[Botany • 2019] Isotrema cangshanense (Aristolochiaceae) • A New Species from Yunnan [Taxonomic Studies on the Genus Isotrema from China: I]

Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma

in Zhu, Zheng, Wang, et al., 2019. 

苍山关木通  ||  DOI: 10.3897/phytokeys.134.37243 

Abstract

Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma, a new species from western Yunnan, China, is described and illustrated here. It is similar to I. utriforme, I. forrestianum, I. cucurbitoides and I. obliquum The major differences between them are outlined and discussed. A detailed description, along with line drawings, photographs, habitat and distribution, as well as a comparison to morphologically similar species, is also provided. Meanwhile, the new taxon is assessed as Vulnerable (VU D2), according to the IUCN Red List criteria.

Keywords: Aristolochia, Isotrema, morphology, subgenus Siphisia, taxonomy

 Figure 2. Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma, sp. nov. 
A habit B leaves C flower bud D inflorescence E flower (front view) F flowers (lateral view) G anthers and gynostemium H the dehiscent capsule I seeds. Photographed by Xinxin Zhu.

Figure 1. Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma, sp. nov. 
A habit B flower (lateral view) C flower (front view) D opened flower (showing the inner structure) E anthers and gynostemium F the dehiscent capsule G seed. Illustration by Shizhen Qiao.

Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma, sp. nov.

  

Diagnosis: Isotrema cangshanense is morphologically similar to Isotrema utriforme (S. M. Hwang) X. X. Zhu, S. Liao & J. S. Ma, I. forrestianum (J. S. Ma) X. X. Zhu, S. Liao & J. S. Ma, I. cucurbitoides (C. F. Liang) X. X. Zhu, S. Liao & J. S. Ma and I. obliquum (S. M. Hwang) X. X. Zhu, S. Liao & J. S. Ma (Zhu et al. 2019a), but is distinguishable from these species by the following diagnostic characters: laminas oblong-lanceolate; calyx outside light yellow; limb narrow-ovoid, 2.4–3 × 0.9–1 cm, asymmetric, forming an acute angle with the upper part of the tube, 3-lobed, upper part separated to the middle, lower part shallowly lobed, inside black purple, net-shaped protruding stripes; throat ca. 5 mm in diam. ....

Figure 4.
A–C Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma, sp. nov. A leaves B flower (lateral view) C longitudinal section of flower (showing the inside structure)
D–F Isotrema utriforme (S. M. Hwang) X. X. Zhu, S. Liao & J. S. Ma D leaves E flower (lateral view) F longitudinal section of flower (showing the inside structure)
G–I I. forrestianum (J. S. Ma) X. X. Zhu, S. Liao & J. S. Ma G leaves H flower (lateral view) I longitudinal section of flower (showing the inside structure)
J–L I. obliquum (S. M. Hwang) X. X. Zhu, S. Liao & J. S. Ma J leaves K flower (lateral view) L longitudinal section of flower (showing the inside structure).

 A–C, G–I Photographed by Xinxin Zhu D–F photographed by Lei Cai; J–L photographed by Yuan Wang.

    

Etymology: The specific epithet derives from the type locality, The Cangshan Mountain, Yangbi County, western Yunnan, south-western China. The Chinese name is given as “苍山关木通”.

Distribution and habitat: The new species is currently known only from the Cangshan Mountain, Yangbi County, Yunnan, China. It grows in forests at an elevation between 2239 m and 2379 m, together with Castanopsis sp. (Fagaceae), Disporum sp. (Colchicaceae), Notochaete hamosa Benth. (Lamiaceae), Photinia Lindl. (Rosaceae), Rubus sp. (Rosaceae) etc.

 Xin Xin Zhu, Hai Lei Zheng, Jun Wang, Yong Qian Gao and Jin Shuang Ma. 2019. Taxonomic Studies on the Genus Isotrema (Aristolochiaceae) from China: I. I. cangshanense, A New Species from Yunnan.  PhytoKeys. 134: 115-124. DOI: 10.3897/phytokeys.134.37243