Lasianthus bidoupensis V.S. Dang & Naiki (2019: 191)

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

4. Lasianthus bidoupensis V.S. Dang & Naiki (2019: 191) — Fig. 18 (plate), Fig. 15 (map)

Type: — VIETNAM. Lam Dong Province, Bidoup Nui Ba National Park, 50 km northeast of Dalat City , 1436 m elev., 10 February 2018, Dang V.S. & Hoang N.S., Dang 250 (holotype VNM! [ VNM00042870 ]; isotypes HN!, VNMN!, VNM! [ VNM00042871 , VNM00042872 ]) .

Specimens examined: — VIETNAM. Central: Lam Dong Province, Bidoup Nui Ba National Park, 50 km northeast of Dalat City, 1436 m elev., 11 February 2018, Dang V.S. & Hoang N.S., Dang 250a ( VNM, the herbarium of Iriomote Station (Japan )); in the same location, 1490 m elev., 19 November 2014, Toyama H., Tagane S., Dang V.S., Nagamasu H., Naiki A., Tran H., Yang C.J. V1839 & V4364 ( FU, VNM, the herbarium of Iriomote Station (Japan )); in the same location, 1438 m elev., 26 November 2017, in moist evergreen forest, Naiki A. & Dang V.S. N10098 ( VNM, the herbarium of Iriomote Station (Japan)) .

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

Habitat & Ecology: —Growing in evergreen forest at 1400–1500 m elev. in Bidoup Nui Ba National Park, Lam Dong Province, southern Vietnam. This species was collected in the understory of forest dominated by Fagaceae , Fabaceae , Rubiaceae , Lauraceae , Myrtaceae , Symplocaceae and Clusiaceae .

Phenology: —Flowering and fruiting from November to February of the next year.

Vernacular name: —Xú hưƠng bidoup.

Notes: — Lasianthus bidoupensis was described in 2018 from our collections (Dang 250). It can easily be recognized by having elliptic-oblong to elliptic-lanceolate leaf blades, secondary veins 6–7 on each side of midrib, flowers fascicular, pinkish white to white, and fruits ovoid or ellipsoid, deep red when ripe.

This species is closely related to L. yaharae V.S.Dang, Tagane & H.Tran (2015: 352) and L. dalatensis Wernham (1921: 138) based on leaf morphology, deeply dissected calyx lobes and cylindrical corolla, but differs from them in having larger leaves and bracts, longer petioles, stipules, calyx, and corolla tubes. Fruit color is also different when ripe. It is also similar to L. inodorus Blume (1826: 998) but differs from the latter in having larger bracts (5–8 mm vs. 3–6 mm long) and longer calyx tubes (4–5 mm vs. 2 mm long).

Figures

FIGURE 15. Distribution maps of Lasianthus annamicus, L. attenuatus, L. bachmaensis and L. bidoupensis.

FIGURE 18. Lasianthus bidoupensis V.S.Dang & Naiki (from Dang 250, VNM and the herbarium of Iriomote Station (Japan)): A. Branch with flower buds, B. Stipules, C. Abaxial leaf surfaces, D–F. Inflorescence showing lateral view bracts and flowers, G. Young fruit, H. Mature fruits, I. Cross section of fruit with 5 pyrenes.