Memecylon longipedunculatum Tagane, V.S.Dang & Nuraliev, 2025

Tagane, Shuichiro, Dang, Van-Son, Truong, Ba Vuong, Nguyen, Quoc Bao, Pham, Quoc Trong, Nguyen, Tran Vy, Yamamoto, Takenori, Kongxaisavath, Deuanta, Yamazaki, Kaito, Nuraliev, Maxim S., Fomichev, Constantin I. & Souladeth, Phetlasy, 2025, Memecylon longipedunculatum (Melastomataceae), a new species from coastal areas of south central Vietnam, Phytotaxa 683 (1), pp. 1-8 : 2-7

Memecylon longipedunculatum Tagane, V.S.Dang & Nuraliev , sp. nov. ( Figs. 1–3 )

Diagnosis: — Memecylon longipedunculatum is similar to M. chevalieri Guillaumin (1921a: 7 , see also Guillaumin 1921b: 936) distributed in Cambodia, Laos and Vietnam by having axillary and terminal inflorescences with relatively long peduncles 1–2.7 cm long (vs. almost 1.5 cm long in M. chevalieri ), but distinguished from the latter species by its smaller leaf blades (1.2–5.7 × 0.7–2.4 cm vs. 4–7 × 2–4 cm), longer pedicels (3.3–5.5 mm vs. 2–3 mm long), longer petals (ca. 4 mm vs. 2–3 mm long) with acute (vs. acuminate) apex, and subglobose (vs. ovoid-globose) fruits.

TYPE: — VIETNAM. Ninh Thuan Province: Ninh Hai District, Nui Chua National Park , open coastal shrubs, 11.74982°N, 109.21890°E, elev. 25 m, 20 December 2023, S. Tagane, V. S. Dang, P. Souladeth, B. V. Truong, T. V. Nguyen, Q. T. Pham, Q. B. Nguyen, D. Kongxaisavath, T. Yamamoto, K. Yamazaki N216 [fl. & fr.] (holotype VNM: VNM00071517 !; isotypes FOF!, KAG: KAG186215 !, VNM: VNM00071547 !) .

Trees up to 5 m tall, evergreen, entirely glabrous; bark reddish brown, finely longitudinally fissured; young branchlets dull yellow-brown, terete and slightly flattened, soon becoming terete with age; old branchlets grayish brown to reddish brown, slightly inflated at nodes; internodes 1.2–3.7(–5.4) cm long. Leaves opposite; blades fleshy (slightly succulent), elliptic to elliptic-obovate or ovate, (1.2–)2.7–5.7 × (0.7–) 1.1–2.4 cm, bright red when young especially adaxially, adaxial surface of mature leaves dark green in vivo, dark yellow-green to dull brownish yellow in sicco, abaxial surface light green in vivo, dull yellow-brown to very pale creamy brown or greenish yellow in sicco, apex obtuse or sometimes emarginate, base cuneate, margin entire and slightly revolute in sicco; midvein flat or slightly impressed adaxially and somewhat raised abaxially; secondary veins 4–6 pairs, indistinct or obscure on both surfaces; petioles (1.4–) 2–3.7 mm long, pale green in vivo, dull yellow green to greenish yellow in sicco. Inflorescences terminal or in axils of distal leaves, possibly panicles or thyrsoids, 2.5–4.8 cm long, 3–13-flowered; peduncle 1–2.7 cm long, elongating to up to 5.1 cm long in fruits, distally quadrangular in cross section; rachis 0.5–1 cm long; bracts ovate-triangular, ca. 1 mm long, caducous before maturation of flower bud. Pedicels 3.3–5.5 mm long and ca. 0.2 mm in diam., elongating to 1 cm long and slightly thickening in fruits. Flowers ca. 0.9 cm across. Hypantho-calyx broadly campanulate, 2.5–3 mm long (together with ovary), ca. 3 mm in diam., light purple or yellowish green in vivo, dull brownish yellow in sicco; calyx ca. 0.2–0.3 mm long, with 4 very short and broad lobes, with each lobe broadly emarginate at apex so that calyx margin appearing shallowly 8-dentate. Petals 4, broadly ovate-triangular, claw-like proximally, with a very narrow base leaving a distinct scar, ca. 4 × 4 mm, adaxially purplish blue and abaxially bluish purple in vivo, apex acute. Stamens 8, equal; filaments 2.5–2.8 mm long, distally tapering to a very narrow connection with anther, blue in vivo, very pale blue in sicco; anthers ca. 1.2 mm long; connective crescent-shaped, with concave lower side, blue; anther gland placed at the middle of adaxial side of connective, distinct, elliptic, ca. 0.7 mm long, dull brownish yellow or dark purple, shiny; thecae facing upwards, pale yellow, longitudinally dehiscing. Ovary inferior, with radially grooved upper surface (at bottom of hypanthium); style 3–5 mm long, linear, gradually becoming thinner towards apex, blue in vivo, very pale blue in sicco. Fruit a berry, subglobose, 7.5–9 × 7–8 mm, blackish purple when mature, with smooth surface, with a crown formed by persistent hypantho-calyx ca. 1.8 mm high and 3.9–4.2 mm in diam. Seeds 1 per fruit, subglobose, ca. 7 mm in diam., reddish brown.

Additional specimens examined (paratypes):— VIETNAM. Khanh Hoa Province: Île Tre près Nhatrang [Nha Trang city area, Hon Tre Island], dans la partie sud de l’île [in the southern part of the island], sol rocheux [in rocky soil], 31 March 1922, E. Poilane 2889 [fl. buds] ( P: P04802385 , image!) ; Nha Trang city area, Hon Tre Island, near Dam Bai marine climate station, dry low seaside forest, 12°11′52′′N, 109°17′08′′E, elev. 140 m, 26 May 2021, M. S. Nuraliev NUR 3340 [fl.] ( MW: MW0595851 , MW0595852 , MW0595853 ) ; Île hon mun près Nhatrang [Nha Trang city area, Hon Mun Island], 24 April 1922, E. Poilane 3139 [fl. and young fr.] ( L: L.3904555, P: P04802297 , P04802299 , images!) . Ninh Thuan Province: Ninh Hai District, Nui Chua National Park , open scrubs on dry rocky slopes on sandstone, 11.67766°N, 109.17364°E, elev. 20 m, 24 December 2023, S. Tagane, V. S. Dang, P. Souladeth, B. V. Truong, T. V. Nguyen, Q. T. Pham, Q. B. Nguyen, D. Kongxaisavath, T. Yamamoto, K. Yamazaki N465 [fl.] ( FOF, KAG: KAG186465 , VNM: VNM00071350 , VNM00071410 ) ; Ninh Hai District, Vinh Hai municipality, Nui Chua National Park , Da Vach cape, 3 km ENE of Vinh Hy town, dry low seaside forest, 11°44′02′′N, 109°13′29′′E, elev. 270 m, 8 March 2023, M. S. Nuraliev & C. I. Fomichev NUR 4192 [fl.] ( MW: MW0595854 ) ; Ca Na , forêt de remplacement [secondary forest], sol rocheux [rocky soil], elev. 300 m, 26 December 1923, E. Poilane s.n. [fr.] ( P: P04802376 , image!) .

Distribution: —Endemic to the south-central coast region of Vietnam (provinces Khanh Hoa and Ninh Thuan) ( Fig. 4 ).

Habitat: —Dry evergreen forests at seaside, open coastal scrubs, at elevations of 20– 300 m.

Etymology: —The species epithet refers to its long peduncles (up to 2.7 cm long in flower and to 5.1 cm long in fruit), one of the remarkable features distinguishing it from most of its congeners in the Indochinese Peninsula.

Phenology: —Flowering and fruiting specimens were collected in December and from March to May.

Vernacular name:— Sầm cuống dài (Vietnamese).

Preliminary conservation status:— Vulnerable (VU). Seven collections of Memecylon longipedunculatum are known so far. These collections originate from five localities in Ninh Thuan and Khanh Hoa provinces, South Central Coast Vietnam. The area of occupancy (AOO) and extent of occurrence (EOO) are estimated as 28 km 2 and 803 km 2, respectively, using GeoCAT ( Bachman et al. 2011). A large area of its habitat, including the Nui Chua National Park, Hon Mun Island and Hon Tre Island, has been protected at either the national or district level, and therefore the status of the known populations is expected to be stable. However, at least some areas outside the protected areas have been disturbed due to land use including cattle grazing, human settlement, and tourism development. Given this situation, M. longipedunculatum is assessed here as Vulnerable (VU) according to the IUCN criterion D2 ( IUCN 2012, 2024).

Notes: — Memecylon longipedunculatum is readily distinguishable from its Indochinese congeners by its long inflorescences borne terminally or in axils of distal leaves ( Figs. 2A & D , 3A & B ), peduncle 1–2.7 cm long, 4- lobed calyx with the broadly emarginate apex of each lobe so that the calyx appears to be shallowly 8-dentate ( Fig. 2F ), and crescent-shaped anther connective with centrally placed gland ( Fig. 2E & F , 3G & H ). The new species is closest morphologically to M. chevalieri , as outlined in the diagnosis. In addition, M. longipedunculatum is similar to M. lanceolatum Blanco (1837: 301) of Vietnam, Taiwan, the Philippines, Malaysia, and Indonesia (Kalimantan and Sulawesi) and M. cantleyi Ridley (1918: 72) of Thailand, Malaysia, and Indonesia (Sumatra and Kalimantan) in having peduncles longer than 0.5 cm. However, it is distinguished from M. lanceolatum by obtuse or sometimes emarginate (vs. acuminate, sometimes with obtuse tip) leaf apex, and crescent-shaped (vs. J-shaped) anthers ( Huang & Huang 1993, Chen & Renner 2007, Hughes 2013). The new species differs from M. cantleyi in having smaller leaf blades (1.2–5.7 × 0.7–2.4 cm vs. 7–19.5 × 3–7.5 cm), obtuse or sometimes emarginate leaf apex (vs. apex distinctly acuminate with acumen 1–2 cm long), distinct (vs. indistinct) anther gland, and caducous (vs. semi-persistent) style ( Maxwell 1980, 1989, Hughes 2013).

Figures

FIGURE 1. Holotype of Memecylon longipedunculatum (Tagane et al. N216, VNM00071517).

FIGURE 2. Memecylon longipedunculatum. A. Flowering branch. B. Abaxial leaf surface. C. Bark. D. Inflorescence. E. Top view of flower bud (up-left), anthetic flower (bottom), and post-anthetic flower (up-right). F. Inflorescence branch with anthetic and post-anthetic flowers. G. Fruiting stage of inflorescence. Tagane et al. N465 (A, D–F) and Tagane et al. N216 (B, C, G). Photos by S. Tagane.

FIGURE 3. Memecylon longipedunculatum. A, B. Flowering branches. C, D. Leaf, adaxial and abaxial side. E. Inflorescence. F. Flower, top view. G. Stamen, side view. H. Anther, side view. I. Post-anthetic flower (after abscission of petals and stamens). J. Mature flower bud. Nuraliev & Fomichev NUR 4192 (A, E–J) and Nuraliev NUR 3340 (B–D). Photos by M.S. Nuraliev.

FIGURE 4. Distribution map of Memecylon longipedunculatum. The map is not aimed to show Vietnam in its entire borders.