Cheniella tsoongii X. Peng, K. W. Jiang & T. Y. Tu

Peng, Xia, Jiang, Kai-Wen, Fang, Tian-Song, Gu, Qiao-Yun, Gu, Shi-Ran, Xie, Zhi, Duan, Lei, Li, Shi-Jin, Wang, Xiang-Ping, Shi, Miao-Miao, Tu, Tie-Yao & Zhang, Dian-Xiang, 2024, Cheniella tsoongii (Leguminosae: Cercidoideae), a rare, critically endangered new species from southern China, Phytotaxa 646 (2), pp. 193-202 : 194-200

Cheniella tsoongii X. Peng, K. W. Jiang & T. Y. Tu , sp. nov. DZKaeāü (zhào qìng dé zhāo téng). Figs. 1–3

Type: — CHINA. Guangdong: Zhaoqing, Guangning , Zhouzai Township , elev. 235m, 17 June 2022 (fl.), Z. Xie XieZ2746P1 [holotype IBSC1011900 !( Fig.2 & 3 ), isotypes IBSC1011901 !, IBSC1011902 !, IBSC1011903 !, IBSC1011904 !, IBSC1011905 !, IBSC1011906 !, IBSC1011907 !, IBSC1011908 !, IBSC1011909 !, NPH0002251 !, NPH0002252 !, PE02376997 !] .

Diagnosis: — Cheniella tsoongii most resembles C. corymbosa in leaf lobe shape, inflorescence structure, axis length, lengths of fully developed stamens and mature pistils, and tardily dehiscent legumes, but it can be easily distinguished from C. corymbosa by its white petals with an oval blade (vs. pinkish petals with a near circular blade in C. corymbosa ), yellow anthers (vs. reddish-purple), 11–16 mm hypanthium (vs. 18–28 mm), hypanthium greatly shorter than pedicel (vs. hypanthium longer than or equal to pedicel) and densely ferruginous-tomentose young branches and leaves (vs. sparsely hairy). A detailed morphological comparison of this new species with its four related species was summarized in Table 1 .

Description: —Clumps of woody liana, relying on tendrils to climb trees, shrubs, bamboos, etc., grow upwards and outwards, and even cover the canopies. Young branches cylindrical, mostly purplish-red, densely tomentose with ferruginous, ascending hairs. Tendrils inserted in the axils of the opposite leaves, slightly compressed and densely pubescent with rust-colored long hairs. Leaves unifoliolate, alternate, rarely distichous, deeply bilobed to 3/5–4/5, with a mucro ca. 3 mm, cordate at base, 2.5–5.1 × 2.6–6.5 cm, the lobes slightly pointed at apex; dark green adaxially, densely villose with ± appressed, light-brownish hairs; greyish-green abaxially, densely tomentose with ferruginous hairs, denser along veins and near the base of the leaf; primary veins 7–9; petioles 0.7–2 cm, purplish-red, indumentum similar to branches. Stipules crescent, ca. 2.7–3 × 0.5–1 mm, apex blunt to acute, growing on both sides at the base of the petiole, adaxial surface glabrous, abaxial surface slightly appressed ferruginous pilose. Inflorescence an elongated corymbose, axillary or terminal on lateral branchlets, occasionally with two opposite fertile branchlets borne on the top of a branch, and then a raceme borne internally between these two branchlets; usually unbranched, axis 2.7–6.6 cm. Flowers abundant, nearly actinomorphic. Calyx usually splitting into 2+2+1, reflexed when flowering, abaxial surface pubescent with ferruginous hairs. Pedicels longer than hypanthia, up to 2.8 cm, indumentum similar to branches. Bracts filiform, ca. 3 mm, located at the base of the peduncle. Bracteoles filiform, ca. 2 mm, in pairs located at 1/3 of the pedicel. Buds ovate, acute, 6–7 × 3–3.8 mm, green or purplish-red, densely ferruginous hairs similar to peduncles. Hypanthia 11–16 mm, tubular, indumentum similar to branches. Petals 5, white, nearly equal in size, slightly crisped, 14–17 × 8–10 mm, with a basal claw 2–3 mm, inner surface glabrous, outer surface sparsely with ferruginous villose, denser near the basal middle part. Disc fleshy, yellowish-green, becoming red with age. Fertile stamens 3, mounted on lower part of disc; filaments of fertile stamens white, glabrous, equal to or slightly longer than petals; anthers elliptic, yellowish, longitudinal dehiscence; pollens yellow; staminodes 7, mounted on the fleshy disc, filiform, two of them between the three fertile stamens, five others opposite to the fertile stamens. Gynoecium nearly similar in length to the fertile stamens when fully developed, glabrous; ovary glabrous, stipitate, from greenish-yellow to pinkish with age; stigma capitate, greyish-green, glabrous, secretes mucus when pollen exhausted. Legumes glabrous, straight, occasionally twisted, tardily dehiscent, 5.7–14.5 × 1.5–2.3 cm. Seeds 5–18 per fruit.

Phenology: —Flowering in May to September; fruiting in August to December.

Distribution and ecology: — Cheniella tsoongii is currently known only from Guangning County, Zhaoqing City, Guangdong Province ( Fig. 4 ). It occurs in open habitats alongside creek valleys, growing upwards by wrapping around poles of the bamboo Bambusa chungii McClure in a surrounding economic forest.

Etymology: —The specific epithet tsoongii honors renowned Chinese botanist and plant collector Mr. Kwan Kwang Tsoong (Ġfl光 / fiḋ光, 1869–1940), who first collected the specimens of this new species in 1919 from Zhaoqing, Guangdong Province. Tsoong dedicated his career to systematically exploring and documenting the flora of southern China, not only established the first plant herbarium (PEY) in China, but also ushered in a new era in which Chinese scholars collected and produced specimens by themselves for taxonomic research. His historic collection represents the earliest known record of Cheniella tsoongii and provides crucial data that facilitates modern revision and conservation of this rare and endangered species. Naming this new taxon in recognition of Tsoong's contributions to botanical knowledge of the region is a fitting tribute to his extensive fieldwork and collection efforts over a century ago. The Chinese name is given as DZKaeāü (Pinyin: zhào qìng dé zhāo téng), which represents the type locality and currently the only distribution location—Zhaoqing, Guangdong Province, China.

Conservation status: —We discovered only one small population of Cheniella tsoongii with less than 10 individuals at its type locality. Despite intensive searches across the area during fieldwork in 2022 and 2023, no additional individuals were found. Combined with the only three known historical collections and extent plants, this species only occurs in Zhaoqing, Guangdong, China. All of this evidence suggests that this species is uncommon. The type locality—Guangning County is the area with the highest forest coverage in Zhaoqing City, reaching 82.29%. However, most of it is secondary artificial forests, mainly consisting of Eucalyptus spp. , Pinus massoniana Lambert , bamboos, and other timber species, as well as economic tree species such as Camellia oleifera C. Abel and Cinnamomum cassia (L.) D. Don, and the native mixed forests remain rare. Habitat degradation from deforestation for timber and agriculture and frequent human activity has severely impacted this region over the past century. The single clump occupies a roadside amid bamboo remnants, making it highly vulnerable to accidental or intentional damage. Few fruits were collected, implying that there are likely more than one individual in the clump or nearby as species of Cheniella are mostly self-incompatible ( Zeng 2021). However, this population is still very small, and low observed fruit set may limit population expansion. Based on the exceedingly small population size observed currently and ongoing threats from habitat loss and modification, although it’s not possible here to generate an EOO value for the species due to limited access to locality data, we still suggest assessing C. tsoongii as Critically Endangered [CR B1ab(iii)+B2ab(iii)] according to IUCN (2022) criteria and as a plant species with extremely small populations ( Sun et al. 2019). Enhanced protection (both ex-situ and in-situ) and regenerations of this species’ habitat are urgently needed to rescue it from imminent extinction.

Additional specimens examined (paratypes):— CHINA. Guangdong: Zhaoqing, Qixingyan, 16 May 1919, K. K. Tsoong 3006 (PEY, PE). Zhaoqing, Dinghu District, Taipingtian, 14 June 1975, G. L. Shi 11539 (IBSC). Zhaoqing, Guangning, Zhouzai Township, Qinggui Forest farm, 11 August 1983, G. L. Shi 14393 (IBSC). Zhaoqing, Guangning, Zhouzai Township, X421, near Maniaokou, elev. 184.55 m, 29 July 2023, K. Chiang & Z. M. Li KC966 (NPH). Zhaoqing, Guangning, Zhouzai Township, elev. 220 m, 28 September 2022, S. R. Gu & Z. Xie GuSR136 (IBSC).

Figures

FIGURE 1. Cheniella tsoongii X. Peng, K. W. Jiang & T. Y. Tu, sp. nov. A. Habitat; B. Reproductive branch; C. Leaves and branches; D. Tendrils; E. Stipules; F. Young inflorescence; G. Young flower; H. Old flower; I. Young inflorescence, showing bracts and bracteoles; J. Young inflorescence, showing hypanthia; K. Bud; L. Lateral view of a flower, showing the reflexed calyx lobes and hypanthium greatly shorter than pedicel; M. Adaxial surface of leaf; N. Abaxial surface of leaf; O. Young legume; P. Mature legume. Scale bar in K, L, M, N, O and P = 1 cm. Photographs taken by Zhi Xie (A–D, G, J, P); Tie-Yao Tu (E, F, H, I, K, L); Xia Peng (M–O).

FIGURE 2. Cheniella tsoongii X. Peng, K. W. Jiang & T. Y. Tu, sp. nov. A. Flowering branches; B. Bud; C. Open flower; D. Flower with petals removed; E. Petals; F. Androecium; G. Gynoecium; H. Pod; I. Leaf. Drawn by Yun-Xiao Liu.

FIGURE 3. Holotype of Cheniella tsoongii X. Peng, K. W. Jiang & T. Y. Tu (IBSC1011900).

FIGURE 4. Geographical distribution of historical records and living plants.