Legumes of Kerala, India: a checklist

A checklist of the legumes of Kerala State is presented. This exhaustive checklist is an outcome of extensive field surveys, collection, identification and documentation of family Leguminosae carried out across Kerala State during the period 2006–2019. A total of 448 taxa were recorded under five subfamilies and 115 genera. The majority of the legumes are herbs and shrubs, the rest being trees and woody climbers. About 81 taxa are endemic to India, especially confined to the Western Ghats biodiversity hotspot, out of which 17 are endemic to Kerala. The state is home to two Critically Endangered and six Endangered legumes, facing severe threat of extinction. Crotalaria is the dominant legume genus in the state with 62 taxa followed by Desmodium and Indigofera. About 57 genera are represented by single species each. Legumes are treated according to the latest phylogenetic classification of the Legume Phylogeny Working Group (LPWG). Updated nomenclature, habit, native countries, voucher specimens, and images of endemic and lesser known legumes found in the state are provided. Crotalaria multiflora var. kurisumalayana (Sibichen & Nampy) Krishnaraj & N. Mohanan is reduced as a synonym to C. multiflora (Arn.) Benth.


INTRODUCTION
Leguminosae with 770 genera and over 19,500 species , are the third largest family of flowering plants after Orchidaceae and Asteraceae. Legumes are a significant component of nearly all terrestrial biomes, distributed throughout the world in almost all habitats and are second only to the Poaceae in their importance to human beings. The family is morphologically, physiologically, and ecologically exceptionally diverse, representing one of the most spectacular examples of evolutionary diversification in plants (LPWG 2017). Legumes are grown agriculturally, primarily for their seeds called pulses, contributing 33% of the dietary protein nitrogen needs of humans (Vance et al. 2000). Many legumes are able to do nitrogen fixation, through symbiotic association with Rhizobium bacteria within root nodules and thereby play an important ecological role in the terrestrial nitrogen cycle. Considering the importance of legumes, the 68 th session of the United Nations General Assembly declared the year 2016 as the International Year of Pulses for their popularisation internationally.
Leguminosae in India are represented by 1,297 taxa under 179 genera, of which about 23% are strictly confined to India (Sanjappa 1992). Kerala, one of the species-rich states in the country, is exceptional because of its richness in biodiversity and endemism. According to Nayar et al. (2006), Kerala represents about 4,694 species of flowering plants under 1,418 genera and 188 families. The state constitutes only 1.18% of the geographical area of India but it accommodates about 27.57% of the flowering plants occurring in the country (Nayar et al. 2008). Sasidharan (2004) and Nayar et al. (2006)  Though Leguminosae are one of the most dominant families in the state and also highly important in the economic point of view, an exclusive legume flora of the state is still wanting. To fill this lacuna, the authors have conducted extensive field surveys, collection, identification and documentation of all the legumes of the state during the last 14 years to produce a comprehensive account on the legume flora of Kerala. Regarding this, recently three new leguminous taxa and seven new records have been reported from Kerala (Predeep et al. 2008, 2009Predeep & Balan 2010;Balan & Predeep 2016;Balan et al. 2014Balan et al. , 2017. The study was initially funded by the Kerala State Council for Science, Technology and Environment, Dept. of Science & Technology, Govt. of Kerala. The present checklist is the first step before the release of a legume flora of Kerala and the list is prepared based on the authors' own collections, and specimens deposited in various Indian herbaria and relevant literature.

Systematic Treatment
Leguminosae (nom. alt. Fabaceae) received its scientific name from earlier taxonomists due to its characteristic fruit (legume). Since this name was long in usage even before the code was formulated, this name was conserved by the International Code of Nomenclature (ICN). Another name Fabaceae based on the type genus Faba Mill. was proposed as an alternate name according to the provisions of ICN and both names are acceptable following Articles 18.5 and 18.6 of the Shenzhen Code (Turland et al. 2018). The name Leguminosae or Fabaceae encompasses all the known leguminous plants under it. Monocarpellary superior ovary with marginal placentation and leguminous fruit are the key characters of Leguminosae.

MATERIALS AND METHODS
This checklist is the result of extensive field studies and repeated seasonal collections of plant specimens from Kerala during the period 2006 ̶ 2019. The plant samples belonging to Leguminosae were collected from all areas of Kerala including coastal, midland, and highlands, all types of forest and non-forest areas in all seasons of the year. Herbarium sheets were prepared following the method suggested by Bridson & Forman (1998) and are housed in the herbarium in the Malabar Botanical Garden & Institute for Plant Sciences, Kozhikode, Kerala (MBGH). Identification was done with the help of pertinent literature including national and local floras (Hooker 1876(Hooker , 1878Bourdillon 1908;Rao 1914;Gamble 1918;Manilal & Sivarajan 1982;Manilal 1988;Ramachandran & Nair 1988;Vajravelu 1990;Mohanan & Henry 1994;Sasidharan & Sivarajan 1996;Sivarajan & Mathew 1997;Mohanan & Sivadasan 2002;Kumar et al. 2005;Sunil & Sivadasan 2009;Sasidharan 2011) and revisionary studies (Sanjappa 1986(Sanjappa , 1995Thothathri 1982Thothathri , 1987Babu et al. 1987;Nair 1989;Chakrabarty & Gangopadhyay 1996a,b;Singh 2001;Bandyopadhyay et al. 2006;Ansari 2008) and consultation of authentic specimens housed at CAL, CALI, KFRI, MH, TBGT & University College Herbarium, Thiruvananthapuram. The species list is based primarily on author's collections and specimens deposited in various Indian herbaria listed in Tables 1, 2, 3, with the exception of 39 reports from the literature. The checklist is arranged according to the latest phylogenetic system of classification of legumes proposed by LPWG (2017). Each species is arranged alphabetically under respective subfamilies. Habit, native countries, selected voucher specimens and litereature references are provided for each species. Plant names are updated following International Plant Names Index (IPNI-www.ipni.org), The Plant List (www. theplantlist.org) and Tropicos (www.tropicos.org). The native range of each species is given on the basis of the International Legume Database and Information Service (ILDIS-www.ildis.org) and Plants of the World Online (www.plantsoftheworldonline.org).  (13). About 47 genera are represented by a single species only. Top 10 dominant genera are given in Fig. 1.

Leguminosae
Life form analysis (Fig. 2) revealed that, out of the 361 indigenous legumes identified from the state, the majority are herbs (124) and shrubs (95) followed by climbers (78) and trees (64).

Endemic and threatened legumes
Among the 361 indigenous legumes found in Kerala, 81 are endemic to India and 33 are confined to the Western Ghats-Sri Lanka biodiversity hotspot. Out of J TT  (IUCN 2020). Cynometra beddomei, which is treated as Extinct in the Red List, has been re-collected recently (Sasidharan 1998), and hence it can be categorised as Critically Endangered. During our field studies Dialium travancoricum is found to be the most threatened tree species in Kerala and is on the brink of extinction due to poor regeneration. This species is survived with a few numbers of very old trees in Ponmudi forest ranges of Thiruvananthapuram District. Among Endangered tree legumes, Kingiodendron pinnatum is facing severe threats due to over-exploitation and habitat destruction. The oleo-gum-resin of this plant species is used in gonorrhoea, catarrhal conditions of genito-urinary and respiratory tract (Kumar et al. 2011), and also in the paint industry. The species has been severely exploited for its wood oil in the past and the stem bark is collected as a substitute for Saraca asoca. Dalbergia travancorica is another highly threatened legume restricted to a few lowland urban sacred groves in Thiruvananthapuram (Jagadeesan et al. 2015).

Economically important legumes
Arachis hypogea (Groundnut), Cajanus cajan (Red Gram), Canavalia gladiata (Sword Bean), Cicer arietinum       www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.

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