Memecylon viswanathanii, a new species of Melastomataceae from Kalakkad- Mundanthurai Tiger Reserve (KMTR), India

Memecylon viswanathanii R.Rajesh, P.Sakthidhasan & C.Rajasekar, a new species of Melastomataceae, is described and illustrated from the Kalakkad-Mundanthurai Tiger Reserve (KMTR) in the southern Western Ghats of India. M. viswanathanii is close to M. parvifolium Thwaites and M. varians Thwaites but differs by several vegetative and floral characters. The species is assessed here as Critically endangered as per IUCN Red List.


INTRODUCTION
The genus Memecylon L. belonging to the family of Melastomataceae (The Angiosperm Phylogeny Group IV 2016) has 357 species (Renner et al. 2007 onwards) or around 379 . It is reported that there are 55 species distributed in India wherein 22 species are endemic to the Western Ghats (Viswanathan and Manikandan 2001;Sivu et al. 2012Sivu et al. , 2018Prabhu and Murugan 2017;Das et al. 2018;Radh and Nampy 2019;Vadhyar et al. 2020). During an inventory in 2017, plant specimens were collected from the Kalakkad-Mundanthurai Tiger Reserve (KMTR) in the southern Western Ghats of Tamil Nadu in India. A critical assessment of pertinent literature (Clarke 1879;Gamble 1919;Bremer 1979Bremer , 1987Viswanathan 2001) revealed that specimens of Memecylon collected from Vaniyangal podavu at an elevation of c. 1405 m MSL in the KMTR were hitherto unknown to science and turned out to be a new species. It is described here with a diagnosis, comparison with closely related species, detailed description, illustrations, phenology and other related details.

Diagnosis
Closely related to M. parvifolium Thwaites and M. varians Thwaites by branches and greyish bark, coria-  ceous leaves with indistinct intramarginal and lateral veins and inflorescence in axillary fascicles but differing in having broadly elliptic leaves with petioles up to 4 mm long, narrowly unbranched filiform sclereids, absence of pedicels and whitish pale blue flowers from M. parvifolium and M. varians, up to 4 mm long peduncles, warty receptacle and connective bearing gland from M. parvifolium and smaller leaves with revolute margin and shorter peduncles from M. varians (Table 1).

Etymology
The specific epithet is in honor of Prof. M.B. Viswanathan, Department of Botany, Bharathidasan University, for his contribution to the field of Plant Taxonomy in India.

Phenology
Flowering: February to April. Leaves elliptic to elliptic-obovate, cuneate at base, obtuse to rounded or notched or sometimes acute or occasionally shortly and indistinctly caudate at apex, more or less shining above, drying dark green, 1-3.5 × 0.5-2.5 cm elliptic, cuneate at base, acute to acuminate or caudate and subacute to obtuse at the very apex, more or less dull on both sides, drying yellowish green, 3-9 × 1.5-3 cm broadly elliptic, obtuse or obtusely cuneate at base, obtusely rounded, retuse or emarginate at apex, more or less shining above, drying yellowish green, 1.5-3.

Conservation Status
This species comprises 252 mature individuals in 4 populations. We recommend a conservation status of critically endangered (CR) based on IUCN Red List Guidelines and Criteria (IUCN, 2019), on the basis of B1. Extent of occurrence (EOO) -6.51 km 2 and B2 and Area of occupancy (AOO) -0.203 km 2 (Figure 3).

Taxonomic affinity
Comparison of M. parvifolium, M. varians and M. viswanathanii is given in Table 1.