Polyalthia maxwelliana Wiya, Chanthamrong & 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 : 261-265

Polyalthia maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov.

urn:lsid:ipni.org:names:77365548-1

Figs 1 , 10–12 ; Table 4

Diagnosis

Morphologically most similar to P. khaoyaiensis , but primarily differs from it in several traits (leaf texture, flowering pedicel length, inner petal shape and number of carpels per flower) as shown in Table 4 .

Etymology

The specific epithet honors James Franklin Maxwell (1945–2015), an extraordinary collector of Thai plants. Besides, he was the first curator and one of the founders of the herbarium CMUB.

Type material

Holotype THAILAND • Cult. in Nakhon Si Thammarat Province (originally from Chalae Subdistrict, Thong Pha Phum District, Kanchanaburi Province); Aug. 2020; fl.; Chanthamrong 73; holotype: CMUB [ CMUB004000801 ] ; isotype: QBG .

Description

Treelets 1.5–4 m tall; young twigs tomentose-villous with mostly erect hairs. Petiole 2.5–3.5 mm long, indumentum similar to that of young twigs, grooved or slightly so above; leaf blade subcoriaceous, elliptic, rarely elliptic-obovate, 13.0–22.0 × 4.1–6.1 cm, almost glabrous above, puberulous with appressed hairs below, base obtuse-subcordate to rounded-subcordate, apex caudate-acuminate (acumen 10.0–20.0 mm long), sometimes acute-acuminate, rarely acute-obtuse; midrib slightly sunken above, tomentose-villous with mostly erect hairs, raised below, puberulous with appressed and erect hairs; secondary veins 11–17 per side, distinct below, angle with midrib 50°–60° (at middle part of leaf blade). Inflorescences 1- or 2-flowered, terminal developing to ± leaf-opposed; peduncle inconspicuous; pedicel 13.0–15.0 mm long, ± velvety with appressed and erect hairs, bearing 1–2 bract(s), ± triangular. Sepals free, ± transversely ovate, 4.0–4.5 × 4.5–6.0 mm, outside and margin puberulous-tomentose with appressed and erect hairs, slightly denser on apex, inside glabrous to almost glabrous. Outer petals ovate, 6.8–7.8 × 4.2–5.2 mm, outside and margin tomentose with appressed hairs, inside glabrous, apex ±acute; inner petals yellow-orange in vivo at maturity, ± broadly ovate, 16.0–17.0 × 11.5–13.0 mm, outside puberulous-tomentose to tomentose, hairs appressed, margin tomentose with mostly appressed hairs, sparser on basal half, inside puberulous-tomentose with appressed hairs only near margin on apical half, remaining area glabrous, apex acute-obtuse. Stamens ca 151 per flower, 2.2–2.5 mm long, connective apex truncate, covering thecae. Carpels ca 63 per flower, 4.2–4.6 mm long; stigmas elongated-obovoid; ovaries tomentose-villous 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. Fruit unknown.

Habitat (at original locality) and phenology

The new species occurs in dry evergreen forests with bamboos, near a stream. The elevation (at original locality) is ca 450 m. Flowering material was collected in August.

Distribution

Kanchanaburi Province, southwestern 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. 10. Polyalthia maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. A. Flower, side view. B. Flower with one inner petal removed, side view. C. Flower, bottom view. D. Adaxial (left) and abaxial (right) sides of inner petal. 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 Chanthamrong 73 (CMUB).

Fig. 11. Holotype of Polyalthia maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. (Chanthamrong 73; CMUB004000801).

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.