A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam Author Dang, Van-Son 0000-0001-8681-4141 Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & Institute of Tropical Biology, Vietnam Academy of Science and Technology, 85 Tran Quoc Toan Street, District 3, Ho Chi Minh City, Vietnam. & Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam. & dvsonitb @ gmail. com; https: // orcid. org / 0000 - 0001 - 8681 - 4141 dvsonitb@gmail.com Author Naiki, Akiyo 0000-0002-3235-2823 Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & naiki @ lab. u-ryukyu. ac. jp; https: // orcid. org / 0000 - 0002 - 3235 - 2823 * Author for correspondence naiki@lab.u-ryukyu.ac.jp text Phytotaxa 2023 2023-01-26 581 1 1921 1935 http://dx.doi.org/10.1094/PDIS-04-22-0755-PDN journal article 10.11646/phytotaxa.581.1.1 1179-3163 7571550 75. Lasianthus yersinii V.S.Dang & Naiki , sp. nov. — Fig. 108 (plate), Fig. 104 (map) Type: — VIETNAM . Khanh Hoa Province , Hon Ba Nature Reserve , 617 m elev., 12°06’39.77’’N , 108°58’59.23’’E , in evergreen forests, 22 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. V1964 ( holotype VNM ! [ VNM00042950 ]; isotypes FU !, VNM ! [ VNM00042951 , VNM00042952 ], the herbarium of Iriomote Station (Japan)) . Diagnosis: —This new species is morphologically similar to Lasianthus latifolius (Blume ex DC.) Blume ex Miq. (1857: 320) based on leaf and inflorescences shapes, but differs from the latter in having more secondary veins (7–8 on each side of midrib vs. ca. 7 on each side of midrib), bracts 1–1.5 mm long (vs. absent), larger calyx ( 1.5–2 mm long vs. ca. 1.5 mm long for tubes and 2.5–4 mm long vs. ca. 2.5 mm long for lobes) and fruits with 5 (vs. 6) pyrenes ( Table 3 ). TABLE 3. Comparison of Lasianthus yersinii with its morphologically similar species.
Characters L. yersinii L. latifolius
Branches glabrous or subglabrous to sparsely strigose on young branches glabrous except appressed-puberulous nodes
Leaf blades elliptic to elliptic-oblong, 15–20 × 4–6 cm; secondary veins 7–8 on each side of midrib elliptic-oblong, 12–16 × 5–7 cm; secondary veins 6–7 on each side of midrib
Stipules 2–3 mm long ca. 3 mm long
Bracts 1–1.5 mm long absent
Calyx tubes 1.5–2 mm long ca. 1.5 mm long
Calyx lobes 2.5–4 mm long ca. 2.5 mm long
Corolla tubes unknown 6–8 mm long
Corolla lobes unknown 6–8 mm long
Fruits 5–6 mm in diam. ca. 5 mm in diam.
Pyrenes 5 6
Description: —Shrubs, 1–3 m tall; branches and branchlets terete, 2–4 mm diam., glabrous or subglabrous to sparsely strigose on young branches, internodes 3–5 cm long. Leaves opposite, elliptic to elliptic-oblong, 15–20 × 4–6 cm , coriaceous, glabrous on both surfaces except sparsely appressed-pubescent midrib and secondary vein abaxially, apex acuminate to cuspidate, aristate 1–1.5 mm long, base acute to cuneate, margin entire; midrib conspicuous adaxially, prominent abaxially; secondary veins 7–8 on each side of midrib, ascending at an angle of 50–60° from midrib, curved to the margin, flat to slightly adaxially, distinct abaxially; tertiary veins parallel; petioles 12–15 mm long, sparsely appressed-pubescent. Stipules triangular, 2–3 mm long, appressed-pubescent. Inflorescences sessile, cymose, 1–7-flowered; bracts small, linear, 1–1.5 mm long, appressed-pubescent. Flowers sessile; calyx campanulate, 4–6 mm long, whitish pale to whitish purple, pubescent, calyx tube 1.5–2 mm long, calyx lobes 5, linear, 2.5–4 mm long; corolla not seen. Fruits drupaceous, globose, 6–7 mm long, 5–6 mm in diam., glabrous, crowned by persistent calyx lobes, orange when ripe; pyrenes 5. Seeds ovoid, 3–4 mm long, sulcate on the abaxial face, brown when dry. Distribution: — Vietnam (currently known only from the Hon Ba Nature Reserve, Khanh Hoa Province ). FIGURE 108. Lasianthus yersinii V.S.Dang & Naiki (from holotype, VNM): A. Branch with fruits, B. Close-up of expanding young leaves, C. Stipules, D. Abaxial leaf surfaces, E. Inflorescence showing lateral view flower buds, F–G. Mature fruits, H. Seeds ( A & F–G : photos by Shuichiro Tagane). Habitat & Ecology: —The species was growing under the shade of the evergreen forest at about 500–700 m elev., where Gnetum gnemon L. (1767: 125), Lasianthus hirsutus (Roxb.) Merr. (1952: 299) , Phyllanthus reticulatus Poir. (1804: 298) , Streblus indicus (Bureau) Corner (1962: 226) and Eustigma honbaense H. Toyama , Tagane & V.S. Dang (2016: 49) are dominant. Phenology: —Flowering and fruiting specimens were collected in July. Etymology: —The specific epithet refers to Dr. Alexandre Emile Jean Yersin, who first discovered the top of Hòn Bà mountain. Vernacular name: —Xú hưƠng yersin. Preliminary conservation assessment: — Lasianthus yersinii was collected from two populations with fewer than 200 individuals in the evergreen forest of Hon Ba Nature Reserve, where is well protected. The Extent of Occurrence (EOO) is less than 200 km 2 and the known Area of Occupancy (AOO) is less than 40 km 2 . However, the natural habitat of this species is close to the road and easily affected by anthropogenic activities. Therefore, we assigned a preliminary status of this species as Vulnerable (VU) based on the IUCN (2019) guidelines. Notes: — Lasianthus yersinii is also similar to L. calycinus Dunn (1912: 367) which is endemic to China , but differs from the latter in having longer petioles ( 12–15 mm vs. 8–10 mm long), bracts 1–1.5 mm long (vs. absent) and smaller calyx.