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Research Article
Taxonomic studies on the genus Isotrema (Aristolochiaceae) from China III: I. pseudohei, a new species from Yunnan, Southwest China
expand article infoJun Wang‡, Guo-Dong Li§, Juan-Juan Yang‡, Bin Shen|, Chun-Xia Pu§, Xin-Xin Zhu‡
‡ Xinyang Normal University, Xinyang, China
§ Yunnan University of Chinese Medicine, Kunming, China
| Shanghai Zuibaichi Park, Shanghai, China

Corresponding author: Xin-Xin Zhu ( zhuzhu8niuniu@126.com )

Academic editor: Elton John de Lirio
© 2021 Jun Wang, Guo-Dong Li, Juan-Juan Yang, Bin Shen, Chun-Xia Pu, Xin-Xin Zhu.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Wang J, Li G-D, Yang J-J, Shen B, Pu C-X, Zhu X-X (2021) Taxonomic studies on the genus Isotrema (Aristolochiaceae) from China III: I. pseudohei, a new species from Yunnan, Southwest China. PhytoKeys 186: 43-52. https://doi.org/10.3897/phytokeys.186.63543
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Abstract

Isotrema pseudohei, a new species from Yunnan, Southwest China, is described and illustrated. It is morphologically similar to I. hei and I. moupinense, but differs from the former in the colour of flower and throat, the size of throat and the shape of gynostemium lobes, and from the latter in the shape of lamina and gynostemium lobes.

Keywords

Aristolochia, clarification, morphology, taxonomy

Introduction

Isotrema Raf. was previously treated as a subgenus of Aristolochia L. and was recently reinstated as an independent genus base on both molecular data and morphological evidence (Zhu et al. 2019a). It can be distinguished from the genus Aristolochia in the strongly curved perianth with a 3-lobed limb, and especially the 3-lobed gynostemium with a pair of anthers on the outer surface of each gynostemium segment. Comprising 109 species, the genus mainly occurring in East and South Asia, with a few species disjunctly distributed in North and Central America (Zhu et al. 2019a). Currently, 71 species of Isotrema are recorded in China, of which 57 are endemic (Hwang et al. 2003; Lai et al. 2019; Li et al. 2019; Peng et al. 2019; Zhou et al. 2019; Zhu et al. 2019a, 2019b, 2019c, 2019d, 2019e; Cai et al. 2020a, 2020b; Luo et al. 2020; Wang et al. 2020a, 2020b; Liao et al. 2021).

During a field expedition to Yunnan, Southwest China, some unknown specimens of Isotrema were discovered. After careful comparison with previously known species and study of related literature (Hwang 1988; Ma 1989a, 1989b; Tao 1997; Hwang et al. 2003; Do et al. 2015; Do and Nghiem 2017; Yang et al. 2018; Zhu et al. 2019a, 2019d; Cai et al. 2020a, 2020b; Wang et al. 2020a, 2020b), we confirm it as a new species, describe and illustrate it below.

Material and methods

Specimens of Isotrema from 36 herbaria (A, BM, BR, CDBI, CSFI, CSH, E, EMA, GXMI, HAST, HENU, HHBG, HIB, HITBC, IBK, IBSC, K, KUN, L, LBG, LE, NAS, NTUF, P, PE, PEM, QTPMB, SM, SNU, SYS, TAI, W, WCU, WU, WUK, YUKU; acronyms follow Thiers 2021) and our collections in the field all over Asia were examined. Meanwhile, the literature, in particular the protologues of published names, was collated and reviewed. The geographic distribution has been compiled from literatures and complemented by the analyzed specimens and color photos. Photographs of plants were taken in the wild for each species and the terminology of description was mainly based on the Flora of China (Hwang et al. 2003).

Taxonomy

Isotrema pseudohei X.X.Zhu, Jun Wang bis & G.D.Li, sp. nov.

urn:lsid:ipni.org:names:77234089-1
Figures 1, 2, 3, 4A–C

Type

China. Yunnan: Yuxi City, Xinping County, near Atizuo Village, 101°55'51"E, 23°58'46"N, 1823 m a.s.l., 11 September 2018, X. X. Zhu et al. ZXX18249 (holotype: CSH [CSH-0157854!]; isotypes: CSH!, KUN!).

Diagnosis

Similar to Isostrema hei Lei Cai & X.X.Zhu and I. moupinense (Franch.) X.X.Zhu, S. Liao & J.S.Ma, but significantly differs in the following characters: laminas lanceolate to narrowly lanceolate, basal tube of calyx ca. 1.5 cm long, inside dark purple at base and yellowish white above base; upper tube of calyx ca. 2.3 cm long, inside yellowish white, getting yellow in upper portion; inner surface of limb yellow with purplish red patches; throat yellow, suborbicular, 7–9 mm in diameter; apex of gynostemium lobes acute.

Figure 1. 

Line drawing of Isotrema pseudohei X.X.Zhu, Jun Wang bis & G.D.Li A habit B leaf C flower (frontal view) D flower (lateral view) E flower (dorsal view) F dissected flower (showing the inside structure) G anthers and gynostemium H dehiscing capsule I seeds. Illustrated by Shi-Zhen Qiao.

Description

Climbing shrubs. Stems terete, brown pubescent when young, old branchlets glabrous. Petioles 1–2 cm long, appressed villous; laminas lanceolate to narrowly lanceolate, 6.5–17.5 × 2.6–4.5 cm, base round to shallowly cordate, margin entire, apex acute, adaxially sparsely pubescent, abaxially densely villous, especially on veins, lateral veins 4–6-paired. Flower solitary, axillary or on stems; pedicels ca. 3 cm long, densely rusty villous; bractlet 1, lanceolate to elliptic, 3–4 mm long, adaxially subglabrous, abaxially densely rusty villous, inserted on middle part of pedicel. Calyx tube geniculately curved, abaxially yellowish white, densely villous; basal tube ca. 1.5 cm long, inside dark purple at base and yellowish white above base; upper tube ca. 2.3 cm long, inside yellowish white, getting yellow in upper portion; limb discoid, ca. 2.1 cm wide, shallowly 3-lobed, lobes broadly triangular, inner surface yellow with purplish red patches; throat suborbicular, yellow, 7–9 mm in diameter. Anthers 6, oblong, ca. 1.6 mm long, adnate in 3 pairs to base of gynostemium, opposite to lobes. Gynostemium 4–5 mm long, 3-lobed, apex of lobes acute. Ovary terete, ca. 8 mm long, densely brown villous. Capsule cylindric, six arrises, ca. 3 × 2.2 cm. Seeds ovate to elliptic, 3.5–5 × 3–4.5 mm, adaxially deeply concave, abaxially convex, glabrous on both sides.

Figure 2. 

Isotrema pseudohei X.X.Zhu, Jun Wang bis & G.D.Li from the type locality A habit B leaves C flower (frontal view) D anthers and gynostemium E fruit F seeds. Photographed by Xin-Xin Zhu.

Phenology

Flowering and fruiting specimens of the new species were collected in September.

Figure 3. 

Holotype of Isotrema pseudohei X.X.Zhu, Jun Wang bis & G.D.Li. (CSH-0157854).

Etymology

The specific epithet refers to the similarity between the new species and Isotrema hei in the morphology of lamina and flower. The Chinese name is given as “拟何氏关木通”.

Figure 4. 

Morphological comparisons of the leaves and flowers of Isotrema pseudohei (A–C), I. hei (D–F) and I. moupinense (G–I). Photographed by Xin-Xin Zhu.

Distribution and habitat

Isotrema pseudohei is distributed in Xinping County of Yunnan Province, China. It grows on the roadside or in mixed forests on sunny slopes at an elevation between 1820 m and 2045 m, together with other taxa as Castanopsis sp. (Fagaceae), Commelina undulata R. Br. (Commelinaceae), Disporum sp. (Colchicaceae), Lycianthes macrodon (Wall.) Bitter (Solanaceae), Rubus sp. (Rosaceae), etc.

Preliminary conservation status

Isotrema pseudohei is currently only known from two populations in Xinping County, with fewer than five individuals at each site. Based on the present study, its Extent of Occurrence (EOO) is less than 100 km2 and the known Area of Occupancy (AOO) is less than 20 km2. Furthermore, the habitat is being destroyed by road construction and small-scale agriculture. Besides, the root of Isotrema itself is often harvested for medicinal purposes by the locals. Although further investigation is necessary to fully map its distribution, it is considered to be Vulnerable (VU) status, based on the criteria D2 of IUCN according to the IUCN Red List Categories and Criteria (IUCN Standards and Petitions Committee 2019).

Additional specimens of Isotrema pseudohei examined (paratypes)

China. Yunnan: Yuxi City, Xinping County, 2045 m a.s.l., 11 September 2018, X. X. Zhu et al. ZXX18250 (CSH, KUN).

Specimens of Isotrema hei examined

China. Yunnan: Wenshan City, 12 May 2018, X. X. Zhu ZXX18072 (CSH), 20 April 2018, Lei Cai et al. CL115 (KUN).

Specimens of Isotrema moupinense examined

China. Chongqing: Nanchuan District, 27 May 1957, T. H. Hsiung & Z. L. Chou 91052 (IBSC), 11 July 1957, S. Y. Chen et al. 95126 (NAS), 12 July 1957, T. H. Hsiung & Z. L. Chou 91972 (IBSC), 25 July 1957, T. H. Hsiung & Z. L. Chou 92285 (IBSC), 17 May 2007, Z. B. Feng et al. 20070508 (PE, WCSBG); Sichuan: Baoxing County, 4 August 1936, K. L. Qu 3410 (IBSC), 1954, T. P. Soong, 38982 (IBSC, NAS), 20 May 1958, Sichuan Agricultural College 4867 (IBSC); Dayi County, 26 May 2015, X. X. Zhu & Z. X. Hua ZH082 (CSH), 26 May 2015, X. X. Zhu & Z. X. Hua ZH083 (CSH); Emeishan City, 1952, C. H. Hsiung et al. 30475 (IBK, IBSC, NAS), 24 May 1952, C. H. Hsiung et al. 30750 (IBSC), 6 June 1960, Sichuan Med. Pl. Exped. 12729 (NAS), 29 April 2015, X. X. Zhu & Z. X. Hua ZH046 (CSH); Jinyang County, 29 April 2013, C. Du & Y. Wang DC-325 (CSH); Luding County, 14 July 2006, X. M. Gao G06117 (WCSBG); Yingjing County, 20 May 1940, K. L. Chu 6901 (NAS); Yunnan:Gongshan County, 25 May 2011, J. Cai et al. 11CS2767 (KUN); Yunlong County, 24 April 2019, X. X. Zhu et al. ZXX19356 (KUN).

Discussion

Characterized by a horseshoe-shaped perianth and a 3-lobed gynostemium with each lobe consisting of two oblong stamens, the new species is shown to be a member of Isotrema (Zhu et al. 2019a). Isotrema pseudohei is similar to I. hei in the shape of lamina (Fig. 4A & D), but differs in the morphology of flowers, the inner surface of limb is yellow with purplish red patches and throat suborbicular, yellow, and 7–9 mm in diameter in I. pseudohei (Figure 4C), whereas the inner surface of limb yellowish green and densely covered with purple papillae and throat circular, yellowish green with purple patches, and 4–5 mm in diameter in I. hei (Figure 4F). Though sharing similar morphology of flowers (Fig. 4B, C, H, J), I. pseudohei can be easily distinguished from I. moupinense by the shape of lamina, which is lanceolate in the new species (Figure 4A), but ovate in I. moupinense (Figure 4G). Moreover, I. pseudohei also differs in the gynostemium lobes acute at apex (Figures 2D & 4C), whereas round at apex in I. hei (Figure 4F) and I. moupinense (Figure 4I). Detailed morphological comparisons are provided in Table 1 and shown in Figure 4. Geographically, the new species is currently only known from Xinping County in central Yunnan, I. hei is restricted to Wenshan City in Southeast Yunnan, while I. moupinense is widely distributed in Southwest China (Figure 5).

Figure 5. 

Distribution of Isotrema pseudohei, I. hei and I. moupinense based on field observation, specimens, color photos and literatures examined.

Table 1.
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Morphological comparisons of Isotrema pseudohei, I. hei and I. moupinense.

Character I. pseudohei I. hei I. moupinense
Lamina lanceolate to narrowly lanceolate, 6.5–17.5 × 2.6–4.5 cm lanceolate to narrowly lanceolate or narrowly elliptic, 2.5–12.5 × 1–4.5 cm ovate, 6–16 × 5–12 cm
Basal tube of calyx inside dark purple at base and yellowish white above base inside dark purple at base and yellowish white with dark purple stripes and patches above base inside dark purple at base and yellowish with purple stripes and patches above base
Upper tube of calyx inside yellowish white, getting yellow in upper portion inside yellowish white with reddish purple patches inside yellowish white, getting yellow in upper portion
Limb ca. 2.1 cm wide; inner surface yellow with purplish red patches ca. 2.4 cm wide; inner surface yellowish green and densely covered with purple papillae 2–2.5 cm wide; inner surface yellow to dark red, sometimes with red or yellow spots
Throat suborbicular, yellow, 7–9 mm in diameter circular, yellowish green with purple patches, 4–5 mm in diameter circular, yellow, 8–11 mm in diameter
Gynostemium apex of lobes acute apex of lobes round apex of lobes usually bilobate, rarely obtuse

Acknowledgements

The authors would like to thank Ms. Shi-Zhen Qiao for the line drawing of the new species. This study was supported by the Special Subsidies for Public Health Services of “Fourth Chinese Materia Medica Resources Survey” (DSS, MOF.43/2018) and the Institute for Conservation and Utilization of Agro-bioresources in the Dabie Mountains.

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