Hanguana sitinurbayai Randi, 2023

Randi, Agusti, Widodo, R. M. Wiwied & Adirahmanta, Sadtata N., 2023, Hanguana sitinurbayai (Hanguanaceae), a new species from mossy montane forest of Gunung Nyiut Penrissen, West Kalimantan, Indonesia, Phytotaxa 606 (3), pp. 231-236 : 231-234

Hanguana sitinurbayai Randi , sp. nov. ( Figs 1 & 2 ).

Type:— INDONESIA. Kalimantan Barat Province, Gunung Nyiut Nature Reserve (Cagar Alam Gunung Nyiut), 1540 m elev., 18 August 2022, Randi KB-1076 (holotype: WAN!; isotype: BO!, FIPIA!) .

Diagnosis:— H. sitinurbayai is the only known Hanguana species that grows in the mossy montane forest. It is differing from other species in that the stigmas are united to form a triangle with rounded corners, seed appendage large with retuse apex and pointy projection at the outer surface, often with 2 sterile bracts on peduncle, the habit solitary without leafless rhizomatous stem, pistillate flowers in a pair as usually found in another Hanguana species does not occur in this new species.

Solitary dioecious herb, to 80 cm tall, ascending crown of leaves; stem erect, covered by leaves entirely, leafless rhizomatous stem absent, or if present only at very base of plant near the roots, up to 5 cm long, ca. 1 cm diameter; stolons absent. Leaves spreading well along stem, bases imbricate; whole leaf up to 80 cm long (including pseudopetiole), slightly arching or straight, pseudopetiole 10–26 cm long, 1.1–1.8 cm wide at the middle, bluntly V-shaped in cross section, with sharp margins, covered with floccose hairs on both sides; lamina narrowly elliptic, 43–60 × 4.4–6.3 cm; base narrowly attenuate, margins entire and widely undulate, apex narrowly tapering with sharp tip; adaxial surface light to dark green, sometimes with a striking dark green horizontal stripes pattern, semi-glossy, glabrous, abaxial surface pale green to whitish, covered with densely floccose hairs; midrib stout to semi-weakly impressed, sunken above, round-raised below. Staminate inflorescence not observed. Pistillate inflorescence/infructescence erect, sometimes arching with ageing as ripe fruits gain weight, not deflexed, comprising 4–6 partials, alternate-secund, thyrsoid inflorescence with a terminal spike; peduncle and rachis together up to 55 cm long, green to brownish purple when fresh, with dense scattered simple and floccose silky hairs; visible portion of peduncle up to 30 cm long, 0.6–1.0 cm diameter at the bottom; often with 2 sterile bracts per peduncle, 5–9 cm apart, very rarely but sometimes with 3 sterile bracts, foliaceous, persistent; lower sterile bract lanceolate, 15–31 × 1.9–4.2 cm (including 2.2–4.3 cm long claw/pseudopetiole), base attenuate, apex caudate; upper sterile bract much smaller and narrower than lower one, 6.5–8.1 × 0.7–2.0 cm; fertile bracts one for each partial inflorescence, the most basal bract at partial inflorescence narrowly triangle, 1.2–7.5 × 0.4–1 cm, base without pseudopetiole, clasping a half to 2/3 of rachis; uppermost fertile bract much smaller, triangle, 5–7 × 4–6 cm; partial inflorescence comprising up to 7 branches at basal level, fewer towards the apex of the inflorescence, branches arising simultaneously from the axis of the subtending bract, lateral branches progressively shorter; longest median branch up to 8 cm long, unbranched or further branching to one order. Pistillate flowers scattered, solitary, sessile, associated minute bracteoles not seen; perianth ca. 6 mm across, composed of 6 tepals in two whorls tightly clasping ovary/fruit in fresh material, all tepals thick and fleshy with prominent bulbous thickening at base (more prominent in outer whorl), light green when fresh; outer tepals broadly ovate, 2 × 3 mm, with sparsely arachnoid externally, glabrous and shiny internally; inner tepals circular or near so, 3–4 mm across, basal free, margin hyaline translucent white, externally with a few arachnoid hairs at apex, glabrous internally; staminodes 6, in two whorls, cream to pale green when fresh with dark brown tip, outer staminodes narrowly triangular, 0.7–1.0 mm long, 0.5–0.8 mm at base, inner staminodes triangular, 1.1–1.4 mm long, 1.0– 1.2 mm wide at base, each basally sheathed with broadly ovate staminodial scale, ca. 1.5 × 1 mm, apex rounded, dark brown with translucent margin; stigmas united, forming a triangular shape with rounded corners, ca. 1.5 mm across, dark brown to black in fresh fruiting material, in matured fruits positioned centrally or slightly oblique, slightly raised or somewhat flat with pericarp surface. Ripe fruits bright pink to magenta, globose, slightly depressed at apex, 7–10 mm across, very weakly 3-lobed with three faint lines from below the tip, glabrous and shiny, or sometimes with sparse minute hairs at base; pericarp 0.9–1.1 mm thick. Seeds 1–2 per fruit, 4.4–5.7 mm across, dark brown to black; deeply bowl-shaped with flat, slightly thickened and incurved margin, a large appendage positioned on the distal part of the rim, ca. 1.6 × 2.5 mm, apex retuse, externally with pointy projection at the outer surface, cavity filled with semi-translucent placental tissue.

Distribution:—Endemic to Borneo, so far only known from Gunung Nyiut Nature Reserve (Cagar Alam Gunung Nyiut), West Kalimantan, Indonesia.

Ecology and habitat:— H. sitinurbayai forming a big population in the mossy montane forest especially in the unique trapped and isolated large swamps of the Nyiut mountains at 1540 m elev. This species is also spreading abundantly on slopes ranging from 1200 to 1640 m elev.

Etymology:— The epithet of Hanguana sitinurbayai is derived from the name after Professor Siti Nurbaya Bakar, the honourable Minister of Environment and Forestry of the Republic of Indonesia (2014–present).

Provisional conservation status assessment:—This species is only known from single location within a fully protected forest area. Hard-to-reach locations, under the same conditions this species also has an abundant population, and no any threats for the habitat observed. According to IUCN Standards and Petitions Subcommittee (2022), the species would be best placed as Least Concern (LC).

Notes:—This new species is superficially resembled with Hanguana bakoensis Siti Nurfazilah, Sofiman Othman & P.C.Boyce (2011: 140) according to their habit, leaf shape, infructescence and fruits colouration, however H. sitinurbayai can be easily distinguished from the presence of indumentums where almost all parts of the plant are covered by scattered and densely floccose hairs, whereas all parts of H. bakoensis are glabrous except for peduncle and rachis of inflorescence; H. sitinurbayai generally has 2 or 3 sterile bracts while H. bakoensis consistently has a single sterile bract. Apart from that, other clear differences can be spotted in generative characters such as much larger fruits on H. sitinurbayai (7–10 mm across vs. 5 × 3.5 mm on H. bakoensis ), stigmas united, forming a triangular shape with rounded corners (vs. stigma 3-lobed, joined to form a clover-leaf shape), seeds much larger, 4.4–5.7 mm across, and deeply bowl-shaped (vs. seeds much smaller, ca. 3.5 mm across, and shallowly cupuliform), different shape of tepals (outer tepals broadly ovate 2 × 3 mm, inner ones circular 3–4 mm across vs. outer tepals ovate 1 × 1 mm, inner ones ovate 2 × 2 mm).

Additional specimens examined:— Hanguana bakoensis : MALAYSIA. Sarawak. Bako N. P.: Lintang Trail , 27 May 2007, Nadiah I., Malcom D., Army K. et al. S.100599 ( SAR!-image); Telok Tajor, 7 June 1963, P. S. Ashton, S.17960 ( SAR!-image); Ulu Sawit Camp, 29 June 1960, J. A. R. Anderson, S.11858 ( SAR!-image); Path near Bukit Keruing, 28 March 1960, J. A. R. Anderson 12489 ( SAR!-image) .

Figures

FIGURE 1. Hanguana sitinurbayai Randi.A–B. Plant habit in situ. C. Habit of single plant. D. Indumentum on abaxial leaf surface. E–F. Lamina, adaxial and abaxial surface. All photos by A. Randi from type specimen.

FIGURE 2. Hanguana sitinurbayai Randi.A. Whole infructescence with sterile and fertile bracts. B. Detail of partial infructescence. C. Perianth, and detail of staminodes and staminodial scales. D–E. Ripe fruit, side and top view. F–H. Seed from top, side and front view.All photos by A. Randi from type specimen.