Curcuma arracanensis W.J.Kress & V.Gowda, 2012

Gowda, Vinita, Kress, W. John & Htun, Thet, 2012, Two new species of Gingers (Zingiberaceae) from Myanmar, PhytoKeys 13, pp. 5-14 : 7-8

Curcuma arracanensis W.J.Kress & V.Gowda sp. nov. Fig 2 Plate 2.

Diagnosis.

A new species in the genus Curcuma differing from other members of the genus known from Myanmar in the inflorescence borne well above the surface of the ground at the apex of a leafy shoot, deep maroon inflorescence bracts, and very conspicuous, bright orange flowers.

Type.

Myanmar: Rakhine State: 57 miles from Taung-gok towards Pyay, steep hillsides of cloud forest in fine scree soil, 795 m, 18°38'15"N, 94°38'97"E, 20 June 2003, W. J. Kress, Aye Pe, Than Than Htay, Win Win Aung, and M. Bordelon 03-7328; living collection cultivated at the Smithsonian Botany Research Greenhouses as USBRG 2003-061, 20 June 2003. W. J. Kress 03-7328 (holotype: US! [US 3572390, barcode 00940953; isotypes RAF!; E!).

Description.

Medium herb to 85 to 130 cm in height; rhizomes compact, yellow internally, with numerous white tubers (yellow internally). Leafy shoots loosely clumped, disarticulating during dry season, 3 to 5-leaved, with basal sheaths green with red speckles, glabrous, 20-22 × 4-5 cm. Plane of distichy parallel to rhizome. Leaves 60-70 cm in length, glabrous and coriacious; petiole 19-23 0.7-0.8 cm, glabrous, green with small red speckles, deeply grooved in cross-section, margin entire, smooth; ligule medium-sized, 1.5-3.2 cm in length, bi-lobed, thin and translucent, pale yellow green, glabrous; blade 43-49 × 17-20 cm, narrowly ovate, midrib below green with sparse red speckles, glabrous, base cordate, subequal, apex caudate, adaxial surface dark green. Inflorescence terminal on relatively long leafy shoot, erect 19-25 cm in height; peduncle 2-5 cm in length, glabrous, green to deep maroon red; rachis short; inflorescence bracts 25-30 per inflorescence, 2.4-2.9 × 2.5-3.4 cm, spirally arranged and imbricate, each fused at base to adjacent members ( “pouched’), 40-50° from vertical axis, glabrous, green basally to deep red maroon distally; no coma. Cincinni one per bract containing 3-4 flowers, maturing from base to apex of inflorescence; bracteoles not tubular, 13-15 × 4-6 mm, translucent, glabrous, white with short red apex. Flowers with tubular calyx, 16-22 mm long, tri-lobed, sparsely hirsute with very short hairs, pale yellow orange; corolla tube 2.8-3.5 cm, orange to pale orange, glabrous, with lobes not reflexed, 19-22 mm in length; lateral staminodes fused to base of filament of fertile anther, 13-17 × 7-10 mm, bluntly acute, glabrous, orange; labellum 18-22 × 15-18 mm, spatulate, shallowly bi-lobed at apex, glabrous, yellow orange with deep orange central stripe and reddish margins, lobes not flared; fertile stamen with filament 7-9 mm long, 4-5 mm wide, glabrous, orange, anther versatile, 10-12 × 4.5 mm, thecae elongate with minute, blunt spurs, glabrous, orange, crest much reduced extended <1 mm beyond thecae; stigma shallowly cup-shaped, ovary tri-locular, 3-5 × 3-4 mm, glabrous, pale yellow or green, placentation axile. Epigynous (stylodial) nectaries 2, rounded, 2.4-2.8 mm long, with scattered minute hairs, pale orange to cream-colored; a collar of short hairs forming nectar chamber on inside of corolla tube 5 mm above apex of ovary. Fruit and seeds unknown.

Distribution.

This species is known only from the area around the type locality in Rakhine State, Myanmar.

Ecology.

Unlike many species of Curcuma , which are found in the understory of seasonally dry monsoonal forests, Curcuma arracanensis inhabits open areas in evergreen cloud forest.

Etymology.

This species is named for the region formerly known as Arrakan, an earlier name for today’s Rakhine State in Myanmar.

Common name.

The local name for this species is "Tauk tar phu" in the Burmese language.

Other specimens examined.

Known only from the type specimen. Collections measured WJK 03-7328; USBRG 2003-061.

Conservation status.

Because this species is only known from a single locality in Myanmar and the habitat in which it is found is steadily declining due to deforestation, we categorize it as critically endangered under criteria B and D following the IUCN guidelines ( IUCN Standards and Petitions Subcommittee 2011).

Relationships.

The relationship of Curcuma arracanensis to other members of the genus is not known at present. The anther shape is similar to that found in Curcuma petiolata Roxb (distributed from India to Malaysia including Thailand) and may suggest evolutionary affinities to species allied to this taxon. Further molecular and morphological analyses are needed to determine more precise relationships.

Figures

Figure 2. Curcuma arracanensis W. J. Kress & V. Gowda. A Habit of flowering plant B Tuberous rhizome C Ligule D Bracteole E Flower, lateral view F Flower, frontal view G Flower, cut-away view showing style and anthers H Base of flower, cut-away view showing style, epigynous nectaries and placentation I Placentation, cross section. WJK 03 - 7328 (US).

Plate 2. Curcuma arracanensis W. J. Kress & V. Gowda. A Habit B Flower, frontal view C Inflorescence D Rhizome. WJK 03 - 7328 (US).