Polyalthia acuminatissima Wiya, Damth. & Chaowasku, 2025

Wiya, Chattida, Damthongdee, Anissara, Chanthamrong, Kithisak, Ue-Aree, Phasit & Chaowasku, Tanawat, 2025, Uncovering five new species of Polyalthia (Annonaceae, Miliuseae) from Thailand: molecular and morphological congruence, European Journal of Taxonomy 1022, pp. 243-276 : 258-261

Polyalthia acuminatissima Wiya, Damth. & Chaowasku sp. nov.

urn:lsid:ipni.org:names:77365547-1

Figs 1 , 8–9 , 12 ; Table 3

Diagnosis

Morphologically most similar to P. chantaranothaii and P. esanensis sp. nov., but principally differs from the two by different combinations of features (indumentum on young twigs, leaf texture, length of leaf acumen and outer petal length) as shown in Table 3 .

Etymology

The specific epithet refers to the usually distinctly elongated leaf apex.

Type material

Holotype

THAILAND • Nakhon Phanom Province, Ban Phaeng District, Phai Lom Subdistrict ; May 2022; fl., fr.; Chaowasku 231; holotype: CMUB [ CMUB004001001 ]; isotypes: BK, CMUB, PBM, QBG.

Paratype

THAILAND • Nakhon Phanom Province, Ban Phaeng District, Phu Langka National Park ; 17°57′00″ N, 104°09′44″ E; elev. 150 m; 25 Aug. 2001; fr.; Pooma et al. 2617; L .

Description

Treelets 1–2 m tall; young twigs puberulous intermixed with pilose, hairs appressed and erect. Petiole 1.5–4.0 mm long, puberulous with mostly appressed hairs, slightly grooved above; leaf blade chartaceous-subcoriaceous, narrowly elliptic to narrowly elliptic-obovate, rarely narrowly obovate, 12.3–20.2 × 2.3– 4.8 cm, glabrous above, puberulous with appressed hairs below, base obtuse-subcordate to obtuse, apex ± caudate-acuminate [acumen (12.0–)16.0–26.0 mm long] to acute-acuminate; midrib slightly sunken above, glabrous, raised below, puberulous with appressed hairs; secondary veins 10–16 per side, rather distinct below, angle with midrib 45°–70° (at middle part of leaf blade). Inflorescences 1- to 4-flowered, terminal (developing to internodal or ±leaf-opposed); peduncle and rachis (when present) inconspicuous; pedicel 4.5–11.0 mm long, puberulous intermixed with pilose, hairs mostly appressed, bearing 1 ovate-triangular bract. Sepals free to nearly half-connate, broadly ovate to ± transversely ovate-triangular, 2.2–3.5 × 2.8–3.5 mm, outside and margin puberulous-tomentose with appressed hairs, sparser at basal half, inside glabrous. Outer petals ovate to ovate-triangular, 4.5–5.5 × 2.2–3.2 mm, outside puberulous with appressed hairs, margin puberulous with appressed and erect hairs, inside glabrous, apex acute to acute-obtuse; inner petals ±pale yellow in vivo at maturity, 10.4–11.0 × 3.2–4.0 mm, (narrowly) ovate to (narrowly) ovate-elliptic, outside and margin puberulous with mostly appressed hairs, inside glabrous to almost glabrous, apex acute-obtuse to obtuse. Stamens 67–75 per flower, 1.3–1.6 mm long, connective apex truncate, covering thecae. Carpels 4–11 per flower, 2.0– 2.5 mm long; stigmas ellipsoid-obovoid to obovoid; ovaries tomentose with appressed hairs; ovule(s) 1 (rarely 2) per ovary, basal when containing 1 ovule and lateral when containing 2 ovules. Torus elevated, flat-topped. Each fruit consisting of up to 10 monocarps which are subglobose to subglobose-ellipsoid, 5.5–8.0 × 4.5–6.5 mm, smooth and shortpuberulous with mostly appressed hairs, apex short-apiculate, stipe 4.0–6.0 mm long, always attached obliquely to monocarps, indumentum similar to that of monocarps but a bit denser; fruiting pedicel to 11.0 mm long. Seed(s) 1 (rarely 2) per monocarp, ± subglobose (but flattened on one side when there are two seeds in a monocarp), ca 6.5 × 5.5 mm.

Habitat and phenology

The new species occurs in dry evergreen forests. The elevation is 150– 180 m. Flowering material was collected in May. Fruiting material was collected in May and August.

Distribution

Nakhon Phanom Province, northeastern Thailand.

Preliminary conservation assessment

Data Deficient (DD).

Figures

Fig. 1. Phylogram derived from Bayesian inference, with support values indicated: SR (maximum parsimony symmetric resampling values) / BS (maximum likelihood bootstrap values) / PP (posterior probabilities). ** = <50%. New species in bold. Scale bar unit: substitutions per site.

Fig. 8. Polyalthia acuminatissima Wiya, Damth. & Chaowasku sp. nov. A. Flower, side view. B. Flower, bottom view. C. Flower with one inner petal removed, side view. D. Adaxial side of outer (left) and inner (right) petals. E. Flower with petals and stamens removed, side view, showing carpels on torus.F. Flower with petals, stamens and carpels removed, top view. G. Carpel. H. Stamen: adaxial (left) and abaxial (right) sides. I. Monocarps. All from Chaowasku 231 (CMUB).

Fig. 9. Holotype of Polyalthia acuminatissima Wiya, Damth. & Chaowasku sp. nov. (Chaowasku 231; CMUB004001001).

Fig. 12. Distribution of Polyalthia chiangmaica Wiya, Damth. & Chaowasku sp. nov. (■), P. miliusifolia Wiya, Chanthamrong & Chaowasku sp. nov. (★), P. esanensis Wiya, Damth. & Chaowasku sp. nov. (●), P. acuminatissima Wiya, Damth. & Chaowasku sp. nov. (▲) and P. maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. (★). Note that (★) indicates a shared locality of both species.