Syzygium namborense D. Dey, N. Devi & J. Sarma, 2022

Dey, Debolina, Sarma, Jatindra & Devi, Nilakshee, 2022, Syzygium namborense (Myrtaceae), a new species from Assam, India, Phytotaxa 538 (2), pp. 133-140 : 134

Syzygium namborense D. Dey, N. Devi & J. Sarma , sp. nov. ( Figures 1–4 ; Table 1 ).

Type:— INDIA. Assam: Golaghat district, Nambor Reserve Forest, Murphulani , 72m, 27 April 2019, 26 ° 22’36.53” N, 93 ° 46’55.49” E, D. Dey DDS2401 (holotype ASSAM!, isotype GUBH!) .

Syzygium namborense resembles S yzygium nervosum in having glabrous, chartaceous and aromatic leaves, paniculate inflorescence with second order branching, calyptrate flowers, numerous stamens and equal number of petals in the calyptra but differs in having more compressed branchlets with internodes 1.5–2 cm (versus internodes 6–7.7 cm in S.nervosum ) and with up to 20 leaves (vs. up to 8 leaves), blades with acumen up to 0.6 cm (vs. up to 1 cm), strictly elliptic leaves with acuminate apex and cuneate base, greater number of lateral veins, intramarginal vein uniform along the blade, sessile yellowish white flowers with obconical hypanthium (vs. greenish white flowers with campanulate hypanthium and pedicel to 2 cm) and 20–30 ovules per locule (vs. 12–15 ovules per locule).

Tree 8–15 m tall, 45–52 cm in diameter at body height. Bark coarse, olive green outside eventually turning into black, pale white inside. Branchlets terete, compressed, each with up to 20 leaves at a time, old branchlets greyish white, dry, young branchlets green, fleshy. Nodes thick, slightly angular, 1.5–2 cm apart. Leaves with petioles 1.2–2.5 cm long, the blades simple, opposite and decussate, chartaceous, glabrous, elliptic, 5–18 × 1.1–6.5 cm, cuneate at base, entire to slightly repand at margins, acuminate at apex, pellucid punctuate on both the surfaces, midrib sulcate above, raised below, secondary nerves 13–15 at each side, prominent beneath, forming intramarginal loops near the margin, acumen ca. 0.6 cm long. Inflorescences panicles, usually on leafless old twigs, axillary, 54–65-flowered, main axis 5–7 cm long, bracts minute, 0.1–0.2 cm long, caducous. Flowers yellowish white, 1–1.2 cm long, sessile, calyptrate, the calyptra 0.2 × 0.2 cm, rhombic, often persistent; hypanthium pellucid punctuate, obconical, slightly tapering towards the base, 0.4–0.5 × 0.3–0.5 cm; sepals 4, free, succulent, deciduous, deltate-prolate, rarely attached to the calyptra; petals 4, unified into a calyptra, each 0.1–0.2 cm long, orange brown at the center, white at the periphery with thin longitudinal grooves, irregularly elliptic, pellucid punctate, shortly clawed; stamens white, 60–80 per flower, 0.2–0.5 cm long, filaments slender, anther sacs parallel, dorsifixed, dehiscing by longitudinal slits; style 0.45 cm long, slightly bent; stigma falcate; ovary with axillary placentation; o vules 20–30 per locule. Fruits not seen.

Distribution, habitat and ecology:—So far, Syzygium namborense is known only from the tropical semi-evergreen forests of Murphulani, Nambor Reserve Forest, Golaghat district and moist deciduous forests of Donkamukam, Rongkhang Reserve Forest, West Karbi Anglong district of Assam ( Figure. 4 ). It generally grows on open areas of forest edge mostly at the base of hilltops between 71–77 m elev.

During the entire survey, only two populations of the species were recorded in Assam. The first population was recorded from Nambor RF consisting of 1 matured individual while the second population was recorded from Rongkhang RF consisting of 5 individuals. Both locations are severely affected by various anthropogenic factors like logging and human settlements. The other associated plants located in the type locality (Nambor RF) were Carallia brachiata ( Loureiro 1790: 296) Merrill (1919: 249) , Gynocardia odorata R. Brown (1820: 95) , Mangifera indica Linnaeus (1753: 200) and Syzygium cumini ( Linnaeus 1753: 471) Skeels (1912: 25) , whereas Syzygium nervosum, Clerodendrum glandulosum Lindley (1844 : t. 19) and Chromolaena odorata ( Linnaeus 1759: 1205) R.M. King & H. Robinson (1970: 204) were located in the other locality (Rongkhang RF).

Note:—The leaves and flowers give off a strong fruity aroma and harbor a large number of insects, especially ants. They gather around at every node in large numbers and feed on the oozing sap ( Figure 2C ).

Phenology:—Flowering occurs from April to June. Fruits were not seen.

Paratypes:— INDIA. Assam: Golaghat district, Nambor Reserve Forest, Murphulani , 72m, 27 April 2019, 26 ° 22’36.53” N, 93 ° 46’55.49” E, D. Dey DDS2403 ( GUBH!); West Karbi Anglong district , Rongkhang Reserve Forest , Donkamukam , 76m, 18 August 2019, 25 ° 58’0.65” N, 92 ° 43’2.39” E, J . Sarma JS 1500 ( GUBH!) .

Etymology:—This new species is named after the type location, Nambor Reserve Forest of Assam.

Affinities:— Syzygium namborense has resemblances with Syzygium nervosum with which it is compared in the diagnosis and in Table 1 .

Figures

FIGURE 1. Syzygium namborense. Holotype.

FIGURE 2. Syzygium namborense. A. Foliage; B. Flowering twig with inflorescence; C. Part of node showing association with ants; D. Part of inflorescence (Photo by D. Dey).

FIGURE 3. Syzygium namborense. A. Habit; B. Young branchlet with leaves; C. Inflorescence; D–E. Dorsal and ventral sides of a leaf; F. A portion of the inflorescence; G–I. Buds showing united petals (calyptra), free sepals and stamens bent inward; J. An open flower with sepals attached to the calyx; K. An open flower with sepals attached to the calyptra; L–M. Dorsal and ventral sides of the calyptra; N. Petals; O. Longitudinal section of the hypanthium showing the gynoecium (Photos by D. Dey, based on holotype).

FIGURE 4. Distribution map of Syzygium namborense in Assam (Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap under ODbL).