Garcinia sibeswarii P. S. Shameer, J. Sarma, N. Mohanan & A. Begum, 2021

Shameer, Peerumuhammed Subaida, Sarma, Jatindra, Mohanan, Narayanan Nair & Begum, Ajima, 2021, Garcinia sibeswarii (Clusiaceae), a new species from Assam, India, Phytotaxa 507 (2), pp. 191-197 : 192-195

Garcinia sibeswarii P. S. Shameer, J. Sarma, N. Mohanan & A. Begum , sp. nov. ( Fig. 1 & 2 )

Garcinia sibeswarii is allied to G. celebica in general habit such as branching pattern, shape and size of leaves, overall structure and position of both male and female inflorescence, number and structure of sepals and petals etc., but differs from the latter in having staminal torus 4-lobed, wavy on margins against torus tetragonous with straight margins; anthers brownish-white against anthers yellowish-white; ovary 4-celled against 8-9-celled, stigma convex-peltate, reddish against flat, 8-9-lobed, yellowish stigma; fruits 8–10 cm diameter, turning yellow on ripening against 3–5 cm diameter, turning pinkish-red on ripening; seeds reticulate-noduled on surface against nearly smooth on surface and aril brownish-white, fibrous against white pulpy aril.

Type: — INDIA. Assam: Lakhimpur District, Dulang Reserve Forest , 270 25 ’ 17.80 ’’ N, 940 10 ’ 59.40 ’’ E, 110 m alt., 24 February 2021 (female specimen in flowering, J. Sarma 1656(1) (holotype CAL!, isotypes MH!, TBGT!)

Dioecious, evergreen, medium sized trees, up to 10 m high; bark greenish brown; exudation milky; branches horizontal spreading, branchlets terete to slightly angled, glabrous. Leaves 17–20 × 10–12 cm, ovate-oblong, dark green, shiny, coriaceous, glabrous, acute or acuminate at base, acute or very shortly and abruptly acuminate apex, margin sub-repand and entire; midribs conspicuous on both sides; lateral veins conspicuous, more than 40 pairs; exudate canals conspicuous on both surfaces; petioles 2–2.5 cm long, slender, adaxially ligulate at the base. Male flowers tetramerous, 5–10, in terminal fascicles, 2–3 cm diameter, pedicel 8–12 mm long, stout; sepals free, imbricate, orbicular, concave, 6–8 × 3–4 mm, unequal, thinly coriaceous, margin membranous; petals free, pale yellow, ovate-orbicular, 8–12 × 6–10 mm, concave, coriaceous, membranous on margins; stamens numerous, inserted on fleshy white, 4-lobed torus, wavy on margins; anthers brownish-white, rudimentary pistil columnar, with a convex, peltate, reddish stigma. Female flowers tetra-merous, pale greenish-yellow, solitary, terminal, 1.5–3 cm diameter; pedicel 1–1.5 cm long; sepals free, imbricate, orbicular, concave 6–8 × 4–5 mm, margin membranous; petals 4, free, imbricate in pairs, pale greenish-yellow, ovate, 8–10 × 6–8 mm, concave, coriaceous, membraneous on margin; staminodes absent; ovary sub-globose, 4-locular, pale greenish; style very short; stigma red, sticky, peltate, convex, entire, recurved on edges. Fruits sub-globose to globose, 8–10 cm in diameter, smooth, green, turning yellow on ripening, crowned by the disclike remnant stigma and with the green leathery sepals at base. Seeds 3–4, oblong, ca. 3 × 6 cm, reticulate-noduled and rough on surface, covered with brownish-white, fibrous aril.

Phenology: —Flowering January–February; Fruiting June–August.

Habitat and Ecology: — Garcinia sibeswarii is hitherto known only from the semi evergreen vegetation of Dulang Reserve Forest, Assam at elevations between 100– 300 m. We could locate around 500 plants which include saplings and small to medium sized trees. Seedlings are very conspicuous in the locality, whereas only about 35 grownup, medium sized trees could be recorded in the entire 900.03 Hectare Dulang Reserve Forest area. The entire terrain is almost flat, barring the foot hills of adjoining Arunachal Pradesh in the north. Alluvial soil with deposits of clay and sand and layers of humus of varying depth is the general edaphic nature of the area. Surface stones and boulders are noticed within the Reserve Forest having very high porosity despite heavy rainfall for 5–6 months round the year. Dominant associated species are Dillenia indica L. (1753: 535), Garcinia cambogioides (Murray) Headland (1856: 339) , Garcinia acuminata Planch. & Trian. (1860: 355) , Gmelina arborea Roxb. (1815: t. 246, Lagerstroemia speciosa Pers. (1807: 72) , Mesua assamica (King & Prain) Kosterm. (1969: 426) , Mesua ferrea L. (1753: 515), Shorea assamica Dyer (1874: 307) , Syzygium cumini (L.) Skeels. (1912: 25), Syzygium tetragonum (Wight) Wall. ex Walp. (1843; 179) etc.

Distribution: —Hitherto known only from the type locality

Use: —The aril of the fruit is seldom taken by local people, as it is fibrous and somewhat sour to bitter in taste. But the fruits are highly relished by the primates such as the Rhesus macaque ( Macaca mulatta ) and the rare Assamese macaque ( Macaca assamensis ), very common in the area. Most of the fruits are plucked and eaten at maturity. But the seeds remain undigested and natural regeneration is primarily from the feces of these primates. Locally, the plant is known as ‘Gela thekera’ (Gela- rotten and thekera- vernacular name for Garcinia in Assamese language), thereby indicating that the fruit is not generally preferred for human consumption. A potential candidate for crop improvement programmes of Garcinia species.

Etymology:— The specific epithet is in the honour of the father of the 2 nd author, late Sri. Sibeswar Sarma, who had always encouraged and inspired his son to do works for human welfare, especially in the scientific arena.

Conservation status and IUCN red list category: —Data Deficient (DD). Hitherto known only from nearly five hundred plants, distributed in less than 1000 hectare area. The second author, a senior officer of the Assam Forest Department, has taken special interest in the conservation of the new species through regeneration and planting, throughout the Reserve Forest and in Biodiversity Parks established on the Northern Bank of Brahmaputra river.

Additional collections examined (paratypes): — INDIA. Assam: Dulang Reserve Forest , 9 March 1962, G. Panigrahi 27621 (ASSAM!); Lakhimpur, Diya, 4 April 1914, U. Kanjilal 444M (ASSAM!) .

Note: —The authors could find two herbarium specimens (both female), at BSI Eastern Circle Herbarium, (ASSAM), viz., G. Panigrahi 27621 and U. Kanjilal 444M, both erroneously identified as Garcinia mangostana L. (1753: 443). The first one is a collection from the same area (Dulang Reserve Forest, Assam), whereas the second specimen bares label Lakhimpur as the locality, which is the district name. Kanjilal et al. (1934) has included it under G. mangostana . Unique morphological features, ( Table 1 & Fig. 2 ) are enough to consider it as a distinct species, but allied to G. celebica .

Figures

FIGURE 1. Garcinia sibeswarii.A. Branch with fruit. B. Blaze showing exudates. C. Male flower. D. Female flower. E. Fruit. F. Fruit rind cut showing fibrous aril. G. Fruit cross section. H. Seed testa removed showing noduled surface. I. Mature seed.

FIGURE 2. A–F. Garcinia celebica. A. Leaf. B. Male flower. C. Female flower. D. Immature fruit showing lobed stigma. E. Fruit opened showing white pulpy aril. F. Seed.A1–F1. Garcinia sibeswarii A1. Leaf. B1. Male flower. C1. Female flower. D1. Immature fruit showing discoid stigma. E1. Fruit opened showing fibrous aril. F1. Seed.