Vietnamocasia dauae N. S. Lý, T. Haevermans, Y. S. Wong & D. V. Nguyen, 2017

Ngoc-Sâm, Lý, Yeng, Wong Sin, Haevermans, Thomas, Dư, Nguy ễn Văn & Boyce, Peter C., 2017, Vietnamocasia, a new genus from Central Vietnam belonging to the AlocasiaColocasia clade (Araceae), Phytotaxa 303 (3), pp. 253-263 : 259-262

Vietnamocasia dauae N. S. Lý, T. Haevermans, Y. S. Wong & D. V. Nguyen , sp. nov. ( Figs. 3 , 4 )

Type:— VIETNAM. Quảng Ngãi Province, Nghĩa Hành District, Hành Tín Đông Commune, TrƯờng L ệ Village, Mount Dầu, Nhự hill,

14°51.45’N, 108°48.59’E, 317 m, 20 May 2015, Ngọc-Sâm Lý, Lý-654 (holotype: VNM! (including spirit), isotypes: P!, VNM!).

Small to moderate evergreen mesophytic herbs to 50–80 cm tall, stem 35–50 cm long, internodes distinct separated by conspicuous annulated scars, 2–3.5 cm diam., sometimes wider than long, green somewhat slender, erect, later decumbent and rooting along underside, active shoot tip ascending in age to 15–30 cm tall, older parts without remains of old leaf bases, un-branched; prophyll with two keels, cataphyll 4.5–8.8 cm long and ca. 1.2 cm wide at base, soon deciduous. Leaves (6–)9–19 together, erect, spreading with age, individually long-lived; petioles slender, D-shaped in cross-section, (8–) 13–41 cm long, green; leaf sheaths fully attached, (7–) 8.5–23 cm long, ca. ¼–½ length of petiole, exterior green, interior paler, wings of sheath persistent, slightly open; leaf blade elliptic to oblong-elliptic, peltate, thickly coriaceous, glabrous, 22–39 × 7–14 cm, adaxially glossy dark green, abaxially medium green, without waxy glands in the axils on the lower leaf surface, margin entire, apex broadly acute with an apiculate 3–5 mm long; anterior lobe widest usually 1 / 3 of the way distal to petiole insertion, occasionally ¼ way distal to petiole insertion; anterior costa with 5–6 sub-opposite primary lateral veins on each side, diverging at ca. 45°–60°, running curved upwards or straight into a conspicuous sub-marginal vein <0.5 mm from margin; secondary venation not forming inter-primary collective veins; posterior lobes mostly connate save for a shallow acute notch, (1 / 4 –) 1 / 5 – 1 / 7 the length of the anterior lobe, 4.8–5.5 cm long, together attenuate with tips diverging. Inflorescence nodding, solitary or 2–3 together, subtended by a cataphyll; peduncle rarely exceeding the cataphyll at anthesis, slightly slender, about ½ to ¾ the length of the petiole, 11–34 cm long, medium green, erect; narrowly ovate to oblong ovate, 8–24 cm long, 2–3.5 cm at widest point, medium green, margins winged, opened, apex mucronate, apiculate with mucro 7–15 mm long; spathe 12–12.5 cm long, slightly constricted between lower spathe and spathe limb; lower spathe cylindrical or slightly ovoid, 3–4 cm long, 1.3–1.5 cm wide, medium green outside, paler inside, margins convolute; spathe limb oblong-lanceolate, 8–13 cm long, 3.3–3.8 cm at widest point, externally pale green, internally white, smooth and shiny in both surfaces, apex shortly acuminate 3–5 mm long, spathe limb deflexed at base when anthesis, turning opaque straw-coloured, soon caducous at fruiting stage; spadix distinctly shorter than spathe, 7–8.7 cm long, very shortly stipitate, <1 cm long, white; pistillate zone cylindrical, 15–21 × 4–5 mm, pistils c. 160 pistils, slightly loosely arranged; ovaries sub-globose, 1.2–1.5 mm long, 1.4–1.5 mm diam., ivory-white, apex gradually tapering to the style, 1–locular, 5(–6) ovules, anatropous, funicle distinct, very short ca ¼ length of the ovary, placenta basal; style very short 0.2–0.4 × 0.3–0.6 mm, ivory-white; stigma discoid-subcapitate, inconspicuously three to four-lobed, slightly concave, pale cream, 0.2–0.3 mm thickness, 0.6–0.7 mm in diam.; sterile interstice subcylindric, 12–16 mm long, 4–4.5 mm at widest point near the pistillate zone, gradually narrowed distally corresponding to spathe constriction; synandrodes in 5–6 whorls; lower synandrodia often irregularly angular at both ends, the remainder elongate rhomboid-hexagonal, 2–3 mm long, 1.2–2 mm thick, creamy yellow to white, flat-topped; staminate zone cylindrical, above the constriction, slightly tapering proximally, 10–12 × 5–7 mm diam.; staminate flowers each comprised of 2–3 stamens, stamens free, oblong-linear, creamy white, 1–1.1 mm long, 0.3–0.5 mm wide; thecae oblong-linear, dehiscing by apically pores ca 0.2 mm long, connective conspicuous, flat, creamy white; appendix sub-cylindrical, weakly fusiform, blunt-tipped, equaling to considerably exceeding half the length of the spadix, 3–4.6 × 0.5–0.7 cm, dull ivory-cream, with more or less conspicuous brain-like patterning of longitudinal grooves. Infructescence declinate; fruiting spathe narrowly triangular-ovoid, 6–7.2 cm long, 2.3–2.7 cm at widest point, externally dark green, internally whitish; fruits ca 40, globose, inconspicuously quadrangular at the top, 4.1–6 × 5–5.5(–8.5) mm, 1(–2)-seeded, probably ripening red, but to be confirmed; seed testa costate, embryo shortly cylindrical, endosperm copious.

Etymology:—The specific epithet is for Mount Dầu, the type locality, treated as feminine.

Phenology:— Vietnamocasia dauae flowers in May, during when the young inflorescences are a food source for wild monkeys ( Macaca spp. ). Although fruiting spathe dehiscence and ripe fruit are yet to be seen, unripe fruit was found in mid September.

Distribution and preliminary IUCN conservation assessment:—Ten small populations each of 2–8 scattered mature individuals were observed on Mount Dầu with a total area of 6.5 km 2 (650 ha) while less than 100 individuals are known from Cà Đa Mountain with a total area of about 38 km 2 (3.800 ha) ( Figure 3 ). The Extent of Occurrence (EOO) is estimated to be less than 20,000 km 2. Although this species is under the protection of the local authorities of TrƯờng Lệ and Khánh Giang communes, and by the Department of Forest Protection of Tây Trà District, Quảng Ngãi province, these populations are nevertheless vulnerable and appear to be declining owing to human activities such as harvesting of non-timber forest products, and land use changes for Acacia plantations. According to the IUCN Red list categories and criteria ( IUCN, 2012), this qualifies the species here to be listed as Endangered (EN B2ab (iii,iv,v)). Further exploration of the area around Dầu Mountain is necessary to fully assess the conservation status.

Additional examined material:— VIETNAM. Qu ảng Ngãi Province , Tây Trà District , Trà Trung Commune , Vàng Village , Cà Đam mountains, NƯ ớc Bi ếc stream, 15°08.96’N, 108°27.81’E, 783 m, 28 July 2016. Ngọc-Sâm Lý & TrƯƠng Bá VƯƠng, Lý -759 ( VNM) ; Nghĩa Hành District , Hành Tín Đông Commune, TrƯờng L ệ Village, 14°51’38’’N, 108°48’36’’E, 28 May 2016, Du-Sy 04 ( HN) ; Nghĩa Hành District , Hành Tín Đông Commune , TrƯờng L ệ Village, Mount D ầu, Nh ự hill, 14°52.06’N, 108°48.74’E, 378 m, 20 May 2015, Ng ọc-Sâm Lý, Lý -655 ( VNM, P) ; ibid., Chí stream, 14°52.70’N, 108°49.12’E, 153 m, 19 May 2015, Ng ọc-Sâm Lý , Lý -648 ( VNM) ; ibid., 14°51.36’N, 108°49.19’E, 486 m, 9 August 2015, Ng ọc-Sâm Lý , Lý -660 ( VNM) ; ibid., Đá Bông hill, 14°51.42’N, 108°48.35’E, 271 m, 18 May 2015, Ng ọc-Sâm Lý , Lý -642 ( VNM) ; ibid., Nh ự hill, 14°52.06’N, 108°48.74’E, 350 m, 14 December 2010, Ng ọc-Sâm Lý & Thomas Haevermans, Lý -528 ( VNM) .

Notes:—Neither Alocasia nor Colocasia have been revised for Vietnam since Gagnepain (1942).

Figures

FIGURE 3. Vietnamocasia dauae. A. Habit; B. Leaf blades: adaxially and abaxially with their closed-up of the leaf bases (from left); C. Inflorescence (front view); D. Cataphyll, spathe (back view), and spadix (from left); E. Close-up of pistillate (E1), sterile interstice (E2) and staminate zones showing free individual staminate flowers (a red arrow, E3); F. Closed-up of appendix; G. pistillate zone after anthesis with lower spathe; H. Fruit spathe (back and front views); I. Longitudinal section of fruit spathe and infructescences (from left).

FIGURE 4. Vietnamocasia dauae. A. Habit; B. Details of leaf base; C. Apical part of stem showing cataphylls of infructescence and continuation shoot; D. Inflorescence; E. Spadix; F. Ovary (top view); G. Ovary (side view); H. Cross-section of ovary; I. Synandrodes, top view; J. Synandrodes, side view; K. Stamen, side view; L. Stamens, top view; M. Stamens, side view; N. Infructescence.