Vietnam. Thua Thien Hue Province, Nam Dong District, Thuong Lo Commune, Bach Ma National Park, on moist rocks under evergreen broad-leaved forests, 16°07'56.5"N 107°45'03.2"E, ca. 545 m alt., 21 Nov 2019, Do Van Truong ĐVT 368 (holotype: VNMN!; isotypes: IBK!, VNMN!).

Figure 1. 

Holotype of Oreocharis phuongii sp. nov. (Truong Van Do ĐVT 368, deposited at VNMN).

The new species is morphologically similar to O. longifolia W.H.Chen in having peduncles up to 22 cm long, bracts 2, zygomorphic, yellow flowers with tubular corolla, stamens 4 and capsules up to 6 cm long; but it differs from the latter in its elliptic to ovate lamina (vs. narrowly elliptic to oblanceolate), cuneate to nearly rounded leaf base (vs. attenuate), obtuse to almost rounded leaf apex (vs. acute), crenulate margin (vs. serrulate), 3–4.5 × 1.5–1.8 mm calyx lobe size (vs. 5–7 × 2–3 mm), glabrous inner surface of corolla tube (vs. sparsely glandular puberulent with dark-purple striations) and exclusively yellow inner surface of three lower lobes without dots and striations (vs. brown to brownish-yellow with purple dots and striations).

Perennial acaulescent herbs, with conspicuous 12–14 cm long stolons, densely brown woolly, with (6–)8–14 leaves in a basal rosette. Petioles 1–3 cm long, densely brown villous. Leaf-blade elliptic to ovate, 4–7 × 2–2.8 cm, base cuneate to nearly rounded, apex obtuse to almost rounded, margin crenulate, adaxially dark-green, densely grey puberulous, abaxially pale-green, densely grey puberulous and browner appressed villous on main veins, secondary veins pinnate, 4–5 pairs, tertiary veins reticulate, lightly sunken on adaxial surface and conspicuously prominent on abaxial surface. Inflorescences cymose, subumbel-like, axillary, 2–3 cymes, each 1–3-flowered; peduncles 12–19(–22) cm long, erect, brown, sparsely villous to pubescent; bracts 2, linear-lanceolate to elliptic, 2–5 × 1.5–2 mm, outside with sparse, brown hairs, inside glabrescent, margin entire; pedicels 2–3 cm long, with sparse, brown hairs, sometimes bearing additional bracts at 1/2 to upper 1/3 of pedicel length, similar in size and morphology with bracts at branching points. Calyx equally 5-lobed, free to base, lobes triangular to lanceolate, 3–4.5 × 1.5–1.8 mm, both surfaces with a dense covering of long gland-tipped and eglandular hairs, margin entire. Corolla, zygomorphic, yellow, bilabiate, outside sparsely pubescent, inside glabrous; tube tubular, 28–30 × 12–13 mm, abrubtly constricted at base, 8–9 × 2.5–3 mm; upper lip slightly 2-lobed; lobes ovate, 5–7 × 4.5–5 mm, incurved backwards, apex obtuse to acute; lower lip 3-lobed, lobes elliptic, broadly ovate to semi-orbicular; lateral lobes 8–9 × 5–6 mm; middle lobe broader than lateral lobes, 8–10 × 6–7.5 mm, apex obtuse to acute or rounded. Stamens 4, anthers coherent in two pairs, filaments linear, glabrous; filaments of upper pair 15–17 mm long, adnate at 7–8 mm from the base of corolla tube; filaments of lower pair 1.1–1.3 cm long, adnate at 9–10 mm from the base of corolla tube; anthers reniform, 1–1.5 mm long, basifixed, glabrous; staminode absent. Disc ca. 1.3 mm in height, margin orbicular, glabrous. Pistil 21–26 mm long; ovary ca. 2.5 mm long, ca. 1 mm in diam., glabrescent; style 17–22 mm long, ca. 1 mm in diam., pubescent, longer than upper pair of filaments when mature; stigma bilobed, V-shaped, 1–1.5 mm long, glabrous. Capsules linear-oblong, straight, 5–6(–8) × ca. 0.3 cm, glabrous to glabrescent, loculicidal.

Figure 2. 

Oreocharis phuongii sp. nov. (A–J) A habitat B habit showing cymose inflorescence C adaxial leaf surface D abaxial leaf surface E–F structure of floral parts (two pairs of anther and filament indicated by a white arrow; shape of pistil indicated by a green arrow) G frontal view of opened flower showing backwards incurved upper lobes, glabrous inner surface of three lower lobes and a bilobed matured stigma longer than stamens (indicated by a blue arrow) H lateral view of opened flower I close-up of opened flower (in frontal view) J close-up of 2-paired stamens; O. longifolia (K–M) K habit L frontal view of opened flower showing brown to brownish-yellow inner surface of three lower lobes with dark-purple striations M lateral view of an opened flower. A–J photos by Do Van Truong K–M photos by Nicholas Turland.

The specific epithet honours Prof. Dr. Vu Xuan Phuong who has contributed significantly to our understanding of Gesneriaceae in Vietnam.

Flowering was observed from October to November. Fruiting may occur from November to December.

The new species is currently known from some protected forest areas (viz. Dakrong Nature Reserve, Quang Tri Province and Bach Ma National Park, Thua Thien Hue Province) within the Annamite Range, central Vietnam (Fig. 3). The new species grows on moist shady cliffs on the humus-rich limestone hills and moist rocks under evergreen broad-leaved forests, at elevations of 360–650 m.

Figure 3. 

Distribution of Oreocharis phuongii sp. nov. from central Vietnam (shown by black stars).

Two large-sized populations of Oreocharis phuongii were found in the core-zones of Dakrong Nature Reserve, Quang Tri Province and Bach Ma National Park, Thua Thien Hue Province, central Vietnam, which are almost entirely covered by primary forest and are well protected. Furthermore, our field observations of these populations indicated that there are many healthy individuals and seedlings that regenerate in well-protected habitats and there is no immediate threat to the populations from human activities. Thus, the new species is probably not at risk in the near future. This species is preliminarily assessed as Least Concern (LC) according to the IUCN Categories and Criteria (IUCN Standards and Petitions Subcommittee 2019).

In the size and shape of the corolla and the structure of inflorescences, O. phuongii is similar to some species with the acaulescent and rosette-forming stems of the formerly circumscribed Briggsia, which previously comprised ca. 30 species and four varieties and was mainly distributed in Bhutan, China, India, Myanmar and Vietnam (Wang et al. 1990, 1998; Vu 2018). Nineteen species and four varieties of acaulescent, rosette forming Briggsia (Craib 1920; Pan 1988) were moved to Oreocharis s.l. in a later revision (Möller et al. 2011, 2014). Of which, O. phuongii is most similar to O. longifolia (Craib) Mich.Möller & A.Weber in having peduncles up to 22 cm long, bracts 2, zygomorphic, yellow flowers with tubular corolla, stamen 4 with two pairs of coherent anthers and capsules up to 6 cm long, but it clearly differs from the latter in the shape of leaf blade, leaf base, leaf apex, leaf margin, number of flowers, shape and size of calyx lobes, inner surface of corolla tube and inner surface of three lower corolla lobes. Detailed morphological comparisons of the new species with O. longifolia are shown in Table 1 and Figure 2.

This new species is the first record of the genus Oreocharis occurring in central Vietnam, which raised the species number of Oreocharis in Vietnam to nine. Amongst the nine known Oreocharis species from Vietnam, the new species shares the yellow to orange corolla with five other species: O. aurea, O. argyrophylla, O. grandiflora, O. longituba and O. tribracteata (Chen et al. 2017, 2018; Möller et al. 2018). However, it is clearly different from these five species by having a tubular corolla tube (vs. funnel to narrowly funnel corolla tube in O. argyrophylla, O. grandiflora, O. longituba, O. tribracteata and urceolate corolla tube in O. aurea). Jin et al. (2021) showed that Oreocharis sl. could be separated into two clades: Clade A was mainly distributed in SW China and predominantly showed yellow to orange corollas; Clade B was mainly distributed in S and SE China and predominantly showed purple corollas, of which, Clade A includes ca. 20 species. In order to facilitate identification, a key to five yellow to orange species of Oreocharis in Vietnam is provided.

Vietnam. Quang Tri Province, Dakrong District, Dakrong Nature Reserve, on moist shady cliffs on the humus-rich limestone hills, 16°29'50.97"N, 107°00'09.25"E, 650 m alt., 18 Oct 2019, Do Van Truong ĐVT 362 (VNMN).