Conamomum vietnamense N.S.Lý & T.S. Hoang, 2022

Ly, Ngoc-Sam, Hoang, Thanh-Son, Insisiengmay, Oudomphone, Haevermans, Thomas & Newman, Mark F., 2022, Conamomum vietnamense (Zingiberaceae), a new species from Tay Nguyen, Vietnam, Phytotaxa 531 (2), pp. 129-135 : 130-131

Conamomum vietnamense N.S.Lý & T.S. Hoang , sp. nov. ( Fig.1 )

Diagnosis: —Most similar to C. odorum Luu, H.Ð.Tr ần & G.Trần in having yellow flowers, trilobed labellum with reflexed margins and trilobed, yellow anther crest but differing by the presence of 20–50 cm tall stilt roots (vs. absent), elliptic to obovate-elliptic leaves (vs. narrowly elliptic), narrowly ovate bracts (vs. ovate), abaxially pubescent bracteoles (vs. ciliate at teeth), bilobed calyx with truncate tips (vs. tridentate with acute tips), broadly obovate to orbicular labellum (vs. obovate), filament 16–18 mm long (vs. ca. 13 mm long), and style glabrous (vs. sparsely hairy).

Also similar to C. rubidum (Lamxay & N.S.Lý) Škorničk. & A.D.Poulsen , differing by its elliptic to obovate-elliptic leaves (vs. oblonglinear), narrowly ovate bracts (vs. obovate), abaxially pubescent bracteoles (vs. hairy at base), bilobed calyx with truncate tips (vs. tridentate with acute tips), broadly obovate to orbicular labellum (vs. reniform), filament 16–18 mm long (vs. 7–8 mm long), and style glabrous (vs. sparsely hairy).

Type:— VIETNAM. Lam Dong Province: Bao Lam District, Loc Bac Commune, Loc Bac protection forests, 11°46’56.47”N, 107°36’23.75”E, 705 m elev., 12 March 2017, Lý Ngọc Sâm, Lý-879 (holotype: VNM!, isotypes: E!, P!) .

Description: —Laxly caespitose, clump-forming herb, 1.2–2 m tall. Rhizome horizontal, held ca. 20–50 cm above ground by numerous stilt roots ( Fig. 1B ), 10–42.5 cm long, 0.5–1 cm diam., slightly aromatic; stilt roots stout, dark brown to brown-greenish, 20–70 × 0.5–0.7 cm, glabrous; interval between pseudostems 2.8–5 cm, covered by ca. 8 distichous scales; scales hairy, broadly triangular, ca.1 × 1.5 cm, coriaceous, striate, outer surface tomentose, apex broadly acute to acuminate with a short mucronate tip. Leafy shoots 3–10 per each clump; pseudostem 1–1.5 m tall, with 9–16 leaves per pseudostem, swollen at base, 1.6–1.8 cm diameter, gradually becoming smaller towards apex, green, striate, glabrous, outer surface finely reticulate; ligule 4–8 mm long, hairy, swollen at base of petiole, apex obtuse, margin ciliate; petiole canaliculate, 5–8 mm long, green, glabrous; lamina elliptic to obovate-elliptic, striate, 27.2–39.5 × 4–6.8 cm, adaxially dark green, shiny, glabrous, abaxially lighter, glabrous except sparsely puberulous along midvein, base attenuate, apex long caudate. Inflorescences erect, arising from branched rhizome, somewhat congested, 1–4 per pseudostem, (8.5–) 10–17.7 cm long; peduncle stout, cylindrical, (4–)4.5–10.2 × 0.6–1 cm, densely minute pubescent, covered by about 8–14 persistent scales; peduncular scales broadly triangular at base, 0.5–0.7 × 1.4–1.8 cm, triangular-ovate distally, 3.5–5 × 2.5–3.4 cm, brown, striate, papery, tomentose with soft hairs, apex acute to rounded, margin ciliate; spike oblong-obovoid, (4.5–)5.5–10 × 4.5–6, bearing 25–50 bracts, 1–2 flowers open at a time; bracts narrowly ovate, 35–51 mm long, (12–) 14–22 mm at widest point, ascending and curved outward, cream when young, soon turning papery brown, hard, thick, striate, subtending a single flower, abaxially pubescent, apex acuminate, persistent; bracteoles tubular, bidentate, unequal, 25–30 mm long, 10–13 mm at widest point, reddish brown, membranous, abaxially pubescent, tube 13–18 mm long. Flowers (4.9–) 5.5–5.7 cm long; calyx tubular, bilobed, 12–14 × 6–8 mm, tube 6–10 mm long, sparsely pubescent, lobes 3– 6 mm long, apex truncate; floral tube 14–16 × 4–6 mm, white, outer surface sparsely pubescent, inner surface glabrous except for sparse glandular hair at apex; corolla lobes glabrous, reddish, with darker red, narrow stripes; dorsal lobe elliptic, 28–33 × 17–18 mm, apex rounded and hooded; lateral lobes oblong, 27–30 × 10–13 mm, apex short, acute; lateral staminodes triangular-linear, sometimes with a few tiny teeth at base, 8–9 mm long, ca. 1 mm at base, pink-red 2/3 towards apex, bright yellow distally, glandular hairs at base; labellum broadly obovate to orbicular, 35–40 × 34–37 mm, bright yellow with red stripes at margin in basal half of labellum, glabrous, apex markedly trilobed, central lobe deeply bifid, margin undulate and reflexed. Stamen 19–22 mm long; filament flat, distinctly incurved to labellum, 16–18 × 2.8–3 mm, yellow, glandular hairy; anther 8–9 × 4–5 mm, yellow with glandular hairs on connective tissue, dehiscing lengthwise; anther crest trilobed, bright yellow, central lobe 2.5–3 × 3–4 mm, triangular-ovate, apex truncate to shortly acute; lateral lobes 4.5–6 × 1–1.5 mm, lanceolate-linear, horn-like, curved inward. Epigynous glands 1 pair, 2.4–2.6 × 1.8–2 mm, cream yellow, glabrous. Style 39–41 × ca. 0.3 mm, white, glabrous; stigma cup-shaped, ca. 1 × 2 mm; ostiole narrowly transverse, margin ciliate. Ovary shortly cylindrical, 2.5–3 × 3–4 mm, densely pubescent, trilocular; ovules many. Infructescence oblong-ovoid, 5–8 × 3–5 cm, bracts persistent, light brown and papery. Mature fruit subglobose, 13–15 × 10–12 mm, red, smooth, pubescent, calyx persistent, containing 10–15 seeds; seeds irregular subglobose, 3–3.5 × 2– 2.5 mm, aril white, ciliate.

Phenology: —Flowering from March to May, fruiting from May to July.

Etymology: —The specific epithet “ vietnamense ” refers to its current discovery and distribution in Vietnam.

Distribution, habitat and conservation status: — Conamomum vietnamense is found in only three localities in Dak Nong and Lam Dong provinces, Tay Nguyen, Vietnam ( Fig. 2A ). It grows on wet ground or on hill slopes throughout the understorey of the evergreen, mixed broadleaved tropical forests which is situated within the confines of the Nam Cat Tien protection forests in Dak R’Lap District, Dak Nong Province and Loc Bac protection forests in Bao Lam District, Lam Dong Province. The new species grows in relatively rich, wet but well-drained soils, at altitudes of 600– 700 m. We observed ten subpopulations of a total of about 700 mature clumps in the Loc Bac protection forests and five subpopulations of a total of about 200 mature clumps found in the Nam Cat Tien protection forests. The extent of occurrence (EOO) and the area of occupancy (AOO) were calculated to be 28.4 km 2 and 16 km 2, respectively ( Fig. 2B ). These two values meet the criteria B1 (EOO <100 km 2) for Critically Endangered and B2 (AOO <500 km 2) for Endangered, following the IUCN Red List Categories and Criteria Version 3.1 ( IUCN 2019). Although the known habitat of the new species is part of a protected area, its forest habitat is frequently logged and disturbed, in particular to create clearings for rubber and coffee plantations. Based on the IUCN Red List criteria ( IUCN, 2019), we therefore provisionally assess this species as Endangered (EN B2ab(iii)).

Other specimens examined (paratypes): — VIETNAM. Dak Nong Province: Kien Duc District, Dak R’lap Commune , Nam Cat Tien protection forest, 11°50’01.50”N, 107°34’23.60”E, 602 m elev., 22 March 2017, Hoang Thanh Son, VAFS-1356 (VAFS!) . Lam Dong: Bao Lam District, Loc Bac Commune, Loc Bac protection forests, 11°47’24.71”N, 107°33’55.81”E, 638 m elev., 18 November 2016, Lý Ngọc Sâm, Lý-838 (VNM); ibid., 11°46’56.32”N, 107°36’21.65”E, 707 m elev., 28 May 2017, Oudomphone Insisiengmay and Lý Ngọc Sâm, OI 172 (VNM!, P!); ibid., 11°47’39.63”N, 107°36’51.31”E, 710 m elev., 19 March 2017, Hoang Thanh Son, VAFS- 1235 (VAFS!) and 11°46’06.9”N, 107°32’23.6”E, 620 m elev., 20 March 2017, Hoang Thanh Son, VAFS-1301 (VAFS!) .

Notes: —A detailed morphological comparison between C. vietnamese and the two species most similar to it is provided in Table 1 . Conamomum vietnamense also resembles C. pierreanum by its stilt roots, persistent bracts and the pattern of colours in the flower but the longer petioles, broadly ovate to boat-shaped bracts with cucullate apex, bowl-shaped labellum, and globose and finely ridged fruits of C. pierreanum distinguish it from the other three species in Cambodia and Vietnam.

With the description of C. vietnamense , the distribution of the genus in Vietnam is extended northwards to Dak Nong Province, and one more locality in Lam Dong Province. The localities of the three Vietnamese species lie some distance south of Lao PDR. Further field work is needed to establish whether Conamomum occurs in Lao PDR or not. Conamomum pierreanum is relatively widespread in Thailand and Cambodia, while the three Vietnamese species are narrow endemics, each known from one or two localities, and all under threat of habitat disturbance.

Figures

FIGURE 1. Conamomum vietnamense. A. Plant in natural habit; B. Basal part of mature plant showing rhizomes with stilt roots; C. Leaves; D. Petioles and ligules (upper) with detail of ligule (lower); E. Inflorescence; F. Top view of inflorescence; G. Close-up of flower; H. Side view of flower; I. Bracts; J. Flower; K. Bracteole; L. Calyx; M. Dorsal and lateral corolla lobes (from left); N. Floral tube and stamen; O. Ovary and epigynous glands; P. Labellum; Q. Stamens (from left: front, side and back views); R. Mature fruit, entire and in cross-section. Scale bars: I–N and P–R = 10 mm; O = 5 mm. Photos and plate from Lý-879.

FIGURE 2. A. Distribution map of C. vietnamense in Vietnam; B. Extent of occurrence (EOO) and Areas of occurrence (AOO) of subpopulations.