Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma, 2019

Zhu, Xin Xin, Zheng, Hai Lei, Wang, Jun, Gao, Yong Qian & Ma, Jin Shuang, 2019, Taxonomic studies on the genus Isotrema (Aristolochiaceae) from China: I. I. cangshanense, a new species from Yunnan, PhytoKeys 134, pp. 115-124 : 115

publication ID	https://dx.doi.org/10.3897/phytokeys.134.37243
persistent identifier	https://treatment.plazi.org/id/170BBC0E-92DF-58BF-AB5C-28E83D80401E
treatment provided by	PhytoKeys by Pensoft
scientific name	Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma
status	sp. nov.

Treatment

Isotrema cangshanense X.X.Zhu, H.L.Zheng & J.S.Ma sp. nov. Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 A–C View Figure 4

Type.

China. Yunnan: Yangbi County, The Cangshan Mountain, Sancha River, 25°41'49"N, 100°02'55"E, 2239 m a.s.l., 23 April 2019, X. X. Zhu et al. ZXX19353 (holotype: CSH [CSH-0164770!]; isotypes: CSH!, KUN!).

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. Detailed morphological comparisons are shown in Table 1 View Table 1 and Figure 4 View Figure 4 .

Description.

Woody liana. Stems terete, young shoots pubescent. Petioles 0.7-3.5 cm long, pubescent to almost glabrous; laminas oblong-lanceolate, 6-20 × 1-7 cm, adaxially almost glabrous, abaxially villous, base auriculate, sinus 0.7-1.8 cm deep, apex acute, margin entire; basal veins 2-3 pairs, palmate, 2-3 pairs from base, lateral veins 12-18 pairs, pinnate. Flowers in axils of leafy shoots or, on older stems, solitary or in fascicles, each fascicle with 2-6 flowers; pedicels 1.5-4 cm, pubescent partly villous; bracteole 1, lanceolate, 2-5 × 1-2 mm, adaxially glabrous, abaxially densely villous, inserted below the middle of pedicel. Calyx tube geniculately curved, outside light yellow, abaxially sparsely pubescent partly villous; basal tube 1.8-2.5 × 0.5-0.6 cm, inside black purple, densely villous at base; upper tube 1.3-1.6 × 0.6-0.8 cm, inside black purple at base, light yellow towards apex, light red at upper part; limb saccate, narrow-ovoid, asymmetric, forming acute angle with upper part of the tube, 2.5-3 × 0.7-0.8 cm, 3-lobed, upper part separated to the middle, lower part shallowly lobed, upper two lobes triangular-lanceolate, 1.2-1.5 × 0.4-0.5 cm, lower lobe triangle, 0.4-0.7 × 0.4-0.5 cm, inside black purple, net-shaped protruding stripes; throat ca. 5 mm in diam. Anthers 6, oblong, ca. 1.5 mm long, adnate in 3 pairs to base of gynostemium, opposite to lobes. Gynostemium ca. 2.7 × 2.5 mm, 3-lobed. Ovary terete, ca. 10 mm long, densely villous. Capsule obovate-elliptic, ca. 4.5 × 2 cm. Seeds obovate-elliptic, ca. 5 × 4 mm, not winged, the adaxial surface deeply concave and the abaxial surface convex, both surfaces glabrous.

Phenology.

Flowering from April to May, fruiting is predicted from July to August (we have seen is just two residual fruit from last year).

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.

IUCN Red List category.

Since Isotrema cangshanense is known from one population only, with fewer than ten individuals, the new species is assigned a preliminary status of Vulnerable (VU D2) according to IUCN Red List Criteria ( IUCN 2012), indicating a population with a very restricted area of occupancy (typically less than 20 km2) or number of locations (typically five or fewer). Although the area is under protection as a national nature reserve, habitat disturbance brought about by human activities, such as grazing and felling, may have a negative impact on the new species.

Specimens examined (Paratypes).

China. Yunnan: Yangbi County, The Cangshan Mountain, 2300 m a.s.l., 23 April 2019, X. X. Zhu et al. ZXX19354 (CSH!); the same location, 2379 m a.s.l., 23 April 2019, X. X. Zhu et al. ZXX19355 (CSH!).