Aristolochia sanheensis J.Z.Liu, R.Z.Huang & K.Y.Yuan, 2024

Aristolochia sanheensis J.Z.Liu, R.Z.Huang & K.Y.Yuan , sp. nov. ( Fig. 1 View FIGURE 1 )

Type: — CHINA. Yunnan province: Nujiang Lisu Autonomous Prefecture, Lushui city, Luzhang town, Sanhe village , 25.887351ºN, 98.782557ºE, elev. ca. 2200m, 9 March 2024, flowers, J.-Z. Liu et al. 2024030901 (holotype SWFC! GoogleMaps , isotype CANT! GoogleMaps ).

Diagnosis: — Aristolochia sanheensis is similar to A. luudamcui and A. forrestiana J.S. Ma (1989b , 321). It is similar to the former in the appearance of calyx shape which is U-shaped and the color of inner calyx’s basal part of tube and limb, but differs by the triangular limb (vs. non-triangular) in lateral view, the inner limb with (vs. without) the prickly outgrowths, and the upper part of limb separated to ca. 1/2–2/3 (vs. ca. 1/4). Aristolochia sanheensis is similar to A. forrestiana in the appearance of the separated upper part of limb and densely prickly outgrowths of the inner limb, but differs by the inner upper part of calyx tube light yellow with purple red (vs. purple red) at the upper part, the limb triangular (vs. non-triangular) in lateral view, inner surface of limb light yellow (vs. black purple).

Description: —Woody liana, up to ca. 3 m tall. Stems terete, young shoots densely light yellow-brown villous, almost glabrous when aged. Petioles 1.3–5.7 cm long, pubescent. Leaf blades ovate to narrowly ovate, 9.3–19.7 × 4.9–8.4 cm, cordate at base, sinus 1.5–2.8 cm deep, acuminate at apex, young leaves adaxially villous, almost glabrous when aged, densely villous abaxially, secondary veins pinnate, 6–7 each side. Inflorescence axillary. Pedicels 1.4– 2. 7 cm long, rusty villous. Bracteoles lanceolate, ca. 3 × 2 mm, densely rusty villous adaxially, pubescent at apex abaxially. Perianth zygomorphic. Calyx tube geniculately curved, adaxially pubescent and light yellow at base, light brown towards apex. Basal part of tube 17.6–22.2 × 6.8–7.6 mm, inside basally light yellow, black purple towards apex, densely pubescent, purple red with light yellow dots at upper part, upper part of tube 13.9–19.4 × 7.6–8.5 mm, inside basally purple red with light yellow dots, light yellow with purple red at upper part. Limb saccate, triangular in lateral view, 3.8–4.6 × 1.7–2.4 cm, forming right angle with upper part of the calyx tube, 3-lobed, upper part separated to ca. 1/2–2/3 of limb, lower part shallowly lobed, lobe triangulate, blunt at apex, upper two lobes 2.4–3.3 × 1.5–2.1 cm, lower lobe 0.6–1.2 × 0.6–0.9 cm, inside light yellow, densely prickly outgrowths. Throat ca. 3 mm in diameter. Anthers 6, oblong, ca. 1.5 mm long, adnate to gynostemium in 3 pairs, opposite to lobes. Gynostemium ca. 4.1 mm long, ca. 2.6 mm in diameter, fleshy; lobes 3, obtuse at apex. Ovary inferior, terete, ca. 1.0– 1.5 cm long, 0.2–0.3 cm in diameter at base, densely rusty villous abaxially. Capsule greenish-brown, puberulent and pubescent, 8.5–9.3 cm long, 2.1–2.6 cm in diameter, 6-ridged. Seeds numerous, elliptic, 4.5–5.5 × 4.0–5.0 mm, not winged, the adaxial surface deeply concave, both surfaces glabrous.

Distribution and habitat: — Aristolochia sanheensis is currently known only from its type locality. The vegetation type in which it occurs is a subtropical semi-humid evergreen broadleaf forest with two canopy layers, reaching a height of 20–25 meters. It is accompanied by the dominant species Daphne papyracea Wall. ex G.Don ( Loudon 1830: 156), Tongpeia fungosa (T.P. Yi 1985: 121) Stapleton (2021: 13) , and Ardisia thyrsiflora D. Don (1825: 148) .

Phenology: —Flowering from March to September. Fruiting from May to October.

Etymology: —The specific epithet was derived from the village which is the type locality. The Chinese name is given as 三ñṉ兜ĸ, Chinese pinyin: sān hé mǎ dōu líng.

Conservation status: —The habitat of Aristolochia sanheensis is located near the eastern edge of the Gaoligong Mountain National Reserve of China, which is a collective forest land allocated to farmers for management, covering approximately 200 hectares. Over the past decade, this land has been leased to a local forest farmer and replaced with an area for agroforestry. Approximately one-third of the area has been developed. It is currently known that this population of A. sanheensis clearly exhibits a very narrow distribution, with only approximately 100 individuals of the species identified in this area. In addition, climate change has been particularly pronounced in this region, with alternating extreme weather events such as droughts and heavy rainfall.Although the authors have observed a relatively high number of flowers in 2023, the fruiting proportion is relatively low. This encourages the authors to evaluate it as Critically Endangered (CR), according to the related criteria of IUCN Standards and Petitions Subcommittee (2022).

Additional specimens examined: — CHINA. Yunnan province, Nujiang Lisu Autonomous Prefecture, Lushui city, Luzhang town, Sanhe village , 25.887351ºN, 98.782557ºE, elev. ca. 2200m, 18 September 2023, flowers and fruit, J.-Z. Liu et al. 2023091801 ( SWFC!) GoogleMaps .