﻿Staurantherafloribunda, a new species of Gesneriaceae from Yunnan, China

﻿Abstract Staurantherafloribunda F.Su, C.Y.Hao & K.Tan, a new species of Gesneriaceae from Yunnan, China, is described and illustrated here. It is morphologically similar to S.grandifolia Benth. in the shape of corolla, stigma, leaves and the number of stamens. However, it can be readily distinguished from the compared species by its dense cymes, leaf indumentum, lack of a corolla spur, calyx colour and stamen shape. The description of the new species, photographs, detailed descriptions, notes on etymology, distribution and habitat, as well as comparisons with morphologically similar species, are provided.


Introduction
Stauranthera Benth.( 1835) is a genus of perennial herbs in Gesneriaceae.Originally, this genus was established, based on the species S. grandifolia Benth.from the Malay Peninsula.The genus has previously been considered to comprise ca. 13 species distributed in Northeast India and South China throughout Malesia to New Guinea (Willis 1973;Burtt 1984).However, the taxonomic delimitation of the genus Stauranthera has been revised considerably over time, with S. brandisii C.B.Clarke being moved into Rhynchotechum Blume, Stauranthera johannis-winkleri Kraenzl.was synonymised with S. argyrescens Hallier f., S. chiritiflora Oliver and S. tsiangiana Hand-Mazz.were transferred to the new genus Whytockia W.W.Sm. in which Stauranthera chiritiflora is the type of Whytockia (Smith 1919;Burtt 1984).Merrill (1923) synonymised both Stauranthera ecalcarata R.Br. and S. philippinensis Elmer with S. caerulea (Blume) Merr.(Merrill 1923).Currently, the genus comprises ca.five species recognised by Möller et al. (2016), with two of them being recorded in China, namely S. umbrosa (Griffith) C.B.Clarke in Guangxi, Hainan and Yunnan and S. grandifolia Benth. in Yunnan and Hainan (Zhu et al. 1996;Qin and Xing 2006;Wei 2018;Wen et al. 2019;Huang and Liu 2023), respectively.Meanwhile, these two species were also documented in northern Vietnam, a region bordering the distribution area of Stauranthera in China (Wei et al. 2022).Additionally, S. coerulea (Blume) Merr., a Malesian species, was also introduced to northern Vietnam (Wei et al. 2022).
During a floristic expedition to Yunnan Province in 2022, the authors found an unknown species of Gesneriaceae near the Sino-Vietnamese border at Jinping County, China.Based on features like opposite, unequal leaves, small opposite bracts, a campanulate corolla tube with a basal spur, an indistinctly 2-lipped limb with a 2-lobed adaxial lip and 3-lobed abaxial lip, four included stamens and basifixed anthers connate into a shallow cone, this species appears to belong to the genus Stauranthera.However, detailed morphological comparisons to protologues and type specimens of all previously-described Stauranthera species revealed it does not match any known species.Thus, we confirmed that it as a new species, described and illustrated here as S. floribunda F.Su, C.Y.Hao & K.Tan.We provide a formal description of the new species and an updated key for the genus in China.

Materials and methods
Morphological studies of the new species were based on the type specimens deposited in the Herbaria IBK and NPH and the living plants cultivated in the Spice and Beverage Research Institute, CATAS and Gesneriad Conservation Centre of China (GCCC).All available specimens of Stauranthera stored in the Herbaria AU, BM, E, G, HITBC, IBK, IBSC, K, KUN, PE and WU were examined from online specimen images via the Chinese Virtual Herbarium (CVH, https://www.cvh.ac.cn/index.php)and JSTOR (https://plants.jstor.org).Measurements of morphological characters were based on living plants whose photographs were taken with a Nikon D750 digital camera (Tokyo, Japan) and Dino-Lite digital microscope (Taiwan, China) and the morphological characters described using the terminology presented by Wang (1990) and Wang et al. (1998).Morphological comparison with close species was based on consultation with published literature.The conservation status evaluations of the new species S. floribunda were based on the International Union for Conservation of Nature Guidelines (IUCN 2022).Diagnosis.The new species resembles Stauranthera grandifolia in leaf blade shape and corolla, but can be easily distinguished from the latter in the flower number of cymes 2-4 bushes (vs.cymes 1-2 bushes), calyx colour white to slightly purple (vs.green), and bract 1, bracteole 1 auriculate connate (vs.bracts 2, linear opposite) and ovary 1-loculed (vs.2-loculed) (Table 1).Description.Perennial Herbs, terrestrial, not rhizomatous, up to 35 cm high.Stem 6-28 cm tall, 5-12 mm in diam., puce, pulverulent.Leaves opposite, usually three pairs, occasionally five pairs, with a normal leaf and a degenerated leaf at the internode, leaf blade strongly oblique, oblong to elliptic obovate, 14-28 cm long, 6-15 cm wide at the middle, apex acuminate, base cuneate on narrow side, broadly cuneate to rounded on wider side, margin nearly entire, adaxially glabrous, abaxially including leaf veins papillose-puberulent, lateral veins 10-13 on the narrow side; 13-20 on the wider side; petiole 4-6 cm long, ca. 4 mm in diam., puberulous; degenerated leaves, sessile, adaxially green, abaxially greenish, pubescent, cordate to auricular-cordate to auricular-renifor, 2-4 mm long, 8-12 mm wide, margin entire, apex retuse or emarginate, leaf vein 3 pairs.Inflorescence dichotomous cyme, emerging from the axils of the large leaves, 3-9 cymes per plant, dense flowers, 10-20, rare 5 flowers per cyme, peduncles, pedicels, bracts, calyx densely white pubescent, sticky, peduncle up to 18 cm high; pedicels 1.5-2 cm long; bract 1, bracteole 1, green, auriculate connated; calyx broadly campanulate, ca. 2 cm in diam., white to slightly purple, 5-lobed, lobes deltoid, margin entire, longitudinally wrinkled between lobes.Corolla slightly obliquely campanulate, purple or bluish-purple, throat yellowish; corolla tube ca. 5 mm long, orifice ca. 4 mm in diam., upper lip ca. 8 mm long, 2-lobed, lobes suborbicular, ca. 4 mm in diam.,  other, dorsal septum slightly raised.Pistil ca. 9 mm; Ovary yellowish, subuliform, ca. 5 mm long, ca. 4 mm in diam., 1-located glandular puberulent about the position from the top to 1/3 of the ovary, the rest of ovary glabrous; Style ca. 3 mm long, linear, sparsely glandular-puberulent from the bottom to 2/3 of the style, the rest of style glabrous; stigma 1, covered densely brownish puberulent hairs.Capsule globose to oblatoid, glabrous, brownish-purple when young, brownish-black when mature.Phenology.Flowering in May and fruiting from June to July.

Taxonomy
Etymology.The specific epithet floribunda, which means "many-flowered", refers the large numbers of the flowers per cyme and the whole plant of the new species.Preliminary conservation status.Since the only known population of Stauranthera floribunda is in the Rubber Forest of Jinshuihe Town, Jinping County, south Yunnan Province, we have not discovered the wild population expected from the above-mentioned location and information known about the population status and natural distribution range of the new species is very limited.Currently, less than 150 individuals have been found in the Rubber Forest.The new species of population, which grows close to a country road, is potentially threatened by human activities.Although no such habitat destruction is currently occurring, this population will likely be threatened in the foreseeable future under the influences of artificial factors, such as rubber cutting.Considering the known population is surrounded by rubber forests, it might survive under strong man-made intervention.Therefore, we suggest that the new species S. floribunda should be considered 'Critically Endangered' [CR, B2a,b (iii,iv,v)], facing a relatively high risk of extinction in the wild) according to current IUCN Red List Categories and Criteria (IUCN 2022).

Figure 1 .
Figure 1.Stauranthera floribunda F.Su, C.Y.Hao & K.Tan, sp.nov.A habit B cymes C, D adaxial and abaxial views of the whole plant E degenerated leaves F front view of flower G back view of flower H detail of abaxial leaf blade I detail of stamens J detail of pistil K ovary and its cross-section view.Photographs by Fan Su.

Figure 2 .
Figure 2. Line drawing of Stauranthera floribunda F.Su, C.Y.Hao & K.Tan A adaxial view of the whole plant B front view of flower C back view of flower D detail of degenerated leaves E pistil F hair of abaxial leaf blade G frontal view of stamens H dorsal side of stamen.Drawn by Di Hu.

Table 1 .
Morphological comparison of key characteristics in S. floribunda and S. grandifolia.