Phyllanthus huamotensis Pornp., Chantar. & J.Parn., 2019

Pornpongrungrueng, Pimwadee, Chantaranothai, Pranom, Parnell, John A. N. & Hodkinson, Trevor R., 2019, Two new species of Phyllanthus (Phyllanthaceae) from Thailand, PhytoKeys 136, pp. 35-44 : 35

Phyllanthus huamotensis Pornp., Chantar. & J.Parn. sp. nov. Figs 1 , 2

Diagnosis.

Phyllanthus huamotensis is one of the most distinct species of Phyllanthus in Thailand, easily distinguished by its reddish branchlets and stem, conspicuous reddish venation, especially on the lower leaf surface, red sepals with long fimbriate margins and red capsule with a papillose-puberulous surface. It is most similar to P. pulcher Wall. ex Müll.Arg., but differs in its undershrub habit that is up to 30 cm high ( P. pulcher is a shrub up to 1.5 m high), small sized leaves (2-9 × (2 –)3– 8 mm) (leaves in P. pulcher are 7-28 × 6-17 mm) with conspicuous reddish venation (inconspicuous on both leaf surfaces in P. pulcher ) and a red capsule with a papillose-puberulous surface (glabrous in P. pulcher ).

Type.

Thailand. Tak, Umpang district, Doi Hua Mot; 16°2.63'N, 98°51.26'E; alt. 901 m; 22 Aug. 2019; P. Pornpongrungrueng, N. Triyutthachai, S. Ninkaew & S. Sukcharoen 1287 (holotype KKU; isotypes BKF, K, QBG, TCD).

Description.

Undershrubs up to 30 cm high, branchlets and stem reddish, terete, young branchlets minutely puberulous. Stipules triangular-lanceolate, 0.5-1 × 0.3-0.5 mm, glabrous. Leaves alternate; petioles 0.4-0.9 mm long, glabrous; lamina broadly ovate, obovate, rounded, broadly elliptic, ovate-oblong, 2-9 × (2 –)3– 8 mm, subcoriaceous, glabrous on both surfaces, base oblique, cordate, broadly cuneate, truncate, rounded, margin entire, revolute, apex acute, acuminate, rounded; nerves in 4-6 pairs; reticulation reddish, conspicuous, especially on the lower surface. Flowers red, unisexual; staminate flowers 2 –3(– 4) in axillary fascicles in proximal axils; pistillate flower solitary in distal axils. Bracts subulate, 0.2-0.3 × 0.1-0.2 mm, glabrous. Staminate flowers: pedicel 4-10 mm long, glabrous; sepals 4, red, triangular, rhombic-ovate, lanceolate, 1.5-2 × 1-1.2 mm, glabrous, margin long fimbriate; disc glands 4, reniform; stamens 4, staminal column ca. 0.2 mm long, anthers ca. 0.2 mm long, transversely dehiscent. Pistillate flowers: pedicel 7-17 mm long, glabrous; sepals 5-6, red, rhombic-ovate, 1.5-3 × 0.6-1 mm, membranous, glabrous, margin fimbriate; disc glands 5 or 6, free, obovate with truncate apex; ovary superior, ca. 0.7 mm diam., 3-locular, ovules 2 per locule, papillose-puberulous; styles 3, free, ca. 0.1 mm long; stigmas nearly completely bifid, ca. 0.2 mm long, glabrous. Fruits capsule, red, 2.5-3 mm diam., papillose-puberulous; pedicel 7-17 mm long. Seeds trigonous, brown, 1.5-1.8 × 1.1-1.2 mm, surface transversely striate.

Phenology.

Flowering and fruiting period is June to December.

Habitat and distribution.

This species grows on open limestone hills, at 880-937 m above sea level. Currently, it is known only from the type location Doi Huamot, Tak province in northern Thailand.

Conservation status.

The species is only known from the type locality. It should be categorised as Critically endangered [CR, B1ab (iii)] according to the IUCN Red List Criteria and Categories version 3.1 ( IUCN 2012). The extent of occurrence is estimated to be less than 20 km2 and this species is found in a restricted area on open limestone hills which is a threatened ecosystem.

Etymology.

The name of this species is given, based on the location where the plant was first discovered.

Vernacular.

Ma Kham Pom Din Huamot.

Additional specimens examined.

Thailand: Tak, Umpang district, Doi Hua Mot; 15°56.46'N, 98°51.93'E; alt. 937 m; 2 Dec. 2018; P. Pornpongrungrueng, N. Triyutthachai & P. Chantaranothai 1270 (BKF, KKU), ibid.; 15°51.40'N, 98°50.88'E; alt. 882 m; 22 Aug. 2019; P. Pornpongrungrueng, S. Ninkaew, S. Sukcharoen & N. Triyutthachai 1285 (BKF, KKU, TCD).

Figures

Figure 1. Phyllanthus huamotensis Pornp., Chantar. & J. Parn., sp. nov. A habit B, C leaf shapes (B adaxial surface C abaxial surface) D stipule E pistillate flower F staminate flower G mature capsule. Drawn by Pimwadee Pornpongrungrueng.

Figure 2. Phyllanthus huamotensis Pornp., Chantar. & J. Parn., sp. nov. A, B habit C branchlet showing axillary fascicle of staminate flowers D branchlet showing pistillate flower E branchlet showing young red capsule. A Photo by Natthawut Triyuttachai B, C photos by Suchart Chanhomhual D, E photos by Kanokorn Ruengsawang.