Polyalthia esanensis 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 : 255-258

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

urn:lsid:ipni.org:names:77365546-1

Figs 1 , 6–7 , 12 ; Table 3

Diagnosis

Morphologically most similar to P. chantaranothaii and P. acuminatissima sp. nov. (another new species described below; = P. evecta -4), but can be chiefly distinguished from the two by different combinations of traits (indumentum on young twigs, leaf texture, length of leaf acumen and outer petal length) as shown in Table 3 .

Etymology

Named after ʻEsanʼ, an informal name for eastern and northeastern regions of Thailand where this species occurs.

Type material

Holotype

THAILAND • Amnat Charoen Province, Chanuman District, Khok Kong Subdistrict ; Jul. 2019; fl.; Chaowasku 225; holotype: CMUB [ CMUB004001101 ]; isotype: QBG.

Paratypes

THAILAND • Udon Thani Province, Nong Saeng District, Thap Kung Subdistrict ; Jul. 2019; fl., fr.; Chaowasku 226; QBG • same data as for holotype; May 2022; fl., young fr.; Chaowasku 230; QBG .

Description

Treelets ca 1.5 m tall; young twigs tomentose-villous to villous, hairs erect only or appressed and erect. Petiole 2.0–4.0 mm long, velvety with mostly erect hairs, slightly grooved above; leaf blade chartaceous, elliptic to obovate, sometimes narrowly obovate, 7.9–15.8 × 2.5–4.3 cm, puberulous with appressed hairs above, puberulous-tomentose intermixed with pilose below, hairs appressed only or appressed and erect, base obtuse-subcordate to rounded-subcordate, rarely obtuse, apex caudately short-acuminate (acumen 6.0–9.0 mm) to acute-acuminate, rarely acute to obtuse; midrib slightly sunken to flat above, tomentose-villous with erect hairs, raised below, velvety with appressed and erect hairs; secondary veins 8–13 per side, rather distinct below, angle with midrib 50°–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 5.0–11.0 mm long, velvety with appressed and erect hairs, bearing 1 ovate-triangular bract. Sepals free, broadly ovate, 2.5–3.0 × 2.6–3.1 mm, outside and margin velvety with appressed and erect hairs, inside glabrous. Outer petals ovate to ovate-triangular, 5.5–5.8 × 3.0– 3.2 mm, outside tomentose with mostly appressed hairs, margin tomentose with appressed and erect hairs, inside glabrous, apex acute; inner petals ± pale yellow in vivo at maturity, ovate to ovate-elliptic, 9.7–10.5 × 3.8–4.2 mm, outside and margin tomentose with mostly appressed hairs, inside almost glabrous, apex ±acute. Stamens 60–84 per flower, 1.2–1.6 mm long, connective apex truncate, covering thecae. Carpels 7–13 per flower, 1.8–2.0 mm long; stigmas ± obovoid; ovaries tomentose with appressed hairs; ovule 1 per ovary, basal. Torus depressed subglobose. Each fruit consisting of up to 6 monocarps which are ±subglobose, 5.5–7.0 × 5.3–6.0 mm, smooth and puberulous with mostly appressed hairs, apex not apiculate, stipe 5.5–7.0 mm long, often slightly obliquely attached to monocarps, indumentum similar to that of monocarps but a bit denser; fruiting pedicel ca 17.0 mm long. Seed 1 per monocarp, subglobose, ca 6.0 × 5.5 mm.

Habitat and phenology

The new species occurs in partially disturbed deciduous forests, near a stream. The elevation is 150– 570 m. Flowering and fruiting material was collected in May and July.

Distribution

Eastern and 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. 6. Polyalthia esanensis 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. All from Chaowasku 230 (QBG).

Fig. 7. Holotype of Polyalthia esanensis Wiya, Damth. & Chaowasku sp. nov. (Chaowasku 225; CMUB004001101).

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.