Isotrema pseudohei X.X.Zhu, Jun Wang bis & G.D.Li, 2021

Wang, Jun, Li, Guo-Dong, Yang, Juan-Juan, Shen, Bin, Pu, Chun-Xia & Zhu, Xin-Xin, 2021, Taxonomic studies on the genus Isotrema (Aristolochiaceae) from China III: I. pseudohei, a new species from Yunnan, Southwest China, PhytoKeys 186, pp. 43-52 : 43

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

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.

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.

Phenology.

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

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”.

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).

Figures

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.

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.

Figure 3. Holotype of Isotrema pseudohei X. X. Zhu, Jun Wang bis & G. D. Li. (CSH- 0157854).

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.