Swertia hongquanii Jia X. Li, 2019

Li, Jiaxiang, Xu, Yongfu & Zhao, Lijuan, 2019, Swertia hongquanii, a new species of Gentianaceae from Mt. Wuling, southern China, PhytoKeys 132, pp. 1-10 : 1

Swertia hongquanii Jia X. Li sp. nov. Figs 1 , 2 , 3

Diagnosis.

The new species is similar to Swertia bimaculata , but differs from the latter by its leaf blades ovate to ovate-cordate, 2.0-4.5 × 1.0-2.5 cm with base cordate and subamplexicaul (vs. broadly elliptic to ovate-lanceolate, 3.5-9 × 1.0-4 cm with base tapered to obtuse), and its seeds irregularly polyhedral with minutely thorny and reticulate seed coat (vs. globose with seed coat finely warty) (Table 1 ).

Type.

CHINA. Hunan province: Zhangjiajie City, Mt. Tianmen, 29°3'N, 110°28'E, elev. 1400 m, 23 September 2016, J. X. Li 092502 (holotype CSFI, bar code: CSFI063656; isotypes CSFI, IBSC, PE).

Description.

Biennial herbs, 2-40 cm tall. Roots yellow, fibrous. Stems erect, sometimes branched from the lower part, subquadrangular, 1-3 mm in diam., with narrow wings on angles. Basal leaves quickly withering, blades elliptic to obovate, 1-3.5 × 0.8-3 cm, apex obtuse, base cuneate and decurrent, veins yellow-white, distinct, pinnate; petioles flattened, winged, ca. 0.5-2.5 cm long. Stem leaves sessile or shortly petiolate, leaf blades ovate to ovate-cordate, apex acute, base cordate and subamplexicaul, 2.0-4.5 × 1.0-2.5 cm, smaller towards stem apex, veins 3-5, arcuate, distinct, green or yellow-green.

Inflorescence a panicle of cymes, lax, 5 –20(– 25) × 4-20 cm, few- or many-flowered; axes spreading. Flowers (4-)5-merous. Pedicels spreading to erect, slender, subquadrangular, 0.6-4 cm. Calyx 1/2 to 2/3 as long as corolla, tube 1-2 mm long, lobes narrowly elliptic, 3-6 mm long, with 3 slender and distinct veins, apex acute. Flowers to 2.0 cm in diam.; corolla white with purple spots on the upper half of the lobes adaxially but less visible abaxially, tube 1-2 mm long; lobes elliptic-lanceolate, 0.5-1.0 × 0.2-0.4 cm, widest at the middle, apex acuminate to acute. Nectaries 2 per corolla lobe, situated in the middle of corolla lobe, semi-circular, reduced to a naked gland patch without raised margin, yellow-green. Stamens with filaments ca. 4 mm long, white; anthers ellipsoid, ca. 1.5 mm long, purple. Style short, ca. 0.5 mm long; stigma lobes capitate. Capsules narrowly ovoid, to 1.3 cm long. Seeds polyhedral, compressed irregularly, with distinct angles, ca. 1.0 × 0.5 mm, dark brown; seed coat minutely thorny and reticulate.

Phenology.

Flowering was observed in September and October. Fruiting was only observed in November, but probably extends till December.

Distribution and habitat.

Swertia hongquanii is known only from the type location in Tianmenshan National Forest Park. The climate here is cool, foggy and humid (annual rainfall ca. 1700 mm) and belongs to the subtropical monsoon climate ( Li et al. 2008; Zhang et al. 2015). The new species grows on the tops of steep limestone mountains surrounded by cliffs above an altitude of ca. 1400 m. The clifftops are covered by mixed evergreen-deciduous forest dominated by species of Fagaceae , Lauraceae , Betulaceae , Aceraceae and Ulmaceae ( Li et al. 2008). One population occurs in the crevices of limestone cliffs; it is covered by shrubs and herbs with little soil but is rich in humus. It is accompanied by Viola davidii Franch., Youngia Cass. sp., Thalictrum ichangense Lecoy. ex Oliv., Aster ageratoides Turcz., Calamagrostis arundinacea (L.) Roth, Carex filicina Nees, Carex L. sp., Leptopus chinensis (Bunge) Pojark., Zanthoxylum bungeanum Maxim., Rubus innominatus S.Moore var. kuntzeanus (Hemsl.) L.H.Bailey, Rubus henryi Hemsl. & Kuntze, Salix mictotricha C.K.Schneid., Carpinus dayongiana K.W.Liu & Q.Z.Lin and Betula chinensis Maxim. Another population grows in the herb layer of forest dominated by Quercus multinervis (W.C.Cheng & T.Hong) Govaerts and Hovenia dulcis Thunb. with deep and fertile soil. Other herbaceous species are Ophiopogon japonicus (Thunb.) Ker Gawl., Carex gibba Wahlenb., Sanicula orthacantha S.Moore, Pimpinella diversifolia DC. and Viola diffusa Ging.

Etymology.

The species is named after Mr. Huang Hongquan for his help during our field investigation. He was also the first to collect this new species.

Local name.

Tianmenshan Zhang Ya Cai

Conservation status.

Despite several investigations in Mt. Tianmen and the surrounding areas (96 km2), two populations with nearly 500 individuals each (total <1000) of Swertia hongquanii were found only at the type locality (towering summit terrace with an area of 2 km2). Presently, a tourist plank walkway passes through this location and its habitat could be easily disturbed or destroyed. According to the IUCN (2017) criterion D thresholds (mature individuals <1000, AOO <20 km2), the new species could be assessed as VU. However, it grows in the upper part of steep limestone mountains surrounded by cliffs, which previously made it impossible to be encountered until a plank walkway was built across the cliff face for tourists. With limited fieldwork executed at present, it is possible that more populations could be found in similar habitats of the Wuling mountain areas. Therefore, we consider the species DD (Data Deficient).

Additional specimens examined.

CHINA: Hunan, Zhangjiajie City, Mt. Tianmen, 20 September 2013, 29°3'N, 110°28'E, limestone, 1400 m alt., Hongquan Huang 13050406 (CSFI); the same locality, 20 November 2017, Hongquan Huang HHQ02 (CSFI); the same locality, 25 September 2017, J.X. Li 092503 (CSFI).

Figures

Figure 1. Swertia hongquanii A seedlings showing basal leaves B root C flowering plant D flower showing corolla, nectaries, stamens and pistil E capsule F seeds. Drawn by Jing Tian.

Figure 2. Habitat and morphology of Swertia hongquanii. A-B Habitat C flowering plant D seedlings showing basal leaves E adaxial view of flower showing calyx, corolla, nectaries, stamens and pistil F abaxial view of flower showing calyx and corolla G stem with a pair of leaves H flowering and fruiting plant; centrally, a capsule with persistent corolla can be seen. Photos: Jiaxiang Li.

Figure 3. Seeds of Swertia hongquanii. Scale bars: 1 mm (A); 0.5 mm (B); 0.2 mm (C); 0.3 mm (D-F). Photos: Jiaxiang Li.