Petrocodon dahuaensis M. L. Mo, Chen Feng & Z. C. Lu sp. nov.

Figs 3, 4

Chinese name.

dà huà shí shān jù tái (大化石山苣苔).

Diagnostic.

The new species is similar to Petrocodon asterostriatus F. Wen, Y. G. Wei & W. C. Chou, but differs by its leaf blades cordate to subrounded, margin crenate or serrate (vs. broadly ovate to subcordate, margin entire), bracts 4–9 mm long (vs. 10–25 mm long), bracteoles ca. 2 mm long (vs. 9–18 mm long), calyx 5–7 mm long (vs. 8–16 mm long), corolla purple (vs. pale purplish-maroon), base straight to slightly inflated (vs. near spherical), filaments purple (vs. white), and style densely glandular-puberulent (vs. densely puberulent).

Type.

China • Guangxi: Hechi City, Dahua County, Qibainong Township, Nongteng Village, 24.06°N, 107.68°E, growing on moist rock surfaces at the entrance of a karst cave, alt. 480 m, 13 July 2023, Xu et al. 16041 (holotype: IBK 00470616, isotypes: IBSC and PE).

Description.

Perennial herb. Rhizome erect or ascending, 1–5 cm long, 7–15 mm in diam. Leaves 8–18, basal. Petiole green to reddish brown, densely pubescent, 6–20 cm long. Leaf blade papery, cordate to subrounded, margin crenate or serrate, 4–10 × 4–12 cm, apex obtuse, base cordate; adaxial side deeply green, pubescent; abaxial side pale green, pubescent, densely pubescent along the veins; lateral veins 4–5 on each side of the midrib. Cymes 4–8, axillary, 1–2 - branched, 4–10 - flowered or more; peduncle green to reddish brown, 3.5–11.6 cm long, densely pubescent; bracts 2, opposite, green with reddish brown at base, ovate to ovate-lanceolate, apex acute, margin entire, 4–9 × 1.2–2.5 mm, both surfaces densely pubescent; bracteoles 2, opposite, elliptic, ca. 2 × 0.5 mm, color and indumentum similar to bracts. Pedicel green, 4–6 mm long, ca. 1 mm in diam., densely pubescent. Calyx 5 - parted to base, green to reddish brown, lanceolate to linear-lanceolate, 5–7 × 1.2–2.1 mm, densely pubescent on both surfaces. Corolla purple, zygomorphic, 3–3.5 cm long, base straight to slightly inflated, outside puberulent and sparsely glandular-puberulent, inside glabrous with deep purple longitudinal stripes; tube infundibuliform, ca. 17 mm long, ca. 3 mm in diam. at base, ca. 7 mm in diam. at tube opening; limb 2 - lipped; adaxial lip 2 - lobed, triangular to narrowly triangular, lobes ca. 5 mm long, ca. 4 mm wide at base, margin entire, apex acuminate; abaxial lip 3 - lobed to more than middle, narrowly lanceolate to narrowly triangular, lobes ca. 9 mm long, 4–5 mm wide at base, margin entire, apex acuminate. Stamens 2, adnate to 8–10 mm above corolla tube base; filaments straight, purple, 5–6 mm long, sparsely puberulent from the base to above middle, distally with sparse glandular puberulence; anthers pale brownish yellow, reniform, ca. 1.2 mm long, glabrous, coherent face to face. Staminodes 3, glabrous, adnate to 7–9 mm above corolla tube base, lateral ones ca. 1.5 mm long, middle one ca. 1 mm long. Disc annular, ca. 1 mm high, margin entire. Pistil ca. 1.6 cm long; ovary cylindrical, 4.5 mm long, 1–1.4 mm in diam., densely pubescent; style ca. 12 mm long, ca. 0.6 mm in diam., densely glandular-puberulent; stigma bilobed, lobes ovate, ca. 0.5 mm long. Capsules linear, straight, 0.9–1.1 cm long, densely puberulent, 4 - valved.

Etymology.

The specific epithet “ dahuaensis ” refers to the type locality of this new species.

Phenology.

Flowering from June to July.

Distribution and habitat.

Petrocodon dahuaensis is endemic in Guangxi, China, and is currently known only from the type locality. It grows on shaded and moist rock surfaces at the northeast-facing entrance of karst caves, at an altitude of about 500 m. The new species is dominant in the herbaceous layer of this small habitat. Associated plants include Begonia sp., Boehmeria nivea (L.) Gaudich., Elatostema sp., Iodes cirrhosa Turcz., Pothos chinensis (Raf.) Merr., Selaginella uncinata (Desv.) Spring, and Zenia insignis Chun, among others.

Additional specimens examined (paratypes).

China • Guangxi: Hechi City, Dahua County, Qibainong Township, Nongteng Village, 24.06°N, 107.68°E, growing on moist rock surfaces at the entrance of a karst cave, alt. 480 m, 11 March 2023, Xu et al. 15539 (IBK).

Provisional conservation status.

Currently, Petrocodon dahuaensis is known only from the type locality, with a total number of individuals less than 50. As further surveys across its potential distribution are lacking, the existence of other populations remains unclear. Therefore, P. dahuaensis is provisionally classified as Data Deficient (DD), according to the IUCN Red List Categories and Criteria (IUCN 2022).