Ophiorrhiza meenachilarensis, a new species of Rubiaceae from southern Western Ghats, India

A new species of Ophiorriza (Rubiaceae) from southern Western Ghats, India is here described and illustrated. Ophiorriza meenachilarensis is similar to O. eriantha, from which it differs in its herbaceous habit (vs. shrubby habit), densely villous-hirsute stem (vs. pubescent-glabrous stem), entire stipule (vs. bifid stipule), short-peduncled cymes (vs. comparatively long-peduncled cymes), unscented flowers (vs. scented flowers) and corolla tube with a ring of hairs at the middle of the tube (vs. corolla tube without a ring of hairs). A detailed description, illustrations, ecological observations, and geographic distribution are provided.


INTRODUCTION
Ophiorriza L. is a predominantly herbaceous genus that belongs to the tribe Ophiorrhizeae, subfamily Rubioideae, Rubiaceae (Bremer and Manen 2000). It is a species-rich genus consisting of 318 species, one subspecies and five varieties (WCSPF 2019) chiefly distributed in wet tropical forests of South-East Asia, extending to Australia, New Guinea and the Pacific Islands (Darwin 1976;Chen and Taylor 2011). The genus is taxonomically complicated and has been less-studied by taxonomists except Darwin (1976), Lo (1990), Halford (1991), Deb and Mondal (1997) and Tao and Taylor (2011). Deb and Mondal (1997) revised the genus in the Indian subcontinent, and recognized 47 species and 9 varieties from India. Since Deb and Mondal (1997), seven species have been added to the flora of India (Ramamurthy and Rajan 1985;Khan et al. 1998;Hareesh et al. 2015aHareesh et al. ,b, 2017aHareesh et al. ,b, 2018. Western Ghats is one of the diversity centres of Ophiorrhiza species followed by the north-eastern Himalayas. Nearly 21 taxa are distributed in the evergreen forest of the Western Ghats (Deb and Mondal 1997;Nayar et al. 2014).
Ophiorrhiza species are commercially important as source of Camptothecin (CPT), a potential anticancer drug. Rajan et al. (2016)  While conducting floristic explorations in the Vagamon hills of southern Western Ghats, the authors came across a few populations of a densely hairy species of Ophiorrhiza growing in moist shady areas of an evergreen forest patch in Kottayam-Idukki districts border. After critical study and comparison with other species of Ophiorrhiza and scrutiny of literature, it turned out to be quite different taxa from known species hence described as new to science and illustrated here. Final author conducted systematic screening of CPT in the newly described species and found that the CPT level is zero.

Diagnosis
Ophiorrhiza meenachilarensis shows similarities with the southern Western Ghats endemic species O. eriantha Wight, but differs by its herbaceous habit, villoushirsute indumentum on stem, leaves and inflorescence, unlobed stipules, unscented flowers, glabrous hypanthium, lanceolate, bristly calyx lobes, corolla tube with a ring of hairs within, basally inserted stamens, ovateorbicular style branches and areolate exotesta of the seeds with a number of tubercles.

Etymology
The specific epithet refers to the type locality in Kottayam district of Kerala state, where the Meenachilar River originates.

Distribution and habitat
This species is currently known only from the type locality, Vagamon hills, Kerala, India. It is growing in moist shady areas of evergreen forest at an elevation of ± 1000 m altitude, in association with Chassalia curviflora Thwaites, Clidemia hirta (L.) D. Don, Ophiorrhiza pectinata Arn., Ophiorrhiza jacobii Hareesh, Salish, G. Joseph & M. Sabu, among other species.

Phenology
Flowering and fruiting during May to September.

Conservation status
Ophiorrhiza meenachilensis is so far known only from two collections at the type locality, Vagamon Hills of Western Ghats, with an extent of occurrence estimated to be less than 10 km 2 . Extensive field surveys are needed to assign appropriate threatened category of IUCN (2012), therefore it is classified as Data Deficient (DD) according to IUCN standards.