Hanguana flavescens Hroneš & UvÍrová, 2025

Hroneš, Michal, UVÍroVá, Alena, Dančák, Martin, Boyce, Peter C. & Leong-ŠkorničkoVá, Jana, 2025, Hanguana ensifolia and H. flavescens, two new species of Hanguana (Hanguanaceae) from western Sarawak, Borneo, Willdenowia 55 (1), pp. 259-269 : 264-267

Hanguana flavescens Hroneš & UvÍrová , sp. nov. – Fig. 4, 5.

Holotype: Malaysia, Sarawak, Kuching Division , Bau District , Jambusan, secondary forest south of Jibong Lake, 1.39933°N, 110.16475°E, c. 50 m a.s.l., 2 Feb 2024, Hroneš & Uvírová 2024/04 (SAR!).

Diagnosis — Hanguana flavescens is similar to H. exultans Siti Nurfazilah & al. but differs by pseudopetioles accounting for c. 1/4 of entire leaf length (vs c. 1/2 of entire leaf length in H. exultans ), leaf blade abaxially distinctly and evenly white floccose (vs somewhat floccose, soon becoming glabrescent), stigma depressed, 1.5–2 mm in diam. (vs conspicuously raised, c. 1.2 mm in diam.) and stigmatic lobes connate basally (vs free).

Description — Herbaceous, dioecious, solitary mesophyte c. 0.8 m tall. Rhizome ascending, c. 4 cm wide, densely covered by rotting remnants of sheaths; stolons absent. Stem terete, very short, c. 15 cm long, to 2 cm in diam., fully covered by leaf sheaths when young, basally ascending to erect, densely covered by rotting remnants of leaf sheaths with age, terminally with a crown of up to 24 leaves. Leaves 60–80 cm long, spreading then arching, bases imbricate with hyaline margins (young leaves), turning brown and erose-marcescent with age; pseudopetiole c. 15 cm long, 0.8–1 cm wide, accounting for c. 1/4 of entire leaf length, rounded channelled with sharp margins, basally densely greyish white floccose, becoming sparsely so apically; leaf blade 50–60 × 9–12 cm, narrowly elliptic to narrowly elliptic-ovate, base attenuate, tip long narrowly attenuate with apicule to 5 mm long, leathery, flat to slightly undulate on margins, adaxially dark green with somewhat indiscernible, greyish green to blackish green, transverse variegation, almost glabrous, abaxially light greyish green, evenly white floccose; midrib weakly impressed, pale whitish green adaxially, rounded raised, light green, sparsely white floccose and shiny abaxially; secondary veins distinct and slightly raised adaxially. Male inflorescence not observed, female inflorescence not observed. Infructescence suberect, consisting of up to 5 partial, whorled, alternate-secund, spiciform infructescences ascending at an angle of 80°–90°, plus a terminal spike; peduncle and rachis together to 60 cm tall, pale green when fresh, peduncle basally papillose, apically white floccose, visible portion of peduncle to 25 cm long; sterile bract 1 per peduncle, foliaceous, persistent, ovate to ovate-lanceolate, remotely undulate on margins, long apiculate, with a basal claw, to 40 cm (incl. c. 3 cm long claw/pseudopetiole) × c. 10 cm; bracts subtending lower partial infructescences similar to sterile bracts, diminishing in size and becoming narrowly triangular distally along infructescence, fully reduced in uppermost partial infructescences; bract supporting most basal partial infructescence c. 18 × 4 cm (incl. c. 2 cm long claw), all bracts of same colour as leaves, with sparse, evenly distributed, white hairs adaxially, densely whitish floccose abaxially; partial infructescences each consisting of up to 8 branches at basal levels (gradually fewer with up to 3 branches toward apex of infructescence), branches arising simultaneously from axil of subtending bract, 2–4 mm in diam., unbranched or with up to 3 branches, to 12 cm long, with up to 20 fruits each. Female flowers scattered, solitary, sessile, all with an associated minute bracteole; perianth consisting of 6 tepals in 2 whorls tightly clasping ovary/fruit in fresh material, all tepals with prominent, bulbous thickening at base (more prominent in outer whorl), light green, margin 0.1–0.2 mm wide, hyaline translucent white (turning brown with age); outer tepals broadly ovate, 1.3–2.2 mm long, c. 2 mm wide, connate at base (only to c. 0.6 mm), sparsely hairy at margins; inner tepals broadly orbicular, c. 2.5 mm long, 2.5–3 mm wide, basally imbricate but free, glabrous; staminodes 6, in 2 whorls, whitish green to brownish green, linear, outer staminodes c. 0.3 mm long, c. 0.1 mm wide at base, inner staminodes longer, 0.8–1 mm long, c. 0.3 mm wide at base, each basally sheathed with broadly orbicular, semicircular staminodial scale, 0.7–0.8 mm long, 0.8–0.9 mm wide, brown with irregular (usually bilobed), translucent margin. Stigma slightly sunken into fruit, 3-lobed (trefoil-like), 1.5–2 mm in diam., each lobe 0.7–1 mm long (fruiting material), elliptic with rounded apex, lobes connate basally, dark brown at fruiting stage, positioned usually at 130°–160° in ripe fruit. Fruit globose to shortly ellipsoid, slightly ventricose, depressed around stigma, c. 7.5 mm long, c. 7.9 mm in diam., c. 8.5 mm in ventricose diam., creamy white to yellowish white, finally ripening black; pulp 1–3 mm thick, yellowish white, fairly hard. Seed 1 or 2 per fruit, c. 5.5 × 2.5 mm, brown, bowl-shaped, with slightly incurved margins, deeply excavated, with large, incurved appendage positioned on distal part of rim, c. 2 mm long, 2–2.5 mm wide, externally with pointy projection at outer surface, cavity filled with placental tissue.

Distribution and habitat — So far known only from three localities in the vicinity of Bau town in Bau District, Kuching Division, western Sarawak. Except for two populations vouchered by herbarium specimens, we encountered and photographed a third population on the Bronang trail near Kampung Segong, north of Bau (1.5566667N, 110.1661111E). The species was found in primary or secondary forests on limestone and sandstone, usually in semi-shady and drier places on slopes, at altitudes of c. 50 m a.s.l.

Conservation status — Hanguana flavescens is endemic to Borneo and it is known from three locations (sensu IUCN 2024) in western Sarawak. The current extent of occurrence ( EOO) is estimated as c. 95 km 2 and the area of occupancy ( AOO) is c. 12 km 2. Although the species is apparently able to grow also in disturbed secondary forests, none of its known populations is located in a protected area. Because we expect further decline in the quality of the habitat, H. flavescens is assigned a preliminary conservation status of EN B1ab(iii)+2ab(iii) according to the IUCN Red List categories and criteria ( IUCN 2024).

Etymology — The Latin adjectival epithet flavescens means turning yellowish or pale yellow and refers to the colour of the fruits.

Additional specimen seen — MALAYSIA, SARAWAK, KUCHING DIVISION, BAU DISTRICT: Bau , Gg. Poing, 13 May 2002, D. Malcolm & al. SBC 1560 (SING 0203928) .