Curcuma papilionacea Soonthornk., Ongsakul & Škorničk., 2020

Soonthornkalump, Sutthinut, Ongsakul, Annop, Dolaji, Aumdah & Leong-Škorničková, Jana, 2020, Curcuma papilionacea (Zingiberaceae), an unusual new species from southern Thailand, Phytotaxa 432 (1), pp. 11-16 : 12-15

Curcuma papilionacea Soonthornk., Ongsakul & Škorničk. sp. nov., subgen. Hitcheniopsis , Fig. 1 , 2 .

Curcuma papilionacea is unique in the genus by the following combination of characters: absence of epigynous glands, presence of Lshaped anthers, inflorescences composed of green bracts without coma, and flowers with a pea-like appearance.

Type: — THAILAND. Satun province, La-ngu Dist., Kamphaeng Subdistr., growing in rubber tree plantation close to the foothill of Khao Lek-Si (Kăo-Lâyk-Sèe), 6°54′53″N, 99°46′15″E, 25 m, 25 June 2019, Annop Ongsakul, Sutthinut Soonthornkalump & Aumdah Dolaji Ong-1001 (holotype BKF! (inclusive spirit), isotype QBG!, SING! (inclusive spirit).

Rhizomatous herb, ca. 60–80 cm height. Rhizome ovoid, ca. 2.8–3.5 × 1.4–2.3 cm, occasionally with one or two lateral branches ca. 1.5–3 × 0.5 cm, yellowish-brown externally, covered with rust-coloured and decayed scales, white internally; root tubers, ovate to fusiform, 1–1.8 × 0.5–1.5 cm, light brown externally, white internally. Leafy shoot with 3–4 leaves at anthesis; pseudostem up to 40 cm height, composed of 2 leafless sheaths and 3–4 leaf-bearing sheaths, all plain green, glabrous; ligule up to 2.5 mm long, obscurely bilobed, hyaline, greenish-white, translucent, glabrous; petiole 39–43 cm long, canaliculate, green, glabrous; lamina elliptic, 27–33 × 11–13.5 cm, adaxially green, abaxially somewhat paler, glabrous on both sides, midrib green, margin entire, glabrous, base rounded, apex acuminate to narrowly acuminate. Inflorescence central, peduncle basally obscured within pseudostem, and exceeding it by 18–30 cm, glabrous; thyrse ca. 9.5–11 × 1.5–2 cm, composed of 7–8 fertile bracts, coma bract absent; bracts ca. 2.5–2.7 × 2.3–2.4 cm, broadly irregularly obovate, green with pale green venation and mostly also with two greenish-white patches (one on each side of the bract), puberulent on both sides, connate in basal 2/3, apex obtuse, reflexed; cincinni with up to 6 flowers at the basal bracts, gradually decreasing distally; bracteoles narrowly triangular and curved, up to 9–10 mm long, up to 5–6 mm wide at base, white, glabrous. Flowers 2.9–3 cm long, slightly exserted from bracts; calyx 10–12 mm long, 3-toothed, with unilateral incision, 1–1.5 mm, semi-translucent, white, glabrous; floral tube 1.5–1.7 cm long, narrowly cylindrical at base, slightly widening distally, white, semi-translucent, externally glabrous, and internally glabrous with glandular hair near throat; dorsal corolla lobe ca. 10 × 5 mm, elliptical, with concave apex, white or pale purple with purple tinge at apex and margins, glabrous; lateral corolla lobes ca. 8–10 mm long, 3–4 mm wide at base, elliptic to slightly triangular with obtuse, concave apex, reflexing soon after anthesis, white or pale purple with purple tinge at apex and margins, glabrous; labellum ca. 13–15 × 7 mm, narrowly obovate, obscurely bifid with an incision ca. 1.5 mm long, white to pale purple with bright red bands at sides basally, gradually turning bright violet towards apex, median yellow, positioned at middle third of labellum and extending as band of fine white hairs towards apical incision, glabrous on both sides except distal part of median; lateral staminodes ca. 13–14 × 7–8 mm, unequally obovate to rhombic, adnate to labellum in basal ¼, white or pale purple with red band basally on side adjacent to labellum, apex slightly reflexed, glabrous on both sides. Stamen 8–9 mm long; filament 3 mm long, 4 mm broad at base, less than 2 mm at point of attachment, white, glabrous; anther spurred, L-shaped (110°–120°), ca. 8–8.5 mm (measured across the L-shape), slightly divergent at middle and convergent at apices creating a narrow central opening, white with tips of spurs pale yellow, glabrous, anther crest absent, anther thecae ca. 3–3.5 mm long, dehiscing along entire length, pollen white. Epigynous glands absent. Style white, glabrous; stigma capitate, with two prominent lobes, ca. 0.75 mm wide, white; ostiole with irregularly serrulate margin, glabrous, facing forward. Ovary 3–4 × 2–2.5 mm, trilocular, placentation axile, white, glabrous. Fruit a globular trilocular capsule, 1–1.2 cm diameter (almost ripe), green, glabrous, dehiscing irregularly, containing 20–25 seeds (most well-developed, some aborted); seeds irregularly obovoid, 3–4 mm long, light brown (almost ripe), shiny, enclosed in translucent white, laciniate aril.

Distribution and ecology:— Known only from Satun province in southern Thailand. It grows in sandy clay loam at the edge of disturbed forest and rubber tree plantations. Some populations were found in humus pockets in limestone under semi-shade at 0–50 m a.s.l.

Phenology:— Flowering starts in the early part of the rainy season and lasts from June–July. Fruiting occurs from mid-June and likely continues until early August. The plant goes dormant in January. The flower opens in the morning and lasts a single day. If exposed to strong sunlight and high temperature, the flowers will wilt earlier.

Preliminary IUCN assessment: — The species is currently known only from three populations with approximately 200, 100 and 5 adult individuals respectively, placing the taxon into the Endangered category using criterion D1. As the Extent of Occurrence (EOO) is only 0.262 km 2, and Area of Occupancy (AOO) is 8 km 2, and moreover, the area is used for rubber plantations and is not under any legal protection, it is evident that suitable habitat in the area is severely fragmented and continuing to decline in area, extent and quality. Furthermore, this species occasionally appears on sale at a local market as an ornamental. We therefore propose to treat it as Critically Endangered (CR B1a b(iii,v)+B2ab(iii,v). Ex situ conservation is strongly recommended and several plants are being currently conserved at Sulee Nursery and further propagated through seeds as well as through in vitro approach. Supplying the horticulture market with in vitro propagated stock will hopefully ease the pressure to harvest this species from the wild.

Etymology:— The specific epithet is derived from Latin ‘ papilionaceus ’, which means butterfly-like. It refers to the pea-like appearance of the flower.

Vernacular names and uses:— No uses were reported, except occasional sale of the plant as an ornamental. As this species is likely to become more widespread in horticulture we propose Thai vernacular name Pathumma-Thin-Tai (Bpà-Tum-Maa-Tìn-Dtâi;) [Pathumma = the Thai common name for Curcuma species, Thin-Tai = native to the southern part of Thailand].

Additional specimens examined (paratypes): — THAILAND. Satun province, La-ngu Dist. , Kamphaeng Subdistr., 25 m a.s.l., 19 July 2017, Annop Ongsakul Ong-0984 ( BK) ; ibidem, growing in rubber tree plantation close to the foothill of Khao Lek-Si (Kăo-Lâyk-Sèe), 6°54′9.14″N, 99°46′14.20″E, 27 m a.s.l., 25 June 2019, Annop Ongsakul, Sutthinut Soonthornkalump & Aumdah Dolaji Ong-1002 ( PSU (inclusive spirit)) .

Note:— As mentioned in the diagnosis, this species is very easy to distinguish from all other species of Curcuma by its pea-like flower. By its flower colour, which combines violet, dark red, white and yellow, it resembles three species in subgen. Hitcheniopsis , namely C. rhabdota , C. saraburiensis and C. alismatifolia Gagnep. With the first two species, it also shares the prominently plicate leaf blades, but it is easily distinguished from both of them by its inflorescences with no coma. From C. alismatifolia , it can also be distinguished by the lack of coma bracts, and plicate leaves (compared to narrowly elliptic and rather smooth leaf blades in C. alismatifolia ). It may also be considered somewhat similar to Curcuma harmandii , which has inflorescences composed of green bracts without coma, but these bracts are very different in shape with narrowly acute apices, and the flowers are greenish white overall, with a yellow median band on a labellum bordered by a pink tinge, and narrowly oblong lateral staminodes. In addition, C. papilionacea occurs only in southern Thailand, while the above four species are confined to Central, Eastern and Northeastern Thailand.

Figures

FIGURE 1. Curcuma papilionacea Soonthornk., Ongsakul & Škorničk.. A–B. Habitat. C. Plant. D. Seeds.E.Almost ripe fruit. F. Rhizome with root tubers. Photographed by S. Soonthornkalump.

FIGURE 2. Curcuma papilionacea Soonthornk., Ongsakul & Škorničk. A–B. Inflorescence. C. Flower (semi-top view). D. Inflorescence (top view). E–G. Flower viewed from different angles. H. Labellum with lateral staminodes attached. I. Stamen in side and front view. Photographed by S. Soonthornkalump, A. Dolaji and A. Ongsakul.