Tarenna pendula Y. H. Qin, S. X. Yu & W. H. Wu, 2025

Qin, Yong-Hua, Bussmann, Rainer W., Liu, Zhi-Rong, Li, Man, Xia, Chang-Ying, Wu, Wang-Hui & Yu, Sheng-Xiang, 2025, Tarenna pendula (Rubiaceae), a new species from Guangxi, China, PhytoKeys 257, pp. 1-8 : 1-8

Tarenna pendula Y. H. Qin, S. X. Yu & W. H. Wu sp. nov.

Figs 1 , 2 , 3

Diagnosis.

Similar to Tarenna tsangii , but distinguished by its small form, asymmetrical leaves, vegetative leaves larger than inflorescence leaves, blades adaxially pilosulous, pendulous inflorescences, longer pedicels (15–35 mm vs. 4–7 mm in T. tsangii ), shorter corolla tubes (1–1.4 cm vs. 1.8–1.9 cm), multiple ovules per locule (vs. 2), and sparsely pubescent fruits with 13–19 seeds (vs. glabrous fruit containing only 4 seeds).

Type.

China • Guangxi Autonomous Region: Baise City, Napo County, Defu Nature Reserve , bamboo understory on Baxiong Mountain, 1380 m a. s. l., 23.292437°N, 105.784845°E, 8 July 2021, Yonghua Qin YH 2021075 (holotype: PE, isotype: IBK) .

Paratypes.

China • Guangxi Autonomous Region: Baise City, Napo County, Defu Nature Reserve , bamboo understory in evergreen broadleaf forest on southern slope of Baxiong Mountain, 1380 m a. s. l., 23.292451°N, 105.784899°E, 30 May 2023, Yonghua Qin YH 2023069 ( PE, IBK) ; • Baise City, Napo County, Defu Nature Reserve , bamboo understory in evergreen broadleaf forest on the southern slope of Baxiong Mountain, 1380 m a. s. l., 23.292485°N, 105.7847944°E, 7 September 2023, Yonghua Qin YH 2023116 ( PE, IBK) .

Description.

Erect shrub up to 1–2 m tall, with a single main stem; branches flattened, shortly pilosulous, first year branchlets green, becoming brown or grayish-brown with age. Leaves opposite; petiole ca. 1 cm long, pilosulous; leaf blades asymmetrical, papery and blackish-brown when dried, oblong – obovate or oblanceolate, 4–17 cm × 1.5–4 cm, vegetative leaves large, 7–17 cm × 3–4 cm, inflorescence-supporting leaf pairs small, 4–7 cm × 1.5–3.5 cm, adaxially with adnate short hairs, abaxially scabrous and sparsely puberulent to subglabrous, with pubescence denser along principal veins, base cuneate, apex acuminate or shortly acuminate; midrib flat on upper surface, prominent on lower surface; secondary veins in 5–7 pairs, prominent on lower surface; stipules triangular, 3–5 mm, acuminate or apiculate when longer, persistent. Inflorescence corymbose, axillary or sometimes terminal, pendulous, 5–7 cm × ca. 3 cm, 3-5 - or sometimes 9 - flowered, shortly pedunculate, peduncles 3–8 mm, inflorescence axes and pedicels gray strigillose. Rachis unbranched. Flowers opposite on rachis, pedicels 1.5–3.5 cm long, proximal pedicels long, 2.5–3 cm long, distal pedicels short, 1.5–2 cm long. Calyx green, pilosulous; hypanthium portion cylindrical – urceolate, ca. 1 mm long; limb ca. 0.5 mm long, lobed for up to 1 / 2 of length. Corolla white, 1.5–1.9 cm long; tube cylindrical, ca. 5 mm long, inside at the upper part near the throat with dense hairs and at the lower part glabrous or sparsely pubescent, outside glabrous; lobes 5, contorted to the left in bud, oblong, 10–14 × 2–3 mm, with rounded apex, adaxial surface glabrous or sparsely pubescent at base, abaxial surface glabrous. Stamens inserted in corolla throat, alternating with corolla lobes, attached to the throat by a short filament; anthers yellowish-gray, linear, 8–10 mm long, basifixed, twisted after spreading. Style-stigma complex 1–1.2 cm long, exserted for 5–7 mm from corolla tube at anthesis; style sparsely pubescent at the middle; stigma fusiform, acentric apices. Ovary small, usually cup-shaped, 0.5–1 mm long, with 2 locules, each axile placenta with multiple ovules. Fruits berry-like, subglobose, 5–6 mm in diameter, with short persistent calyx teeth or calyx scar at the apex; seeds 13–19 per fruit, elliptic, 3–3.2 × 1.8–2 mm, brownish or black, testa rugose.

Phenology.

Tarenna pendula has been observed to flower from May to July, and to fruit from July to January.

Distribution, habitat, and ecology.

Tarenna pendula grows in southern subtropical evergreen broadleaf forests, particularly in mixed bamboo understory ( Indosasa sinica C. D. Chu & C. S. Chao ), at 1380 m a. s. l. The species is only known from this single locality in Napo County, Guangxi Autonomous Region, China (Fig. 3 ).

Conservation status.

Tarenna pendula is only known from Baxiong Mountain, Defu Nature Reserve, Napo County, Guangxi, China with about 250 individuals recorded to date. Currently the species is only known from a single location. This location is inside a well-protected nature reserve, and as such, the species does not qualify for any threat condition. However, during fieldwork we noticed that the understory of the evergreen broadleaf forests in which T. pendula grows is being colonized by luxuriant bamboo, which may constitute a danger to the new species. A second possible threatening factor for this apparently rare and narrow-ranged species is a limited capacity of natural regeneration. The conservation status for Tarenna pendula thus needs further study. We therefore assess the species as Data Deficient.

Etymology.

The specific epithet is derived from the pendulous inflorescence, which differs from several other Tarenna spp. in the area.

Vernacular name.

Chuixiu wukoushu in Mandarin Chinese, which translates to ‘ pendulous Tarenna ’.

Similar species.

Tarenna pendula is similar to T. tsangii but is easily distinguished by its small form. Further diagnostic morphological characters of the new species and related species are presented in Table 1 . Character information about relevant species is retrieved from Flora of China ( Chen and Taylor 2011).

It is challenging to distinguish different species based on morphological characters alone. However, after carefully scrutinizing the morphological characters of the new species and related species, we found that the new species is easily recognized by its pendulous cymose inflorescences and large number of seeds per fruit. Although T. tsangii has a much larger distribution range than T. pendula , their areas do not overlap. Because the distribution range of T. pendula is immediately adjacent to that of T. tsangii , we hypothesize that these two species may be allopatric. Given the complicated evolutionary relationship among Tarenna species, future studies should investigate the plant diversity and phylogeny of this genus in greater detail.

Figures

Figure 1. Tarenna pendula sp. nov. A flowering branches B portion of inflorescence showing stipule C portion of stem showing stipule D portions of adaxial and abaxial leaf surfaces, (D 1) pressure side of blade, (D 2) low pressure side of blade E flower F stamen G longitudinally opened corolla showing the position of the stamens H pedicel, bracteoles, ovary and calyx I ovary, calyx, style and stigma J fruit K cross section of ovary L longitudinal section of fruit. Drawings by Lijie Zhu, based on type specimens.

Figure 2. Tarenna pendula A habitat B flowering branch C pendulous cyme D flower (D 1) and ovary and calyx (D 2) E longitudinally opened corolla F ovary, calyx, style and stigma G fruiting branch H blade in adaxial view (H 1) and in abaxial view (H 2) I young fruits in different developmental stages J unripe seeds clustered together (after removal of fruit wall) K unripe seeds.

Figure 3. Distribution map of Tarenna pendula (triangle) and Tarenna tsangii (dots).