This new species is morphologically similar to Aristolochia championii Merill & W.Y. Chun, Aristolochia vallisicola T.L. Yao, Aristolochia petelotii O.C. Schmidt and Aristolochia versicolor S.M. Hwang, but is distinguishable from these species by the following diagnostic characters: petiole 1.5–2.5(–3) cm long; lamina elliptic to oblong-elliptic; peduncle 1.5–2 cm long, covered with yellow-brown trichomes; perianth limb bell-shaped, 2–2.5(–3) cm wide, exclusively purplish-pink on both sides, no blotches or veins are visible; perianth margins recurved; flower tube mouth slightly darker than the remaining perianth limb; perianth tube pale yellow to whitish and the entire back of the perianth limb and tube covered with yellow-brown trichomes.

VIETNAM. Quang Binh province: Minh Hoa district, Hoa Luong community, 17°47'5.00"N, 105°52'20.05"E, elev. 380 m, 3 April 2013, T.V. Do 39 (holotype: VNMN; isotype: DR).

Perennial woody lianas. Roots numerous, fasciculate and cylindrical. Stems terete, densely yellow-brown villous when young, older stems with corky bark, glabrous. Petiole 1.5–2.5(–3) cm long, straight, densely covered with yellow-brown trichomes; lamina elliptic to oblong-elliptic, (6–)8–13(–14) cm long, 3–5(–6) cm wide, subcoriaceous, base subcordate to auriculate, with a shallow sinus 3–4 mm deep, (1–)1.5–2 mm wide, apex acute, adaxially glabrous, dark green, abaxially densely yellow-brown villous, basal veins 3, palmate, secondary veins 7–8 pairs, pinnate, venation densely reticulate and prominent on both sides. Flowers terminal, solitary, but accompanied by a lanceolate scale-like bracteole, (2–)3 mm long, (1.5–)2 mm wide, sessile, inserted near base of the peduncle, conspicuous, persistent. Peduncles 1.5–2 cm long, pendulous, purple, densely hirsute. Peduncles, bracts and perianth densely covered by yellow-brown pluricellular hairs. Perianth S-shaped, (3–)3.2–3.5 cm long, outside densely yellow-brown hirsute with obscure, parallel veins, inside smooth. Ovary oblong, (0.8–)1–1.2 cm long, 0.3–0.4 cm diam., yellowish-green, densely hirsute, 6-locular, ovules numerous, usually in one series. Utricle ovoid, (1.2–)1.5–1.8 cm long, 0.5–0.6(–0.8) cm diam., externally white, inner surface basally with a dark-purple patch and distally with a white patch; tube strongly curved at its base, parallel and in close contact with the utricle, narrower than the utricle, cylindrical, 0.9–1.0 cm long, 0.4–0.5 cm diam.; limb three-lobed, bell-shaped, 2–2.5(–3) cm diam., purplish-pink on both sides, without any blotches or veins visible, outer surface densely hirsute, inner surface smooth, the three unequal lobes valvate in preanthetic flowers, the lateral lobes broadly deltoid with acute apex, the lower (median) lobe semicircular, during anthesis bell-shaped and with the margins recurved; throat circular, dark-purple, densely papillose; annulus present, formed by an ellipsoid flange, dark-violet; gynostemium three-lobed, lobes with obtuse apices, smooth, (3–)4–5 mm high, 2–3 mm diam., white; stamens six in one serie of three pairs; anthers oblong, (2–)2.5–3 mm long, yellow, tetralocular, longitudinally dehiscent. Capsules not seen.

Phòng Kỷ Quảng Bình (in Vietnamese).

Aristolochia quangbinhensis is known from a single population found on the north-eastern slope of a mountain range bordering the buffer zone of Phong Nha-Ke Bang National Park in the Hoa Luong community, Minh Hoa district, Quang Binh province (Fig. 3). It might also be present in Laos P.D.R., because of the proximity of the Khammouan province with Central Laos.

Aristolochia quangbinhensis occurs in humid mountain sites, in the understory of disturbed lowland evergreen broad-leaved forest and mainly evergreen scrubs. Dominant plants at the type locality are Annonaceae (Desmos spp.), Apocynaceae (Marsdenia spp., Wrightia spp.), Fabaceae (Millettia spp.), Lauraceae (Machilus spp., Litsea spp.), Malvaceae (Sterculia spp.), Pandaceae (Microdesmis spp.), Phyllanthaceae (Antidesma spp., Aporosa spp., Glochidion spp.), and Rubiaceae (Randia spp.).

Flowering specimens have been collected in April and May but it is possible that blooming already begins in March.

The specific epithet refers to the type locality.

In the past, large areas of primary, broad-leaved, evergreen forest covered the Hoa Luong community. Excessive logging, however, resulted in the loss of large extensions of primary forest. Although logging was prohibited in the 1990s, local farmers continued to impose strong pressure on the remaining forest patches converting it mostly into corn and soybean fields. As a result, the flora of the area should be regarded as threatened by extinction. Within the area, Aristolochia quangbinhensis is known from a single population; in fact, during the present study, only two healthy individuals were located growing about 50 m apart from each other. Therefore, the new species is assigned a preliminary status of vulnerable (VU D2) according to IUCN Red List criteria (IUCN 2013), indicating a population with a very restricted area of occupancy (typically less than 20 km²) or the number of locations (typically five or fewer) being both at hand for Aristolochia quangbinhensis. The lack of data currently does not allow a final risk evaluation, but the species might also be regarded as endangered (EN).