Curcuma arida Škorničk. & N.S.Lý, 2015

Leong-Škorničková, Jana, Lý, Ng ọc-Sâm & Nguy ễn, Qu ốc Bình, 2015, Curcuma arida and C. sahuynhensis, two new species from subgenus Ecomata (Zingiberaceae) from Vietnam, Phytotaxa 192 (3), pp. 181-189 : 182-185

Curcuma arida Škorničk. & N.S.Lý , sp. nov.

Similar to C. pambrosima (subgenus Ecomata ) by the shape of the inflorescence, but differs in shape and colour of the anther (anthers white with bright yellow anther crest and two filamentous, hook-shaped spurs in C. arida versus light yellowish anther with prominent 1.5 mm long thick spurs which are curved inwards in C. pambrosima ).

Type: — VIETNAM. Ninh Thuận Province: Ninh H ải Dist., Vĩnh H ải Commune, Thái An village, Núi Chúa National Park, 11°41′16.0″N, 109°09′25.2″E, 75 m, Jana Leong-Škorničková, Nguy ễn Quốc Bình, Aung Thame & Edward Ong JLS-2575 (holotype SING (inclusive spirit), isotypes E, P, VNM, VNMN (inclusive spirit)). Fig. 1 & 2 .

Small rhizomatous herb to 0.5 m tall. Rhizome ovoid, 3–4 × ca 1 cm, occasionally with a thin branch pointing downwards, light brown externally, yellow internally, strongly aromatic; root tubers ovate to fusiform, 2.4–4.8 × 0.9–2.3 cm, externally brown, internally whitish, buried deeply in the ground. Leafy shoots with usually 3–4 leaves at the time of flowering; pseudostems to 15 cm long, green, composed of sheathing bracts and leaf sheaths; sheathing bracts 2–3, green, soon turning papery dry and decaying, glabrous; leaf sheaths green, glabrous; ligule up to 5 mm long, bilobed (lobes acute to acuminate), hyaline, greenish white, translucent, glabrous; petiole 1–9 cm long (petiole of first leaf shortest, innermost leaves longest), canaliculate, green, glabrous; lamina slightly unequal, ovate to elliptic, up to 35 × 13 cm, slightly coriaceous, smooth (very obscurely plicate), adaxially green, glabrous, abaxially lighter green, glabrous, midrib green, glabrous on both sides, base rounded, slightly oblique, apex attenuate, puberulent. Inflorescence central, with peduncle obscured within pseudostem; peduncle up to 20 cm long, up to 7 mm in diameter, light green in parts exposed to light; spike 10–20 cm long, 4–6 cm in diameter (measured at the middle part), with no obvious coma, composed of 15–35 bracts; bracts 3–5 × 2.0– 4.5 cm, broadly to narrowly ovate to trullate, broader at base, narrower towards the apex, whitish to light green at basal half with increasing purple tinge towards the apices, both sides glabrous, connate in lower 1/3–1/4, apices acute to narrowly acute, reflexed; cincinni with 4 flowers at the base of the inflorescence, 1–2 flowers at the top; bracteoles small, narrowly triangular and curved, up to 2 mm wide at base, up to 9 mm long, white with purple–pink tinge at apex, sometimes fully reduced (missing). Flowers 4–5 cm long, exserted from bracts; calyx 10–13 mm long, 3-toothed, with 5–6 mm long unilateral incision, glabrous, semi-translucent white, apices of teeth convex, tinged with dark pink; floral tube 2.2–3.0 cm long, narrowly cylindrical at base for ca 1.5–2.0 cm above the ovary, funnel-shaped at apex, white externally and internally, externally glabrous at base, puberulent at funnel-shaped part, internally puberulous, with dorsally placed loose groove holding the style; dorsal corolla lobe ca 15 × 11–13 mm, triangular-ovate, concave, white or with slight purple tinge at the apex, glabrous, apex mucronate, mucro ca 1 mm; lateral corolla lobes ca 12 mm long, 7–9 mm wide at base, triangular with obtuse, slightly concave apex, white or with slight purple tinge at the apex, glabrous; labellum ca 15–17 × 14 mm, slightly obovate, with an incision up to 7 mm long, cream white at base, turning yellow at apex with bright yellow band running through the apical part of the centre; lateral staminodes 14–16 × 11 mm, unequally ovate to rhombic, white at base, yellow towards apex, glabrous on both sides. Stamen 9–10 mm long; filament 3–5 mm long, 5–6 mm wide at base, ca 1.5 mm wide at the point of connection to connective, white, puberulent (glandular hair); anther spurred, connective sparsely puberulent (glandular hair), anther spurs ca 0.5 mm long, filamentous, hook-shaped, white, anther crest present, 1.0– 1.5 mm long, with obtuse apex, yellow; anther thecae 5 mm long, dehiscing along entire length, pollen white. Epigynous glands two, cream-coloured, 3 mm long, ca 0.8 mm in diameter, with blunt apex. Style white, glabrous; stigma capitate, ca 1 mm wide, creamy white, ostiole ciliate, facing forward. Ovary 2–3 × 2 mm, trilocular, creamy white, glabrous. Fruit a globular trilocular capsule, ca 1.1 cm in diameter (almost ripe), white, glabrous; seeds irregularly obovoid, ca 5 mm long, creamy white to light brown (almost ripe), shiny, enclosed in translucent white, laciniate aril.

Ecology and phenology:— So far known only from the Núi Chúa National Park, where it is restricted in semi-arid forest, growing on rocky slopes in open places or in the undergrowth of shrubby vegetation. Curcuma arida flowers from September to November and fruits from October to December, unlike the majority of other Curcuma species in Vietnam which flower in April to July. This pattern, however, corresponds well with the occurrence of the rainy season in the semi-arid climatic zone of southern Vietnam ( Averyanov et al. 2003).

Distribution and IUCN preliminary assessment:— Curcuma arida is as yet only known from the type locality, where we have counted about 200 adult individuals. Local people informed us that they have seen this species growing also in other lowland locations with similar vegetation type within Núi Chúa NP. They have also shared that they do not use this species economically. With no imminent threat and with the protection given by the National Park status, we suggest treating this species as Data Deficient (DD) until the lack of data on the extent of its occurrence and population sizes can be satisfactorily addressed.

Etymology:— This species grows in one of the driest parts of Vietnam, often intermingled with succulent members of Euphorbiaceae ( Fig. 2 ) and hence the specific epithet ‘ arida ’.

Additional specimens examined (paratypes):— VIETNAM. Ninh Thu ận Province : Ninh H ải Dist., Vĩnh H ải Commune, Thái An village, 11°42’14.67”N, 109°09’26.45”E, 120 m, 20 September 2009, Lý Ngọc Sâm 450 ( SING, VNM) ; ibid. 11°41′27″N, 109°11′14″E, 35 m, 1 November 2010, Lý Ngọc Sâm 489 ( E, P, SING, VNM) .

Notes:— Curcuma arida is similar to C. pambrosima by its inflorescence composed of ovate to trullate bracts that are green to white at the base, gradually tinged pink towards the acute to narrowly acute and reflexed apices, as well as their lack of clear distinction between fertile and coma bracts. The major difference between the two species lies in the floral features of which most conspicuous is the shape of the anthers. Curcuma pambrosima has a light yellowish anther with prominent 1.5 mm long thick spurs that are curved inwards (see Fig. 1D in Leong-Škorničková & Lý 2010), while C. arida has a white anther with a bright yellow anther crest and two filamentous hook-shaped spurs (see Fig. 1G ).

The anther of Curcuma arida is in shape very similar to that of C. vitellina (see Fig. 1D in Leong-Škorničková et al. 2010) and likely catering to a similar pollinator, but the general appearance of the two species is different in leaves (thin and prominently plicate lamina in C. vitellina vs. somewhat coriaceous smooth lamina in C. arida ) as well as the overall inflorescence shape and colour (inflorescence composed of 15–60 creamy white or greenish bracts with obtuse, mildly reflexed apices in C. vitellina vs. inflorescence composed of 15–35 bracts that are green to white at base, gradually tinged by pink towards the acute to narrowly acute and strongly reflexed apices (compare Fig. 1 in Leong-Škorničková et al. 2010 and Fig. 1 presented here).

A revision of extensive herbarium material of Curcuma in various herbaria resulted in a possible match of two specimens deposited in the in the MNHN herbarium in Paris (P). One of them was collected near Phan Rang, while the other near Nha Trang (ca 20 and 60 km air distance respectively). While the conclusive determination is not possible due to lack of flowers/detailed notes (and therefore these specimens are not listed above), it is likely that both specimens represent Curcuma arida .

Figures

FIGURE 1. Curcuma arida. A. Habit and detail of ligule (inset). B. Inflorescence. C. Cincinnus. D. Young fruit. E. Rhizome (scale bar in mm). F. Flower dissection: flower in side view, flower bud, floral tube (with ovary, calyx and stamen attached), corolla lobes, staminodes and labellum, fertile bract (scale bar in cm). G. Epigynous glands, anther (side and front view; scale bar in mm). From type JLS-2575. Photos: J. Leong-Škorničková

FIGURE 2. Curcuma arida in the typical dry habitat at the type locality where it grows on stony slopes under the shrubby vegetation often intermingled with succulent members of Euphorbia. Photo: J. Leong-Škorničková