Thottea aroangensis T.A. Le, D. Dien & Tagane, 2021

Le, Tuan Anh, Dinh, Dien, Doan, Quoc Tuan, Nguyen, Quang Hoa Anh & Tagane, Shuichiro, 2021, Thottea aroangensis, a new species of Aristolochiaceae from central Vietnam, Phytotaxa 513 (1), pp. 69-74 : 70-73

Thottea aroangensis T.A. Le, D. Dien & Tagane , sp. nov. ( Figs 2 & 3 )

TYPE: — VIETNAM. Thua Thien Hue province : A Luoi district , A Roang commune, 16°07′39.17″N, 107°24′39.59″E, ± 850 m a.s.l., 18 April 2021, Dien Dinh , Quoc Tuan Doan , Quang Hoa Anh Nguyen, Tuan Anh Le LTA 1101 (holotype VNMN!) .

Thottea aroangensis is characterized by subshrub habit 70–90 cm tall, inflorescence at base of stem close to ground level, campanulate perianth ca. 2.6 cm long, inside of perianth tube with creamy white patches, obscure perianth lobes very broadly triangular ca. 0.5 cm long, and 20 stamens in 2 whorls, which the combination of characters clearly distinguished it from all the previously known species of the genus.

Perennial subshrubs, 70–90 cm tall. Stems erect, scarcely branched, dark green, 0.4–1 cm in diam., terete, glabrous; internode 2.5–15 cm long, node swollen, above nodes constricted. Leaves alternate, distichous; blade elliptic-oblong to obovate, 13–16 × 4–5 cm, slightly curved, laterally not equal, apex acute or mucronate, base obtuse to rounded, slightly oblique, margins entire, adaxial surface green, glabrous, abaxial surface pale green, sparsely pubescent along midrib and veins, midrib prominent on both surfaces, lateral veins 5–6 pairs, prominent on abaxial surface; petioles 0.8–1 cm long, glabrous. Inflorescences 1–2 per plant, racemose, at base of stem close to ground level, axils of fallen leaves, up to 8-flowered; peduncle not branched, 6–11 mm long, 2–3 mm in diam., bracts ovate, elliptic-lanceolate, lanceolate or obovate, 5 × 2–4 mm, venation obvious when young, dark purple, pubescent, margin entire, apex acute, sometimes bifid. Pedicel and ovary 0.5–1.2 cm long, densely pubescent, 4-ribbed. Perianth campanulate, ca. 2.6 cm long, 2.2 cm in diam., base sub-truncate, obscurely lobed, tube ca. 2.1 cm long, outer surface dark claret, sparsely pubescent, with prominent longitudinal veins, inner surface claret with creamy white patches in upper half, densely villous, margin shallowly 3-lobed, lobes very broadly triangular, 0.5 × 0.4–1.8 cm, apex blunt. Stamens 20 in alternate whorls of 2, upper whorl with 10 stamens, lower whorl with 10, filaments 1–1.5 mm long, glabrous, anthers extrose, positioned at swollen connective apex, oblong, ca. 1 mm long, ca. 0.5 mm wide. Style column cylindric, ca. 1.5 mm long, glabrous, stigmatic lobes 8–9, positioned higher than stamens, ca. 4 mm long, glabrous. Capsules ca. 3 cm long, ca. 3.5 mm in diam., dark green to dark purple, curved, 4-angled, puberulent. Seeds not seen.

Distribution:— Vietnam, known only from the type locality ( Fig. 1 ).

Habitat:— Thottea aroangensis was found on alluvial soils of the shady reclined slope in primary broad-leaved evergreen forest at elevation around 850 m a.s.l., where it grows with Aspidistra heterocarpa Aver., Tillich & V.T. Pham var. echinata Aver., Tillich & T.A. Le , Curculigo sp. , Dracaena angustifolia Roxb. , and Gomphia serrata (Gaertn.) Kanis.

Phenology:— Flowering in March to April and fruiting in April to May.

Etymology:— The specific epithet is derived from its type locality, A Roang commune, located in A Luoi district, Thua Thien Hue province, central Vietnam.

Vernacular name:— Tốt hoa a roàng

Preliminary conservation assessment:— Critically Endangered (CR). To date, we found only five individuals in one population of Thottea aroangensis in the type locality. Therefore, the most appropriate initial assessment of the IUCN conservation status for this species is Critically Endangered (CR) under criteria D ( IUCN, 2012). The habitat is located within the protected area at district level and well-protected. However, since it grows near the route for tourist, we need to pay special attention for its survival.

Note:— In Indochina, three species of Thottea , T. racemosa , T. tomentosa , and T. aff. hainanensis were recorded ( Hou 1981, Hô 1999, Phan et al. 2009, Tagane et al. 2017). Thottea aroangensis is easily distinguished from T. racemosa and T. aff. hainanensis by its inflorescence at base of stem close to ground level (vs. at the upper part of stem, in the axils of foliage leaves) and from T. tomentosa by taller habit 70–90 cm tall (vs. 10–50 cm tall), abaxial surface of lamina sparsely pubescent along midrib and veins (vs. tomentose), and longer perianth ca. 2.6 cm long (vs. 0.7–1.2 cm long). Thottea aroangensis is similar to T. becarrii Hou (1981: 315) of Sumatra in having inflorescence at base of stems and obscurely lobed perianth, but differs in having smaller lamina (13–16 × 4–5 cm in T. aroangensis vs. 19.5–25 × 9.5–15 cm in T. beccarrii ), shorter pedicle and ovary (5–12 mm long vs. 15–17.5 mm long), larger campanulate perianth ca. 2.6 cm long (vs. perianth cupular, 1.2–1.5 cm long).

Figures

FIGURE 1. Locality of A Roang commune, A Luoi district, Thua Thien Hue province (closed square), representing the distribution of Thottea aroangensis T.A. Le & D. Dien & Tagane.

FIGURE 2. Holotype of Thottea aroangensis T.A. Le, D. Dien & Tagane (Dien et al. LTA 1101, VNMN).

FIGURE 3. Thottea aroangensis T.A. Le, D. Dien & Tagane. A. Habit; B. Leaves (abaxial surface); C. Inflorescence with flowers and immature fruits; D. Flowers (lateral view); E. Flower (front view); F. Flower corolla removed, showing stamens and pistil; G. Corolla dissected showing the coloration of inner surface.