Psychotria vasudevae Murugan & Arisdason, 2016

Murugan, C. & Arisdason, W., 2016, A new species of Psychotria (Rubiaceae) from Andaman and Nicobar Islands, India, Phytotaxa 258 (3), pp. 295-300 : 295-299

Psychotria vasudevae Murugan & Arisdason , sp. nov. ( Figs. 1. A–J & 3. A–D )

This new species is similar to Psychotria nicobarica Kurz but differs in its more slender glabrous stems (vs. very stout and rusty pubescent stems), leaves that are glabrous on the midrib and have 12 or 13 pairs of secondary veins (vs. puberulous and 15–17 pairs of secondary veins), acute and unlobed stipules (vs. acuminate and bifid stipules), longer (c. 5 mm) calyx lobes (vs. 1.5–2 mm long calyx lobes), corolla lobes pubescent outside, papillose stigma and globose fruits.

Type:— INDIA , Andaman and Nicobar Islands, Katchal Island, forest between Beechdera and Delhi Village , 04 April 1979, M. K. Vasudeva Rao 7521 (Holotype PBL, Acc No. 16476; Isotype PBL, Acc. No. 16477) .

Evergreen shrub, 2–3 m high; branchlets and stems terete, slender, glabrous. Stipules ovate, c. 7 mm long, acute at apex, not lobed, glabrous, caducous. Petioles 2–5 cm long, slender, rounded beneath, flat above, glabrous. Leaves opposite, rarely ternate, elliptic-oblanceolate, 15–30 × 15–20 cm, acute at base, entire at margins, abruptly acuminate at apex, chartaceous, glabrous, pale yellowish green when dry; lateral veins 12 or 13 pairs, glabrous, raised beneath, impressed above; tertiary veins distinct. Peduncles 1.5–2.5 cm long. Inflorescence in terminal panicled cymes, 5–7 cm long, sparsely minutely pubescent; branches slender, whorled at base, opposite towards apex, pubescent. Pedicels slender, 3–5 mm long, minutely pubescent. Flower buds ovoid, pale purple. Flowers bisexual, actinomorphic, c. 1 cm in diameter. Calyx tube campanulate, c. 2 × 1 mm, minutely pubescent; lobes ovate-lanceolate, c. 0.5 mm long, brown, acute at apex. Corolla tube cylindrical, c. 3 × 2 mm, hairy at throat; lobes oblong, c. 4 × 2 mm, recurved, acute with inflexed at apex, pale yellow. Stamens 5, exserted; filaments slender, c. 4 mm long; anthers dorsifixed, 2-celled. Ovary obconic, c. 1.5 mm long, 2-celled; ovule 1 in each cell, axile. Disk dome-shaped, c. 1. 5 mm in diameter; style slender, c. 2 mm long; stigma bifid, rather reflexed, c. 1.25 mm long, papillose. Fruits drupaceous, globose, c. 7 mm, with 6 ridges and 8 furrows, yellowish green; pyrenes 2, ovoid, dorsally 3-ridged and 4-furrowed, ventrally flat.

Flowering:—October–February; Fruiting:—March–April.

Habitat & Ecology:—Along streams, found in association with Stemona curtisii Hooker filius (1892: 298), Phyllanthus gomphocarpus Hooker filius (1887: 301) and Areca catechu Linnaeus (1753: 1189) .

Distribution:— INDIA : South Nicobar, Katchal and Little Nicobar Islands ( Fig. 2 ).

Paratypes:— INDIA , Andaman and Nicobar Islands, South Nicobar, Little Nicobar Island, Pulopanja stream, 31 October 2009, C. Murugan 27822 ( PBL, Acc. No. 26980, 26981) ; Pulopanja , 12 April 2010, C. Murugan 28127 ( PBL, Acc. No. 27375, 27376) ; Pulopanja , 07°23.324’ N, 93°43.855’ E, 16 April 2011, C. Murugan 28484 ( PBL, Acc. No. 27888, 27889) .

Etymology:—The new species is named after Dr. M.K. Vasudeva Rao, ex-Joint Director, Botanical Survey of India , Western Regional Centre, Pune, who made the first collection of this species from Katchal Island and identified it as Pavetta indica L.

Conservation Status:—During the botanical explorations in Pulopanja, Little Nicobar Island only six individuals were located. As this species has restricted range of distribution, and occupies a small geographical area, it is provisionally assessed here as Critically Endangered (CR D) using IUCN Red List Categories and Criteria version 3.1 ( IUCN 2012). However, more explorations in similar habitats are required to assess the exact threat category. To conserve this extremely rare species an ex-situ conservation effort was made. Four saplings were introduced at Dhanikari Experimental Garden-cum- Arboretum maintained by the Andaman and Nicobar Regional Centre, Botanical Survey of India, Port Blair , of which only three are surviving, and only flowering is observed.

Taxonomic Notes:—The new species is closely allied to P. nicobarica in having similar leaf shape (elliptic-oblanceolate), nature of inflorescence (terminal cyme), and 5-merous flowers, but differs in various other morphological characters as depicted in Table 1.

Figures

FIGURE 1. A–J. Psychotria vasudevae: A. Twig. B. Stipule. C. Flower. D. Bract. E. Corolla split-open. F. Pistil. G. Stamens. H & I. Ovary (L.S. & C.S.). J. Fruit (All drawn from Murugan 27822 by H. Sankar).

FIGURE 2. Map showing the distribution of Psychotria vasudevae (Rubiaceae) in Andaman and Nicobar Islands.

FIGURE 3. A–D. Psychotria vasudevae: A. Habitat (Little Nicobar Is.). B. Habit. C. Flowering twig. D. Inflorescence (All Photos were taken by C. Murugan from living plants in the type locality).