ABSTRACT. Ixora gadgiliana Balan & Robi, sp. nov., a new species of Rubiaceae is described from the Kerala part of Southern Western Ghats, India. It is allied to I. lawsonii Gamble in its terminal, dense, short-peduncled corymbose inflorescence, but distinct from the latter by the arborescent habit, short, obovate-oblanceolate leaves with 7-9 pairs of secondary veins, comparatively small, white flowers with short, deltoid calyx lobes and beaked anthers.
KEYWORDS: Rubiaceae, Ixora, Western Ghats, threatened species, Idukki, landslides, new species.
RÉSUMÉ. Ixora gadgiliana Balan & Robi, sp. nov, une espèce nouvelle de Rubiaceae, est décrite des Ghats occidentaux méridionaux, Inde (États du Kerala). Elle est apparentée à I. lawsonii Gamble par son inflorescence en corymbe terminal, dense, à pédoncule court, mais se distingue de cette dernière par son port arborescent, ses feuilles courtes, obovales-oblancéolées avec 7-9 paires de nervures secondaires, ses fleurs blanches relativement petites avec des lobes de calice courts et deltoïdes et des anthères à bec.
MOTS CLÉS: Rubiaceae, Ixora, Ghats occidentaux, espèce menacée, Idukki, glissements de terrain, espèce nouvelle.
The genus et al. 2009; POWO 2024). It is distributed chiefly in tropical and subtropical regions of the world. The genus is easily recognized by its articulate petioles, terminal, branched cymose inflorescence, narrowly-tubular, tetramerous flowers, bilobed stigma, uni-ovulate locules and seeds with a large adaxial hilar cavity (De Block 1998). In India, the genus is represented by 47 species, of which 21 species are endemic (Nayar et al. 2014; Kottaimuthu 2016; Murugan et al. 2021). About half of the Indian endemic species are confined to the Southern Western Ghats of Karnataka, Kerala and Tamil Nadu states.
While working on the floristic diversity of Idukki district, in the Kerala part of the Southern Western Ghats, the authors collected some interesting specimens of et al. 2014; Balan & Shanmugham 2016; Kottaimuthu 2016; Gangopadhyay 2017; Murugan et al. 2021; Mathew & Pichan 2022) and comparison with the digital images of type specimens of
Plant materials were collected from the Idukki district of Kerala state and processed following the standard procedure for botanical specimens. Photographs were taken from living as well as preserved specimens. Morphological characters were studied and microscopic dissections of material were made and detailed descriptions were prepared. The plant specimens were also matched with digital images of herbarium specimens of
BAM Herbarium of the Bishop Abraham Memorial College, Thuruhticad;
BM Herbarium of the Natural History Museum;
BR Herbarium of the Meise Botanic Garden;
CAL Herbarium of the Botanical Survey of India;
E Royal Botanic Garden, Living Plant Collections, Edinburgh;
G Conservatoire et Jardin botaniques de la Ville de Genève;
K Herbarium of the Royal Botanic Gardens, Kew;
KFRI Herbarium of the Kerala Forest Research Institute;
MH Herbarium of the Tamil Nadu Agricultural University Campus, Coimbatore.
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Ixora
Flowering observed from December to January; Fruiting not seen even after observing for three consecutive seasons.
The epithet is named in honour of Prof. Madhav Dhananjaya Gadgil, a renowned Indian ecologist, in recognition of his contributions towards the conservation of Western Ghats, one of the biodiversity hotspots in India.
Very rare in its known distribution range and the population is restricted to two isolated locations. The type locality of the new species is located in a landslide-prone area identified by the Kerala State Disaster Management Authority (KSDMA). Hence, the new species is under threat due to natural calamities like landslides and soil erosion. It is located far away from the surveillance of forest department and therefore facing serious threat due to human encroachments. The conservation status of this species is proposed as Data Deficient. Further survey for this taxon is suggested.
Much branched, evergreen trees, up to 5 m tall; stem often covered with mosses and ferns; branchlets slender, glabrous; internodes short (0.8-1.5 cm). Stipules interpetiolar, ovate-truncate, 2-3 × 2-2.5 mm, glabrous, awn 2–3 mm long. Leaves opposite; petioles 4-6 mm long, thick, glabrous; lamina obovate-oblanceolate, 6-9 × 1.5-2.5 cm, acute-shortly acuminate at apex, cuneate at base, subcoriaceous, margins flat, glabrous on both sides; secondary veins 7-9 pairs, prominent beneath. Bracts supporting inflorescence foliaceous, 1.5-2.5 × 0.8-1.0 cm, ovate, shortly-acuminate at apex, obtuse at base, persistent. Inflorescence terminal, 4-5 cm long, 4 cm across, trichotomously branched corymbose cymes; peduncle branched at 1.5-2 cm from the base; branches 1.5-2 cm long, glabrous; bracts supporting flowers linear-lanceolate,1-1.2 mm long, puberulous. Flowers subsessile, bracteolate; bracteoles 0.6-0.7 mm long, lanceolate, puberulous. Calyx tube 0.8-1 mm long, glabrous; lobes 4, 0.5 mm long, deltoid. Corolla white, glabrous; tube 8 mm long, slightly broadened towards apex; lobes 4, 2.2 × 2 mm, ovate-oblong, obtuse at apex, reflexed. Stamens 4, attached at mouth, alternating with corolla lobes; filaments 0.5 mm long; anthers sub-basifixed, beaked, 2 mm long, tip pointed, sagittate at base. Ovary 2-celled, ovule 1 in each cell; style slender, 1 cm long, tip fusiform, longitudinally cleft forming two stigmatic lobes of c. 1 mm long. Fruits unknown.
The authors are grateful to the Principal and Management of Bishop Abraham Memorial College, Mallappally, Thuruthicad, Pathanamthitta, Kerala, for all the support and facilities, to Dr P. Sujanapal, KFRI, Peechi, Kerala for plant images and to Dr K. N. Gandhi, Harvard University, United States for nomenclatural suggestions. Drs Thierry Deroin, Arnaud Mouly and an anonymous referee are also thanked for their recommendations on a previous version of the manuscript.
Fig. 1. —
A, habitat;
B, stem;
C, flowering twig;
D, stipule;
E, inflorescence;
F, single flower;
G, bract;
H, bracteole;
I, calyx;
J, corolla lobe;
K, Flowering twig of
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