in his most outstanding work Indian Polyporaceae (on trees and timber). Roy & De (1996) listed 114 poroid species in Polyporaceae of India based on exhaustive studies on fungi belonging to the family Polyporaceae collected from different parts of India. Further, Florence (2004) reported 555 species of basidiomycetes under 179 genera from Kerala State. Bhosale et al. (2005) gave a tabulated account of 251 species of order Aphyllophorales from the Western Ghats. Swapna et al. (2008) reported 778 species of macrofungi belonging to 101 genera under 43 families from the semi-evergreen and moist deciduous forests of Shimoga District, Karnataka.
The study of the polypores of Kerala was initiated by Rangaswami et al. (1970). In his outstanding work Fungi of South India, 44 polyporoid species representing 13 genera were described, of which five species were from Kerala. Roy & De (1996) in their work Polyporaceae of India reported six polypore species from Kerala. Leelavathy & Ganesh (2000) reported 78 species belonging to 26 genera under families Ganodermataceae, Hymenochaetaceae, and Polyporaceae in their classical work Polypores of Kerala. The majority of the specimens described in that treatise was collected by the authors during the period 1983-1987 from the forests as well as inhabited areas of central and northern Kerala. Florence & Yesodharan (2000)  In Kerala, studies on polypores are done not much exhaustively as compared to mushrooms (Agaricales). The literature shows only sporadic reports and the assessments are still preliminary. Even though the polypores of Kerala were studied in detail by Bakshi (1971), Leelavathy & Ganesh (2000), and Mohanan (2011), much of the forests remain unexplored. Here we summarise the findings of the exploration of polypore diversity in specialized ecosystems like wet evergreen and shola forests of the Silent Valley NP from March 2014 to February 2015.

Study area
The Silent Valley National Park (SVNP) lies within the geographical extremes of latitudes 11 o ,[2][3][4][5][6][7][8][9][10][11]13' N & longitudes 76 o ,32' E (Fig. 1) in the southwest corner of the Nilgiri Hills of the southern Western Ghats. Silent Valley National Park constitutes part of the core area of India's first biosphere reserve, the Nilgiri Biosphere Reserve. The terrain of the SVNP is generally undulating with steep escarpments and many hillocks. The elevation ranges from 900-2300 m with the highest peak at 2383m (Anginda Peak). Both the southwestern and northeastern monsoon cause rains in this area. The major share, however, comes from the southwestern monsoon, which sets in during the first week of June. The heaviest rainfall is during the months of June, July, and August. Variation in the intensity of rainfall is observed across the area. The elevated hills on the western side of Silent Valley receive an average of 5045mm rainfall, and near Walakkad the rainfall received goes up to 6500mm.
The forests exhibit considerable variation in floristic

Survey methodology, collection, identification, and preservation of polypores
The polypores were surveyed in Silent Valley National Park (SVNP) from March 2014 to February 2015. Six permanent sample plots of size 100m × 100m were established in evergreen and shola forests (three in each ecosystem) as per the methodology followed in earlier studies (Yamashita et al. 2010;Mohanan 2011). In evergreen forests, the sample plots were taken in three different locations: Sairandhri, Poochipara, and Walakkad sections (Images 1-3). Three sample plots of shola forest were taken in different locations: Sispara, Cheriyamkandam, and Valliyamkandam (Images 4-6). The sample plots were visited during the pre- monsoon, monsoon, and post-monsoon periods for the documentation of polypores, including collection of sporocarps, labelling, identification of rot character, taking photographs, and recording macromorphological description and details of substratum in the illustrated data sheet. The rot characters were documented by examining the substrate characters and basal attached portion of polypores. A total area of 60000m 2 was surveyed in each of the three climatic seasons. Additional collection of polypores was also made from "off-plots" in the study area. Thus, a combination of opportunistic and plot-based survey was carried out to maximize the documentation of polypore diversity and distribution.
The polypore specimens collected from the study area were kept in paper bags and brought to the lab. The specimens were properly air-dried or oven-dried at 70 o C and stored in polythene zip-cover under less humid conditions. The specimens were identified based on their macro and micro morphological features. The colour names and colour codes of the specimens were given as per Kornerup & Wanscher (1967). The identification keys provided by Bakshi (1971) and Leelavathy & Ganesh (2000) were used for the confirmation of polypore species. The micromorphological characteristics of the polypores were studied using a Lieca DM 750 microscope. Some of the specimens were compared with those in the herbaria at Kerala Forest Research Institute, Peechi. The taxonomy and nomenclature are as per indexfungorum. All the specimens collected during the study period were catalogued and kept under less humid conditions in the Department of Forest Management and Utilization, College of Forestry, Kerala Agricultural University.
The diversity of polypores was calculated using PAST 3.14. The following formulae have been used to determine the diversity of polypores: 1. Simpson Index of Diversity, D = 1-∑ (ni / N) 2 (Simpson 1949) Where

Sorenson Similarity Index
Similarity of each polypore community was calculated by the following equation: QS = 2c/a+b Where, a & b represent the species numbers occurring in two different plots, and c the species occurring in both plots (Sorenson 1948).

RESULTS
Fifty-seven polypore species in 29 genera belonging to seven families were documented ( Table 1). The wet evergreen forest was enriched with 52 species whereas the shola forest harboured 20 polypore species. Fifteen species were found in both ecosystems while five species were exclusively found in shola forest (Fig. 2).
The Polyporaceae was the dominant family with 30 species followed by Hymenochaetaceae (16 sp.), Fomitopsidaceae, and Meripilaceae with three species each. Ganodermataceae and Schizoporaceae made their presence with two species each while only one species was reported under the family Meruliaceae (Fig.  3). Among the polypores documented, 42 species were annuals and 15 were perennials. While analyzing the rot characteristics of the recorded polypores, it was found that the white rot polypores had a notable dominance over brown rot polypores. Out of the 57 species analysed, 52 polypores were white rotters and only five species were brown rotters.
In order to understand the diversity attributes of the polypores in wet evergreen and shola forests, the diversity, richness, dominance, and evenness were analyzed using Simpson diversity index, Shanon-Wiener index, Pielou's evenness index, Berger-Parker dominance Index, and Margalef richness Index (Table 2).
In wet evergreen forest, Simpson's Index of diversity was observed to be 0.92 while in shola it was only 0.78. The wet evergreen forest showed higher Shanon-Wiener Index value (2.83) than that in shola forest (2.02). The Margalef richness index was also found to be relatively high in wet evergreen forest (3.15) while it was 1.74 in shola forest. The evenness in the distribution of polypores was observed to be comparatively higher in wet evergreen forest with Pielou's evenness index 0.84 than in shola forest (0.77). The shola forest showed more Berger-Parker dominance index value (0.42) in the polypore distributon while it was only 0.12 in evergreen forest ( Table 2).
Sorenson's similarity index was worked out to find the similarity of polypore community in the wet evergreen forest and shola forest during different seasons. In all the seasons similarity between polypore community in the two ecosystems was found to be low (0.44).

DISCUSSION
The present study on the diversity and distribution of polypores in wet evergreen and shola forest of Silent Valley National Park reported 57 species altogether. The species composition analysis of polypores in the wet   (2000), Mohanan (2008, 2011), and Iqbal et al. (2016. It was suggested that brown-rot has been repeatedly derived from white-rot (Gilbertson 1980). In contrast, it was also suggested that brown-rot fungi forms the plesiomorphic form in the homobasidiomycetes, and that white-rot has been repeatedly derived by elaborated wood decay mechanisms (i.e., gaining the ability to degrade lignin) (Nobles 1965(Nobles , 1971. Studies by Ryvarden (1991) and Worrall et al. (1997), however, have supported Gilbertson's view that brown-rot fungi were derived from white-rot fungi.
White-rot fungi occur frequently on hardwoods while brown-rot fungi have an obvious preference for coniferous substrates (Tuor et al. 1995;Schmidt 2006;Karami et al. 2014). Hardwood lignin is composed mainly of gluaiacyl and syringyl units. Lignin distribution, content, and composition have a significant influence on decay resistance (Frankenstein & Schmitt 2006). White-rot fungi achieve wood degradation with several different combinations of peroxidases and oxidases like ligninase, Manganese peroxidase (Mnp), Lignin peroxidase (Lip), and lactase and are able to utilize a wide variety of substrates (Tuor et al. 1995). On the other hand, white rot fungi have a geographic distribution not corresponding to their most suitable hosts (Gilbertson 1980). These views support the high proportion of white rot polypores in the study area. Leelavathy & Ganesh (2000) have reported 19 species of polypore from the national park area. Of these, 15 species were observed during the present study. Species like Hexagonia sulcata, Pycnoporus sanguineus, Trametes modesta, and Coriolopsis sanguinaria were not observed during the present study. Polypore diversity exploration in the present study added five new reports to polypores of southern Western Ghats. The identities of the species were confirmed by comparing the characters described for the specimens collected by Bakshi (1971), Ryvarden & Jonansen (1980), and Leelavathy & Ganesh (2000).
The wet evergreen forest showed relatively high polypore diversity and evenness than that of the shola forest (Table 2). Also, wet evergreen forest showed relatively high species richness (29 species) than that  of shola forest (14 species). In wet evergreen forest, Simpson's Index of diversity was observed to be 0.92, i.e., if 100 pairs of polypores were taken at random, 92 will comprise different species while in shola it was only 0.78. The species richness was also found to be relatively high in wet evergreen forest than in shola forest. The less polypore diversity and richness in the shola forest can be explained on the basis of the theory of ecological niches and strategies of saprophytic fungi by Cooke & Rayner (1984). The availability of suitable substrate is an important determinant of polypore diversity. Two characteristics of substrates influencing patterns of fungal development are the ease with which they can be assimilated and their spatial and temporal distribution (Cooke & Rayner 1984). The arborescent floras of the two forest types also contained many disjunctively distributed species. Only a few species were found to be common to both ecosystems. Tree species of shola forest is characterized by much stunted habit (seldom attaining a height above 15m) with spreading, umbrella-shaped canopy, and crooked and twiggy branches and branchlets (Nair & Menon 2000). The trees are very often covered with several epiphytic lichens, mosses, ferns, and orchids. Even though they are mostly associated with living trees, they will remain on the logs of early stages of decay. The number of logs was also noticed to be comparatively less in shola forest. It has been pointed out that a broad diversity of host tree species of various volumes, diameters, and degrees of decomposition seem to be major factors contributing to the diversity of the woodrotting fungi (Kuffer & Senn-Irlet 2005). Thus, the less availability of suitable substrate is a major factor for the low diversity and richness of polypores in shola forest.
The ecological strategy of polypores is strongly influenced by three factors: competition, stress, and disturbance (Cooke & Rayner 1984). Competition involves the struggle for capture and defence of resources between neighbours. In shola forest, the tree branches are often covered with several epiphytic lichens, mosses, ferns, and orchids which could be a barrier for the germination and establishment of polypores. Similarly, the undergrowth of shrubs like Strobilanthus sp. was found to prevent light on the fallen logs. The shady environment around the logs is not favourable for polypore establishment. Light has a wide range of effects on basidiomycete fruiting such as production, development, and abundance (Moore et al. 2008). Additionally, the undergrowth of Strobilanthus sp. may also prevent spore dispersal of the polypores in shola forests.
Further, the stress may be any form of continuously imposed environmental extremes that tend to restrict fruitbody production of polypores (Cooke & Rayner 1984). The low temperature of the shola forest could also be a limiting factor for polypore diversity. Extension rate of mycelial cord-forming basidiomycetes generally increases as the temperature does, up to optima of about 20-25 °C (A'Bear et al. 2014). The low temperature of the shola forest also cause physiological dryness to the plants growing there, restricting their moisture absorption capability from the topsoil, which is often frozen (Nair & Menon 2000). The lower temperature is, therefore, an important determinant of polypore diversity in shola forests. Finally, the disturbance describes a state in which the whole or part of the total fungal biomass is destroyed or subjected to new selection pressures by a drastic change in environmental conditions (Cooke & Rayner 1984). The severe low temperature in the shola forest could be acting as a disturbance for most of the polypores.
The evenness in the distribution of polypores was found to be comparatively high in wet evergreen forest with Pielou's Evenness Index 0.84 than in shola forest (0.77). On the other hand, shola forest showed more Berger-Parker Dominance Index value (0.42) in polypore distribution, which was low (0.12) in evergreen forest. This could be due to polypores that can tolerate the prevailing environmental severity and dominate over the rest. Species like Phylloporia pectinata, Fulvifomes cesatii, Leucophellinus hobsonii, Trametes ochracea, and Trametes pubescens were recorded only from high altitude shola forest, indicating their environmental tolerance and adaptation to disturbances.