Aristolochia annamensis Do, Wanke & Neinhuis, 2015

Do, Truong Van, Neinhuis, Christoph & Wanke, Stefan, 2015, A new species of Aristolochia subgenus Siphisia (Aristolochiaceae) from central Vietnam, Phytotaxa 220 (1), pp. 69-76 : 70-74

Aristolochia annamensis Do, Wanke & Neinhuis , sp. nov. ( Figures 1 & 2 )

Aristolochia annamensis is most similar to Aristolochia xuanlienensis and A. coadunata but it differs from these two species by the following characters: leaf base truncate to slightly cordate; upper part of the perianth tube strongly constricted, straight oblong cylindrically-shaped without veins, 3–3.2 cm long, uniformly dark-purple; limb subcordate, margin of three lobes somewhat recurved but not revolute, inner surface smooth; throat white to yellowish-white, densely covered with purple dots.

TYPE:— VIETNAM. Thua Thien Hue : Phu Loc , Loc Tri , Ngu Ho, Bach Ma National Park, 16°11’28.80”N, 107°51’27.82’’E, elev. 1240 m, 11 November 2014, T. V. Do 70 (holotype: VNMN!; isotype: DR!) .

Perennial woody lianas, 12–18 m long, with numerous fasciculate and cylindrical roots. Stem terete, young branches slender, glabrescent, with a shallowly furrowed corky bark when mature, internodes 13–15 cm long. Petiole 4–5(–6) cm long, straight, glabrescent. Leaf blade lanceolate to lanceolate-ovate, 12–18 cm long, 6–8 cm wide, subcoriaceous, base truncate to slightly cordate, apex acute, the adaxial surface dark green and glabrous, the abaxial surface densely villous, glaucous, trinerved at base, basal pair exceeding nearly half the leaf length, secondary veins four to five pairs, pinnate, venation reticulate, prominent on the abaxial surface, flattened on the adaxial surface, margin entire. Inflorescences cymose, on old woody stems, solitary, 3–4-flowered, clearly separated from each other. Inflorescence axis 4–6 cm long, slightly curved, densely brown pubescent. Bracteoles clasping, conspicuous, triangular, 2–2.5 mm long, 1.5–1.8 mm wide, sessile, both sides densely brown pubescent. Pedicel 2.5–2.8(–3) cm long, straight, densely brown pubescent. Ovary 0.8–1 cm long, 0.2–0.3 cm in diam., densely brownish villous. Perianth horseshoe-shaped (lateral view), 5.5–5.8(–6) cm high, outside whitish-purple, sparsely hairy with parallel dark-purple veins, inside glabrous, with the exception of the utricle. Utricle indistinct from the tube, cylindrical, inflated, 0.8–0.9 cm long, 0.6–0.8 cm in diam., inside with dark-purple patches and a dense arrangement of trichomes. Tube consisting of two parts with differentiation between lower and upper part of tube: lower part horseshoe-shaped, strongly inflated, 1.1–1.2 cm in diam., and upper part straight oblong cylindrically-shaped without veins, 3–3.2 cm long, 0.4–0.5 cm in diam., uniformly dark-purple. Limb with three unequal lobes, valvate during pre-anthesis: two deltoid lateral lobes, 1.2–1.4 cm wide, 0.5–0.6 cm high, and a triangular middle lobe, 0.6–0.7 cm wide, 0.9–1 cm high, margins of lobes somewhat recurved but not revolute during anthesis, forming a subcordate limb, with two lateral lobes broader than middle one, 2–2.2 cm wide. Expanding lobes displaying a dark-purple, smooth inner surface, without veins or warts. Throat white to yellowish-white, densely covered with purple dots, 1–1.1 cm wide. Annulus absent. Gynostemium 3-lobed, cylindrical, purple, 5–6 mm high, 3–4 mm in diam., lobes with long, truncate and constricted apices. Anthers 2.2–2.5 mm long, yellow. Capsule elongate-oblong, 5–6 cm long, 1.8–2.2 cm diam., distinctly 6-ridged, yellowish-green, densely brown villous, basipetally dehiscent. Seeds ovoid, 6–7 mm long, 4–5 cm in diam., non-winged, one surface convex, another surface concave, both surfaces smooth.

Phenology: — Aristolochia annamensis has been observed flowering from September to November and fruiting from October to December.

Distribution and habitat: — Aristolochia annamensis is currently known from many populations among the protected forest areas in central Vietnam throughout Thua Thien Hue province to Quang Nam province ( Figure 3). This species is known to grow in broad-leaved evergreen forests, mostly along streamlet edges, at 700–1240 m elevation.

Conservation status: —The type specimens were collected in the core-zone of Bach Ma National Park, a large evergreen forest area that is well protected. Additionally our field observations from other localities indicate that there are many populations with healthy individuals as well as saplings that regenerate in well-protected habitats. Thus, the new species is probably not at risk (LC) according to IUCN (2001).

Etymology: —The specific epithet refers to the former name of central Vietnam where it occurs.

Vernacular name: —Common names in Vietnamese for this species are Mộc hƯƠng Trung Bộ, Phòng kỷ Trung Bộ.

Morphological affinities: — Aristolochia annamensis is most similar to Aristolochia coadunata Backer (1919: 154) occurring in Indonesia (Sumatra and Java) by sharing an upper part of tube oblong cylindrically-shaped and A. xuanlienensis N.T.T. Huong, B.H. Quang & J.S. Ma (2014: 176) occurring in northern Vietnam by sharing a throat densely covered with purple dots. However, A. annamensis differs from A. coadunata by the following characters: leaves (lanceolate to lanceolate-ovate, truncate to slightly cordate at base vs. ovate-oblong to lanceolate, deeply cordate at base), upper part of tube (straight oblong cylindrically-shaped, 3–3.2 cm high vs. obliquely oblong cylindrically-shaped, 3–4.5 cm high), limb (subcordate with three distinct lobes vs. subrotundate with three obscure lobes), throat (white to yellowish-white, densely covered with purple dots vs. yellow without dots). Also, the new species is clearly distinguished from A. xuanlienensis by the diagnostic characters of perianth (whitish-purple vs. white), upper part of tube (straight oblong cylindrically-shaped, uniformly dark-purple without veins vs. obliquely broad funnel-shaped, white with purple veins), limb (subcordate with three distinct lobes, somewhat recurved, but not revolute vs. trumpetshaped with three fused lobes, strongly revolute), inner surface of limb (smooth vs. densely covered with purple papillate). Detailed comparisons are provided in Table 1.

Additional specimens examined (paratypes): — VIETNAM: Thua Thien Hue. A Luoi district, 16 May 1983, Nghi 3160 (NIMM).— Da Nang. Ba Na hill, 18 Novemver 2014, T.V. Do 62 (VNMN).— Quang Nam. Nui Thanh district, Tam Tra commune, 25 September 1983, Bon & Phong 2959 (NIMM), Tam My commune, 1 October 1983, T. Nguyen 466 (NIMM). Tay Giang district, Lang Community, Nal stream, 29 June 2003, T. Nguyen & P.D. Ngo 7124 (NIMM). Song Thanh Nature Reserve, 15°38’59.84”N, 107°36’00.93’’E, elev. 890 m, 3 December 2014, T.V. Do 75 (VNMN).

Figures

FIGURE 1. Aristolochia annamensis. A. Abaxial leaf surface. B. Solitary cyme on old woody stem. C. Lateral view of open flower. D. Front view of open flower. E. Oblique view of open flower. F. Close up of gynostemium. G. Capsule. Drawn by Bernd Schulz from the type specimen.

FIGURE 2. Aristolochia annamensis (A–E). A. Abaxial leaf surface. B. Solitary cymes on old woody stem. C. Front view of open flower showing inner surface of limb lobes smooth. D. General view of open flower. E. Capsule (white arrow showing a triangular bracteole).— Aristolochia xuanlienensis. F. Front view of open flower showing inner surface of limb lobes densely covered with papillate. A–E photos by Lu Thi Ngan at the type locality. F photo by Nguyen Thi Thanh Huong.