Acronema handeloides, a new species from Jiaozi Mountain, Yunnan Province, China (Apiaceae)

81 Acronema handeloides, a new species from Jiaozi Mountain, Yunnan Province, China (Apiaceae) Xu-Dong Ma1, Hui-Min Li1, Ying Xie2, Jun-Wen Zhu1, Jun Wen1, Wei Zhou1, Bao-Cheng Wu1, Chun-Feng Song1 1 Jiangsu Key Laboratory for Conservation and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China 2 CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China Corresponding author: Chun-Feng Song ([email protected]) Copyright: © Xu-Dong Ma et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract Acronema handeloides, a new species of Apiaceae from Jiaozi Mountain in Yunnan Province, is described and illustrated herein. This species is similar to A. handelii and A. sichuanense but can be distinguished by its 1–2 branches; variable basal leaves; bracts 1 or occasionally present, bracteoles 1–3; subulate calyx teeth; linear-subulate, papillate petal apex; and broadly ovoid. Phylogenetic analyses also support that it is a monophyletic group sister to A. handelii and A. sichuanense. In accordance with the IUCN Red List criteria (2024), the conservation status of A. handeloides is preliminarily assessed as Data Deficient (DD). Key words: Acronema, alpine plants, new species, taxonomy, Yunnan Introduction Acronema Edgew. is distributed from the southern Himalayan region to the Hengduan Mountains. According to the Flora of China and subsequent records of new species and discoveries in recent years (Pan et al. 2005; Wang et al. 2013), approximately 22 species are currently recognized in China. The genus is characterized by its petals, which possess a filamentous and straight apex. Most species of Acronema are typically found in pristine alpine forests above 3,000 meters, making them difficult to encounter in early surveys. Due to the scarcity of specimens and the generally poor quality of available collections, this genus has always remained insufficiently studied within the Apiaceae. Due to the complex topography of the Hengduan Mountains, where high peaks and deep valleys form unique “Sky Island” ecosystems, the region exerts a profound influence on plant diversification and genetic structure (Zhang et al. 2021; Rana et al. 2025). Like many other alpine understory species, the genus Acronema exhibits a fragmented distribution across different mountain ranges and has gradually diversified into several unique species. It is common to find multiple Acronema species distributed at different altitudes on Academic editor: Alexander Sennikov Received: 28 October 2025 Accepted: 15 November 2025 Published: 2 December 2025 Citation: Ma X-D, Li H-M, Xie Y, Zhu J-W, Wen J, Zhou W, Wu B-C, Song C-F (2025) Acronema handeloides, a new species from Jiaozi Mountain, Yunnan Province, China (Apiaceae). PhytoKeys 267: 81–91. https://doi.org/10.3897/ phytokeys.267.174758 PhytoKeys 267: 81–91 (2025) DOI: 10.3897/phytokeys.267.174758 82 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema the same mountain. In 2024, during a survey of A. crassifolium Huan C.Wang, X.M.Zhou & Y.H.Wang on Jiaozi Mountain (Luquan County, Kunming, Yunnan), we discovered an extremely small plant initially suspected to be A. handelii H.Wolff or A. sichuanense S.L.Liou & R.H.Shan, characterized by a globose root and broadly ovate fruits with calyx teeth. To clarify its taxonomic status, we conducted further fieldwork in 2025, focusing on the morphology of petals and basal leaves. Our observations confirmed that this species is distinct from all known Acronema species. Since Zhou Jing inferred the phylogeny of the subfamily Apioideae (Apiaceae) using ITS sequences and the rps16 and rpl16 intron sequence variation, the phylogenetic position of the genus Acronema received clarification within this subfamily (Zhou et al. 2008, 2009). Subsequently, Chen Lian employed plastome data and ITS sequences to further resolve interspecific relationships among 16 Acronema species (Chen et al. 2024). To clarify the phylogenetic position of this species, we performed phylogenetic analyses based on ITS sequence data from 7 Acronema species, and the results confirmed our hypothesis. Due to its overall similarity in floral and fruit characteristics to A. handelii, we describe it herein as a new species, A. handeloides X.D.Ma & C.F.Song. Material and methods Species sampling In late August 2024, fruiting specimens were collected from Jiaozi Mountain in Luquan County, Kunming, Yunnan. Fresh ripe fruits were photographed in situ using an Olympus TG6 camera, and the number of oil ducts was examined. In late July 2025, flowering individuals were revisited at the same site, with emphasis on collecting specimens representing morphological variation within the population. Fresh petal characteristics were documented with the same camera. Subsequent morphological measurements and counts were conducted with ImageJ to supplement the specimen records. DNA sequencing We assembled the nuclear ribosomal internal transcribed spacer (nrITS) of A. handeloides to determine its phylogenetic position within the genus. In total, 7 currently recognized species of Acronema and 4 currently recognized species of the Acronema clade (Sinocarum cruciatum (Franch.) H.Wolff, S. filicinum H.Wolff, S. muliense L.J.Gui, Y.P.Xiao & X.J.He, S. vaginatum H.Wolff) were included, with two additional species (Meeboldia delavayi (Franch.) W.Gou & X.J.He, M. yunnanensis (H.Wolff) Constance & F.T.Pu ex S.L.Liou) selected as outgroups. Sequences of A. handeloides, A. chinense, A. minus, A. sichuanense, and A. handelii were newly generated in this study, while the remaining sequences were retrieved from GenBank. Detailed information on the material sources and GenBank accession numbers is provided in Tables 1, 2. The total genomic DNA of A. handeloides was extracted by Wuhan Benagen. The nrITS region was assembled using GetOrganelle v.1.7.7.1 (Jin et al. 2020). Geneious Prime 2024.0.2 (Kearse et al. 2012) was used to annotate the 83 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema assembled plastomes and extract the ITS1, 5.8S, and ITS2 regions used in the phylogenetic analysis. The MAFFT alignment plug-in of Geneious was used to align the 23 sequences obtained, using the default parameters. IQ-TREE 2 (Bui et al. 2020) was used, and the K2P+G4 model was selected to construct a maximum likelihood (ML) tree with 1000 bootstrap replicates. In the ML analysis, bootstrap support (BS) values < 50% were considered unreliable, values between 50% and 75% were considered moderately supported, and values > 75% were considered strongly supported. BI analyses were conducted using MrBayes v.3.2.7 (Ronquist et al. 2012) under the selected JC model with the following settings: mcmc ngen = 2,000,000; nruns = 2; nchains = 4; samplefreq = 1000; temp = 0.2; sumt burnin = 2000. In the BI analysis, posterior probability (PP) values < 0.90 were considered poorly supported, values between 0.90 and 0.95 were considered moderately supported, and values > 0.95 were considered strongly supported. The final sequence alignments have been deposited in the Zenodo repository (DOI: https://doi. org/10.5281/zenodo.17451735). Table 1. Newly generated sequences. Taxon Locality Voucher Acronema handeloides China, Yunnan, Kunming MXD370-1 (NAS) Acronema handeloides China, Yunnan, Kunming MXD370-4 (NAS) Acronema handelii China, Yunnan, Diqing MXD364-2 (NAS) Acronema handelii China, Yunnan, Diqing MXD364-15 (NAS) Acronema sichuanense China, Sichuan, Ngaba MXD365-2 (NAS) Acronema sichuanense China, Sichuan, Ngaba MXD365-9 (NAS) Acronema sichuanense China, Sichuan, Ngaba MXD365-12 (NAS) Acronema chinense China, Sichuan, Ngaba MXD366-1 (NAS) Acronema chinense China, Sichuan, Ngaba MXD366-6 (NAS) Acronema minus China, Yunnan, Kunming MXD290a-1 (NAS) Acronema minus China, Yunnan, Kunming MXD372-1 (NAS) Acronema minus China, Yunnan, Kunming MXD372-2 (NAS) Table 2. Source of materials studied and GenBank accession numbers. Taxon Voucher ITS Acronema muscicola XZ2011081741 (SZ) KP940756 Acronema schneideri YLDP244A MH117405 Acronema graminifolium 1MT359945 Meeboldia delavayi G19072401 (SZ) MN688992 Meeboldia yunnanensis G18071908 (SZ) MN688997 Sinocarum cruciatum XYP19080301 MN846686 Sinocarum vaginatum XYP19080402 MN846688 Sinocarum muliense GLJ18081101_1 MZ054145 Sinocarum muliense GLJ18081101_2 MZ054146 Sinocarum filicinum XYP19080302 MT586806 Sinocarum filicinum XYP19091803 MT586807 84 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema Results and discussion General morphology Acronema handeloides, A. handelii, and A. sichuanense are all short herbs with globose roots, petals featuring filiform, papillate tips, prominent calyx teeth, and broadly ovate fruits. However, A. handeloides exhibits less developed leaf forms, ranging from simple to trifoliate or ternate-bipinnate. In contrast, the basal leaves of A. handelii are monoto bipinnate, while those of A. sichuanense are more consistently ternate-bipinnate. Beyond leaf morphology, the three species also differ in the number of umbels and umbellules. Acronema handeloides has fewer of both, typically bearing 2–4 (rarely up to 5) umbels and umbellules. Acronema handelii, on the other hand, possesses 4–6 (often 5) umbels and 3–9 (often 6) umbellules, and A. sichuanense has 3–6 (often 5) umbels and 3–10 (often 8) umbellules. Regarding petal morphology, all three species possess papillae at their petal apex. However, A. handeloides more closely resembles A. handelii in having ovate-lanceolate petals, which clearly distinguish them from the ovate petals of A. sichuanense. The most critical distinguishing feature is that A. handeloides possesses 1–2 branches and 1–3 bracteoles. Within the genus, these characteristics are shared only with A. tenerum (DC.) Edgew. and A. minus (M.F.Watson) M.F.Watson & Z.H.Pan, while both A. handelii and A. sichuanense lack these features. Phylogenetic analyses In the phylogenetic analysis, species in the genus Acronema formed a monophyletic group, clearly distinguishable from those in the genus Sinocarum, and exhibited strong support (PP = 1, BS = 100%). Within Acronema, A. handeloides, A. handelii, and A. sichuanense each clustered into three independent monophyletic clades. The high support of each clade indicates that all three species are monophyletic groups with clear genetic differentiation boundaries, strongly supporting the taxonomic status of A. handeloides as a valid species. Furthermore, these three morphologically similar species formed a monophyletic group that clustered into the same clade, exhibiting the highest support (PP = 1, BS = 100%), further confirming their close phylogenetic relationship (Fig. 1). Notably, A. muscicola (KP940756) was placed within this clade, but its true phylogenetic position could not be determined based on a single specimen. This uncertainty is exacerbated by the significant inconsistency between its known morphological features (e.g., trifoliate basal leaves, thick papery leaf blades, and completely sheathed petioles) and those of all other taxa within this clade. Phylogenetic evidence from Chen Lian (Chen et al. 2024) (a phylogenetic tree based on ITS sequences) further confirms that the phylogenetic relationships of A. muscicola require further molecular verification. After excluding the highly uncertain A. muscicola, the cluster of A. handeloides, A. handelii, and A. sichuanense exhibits a branch length < 0.01 coupled with low node support. This combined pattern, characterized by extremely short branches and insufficient node support, represents a classic molecular signature of recent rapid radiative evolution. In this scenario, incomplete lineage sorting leads to conflicting phylogenetic signals captured by different phylogenetic methods, a typical feature of recently divergent groups. Therefore, further research is needed 85 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema to determine the exact sister-group relationships of A. handeloides. Specifically, multi-gene joint analysis of nuclear and chloroplast genes in Acronema and coalescent simulation analysis should be employed, thereby enabling the definitive identification of the sister group of A. handeloides. Taxonomic treatment Acronema handeloides X.D.Ma & C.F.Song, sp. nov. urn:lsid:ipni.org:names:77370065-1 Figs 3, 4 Diagnosis. Acronema handeloides has flowers and fruits similar to A. handelii and A. sichuanense but differs from these latter in its frequently branched stems (1–2 branches), fewer number of umbel rays and umbellule rays, 1–3 bracteoles, and variable shape of basal leaves. These three species are readily distinguishable by key morphological characteristics, as detailed in Table 3 and Fig. 2. Type. China • Yunnan: Kunming City, Luquan County, Wumeng Township, Jiaozi Mountain, 26.0795°N, 102.8480°E, in the moss understory of the Rhododendron forest, 15 August 2025 (fl. & fr.), X.D.Ma & Y.X MXD370 (holotype: NAS!; isotype: NAS!). Description. Annual to biennial herbs, glabrous, 1–10 cm tall. Roots spherical to ellipsoidal, 3–4 mm in diameter. Stems slender, with 1–2 lateral branches or unbranched. Basal leaves: petiole 8–30 mm, sheath narrow; leaf blade polymorphic, 1–1.5 cm long, 1.3–2 cm wide; when simple, blade broadly ovate, base truncate to slightly cordate, margin irregularly serrate, or trifid to tripartite, lobes obovate, apex trifid; when trifoliolate, leaflets short-petiolulate, apex trifid, lobes shallowly 1–3-lobed at apex; when 2-ternate, pinnately compound, ultimate segments obovate, apex trilobed. Cauline leaves similar to basal ones, occasionally Figure 1. Phylogenetic tree inferred from the ITS sequences. Bayesian posterior probability values (PP) / bootstrap support values (BS) are shown below the branches. 86 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema Figure 2. Morphological comparisons between Acronema handelii (A), A. sichuanense (B), A. handeloides (C). A1–C1. Flower; A2–C2. Bracteoles and umbellules; A3–C3. Bracts and rays; A4–C4. Basal leaves. Photograph credits: X.D. Ma. 87 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema simple and lanceolate. Peduncle 1.5–2.5 cm long; bracts 1 or absent, lanceolate; rays 2–5, 5–20 mm long, subequal; bracteoles 1–3, subulate; umbellules 2–5, 4–9 mm long, subequal. Calyx teeth subulate, conspicuous. Petals purplish red, ovate to obovate, ca. 1 mm long; apex linear-subulate, papillate, ca. 1 mm long. Fruit broadly ovoid, ca. 1 × 1.5 mm, base cordate, glabrous; primary ribs filiform, inconspicuous; vittae 1–2 in each furrow, 2 on the commissure. Phenology. Flowers are observed from July to August, and fruits from August to September. Etymology. The species epithet ‘handeloides’ is derived from the combination of “handel” (from Acronema handelii) and the suffix “-oides” (meaning “resembling”), indicating the morphological similarity of this new species to A. handelii. The Chinese name “拟中甸丝瓣芹” (nĭ zhōng diàn sī bàn qín) is a direct translation from the epithet, used to maintain nomenclatural consistency and avoid ambiguity. Distribution and habitat. This new species is currently only found in the moss understory of the Rhododendron forest at 3700 m on Jiaozi Mountain in Luquan County, Kunming, Yunnan (Fig. 5). Additional material examined (paratype). China • Yunnan: Kunming City, Luquan County, Wumeng Township, Jiaozi Mountain, 26.0795°N, 102.8480°E, on the moss understory of the Rhododendron forest, 31 August 2024 (fr.), X.D. Ma & H.R.Zhuang MXD290 (NAS!). Conservation status and discussion. Following the description of A. crassifolium by Wang Huanchong in 2013, A. handeloides represents another new species of Acronema discovered on Jiaozi Mountain. Located near Kunming, Jiaozi Mountain is renowned as “the premier mountain of central Yunnan” and has been increasingly developed for tourism due to its scenic landscapes and winter snowfall (Chang 2019; Zhang et al. 2020). This development poses potential threats to understory habitats through intensified human activities. Acronema species typically occur in moist, moss-rich understories at high altitudes, representing a highly specialized ecological niche that is particularly vulnerable to disturbance in visited areas. To date, Acronema handeloides is documented only from Jiaozi Mountain, with no prior collection records. Field observations indicate that the new species exhibits low fruit abortion rates in the wild, implying successful reproductive capacity under natural conditions. Despite this, available data on its full distribution and population trends remain incomplete. Therefore, in accordance Table 3. Comparison of morphological characters between Acronema handeloides, A. handelii, and A. sichuanense. Characters Acronema handelii A. sichuanense A. handeloides Basal leaves monoto 2-ternate pinnate 2-ternate-pinnate Simple leaf to trifoliolate to 2-ternate pinnately compound leaf Plant branching Stem solitary Stem solitary Often with 1–2 branches Number of umbel rays and umbellule rays Umbels with 4–6 rays (often 5), umbellules with 3–9 rays (often 6) Umbels with 3–6 rays (often 5), umbellules with 3–10 rays (often 8) Umbels with 2–4 rays (often 3, rarely up to 5), umbellules with 2–5 rays (often 3) Bracts and bracteoles Bracts and bracteoles absent Bracts and bracteoles absent Bracts 1 or occasionally present, bracteoles 1–3 Petal characteristics Ovate-lanceolate, apex linear-subulate, papillate Obovate, apex linear-subulate, papillate Ovate-lanceolate, apex linear-subulate, papillate 88 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema Figure 3. Acronema handeloides X.D.Ma & C.F.Song. A. Habit; B. Basal leaves and stem leaves (B1, B2, B3 show different leaf shapes); C. Flower and the linear-subulate apex with papillate; D. Fruit; E. Vittae number. Drawn by X.D. Ma. 89 PhytoKeys 267: 81–91 (2025), DOI: 10.3897/phytokeys.267.174758 Xu-Dong Ma et al.: Taxonomic study of Acronema Figure 4. Acronema handeloides X.D.Ma & C.F.Song. A. Plant in natural habitat; B. Single individual; C. Basal leaves (Ca1, Cb1. Adaxial surface; Ca2, Cb2. Abaxial surface); D. Bracts and rays; E. Bracteoles and umbellules; F. Flower and petal apex (F1. Flower; F2. Linear-subulate apex with papillate); G. Fruit. Photographs by X.D. Ma. Figure 5. The distribution of Acronema handeloides (red circle).