Syzygium triflorum T. T. Hoang, Kim Thanh, S. Tagane & D. H. Cuong, 2025

Syzygium triflorum T. T. Hoang, Kim Thanh, S. Tagane & D. H. Cuong sp. nov.

Type.

Vietnam. Gia Lai Province, K’Bang District, Son Lang Commune, Kon Chu Rang Nature Reserve, in coniferous forest, 200 m from Bai Chay station along the path , 14°28'44.5"N, 108°34'19.2"E, 1015 m a. s. l., 4 July 2024, T. T. Hoang, N. T. K. Thanh & D. H. Cuong DLU 1005 (holotype DLU! isotypes HNU [ HNU 025528 !, HNU 025529 !], the Herbarium of The Joint Vietnam-Russia Tropical Science And Technology Research Center) (Figs 1 View Figure 1 , 2 View Figure 2 ) GoogleMaps .

Diagnosis.

Syzygium triflorum could be confused with S. skiophilum (Duthie) Airy Shaw distributed in Thailand, Malay Peninsula and Borneo ( Airy Shaw 1949; Parnell and Chantaranothai 2002; Ashton 2011). Generally, S. triflorum is similar to S. skiophilum because they both show small tree habit and short cymose inflorescences with tiny flowers. However, S. triflorum differs from S. skiophilum in having 4 - angled and reddish-grey twigs (vs. terete and blackish-brown in S. skiophilum ), oblong leaf blades (vs. elliptic-lanceolate, obovate or oblanceolate), fewer secondary veins (26–30 pairs vs. ca. 45 or 14–18 pairs), exclusively axillary inflorescences (vs. temirnal and axillary), lanceolate-ovate bracts (vs. linear), sessile or subsessile flower (vs. with short pseudostalk ca. 1 mm long), obconical hypanthium (slightly pyriform in flower buds) (vs. funnel-shaped) and more stamens (18–28 vs. 8 stamens) (Table 1 View Table 1 , Fig. 3 View Figure 3 ).

Description.

Trees, 1.5–3 m tall, all part glabrous. Young twigs 4 - angled, reddish-grey. Leaves opposite; petioles 1–2 mm long, concave adaxially; blades oblong, 7.5–8.5 cm × 2.0– 2.2 cm, dark green and shiny adaxially, pale green, with numerous dark green gland dots abaxially, coriaceous, base cuneate, margin entire, apex attenuate with a rounded acute tip 1.5–2 mm long, mid-rib impressed adaxially, prominent abaxially, secondary veins faint, 26–30 pairs, tertiary veins faintly visible, intramarginal vein 1, 0.6–0.8 mm from the margin. Inflorescences short cymose, axillary or on old branchlets behind leaves, 3–4 mm long, clusters of 3 (rarely reducing to 1) flowers; peduncle 0.8–1 mm long, terete; bracts lanceolate-ovate, 0.5–0.7 mm long, pale green to dark red on the upper half, apex rounded. Flower buds pyriform. Flowers 2.8–3.2 mm × 1.8–2.0 mm, light green, sessile or with pseudostalks to 0.5 mm long; bracteoles triangular, 0.2–0.3 mm long, dark red on the upper half, caducous. Hypanthium obconical, 2.0– 2.2 mm × 1.8–2.0 mm, light green. Sepals 4, very broadly triangular, 0.2–0.3 mm long, light green, persistent, apex acute. Petals 4, free, suborbicular, 0.8 mm × 1.0 mm, light green, membranous, concave adaxially. Stamens 18–28 in a single whorl, 0.8–1 mm long, filaments white, anthers ellipsoid, ca. 0.1 mm long, cream-coloured. Ovary 2 - locular, many ovules per locule, placentas axile; style and stigma 0.8–1.0 mm long, positioned lower than the stamens. Fruits (immature) globose, 4 × 4 mm, calyx disc convex. Seeds not seen.

Flowering and fruiting.

The flowers and fruits were observed during the rainy season in July 2024. At this time, the fruits were not fully matured.

Ecology.

This species grows in a mixed broad-leaved and coniferous forest so far known only from Kon Chu Rang Nature Reserve. The forests are dominated by Dacrydium elatum (Roxb.) Wall. ex Hook. and Dacrycarpus imbricatus (Blume) de Laub. ( Podocarpaceae ), along with other angiosperms, such as Exbucklandia populnea , Rhodoleia championii ( Hamamelidaceae ), Magnolia mediocris ( Magnoliaceae ), Castanopsis spp. ( Fagaceae ) and Schima superba ( Theaceae ). Many small trees grow in the understorey with Syzygium triflorum sp. nov., including Ixora sp. , Lasianthus spp. ( Rubiaceae ), Eurya sp. ( Pentaphylacaceae ) and Eriobotrya bengalensis ( Rosaceae ). The habitat receives approximately 60–70 % of the total light from the understorey at an elevation around 1,000 m a. s. l.

Vernacular.

Trâm ba hoa (three-flowered syzygium), Trâm hoa nh ỏ (tiny-flowered syzygium)

Etymology.

The species epithet refers to its number of flowers in a inflorescence, which is usually in a cluster of three.

Preliminary conservation status

This species is currently known with only a few populations being found, each consisting of about 30–40 individuals, within a 10 - hectare (0.01 km 2) stand of the mixed broad-leaved and coniferous forest dominated by Dacrydium elatum and Dacrycarpus imbricatus at Kon Chu Rang Nature Reserve. The total number of the mature individuals are approximately 200, living in understorey and strictly protected near the Bai Chay ranger station.

The primary natural threat in this area might be random fires, which could cause extreme fluctuations in the number of mature individuals. However, this risk is less prevalent in broad-leaved forests and the mixed broad-leaved and coniferous forests of Kon Chu Rang. Fires have not been recorded in these forests in the Nature Reserve for at least 30 years. Therefore, this species is temporarily regarded as safe in this forest stand.

All five IUCN criteria have been considered, but there is no fully direct or indirect information about the species’ current status or possible threats. Considering the known population is very small, restricted to a 10 - hectare stand and the number of mature individuals approximately 200 trees, Endangered (EN) is categorised for the preliminary conservation status of this species according the criteria D ( IUCN 2012).