Lasianthus lacduongensis V.S.Dang & Naiki (2021: 42)

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

40. Lasianthus lacduongensis V.S.Dang & Naiki (2021: 42) — Fig. 65 (plate), Fig. 62 (map)

Type: — VIETNAM. Lam Dong Province, Bidoup Nui Ba National Park, 1490 m elev., 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. V1840 (holotype VNM! [ VNM00042910 ]; isotypes FU!, VNM! [ VNM00042911 , VNM00042912 ], the herbarium of Iriomote Station (Japan)) .

Specimens examined: — VIETNAM. Central: Lam Dong Province, Bidoup Nui Ba National Park, 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. V1840 ( 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. V1930 ( FU, VNM, the herbarium of Iriomote Station (Japan)). Khanh Hoa Province, Hon Ba Nature Reserve , 1533 m elev., 12°07’01.82’’N, 108°56’43.63’’E, in evergreen forests, 25 November 2014, Toyama H., Tagane S., Dang V.S., Nagamasu H., Naiki A., Tran H., Yang C.J. with Cuong N.Q., Hieu H.N.P. V2160 ( FU, VNM, the herbarium of Iriomote Station (Japan )) .

Distribution: —Endemic to Vietnam (known from the Hon Ba Nature Reserve in Khanh Hoa Province and Bidoup Nui Ba National Park in Lam Dong Province).

Habitat & Ecology: —In evergreen forests at 1200–1600 m elev.

Phenology: —Flowering and fruiting from February to November.

Vernacular name: —Xú hưƠng lạc dưƠng.

Notes: — Lasianthus lacduongensis is similar to L. membranaceoideus H. Zhu (2012: 62) which is endemic to Borneo in having the shape of leaves and bracts inconspicuous, but differs from the latter in having sparsely tomentose on young branches (vs. glabrous), more secondary veins (8–10 on each side of midrib vs. 6–8 on each side of midrib), shorter petioles (5–7 mm long vs. 6–10 mm long), and fruits with 2 (vs. 4) pyrenes.

Lasianthus lacduongensis was previously recognized by Dang et al. (2019) based on the specimen Dang 193 (VNM) as a new record of “ L. membranaceoideus H.Zhu ” for the flora of Vietnam. However, after careful examination of morphological and molecular evidence, it is L. lacduogensis V.S.Dang & Naiki.

Figures

FIGURE 62. Distribution maps of Lasianthus khanhvinhensis, L. konchurangensis, L. kontumensis and L. lacduongensis.

FIGURE 65. Lasianthus lacduongensis V.S.Dang & Naiki (from V1840, VNM): A. Branch, B. Close-up of young branch and leaves, C. Stipules, D. Abaxial leaf surfaces, E–F. Young fruits, H–I. Mature fruit, J. Seeds.