Aristolochia zhuhaiensis Y. Fan Wang & Z. R. Guo, 2025

Aristolochia zhuhaiensis Y. Fan Wang & Z. R. Guo sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3

Type.

China. • Guangdong Province: Zhuhai City, Doumen District , under forest in coastal hills, elevation 90 m, 16 Feb 2024, Y. Fan Wang & Z. R. Guo yw 00036 (holotype: IBSC 1041409 About IBSC !; isotypes: IBSC 1041410 About IBSC !, IBSC 1041411 About IBSC !) .

Diagnosis.

Aristolochia zhuhaiensis shares morphological similarities with A. thwaitesii , both of which are distributed in neighboring regions and represent the only two known self-supporting, non-twining Aristolochia subg. Siphisia species in Asia. In terms of vegetative characteristics, these two congeners are highly similar; however, they can be readily distinguished by their markedly different floral morphologies. Aristolochia zhuhaiensis is characterized by a campaniform-infundibuliform calyx limb densely covered with porcelain-white granular pustules. It also features a conspicuous platform-shaped area beneath the perianth throat, which is white, glabrous, waxy, and slightly elevated upward. In contrast, A. thwaitesii possesses an elongated, concave tubular calyx limb with an adaxial surface that transitions from purple to pale yellow or white towards the apex. This species is entirely covered with recurved fleshy prickles and lacks the distinctive platform structure found in the calyx of A. zhuhaiensis . Detailed morphological comparisons between the new species and A. thwaitesii are shown in Figs 4 View Figure 4 , 5 View Figure 5 and Table 1 View Table 1 .

Description.

Erect subshrub. Roots fusiform or globose. Stems terete, densely rusty villous, becoming glabrous when lignified. Leaf blades spathulate, narrowly oblanceolate, or lanceolate, with an apex acute to acuminate, 12–16 × 3–3.5 cm. Almost glabrous to subglabrous adaxially, densely brown-villous abaxially. Venation pinnate, with 10–12 secondary veins on each side, leaves papery; petiole approximately 0.6–1.0 cm long, densely rusty villous. Basal inflorescence, fasciculate; flower count varies significantly depending on plant nutrient status, ranging from solitary to up to 20. Pedicels approximately 1–1.2 cm long, initially erect, then pendulous, densely rusty villous. Bracteole 1, lanceolate, 1–2 × 0.4–0.5 mm, densely rusty villous on both sides, sessile. Perianth zygomorphic, densely covered with grey indumentum abaxially, campanulate, 0.9–1.2 × 0.8–1.0 cm; dark purplish, arachnoid white villous. Calyx tube geniculately curved, yellowish to brownish abaxially; utricle to geniculation: 2.5–3.5 cm, light purplish with dark veins, subglabrous adaxially; geniculation to throat: 2.5–3.0 cm, dark purple, glabrous, velvety adaxially. Calyx limb 3.0–4.0 cm long, 4.5–5.5 cm in diameter, flaring to campaniform-infundibuliform, densely covered with porcelain-white granular pustules; beneath the throat forms a glabrous and flat area that lies on the soil, waxy; abaxial side of calyx limb brownish to yellowish, villous with ridged veins. Apex of the calyx limb 3 - dentate; when the flower is near withering, the calyx apex rolls outward. Throat approximately 6–9 mm in diameter, purple, cordate-shaped. Stamens 6 in one series, fully adnate in 3 pairs to the style column to form a gynostemium, opposite the stigma lobes; anthers oblong, approximately 2.0–3.0 mm long, extrorse. Gynostemium approximately 4.5–5 mm long, 4–5 mm in diameter, fleshy; lobes 3, hooked inward at the apex; margin crenate-rugose. Ovary inferior, cylindric, 6–8 mm long, 3–4 mm in diameter, densely rusty villous abaxially.

Distribution and habitat.

The new species has been discovered exclusively in Zhuhai City, Guangdong Province, China (Fig. 6 View Figure 6 ). It is typically found near creeks within forests on coastal hill slopes, at elevations ranging from 50 to 100 meters. To date, three populations have been identified, all situated in the southern region of Zhuhai City: two within Doumen District and one in Jinwan District, each in proximity to the coastal areas. This species commonly occurs near water sources such as creeks and mountain streams, usually thriving under dense canopy cover. Associated species typically include Nepenthes mirabilis (Lour.) Druce , Drosera spatulata Labill. , Strophanthus divaricatus (Lour.) Hook. & Arn. , Pteris vittata L. , and Rhodomyrtus tomentosa (Aiton) Hassk.

Phenology.

Flowering from January to early March, fruit or seed not seen.

Etymology.

The epithet ‘ zhuhaiensis ’ refers to the type locality (Zhuhai City), where the new species has been discovered. Given Zhuhai’s status as a highly populated and urbanized city, the discovery of a new species is both a rare and welcome occurrence.

Vernacular name.

During our initial encounter with this new species, local cultivators referred to it by the Cantonese vernacular name “ shí qín qú ” (石蠄蟝), indicating that the root, harvested for medicinal purposes, has a surface texture so coarse it resembles a toad’s skin. Interestingly, as our survey extended further, we discovered that the Hakka people refer to the species as “ shù zǎi lián ” (树仔莲), which translates literally to “ shrubby herb medicine. ” These two distinct ethnic groups each have their own vernacular name for the same species. For clarity and consistency in scientific communication with the broader public, we propose the Chinese name “ zhū hǎi guān mù tōng ” (珠海关木通), reflecting the literal meaning of its epithet and its geographical origin.

Conservation status.

Since we first discovered and recognized it as a new species, we have conducted more than five extensive field trips covering the coastal mountain hills, including all major coastal cities within the Greater Bay Area, particularly focusing on Zhuhai, and its neighboring cities Jiangmen and Shenzhen. Despite these efforts, we only located three extant populations, all of which are confined to Zhuhai. As previously mentioned, this species has long been recognized by local medicinal practitioners and has been exploited for generations to treat snake bites, according to local testimony. The traditional belief in its medicinal properties has made this species highly sought after, leading to its scarcity in the wild in recent years.

Our investigation revealed that A. zhuhaiensis is morphologically challenging to distinguish from its close congener, A. thwaitesii , when not in flower. Local collectors report sometimes to travel to outlying islands near Hong Kong or the Pearl River Estuary to harvest this plant. We hypothesize that in these cases, it remains unclear whether the collected individuals are A. zhuhaiensis or A. thwaitesii , especially as both species primarily exhibit vegetative growth for much of the year, and the collectors focus mainly on harvesting the tuberous roots based on our field survey.

Aristolochia zhuhaiensis faces several severe threats. While A. thwaitesii is already classified as Vulnerable (VU) according to the China Plant Specialist Group (2019), the conservation status of A. zhuhaiensis appears to be even more precarious. The three populations we identified are situated on very small hills in close proximity to urban areas. These hills have limited area and gentle slopes and are completely encircled by urban developments, including residential communities, real estate projects, tourist attractions, airport, and farmlands, as well as other anthropogenic landscapes. Furthermore, these habitats have been heavily invaded by artificial fast-growing Eucalyptus plantations. Our field observations indicate that A. zhuhaiensis exclusively grows under native coastal low shrubland along riparian zones and does not thrive in secondary forests or plantation environments. Habitat loss due to its proximity to human activity is likely one of the primary threats to its survival.

During our multiple fieldwork expeditions in the region, we observed a substantial number of flowers produced by robust individuals, with some bearing up to 20 flowers in a single fascicle at the basal stem. However, we found no evidence of fruiting or seed production. The basal flowering habit might indicate specific pollinator requirements, a topic that warrants further ecological study.

Another aspect of the potential ecological significance of A. zhuhaiensis is its possible role as a host plant for the Chinese windmill butterfly Byasa alcinous Klug , which is also associated with A. thwaitesii . This host relationship with A. thwaitesii has been confirmed by the Agriculture, Fisheries and Conservation Department ( AFCD) of the Hong Kong SAR ( Anon 2010). Considering the morphological similarities between A. zhuhaiensis and A. thwaitesii , as well as the natural range of B. alcinous extending into Zhuhai ( Wu and Bai 2001), A. zhuhaiensis could also provide a vital food source for the butterfly. Further ecological studies are needed to confirm this potential interaction.

Currently, the three known populations of A. zhuhaiensis are located in the coastal region of Zhuhai City, each in close proximity and restricted to an area of less than 10 km 2, at elevations ranging from 50 to 100 meters. Based on these populations, the estimated extent of occurrence (EOO) is 0.335 km 2 (<100 km 2), and the area of occupancy (AOO) is 12.000 km 2. No fruiting or seed production has been observed over the past two consecutive years, and each population comprises fewer than ten individuals. Based on these findings, we recommend classifying A. zhuhaiensis as Critically Endangered (CR) under the IUCN Red List criteria B 1 ab (i, ii, iii, iv, v); D 1. This recommendation reflects its extremely limited distribution, ecological significance, close association with urban areas, vulnerability to habitat loss and medicinal exploitation, and the absence of observed sexual reproduction.

Additional specimen of Aristolochia zhuhaiensis examined.

China. • Guangdong Province: Zhuhai City, Doumen District , under forest in coastal hills, elevation 68 m, 2 Mar 2024, Y. Fan Wang & Z. R. Guo yw 00077 (paratype: IBSC 1041412 About IBSC !) .

Specimens of Aristolochia thwaitesii examined.

China. • Hongkong: Wong Nai Chung Gap , 1903, W. J. Tutcher 979 ( IBSC 0127925 About IBSC ), 4 Jul 2000, Y. W. Lam 1633 (HK 38320); Lantau Island, 16 Mar 1909, W. J. Tutcher 8273 ( IBSC 0127926 About IBSC & HK 23774). UK. Cultivated at Kew, Royal Botanic Gardens, s. coll. s. n., April 1858 ( K 003691508 ); • Tze Kong Bridge , Repulse Bay , Southern District , Hong Kong Island, 1 April 2024 Y. Fan Wang yw 00068 ( IBSC!); Tze Kong Bridge, Repulse Bay, Southern District, Hong Kong Island, 2 April 2024 Y. Fan Wang yw 00069 ( IBSC!).

Notes.

Aristolochia thwaitesii has been confirmed, by our fieldwork, to occur in the Hong Kong region, specifically on Hong Kong Island and Lantau Island (Fig. 6 View Figure 6 ). Although there are records indicating its discovery in Jiangmen and Zhuhai (Ma 1989; Huang et al. 2003), no living plant collection, or photograph of the flower has provided conclusive evidence of its presence there. The only two voucher specimens ( IBSC 0127924 & SYS 00159983 ), collected in 1973 and 1979, almost 50 years ago, are solely vegetative specimens, lacking flowers. Following the confirmation of A. zhuhaiensis , we re-examined these two voucher specimens and embarked on a field expedition in early July 2024 to Dawanshan Island, where voucher IBSC 0127924 was originally collected. Despite extensive efforts, we failed to locate any Aristolochia individuals. Administratively, Wanshan Island is under Zhuhai’s jurisdiction, but geographically it lies closer to the known distribution of A. thwaitesii in Hong Kong than to the range of A. zhuhaiensis that we have documented. As for voucher SYS 00159983 , despite multiple extensive field surveys in Jiangmen City, no specimens have been found. Given the current lack of definitive evidence, such as a living specimen or a photograph confirming the floral morphology, we have refrained from assigning either voucher to A. thwaitesii or A. zhuhaiensis until further conclusive data can clarify their identity.

Given the proximity of this species to urban areas and the lack of any form of protection or monitoring in its natural habitats, combined with its long history of medicinal exploitation, we have opted not to disclose the precise locations of these populations in this paper to safeguard their conservation. We strongly urge local authorities to implement policies or legislation to protect this rare species. Researchers requiring material or information for scientific purposes may contact the authors directly for collaboration and information sharing.