5. Sonerila montana J. Wai & J.-M. Hu, sp. nov. (Figures 10, 11).

TYPE:— THAILAND. NORTHERN: Chiang Mai Province, Chom Thong District, Near Doi Inthanon National Park Check Point 2, 18°31’39.79”N, 98°29’57.84”E, 1690 m, 11 December 2015, K. Khammongkol et al. 74 (holotype PSU!, isotypes BKF!, TAI!).

Diagnosis: Sonerila montana is morphologically most similar to S. parishii Stapf (1982: 303) in having terete stems and isophyllous leaves, but differs by the scattered bristles on stems (vs. absent), shorter petals (7–9.5 mm long vs. 10–11 mm), smaller anthers (ca. 6.5 mm long vs. 7–8 mm).

Perennial herbs or subshrubs, 10–30 cm high; stems erect or ascending, simple or branched, slender, terete, semi-woody in older parts, 2–3 mm thick, almost all parts densely covered with minute brown glandular trichomes mixed with scattered bristles ca. 1 mm long, young parts usually reddish purple, old parts turn to grayish brown; internodes 1–3.5 cm long. Leaves opposite decussate, isomorphic, light to dark green or reddish purple, sometimes with numerous white spots, chartaceous or submembranaceous when dry; petioles 0.5–4 cm long; blades ovate or lanceolate, 3–10.5 × 2–3.7 cm, 1.5–2.8 times as long as wide, adaxially sparsely minutely strigose, abaxially sparsely minutely strigose along veins, apex acute to acuminate, base equal or slightly oblique, cuneate to rounded, truncate or slightly cordate, margin shallowly serrulate; venation pinnate; primary vein shallowly grooved above, prominent beneath; secondary veins arising from both sides of primary vein in an alternate or sub-opposite manner, 2–4 pairs. Inflorescences terminal or axillary, scorpioid cymes, 3–10-flowered, with scattered minute transparent brown glandular trichomes (seen under magnification) mixed with scattered long stipitate glandular trichomes on peduncles, pedicels and hypanthia; peduncles erect or slightly curved, 2–5 cm long, green or purplish; bracts minute, triangular, 0.25–0.75 mm long. Flowers 3- merous; pedicels 3.5–6 mm long, purplish. Hypanthium obpyramidal or obconical, 6–7 × 2.5–3 mm, purplish or greenish; part of hypanthium free from ovary 2.5–3.5 mm long. Calyx lobes 3, triangular-ovate, 1–1.5 × 2–2.5 mm. Petals short-clawed, elliptic or obovate, 7–9.5 × 4–6 mm, apex acuminate, pinkish, adaxially glabrous, abaxially glandular pilose along the midvein. Stamens 3, equal, glabrous; filaments 6.5–10 mm long, pinkish or white; anthers slightly incurved, deeply cordate at base, narrowing towards apex, ca. 6.5 mm long, yellow, apex opening with two pores. Ovary 3–4 mm long, 3-locular; ovary crown ca. 1 mm high; ovules numerous; style 11–16 mm long, pinkish; stigma capitate, papillate. Capsule obpyramidal, trigonous, 5–7 × 4–5 mm, with minute trichomes or glabrescent. Seeds numerous, triangular ovoid, 0.6–0.7 mm long, 0.3–0.4 mm wide, 0.25–0.3 mm thick (measured through SEM), dark brown; testa cells densely verrucose-papillose, with prominent tubercles on antiraphal side; tubercles dome-shaped, minutely verrucose-papillose.

Paratypes:— THAILAND. NORTHERN: Mae Hong Son Province, Mueang Mae Hong Son District, Doi Khun Huai Pong, 18°58’ N, 98°10’ E, 1800 m, 5 March 1968, B. Hansen & T. Smitinand 12828 (C!, E!, K!, L!); Pang Mapha District, Doi Chong, 19°25’ N, 98°18’ E, 1800 m, 19 February 1968, B. Hansen & T. Smitinand 12671 (AAU!, C!, E!, K!, KYO!, L!, P!). Chiang Mai Province, Chom Thong District, Doi Angka, 1550 m, 20 December 1934, H. B. G. Garrett 914 (E!, L!); ibid., 1550 m, 20 December 1934, H. B. G. Garrett 915 (E!, L!); Mae Chaem District, Doi Inthanon, 2400 m, 20 December 1965, M. Tagawa et al. T3058 (AAU!, E!, K!, KYO!, L!); ibid., 18°40’ N, 98°25’ E, 1700 m, 7 December 1969, C. F. van Beusekom & C. Phengklai 2379 (AAU!, E!, L!); ibid., 2300 m, 31 December 1974, R. Geesink et al. 7989 (L!); ibid., 1900 m, 3 January 1975, R. Geesink et al. 8062 (C!, K!, L!, P!); ibid., 1680 m, 19 December 1983, N. Fukuoka & M. Ito T35340 (KYO!, L!); ibid., 1600 m, 5 December 1984, S. Mitsuta et al. T45317 (KYO!); ibid., 2000 m, 5 December 1984, H. Koyama et al. T48806 (BKF!); ibid., 1750 m, 13 December 1984, W. Nanakorn 1096 (AAU!); ibid., 1800 m, 13 December 1984, W. Nanakorn 1110 (AAU!); ibid., 18 October 1991, O. Thaithong et al. 294 (BCU!); ibid., 1600 m, 29 November 1991, R. Pooma 612 (BKF!, CMUB!); ibid., 1500–1700 m, 30 January 1996, W. Nanakorn et al. 5901 (QBG!); ibid., 1700 m, 23 December 1996, M. Hara A091 (CMUB!); ibid., 1800 m, 15 December 1996, W. Nanakorn et al. 8261 (QBG!); ibid., 2 January 1997, M. Hara A348 (CMUB!); ibid., 3 January 1997, M. Hara A392 (CMUB!); ibid., 7 January 1998, P. Srisanga & W. Pongamornkul 110 (QBG!) ibid., 7 January 1998, P. Srisanga & W. Pongamornkul 111 (QBG!); ibid., 1600 m, 6 January 2009, S. Watthana 2706 (QBG!); ibid., 6 January 2009, S. Watthana 2707 (QBG!); ibid., Route to Khun Wang, 1650 m, 20 January 2009, P. Srisanga & P. Suksathan 3248 (QBG!) ibid., 20 January 2009, P. Srisanga & P. Suksathan 3261 (QBG!); ibid., 18°31’14.00” N, 98°30’7.00” E, 1652 m, 27 November 2011, V. Chamchumroon et al. 5175 (AAU!, L!); Omkoi District, Doi Mon Chong, 1400–2000 m, 1 January 1997, W. Nanakorn et al. 8336 (QBG!).

Distribution:— Thailand (Mae Hong Son and Chiang Mai Provinces).

Habitat:— Terrestrial plant. This species was often found growing in shaded areas of montane forest, at elevations of 1400–2400 m.

Phenology:— Flowering and fruiting were observed from October to March.

DNA barcodes:— OP431215 (ITS), OP453037 (ETS), OP480513 (accD-psal), OP452963 (ndhF), OP480649 (rpl16),OP503759 (trnS-trnG), OP558246 (ndhC-trnV),OP495559(ndhF-rpl32).All sequenced from K.Khammongkol et al. 74.

Etymology:— The specific epithet “montana” refers to the mountain habitat of this species.

Vernacular name:—สาวสนมดอย (Sao Sanom Doi) (Thailand).

Proposed IUCN conservation status:— Vulnerable (VU) under criteria B1ab (iii)+B2ab (iii). This species is narrowly distributed in Northern Thailand. The known extent of occurrence (EOO) is less than 20,000 km 2 and the known area of occupancy (AOO) is less than 2,000 km 2. Since they are particularly attractive to collectors and some populations are very close to the road, they can be affected by human disturbance. Therefore, we qualify this species as VU according to IUCN Red List guidelines Version 15.1 (IUCN Standards and Petitions Committee 2022).