Aristolochia pulvinata Yi-Fan Wang & Zhi-Jian Yin, 2024

Zhang, Hong-Lin, Wang, Yi-Fan, Guo, Zi-Rui, Zhu, Tong, Yang, Hu-Hua & Yin, Zhi-Jian, 2024, Aristolochia pulvinata, a new species of Aristolochiaceae from Yunnan, Southwest China, Phytotaxa 675 (3), pp. 261-272 : 263-269

Aristolochia pulvinata Yi-Fan Wang & Zhi-Jian Yin , sp. nov.

Figures 1–2

Type:— CHINA. Yunnan province, Dali Bai autonomous prefecture, Yongping county, Shanyang town , Jinguangsi nature reserve , 25°11´N, 99°32´E, 2446 m, 10 April 2024, flowering, H. L. Zhang & T. Zhu JGS654 (holotype KUN1601585!; isotypes KUN1601586!, KUN1601587!) .

Diagnosis:— Aristolochia pulvinata is distinguished by a prominent elliptical, elevated thickened region on the adaxial side of the calyx limb, encircling the throat, with the three dentate lobes connate, forming a triangular perianth opening. The limb’s interior surface is densely covered with dark purple granular pustules. Morphologically, it is most similar to the sympatrically distributed Aristolochia ovatifolia , but can be readily distinguished by the absence of such an elevated thickening on A. ovatifolia 's calyx limb, which instead features a smooth, velvet-textured interior surface. In leaf morphology, A. ovatifolia has ovate, thick, felted leaves with long, rusty villi on both sides, whereas A. pulvinata presents cordate leaves with an acuminate apex, sparsely covered with short indumentum.

Description:—Climbing shrub, 0.5–1.8 m Roots cylindrical, young roots capable of forming creeping roots; older roots lignified, diameter 0.8–3.0 cm, cross-section circular to elliptical, xylem yellow, with xylem rays grouped into three equal clusters. Stems cylindrical; young branches densely covered with rusty short indumentum, older branches glabrous to scabrous; transition from green, herbaceous young branches to older branches with a coarse, barleylike texture on the surface; fully lignified stems develop a surface forming rough, warty bark. Petioles 3.0-6.0 cm long; juvenile leaves densely rusty villous; mature leaves adaxially sparsely tomentose to appressed, abaxially slightly pubescent, showing palmate venation, with two pairs of veins symmetrically extending laterally from the base of the central midrib; leaf blades lanceolate, bases cordate, margins entire, 6.0-15.0 × 3.0-8.0 cm, papery; sinuses deep, 0.5- 1.5 cm; apices acute. Flowers often solitary or in pairs, axillary on young branches, and cauliflorous on lignified stems, typically emerging from nodular structures formed by meristematic tissue in the axils of previously fallen leaves. On lignified stems, fascicles commonly bear 2–4 flowers on average.; pedicels 1.0-2.0 cm long, usually pendant, densely covered with rusty short indumentum. Perianth abaxially scabrous with a short yellow to brown indumentum; bracteoles reduced or very small, triangular, attached at the base of the pedicel, both surfaces densely covered with rusty woolly villous, sessile. Calyx fused into a geniculated, tuberous perianth, zygomorphic; utricle extending from the calyx-pedicel junction downward about 0.8-1.0 cm; calyx tube geniculately curved; utricle from the pedicel-joint downward 0.6-1.2 cm, cylindric, abaxially green-yellowish with sparse pubescence, adaxially dark purplish, arachnoid villous; from utricle to geniculation 1.0- 1.4 cm, abaxially yellowish to purplish, sparsely tomentose; adaxially purplish, glabrous, with a velvety texture, ridged with veins; from geniculation to the calyx throat, 1.2-1.8 cm, abaxially purplish, sparsely tomentose; abaxially purple to reddish, glabrous, velvety, smooth, gourd-shaped tube; near the throat region darkening to black purple for 0.2-0.3 cm. Calyx limb trilobate, semi-open saccate, 0.9-1.5 cm long, 1.0- 1.2 cm in diameter, abaxially purplish red to yellowish green; adaxially densely covered with dark purple granular pustules. Upon floral anthesis, downward lobe reflexes, curling back to create a triangular aperture at the calyx limb's opening., throat ca. 0.1–0.2 cm in diameter, from throat opening to the margin of the inferior lobe, quickly elevating and thickening, forming a pulvinate structure from 0.1-0.2 cm above the throat extending downward to the lower lobe edge, the entire thickening region oval, thickest in the middle, edges thin, thickness up to 0.3-0.5 cm, edges sparsely covered with some purple pustules, central part of pulvinate smooth, waxy, occasionally with brown dots, obliquely outward at approximately 70 degrees relative to the horizontal, function pending further investigation. Stamens 6, in one series, fully adnate with the style column to form a gynostemium, in three pairs opposite stigma lobes; filaments absent; anthers oblong, approximately 0.1-0.2 cm long, extrorse. Gynostemium approximately 0.3 cm long, diameter 0.18-0.25 cm, fleshy; lobes 3, apex obtuse; margin crisped; ovary inferior, cylindrical, 0.5-0.7 cm long, diameter 0.2- 0.4 cm, with 6 ridges, densely rusty villous abaxially. Capsule and seeds not observed.

Distribution and habitat:— Aristolochia pulvinata is currently documented solely at its type location, thriving in moist, shaded habitats along montane stream banks. The microhabitat is primarily characterized by a dark brown humic layer, occasionally found amid streamside debris. The forest, achieving a canopy closure of 70–80%, predominantly consists of Castanopsis orthacantha Franchet (1899: 194) ( Fagaceae ) and Camellia reticulata Lindley (1827: 1078) ( Theaceae ), among other species. The understory is prevalently occupied by Sarcococca wallichii Stapf (1916: 37) ( Buxaceae ) and Sarcococca hookeriana var. digyna Franchet (1889: 135) ( Buxaceae ). The estimated population of this species is currently around 100 individuals, distributed from an altitude of 2435 m to 2656 m above sea level.

Phenology:—Flowering from March to May. Fruit or seed not observed.

Etymology:—The specific epithet "pulvinata " is derived from the distinctive pulvinate thickening on the inferior lobe of the adaxial side of the calyx limb observed in its flowers. The subgenus Siphisia is commonly referred to as ẍ †® (guan mu tong) in Chinese, which differs from the genus name Aristolochia , typically known as ṉ兜ẅ (ma dou ling). Therefore, the Chinese name is given as 垫ẖẑẍ†® (dian zhuang hua guan mu tong), reflecting this unique morphological trait.

Additional specimen examined (paratype):— CHINA. Yunnan province, Dali Bai autonomous prefecture, Yongping county, Shanyang town, Jinguangsi nature reserve, 25°11´N, 99°32´E, 2228 m, 08 May 2024, flowering, H. L. Zhang & T. Zhu JGS1116 (SWI25!).

Similar species and phylogenetic position:— Aristolochia pulvinata displays close floral morphological similarities with its sympatric species, A. ovatifolia and A. utriformis , especially in the dark purple, glabrous, and velvety texture of the adaxial calyx tube. Additionally, these species exhibit an anachroid villous adaxial surface of the calyx utricle, a feature consistent across the taxa. Together with A. luudamcui and A. melanocephala , these species demonstrate varying degrees of thickening at the calyx throat, as depicted in Figure 3 A2, B2, C2, D2, E2 and detailed in Table 1. However, the characters of the thickening—specifically its shape, texture, angle, and degree—in A. pulvinata are distinctly different from those observed in the aforementioned species.

FIGURE 3. Morphological comparison. A1–A5: Aristolochia pulvinata , B1–B5: A. ovatifolia , C1–C5: A. melanocephala , D1–D5: A. utriformis , E1–E5: A. neolongifolia . A1, B1, C1, D1, E1: Lateral view of the flower; A2, B2, C2, D2, E2: Longitudinal section view of the flower; A3, B3, C3, D3, E3: Front view of the flower; A4, B4, C4, D4, E4 :: Gynostemium; A5, B5, C5, D5, E5: Abaxial (upper right) and adaxial (lower left) sides of the leaf. C1–C5 were provided by Dr. Xinxin Zhu.

Furthermore, the morphology of the saccate structure formed by the calyx limb varies significantly among these taxa. Aristolochia pulvinata is distinctly characterized by a semi-open, bucket-like shape due to its relatively wide, triangular opening, with the interior densely lined with purple, granular pustules. In contrast, A. ovatifolia and A. utriformis exhibit a narrow, elongated conical structure with a constricted opening; A. ovatifolia lacks any bumps on the internal surface of the limb, while A. utriformis features sparse papillae. A. melanocephala is easily recognizable by its elongated tubular calyx limb adorned adaxially with densely packed, black-tipped palliae.

This study also included comparisons with A. luudamcui ( Phan et al. 2021) and A. neolongifolia , both of which can be readily differentiated from A. pulvinata by their yellow-colored adaxial perianth calyx tube and limb. Detailed morphological comparisons and additional information are provided in Figure 3 and Table 1.

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* Measured by this study

** Following original description of A. melanocephala ( Zhu et al. 2018)

*** Following original description of A. luudamcui ( Phan et al. 2021)

**** U–G–T = utricle to geniculation to throat

Conservation status:— Aristolochia pulvinata is currently known only from its type locality and, like many members of Aristolochia subg. Siphisia , exhibits high endemism, being restricted to a narrow habitat ( Luo et al. 2020; Huang et al. 2022). With an estimated population size of only about 100 individuals, this species is potentially vulnerable. The genus Aristolochia is known for its critical role as host plants for multiple swallowtail butterfly species ( Lepidoptera : Papilionidae ). Particularly, the sympatric species A. ovatifolia has been confirmed as a local host for Bhutanitis lidderdalii ( Zhang et al. 2019) , a critically endangered butterfly listed under CITES Appendix II (2024). This relationship underscores the potential ecological importance of Aristolochia pulvinata , suggesting its possible role in butterfly conservation and highlighting the need for comprehensive conservation assessments.

During our fieldwork in Yunnan province, it was observed that multiple Aristolochia species are indiscriminately exploited for use in traditional Chinese medicine (TCM), largely due to their morphological similarities when not in flower. Specifically, Aristolochia pulvinata has only been found in a very limited and concentrated area (<10km 2), with no observed fruiting or seed production this year. This could indicate it potentially facing a pollination challenge, necessitating further ecological and reproductive studies.

Given these findings, it is recommended to classify Aristolochia pulvinata as Critically Endangered (CR) under the IUCN Red List criteria B2ab; C2a (i, ii). This assessment is based on its extremely restricted distribution to a single location, the isolated and high endemic nature of its population, the absence of fruiting, the exploitation risks from local traditional medicine practices, and its ecological significance. This recommendation aligns with the guidelines provided by the IUCN Standards and Petitions Committee (2024).

Figures

FIGURE 1. Aristolochia pulvinata Yi-Fan Wang & Zhi-Jian Yin. sp. nov. A. Habitat, B. Habit in situ, C. Frontal abaxial view of the bud, D. A pair of flowers in a fascicle on lignified stem, E. Front view of the flower, F–G. Longitudinal section of the flower, showing the adaxial side of the calyx limb covered with purple pustules, H. Thickened pulvinate structure on the calyx limb, I. Lateral and back view of the flower, J–K. Top and lateral view of the gynostemium, showing the paired anthers and their position, L.Adaxial (upper) and abaxial (down) side of the leaf, M–N. Taproot and root tips.

FIGURE 2. Line drawing of Aristolochia pulvinata by Ms. Xiao Li. A. Habit, showing alternate leaves and axillary inflorescences, B. Abaxial view of the leaf, showing palmate venation, C. Cauliflorous habit on lignified branches, D–E. Longitudinal section and frontal view of the flower. F. Thickened pulvinate structure on the calyx limb, G–H. Gynostemium and pedicel, I–J. Lateral and transverse sections of the root, showing three xylem ray clusters.