Uncovering five new species of Polyalthia (Annonaceae, Miliuseae) from Thailand: molecular and morphological congruence

243 European Journal of Taxonomy 1022: 243–276 https://doi.org/10.5852/ejt.2025.1022.3093 europeanjournaloftaxonomy.eu ISSN 2118-9773 2025 · Wiya C. et al. This work is licensed under a Creative Commons Attribution License (CC BY 4.0) Received: 24 January 2024 • Accepted: 23 April 2025 • Published: 14 October 2025 Topic editor: Frederik Leliaert • Desk editor: Radka Rosenbaumová Research article Uncovering five new species of Polyalthia (Annonaceae, Miliuseae) from Thailand: molecular and morphological congruence Chattida WIYA 1 , Anissara DAMTHONGDEE 2 , Kithisak CHANTHAMRONG 3 , Phasit UE-AREE 4 & Tanawat CHAOWASKU 5,* 1,2,4,5 Herbarium, Department of Biology, Faculty of Science, Chiang Mai University, 239 Huay Kaew Rd., Chiang Mai 50200, Thailand. 1 Current address: Queen Sirikit Botanic Garden, The Botanical Garden Organization, 100 Moo 9, Mae Rim, Chiang Mai 50180, Thailand. 3 Independent Research Group on Plant Diversity in Thailand, 13 Moo 1, Khaonoi, Sichon, Nakhon Si Thammarat 80120, Thailand. 4 Current address: Forest Herbarium, Department of National Parks, Wildlife and Plant Conservation, 61 Phahonyothin Rd., Bangkok 10900, Thailand. * Corresponding author: [email protected] 1 Email: [email protected] 2 Email: [email protected] 3 Email: [email protected] 4 Email: [email protected] Abstract. Based on molecular phylogenetic analyses using seven plastid DNA markers (matK, rbcL, ndhF and ycf1 exons; trnL intron; psbA-trnH and trnL-trnF intergenic spacers) and detailed morphological investigations, five new species of Polyalthia Blume (Annonaceae Juss.) from Thailand are recognized, described and illustrated. These species are: P. acuminatissima Wiya, Damth. & Chaowasku sp. nov. (from Nakhon Phanom Province, northeastern region), P. esanensis Wiya, Damth. & Chaowasku sp. nov. (from eastern and northeastern regions), P. chiangmaica Wiya, Damth. & Chaowasku sp. nov. (from Chiang Mai Province, northern region), P. maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. and P. miliusifolia Wiya, Chanthamrong & Chaowasku sp. nov. (both from Kanchanaburi Province, southwestern region). All five species belong to one of the three major clades within the genus. Three of them (P. acuminatissima, P. esanensis and P. chiangmaica) were previously misidentified as P. evecta (Pierre) Finet & Gagnep., which is polyphyletic. Comparisons with their phylogenetically related or morphologically similar species are provided and a key to the species of this major clade occurring in Thailand is included. The conservation status of all five new species is provisionally assessed as Data Deficient. Keywords. Magnoliids, Malmeoideae, molecular phylogeny, systematics, taxonomy. European Journal of Taxonomy 1022: 243–276 (2025) 244 Wiya C., Damthongdee A., Chanthamrong K., Ue-aree P. & Chaowasku T. 2025. Uncovering five new species of Polyalthia (Annonaceae, Miliuseae) from Thailand: molecular and morphological congruence. European Journal of Taxonomy 1022: 243–276. https://doi.org/10.5852/ejt.2025.1022.3093 Introduction The genus Polyalthia Blume (Blume 1830) belongs to Annonaceae Juss., a large angiosperm family prominent in lowland rainforests, comprising ca 108 genera (Damthongdee et al. 2024) and about 2550 species (Couvreur et al. 2022). It is classified within a recently established subtribe Popowiinae Chaowasku & D.C.Thomas of Miliuseae Hook.f. & Thomson, the largest tribe in the subfamily Malmeoideae Chatrou, Pirie, Erkens & Couvreur (Nge et al. 2024). Historically, Polyalthia has been taxonomically problematic due to the lack of distinct morphological diagnostic features. However, molecular phylogenetics has helped resolve these complexities, leading to generic realignments across the subfamily (Mols et al. 2008; Saunders et al. 2011; Xue et al. 2011, 2012, 2014, 2016, 2020; Chaowasku et al. 2012, 2015, 2018b; Tang et al. 2013). In its narrowly defined sense, Polyalthia consists of approximately 99 species distributed across tropical Asia and Oceania (Turner 2018; Shailajakumari et al. 2019; Bunchalee et al. 2019, 2021a, 2021b, 2025; Xue et al. 2020; Wiya & Chaowasku 2021). Members of the genus are shrubs, treelets or trees characterized by a combination of the following traits: (1) leaf blades with a usually reticulate tertiary venation, (2) a usually asymmetrical subcordate to cordate leaf base, (3) 1–8 ovule(s) per ovary and (4) seeds with ± spiniform endosperm ruminations (Wiya & Chaowasku 2021; Bunchalee 2022). Phylogenetically, Polyalthia is sister to Popowia Endl. (Endlicher 1839) and consists of three major clades (Chaowasku et al. 2012). One of these clades includes Polyalthia suberosa (Roxb.) Thwaites (Thwaites 1864; basionym: Roxburgh 1795) and related species, and has previously been referred to as the P. suberosa clade (Wiya & Chaowasku 2021). Members of the P. suberosa clade exhibit rather small flowers and free petals, which are (rather) thick and fleshy in inner petals (sometimes also outer petals); note that petals of both whorls in most species are unequal, with the outer petals being smaller and sometimes ± sepaloid (Chaowasku et al. 2014; Wiya & Chaowasku 2021). Among the species of Polyalthia reported for Thailand, about 11 belong to the P. suberosa clade (Wiya & Chaowasku 2021; Bunchalee 2022; Bunchalee et al. 2025). However, a particular species, P. evecta (Pierre) Finet & Gagnep. (Finet & Gagnepain 1906; basionym: Pierre 1881), is morphologically heterogeneous regarding indumentum on young twigs, leaf texture, length of leaf acumen, flowering pedicel and outer petal length, ratio of outer petal to inner petal length and number of carpels per flower. In this study, we aim to clarify the taxonomy of P. evecta as well as some unidentified gatherings from Thailand by reconstructing molecular phylogenetic hypotheses for the genus Polyalthia, with emphasis on the species in the P. suberosa clade and inclusion of multiple accessions per species where possible. Material and methods Molecular phylogenetic analyses Thirty-eight accessions comprised the ingroup: 37 of Polyalthia (representing 28 species plus five unidentifiable accessions from Thailand) and one of Popowia hirta Miq. (Miquel 1865). Mitrephora alba Ridl. (Ridley 1915), Monocarpia maingayi (Hook.f. & Thomson) I.M.Turner (Turner 2012a; basionym: Hooker & Thomson 1872) and Orophea sp. were assigned as outgroups. Voucher information and GenBank accession numbers of all accessions are indicated in Appendix 1. Seven plastid DNA regions (matK, rbcL, ndhF and ycf1 exons; trnL intron; psbA-trnH and trnL-trnF intergenic spacers) were used. Nineteen accessions were newly sequenced for this study (Appendix 1). The methods for DNA extraction, amplification and sequencing used in the present study, including primer information, WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 245 followed Chaowasku et al. (2018a, 2018b, 2020). Sequences were edited using the Staden package (Staden et al. 2000) and, together with GenBank sequences, the data matrix was aligned by Multiple Sequence Comparison by Log-Expectation (MUSCLE; Edgar 2004) in MEGA11 (with default settings; Tamura et al. 2021). The aligned data matrix was subsequently manually checked and realigned where necessary using the similarity criterion (Simmons 2004). In some psbA-trnH intergenic spacer sequences, there was an inversion of 15 continuous nucleotides and this was reversed complementarily to be comparable to the remaining sequences, following Pirie et al. (2006). In total, 6915 nucleotide plus four binary-coded indel characters were included. The simple method for indel coding of Simmons & Ochoterena (2000) was used, with the emphasis on less homoplastic and non-autapomorphic indel structures. Maximum parsimony analysis was performed in TNT ver. 1.5 (Goloboff & Catalano 2016). All characters were equally weighted and unordered. The setting concerning collapsing rules was set to ʻmax. length = 0ʼ. Incongruence among plastid DNA regions was evaluated by analyzing each region individually to detect if there was any significant topological conflict (e.g., Wiens 1998). Most parsimonious trees were generated by a heuristic search of the combined data, with 9000 replicates of random sequence addition, saving 10 trees per replicate and using the tree bisection and reconnection (TBR) branch-swapping algorithm. Clade support was measured by symmetric resampling (SR; Goloboff et al. 2003), with default change probability (P = 33). Two hundred thousand replicates were run, each with four replicates of random sequence addition, saving four trees per replicate. A clade with SR ≥ 85%, 70–84% or 50–69% was considered strongly, moderately or weakly supported, respectively. Maximum likelihood analysis was carried out in IQ-TREE ver. 2.1.2 (Minh et al. 2020) under partition models (Chernomor et al. 2016) employed with the ʻ-pʼ command, whereas a Bayesian Markov chain Monte Carlo (MCMC; Yang & Rannala 1997) phylogenetic analysis was conducted in MrBayes ver. 3.2.7a (Ronquist et al. 2012). Both methods of phylogenetic reconstruction were analyzed via the CIPRES Science Gateway ver. 3.3 (Miller et al. 2010). The aligned data matrix was divided into six partitions based on DNA-region identity (the trnL intron and adjacent trnL-trnF intergenic spacer were combined into a single partition [= trnL-F]). The most suitable model of sequence evolution for each DNA partition was selected using the Akaike Information Criterion (AIC; Akaike 1974) scores calculated in jModelTest ver. 2.1.10 (Darriba et al. 2012), with the following selections: +F, +G (nCat 4), ML optimized (base tree for likelihood calculations) and Best (base tree search). The General Time Reversible (GTR; Tavaré 1986) substitution model with a gamma distribution for among-site rate variation was selected for matK, ndhF and psbA-trnH partitions, whereas the Hasegawa-Kishino-Yano (HKY; Hasegawa et al. 1985) substitution model was chosen for trnL-F (= trnL intron + trnL-trnF intergenic spacer) and HKY substitution model with a gamma distribution for among-site rate variation was chosen for the remaining partitions (rbcL and ycf1 exons). In the maximum likelihood analysis, the model ʻJC2+FQ+ASCʼ was selected using the corrected AIC scores for the binary indel partition. Clade support was assessed by a non-parametric bootstrap resampling (BS; Felsenstein 1985) with 2000 replicates. A clade with BS ≥ 85%, 70–84% or 50–69% was considered strongly, moderately or weakly supported, respectively. In the Bayesian analysis, the ʻcoding=variableʼ setting was assigned to the binary indel partition, which was implemented under a simple F81-like model without a gamma distribution for among-site rate variation. Four independent runs, each with four MCMC chains, were simultaneously performed; each run was set for 10 million generations. The default prior settings were used except for the prior parameter of rate multiplier (ʻrateprʼ [=variable]). The temperature parameter was set to 0.08. Trees and all parameter values were sampled every 1000th generation. Convergence was assessed by checking the standard deviation of split frequencies of the runs with values < 0.01 interpreted as indicative of a good convergence and by checking for adequate effective sample sizes (ESS > 200) using Tracer ver. 1.7.1 (Rambaut et al. 2018). The first 25% of all trees sampled were removed as burn-in and the 50% majority-rule consensus tree was produced from the remaining trees. A clade with posterior probabilities (PP) ≥ 0.95, 0.9–0.94 or 0.5–0.89 was considered strongly supported, weakly supported or unsupported, respectively. European Journal of Taxonomy 1022: 243–276 (2025) 246 Morphological study Morphological data of relevant species of Polyalthia were derived from literature (Pierre 1881; Finet & Gagnepain 1906; Ridley 1912; Ast 1938; Jovet-Ast 1940; Bân 2000; Khumchompoo & Thongpukdee 2005; Bunchalee et al. 2019, 2021b, 2025; Wiya & Chaowasku 2021; Bunchalee 2022), personal observations based on their type specimens at the herbaria BK, BM, CAL, K, L and P (see Appendix 2) and other specimens [Chaowasku 234 (QBG): P. intermedia (Pierre) Bân (Bân 2000; basionym: Pierre 1881); Sichaikhan 9 (QBG): P. khaosokensis Bunchalee, Leerat. & Sinbumr. (Bunchalee et al. 2025)]. Acronyms of herbaria follow Index Herbariorum (Thiers continuously updated). Some floral organs (sepals, petals, stamens and carpels) of the specimens studied were observed and measured using spirit material. The indumentum terminology used followed Hewson (1988). Results Phylogenetic relationships and morphological comparisons The maximum parsimony analysis resulted in 21 650 most parsimonious trees with 586 steps. The consistency and retention indices (CI and RI) were 0.87 and 0.89, respectively. There was no strong topological conflict (SR ≥ 85%) in the analyses of each plastid DNA region. The phylogenetic results (Fig. 1) showed the monophyly for the ingroup (Popowia-Polyalthia) and for the genus Polyalthia, both with strong support (SR = 99%, BS = 100%, PP = 1). Three major clades (clades 1–3) in Polyalthia were recovered. The strongly supported (SR = 99%, BS = 100%, PP = 1) clade 1 was sister to the maximally supported clade 2 with strong support (SR = 87%, BS = 92%, PP = 1). A larger clade composed of clades 1 and 2 was sister to the strongly supported (SR = 93%, BS = 95%, PP = 1) clade 3, which included, among others, the recently described P. heliopetala Leerat. & Bunchalee (in Bunchalee et al. 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. WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 247 2021a) and Polyalthia sp. A. Clade 1 consisted of two accessions: P. stenopetala (Hook.f. & Thomson) Finet & Gagnep. (Finet & Gagnepain 1906; basionym: Hooker & Thomson 1855) and Polyalthia sp. B. The relationships in clades 2 and 3 were largely unresolved (Fig. 1). In clade 2, Polyalthia evecta-1, P. evecta-2, P. intermedia, P. suthepensis-1, P. suthepensis-2, P. khaoyaiensis Bunchalee & Chantar. (in Bunchalee et al. 2019) and Polyalthia sp. 1 were recovered in an unsupported to strongly supported (SR = 54%, BS < 50%, PP = 0.99) clade; in this clade, there was a trichotomy consisting of (1) a strongly supported (SR = 99%, BS = 99%, PP = 1) clade comprising P. evecta-1, P. evecta-2 and P. intermedia, with the first two accessions forming a strongly supported (SR = 89%, BS = 94%, PP = 1) clade, (2) a strongly supported (SR = 98%, BS = 99%, PP = 1) clade comprising two accessions of P. suthepensis Wiya & Chaowasku (Wiya & Chaowasku 2021) and (3) a weakly to strongly supported (SR = 64%, BS = 67%, PP = 1) clade composed of P. khaoyaiensis and Polyalthia sp. 1. Polyalthia evecta-3, Polyalthia sp. 2, P. evecta-4 and P. chantaranothaii Bunchalee & Chalermglin (in Bunchalee et al. 2021b) belonged to a moderately to strongly supported (SR = 75%, BS = 80%, PP = 1) clade; in this clade, P. evecta-3 and Polyalthia sp. 2 were sister to each other with moderate to strong support (SR = 84%, BS = 87%, PP = 1). A clade consisting of P. evecta-3 and Polyalthia sp. 2 formed a trichotomy with P. evecta-4 and P. chantaranothaii. Polyalthia suberosa, P. kanchanaburiana Khumch. & Thongp. (Khumchompoo & Thongpakdee 2005) and Polyalthia sp. 3 were retrieved in an unsupported (SR < 50%, BS < 50%, PP = 0.71) clade, with the first two accessions forming a strongly supported (SR = 99%, BS = 100%, PP = 1) clade. It is apparent that the polyphyletic P. evecta (Fig. 1) should be reclassified. Upon comparisons, P. evecta-2 (collected in Vietnam) morphologically corresponds well with the lectotype and isolectotypes of Unona evecta, the basionym of P. evecta, which were also collected in Vietnam; thus, it is considered as the true P. evecta. Polyalthia evecta-1 is sister to the true P. evecta, but the two are morphologically different in several features as shown in Table 1. Polyalthia evecta-1 also differs morphologically from P. intermedia (Table 1); therefore, it deserves recognition as a new species (P. chiangmaica sp. nov.), which is described below. Although Polyalthia sp. 1 is sister to P. khaoyaiensis, their morphology differs substantially (Table 2). Polyalthia sp. 1 is morphologically quite similar to P. minima Jovet-Ast (Jovet-Ast 1940) endemic to Vietnam, but differs from it in several traits as shown in Table 2. Consequently, it is described below as a new species (P. miliusifolia sp. nov.). Unfortunately, P. minima has not been included in the molecular phylogenetic inferences because the holotype (collected in 1930) is the only specimen available for this species. Polyalthia evecta-3 is sister to Polyalthia sp. 2; however, it is morphologically more similar to P. evecta-4 and P. chantaranothaii, both of which are also phylogenetically related to P. evecta-3 (Fig. 1). Table 3 shows their differences, as well as their differences from the true P. evecta, which is more distantly related (Fig. 1). Based on these findings, two new species (P. esanensis sp. nov. and P. acuminatissima sp. nov.) are warranted and described below. The phylogenetic affinities of Polyalthia sp. 3 are still uncertain (Fig. 1). It is morphologically most similar to P. khaoyaiensis, which is quite distantly related (Fig. 1). The two differ from each other in several features (Table 4). Hence, Polyalthia sp. 3 is described below as new to science (P. maxwelliana sp. nov.). Provisional conservation assessments Because each of the five new species is known from a limited number of gatherings collected from one or a few location(s), the conservation category Data Deficient (DD) (IUCN Standards and Petitions Committee 2024) is provisionally applied to all five new species. European Journal of Taxonomy 1022: 243–276 (2025) 248 Taxonomy Order Magnoliales Juss. ex Bercht. & J.Presl Family Annonaceae Juss., nom. cons. Tribe Miliuseae Hook.f. & Thomson Genus Polyalthia Blume Polyalthia chiangmaica Wiya, Damth. & Chaowasku sp. nov. urn:lsid:ipni.org:names:77365544-1 Figs 1–3, 12; Table 1 Diagnosis Morphologically most similar to P. evecta and P. intermedia but differs mainly from them by different combinations of features (flowering pedicel and outer petal length, ratio of outer petal to inner petal length and number of carpels per flower) as shown in Table 1. Etymology The specific epithet refers to Chiang Mai Province of northern Thailand where the new species occurs. Type material Holotype THAILAND • Chiang Mai Province, Chiang Dao District, Chiang Dao Subdistrict; Dec. 2021; fl., fr.; Chaowasku 229; holotype: CMUB [CMUB004001201]; isotypes: BK, CMUB, PBM, QBG. Paratype THAILAND • Chiang Mai Province, Chiang Dao District, Chiang Dao Subdistrict; Oct. 2022; fl., fr.; Chaowasku 232; QBG. Description Shrubs ca 6 m tall; young twigs tomentose-villous with appressed and erect hairs. Petiole 1.5–3.0 mm long, puberulous-pilose with mostly appressed hairs, slightly grooved above; leaf blade chartaceous, elliptic, rarely elliptic-obovate, 8.0–18.5 × 3.0–7.6 cm, glabrous above, puberulous with appressed hairs below, base obtuse to obtuse-subcordate, apex acute to acute-obtuse, rarely obtuse; midrib slightly sunken above, puberulous with erect hairs, raised below, puberulous with appressed hairs; secondary veins 9–14 per side, rather distinct below, angle with midrib 55°–70° (at middle part of leaf blade). Inflorescences 1to 4-flowered, terminal (developing to internodal); peduncle inconspicuous to 3 mm long; rachis ca 7 mm long when present, tomentose with appressed and erect hairs, with scars of fallen flowers; pedicel 6.5–8.0 mm long, puberulous intermixed with pilose, hairs appressed and erect, bearing 1 ovate-triangular bract. Sepals free, broadly ovate, 2.0–2.5 × 2.8–3.0 mm, outside and margin tomentose-villous with mostly appressed hairs, inside almost glabrous. Outer petals ovate to broadly ovate, 2.2–2.5 × 1.9–2.0 mm, outside tomentose with appressed hairs, margin tomentose with appressed and erect hairs, inside almost glabrous, apex ± acute; inner petals ± pale yellow-orange in vivo at maturity, elliptic-oblong, 7.5–8.2 × 4.5–5.0 mm, outside tomentose with appressed hairs, margin tomentose with appressed and erect hairs, inside glabrous, apex ± acute. Stamens ca 100 per flower, 1.3–1.5 mm long, connective apex truncate, covering thecae. Carpels 16–22 per flower, 1.7–1.9 mm long; stigmas obovoid; ovaries tomentose-villous with appressed hairs; ovule 1 per ovary, basal. Torus elevated, flat-topped. Each fruit consisting of up to 2 monocarps which are globose to subglobose, 6.0–7.5 × 6.0–6.5 mm, smooth and puberulous-tomentose with mostly appressed hairs, apex short-apiculate, stipe 2.0–5.5 mm long, sometimes slightly obliquely attached to monocarps, tomentose with appressed and erect hairs; fruiting pedicel to 20 mm long. Seed 1 per monocarp, subglobose, ca 6.3 × 5.8 mm. WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 249 Fig. 2. Polyalthia chiangmaica 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 229 (CMUB). European Journal of Taxonomy 1022: 243–276 (2025) 250 Fig. 3. Holotype of Polyalthia chiangmaica Wiya, Damth. & Chaowasku sp. nov. (Chaowasku 229; CMUB004001201). WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 251 Habitat and phenology The new species occurs in secondary forests adjacent to dry evergreen forests, near a stream. The elevation is ca 500 m. Flowering and fruiting material was collected in October and December. Distribution Chiang Mai Province, northern Thailand. Preliminary conservation assessment Data Deficient (DD). Polyalthia miliusifolia Wiya, Chanthamrong & Chaowasku sp. nov. urn:lsid:ipni.org:names:77365545-1 Figs 1, 4–5, 12; Table 2 Diagnosis Morphologically most similar to P. minima, but differs mainly from it in several features (indumentum on young twigs and lower leaf midrib, flowering pedicel length, outer petal shape and apex, number of carpels per flower and stigma shape) as shown in Table 2. Etymology The leaves of the new species look somewhat similar to those of certain species of Miliusa Lesch. ex A.DC. (de Candolle 1832), e.g., M. astiana Chaowasku & Kessler (Chaowasku & Kessler 2014), M. fragrans Chaowasku & Kessler (Chaowasku & Kessler 2013), M. fusca Pierre (Pierre 1881) and M. parvifolia (Kurz) Damth. & Chaowasku (Damthongdee & Chaowasku 2022; basionym: Kurz 1875); hence, its specific epithet. Type material Holotype THAILAND • Cult. in Nakhon Si Thammarat Province (originally from Chalae Subdistrict, Thong Pha Phum District, Kanchanaburi Province); Jul. 2022; fl.; Chanthamrong 74; holotype: CMUB [CMUB004000901]; isotypes: PBM, QBG. Paratypes THAILAND • same data as for holotype; Nov. 2020; fl.; Chaowasku 228; QBG • same data as for preceding; Nov. 2022; fl.; Chaowasku 233; QBG • same data as for preceding; Jul. 2023; fl.; Chanthamrong 75; QBG. Feature P. evecta-1 [= P. chiangmaica sp. nov.] P. evecta-2 [= true P. evecta]P. intermedia Pedicel length (mm; in flower) 6.5–8.0 (12.5–)15.0–30.0 13.0–28.0 Ratio of outer petal to inner petal length ca ⅓ ca ½ ca ½ Outer petal length (mm) 2.2–2.5 4.5–5.5 4.0–5.0(–6.5) Number of carpels per flower 16–22 (30–)40–60 6–20 Table 1. Morphological comparisons between Polyalthia evecta-1 [= P. chiangmaica Wiya, Damth. & Chaowasku sp. nov.], P. evecta-2 [= true P. evecta (Pierre) Finet & Gagnep.] and P. intermedia (Pierre) Bân. Data for the true P. evecta are from Pierre (1881) and personal observations; data for P. intermedia are from Pierre (1881), Bân (2000) and personal observations. European Journal of Taxonomy 1022: 243–276 (2025) 258 inconspicuous; pedicel 5.0–11.0 mm long, velvety with appressed and erect hairs, bearing 1 ovatetriangular 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). 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- WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 259 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). European Journal of Taxonomy 1022: 243–276 (2025) 260 Fig. 9. Holotype of Polyalthia acuminatissima Wiya, Damth. & Chaowasku sp. nov. (Chaowasku 231; CMUB004001001). WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 261 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 1to 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 ovatetriangular 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). 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. European Journal of Taxonomy 1022: 243–276 (2025) 262 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). WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 263 Fig. 11. Holotype of Polyalthia maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. (Chanthamrong 73; CMUB004000801). European Journal of Taxonomy 1022: 243–276 (2025) 264 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. WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 265 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 1or 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 yelloworange 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). Key to the species of Polyalthia in Thailand belonging to clade 2 1. Petals of both whorls subequal, (rather) thick and fleshy ................................................................. 2 – Petals of both whorls unequal, inner petals (rather) thick and fleshy, outer petals markedly smaller, thinner and less fleshy ....................................................................................................................... 3 Feature Polyalthia sp. 3 [= P. maxwelliana sp. nov.] P. khaoyaiensis Leaf texture subcoriaceous chartaceous Pedicel length (mm; in flower) 13.0–15.0 3.0–5.0 Inner petal shape ± broadly ovate ovate-elliptic to elliptic-oblong Number of carpels per flower ca 63 25‒35 Table 4. Morphological comparisons between Polyalthia sp. 3 [= P. maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov.] and P. khaoyaiensis Bunchalee & Chantar. Data for P. khaoyaiensis are from Bunchalee et al. (2019) and personal observations. European Journal of Taxonomy 1022: 243–276 (2025) 266 2. Flowers sessile or subsessile; carpels 6–12(–20) per flower; ovules 2 per ovary; monocarps dark red in vivo at maturity, sessile or subsessile ............................................................................................. .................... P. debilis (Pierre) Finet & Gagnep. (Finet & Gagnepain 1906; basionym: Pierre 1881) – Flowers pedicellate (pedicels 7.5–14.5 mm long); carpels 4 per flower; ovules 4–6 per ovary; monocarps yellow in vivo at maturity, stipitate (stipes 6.0–8.0 mm long) ......................................... ........................................................ P. suthepensis Wiya & Chaowasku (Wiya & Chaowasku 2021) 3. Carpels 1–2 per flower; ovules 3–8 per ovary ................................................ P. cambodica (Finet & Gagnep.) Wiya & Chaowasku (Wiya & Chaowasku 2021; basionym: Finet & Gagnepain 1906) – Carpels ≥ 3 per flower; ovule(s) usually 1–2 per ovary .................................................................... 4 4. Flowering pedicels < 13 mm long ..................................................................................................... 5 – Flowering pedicels ≥ 13 mm long ................................................................................................... 13 5. Flowering pedicels < 3 mm long; apex of outer petals obtuse to rounded; carpels 3 per flower ........ .............................................................. P. miliusifolia Wiya, Chanthamrong & Chaowasku sp. nov. – Flowering pedicels ≥ 3 mm long; apex of outer petals acute to acute-obtuse; carpels ≥ 4 per flower ........................................................................................................................................................... 6 6. Outer petals < 3 mm long .................................................................................................................. 7 – Outer petals ≥ 3 mm long .................................................................................................................. 8 7. Leaf apex acuminate; flowering pedicels 4.0–6.0 mm long; carpels 10–15 per flower ..................... ....................................... P. chantaranothaii Bunchalee & Chalermglin (in Bunchalee et al. 2021b) – Leaf apex usually acute to acute-obtuse; flowering pedicels 6.5–8.0 mm long; carpels 16–22 per flower .............................................................P. chiangmaica Wiya, Damth. & Chaowasku sp. nov. 8. Inner petals obovate ......... P. chalermglinii Bunchalee & D.M.Johnson (in Bunchalee et al. 2021b) – Inner petals (narrowly) ovate, (narrowly) ovate-elliptic or elliptic-oblong ...................................... 9 9. Carpels 25–35 per flower ............ P. khaoyaiensis Bunchalee & Chantar. (in Bunchalee et al. 2019) – Carpels < 25 per flower ................................................................................................................... 10 10. Base of inner petals usually orange-red in vivo at maturity; monocarps subsessile .......................... ......................... P. kanchanaburiana Khumch. & Thongp. (Khumchompoo & Thongpakdee 2005) – Base of inner petals ± pale yellow in vivo at maturity; monocarps stipitate (stipes 3.0–7.0 mm long) .................................................................................................................................................11 11. Outer petals 3.0–3.5 mm long; carpels 18–20 per flower ................................................................... .......................................... P. khaosokensis Bunchalee, Leerat. & Sinbumr. (Bunchalee et al. 2025) – Outer petals > 3.5 mm long; carpels < 18 per flower ...................................................................... 12 12. Young twigs sparsely hairy; leaf blades chartaceous-subcoriaceous, acumen (12.0–)16.0–26.0 mm long ........................................................... P. acuminatissima Wiya, Damth. & Chaowasku sp. nov. – Young twigs densely hairy; leaf blades chartaceous, acumen 6.0–9.0 mm long ................................ ............................................................................. P. esanensis Wiya, Damth. & Chaowasku sp. nov. 13. Leaf blades subcoriaceous, apex usually caudate-acuminate; carpels > 40 per flower ....................... ............................................................ P. maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. – Leaf blades chartaceous, apex acute to rounded-obtuse; carpels ≤ 40 per flower .......................... 14 WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 267 14. Bark (of large stems) corky; carpels 25–40 per flower; monocarps ± black in vivo at maturity ........ ......................................P. suberosa (Roxb.) Thwaites (Thwaites 1864; basionym: Roxburgh 1795) – Bark not corky; carpels < 25 per flower; monocarps red in vivo at maturity ..................................... ..........................................................P. intermedia (Pierre) Bân (Bân 2000; basionym: Pierre 1881) Discussion This study reveals that clades 1 (P. stenopetala clade) and 2 (P. suberosa clade) are sister groups. However, no morphological synapomorphies have been identified to unite these two clades. The petals of members of clade 1 exhibit a (much) higher length / width ratio than those of members of clade 2 and their inner petals are also thinner (Bunchalee 2022; C. Wiya & T. Chaowasku, pers. obs.), whereas the petals of members of clade 3 [P. subcordata (Blume) Blume (Blume 1830; basionym: Blume 1825) clade] are quite variable (van Heusden 1994; Jessup 2007; Bunchalee 2022; C. Wiya & T. Chaowasku, pers. obs.). Although the relationships of the species within clade 2 are mostly unresolved, they support the previous taxonomic action: disintegration of P. debilis (Pierre) Finet & Gagnep. (Finet & Gagnepain 1906; basionym: Pierre 1881), with new combinations made, e.g., P. cambodica (Finet & Gagnep.) Wiya & Chaowasku (Wiya & Chaowasku 2021; basionym: Finet & Gagnepain 1906), and establishment of a replacement name (P. suthepensis Wiya & Chaowasku) (Wiya & Chaowasku 2021). As a result of the taxonomic clarification of the P. evecta complex presented in this study, it appears that the true P. evecta may not occur in Thailand. Further field explorations in Thai areas closest to the type locality of this species are necessary to confirm its presence or absence. Regarding Miliusa concinna Ridl. (Ridley 1920), which was originally described from specimens collected in Siam (now Thailand) and has been considered as a heterotypic synonym of P. evecta (Turner 2012b, 2018), its morphology more closely resembles that of P. intermedia, especially in the number of carpels per flower (Ridley 1920; Table 1); elucidating the phylogenetic affinities of M. concinna is indispensable for the determination of its taxonomic status. It should be noted that, based on comparisons of relevant type specimens, P.parviflora Ridl. (Ridley 1912), which is well known in Thailand and Peninsular Malaysia, and P. debilis (the lectotype and isolectotypes of Unona debilis, the basionym of P. debilis, were collected in Vietnam; Turner 2018) are morphologically indistinguishable; thus, we consider them to be conspecific herein, awaiting further phylogenetic validation. Regarding Polyalthia sp. 2, only fruiting material is available. When compared with its sister (P. evecta-3 [= P. esanensis sp. nov.]), there are morphological differences, i.e., the monocarps are sessile (vs stipitate) and larger in Polyalthia sp. 2. It is morphologically more similar to P. cambodica. Flowering material is nevertheless needed before any taxonomic conclusion could be made. The recently described P. heliopetala is shown for the first time to belong to clade 3 (Fig. 1). Additionally, there are two potentially undescribed species from Thailand (Fig. 1: Polyalthia sp. A belonging to clade 3 and Polyalthia sp. B belonging to clade 1), but current material is insufficient for formal description. Acknowledgments We thank the BK, BM, CAL, CMUB, K, L, P, PBM and QBG herbaria for the specimens studied. Chanwut Saengpho helped with the manuscript preparation. Abdulromea Baka, Aroon Sinbumroong, Isma-ael Sama-ae, Pornthawat Chalermwong and Suhibukree Samae provided useful material for molecular phylogenetic inferences. Hathaichanok Jongsook provided photographs of the holotype of P. chantaranothaii at BK. Partial support was from Chiang Mai University. European Journal of Taxonomy 1022: 243–276 (2025) 274 Polyalthia johnsonii: Australia, Ford AF 3625 (CNS); JX544826, JX544840, JX544810, PV469173*, JX544801, JX544819. Polyalthia kanchanaburiana: Thailand, Chanthamrong 77 (QBG); PV469097*, PV469116*, PV469135*, PV469154*, PV469174*, PV469193*. Polyalthia khaoyaiensis: Thailand, Chanthamrong 78 (QBG); PV469101*, PV469120*, PV469139*, PV469158*, PV469178*, PV469197*. Polyalthia lateritia: Thailand, Chanthamrong 52 (QBG); PV469113*, PV469132*, PV469151*, PV469170*, PV469190*, PV469209*. Polyalthia longirostris: New Guinea, Takeuchi & Ama 15656 (L); AY518826, ---, ---, AY318979, AY319091, ---. Polyalthia maxwelliana [= Polyalthia sp. 3]: Thailand, Chanthamrong 73 (CMUB); PV469098*, PV469117*, PV469136*, PV469155*, PV469175*, PV469194*. Polyalthia miliusifolia [= Polyalthia sp. 1]: Thailand, Chanthamrong 74 (CMUB); PV469107*, PV469126*, PV469145*, PV469164*, PV469184*, PV469203*. Polyalthia cf. miliusoides: Borneo, RidsdaleDV-M2-11443 (L); AY518829, ---, ---, AY319028, AY319142, ---. Polyalthia obliqua: Borneo, Ambriansyah&ArifinAA1694 (L); AY518822, ---, ---, AY319029, AY319143, ---. Polyalthia stenopetala: Thailand, Chalermglin 540116 (HKU); JX227896, ---, ---, ---, ---, ---. Polyalthia stenopetala: Thailand, Chalermglin 440302 (TISTR, Bangkok); ---, ---, ---, AY319034, AY319148, ---. Polyalthia subcordata: Java, Gravendeel et al. 549 (L); AY518830, ---, ---, AY319036, AY319150, ---. Polyalthia suberosa: Utrecht Univ. Bot. Gard., Chatrou 480 (U); AY238965, AY841417, AY841502, AY238956, AY231289 and AY238949, JX544817. Polyalthia submontana: Australia, Sankowsky 3182 (HKU); JX227893, ---, ---, JX227918, JX227869, ---. Polyalthia cf. subsessilifolia: Borneo, Beaman 10272 (NY); JX227884, ---, ---, JX227909, JX227860, ---. Polyalthia suthepensis [= Polyalthia suthepensis-1]: Thailand, Chaowasku 202 (CMUB); PV469099*, PV469118*, PV469137*, PV469156*, PV469176*, PV469195*. Polyalthia suthepensis [= Polyalthia suthepensis-2]: Thailand, Chaowasku 236 (QBG); PV469100*, PV469119*, PV469138*, PV469157*, PV469177*, PV469196*. Polyalthia trochilia: Borneo, Burley et al. 807 (NY); JX227894, ---, ---, JX227919, JX227870, ---. Polyalthia xanthocarpa: Australia, Sankowsky 3150 (HKU); JX227895, ---, ---, JX227920, JX227871, ---. Polyalthia sp. A: Thailand, Chalermwong & Sinbumroong 15032021 (CMUB); PV469112*, PV469131*, PV469150*, PV469169*, PV469189*, PV469208*. Polyalthia sp. B: Thailand, Chanthamrong & Baka 45 (CMUB); PV469111*, PV469130*, PV469149*, PV469168*, PV469188*, PV469207*. Polyalthia sp. 2: Thailand, Chaowasku 238 (QBG); PV469103*, PV469122*, PV469141*, PV469160*, PV469180*, PV469199*. WIYA C. et al., Five new species of Polyalthia (Annonaceae) from Thailand 275 Appendix 2 Type specimens of relevant names studied. Miliusa concinna Ridl. Miliusa concinna Ridl. (Ridley 1920: 127). – Type: SIAM (now THAILAND) • Southwest, Koh Lak; 3 Apr. 1919; fl.; HamidFMSFieldNo.3802; [specimen studied: lectotype K1]. 1 https://plants.jstor.org/stable/viewer/10.5555/al.ap.specimen.k000691547 Polyalthia chantaranothaii Bunchalee & Chalermglin Polyalthia chantaranothaii Bunchalee & Chalermglin (in Bunchalee et al. 2021b: 276). – Type: THAILAND • Lampang, Me Ping; 21 Jun. 1926; fl.; Winit 1708; [specimen studied: holotype BK]. Polyalthia debilis (Pierre) Finet & Gagnep. Polyalthia debilis (Pierre) Finet & Gagnep. (Finet & Gagnepain 1906: 96). – Unona debilis Pierre (Pierre 1881: t. 29). – Type: VIETNAM • Cochinchine, Ba Ria, Mt Dinh; May 1866; fl.; Pierre 1771; [specimens studied: lectotype P1, isolectotypes P2,3]. 1 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00372676 2 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00372677 3 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00372678 Polyalthia evecta (Pierre) Finet & Gagnep. Polyalthia evecta (Pierre) Finet & Gagnep. (Finet & Gagnepain 1906: 91). – Unona evecta Pierre (Pierre 1881: t. 31). – Type: VIETNAM • Cochinchine, Bien Hoa, Song Lu; Feb. 1877; fl.; Pierre 1762; [specimens studied: lectotype P1, isolectotypes P2,3, BM4, L5,6]. 1 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432205 2 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432203 3 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432204 4 https://data.nhm.ac.uk/object/45df18da-ff7c-471d-bf9c-5800216af4fe 5 https://data.biodiversitydata.nl/naturalis/specimen/L%20%200183718 6 https://data.biodiversitydata.nl/naturalis/specimen/L%20%200038114 Unona evecta var. attopeuensis Pierre Unona evecta var. attopeuensis Pierre (Pierre 1881: sub t. 31). – Type: LAOS • Bassin d’Attopeu; Feb. 1877; fl.; Harmand 1349; [specimens studied: lectotype P1, isolectotypes P2,3]. 1 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432210 2 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432209 3 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432211 Polyalthia intermedia (Pierre) Bân Polyalthia intermedia (Pierre) Bân (Bân 2000: 95). – Unona evecta var. intermedia Pierre (Pierre 1881: t. 31A). – Type: VIETNAM • Cochinchine, prov. Baria, Noi; Jul. 1867; fl., young fr.; Pierre 289b; [specimen studied: lectotype P1]. 1 http://coldb.mnhn.fr/catalognumber/mnhn/p/p00432221 European Journal of Taxonomy 1022: 243–276 (2025) 276 Polyalthia khaoyaiensis Bunchalee & Chantar. Polyalthia khaoyaiensis Bunchalee & Chantar. (in Bunchalee et al. 2019: 172). – Type: THAILAND • Nakhon Ratchasima, Khao Yai National Park; 14 Mar. 1986; fl.; van Beusekom & Phengklai 45; [specimen studied: isotype L1]. 1https://data.biodiversitydata.nl/naturalis/specimen/L.1767376 Polyalthia minima Jovet-Ast Polyalthia minima Jovet-Ast (Jovet-Ast 1940: 75). – Type: VIETNAM • Annam, Phan Rang, Ca Na; 16 Jul. 1930; fl.; Poilane 17886; [specimen studied: holotype P1]. 1http://coldb.mnhn.fr/catalognumber/mnhn/p/p00601068 Polyalthia parviflora Ridl. Polyalthiaparviflora Ridl. (Ridley 1912: 49). – Type: MALAYSIA • Peninsular Malaysia, Pulau Langkawi, Kuala Malacca; Sep. 1890; fl., fr.; Curtis 2533; [specimen studied: isolectotype CAL1]. 1https://archive.bsi.gov.in/phanerogams-Image/en?link=CAL0000004428&column=szBarcode