identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
13369960870B534583A56540EBDEEDD2.text	13369960870B534583A56540EBDEEDD2.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Rhododendron mulunense Y. S. Huang & X. X. Mao 2026	<div><p>Rhododendron mulunense Y. S. Huang &amp; X. X. Mao sp. nov.</p><p>Figs 1, 2, 3, 4 (A – C)</p><p>Type.</p><p>China. • Guangxi: Hechi City, Huanjiang County, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=107.95&amp;materialsCitation.latitude=25.1" title="Search Plazi for locations around (long 107.95/lat 25.1)">Mulun National Nature Reserve</a>, 25°06'N, 107°57'E, on the limestone under sparse forest, in summits of karst mountains, elev. 641 m, 3 March 2021, Ying Qin et al., GXQY 20210303021 (holotype: IBK! 00470814, isotype: IBK! 00470813) (Fig. 1)</p><p>Diagnosis.</p><p>Resembles Rhododendron wumingense Fang but distinguishable by the absence of indumentum on young shoots, leaf margins, and petioles (vs. sparsely setose), longer and larger leaves (4.2–7.4 × 2.3–3.8 vs. 3.5–4.5 × 1.8–2.4 cm), relatively sparser scales on abaxial leaf surfaces (1–4 vs. 1–3 × their own diameter apart), corollas that are tubular funneled (vs. broadly funneled), longer and wider (5.9–7.5 × 4.7–7 vs. 3.1–4.5 × 3.3–4.9 cm) with slender tubes (2.9–3.9 × 0.5–1.2 vs. 1.9–2.5 × 1.7–2.4 cm), outer surface of corolla tubes white flushed with pink (vs. yellowish green) and pubescent but not scaly (vs. sparsely scaly and hairless) (Figs 1, 2, 4; Table 1).</p><p>Description.</p><p>Shrubs, 0.5–2 m tall; young shoots stout, short, and relatively sparse, brownish scaly, hairless. Stems robust, erect, much-branched and sparsely scaly. Leaf-bud scales acuminate, elongated at flowering time. Petioles densely scaly, hairless, 0.5–0.8 cm long. Leaf leathery, elliptic, oblong-lanceolate, 4.2–7.4 × 2.3–3.8 cm, apex acute or obtuse, mucronate, base tapering or narrowly cuneate, margin slightly revolute and glabrous; adaxial surface green with minute and transparent scales, somewhat shining, hairless; abaxial surface usually gray-white, densely scaly, scales one to four times their own diameter apart, pale brown or brownish-red; midrib sunk adaxially, conspicuously raised abaxially, and lateral veins sunk adaxially but not obvious abaxially. Inflorescences terminal, umbellate, 3 - flowered, sometimes 2 - or 4 - flowered; pedicel 0.5–1 cm long, densely scaly, hairless. Calyx 5 - lobed, lobes 0.5–1 × 0.5–0.8 mm, rounded or triangular, outside densely to moderately scaly, margins glabrous. Corolla tubular-funnelform, 5.9–7.5 × 4.7–7 cm, narrowly tubular near the middle and lower part of corolla, 5 - lobed; corolla lobes white, with yellow markings inside; corolla tubes slender, 2.9–3.9 × 0.5–1.2 cm, white flushed with pink and not scaly but pubescent outside, glabrous with yellow markings inside. Stamens 10, unequal, 3.7–5.6 mm long; filaments densely pubescent at the base. Ovary ovoid, 5 - locular, 0.7–1.2 mm long, densely scaly, hairless. Style s scaly and pubescent near the base, curved upwards, extend beyond the corollas. Capsule ovoid, 1.4–2.1 × 0.4–0.7 cm, densely scaly, hairless, calyx persistent.</p><p>Phenology.</p><p>Flowering from March to April. Fruiting from July to August.</p><p>Etymology.</p><p>The specific epithet of this newly described species refers to its type localities at Guangxi Mulun National Nature Reserve, part of the South China Karst landscape registered in UNESCO’s World Heritage List.</p><p>Vernacular name.</p><p>Simplified Chinese: 木论杜鹃; Chinese pinyin: mù lùn dù juān.</p><p>Distribution and ecology.</p><p>This new species is known from five localities to date. Three localities are fragmentally distributed in the same province, including two localities in Huanjiang County, Hechi, NW Guangxi, and one smaller locality at Molu Mountain (105°52'E, 23°23'N) in Napo County, Baise, SW Guangxi. The remaining two localities were distributed at Dongli (107°59'E, 25°22'N) in Mao-lan National Nature Reserve, Libo County, S Guizhou (Fig. 3). The plants were found on limestone under sparse, mixed, broad-leaf forest on the karst mountaintop (Figs 2 A, 4 A) at elevations from 640 to 1350 m (Fig. 3). The associated plants include Calocedrus rupestris Aver., T. H. Nguyên &amp; L. K. Phan ( Cupressaceae), Zanthoxylum dimorphophyllum Hemsl. ( Rutaceae), Platycarya strobilacea Siebold &amp; Zucc. ( Juglandaceae), Polygala wattersii Hance ( Polygalaceae), Acer sycopseoides Chun ( Sapindaceae), Alyxia schlechteri H. Lév. ( Apocynaceae), Leptopus pachyphyllus X. X. Chen ( Phyllanthaceae), Rhododendron liboense Zheng R. Chen &amp; K. M. Lan ( Ericaceae), Paphiopedilum micranthum Tang &amp; F. T. Wang ( Orchidaceae), and Ophiorrhiza japonica Blume ( Rubiaceae).</p><p>Systematic position in Rhododendron .</p><p>Subsect. Maddenia Sleumer, Sect. Rhododendron, Subgen. Rhododendron .</p><p>Conservation status.</p><p>According to multiple fieldwork expeditions for Rhododendron plants around the karst mountains of Guangxi and Guizhou, five subpopulations or localities of R. mulunense have been discovered. Fewer than 30 mature individuals were found at two localities of less than 100 × 100 m 2 in Huanjiang County, nine mature individuals were found at Molu mountain, and approximately 150 mature individuals were found in two localities at Mao-lan National Nature Reserve. Based on our investigations, the habitat quality and population size of R. mulunense have a continuing downward trend. Although two subpopulations, or all individuals at type localities from Huanjiang, are protected well, there are severe threats in other localities. Two subpopulations are situated in very small rocky hills in Mao-lan, with limited area encircled by urban roads, residential communities, and farmlands. Another subpopulation faces more severe threats in Napo, including its few mature individuals, limited distribution, and degraded habitat due to deforestation and wind power projects. Based on these findings, the conservation status of this new species should be assessed as Endangered (EN) under the IUCN Red List criteria C 2 a (i); D (Gibbs et al. 2011; IUCN 2012). This recommendation reflects the extremely limited distribution and very small population sizes of R. mulunense, combined with an observed continuing decline in numbers of mature individuals resulting from its close association with human activities and vulnerability to habitat loss.</p><p>Conservation studies of Rhododendron species indicated that the member botanic gardens of BGCI (Botanic Garden Conservation International, Richmond, UK) and the Global Conservation Consortium for Rhododendron play important roles in the conservation of species of subsect. Maddenia (BGCI 2020; Hu et al. 2024). Notably, a study focusing on conservation of Maddenia species in global botanic gardens suggested that ex situ living collections are urgently required to conserve wild endemic Maddenia species in countries of origin, and broader sampling of wild populations should be conducted for these threatened species (Hu et al. 2024). We propose extending the ecogeographical range of wild collections of R. mulunense and establishing ex situ collections in three member gardens of BGCI in China (Kunming Botanical Garden, Guilin Botanical Garden, and Lushan Botanical Garden). Meanwhile, given the threats to this endangered species, we urge local authorities to carry out habitat restoration and protection of the subpopulations in Mao-lan and Napo.</p><p>Additional specimens examined.</p><p>China. Guangxi Zhuang Autonomous Region: Hechi City, Huanjiang County, Chuanshan Town, Mulun National Nature Reserve, alt. 641 m, 3 March 2021, Y. Qin et al. GXQY 20210303022 (IBK), GXQY 20210303023 (IBK), GXQY 20210303024 (IBK, IBSC), GXQY 20210303025 (IBK, IBSC), GXQY 20210303026 (IBK, PE), GXQY 20210303027 (IBK, PE), GXQY 20210303028 (IBK, PE), GXQY 20210303029 (IBK) ; the same town, Jianfulun, alt. 1000 m, 22 April 2025, J. H. Liang, M. L. Mo &amp; Q. M. Wei YB 0225 (IBK) ; the same town, Zhonglun, alt. 970 m, 29 March 2025, Y. S. Huang Y 25032906 (IBK) ; the same locality, elev. 980 m, 23 April 2025, J. H. Liang, M. L. Mo &amp; Q. M. Wei YB 0264 (IBK) .</p><p>Notes.</p><p>The species of Rhododendron subsect. Maddenia show high interspecific diversification in morphological traits, including whether shoots and leaves have indumentum, leaf shape and size, scale density on the abaxial leaf surface, corolla shape and size, indumentum and scales on the corolla and tube exterior, and the color of the corolla and tube exterior (Min and Fang 1990; Fang et al. 2005). Some of these divergences between species may be attributed to heterogeneous habitat conditions. In south China, certain Maddenia species growing in dry conditions or subhumid habitats generally have hairless shoots and leaves, such as R. pachypodum Balf. f. &amp; W. W. Sm., R. liliiflorum Levl., and R. kiangsiense Fang, while the shoots and leaves of species growing in moister or humid conditions tend to be covered with setose hairs; for example, R. wumingense Fang, R. ciliicalyx subsp. lyi (Levl.) R. C. Fang, and R. levinei Merr. (Table 1). Therefore, species distributed across different conditions or habitats have distinct morphological traits in subsect. Maddenia . Meanwhile, this indicates that habitat conditions can be used to discriminate specific species in this group.</p><p>Among the morphological traits mentioned above, the presence or absence of indumentum on shoots and leaves, the shape and size of the corolla and tube, the presence or absence of indumentum and scales on the corolla and tube exterior, the presence or absence of indumentum on calyx margins, the size of the calyx lobe, and the scale density on the abaxial leaf surface are the most taxonomically important. Both the morphological characteristics and geographic distribution of R. mulunense are most similar to those of R. wumingense, from which it can nevertheless be readily distinguished (Figs 2, 4; Table 1). Moreover, R. mulunense grows on limestone under subhumid conditions with sparse forest cover (Figs 2 A, B, 4 A), while R. wumingense is found on granite rocks under moister conditions in dense forest on montane slopes (Fig. 4 E) or on open wet cliffs.</p><p>To assess whether it should be recognized as a new species, we compared R. mulunense with other similar species (Fig. 5; Table 1). Morphologically, this newly discovered species is similar to R. pachypodum and R. dendricola Hutch.: it has oblong-lanceolate leaves, an undeveloped calyx, and white flowers. However, it can be distinguished from these species by its tubular-funnelform corolla with an obviously slender tube lacking scales. R. pachypodum has a later flowering period, and R. dendricola has a narrow, non-overlapping distribution in the Himalaya – Hengduan Mountains, where it generally grows among conifers (Gibbs et al. 2011). In terms of the number of flowers per inflorescence and geographical distribution, R. mulunense is similar to other species of subsect. Maddenia, including R. ciliicalyx subsp. lyi, R. liliiflorum (including the synonym R. chunienii Chun and W. P. Fang), R. levinei, and R. kiangsiense (Li 2008; Geng 2004, 2014; Yang et al. 2022), but it can be readily distinguished by its tubular-funnelform corolla with the tube pubescent and not scaly, its undeveloped calyx, and an earlier flowering period.</p><p>Hu et al. (2023) showed that there have been polyploidization events in multiple species within subgen. Rhododendron, which could result in phenotypes distinct from their diploid progenitors. Nevertheless, polyploidization seldom occurs in subsect. Maddenia, and all related species, including R. wumingense, R. pachypodum, R. dendricola, R. ciliicalyx, R. liliiflorum, R. levinei, and R. kiangsiense, have been confirmed as diploids (Hu et al. 2023). Based on these findings, our study concludes that R. mulunense represents a new species in subsect. Maddenia of subgen. Rhododendron . Detailed comparisons of morphology, phenology, and distributions of R. mulunense and related species are summarized in Table 1. In addition, an identification key is provided to facilitate discrimination of R. mulunense from similar Maddenia species.</p></div>	https://treatment.plazi.org/id/13369960870B534583A56540EBDEEDD2	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Hou, Ying;Huang, Yu-Song;Luo, Liu-Juan;Chen, Zheng-Ren;Mao, Xing-Xing	Hou, Ying, Huang, Yu-Song, Luo, Liu-Juan, Chen, Zheng-Ren, Mao, Xing-Xing (2026): Rhododendron mulunense (Ericaceae), a new species from the karst mountains of Guangxi and Guizhou provinces, China. PhytoKeys 269: 99-112, DOI: 10.3897/phytokeys.269.175011
