Lasianthus sonlangensis V.S.Dang, Vuong & Quan, 2022

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, European Journal of Taxonomy 806, pp. 19-31 : 25-29

publication ID	https://doi.org/ 10.5852/ejt.2022.806.1697
DOI	https://doi.org/10.5281/zenodo.6379962
persistent identifier	https://treatment.plazi.org/id/0387F954-292C-FF86-FE6A-172AFE0DCCCC
treatment provided by	Felipe
scientific name	Lasianthus sonlangensis V.S.Dang, Vuong & Quan
status	sp. nov.

Treatment

Lasianthus sonlangensis V.S.Dang, Vuong & Quan sp. nov.

urn:lsid:ipni.org:names:77295608-1

Figs 4–5 View Fig View Fig ; Table 2 View Table 2

Diagnosis

Lasianthus sonlangensis sp. nov. is morphologically similar to L. caeruleus Pitard ( Fig. 6 View Fig ) 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 View 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!; GoogleMaps isotypes: HN!, VNM GoogleMaps !.

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).