A Checklist of Stenoendemic Angiosperms of Tamil Nadu

Vol. 34(2): 87–117 (2024) ISSN: 0971-2313 (Print edition) ISSN: 2582-2438 (Online edition) https://dx.doi.org/10.22244/rheedea.2024.34.02.02 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Nithaniyal S.1*, Irwin S.J.2 & Narasimhan D.3 1Botanical Survey of India (BSI), Western Regional Centre (WRC), Koregaon Road, Pune, Maharashtra – 411001, India 2No. 76/1, Arul Garden, Sundarapuram, Coimbatore, Tamil Nadu – 641 024, India 3Associate Professor (Retd.), Department of Botany, Madras Christian College (Autonomous), Chennai – 600059, India *E-mail: [email protected].in Abstract: Inventory of endemic species is sparse in the country and lacks state-wise assessment and nationwide compilation. Here, we report a comprehensive record of the stenoendemic angiosperms of Tamil Nadu and highlight the priority areas for conservation. A critical perusal of existing literature points out that 272 endemic taxa belonging to 138 genera representing 59 families and ten diverse clades of APG IV. Maximum numbers of endemic taxa are from Cyperaceae and the genus Impatiens. Endemic plants are concentrated in the floristically rich Western Ghats of Tamil Nadu, covering the areas of Tirunelveli, Nilgiris, and Coimbatore districts. The vegetation gradient occurring at the Western Ghats hill slopes of Tamil Nadu is a home for many centres of endemism that provide a micro-habitat for speciation. Out of 272 endemic taxa reported, 71 of them are classified under the IUCN threatened category, that include Critically Endangered (33), Endangered (32), Vulnerable (5) and Extinct (1), representing taxa that demand a high priority for conservation. Evaluation of conservation status based on IUCN Red List Categories and Criteria showed that endemic taxa in micro-endemic centres of Tamil Nadu is facing a high risk of extinction due to the decline in population size, area of distribution, habitat fragmentation, and anthropogenic pressures. Therefore, the current study on the inventory of endemic species will be helpful to implement appropriate conservation strategies. Keywords: Endemics, Western Ghats, Micro Habitat, Threatened Species, Conservation Introduction Despite attempts to halt the extinction crisis, biodiversity loss due to anthropogenic pressure has increased worldwide (Cardinale et al., 2012). Therefore, an inventory of floral diversity to develop conservation strategies is essential to achieve the targets of the Kunming-Montreal Global biodiversity framework as envisioned by the Convention on Biological Diversity. Endemic species are unique to a site or restricted area, biotope, biogeographical region, or a political boundary based on the spatial distribution pattern (Daru et al., 2020). Endemic diversity exploration is therefore, necessary in mega-diversity countries with exceptionally high species richness. The terms “paleoendemic” and “neoendemic” are used to classify endemics based on evolutionary characters and historical biogeography. Paleoendemics are characterized by woody habit, low level of polyploidy, and usually form monotypic genera or families with a disjunct distribution as evidenced in fossil records (Stebbins & Major, 1965; Kruckeberg & Rabinowitz, 1985). Whereas neoendemics are characterized by herbaceous or shrubby habits having a high level of polyploidy that belong to polytypic genera and form a species complex with no clear taxonomic boundaries and related taxa occurring in the same or adjacent region (Kruckeberg, 2002; López-Pujol et al., 2011). Endemism also increases with the increase in size of a homogenous biogeographical area with Received: 18.08.2023; Revised & Accepted: 05.06.2024 Published Online: 30.06.2024 Rheedea Journal of the Indian Association for Angiosperm Taxonomy RESEARCH ARTICLE 88 A Checklist of Stenoendemic Angiosperms of Tamil Nadu the same floristic history and ecological conditions (Peñas et al., 2005). Stenoendemic or local endemic species stand as the biological capital of the country, reflecting the unique species richness (Nayar, 1996). India, a mega-diversity country, comprises 22,108 angiosperm species, including 4036 endemic species distributed in the 12 biogeographical provinces, five biomes, and three bioregion domains (Singh et al., 2015; Mao et al., 2022). Endemism is concentrated in the floristically rich mega centres, namely Eastern Himalayas, Western Ghats, North-eastern India, and Andaman and the Nicobar Islands. These biodiversity hotspots exhibit unique endemic species diversity but also experience habitat loss that resulted in many species being included under the threatened category by IUCN (Marchese, 2015). The state of Tamil Nadu occurs in the southernmost part of the Indian peninsula and has rich angiosperm diversity due to the varied vegetation types. This region supports an array of habitats such as forests, grasslands, wetlands, and coastal plains with unique endemic species diversity. The Hill ranges of the Western Ghats are considered as a major centre of endemism in Tamil Nadu (Narasimhan & Irwin, 2021). The Western Ghats harbor most of the angiosperms described in India, and the Agasthyamalai Range alone includes more than 50% of the species (Meher-Homji & Pascal, 1996). However, in recent decades, human accelerated habitat fragmentation has increased the species’ extinction rate in their natural habitats. Agriculture, monoculture practices, hydroelectric projects, and climate change are the causes of the extinction of endemics (Davidar et al., 2007). The knowledge on the phytodiversity and phytogeography are essential for implementing conservation strategies. Therefore, this study focuses on the inventory of endemic species to facilitate the conservation measures for species and genetic diversity from extinction. Researchers from all over the world are utilizing the IUCN framework in biodiversity studies to establish conservation methodologies for structuring policies towards the conservation of species through multilateral agreements, as well as to prioritize species for conservation (Betts et al., 2020). Nevertheless, there are several shortfalls or data deficiencies about species taxonomy, distributions, abundance, evolutionary patterns, abiotic tolerances of species, biotic interactions, and limited understanding of species traits that hinder the biodiversity studies (Brown & Lomolino, 1998; Lomolino, 2004; Cardoso et al., 2011; Diniz-Filhom et al., 2013; Hortal et al., 2015). Recent studies also highlighted the shortfalls of species distribution, identification, evolution, and dynamics during the biodiversity assessments (Shaltout & Bedair 2021; Shaltout & Bedair 2023). Assessment studies in India reported that 2,142 out of 18,532 taxa are red-listed under the category of threatened (432 taxa), near threatened (52 taxa), and extinct (8) (IUCN, 2024, Gowthami et al., 2021). Diversity analysis of narrow endemic angiosperms in different states of India showed that the highest taxa were reported in Tamil Nadu (410 taxa), followed by Kerala (357 taxa) and Maharashtra (278 taxa) (Singh et al., 2015). Likewise, assessment studies of endemic taxa were attempted in different regions of Southern India (Daniels et al., 1995; Narayanasamy & Natesan, 2020). For instance, the Conservation Assessment and Management Prioritization (CAMP) assessment on medicinal plants has listed 256 taxa, 36 of which were designated as endangered (Molur et al., 1995). A study by Ramesh and Pascal (1997) revealed that 70% of endemic trees are home to Agasthyamalai highlands. Another research on developing the Database on Endemic and red-listed species in Agasthyamalai Biosphere Reserve reported 126 out of 2270 taxa were endemic (Narasimhan & Irwin, 2017). However, a consolidated report of endemic and red-listed species taxa of Tamil Nadu is not available, and it is not easy to access data from various sources. 89 Nithaniyal et al. Therefore, a comprehensive survey of endemics was undertaken using existing literature and other field records. This study reports 272 stenoendemics in Tamil Nadu of which 71 taxa were red-listed by IUCN. The current study aims to (i) catalogue the stenoendemic angiosperms of Tamil Nadu, (ii) identify the areas of endemism in Tamil Nadu, with particular reference to Western Ghats, (iii) improve the understanding of the phytogeographic pattern of endemism, and (iv) discovery and rediscovery of endemics in Tamil Nadu. Materials and Methods Study Area Tamil Nadu, the southernmost state of the Indian peninsula, is spread over a 1,30,058 km2 landmass, accounting for about 4% of the country’s total area. The state lies between 8° 5’ – 13° 35’ N latitude and 76° 14’ – 80° 21’ E longitude with an elevation ranging from sea level to 2637 MSL (Fig. 1). The Bay of Bengal bounds the state to the east, the Indian Ocean to the south, and the Arabian Sea to the southwest and the state of Kerala to the west, Karnataka to the northwest, Andhra Pradesh to the north, and parts of Puducherry, a Union Territory, along the east-central coast (Fig. 1). The state is administratively subdivided into 38 districts. Topographically, the state is divided into the Western Ghats, Eastern Ghats, Central Plateau, and Coastal Plains. Rainfall varies from 900 mm to 3000 mm, and it benefits from both southwest and northeast monsoons. The state generally enjoys a humid tropical climate and has varied topography and habitats. A recent study by the Forest Survey of India (2021) reported that Tamil Nadu has a forest cover of about 26,419 Km2 that constitutes 20.31% of the state’s total geographical area, and is ranked ninth in the country. Much of the forest is open, whereas very dense and moderately dense account for about 11% of the total forest area. More than 80% of the Fig. 1 . Distribution of micro-endemic centres of Tamil Nadu. Map drawn with QGIS Firenze v.3.28.0 (QGIS development team, 2024). 90 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Fig. 2 . Some of the endemic and threatened taxa of Tamil Nadu. a. Phyllanthus singampattianus (Sebast. & A.N. Henry) Kumari & Chandrab.; b. Huberantha senjiana (R. Mural., D.Naras. & N.Balach.) R.Mural., D.Naras. & N.Balach.; c. Premna mundanthuraiensis Rajendran & P.Daniel; d. Barleria durairajii K. Ravik., D.Naras., Devanath. & Gnanasek.; e. Hedyotis rajasekaranii Karupp. & V.Ravich.; f. Hedyotis shettyi K.Ravik. & V. Lakshm.; g. Memecylon manickamii Murugan, Sundaresan & Jothi; h. Sonerila parameswaranii K.Ravik. & V. Lakshm.; i. Eugenia megamalayana Murugan & Arum.; j. Impatiens megamalayana Ramas.; k. I. flavescens Karupp. & V. Ravich.; l. Calophyllum pascalianum B.R.Ramesh, Ayyappan & De Franceschi. 91 Nithaniyal et al. total forest cover is distributed between 0 – 1000 m altitude (Narasimhan & Irwin, 2021; FSI, 2021). Methods Floras, research articles, reports, and books were referred for the checklist preparation of stenoendemics angiosperms of Tamil Nadu (Hooker, 1872-1897; Gamble, 1915-1936; Ahmedullah & Nayar, 1986; Nayar and Sastry 1987-1990; Henry et al., 1987; Henry et al., 1989; Ahmedullah, 2000; Kameswara et al., 2003; Nayar et al., 2014; Singh et al., 2015; Narasimhan and Irwin 2017; Mao & Dash, 2020; Dash & Mao, 2020; Narasimhan & Irwin, 2021). Type information of each taxon was collected from published literature of the 19th, 20th and 21st centuries. Nomenclature of botanical names was confirmed by the Plants of the World Online (POWO) (https://powo.science.kew. org/) and World Flora Online (http://www. worldfloraonline.org/) databases. The checklist on stenoendemics of Tamil Nadu was based on APG IV classification (Table 1) (APG, 2016). The conservation status of each taxon was obtained using the IUCN Red List of Threatened Species database (https://www.iucnredlist.org/), the CAMP assessment using taxon data sheet (Molur et al., 1995; Gopalan and Henry 2000) and other reports based on the existing database and field records. Results and Discussion 1. Stenoendemic angiosperms of Tamil Nadu The current study records 272 endemic taxa belonging to 138 genera from 59 families and ten diverse clades of APG IV (Fig. 2). Clade-wise distribution of endemics indicates that 70% of taxa are from Core Eudicots, and the Monocots clade represents 25% of taxa. Eudicots represent 75% of the world’s angiosperms (approximately 190,000 described species) as a large monophyletic assemblage (Simpson, 2010). Analysis of speciesrich families reveals that the maximum endemic taxa are from Cyperaceae, followed by Poaceae and Balsaminaceae with at least 18 taxa. However, at the generic level, Impatiens tops the list with 18 taxa, followed by Fimbristylis and Ceropegia. Fiftyeight percent of endemic taxa are herbaceous, that occur in diverse habitats such as coastal plains, grasslands, evergreen forests, and deciduous forests. The other life forms, such as shrubs, trees, liana, and climbers, are represented by 21%, 16%, and 5%, respectively. Earlier studies have reported that endemic trees were predominant over herbs (Ganesh et al., 1996) and endemic shrubs were dominant as compared to the trees (Krishnan & Davidar, 1996). However, the present results show the dominance of the herbaceous endemics over the trees, shrubs, and climbers, which is comparable to the study conducted in the Northern Western Ghats and Konkan regions of India (Joshi & Janarthanam, 2004; Gaikwad et al., 2014). Habitat diversity is vital in microevolution as more than 50% are herbaceous taxa, sheltered in specific microhabitats including rock outcrops and grasslands. Specific conservation programs for herbaceous species are challenging to execute; however, the gene pool of herbaceous taxa at higher elevations is well-preserved by microhabitats. 2. Areas of endemism Several endemic taxa have been reported in the Western Ghats of Tamil Nadu in the last two decades, which calls for attention to conservation (Sarvalingam & Rajendran, 2016; Arya et al., 2021). Therefore, region-wise exploration is essential to document the spatio-temporal distribution of endemics. In the current study, district-wise analysis showed that 30% of endemic taxa are found to occur in Tirunelveli, followed by the Nilgiris (21%) and Coimbatore (18%) districts. High endemic diversity in the Western Ghats of Tamil Nadu occurs in the four micro endemic centers, namely the Agasthyamala Biosphere Reserve, Palani Hills, Anamalai Hills, and NilgirisWayanad-Kodagu Tri-junction (Nayar, 1980). Our study revealed that nearly 80% of endemic taxa were represented within the protected areas 92 A Checklist of Stenoendemic Angiosperms of Tamil Nadu such as Anamalai Tiger Reserve, KalakkadMundanthurai Tiger Reserve, Megamalai Wildlife Sanctuary, Kanyakumari Wildlife Sanctuary, Kodaikanal Wildlife Sanctuary, Courtallum hills, Mahendragiri Hills, and Velliangiri Hills (Fig. 1). These regions represent prioritized locations for the in-situ conservation of taxa and regular monitoring of the gene pool in the natural habitat. The unique endemics are much pronounced in the Western Ghats, which capture facets of biodiversity not described elsewhere (Joshi & Karanth, 2013). About 20% of endemic taxa are from the Eastern Ghats and the Coastal plains. Regions like Kolli Hills, Kalrayan Hills, Jawadhu Hills, Pachamalai Hills, Gingee Hills, and Shevaroy Hills represented the areas of micro endemic centers for conservation (Fig. 1). Species such as Tetrastigma tamilnadense N.Balach. & K.Ravik., Zeuxine chowdheryi Av.Bhattacharjee & Sabap., Commelina tricolor E.Barnes, and Fimbristylis murthyi Yarrayya & Ratna Kumar occur in both the Eastern and Western Ghats. The tropical ecosystem faces a high degree of extinction of endemic taxa due to climate change and habitat loss (Kidane et al., 2019). About 26% of endemic taxa in Tamil Nadu are classified under IUCN red-list categories that include Critically Endangered (33), Endangered (32), Vulnerable (5) and Extinct (1) (Table 2). Analysis of the redlisted threatened taxa revealed that the family Melastomataceae (10) holds more threatened taxa, followed by the family Balsaminaceae (8), Fabaceae (6), and Acanthaceae (6). Threatened species often face a high risk of extinction due to a decline in population size and distribution, habitat fragmentation, and anthropogenic pressures. Therefore, implementation of conservation strategies for Indian endemic species requires an understanding of species taxonomy, phenology, distribution, and identification of priority areas rich in endemic taxa. Further, by employing the current biotechnological tools and approaches, we could be able to preserve the genetic pool of the threatened endemic taxa (Coelho et al., 2020). 3. Phytogeographic patterns of endemism High species richness is one of the characteristic features of a humid tropical ecosystem. The tropical Indian landscape has a heterogeneous climatic history and topography that supports four global biodiversity hotspots from ten different phytogeographic zones (Rodgers & Panwar, 1988). The state of Tamil Nadu harbors complex phytogeographic regions like the Eastern Ghats and Western Ghats. The Western Ghats of Tamil Nadu sustain lineages of ancient tropical vegetation that were once part of Gondwanaland and encountered intense volcanic activity in the late Cretaceous period (Prasad, 2009). Eventually, the percentage of endemism is comparatively high in the Western Ghats as this region is favoured by factors like altitude gradient, unique rainfall pattern, and short dry season length (Joshi & Karanth, 2013). Our analysis based on the endemics at altitude gradient showed that the maximum numbers of taxa are from the high-elevation regions of Tamil Nadu. Seventy percent of endemics are concentrated in the high-elevation regions of the Eastern and Western Ghats. Our study indicated that 187 taxa are confined to high-elevation areas representing 48 families from 93 genera and 26 orders. The highest number of endemic taxa is from the monocot order Poales representing 40 taxa from 19 genera and three families. The Wet Evergreen Forests supported the higher number of endemics, followed by the Moist Deciduous Forests, Montane Wet Temperate Forests, and Shola Forests. We also observed that the altitude gradient influences the vegetation types in the Agasthyamalai and the Nilgiris massifs that hold the unique vegetation and provide microhabitats for the species. Earlier studies reported that the areas of endemism are associated with high mountain ranges where the degree of endemicity and richness were related to topographic complexity and elevational range (Noroozi et al., 2018; Nerlekar et al., 2022). Conservation of such 93 Nithaniyal et al. endemic species, especially in the Indian savannah, depends on understanding forest ecosystem dynamics and phytogeographic patterns (Nerlekar et al., 2022). Climatologically, the mid-elevational zone does not exhibit very extreme cold temperatures (Page & Shanker, 2020). In the mid-elevation region (500-1000 msl), about 39 endemic taxa belonged to 22 families from 15 genera, and 14 orders were identified from the Eastern Ghats and the Western Ghats of Tamil Nadu. It was dominated by six taxa belonging to Gentianales, five from Ericales, and four taxa each from the orders Asparagales, Lamiales, and Magnoliales. Vegetation that supports include Dry Deciduous Forests, Moist Deciduous Forests, Evergreen Forests, SemiEvergreen Forests, Thorn Forests, and Grasslands. Similarly, the lowland zone, including the coastal regions and inland plains, consists of vegetation like Deciduous Forests and Dry forests, which holds 46 endemic taxa belonging to 32 genera from 18 families and eleven orders. Dominating orders are Poales, Lamiales, and Fabales, representing eleven, nine, and seven taxa, respectively. Earlier studies reported the largest number of endemic species from the plateaus, followed by the moist deciduous, semi-evergreen, and evergreen forests (Joshi & Janarthanam, 2004). Based on the Mountain Geo-biodiversity Hypothesis, we can understand that mountain formation and upliftment influence the regional geodiversity patterns (Mosbrugger, 2018). The Western Ghats in Tamil Nadu also show unique geodiversity patterns in Agasthyamalai, Anamalai, Palani Hills, Silent Valley, and the Nilgiris range. The highest peaks of Western Ghats include Doddabeta (2637 m) and Kolaribeta (2629 m), located in the Nilgiris and the Vandaravu Peak (2553 m) in Palani Hills (Narasimhan & Irwin, 2021). These mountain regions provide refugia for several endemics, which experienced an increased chance of allopatric speciation due to environmental gradient followed by the ‘speciespump’ effect (Doebeli & Dieckmann, 2003). The climatic shifts in these geographical regions lead to low levels of change in species distributions and may allow the survival of ancient lineages that have become extinct elsewhere (Harrison & Noss, 2017; Daru, 2020). However, in the Eastern Ghats, regions such as Kalrayan Hill, Jawadhu Hills, Kolli Hills, and Pachamalai areas could have experienced higher historic temperature changes and tend to harbor fewer endemic species. Phylogenetically derived species often occupy higher altitude in the Eastern Ghats, indicating the elevation-driven isolation of endemics. These observations were comparable to earlier studies that highlighted that elevation-driven isolation had significantly shaped the patterns of endemic species richness (Noroozi et al., 2018; Nerlekar et al., 2022). 4. Discovery and rediscovery of endemics of Tamil Nadu The Discovery of new species is one of the prime interests of botanical research. Tamil Nadu stands in the top third in India’s Discovery of new species (Mao et al., 2022). Systematic investigation of plants presumably started during the 18th century in Tamil Nadu. Nearly nineteen new taxa were reported in the Madras Journal of Literature and Science, Flora of British India, Icones Plantarum Indiae Orientalis, and Journal of the Linnean Society Botany. These new taxa were considered endemic to Tamil Nadu because they were not reported elsewhere since then. The oldest endemic species identified was Semecarpus anacardium var. cuneifolia in 1825 by A.P. de Candolle in Prodromus Systematis Naturalis Regni Vegetabilis. Interestingly, three species of the 19th century that were considered extinct such as Koilodepas calycinum Bedd., Aerva wightii Hook.f., and Andrographis rothii C.B. Clarke, were rediscovered after 100 years. Exploration in Tamil Nadu was more prevalent during the 20th century. Out of 272 taxa that were reported here, about 40% (108) were discovered during this period from the Western Ghats of 94 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Tamil Nadu, which were not reported elsewhere. In the late 1970s, about nineteen new taxa from Cyperaceae were reported by Govindarajulu in the Proceedings of the Indian Academy of Sciences, Journal of the Bombay Natural History Society, and Rheedea that remained as endemic species. Reports on rediscovery of 20th-century taxa such as Impatiens laticornis C.E.C. Fisch., Eriochrysis rangacharii C.E.C. Fisch., Senecio kundaicus C.E.C. Fisch., Berberis nilghiriensis Ahrendt, Elaeocarpus blascoi Weibel, Dalbergia tinnevelliensis Thoth., Andrographis rotundifolia (Sreem.) Sreem., Indotristicha tirunelveliana Sharma, Karthik. & Shetty and Hiptage nayarii R.C. Srivast., highlighted the intensive field studies during recent decades. The floristic exploration was remarkable in the last three decades of the 21st century, and about 145 new endemic taxa were identified from Tamil Nadu. Discovery of new endemic species in the 21st century increased many folds compared to the 19th and 20th centuries. The availability of regional experts, regular field exploration, funding resources, and e-communication are the primary reasons for the increasing pace of species discovery. This also indicates that a list of endemics in a particular geographic region may vary from time to time and is indefinable. Recent technological advancements greatly support taxonomic exploration by providing quick access to online databases, botanical literature, and resources, including type specimens for rapid confirmation and unambiguous identification. Further, the evolving DNA sequencing methodology could speed up plant identification by complementing the traditional taxonomic approaches (Bhavisha and Thaker, 2017; de Boer et al., 2022). In the upcoming years, a lot newer new species may be discovered utilizing the emerging molecular techniques which are crucial for functional taxonomic research in India. 5. Conclusion Exploration of endemic taxa is essential for insitu and ex-situ conservation and to regulate conservation policies. The current study enlisted 272 endemic taxa of Tamil Nadu, representing 138 genera and 59 families. Herbaceous endemics dominated the trees, shrubs, and climbers. The vegetation gradient occurring at hill slopes of the Western Ghats acts as a microhabitat for speciation. About 26% of endemics are threatened, which indicates the high risk of extinction of these taxa. Furthermore, many endemic taxa attract medicinal and timber value, which could be over-extracted from the wild, leading to extinction. In addition, loss of habitat, decline in population, and anthropogenic pressure severely affect the population status of endemics. Therefore, the current study reinforces the need to assess all the endemics based on IUCN guidelines. The comprehensive data on threatened endemic taxa enlisted from this study could help to implement conservation strategies and to preserve the unique endemic taxa. Acknowledgements The authors thank the National Biodiversity Authority and Tamil Nadu State Biodiversity Board, Chennai. We also thank the Joint Director, Botanical Survey of India, Southern Regional Circle, for providing the Herbarium and library facilities. The authors also acknowledge Dr. K. Ravikumar, Emeritus Professor, The University of Trans-disciplinary Health Sciences and Technology (TDU), Bengaluru, Dr. K. Karthigeyan, Scientist ‘F’, Botanical Survey of India, Southern Regional Centre, Coimbatore, and Dr. R. Muralidharan, Assistant Professor, D.G. Vaishnav College, Chennai, for providing the plant photographs. We thank Mr. Thirumurugan V, Madras Christian College (Autonomous), Chennai, for preparing the Map. 95 Nithaniyal et al. Table 1: List of endemic taxa of Tamil Nadu Sl.No Family Botanical Name 1 Ranunculaceae Clematis gouriana Roxb. ex DC., var. mollifolia W.T. Wang 2 Ranunculaceae Clematis theobromina Dunn 3 Annonaceae Huberantha senjiana (R. Mural., D. Naras. & N. Balach.) R. Mural., D.Naras. & N.Balach. 4 Annonaceae Miliusa flaviviridis N.V. Page, Poti & K. Ravik. 5 Annonaceae Miliusa manickamiana Murugan 6 Annonaceae Miliusa tirunelvelica Murugan, Manickam, Sundaresan & Jothi 7 Annonaceae Miliusa velutina (Dunal) Hook.f. & Thomson, var. deviyarina S.M. Rajendran, S.C. Agarwal & H.N. Verma 8 Annonaceae Monoon tirunelveliense (M.B. Viswan. & Manik.) B.Xue & R.M.K. Saunders 9 Berberidaceae Berberis nilghiriensis Ahrendt 10 Capparaceae Capparis kollimalayana M.B. Viswan. 11 Capparaceae Capparis danielii Murugan, R. Manik., S.P. Nithya, B. Karthik & Arisdason 12 Pittosporaceae Pittosporum anamallayense M.P. Nayar & G.S. Giri 13 Polygalaceae Polygala arillata Buch.-Ham. ex D. Don, var. revoluta (Mukerjee) G.S. Giri 14 Caryophyllaceae Polycarpaea corymbosa (L.) Lam. var. diffusa (Wight & Arn.) S.R.Ramesh & Razi 15 Clusiaceae Agasthiyamalaia pauciflora (Bedd.) S. Rajkumar & Janarth. 16 Calophyllaceae Calophyllum pascalianum B.R. Ramesh, Ayyappan & De Franceschi 17 Malvaceae Corchorus tirunelveliensis Kalaiselvan, Selvak. & Rajakumar 18 Malvaceae Grewia kothayarensis Murugan & Manickam 19 Elaeocarpaceae Elaeocarpus blascoi Weibel 20 Malpighiaceae Hiptage nayarii R.C. Srivast. 21 Oxalidaceae Biophytum longibracteatum Tadul. & K.C. Jacob 22 Oxalidaceae Biophytum puliyangudiense Rajakumar, Selvak., S.Murug. & Chellap. 23 Balsaminaceae Impatiens agastyamalayensis (Bhaskar) A. Joe, Bhaskar & M. Sabu 24 Balsaminaceae Impatiens aliciae C.E.C.Fisch., Bull. Misc. Inform. Kew 1934(9): 389.1934 var. pandavaramalayensis Bhaskar 25 Balsaminaceae Impatiens aquatica Bhaskar 26 Balsaminaceae Impatiens courtallensis Ramas. & Pandur. 27 Balsaminaceae Impatiens debilis Turez. 28 Balsaminaceae Impatiens dindigulensis Ramas., Anjana & Chandra 29 Balsaminaceae Impatiens flavescens Karupp. & V. Ravich. 30 Balsaminaceae Impatiens kawttyana Chhabra & Ramneek 31 Balsaminaceae Impatiens laticornis C.E.C. Fisch. 32 Balsaminaceae Impatiens megamalayana Ramas. 102 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Sl.No Family Botanical Name 237 Cyperaceae Fimbristylis sivarajanii W. Khan & R.D. Taur 238 Cyperaceae Fimbristylis strigosa Govind. 239 Cyperaceae Fimbristylis tortifolia Govind. 240 Cyperaceae Fimbristylis velliangiriensis Murug., V.Balas. & Nagarajan 241 Cyperaceae Fuirena pubescens (Poir.) Kunth var. pergamentacea C.E.C.Fisch. 242 Cyperaceae Scleria swamyi Govind., 243 Orchidaceae Habenaria denticulata Rchb.f. 244 Orchidaceae Habenaria pallideviridis Seidenf. ex K.M. Mathew 245 Orchidaceae Habenaria polyodon Hook.f. 246 Orchidaceae Liparis beddomei Ridl. 247 Orchidaceae Luisia megamalaiana Karupp. & V.Ravich 248 Orchidaceae Oberonia balakrishnanii R. Ansari 249 Orchidaceae Polystachya seidenfadeniana Mytnik & Baranow 250 Orchidaceae Tropidia hegderaoi S.Misra 251 Orchidaceae Zeuxine chowdheryi Av.Bhattacharjee & Sabap. 252 Poaceae Acrachne henrardiana (Bor) S. M. Phillips. 253 Poaceae Agrostis schmidii (Hook.f.) Fischer. 254 Poaceae Andropogon longipes Hack. 255 Poaceae Brachiaria nilagirica Bor 256 Poaceae Chloris wightiana Nees ex Steud. 257 Poaceae Chrysopogon copei Mohanan & Ravi 258 Poaceae Dimeria jayachandranii Arisdason & P. Daniel 259 Poaceae Dimeria kollimalayana Mohanan & Rao 260 Poaceae Enteropogon coimbatorensis K K. N. Nair, Jain & Nayar 261 Poaceae Eragrostis rottleri Stapf 262 Poaceae Eriochrysis rangacharii Fischer 263 Poaceae Helictotrichon polyneurum (Hook. f.) Henrard. 264 Poaceae Isachne deccanensis Bor 265 Poaceae Ischaemum koenigii (Hook. f.) Stapf ex Fischer. 266 Poaceae Polypogon nilgiricus Kabeer & V.J.Nair 267 Poaceae Trachys copeana Kabeer & V.J. Nair 268 Poaceae Trachys narasimhanii Ravich. 269 Poaceae Tripogon ashihoi Murug., Arum. & Kabeer 270 Poaceae Tripogon borii Kabeer, V.J.Nair & G.V.S.Murthy 271 Poaceae Tripogon copei Newmaster, V.Balas., Murug. & Ragup. 272 Poaceae Tripogon ravianus Sunil & Pradeep 103 Nithaniyal et al. Sl.No Botanical Name Family Conservation Status References 1Neuracanthus neesianus (Wight ex T. Anderson) C.B. Clarke Acanthaceae Extinct. Only two herbarium sheets of this species collected from Tami Nadu: Paloor, Palayankottai is available in the Hooker Herbarium at Kew. Kameswara et al. (2003) 2Justicia tamilnadensis P.Raja & Soosairaj, sp. nov Acanthaceae Critically Endangered. The Area of Occupancy (AOO) is c. 0.5 km² and the distribution is limited to the type locality and total population is less than 20 individuals. This species is classified in criterion B (AOO) under B2a and B2b and criterion D (number of mature individuals is less than 20) as well to meet the criteria for the Critically Endangered B2ab (ii,iii,v); D. Raja et al. (2023) 3Lepidagathis gandhii Gnanasek., A.F.J.King, S.M.Kasim & Arisdason Acanthaceae Critically Endangered. The EOO and AOO for this species are 21.2 km2 and 16 km2 respectively. Severe decline of mature individuals was observed in the field. The species is evaluated provisionally here as ‘Critically Endangered’ [CR B1b(i,iii,v)c(i) + 2b(ii,iii,v)c(ii)] following the IUCN Red List Categories and Criteria version 15.1. Gnanasekaran et al. (2023) 4Strobilanthes tricostata S. Thomas, B. Mani, Britto & Pradeep Acanthaceae Critically Endangered. The extent of occurrence (EOO) is less than 100 km2 (B1) and the area of occupancy (AOO) is less than 10 km2 (B2). It is found in only one location (B2a) and the number of mature individuals is less than 250 (C). The habitat is severely fragmented and decline observed in the area and quality of habitat (B2biii). Based on above criterion the species is assessed as critically endangered (CR). Thomas et al. (2019) Table 2: . List of IUCN red-listed threatened taxa of Tamil Nadu. 104 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Sl.No Botanical Name Family Conservation Status References 5Andrographis rotundifolia (Sreem.) Sreem. Acanthaceae Critically Endangered. The species is assessed as ‘Critically Endangered’ [CR B1a+B2a] in Boluvampatti hills, Coimbatore District, using the IUCN Red List Categories and Criteria version 3.1. Gnanasekaran & Murthy (2015) 6Barleria durairajii K. Ravik., D. Naras., Devanath. & Gnanasek. Acanthaceae Critically Endangered. The species is known only from the type locality, where it is very common. However, more explorations in similar habitats are required to know its population size, area of occupancy and extent of occurrence and threats, if any, to assess the exact threat category. Ravikumar et al. (2016) 7Andrographis rothii C.B. Clarke Acanthaceae Endangered. The species is very poorly represented in national and international herbaria by less than 10 collections and all of them have been collected from the Western Ghats of Tirunelveli district in Tamil Nadu. Therefore, the species is assessed as ‘Endangered’ [EN (B1ab(iii)+B2ab(iii)] using IUCN Red List Categories and Criteria Version 3.1. Gnanasekaran et al. (2015) 8Nothopegia vajravelui K. Ravik. & V. Lakshm. Anacardiaceae Endangered. Known from only Kudamparai Estate, Megamalai, High Wavy’s Mountains, Pachakumatetu Hills Lakshmanan & Ravikumar (1988) 9Monoon tirunelveliense (M.B. Viswan. & Manik.) B.Xue & R.M.K.Saunders Annonaceae Critically Endangered. Steno-endemic and critically endangered species distributed in the Kalakkad Mundanthurai Tiger Reserve (KMTR) in India Xue et al. (2018) 10 Ceropegia rapinatiana (Britto & Bruyns) Bruyns Apocynaceae Vulnerable. Known from only type location Tamil Nadu, Pudukkottai District, Narthamalai. Rajasekar et al. (2023) 11 Hoya kanyakumariana Henry & Swamin. Apocynaceae Critically Endangered. Gopalan & Henry (2000) 12 Ceropegia matthewiana (Bruyns & Britto) Bruyns Apocynaceae Vulnerable. Gopalan & Henry (2000) 105 Nithaniyal et al. Sl.No Botanical Name Family Conservation Status References 13 Ceropegia saldanhae (Britto & Bruyns) Bruyns Apocynaceae Vulnerable. Gopalan & Henry (2000) 14 Schefflera maduraiensis K.Ravik. & V.Lakshm. Araliaceae Endangered. Known from only two location i.e., Way to Suruli falls, Theni district and Megamalai Wildlife Sanctuary, Tamil Nadu. Ravichandran (2016) 15 Schefflera agasthiyamalayana Manickam, Murugan, Sundaresan & Jothi Araliaceae Endangered. Devika & Amitha Bachan 2023. 16 Cissampelopsis vivekananthanii Gopalan & Chithra Asteraceae Critically Endangered. Gopalan & Henry (2000) 17 Impatiens tanyae R.Kr.Singh, Arigela & Kabeer Balsaminaceae Endangered. Known from only type locality Kodaikanal Wildlife Sanctuary. Species is represented by about 195 mature individuals Arigela et al. (2019) 18 Impatiens tamilnadensis Ramas. Balsaminaceae Endangered. Known from only type locality Megamalai Wildlife Sanctuary. Raju (2020) 19 Impatiens aliciae C.E.C.Fisch. var. Balsaminaceae Critically Endangered. Known from only type locality pandavaramalai Bhaskar (2012) 20 Impatiens flavescens Karupp. & V. Ravich. Balsaminaceae Critically Endangered. Known only from a small area in Megamalai hills, Theni District, Tamil Nadu. The habitat is exposed to forest fire, cattle grazing and tourism impact, hence it is assessed as Critically Endangered (CR). Subbiah & Vellingiri (2019) 21 Impatiens megamalayana Ramas. Balsaminaceae Critically Endangered. Rare species occurring on hill tops Megamalai Hills, Theni District, Tamil Nadu, India. Therefore, the species is assessed as Critically Endangered (CR B1ab(i,ii,v); 2ab(i,ii,iv); D) in accordance with the IUCN guidelines. Ramasubbu et al. (2017) 106 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Sl.No Botanical Name Family Conservation Status References 22 Impatiens laticornis C.E.C. Fisch. Balsaminaceae Critically Endangered. The area of occupancy is about 3 km2 with only 18 matured individuals in Bangi Halla, on way to Bangitappal from upper Bhavani. Therefore, the species is provisionally assessed as Critically Endangered (CR). Tharani et al. (2021). 23 Impatiens courtallensis Ramas. & Pandur. Balsaminaceae Critically Endangered. There were only two populations (32±9 individuals per populations) observed within 0.6 km and the habitat was severally affected by landslide. Therefore, the species is assessed as critically endangered according to the IUCN. Ramasubbu et al. (2015) 24 Impatiens debilis Turez. Balsaminaceae Critically Endangered. Narasimhan & Irwin (2021) 25 Euonymus kanyakumariensis Murugan & Manickam Celastraceae Endangered. Known form only the type locality on the way to Parvathain, Mahendragiri Hills, Kanyakumari district, Tamil Nadu, India Murugan & Manickam (2005) 26 Euonymus barberi Murugan & Manickam Celastraceae Endangered. Known from only the type location Agasthiyamalai, India. Murugan & Manickam (2006) 27 Microtropis microcarpa Wight var. densiflora (Wight) Meissner Frectn. Celastraceae Endangered. 28 Agasthiyamalaia pauciflora (Bedd.) S.Rajkumar & Janarth. Clusiaceae Critically Endangered. This species has been assessed as Critically Endangered (CR B1+2c ver. 2.3 (1994) by WCMC under Poeciloneuron pauciflorum Bedd. World Conservation Monitoring Centre (2017) 107 Nithaniyal et al. Sl.No Botanical Name Family Conservation Status References 29 Cyperus coonoorensis Viji Cyperaceae Critically Endangered. The extent of occurrence (EOO) is less than 10 km2 and the area of occupancy (AOO) is less than 0.5 km2, and there are less than 250 individuals in the population, which indicates its narrow endemic nature. Therefore, preliminary conservation assessment considered this species as Critically Endangered: CR – B1a; B2a; C2a(ii) (IUCN 2012a & b, 2013). Viji et al. (2015) 30 Elaeocarpus blascoi Weibel Elaeocarpaceae Critically Endangered. There are only two known mature wild specimens of this large tree species persisting at Vattakanal Shola of Kodaikanal, Palani hills of Western Ghats, Tamil Nadu State. It is threatened with habitat loss as a result of increased forestry and agriculture. The species is assessed as Critically Endangered B1ab(iii)+2ab(iii) (IUCN 2021) Raveendran (2022) 31 Eriocaulon panagudianum R.Ansari & N.P.Balakr. Eriocaulaceae Critically Endangered. Gopalan & Henry (2000) 32 Euphorbia heyneana Spreng. subsp. nilagirica (Miq.) Panigrahi Euphorbiaceae Endangered. Known from only the type location the Nilgiri Hills Panigrahi (1974) 33 Syzygium microphyllum Gamble Myrtaceae Endangered. Known from only the type locality in the Agastyamalai Hills. More information is needed on the status of the species and direct threats to its populations. Endangered B1+2c. World Conservation Monitoring Centre (1998a) 34 Koilodepas calycinum Bedd. Euphorbiaceae Endangered. Species is known from only two collections Panagudi in Kaniyakumari and Sethur Hills in Ramanathapuram District. Therefore, preliminary conservation assessment considered this species as Endangered B1+2c. World Conservation Monitoring Centre (1998b) 108 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Sl.No Botanical Name Family Conservation Status References 35 Micrococca wightii (Hook.f.) Prain, var. angustata (S.R.M. Susila Rani & N.P. Balakr.) Radcl. -Sm. & Govaerts Euphorbiaceae Critically Endangered. Gopalan & Henry (2000) 36 Derris matthewii Kottaim. Fabaceae Vulnerable. Known from only the type location Alagar Hills, NupuragangaiPeriaaruvi valley. Kottaimuthu Vasudevan (2016) 37 Derris benthamii (Thw.) Thw. var. wightii (Baker) Thoth. Fabaceae Endangered. Known from only the type location Kalakad-Mundanthurai Tiger Reserve. Thothathri (1984) 38 Dalbergia tinnevelliensis Thoth. Fabaceae Endangered. Known from only type locality KalakadMundanthurai Tiger Reserve. Gopalan & Henry (2000) 39 Dalbergia gardneriana Benth. Fabaceae Endangered. The extent of occurrence (EOO) and area of occupancy (AOO) are 125 km2 and 28 km2, respectively, and the species is known from four locations. Therefore, the species is assessed as Endangered B1ab(iii)+2ab(iii). Plummer (2022) 40 Indigofera tirunelvelica Sanjappa Fabaceae Endangered. Gopalan & Henry (2000) 41 Dalbergia tinnevelliensis Thoth. Fabaceae Critically Endangered. Gopalan & Henry (2000) 42 Pogostemon hedgei V.S.Kumar & B.D.Sharma Lamiaceae Critically Endangered. Gopalan & Henry (2000) 43 Teucrium plectranthoides Gamble Lamiaceae Critically Endangered. Gopalan & Henry (2000) 44 Premna mundanthuraiensis Rajendran & P.Daniel Lamiaceae Endangered. Gopalan & Henry (2000) 109 Nithaniyal et al. Sl.No Botanical Name Family Conservation Status References 45 Lindernia minima (Benth.) Mukerjee Linderniaceae Endangered. Known from only two locations with a restricted area of occupancy and extent of occurrence. It has a disjunct distribution, found in Chengalpattu and in Tirunelveli on the east coast. The two known populations are threatened by commercial and residential developments. It is therefore assessed as Endangered B1ab(ii,iii,v)+2ab(ii,iii,v). Rehel (2013) 46 Hiptage nayarii R.C. Srivast. Malpighiaceae Endangered. The extent of occurrence (EOO): 6 sq. km (B1) and area of occupancy (AOO): 4 sq. km (B2). Distributed within the ranges of Ambasamudram and Mundanthurai in the Kalakad Mundanthurai Tiger Reserve (KMTR). Therefore, preliminary conservation assessment considered this species as Endangered. Viswanathan et al. (2021) 47 Osbeckia tirunelvelica Manickam & Murugan ex Kottaim. & Gnanasek. Melastomataceae Endangered. Known form only towards the road below Manjolai, Manjolai hills, Tirunelveli District, India. Kottaimuthu & Gnanasekaran (2015) 48 Memecylon tirunelvelicum Murugan, Manickam & Sundaresan Melastomataceae Endangered. Known from only Kalakad Wild Life Sanctuary, Sengaltheri-Kulirati path. Murugan et al. (2001) 49 Memecylon mundanthuraianum M.B.Viswan. & Manik. Melastomataceae Endangered. Known from only KalakadMundanthurai Tiger Reserve, near Poonkulam. Viswanathan & Manikandan (2001) 50 Memecylon manickamii Murugan Melastomataceae Endangered. Known from only KalakadMundanthurai Tiger Reserve. Narasimhan & Irwin (2021) 51 Sonerila parameswaranii K.Ravik. & V.Lakshm Melastomataceae Endangered. Known from only type locality Megamalai Wildlife Sanctuary, Theni district Ravichandran (2016) Snerila nayariana Murug. & V.Balas. Melastomataceae Endangered. Known from only Velliangiri hills, Coimbatore District, Tamil Nadu, India. Murugesan & Balasubramaniam (2011) 110 A Checklist of Stenoendemic Angiosperms of Tamil Nadu Sl.No Botanical Name Family Conservation Status References 53 Sonerila coriacea Lundin & B.Nord. Melastomataceae Endangered. Species has a very restricted distribution in the area around Mahendragiri Peak in the Tinnevelley Hills. No recent collections have been recorded since it was last collected in 1969. Therefore, its conservation status may be classified as Endangered (EN) according to IUCN Red List criteria. Lundin & Nordenstam (2009) 54 Sonerila kanniyakumariana Gopalan & A.N.Henry Melastomataceae Endangered. Gopalan & Henry (2000) 55 Sonerila sadasivanii Nayar var. kanniyakumariensis G.S.Giri & M.P.Nayar Melastomataceae Vulnerable. Gopalan & Henry (2000) 56 Sonerila inaequalis Murugan & Manickam Melastomataceae Endangered. Narasimhan & Irwin (2021) 57 Eugenia manickamiana Murugan Myrtaceae Endangered. Known from only the type location Tirunelveli District, Courtallum Hills, way to Attaikkadu from Therkkumalai Estate. 58 Eugenia megamalayana Murugan & Arum. Myrtaceae Critically Endangered. Only three individuals were seen in the coffee plantation of dry forest areas, the new taxon is assigned here as a “Critically Endangered” [CR A3c] following the IUCN Red List Categories and Criteria due to preliminary risk of extinction. Murugan & Arumugam (2019) 59 Syzygium bharathii Ramas. Myrtaceae Critically Endangered. The species is known from only one site of Megamalai hills and there were about 30 individuals observed within 4.67 km2. Hence, the species is assessed as Critically endangered (CR; Criterion B1(a), B2 +C2(a)(i),(b)+D)according to the IUCN guidelines (2016). Raju et al. (2018) 111 Nithaniyal et al. Sl.No Botanical Name Family Conservation Status References 60 Eugenia bolampattiana V.Ravich., Murug. & Murugan Myrtaceae Critically Endangered. The species is known only from the type locality, where only 18 individuals occur in a forest area of 10 km2. Its distribution has been evaluated under the Red List Categories and Criteria and is assessed here as Critically Endangered (CR B1ab(iii), B2ab(iii)). Ravichandran et al. (2020) 61 Syzygium agastyamalayanum M.B.Viswan. & Manik. Myrtaceae Critically Endangered. Tree species having two small subpopulations in the Agasthyamalai hills of the Kalakkad Mundanthurai Tiger Reserve. The area of occupancy (AOO) and the extent of occurrence (EOO) of the species are 8 km2 and the number of mature individuals limited to below 50 in severely fragmented subpopulations. The species assessed as Critically Endangered B1ab(iii)+2ab(iii); D as per IUCN guidelines. Viswanathan & Manikandan (2008) 62 Striga indica K.M.P. Kumar, P. Jayanthi, A. Rajendran & M. Sabu Orobanchaceae Critically Endangered. The population contains a maximum of c. 300 plants with very restricted distribution. A provisional threat assessment of CR B1ab(i,ii,iv) and 2ab(i,ii,iv) has been assigned as critically endangered Jayanthi et al. (2012) 63 Striga musselmanii Omalsree & V.K.Sreenivas Orobanchaceae Critically Endangered. The species is found only 1525 plants distributed in two sub populations in a very small area of 1 km2. The major threat to habitat are due to of tourism development. The conservation status is assessed here as ‘Critically Endangered [CR B1a(iii,iv)+2a(iii,iv); D]’ (IUCN 2017). Moolayil & Sreenivas (2018) 64 Phyllanthus singampattianus (Sebast. & A.N. Henry) Kumari & Chandrab. Phyllanthaceae Critically Endangered. Gopalan & Henry (2000)