Lasianthus sonlangensis V. S. Dang, Vuong & Quan 2022, sp. nov.
Creators: name: Dang, Minh Quan
name: Nguyen, Manh Ha
name: Hoang, Nghia Son
name: Le, Van Tho
name: Nguyen, Thi Mai Huong
name: Ho, Nguyen Quynh Chi
name: Truong, Ba Vuong
name: Dang, Van Son
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Rubiaceae
Lasianthus
Lasianthus sonlangensis

description: Lasianthus sonlangensis V.S.Dang, Vuong & Quan sp. nov.
urn:lsid:ipni.org:names:77295608-1
Figs 4–5; Table 2
Diagnosis
Lasianthus sonlangensis sp. nov. is morphologically similar to L. caeruleus Pitard (Fig. 6) which is endemic to Vietnam in the shape of leaves and inflorescences, but differs from the latter by having secondary veins 5–7 pairs (vs 4–5 pairs), petioles 2–3 mm long (vs 4–5 mm long), bracts present 0.6– 1 mm long (vs absent), calyx tube 1.5–2 mm long (vs ca 1 mm long), calyx lobes 0.7–1 mm long (vs ca 0.5 mm long) and corolla lobes 4 (vs 5). For a further comparison see Table 2.
Etymology
The specific epithet is derived from commune ʻSƠn Langʼ where the new species was discovered.
Vernacular name
Xú hƯƠng ʻSƠn Langʼ.
Type material
VIETNAM • Gia Lai Province, K’Bang District, Son Lang Commune, Kon Chu Rang Nature Reserve, primary evergreen forests; 14°29′15.08″ N, 108°32′11.10″ E; at 900–1100 m a.s.l.; 24 Apr. 2021; Van-Son Dang, Ba Vuong Truong, Minh Quan Dang & Nghia Son Hoang Dang 465; holotype: VNM!; isotypes: HN!, VNM!.
Description
Shrubs, evergreen, up to 1 m tall; branches and branchlets slender, 1–1.5 mm diam., glabrous, internodes 1.5–2.5 cm long. Leaves opposite, blades oblong to oblong-laceolate, 5–7 × 1–1.5 cm, coriaceous, yellowish brown when dry, glabrous on both sides, apex acute to acuminate, aristate 0.7–1 mm long, glabrous, base acute, margin entire; midrib slightly prominent adaxially, prominent abaxially; secondary veins 5–7 pairs, ascending at an angle of 60–75° from midrib, curved to the margin, flat adaxially, slighly prominent abaxially; tertiary veins subparallel to subreticulate; petioles 2–3 mm long, grabrous. Stipules triangular, 0.8–1 mm long, persistent, glabrous except barbate margin. Inflorescences cymose, sessile, 1–9-flowered; bracts small, 0.6–1 mm long, glabrous except barbate margin. Flowers sessile; calyx campanulate, 2–3 mm long, white to whitish purple, calyx tube 1.5–2 mm long, glabrous, calyx lobes 4, linear-triangular, 0.5–1 mm long, glabrous except barbate margin; corolla tube cylindrical, 8–9 mm long, white, corolla tube 6–7 mm long, puberulous outside in upper part, corolla lobes 4, triangular, 1.5–2 mm long, puberulous outside, floccose inside in the throat; stamens 4, filaments short, anthers oblong, 1–1.2 mm long; ovary with 4–5 locules, style linear, 7–8 mm long, stigma lobes 4, 0.4–0.7 mm long. Fruits not seen.
Distribution, habitat and phenology
Lasianthus sonlangensis sp. nov. was discovered in Kon Chu Rang Nature Reserve, Gia Lai Province, southern Vietnam. It occurs in the understory of primary evergreen forest together with Lasianthus hirsutus (Roxb.) Merr. (Rubiaceae Juss.), Ardisia perpendicularis E.Walker (Primulaceae Batsch ex Borkh.), Mischocarpus sundaicus Blume (Sapindaceae Juss.), Pterospermum mucronatum Tardieu (Malvaceae Juss.) and Trivalvaria costata (Hook.f. & Thomson) I.M.Turner (Annonaceae Juss.), at 900–1100 m elevation. Flowering specimens were collected in April.
Population and threats
Lasianthus sonlangensis sp. nov. is currently known from only one locality with a small population of less than 10 individuals. The forest habitat where we found this species is frequently disturbed by anthropogenic factors, such as spontaneous tourism activities and collection of non-timber forest products (NTFPs).
description: Published as part of Dang, Minh Quan, Nguyen, Manh Ha, Hoang, Nghia Son, Le, Van Tho, Nguyen, Thi Mai Huong, Ho, Nguyen Quynh Chi, Truong, Ba Vuong & Dang, Van Son, 2022, Two new species of Lasianthus Jack (Rubiaceae) from southern Vietnam, pp. 19-31 in European Journal of Taxonomy 806 on pages 25-29, DOI: 10.5852/ejt.2022.806.1697, http://zenodo.org/record/6373945