Psychotria ngotphamii Bao, Tagane, Yahara & V.S.Dang, 2023

Nguyen, Quoc Bao, Quach, Van Toan Em, Huynh, Huu Duc, Pham, Quoc Trong, Truong, Ba Vuong, Yahara, Tetsukazu, Tagane, Shuichiro & Dang, Van-Son, 2023, A new species of Psychotria (Rubiaceae) from Bidoup - Nui Ba National Park, Vietnam, Phytotaxa 618 (2), pp. 188-194 : 189-191

Psychotria ngotphamii Bao, Tagane, Yahara & V.S.Dang , sp. nov. ( Figures 1 , 2 )

TYPE:— VIETNAM. Lam Dong Province, Bi Doup-Nui Ba National Park , in evergreen forests, 12°10′26.91″N, 108°41′53.94″E, 1490 m elevation, 19 Nov 2014, Tagane S., Toyoma H., Dang V.S., Nagamasu H., Naiki A., Tran H., Yang C.J., Cuong, N.Q., Hieu H.N.P., Loi X.N. V1850 (holotype VNM [VNM00042784!]; isotypes FU!, VNM [VNM00042782!, VNM00042783!]) .

Diagnosis: — Psychotria ngotphamii is similar to P. bonii Pitard (1924: 347) of Vietnam and Thailand in having an entirely glabrous plant body except some floral parts, similar leaf shape, cymose inflorescences, and similar fruits shape. However, it differs in having smaller stipules (1.5–2 mm long in P. ngotphamii vs. 3–8 mm long in P. bonii ), smaller leaf blades (2.5–6.5 × 1–2.5 cm vs. 5.5–18.3 × 2.5–6.3 cm), shorter petioles (5–7 mm long vs. 15–35 mm long), longer calyx lobes (0.5–0.8 mm long vs. 0.3–0.5 mm long), longer corolla lobes (1.2–1.4 mm long vs. 0.7–1 mm long), and larger fruits (8–10 mm long vs. 7–8 mm).

Shrubs 0.5–1 m tall. Current year twigs dark green in vivo, glabrous, old twig brownish-grey in vivo, dark brown in sicco, stems cylindrical, internodes 0.2−0.9 cm long. Stipules ovate-triangular, 1.5−2 mm long, green in vivo, dark brown in sicco, glabrous on both sides, connate at base, apex rounded, margin entire, outer surface with two setae at the base over topping the apex of stipule, setae filiform, ca. 1 mm long, margin ciliolate. Leaves simple, oppositedecussate, petiolate; lamina elliptic-oblong or obovate-oblanceolate, 2.5−6.5 × 1−2.5 cm, adaxially dark green in vivo, abaxially light green in vivo, glabrous on both sides, base acute, apex acute to acuminate, margin entire, venation mixed brochidodromous, midrib prominent on both sides, secondary veins 5−8 pairs, prominent abaxially, without domatia; petioles 5−7 mm long, glabrous. Inflorescences terminal or axillary on new branches, trichotomous, peduncles 1−2.3 cm long, secondary axes 0.4−1.1 cm long, greenish-white in vivo, glossy, glabrous; bracts triangular, 0.6−1 mm long, greenish in vivo, apex acute, margin ciliolate, persistent. Flowers white, short-pedicellate; pedicel 0.4−0.9 mm long, glabrous, bracteoles triangular, 0.2−0.5 mm long, glabrous adaxially, pilose abaxially, margin ciliate, persistent; calyx obconic, glabrous, tube 0.8−1 mm long, lobes 5, triangular, 0.5−0.8 mm long, margin ciliate; corolla cupuliform, tube 1.7−2 mm long, lobes 5, triangular, 1.2−1.4 mm long, thick, recurved at the apex, puberulous abaxially, densely puberulous adaxially, with dense villous hairs at throat internally; stamens 5, inserted in the corolla throat, filaments 0.3−0.4 mm long, glabrous, erect, anthers oblong, 0.6−0.8 mm long, dorsifixed; ovary 2-locular, ovule 1 in each locule, style 1–2 mm long, glabrous, stigma broadly obovate to rounded shape, 2-lobed. Fruits drupaceous, ellipsoid, 8−10 mm long, 4−5 mm in diam., green when young, red when ripe, shiny, glabrous, apex with persistent calyx lobes; pyrenes 2, ventrally flat with 1 groove, convex dorsal with four flat areas and three ridges. Seeds ellipsoid to hemiellipsoid, 6−8 mm long, 3−4 mm in diam., irregularly sulcate on the abaxial face, blackish brown in sicco, albumin abundant.

Distribution and habitat: — Vietnam (so far known only from Bidoup - Nui Ba National Park, Lam Dong Province). Psychotria ngotphamii grows in evergreen broad-leaved forest dominated by species of Fagaceae , Euphorbiaceae , Rubiaceae , Lauraceae , Annonaceae , and Symplocaceae , at elevations ranging from 1490 to 2060 m.

Phenology: —Flowering and fruiting from August to December.

Etymology: —The species epithet is named after Dr. Phạm Văn Ngọt (former Dean of the Faculty of Biology, HCMC University of Education) for his great contribution to the study of plant diversity in Vietnam.

Vernacular name: —Lấu Phạm Văn Ngọt.

Preliminary conservation assessment: — Psychotria ngotphamii is found scattered in the understory of lower montane and montane forests within Bidoup - Nui Ba National Park, Lam Dong Province, Vietnam. From our field observations, the estimated number of mature individuals is approximately 500. The species has an extent of occurrence (EOO) of less than 100 km 2 and an area of occupancy (AOO) of less than 25 km 2. The habitat of P. ngotphamii is within the protected area of the national park, which is well preserved and stable. Given this situation, its status is Vulnerable (VU) according to the IUCN Red List criteria D1 ( IUCN 2022).

Notes:— Psychotria ngotphamii is also similar to P. henryi Léveillé (1914: 179) , which is known from China, but differs in having glabrous branches and petioles (vs. puberulent), longer peduncle (1–2.3 cm long vs. ca. 0.5 cm long), smaller bracts (0.6−1 mm long vs. 1−1.5 mm long), and calyx lobes (0.5−0.8 mm long vs. 0.8−1.2 mm long) ( Table 1 ).

Additional specimens examined:— VIETNAM. Lam Dong Province, Bidoup - Nui Ba National Park, Mt. Langbian , in montane evergreen forests, 12°02′52.49″N, 108°26′22.73″E, 2062 m elevation, 21 December 2018, Yahara et al. V9590 (DLU, FU, KAG [KAG127341]) .

Figures

FIGURE 1. Psychotria ngotphamii (from the holotype, VNM), A. Fruiting branch, B. Abaxial leaf surface, C. Stipules, D. Part of inflorescence and flower, E–F. Corolla, tube opened to show stamens and dense villous pubescence on the corolla throat (when dry), G. Calyx with bracteoles and epicalyx (when dry), H. Stigma and style (bud when dry), I. Infructescence. K. Part of infructescence showing the persistent bracts. L. Fruit in transverse section showing pyrenes, M. Seeds (A, B, D, I: photos by Shuichiro Tagane, and C, E–H, K–M: photos by Ba Vuong Truong based on the holotype (Tagane et al. V1850, VNM)).

FIGURE 2. Psychotria ngotphamii. A.Fruiting branch,B. Stipules, C. Flowers,D. Corolla, opened to show stamens.E. Calyx, hypanthium and bracts, F. Infructescence, G. Fruit in transverse section showing pyrenes, H. Seeds. Materials from the holotype (Tagane et al. V1850, VNM). Drawn by Quoc Bao Nguyen.