Sonerila tenasserimensis J. Wai

11. Sonerila tenasserimensis J. Wai & J.-M. Hu, sp. nov. (Figures 22, 23).

TYPE:— THAILAND. SOUTH-WESTERN: Kanchanaburi Province, Thong Pha Phum

District, Thong Pha Phum National Park, 14°41’4.40” N, 98°26’0.80” E, 800 m, 2 November 2015, M. Poopath et al. 1367 (holotype PSU!, isotypes BKF!, TAI!).

Diagnosis: Sonerila tenasserimensis is morphologically most similar to S. picta Korthals (1844:249) in having subshrub habit, quadrangular stems and often with white spots on leaves, but differs by the densely canescent or rusty brown pubescence on peduncles, pedicels, and hypanthia (vs. absent), longer petals (8–11 mm long vs. 6–7.5 mm) and longer stamen filaments (filaments 6.5–8 mm long vs. 3.5–5 mm).

Perennial herbs or subshrubs, 10–60 cm high; stems erect or ascending, quadrangular, simple or branched, semi-woody in older parts, 2–3.5 mm thick, densely canescent or rusty brown pubescent mixed with few long stipitate glandular trichomes (trichomes ca. 0.25 mm long); internodes 0.5–3 cm long. Leaves opposite decussate, isomorphic, light green to dark green or reddish purple, often with numerous white spots, membranaceous when dry; petioles 0.5–4.5 cm long; blades elliptic, ovate or lanceolate, 3–9 × 1–4 cm, 1.5–3 times as long as wide, adaxially sparsely minutely strigose, abaxially sparsely minutely strigose along secondary veins, apex acute to acuminate, base equal or oblique, cuneate, rounded to cordate, margin shallowly serrulate; venation pinnate; primary vein shallowly grooved above, prominent beneath, densely covered with minute, rusty brown pubescent and mixed with scattered long stipitate glandular trichomes; secondary veins arising from both sides of primary vein in an alternate or occasionally sub-opposite manner, 2–3 pairs. Inflorescences terminal or axillary, scorpioid cymes, 5–20-flowered, densely pubescent with scattered long stipitate glandular trichomes on peduncles, pedicels and hypanthia; peduncles erect or slightly curved, 1–2 cm long, green or purplish; bracts minute, narrowly triangular, 0.25–0.35 mm long. Flowers 3-merous; pedicels 2–4 mm long, purplish. Hypanthium cylindrical-campanulate or obconical, 5.5–7 × 2–2.5 mm, purplish or greenish; part of hypanthium free from ovary 2.5–3 mm long. Calyx lobes 3, triangular-ovate, 1–1.5 × ca. 2 mm. Petals short-clawed, elliptic, elliptic-ovate or elliptic-oblong, 8–11 × 4.5–6 mm, apex acuminate, pinkish, adaxially glabrous, abaxially glandular pilose along the midvein. Stamens 3, equal, glabrous; filaments 6.5–8 mm long, pinkish or white; anthers slightly incurved, deeply cordate at base, narrowing towards apex, 6.5–7.5 mm long, yellow, apex opening with two pores. Ovary 2.5–4 mm long, 3-locular; ovary crown 1–1.5 mm high; ovules numerous; style 12–15 mm long, pinkish; stigma capitate, papillate. Capsule obpyramidal, trigonous, 5–6.5 × 3.5–4 mm, minutely pubescent or sometimes glabrescent. Seeds numerous, triangular ovoid, 0.4–0.5 mm long, 0.2–0.3 mm wide, ca. 0.2 mm thick (measured through SEM), dark brown; testa cells densely verrucose-papillose, with minute tubercles on antiraphal side.

Paratypes:— THAILAND. NORTHERN: Kamphaeng Phet Province, Klong Lan District, 1290 m, 15 December 1998, M. van de Bult 193 (CMUB!); Pang Sila Thong District, Chong Yen, 16°06’07.8” N, 99°06’23.4” E, 1408 m, 6 November 2015, M. Poopath et al. 1413 (BKF!, PSU!, TAI!). SOUTH-WESTERN: Kanchanaburi Province, Thong Pha Phum District, Ban E-Tong, Pilok, 21 February 1967, C. Chermsirivattana 681 (BK!); ibid., 10 December 1969, C. Chermsirivattana 1580 (BK!); ibid., 21 November 1997, K. Chayamarit 1013 (BKF!); ibid., 14°41’1.50” N, 98°21’43.00” E, 900 m, 3 November 2015, M. Poopath et al. 1371 (PSU!); Thong Pha Phum National Park, 700–970 m, 26 January 1983, H. Koyama et al. T32941 (KYO!); ibid., 14°41’37” N, 98°24’ 17” E, 925 m, 15 October 2013, C. I. Peng et al. 24192 (HAST).

Distribution:— Thailand (Kanchanaburi and Kamphaeng Phet Provinces). It might be also found across the border in Myanmar.

Habitat:— Terrestrial plant. This species was found growing in shaded areas of lowland to submontane forests, at elevations of 700–1450 m.

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

DNA barcodes:— OP431265 (ITS), OP453060 (ETS), OP480548 (accD-psal), OP452984 (ndhF), OP503778 (trnS-trnG). All sequenced from M. Poopath et al. 1367.

Etymology:— The specific epithet “tenasserimensis” refers to the type locality, the Tenasserim range where this species has been found.

Vernacular name:—สาวสนมตะนาวศรี (Sao Sanom Tanao Si) (Thailand).

Proposed IUCN conservation status:— Endangered (EN) under criteria B1ab (iii)+B2ab (iii). This species is known only from three locations near Thai-Myanmar border. The known extent of occurrence (EOO) is less than 5,000 km 2 and the known area of occupancy (AOO) is less than 500 km 2. Since some populations are very close to the road, they can be affected by human disturbance. Therefore, we qualify this species as EN according to IUCN Red List guidelines Version 15.1 (IUCN Standards and Petitions Committee 2022).