Petrocodon luteoflorus Lei Cai & F.Wen, 2020

Fan, Zhi-Wei, Cai, Lei, Yang, Jia-Wen, Tang, Sheng-Hu & Wen, Fang, 2020, Petrocodon luteoflorus (Gesneriaceae), a new species from karst region in Guizhou, China, PhytoKeys 157, pp. 167-173 : 167

Petrocodon luteoflorus Lei Cai & F.Wen sp. nov. Fig. 1

Diagnosis.

Petrocodon luteoflorus most resembles P. dealbatus in plant type and floral size, but can be easily distinguished from the latter by the following diagnostic characters: longer calyx lobes 6-8 mm long (vs. 2-5 mm long); larger corolla 9-11 mm long, pale yellow to yellow (vs. 5.5-8 mm long, white); corolla lobes in equal shape and size, triangular and ca. 2 mm long (vs. in different shape and size: adaxial lobes 0.8-2 mm long, triangular; abaxial lobes 1.8-3 mm long, triangular to ovate).

Type.

CHINA. Guizhou: Libo County, Limingguan Town, Yaolan, 25°17'N, 107°55'E, 735 m a.s.l., on moist rocks under forest, in flower, 23 August 2018, Lei Cai et al. CL193 (holotype: KUN!, isotypes: KUN! & IBK!).

Description.

Perennial herb, stemless. Rhizome 8-12 cm long, 5-12 mm in diameter. Leaves 8-16, basal; petiole 3.5-6.5 cm long, densely pruinate; leaf blade narrow elliptic or oblanceolate, 8-20 × 2.5-8 cm, coriaceous, adaxially green, appressed pubescent, abaxially appressed pubescent along veins, whitish-green, pruinate, base cuneate, gradually tapered to petiole, margin nearly entire to denticulate or crenulate, apex acuminate; lateral veins 4-6 on each side of midrib. Cymes axillary, 1-5 on a plant, flowers numerous, 8-25-flowered or more; peduncle 8-20 cm long, densely puberulent; bracts 2, lanceolate, 8-10 × 1.5-2 mm, both sides puberulent, margin entire, apex obtuse. Pedicel 0.8-2.2 cm long, pubescent. Calyx 6-8 mm long, 5-lobed to the base; lobes equal, linear, 6-8 × 1.5-2.0 mm, outside pubescent, inside glabrous, margin entire to denticulate, apex acuminate. Corolla slightly or inconspicuously 2-lipped, pale yellow to yellow, 9-11 mm long, 4-6 mm in diameter, outside densely puberulent, inside glabrous; tube cannulate, 7-9 × 4-6 mm; adaxial lobes 2, abaxial lobes 3, all lobes triangular, in nearly equal size, ca. 2 mm long, 2.5 mm wide at the base. Filaments ca. 7 mm long, S-shaped, glabrous, inserted ca. 2 mm from base; anthers dorsifixed, ca. 3 mm long, reniform or water-chestnut shaped, apexes acute; staminodes 3, ca. 0.5 mm long, linear, glabrous, inserted ca. 1 mm from base. Disc ca. 1.5 mm high, margin asymmetrical, one side absent, on the other side horned. Pistil ca. 1.5 cm long, glabrous; ovary linear, ca. 6 mm long, style linear, ca. 9 mm long; Stigma discoid, small, 0.3-0.5 mm in diameter. Capsule linear, glabrous, 2-3 cm long.

Phenology.

Flowering from August to September; fruiting from September to November.

Etymology.

The specific epithet ' luteoflorus ' derives from the Latin prefix, luteo -, yellow and the Latin suffix, '- florus ', of flower, referring to its small and yellow flowers of the new species. The Chinese name is "Xiǎo Huáng Huā Shí Shān Jù Tái” (小黄花石山苣苔).

Distribution and habitat.

Petrocodon luteoflorus is currently known only from the type locality and might be endangered but more data are needed to evaluate that reliably. The species only grows on the surface of moist rocks under the forest.

Conservation status.

Current information for this new species is known from only a few collections and details on the size of the population are known in Maolan National Nature Reserve, where the plants’ protected status is guaranteed. Based on some careful field investigations in recent years, this species appears to be locally abundant. Thus, it is assessed temporarily as Least Concern (LC) according to the IUCN Red List Categories and Criteria ( IUCN 2017).

Additional specimens examined.

Guizhou: Libo County, Dongtang Town, Raosuo village, Jiudongtian, 25°17'N, 103°03'E, 795 m a.s.l., on moist rocks at the entrance of limestone caves, 11 September 2017, Fang Wen WF160113-01 (IBK!).

Notes.

At first glance, this new taxon and the type species, Petrocodon dealbatus (Fig. 2 ), could easily have been confused because of its similar leaves if the pruinate abaxial leaf surfaces escaped collectors’ attention or were not in flower. However, once the flowers of the two congeners are compared to each other, they are easy to distinguish. The new species can be easily distinguished from the latter in the shape and length of bracts (lanceolate, 8-10 mm long in P. luteoflorus vs. linear, 3-7 mm long in P. dealbatus ); the length of calyx lobes (6-8 mm long vs. 2-5 mm long); the size and colour of corolla (9-11 mm long, pale yellow to yellow vs. 5.5-8 mm long, white); the shape and size of corolla lobes in equal shape and size: triangular and ca. 2 mm long vs. in different shape and size: adaxial lobes 0.8-2 mm long, triangular; abaxial lobes 1.8-3 mm long, triangular to ovate); indumentum of corolla outside (densely puberulent vs. upper half of corolla puberulent to glabrescent); filaments (S-shaped vs. straight); shape of anthers (reniform or water-chestnut shaped vs. elliptic); the shape and height of disc (ca. 1.5 mm high, asymmetrical, one side absent, on the other side horned vs. ca. 1 mm high, symmetrical and annular).

Figures

Figure 1. Petrocodon luteoflorus Lei Cai & F. Wen, sp. nov. A Habitat B, C plants with flowers D petiole and adaxial leaf surface E petiole and abaxial leaf surface F, G gymes H side view of flower I opened corolla and pistil with calyx J pistil, disc and calyx K opened corolla showing stamens and staminodes L adnate anthers, adaxial view M adnate anthers, abaxial view. Scale bars: 20 cm (A); 10 cm (B, C); 5 cm (D, E); 1 cm (F, G); 5 mm (H, I, J, K), 3 mm (L, M). Photographed by Lei Cai and Fang Wen (D, E).

Figure 2. Petrocodon dealbatus Hance. A Habitat B cyme C the lateral view corolla and calyx lobes D the frontal view of corolla. Photographed by Fang Wen.