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 | Phyllanthus huamotensis Pornp., Chantar. & J.Parn.
in Pornpongrungrueng, Chantaranothai, Parnell & Hodkinson, 2019. |
Abstract Two Phyllanthus species are newly described from a limestone mountain in the north of Thailand. The first species, P. huamotensis Pornp., Chantar. & J.Parn., sp. nov., is one of the most distinct Phyllanthus species easily distinguished by its reddish branchlets and stem, conspicuous reddish venation, especially on the lower leaf surface, red sepals with long fimbriate margin and red capsule with papillose-puberulous surface. The second species, P. chantaranothaii Pornp., J.Parn. & Hodk., sp. nov., is similar to P. pulcher Wall. ex Müll.Arg., but it is distinguished by its puberulous upper leaf surface and pistillate flowers which have red, narrowly lanceolate sepals with a white, long fimbriate margin, puberulous outer side as well as puberulous pedicel.
Keywords: diversity, Euphorbiaceae, new taxa, revision, taxonomy
 | 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. |
Phyllanthus huamotensis Pornp., Chantar. & J.Parn., sp. nov.
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).
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.
Etymology: The name of this species is given, based on the location where the plant was first discovered.
Vernacular: Ma Kham Pom Din Huamot - มะขามป้อมดอยหัวหมด.
 | 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. |
Phyllanthus chantaranothaii Pornp., J.Parn. & Hodk., sp. nov.
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.
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. 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 - มะยมน้อย.
Pimwadee Pornpongrungrueng, Pranom Chantaranothai, John A.N. Parnell and Trevor R. Hodkinson. 2019. Two New Species of Phyllanthus (Phyllanthaceae) from Thailand. PhytoKeys. 136: 35-44. DOI: 10.3897/phytokeys.136.47625
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