Amorphophallus kienluongensis V.D. Nguyen, Luu & Hett., 2016

Amorphophallus kienluongensis V.D. Nguyen, Luu & Hett. View in CoL , sp. nov. — Fig. 1 View Fig

Diagnosis: Amorphophallus kienluongensis resembles A. brevispathus in having a spathe shorter than the spadix and the male flowers clustered in groups of 6 or more. It differs from A. brevispathus in the stigma diameter exceeding that of the ovary and in having a tuber without long rhizomatous offsets.

1 Institute of Ecology and Biological Resources – Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet road, Nghia Do, Cau Giay, Hanoi, Vietnam; corresponding author e-mail: vandu178@yahoo.com.

2 Southern Institute of Ecology – Vietnam Academy of Science and Technol- ogy, 1 Mac Dinh Chi, District 1, Ho Chi Minh City, Vietnam; e-mail: hongtruongluu@yahoo.com.

3 Von Gimborn Arboretum,Velperengh 13, 3941 BZ Doorn, The Netherlands; e-mail: hetter@xs4all.nl.

Type.Nguyen Quoc Dat & Luu Hong Truong, KG008 (holotype SGN), KG 001 View Materials (paratype VNMN,leaf), KG002 (paratype VNMN,inflorescence), KG003 (paratype L, leaf), KG004 (paratype L, inflorescence), KG 010 (paratype HN) , Viet Nam, Kien Giang Province, Kien Luong District, Ba Tai Hill , 2 June 2011; KG008 (paratype HN,leaf collected from the type-plant in cultivation, 2012) .

Etymology. The species epithet kienluongensis is derived from the name of the Kien Luong district of the Kien Giang province, Vietnam.

Seasonally dormant, tuberous herb, 20–50 cm tall. Tuber globose or slightly elongate, producing depressed globose offsets, 3.5–7 cm long, 2–6 cm thick; flesh white. Leaf solitary. Petiole cylindric, 24–90 cm long, 1–2.6 cm diam at base, smooth, light green or dull brownish green. Lamina moderately decompound, 20–55 cm diam. Leaflets elliptical, elongate obovate, or lanceolate, 6–18 cm long, 3–5 cm across at the widest point, base attenuated, oblique, acute, or acuminate, acumen 1.5–2 mm long, upper surface medium to dark green, glossy; lateral veins abundant, prominent on the lower surface, distance 6–7 mm between veins, sometimes with intermediate veins; collective vein 2–4 mm distant from margin. Inflorescence appearing without the leaves. Peduncle 15–45 cm, 0.7–2 cm diam at base, smooth, light green. Spathe considerably shorter than spadix, broadly triangular, 3.5–7 cm long, 5–9 cm wide at the base, enclosing the entire fertile part of the spadix, base strongly convolute, whitish green on both surfaces, slightly darker green at the base, inside surface with a prominent wax layer. Spadix much exceeding spathe, sessile, 10–15 cm long; female portion slightly obconic, 1.3–1.5 cm long, 1–1.2 cm diam at the base, 1.3–1.5 cm diam at the apex, ovaries distant; male portion obconic, 4.0– 5.4 cm long, 1.5 cm diam at the base, 2.4 cm diam at the apex; appendix elongate-conic, 6–11 cm long, 2–3 cm diam at the base, top acute or obtuse, surface smooth, off-white. Ovary globose, pale green, unilocular, 1 mm high, 2 mm diam, ovule solitary, basifix; style prominent, thick, whitish green, 1 mm long; stigma 1.2–2.2 mm diam, wider than ovary, dirty whitish, disciform with a concave depression, slightly lobed, surface uneven. Male flowers consisting of 3–5 stamens but flowers from the base to the top of the male zone increasingly clustered to form groups with 8 or more stamens; stamens 0.8–1.5 mm long, 1.5–3 mm diam; filaments very short, 0.2–0.4 mm long; anthers truncate, 1 mm long, yellow, connective very thin, rupturing fully at male anthesis to create a single common pore. Infructescence slightly elongate, obconical, to 7 cm long and 2 cm diam at the base and 3 cm at the apex, berries lax, 1.6–2.0 by 1.0– 1.4 cm, elongate ovate, shiny dark blue when mature.

Distribution — Only known from the Kien Luong Karst system, Kien Giang Province, Mekong Delta, southern Vietnam.

Ecology — Coastal forests on karst limestone, 5–50 m altitude. Flowering in June and fruiting in September.

Conservation status — Amorphophallus kienluongensis is known to occur only on several small adjacent isolated limestone hills including Khoe La, Hang Tien, Chua Hang, and Ba Tai in the Kien Luong district. Khoe La is quarried for cement manufacture, and it is foreseen it will be destroyed within the next years. The area in which the species grows is less than 3 km 2 and combined with threats from quarrying the species is recommended to be ranked as globally Critically Endangered (CR) according to the IUCN Red List criteria (v. 2.3) (http:// www.iucnredlist.org).

Specimens studied. Nguyen Van Du s.n., Viet Nam, Kien Giang province, Kien Luong district , Chua Hang, 29 Nov. 2009 ( HN, leaf) ; Luu Hong Truong KG 250 ( SGN,inflorescence), Hang Tien, Kien Luong distr.; Luu Hong Truong KG 251 ( SGN, inflorescence), KG252 ( SGN, leaf), Khoe La , Kien Luong distr. , 17 June 2010 ; Nguyen Quoc Dat & Luu Hong Truong, KG 005 ( SGN, inflorescence), KG 006 ( SGN, leaf), KG007 ( SGN, leaf), KG 008 ( SGN, inflorescence), KG009 ( HN, inflorescence) and KG011 ( SGN, leaf) , Viet Nam, Kien Giang province, Kien Luong district, Chua Hang , 2 June 2009 .

Notes — The combination of characters in A. kienluongensis of male flowers in large groups, a rupturing connective, and berries ripening blue suggests the species to be a member of a subclade of five other species with this same unique character combination: A. atrorubens Hett. & Sizemore ( Hetterscheid & Van der Ham 2001, Thailand), A. brevispathus ( Thailand), A. gallowayi Hett. ( Hetterscheid 2006, Thailand), A. interruptus Engl. & Gehrm. ( Engler 1911, N Vietnam), and A. prolificus ( Hetterscheid 2006, Thailand). Sedayu et al. (2010: 482, f. 3) failed to resolve these species as a monophyletic group although only two species ( A. brevispathus and A. interruptus ) were included. As yet unpublished molecular phylogenetic information based on 130 species, resolved the above listed species as a monophyletic group with full statistical support (Baysian post. prob. = 1).