Lasianthus hongiaoensis V.S.Dang & Naiki (2021: 32)

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

32. Lasianthus hongiaoensis V.S.Dang & Naiki (2021: 32) — Fig. 55 (plate), Fig 52 (map)

Type: — VIETNAM. Lam Dong Province, Bidoup Nui Ba National Park , 1698 m elev., 24 February 2016, Tagane S., Nagamasu H., Naiki A., Dang V.S., Nguyen V.N., Wai J. V 4318 (holotype VNM![ VNM00042898 ]; isotypes FU!, VNM! [ VNM00042899 , VNM00042900 ], the herbarium of Iriomote Station ( Japan)) .

Specimens examined: — VIETNAM. Central: Lam Dong Province, Bidoup Nui Ba National Park , 1698 m elev., 12°09’52.95’’N, 108°32’00.38’’E, in hill evergreen forests, 24 February 2016, Tagane S., Nagamasu H., Naiki A., Dang V.S., Nguyen V.N., Wai J. V 4318 ( FU, VNM, the herbarium of Iriomote Station ( Japan)); in the same location, 1490 m elev., 12°10’26.91’’N, 108°41’53.94’’E, in evergreen forests, 19 February 2014, Toyama H., Tagane S., Dang V.S., Nagamasu H., Naiki A., Tran H., Yang C.J. with Ngoc N.V., Cuong N.Q., Hieu H.N.P., Loi X.N. V1842 ( FU, VNM, the herbarium of Iriomote Station ( Japan)) .

Distribution: —Endemic to Vietnam (known only from the Bidoup Nui Ba National Park, Lam Dong Province).

Habitat & Ecology: —In hill evergreen forest at around 1400–1700 m elev.

Phenology: —Flowering and fruiting from February to June.

Vernacular name: —Xú hưƠng hòn giao.

Note: — Lasianthus hongiaoensis is morphologically similar to L. hispidulus (Drake) Pit. (1924: 382) in the shape of leaves, flower color at anthesis, and blue fruits, but differs from the latter in having densely pubescent at branches and branchlets (vs. densely brown-villous), longer stipules (1–1.5 mm long vs. 1 mm long) and larger calyx (1.5–2 mm long vs. 1–1.5 mm long for tubes and 1.5–2 mm long vs. 1–1.5 mm long for lobes).

It is also similar to L. nuichuaensis V.S.Dang & Naiki which was described from Nui Chua National Park, Ninh Thuan Province, Southern Vietnam, but differs from the latter by having plants covered by densely pubescent (vs. glabrous), larger leaves (7–9 × 2.5–3.5 cm vs. 5–7 × 1.5–3 cm), fewer secondary veins (4–5 on each side of midrib vs. 5–6 on each side of midrib), larger calyx lobes (1.5–2 mm long vs. 0.5–1 mm long) and fruits with 5 (vs. 4) pyrenes.

Figures

FIGURE 52. Distribution maps of Lasianthus hirsutus, L. hispidulus, L. honbaensis and L. hongiaoensis.

FIGURE 55. Lasianthus hongiaoensis V.S.Dang & Naiki (from V4318, VNM): A. Branch with fruits, B. Close-up of expanding young leaves, C. Stipules, D. Abaxial leaf surfaces, E. Flower buds and young fruit, F. Inflorescence showing side view flowers, G–H. Fruits, J. Seeds (E–F: photos by Shuichiro Tagane).