Lanonia centralis Henderson & Bacon 2011

4. Lanonia centralis (Henderson, Ninh Khac Ban & Nguyễn Quốc Dựng) Henderson & Bacon (2011: 890).

Licuala centralis Henderson, Ninh Khac Ban & Nguyễn Qu ốc Dựng (2008: 148). Type:— VIETNAM. Da Nang City, Hoa Vang District, Ba Na-Nui Chua Nature Reserve, road to summit, 16°00’N 108°02’E, ca. 350 m, 19 April 2007, A. Henderson, Nguyễn Qu ốc Dựng, Nguyen Canh & Le Van Bo 3299 (holotype HN!, isotypes K!, NY!).

Stems 2.0(1.0–2.0) m long, 3.0(2.0–3.0) cm diameter, clustered, rarely solitary. Leaves 12(9–15) per stem; ligules 11.0(9.0–14.0) cm long, soon disintegrating into fibers; sheaths and proximalmost part of petioles with scattered, brown scales; petioles 111.7(81.0–200.0) cm long, 0.5(0.4–0.7) cm wide at the apex; petiole thorns usually poorly developed, brown or black, more or less regularly arranged on proximalmost part of petiole; hastulas raised, triangular, infolded; leaf blades 84.0(63.0–99.0) cm wide; costas 3.0(1.6–4.5) cm long, triangular, with a pulvinus at the apex abaxially, with the numerous segments free almost to the base; segments 19(13–29) per leaf, not mottled, with minute, reddish-brown scales abaxially, with (on dried specimens) straight margins; middle segments 45.6(33.5–54.0) cm long, 6.2(4.5–9.3) cm wide at the apex; apices of middle segments with adaxial splits not much deeper than abaxial ones. Inflorescences 65.0 cm long; prophylls 18.3(13.8–22.0) cm long; peduncles 30.1(20.0–40.5) cm long; rachis bracts flattened, splitting apically and laterally, usually densely brown tomentose; rachillae not filiform nor thick and ribbed, densely covered with wooly, much branched, reddish-brown hairs; staminate rachises 23.3(18.0–28.5) cm long; staminate partial inflorescences 2–3, branched to 3 orders; staminate rachillae 11, 12.0(7.8–15.2) cm long, 1.5(1.2–2.0) mm diameter; staminate flowers 2.3(2.1–2.6) mm long; sepals not pedicellate at the base, not densely hairy; petals rounded at the apex; stamens with equal filaments and longer, rectangular anthers; filaments not elongate; pistillodes undivided; pistillate rachises 25.0(17.5–34.0) cm long; pistillate partial inflorescences 2–3, branched to 2–3 orders; pistillate rachillae on proximalmost partial inflorescence 8(5–12), 12.7(9.0–19.5) cm long, 1.7(1.1–2.5) mm diameter; pistillate flowers 2.8(2.5–3.0) mm long, with short styles; fruits 6.7(6.0–7.1) mm long, 6.7(6.0–7.1) mm diameter, globose, white, whitish, or dull yellow, with smooth surfaces; seeds with a curved basal intrusion.

Distribution and habitat:—Central Laos in Bolikhamsay province and central Vietnam in Ha Tinh, Quang Binh, Quang Nam, Quang Tri, and Thua Thien-Hue provinces and Da Nang City in lowland rainforest at 496(20–1,025) m elevation (Fig. 8).

Taxonomic notes:— Specimens determined as preliminary species Lanonia centralis were polymorphic for stem branching, segment margins, rachillae thickness, rachillae tomentum, and stamen type. Specimens were therefore split into two species such that each had a unique combination of variables (stem branching was treated as a trait), and these two were recognized as phylogenetic species L. centralis and L. kontumensis.

Lanonia centralis appears most similar to L. hainanensis from Hainan Island, China. It differs in its rachillae with dense, wooly, much branched, reddish-brown hairs (versus sparse, short, mostly simple, brownish hairs) and white (versus red) fruits.

Subspecific variation:— Lanonia centralis is one of the most widespread species and thus one of the most variable. Most variation is found in the southern part of the range. Three specimens (LX-VN 3099, Cuong 10, Henderson 3564) from Quang Nam have narrower segments but otherwise appear similar to other specimens of L. centralis. Further south, L. centralis is sympatric with three other species, L. batoensis, L. gialaiensis, and L. kontumensis. In particular, some specimens are similar to L. kontumensis in their narrow segments and there may be hybridization in this area.