Oreocharis argyrophylla W.H.Chen, H.Q.Nguyen & Y.M.Shui

Oreocharis argyrophylla W.H.Chen, H.Q.Nguyen & Y.M.Shui, Gardens’ Bulletin Singapore 69(2): 295–305. 2017 295

Oreocharis argyrophylla W.H.Chen, H.Q.Nguyen & Y.M.Shui; Photos Hoang Thanh Son

The new species is most similar in leaf characteristics to Oreocharis argyreia Chun ex K.Y.Pan but differs from it in having yellow flowers (vs purple), corolla narrowly infundibuliform (vs tubiform) and 2.5–3.1 cm long (vs 2–2.3 cm), and coherent anthers (vs free). In flower characteristics it is also similar to Oreocharis hirsuta Barnett in its yellow and tubular corolla but differs from it in its deeply bilabiate corolla limb (vs shallowly bilabiate) and coherent anthers (vs free). – TYPE: Vietnam, Son La province, Van Ho district, Tan Xuan municipality, Cot Moc village, territory of Xuan Nha nature reserve, eastern slopes of Pha Luong Mountain, at an elevation of 1000–1400 m, 20°40ʹ33.3ʺN 104°39ʹ00.3ʺE, 15 November 2013, in flower, Averyanov, L., Hiep, N.T., Khang, N.S., Thang, N.D. & Qui, L.D. CPC 7175 (holotype KUN; isotypes CPC, LE). 

Description:

Perennial herb with very short stem. Leaves numerous, rosulate, petiolate; petiole 4–9 cm, densely appressed pubescent; blade narrowly obovate to broadly lanceolate, 12–18 × 4.5–6.5 cm, both surfaces densely pubescent with appressed silvery hairs especially adaxially, base narrowly cuneate, apex acute to short acuminate, margin serrulate above middle of leaf blade, lateral veins 6–8 on each side of midrib, distinct.

Inflorescences axillary, 3–4-branched, cymes 3–many-flowered; peduncle 8–12 cm long, pubescent with appressed hairs; bracts 2, linear-lanceolate, 10–13 × 1–2 mm, apex tapering, margin entire, pubescent and villous abaxially, glabrous adaxially; pedicels 0.7–1.8 cm long, white pubescent. Calyx of 5 lobes free to base; lobes equal, linear, 6–8 × c. 1 mm, margin entire, pubescent with appressed hairs abaxially, glabrous adaxially. Corolla yellow, tubular, apically infundibuliform, 2.5–3.1 cm long, outside glandular pubescent, glabrous inside; tube gradually slightly ampliate from the middle, 1.6–2.2 cm long, 2.8–3 mm in diam. at base, 6–6.2 mm in diam. and not constricted at the throat; limb 2-lipped; adaxial lip 2-lobed, dissected from near base of the adaxial lip, lobes ovate, apices rounded or obtuse, 5.8–6 × 4.1–4.3 mm; abaxial lip 3-lobed, lobes ovate, apices rounded or obtuse, subequal, median lobe slightly larger, 7.4–7.5 × 6.1–6.2 mm, lateral lobes 7–7.1 × 4.4–4.7 mm. Stamens 4, anthers coherent in pairs, included, adaxial stamens 8–9 mm long, adnate to corolla tube 1.5–1.6 cm from base, abaxial stamens 1.4–1.5 cm long, adnate to corolla tube 5–5.5 mm from base; filaments glabrous; anthers basifixed, subglobular, 2-locular, dehiscing longitudinally; staminode 1.4–1.5 mm long, adnate to corolla tube 4–5 mm from base. Disc ring-like, c. 1.2 mm long, shallowly 5-lobed. Pistil 1.5–1.6 cm long, glabrous; ovary fusiform, 1.1–1.4 cm long, glabrous, unilocular; style glabrous, 4–5 mm long; stigma 1, peltate. Capsule straight, fusiform, loculicidally dehiscent, 3.3–4 cm long, with persistent style 5–6 mm long. Seeds fusiform, 5–6 × c. 2 mm.

Etymology. 

The specific epithet refers to the silvery leaf indumentum. Ecology, distribution and phenology. The species grows as a lithophytic herb on large moss covered boulders in remnants of primary and secondary broad-leaved evergreen humid forests on very steep mountain slopes composed of shale and sandstone at elevations of 1000–1850 m. This species is only known from the Xuan Nha nature reserve, Son La province of north-western Vietnam, where it is common. Flowering in September–December and fruiting in October–December.

Provisional IUCN conservation status. Endangered EN B1ab(ii,iii,v) + B2ab(ii,iii,v), following IUCN (2012, 2016) guidelines. This is based on an EOO of < 5000 km2 and an AOO of < 500 km2 being known from fewer than five populations, and with evidence of a reduction in the area of occupancy, a decline in habitat quality, and a decline in the number of individuals due to deforestation, largely for agriculture and due to fire.

Additional specimens examined. VIETNAM. Son La: Van Ho district, Chieng Xuan municipality, Co Hong village, territory of Xuan Nha nature reserve, Pha Luong Mountain, 13 Nov 2013, in fruit, Averyanov, L. et al. CPC 7020 (CPC, KUN, LE); Moc Chau Distr., Chieng Son comm., Pha Luong vill., Pha Luong Mountains, 1400–1500 m a.s.l., 20°41ʹ33.2ʺN 104°37ʹ37.0ʺE, 22 Sep 2016, Averyanov, L. et al. CPC 7939 (CPC, LE); Moc Chau Distr., Chieng Son comm., Pha Luong vill., Pha Luong Mountain, 20°40ʹ23.0ʺN 104°37ʹ52.0ʺE, 1750–1850 m a.s.l., 23 Sep 2016, Averyanov, L. et al. CPC 7993 (CPC, LE); Moc Chau Distr., Chieng Son comm., Pha Luong vill., Pha Luong Mountain system, 20°41ʹ30.9"N 104°38ʹ08.9"E, 1425 m a.s.l., 25 Sep 2016, Averyanov, L. et al. CPC 8026 (CPC, E); Van Ho Distr., Tan Xuan comm., A Lay village, around point 20°40ʹ46.2ʺN 104°39ʹ49.6ʺE, approx. 1500 m a.s.l., 1 Oct 2016, Averyanov, L. et al. CPC 8173 (CPC, PE).

Notes. 

The new species is similar to Oreocharis argyreia in its leaf characteristics (silvery indumentum with densely appressed hairs), but can be distinguished easily by its yellow corolla which is also of a different size and shape. The differences between the two species are detailed in Table 1. In Indo-China, Oreocharis argyrophylla is also quite similar to O. hirsuta from northern Thailand in the yellow and tubular corolla, but differs in the densely appressed pubescence on the leaves and the cuneate leaf base (hirsute hairs and obtuse to rounded base in O. hirsuta), more unequal upper and lower corolla lips (subequal lips in O. hirsuta), and anthers coherent in pairs (free in O. hirsuta). 

References

Möller, M., Atkins, H., Bramley, G., Middleton, D., Baines, R., Nguyen, V., . . . Barber, S. (2018). TWO NEW SPECIES OF OREOCHARIS (GESNERIACEAE) FROM NORTHERN VIETNAM. Edinburgh Journal of Botany, 75(3), 309-319. doi:10.1017/S0960428618000148