Phyllanthus chantaranothaii Pornp., J.Parn. & Hodk., 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 chantaranothaii Pornp., J.Parn. & Hodk. sp. nov. Figs 3 , 4

Diagnosis.

Phyllanthus chantaranothaii is most similar to P. pulcher , but differs in its puberulous upper leaf surface with white, simple and dendritic hairs and pistillate flowers that have red, narrowly lanceolate sepals with a white long fimbriate margin, puberulous on the outer side and puberulous pedicel, whereas in P. pulcher , the leaf is glabrous on both surfaces and the sepals of the pistillate flower are rhombic-ovate with the upper part greenish and lower part red, glabrous on the outside and glabrous pedicel.

Type.

Thailand. Tak, Umpang district, Pa La Ta waterfall, 15°49.14'N, 98°51.37'E, alt. ca. 500 m, 23 Aug. 2019, P. Pornpongrungrueng, S. Ninkaew, S. Sukcharoen & N. Triyutthachai 1291 (holotype KKU; isotypes BKF, K, QBG, TCD).

Description.

Small shrubs up to 80 cm high, branchlets terete, young branchlets puberulous with white, simple and dendritic hairs. Stipules lanceolate-subulate, 1.4-2 × 0.1-0.4 mm, glabrous. Leaves alternate; petioles ca. 0.5 mm long, glabrous; lamina oblong, obovate, 1-2.1 × 0.5-0.8 cm, membranous, upper surface puberulous with white, simple and dendritic hairs, lower surface glabrous, base oblique, margin entire, revolute, apex mucronate; nerves in 4-7 pairs; reticulation inconspicuous on both surfaces. Flowers unisexual; staminate flowers 2-3 in axillary fascicles along lower half of the branchlets; pistillate flower solitary in leaf-axils along upper half of the branchlets. Bracts subulate, 0.6-1.4 × ca. 0.2 mm, puberulous-glabrous. Staminate flowers: pedicel 5-11 mm long, glabrous; sepals 4, red, triangular, rhombic-ovate, 2-3 × ca. 1 mm, glabrous, margin white 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 8-11 mm long, puberulous; sepals 6, reddish, narrowly lanceolate, 3-3.5 × 0.5-0.8 mm, outer surface puberulous, margin white long fimbriate; disc glands 6, free, obovate with truncate apex; ovary superior, ca. 1 mm diam., 3-locular, ovules 2 per locule, glabrous or papillose; styles 3, free, ca. 0.1 mm long; stigmas nearly completely bifid, 0.4-0.6 mm long, glabrous. Fruits capsule, young capsule white to pale greenish, 2.5-4 mm diam., glabrous or papillose; pedicel 5-13 mm long. Seeds trigonous, brown, 1.5-2 × 1-1.3 mm, surface transversely striate.

Phenology.

Flowering and fruiting from August to November.

Habitat and distribution.

This species grows in mixed deciduous forest, at ca. 500 m elevation. It is currently known from the type location near Pa La Ta waterfall and Doi Huamot, Tak province, Thailand.

Conservation status.

As only the type collection, which was collected from mixed deciduous forest, has been investigated in detail, more field exploration in similar habitats in the surrounding areas should be conducted in order to provide a more accurate distribution range of this species. However, based on information that is available to us, this species is preliminarily categorised here as Endangered [EN, B1ab(i, iv)], according to the IUCN Red List Criteria and Categories version 3.1 ( IUCN 2012). The extent of occurrence is estimated to be less than 50 km2 and, previously, it was found in two locations (Doi Huamot and Pa La Ta waterfall in Umpang district, Tak province), but recently, the extent of occurrence seems to be in decline, because the species has not been found in Doi Huamot since it was first photographed in November 2008.

Etymology.

The name of this species honours Prof. Dr. Pranom Chantaranothai for his major contributions to plant taxonomy, in general, but especially for his extensive work on Phyllanthus in the Flora of Thailand.

Vernacular.

Mayom Noi.

Figures

Figure 3. Phyllanthus chantaranothaii Pornp., J. Parn. & Hodk., sp. nov. A habit B, C leaf shapes (B adaxial surface C abaxial surface) D stipule E pistillate flower F staminate flower G young capsule H mature capsule. Drawn by Pimwadee Pornpongrungrueng.

Figure 4. Phyllanthus chantaranothaii Pornp., J. Parn. & Hodk., sp. nov. A habit B branchlet showing axillary fascicle of staminate flowers C branchlet showing pistillate flower D branchlet showing young capsule E branchlet showing mature capsule. A-C photos by Natthawut Triyuttachai D, E photos by Siriyakorn Sukcharoen.