Lasianthus nuichuaensis V.S.Dang & Naiki (2021: 17)

Dang, Van-Son & Naiki, Akiyo, 2023, A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam, Phytotaxa 581 (1), pp. 1921-1935 : 1921-1935

53. Lasianthus nuichuaensis V.S.Dang & Naiki (2021: 17) — Fig. 81 (plate), Fig. 78 (map)

Type: — VIETNAM. Ninh Thuan Province, Nui Chua National Park, 260 m elev., 16 August 2019, Dang V.S. & Naiki A., Dang 404 (holotype VNM! [ VNM00042926 ]; isotypes VNM! [ VNM00042927 , VNM00042928 ], the herbarium of Iriomote Station (Japan)) .

Specimens examined: — VIETNAM. Central: Ninh Thuan Province, Nui Chua National Park, 260 m elev., 11°44’06.53’’N, 109°13’15.12’’E, in secondary forest, 16 August 2019, Dang V.S. & Naiki A., Dang 404 ( VNM, the herbarium of Iriomote Station (Japan )); in the same location, 256 m elev., 11°44’06.51’’N, 109°13’15.11’’E, in secondary forest, 01 December 2017, Dang V.S. & Naiki A. N10147 ( KYO, VNM, the herbarium of Iriomote Station (Japan)) .

Distribution: —Endemic to Vietnam (known only from the Nui Chua National Park, Ninh Thuan Province).

Habitat & Ecology: — This species is only known from the type locality in Nui Chua National Park , Ninh Thuan Province, southern Vietnam where it grows under the shade of the secondary forest at an elevation between 200–300 m.

Phenology: —Flowering from June to September, fruiting from October to December

Vernacular name: —Xú hưƠng núi chúa.

Notes: — Lasianthus nuichuaensis is closely related to L. hispidulus (Drake) Pit. (1924: 382) in the shape of leaves, the number of secondary veins and inflorescences, but differs from the latter by having glabrous branches (vs. densely brown-villous), smaller leaves (5–7 × 1.5–3 cm vs. 7–10 × 3–5 cm), bracts 1–1.5 mm long (vs. absent), calyx and corolla lobes 4 (vs. lobes 5), orange fruits (vs. blue) and drupe with 4 pyrenes (vs. 5 pyrenes).

Figures

FIGURE 78. Distribution maps of Lasianthus nghiasonii, L. nhatrangensis, L. ngoclinhensis, L. nuichuaensis and L. oblongilobus.

FIGURE 81. Lasianthus nuichuaensis V.S.Dang & Naiki (from Dang 404, VNM): A. Fruiting branch, B. Stipules, C. Abaxial leaf surfaces, D–F. Close-up of inflorescences and flowers, G–H. Close-up of immature and mature fruits, I. Seeds.