Perilimnastes, Ridley, 1918

Souvannakhoummane, Keooudone, Lamxay, Vichith, Lanorsavanh, Soulivanh & Liu, Ying, 2024, Perilimnastes aura (Sonerileae, Melastomataceae), a new species from Dak Cheung Plateau, Sekong province, Southern Laos, Phytotaxa 670 (1), pp. 77-82 : 78

Perilimnastes aura Souvann. & Lamxay, sp. nov. ( Figures 1 , 2 , and 3).

Type:— LAOS. Sekong province, Dakcheung district, Dakleun village, Phou Kong King Mountain, Evergreen forest, 15°28’25.0”N 107°09’42.2”E, 1,655 m elevation, 26 April 2023, V. Lamxay, S.Lanorsavanh, K.Souvannakhoummane, K. Phommasy, P. Phommachan. WF 109 (holotype HNL, isotypes FOF, KKU).

Perilimnastes aura closely resembles P. suberalata in the unequal leaves, and glabrescent, oblanceolate to broadly elliptic lamina, but differs in the acute leaf apex (vs. acuminate), 1–3-flowered inflorescence (vs. 1-flowered), quadrangular hypanthium (vs. obtusely quadrangular) and broadly triangular, 1.8–2.2 mm long calyx lobes (vs. linear, 8–10 mm long).

Description:—Small shrubs up to 100 cm tall, with druses in many parts of the plant. Stems erect to ascending and multi-branched, quadrangular, glabrous when young, old stems woody and slightly verrucose. Leaves opposite, subequal or distinctly unequal; petioles 2.5–8 cm long, grooved above; lamina oblanceolate to broadly elliptic, 2.0–7.2 × 1.0– 2.8 cm, thin papery, adaxial surface waxy, dark green, sometimes reddish, abaxial surface pale green, glabrescent to glabrous, 3-veined, secondary veins 7–18 on each side of midvein, base cuneate, margin entire to serrate near apex, apex acute. Inflorescence a terminal cyme,1–3-flowered, peduncle 3.0– 4.5 cm long, quadrangular, green to red, glabrescent to puberulent; bracts minute triangular, 1–2 mm long, glabrous, brownish. Flowers bisexual, radial but androecium slightly bilateral; pedicels 8.4– 1.2 cm, purplish, glabrescent to puberulent; hypanthium cup-shaped, ca. 4.5–5.4 × 2.5–3.2 mm, pale green to pink, glabrescent; calyx lobes 4, broadly triangular, 1.8–2.2 × 2.2–2.5 mm, keeled, abaxial surface reddish-brown with dark green apex, glabrous, adaxial surface pale green to white, glabrous; petals 4, thick, orbicular to broadly elliptic, 0.8–1.2 × 0.9–1.1 cm, pink to white, margin undulate to entire, apex oblique and obtuse, both surfaces glabrous; stamens 8 in 2-whorls, isomorphic, subequal in length, filaments 5–8 mm long, bent with the anthers to one side of the flower, anthers narrowly lanceolate, 4–6 mm long, purplish, connectives pale yellow, forming a 0.5 mm long, dorsal spur and 2 ventral lobes; style 0.9–1.6 cm long, white, glabrous; ovary half inferior, locules 4, ovary with a membranous crown. Capsule 5–8 × 4–6 mm, cup-shaped, quadrangular; hypanthium 8-ribbed; placentation column 4-horned, placentas thready.

Habitat and Phenology:—Terrestrial or lithophytes growing in evergreen cloud forests on mountain slope from 1,500 to 1,800 m elevation, with 3–4 hours of sunshine per day. The soil is moist clay loam mixed with stones and the temperature ranges from 16–23 degrees Celsius. Flowering from March to July and fruiting from June to October.

Distributed: —Known only from Phou Kong King Mountain in Dakcheung district, Sekong province, Southern Laos.

Etymology: —The epithet refers to smooth wind and year-round pleasant weather in the habitat of P. aura.

Vernacular name: —ເອັນອ້າບັງບົດ [En-R Bung Bod]

Preliminary conservation status: — Perilimnastes aura is only know from Phou Kong King Mountain, Sekong province, Laos. According to field survey, the only population consists of about 1,000 individuals, including mature individuals and seedlings. Numerous seedlings were observed growing near the mature plants. No specific threats have been identified as this area is sparsely populated with low level of habitat disturbance. The Phou Kong King Mountain Area, which covers approximately 100 km 2, is considered as the extent of occurrence (EOO) for this species. Therefore, the new species should be classified as Vulnerable (Vu) under criteria D of the IUCN Red List Categories and Criteria ( IUCN, 2024).

Figures

FIGURE 1. Perilimnastes aura, A. Habit. B. White flower. C. Pink flower. D. Lateral view of flower. E. Druses (as white spots) on adaxial surface. F. Lateral view of old capsule. G. Longitudinal section of an old capsule showing enlarged ovary crown and morphology of the placental column and placentas. Photo: A–D by S. Lanorsavanh and E–G by K. Souvannakhoummane.

FIGURE 2. Perilimnastes aura, A.Abaxial view of a leaf. B. The tip of a branchlet showing the adaxial surfaces of a pair of unequal leaves and a young capsule. C.Adaxial surface of a petal. D.Abaxial surface of a petal. E, H–J. Lateral view of flowers, showing the morphology of flower bud, hypanthium, and anthers. F. Flowers bud. G. Flower. Photo: K. Souvannakhoummane.