The genus Salacia (Celastraceae: Salaciodeae) in peninsular India

Mayur Dhondiram Nandikar, Naoroji Godrej Centre for Plant Research

Celastraceae consists of 96 genera and about 1300 species (Mabberley 2017), distributed in tropical, subtropical and temperate parts of the world. In India, the family (including Hippocrateaceae) is represented by 15 genera and about 114 species (Ramamurthy and Naithani 2000). The classification of Celastraceae has undergone several revisions based on molecular evidence and it is now recognized with four subfamilies (Celastroideae, Stackhousioideae, Hippocrateoideae and Salacioideae). Subfamily Salacioideae consists of six genera and most of the species within this subfamily are lianas. Cheiloclini-um Miers, Peritassa Miers and Tontelea Miers are confined to South America, Salacighia Loes. and Thyrosalacia Loes. are native to tropical Africa, whereas one of the largest genera, Salacia L., is distributed in both the Old and New World tropics (Simmons 2004). Salacia is perhaps best known as the source of salacinol, an antidiabetic compound (Yoshikawa et al. 1997).

Among the members of Celastraceae from India, the species of Salaciaresembles those of Loeseneriella A.C. Sm. and Reissantia N. Hallé, but differs by their axillary or ramiflorous fascicles, thyrsiform or paniculate cymes, intrastaminal fleshy, annular pulvinate or flattened disc 2 or 3 inserted stamens from the pistil base, 2- or 3-celled, 1–8 ovulate ovary, drupaceous or baccate; mucilaginous (pulpy) or dry meso or endocarp, 1–8-seeded, indehiscent fruits. Reissantia has entire-margined petals and an inconspicuous disc, whereas Loeseneriella has involute petals and a conspicuous disc . Moreover, both these latter genera possess axillary, dichotomously branched cymes, with or without supplementary branchlets in dichotomy, capsular, dehiscent fruit, and winged seeds . Historically these three genera were often placed in Hippocrateaceae along with Hippocratea L. In more recent classifications, however, Hippocrateoideae and Salacioideae are included in Celastraceae as monophyletic groups representing dif-ferent lineages.

Fruits of Hippocrateoideae are dehiscent mericarps with winged seeds, whereas those of Sala-cioideae are indehiscent and drupaceous (Robson 1965; Ding Hou 1964; Robson et al. 1994; Simmons et al.2001; Coughenour et al. 2010, 2011). The genus Salacia consists of about 200 species worldwide (Mabberley 2017). The group is most diverse in tropical Africa with approximately 90 species (Hallé 1962); remaining taxa are distributed in southeast Asia with nearly 30 species (Ding Hou 1964; Pelser et al. 2016), and neotropics with 33 species (Smith 1940; Hed-in 1999; Lombardi 2014). Ramamurthy and Naithani (2000) recognized 21 species of Salacia in India, 11 of which are endemic to the country. Subsequently three further species and one variety have been described from peninsular India (Udayan et al. 2012, 2013, 2014; Sujana et al. 2015, Page and Nandikar 2020). Among the Indian species, Salaciaf loribundaWight, S. jenkinsii Kurz and S. khasiana Pu rk ay. a re known from North East India, whereas S. majumdarii(Chakrab. & M.Gangop.) B.D. Naithani, S. platyphyllaKurz and S. tortuosa Griff. occurs on the Andaman and Nicobar Islands. Salacia grandiflora Kurz, S. salacioides(Roxb.) R.S.Rao & Hemadri and S. verrucosa Wight are common to North East India as well as the Andaman and Nicobar Islands. S. chinensis L. occurs throughout peninsular India and the Andaman Islands, whereas S. oblonga Wight & Arn. is restricted to the Western Ghats of India and Sri Lanka. Salacia is more diverse in peninsular India than other parts of the country.

Of the ten species recorded so far, eight are endemic to this part of the country: S. agasthiamalana Udayan, Yohannan & Pradeep, S. brunoniana Wight & Arn., S. fruticosa Heyne ex M.A.Lawson, S. galmbleana Whiting & Kaul, S. mac-rosperma Wight, S. malabarica Gamble, S. megacarpaN.V.Page & Nandikar and S. wayanadica Sujana, Naga-raju, M.K.R.Narayanan & Anil Kumar. Salacia meg-acarpa is the only species that has large, ridged, green mature fruit with a dry endocarp. Salacia agasthiamala-na is unique in having small, elliptic, obovate leaves and fruits with a thin epicarp. Salacia vellaniana Udayan, Yohannan & Pradeep, wrongly synonymized under S.gambleanaby Sasidharan & Anaz (2015), is considered conspecific to S. macrosperma. In S. macrosperma, the fruitshave been described unclearly. In the protologue, fruits were given as irregularly ovate, and in illustration fruit vary from globose to obovoid to ellipsoid, smooth (Wight 1845). The original material (housed at K) has broadly ellipsoid-oblong fruit. Nevertheless, most col-lections of S. macrosperma from peninsular India also bears globose to oblong fruits with a smooth to sparsely tuberculate exocarp. Hence, taxonomic delimitation of S. macrosperma from its congeneric S. beddomei Gamble and S. brunoniana is often difficult. Incidentally, both the latter species were described without fruit. In the case of S. beddomei, it was found to be conspecific with S. macrosperma due to similarities in leaf shape, size, flowers.

On the other hand, S. brunoniana is retained as distinct species, as it differs from S. macrosperma by having serrate leaves, and few-flowered fascicles. The claimed occurrence of S. macrophylla and S. reticulata in peninsular India by Ramamurthy and Naithani (2000) is based on misidentifications. The former was identified based on the work of Ding Hou (1964), which was based on Dalzell’s collection from Konkan. The present author had an opportunity to scrutinize Dalzell’s collection of S. oblonga at K which is erroneously determined by Ding Hou as S. macrophylla. Similarly, S. reticulata Wight (1840) does not occur in India. It was based on a collection of Colonel Walker from Ceylon (Sri Lanka). In the protologue, Wight was uncertain about its distribution in India. Subsequently, Gamble (1918) incorrectly included this species based on a collection of Rao(874 4 0 at CAL), and misinterpreted the type specimen (C.P. 2720 at CAL) of the Sri Lankan endemic S. diandra Thwaites as S. reticulata (seeUdayan and Pradeep 2012).

DOI: https://doi.org/10.36253/jopt-10390

Read Full Text: https://oaj.fupress.net/index.php/webbia/article/view/10390

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