Isotrema sanyaense, a new species of Aristolochiaceae from Hainan, China Author Li, Rongtao Author Wang, Zhiwei Author Wang, Jun Author Zhu, Xinxin Author Xu, Han text PhytoKeys 2019 128 85 96 http://dx.doi.org/10.3897/phytokeys.128.35042 journal article http://dx.doi.org/10.3897/phytokeys.128.35042 1314-2003-128-85 55651BFDC4A35FC6805717910ACA6DB8 3371818 Isotrema sanyaense R.T.Li, X.X.Zhu & Z.W.Wang sp. nov. Figs 1 , 2 , 3 Diagnosis. Isotrema sanyaense is most similar to I. ledongense (Han Xu, Y.D.Li & H.J.Yang) X.X.Zhu, S.Liao & J.S.Ma and I. jianfenglingense (Han Xu, Y.D.Li & H.Q.Chen) X.X.Zhu, S.Liao & J.S.Ma ( Zhu et al. 2019 ), but significantly differs in the following characters: cymes 1-5-flowered, in hanging clusters of 1 to numerous branches, the pedicel nearly equal in length to flower, upper calyx tube obviously longer than basal calyx tube, calyx limb discoid, yellow inside, with purple-red stripes and spots, about 13-18 mm in diameter, glabrous, the throat dark red without spots, 4-6 mm wide. A detailed morphological comparison among the three species is shown in Figure 4 and Table 1 . Figure 1. Isotrema sanyaense R.T.Li, X.X.Zhu & Z.W.Wang, sp. nov. A flowering branch B leaf C flower (front view) D flower (lateral view) E opened flower (showing the inside structure) F anthers and gynostemium G fruit H seeds. Scale bars: 6 cm ( B ); 1 mm ( C, D, E ); 5 mm ( F ); 2 cm ( G ); 3 mm ( H ). Figure 2. Isotrema sanyaense R.T.Li, X.X.Zhu & Z.W.Wang, sp. nov. A habit B leaves (adaxially and abaxially) C inflorescence D flower (lateral view) E opened flower (showing the inside structure) F anthers and gynostemium G fruit H seeds. Scale bars: 1 cm ( B, C ); 2 cm ( D, E, G ); 5 mm ( F, H ). Type. CHINA. Hainan: Sanya City, Haitang District, Haitangwan Town, 18°17'22"N , 109°39'45"E , 332m a.s.l., 28 October 2017 (fl), X.X.Zhu & R.T.Li ZXX17105 (holotype: CSH-0146607!; isotype: CSH!, KUN!). Description. Woody liana. Young stems terete, densely villous, with yellow to brown trichomes, old branchlets glabrous, old stems leafless. Petioles 0.8-1.7 cm long, young ones densely villous, with yellow to brown trichomes mixed with a white pubescence; blades lanceolate or elliptic-lanceolate, entire, 9-14 x 3-6 cm, leathery, adaxially glabrous, abaxially villous, with sparse larger white appressed trichomes, mixed with shorter white pubescence, veins pinnate, 5 to 10 pairs, base shallowly cordate to cordate, sinus <2-3 mm deep, apex acute. Cymes lateral on old woody stems or axillary, 1-5-flowered, in hanging clusters of 1 to numerous branches, pedicels 1.1-2.6 cm long, densely villous, with yellow to brown trichomes; bracteoles ovate-lanceolate, ca. 0.2-0.4 x 0.4 mm, inserted at the basis of pedicel, adaxially glabrous, abaxially densely villous, with yellow to brown trichomes. Calyx horseshoe-shaped, externally white with purple-red stripes; abaxially densely villous, with yellow to brown trichomes; basal tube ca. 2.2 x 0.5 cm, inside dark purple, with white patches spaced in the middle; upper tube ca. 2.5 x 0.5 cm, white inside, getting dark red in upper portion; calyx limb discoid, ca. 13-18 mm in diameter, abaxially densely villous, with yellow to brown trichomes, the inner surface yellow with purple-red stripes and spots, glabrous; throat dark red, 4-6 mm wide. Anthers 6, oblong, ca. 2.2 mm long, adnate in 3 pairs to base of gynostemium, opposite to lobes, dehiscence longitudinal. Gynostemium ca. 5 mm long, 3-lobed, apex acute; ovary inferior, 6-loculed, abaxially densely villous, with yellow to brown trichomes; ovules numerous; placentation axillary. Capsule oblong-ellipsoid, ca. 5 x 2 cm, dehiscing basipetally. Seeds triangular-ovate, 4-5 x 3-4 mm. Figure 3. Holotype of Isotrema sanyaense R.T.Li, X.X.Zhu & Z.W.Wang, sp. nov. [CSH-0146607]!. Figure 4. A, B Isotrema sanyaense R.T.Li, X.X.Zhu & Z.W.Wang, sp. nov. A habit B flowers C, D I. jianfenglingense (Han Xu, Y.D.Li & H.Q.Chen) X.X.Zhu, S.Liao & J.S.Ma C habit D flowers E, F I. ledongense (Han Xu, Y.D.Li & H.J.Yang) X.X.Zhu, S.Liao & J.S.Ma E flowering branch F flower (front view). Phenology. Flowering specimens have been collected in October and in fruiting specimens in May. Etymology. The specific epithet is derived from the type locality, Sanya City, in Hainan island, China. The Chinese name is given as "三亚关木通" . Distribution and habitat. Isotrema sanyaense is currently known from Haitangwan Town, Haitang District, Sanya City, Hainan Province, China. It grows in lowland dry forests dominated by families including Euphorbiaceae , Fagaceae , Lauraceae , Myrtaceae , Arecaceae and Rubiaceae at elevations between 332-400 m. Conservation status. Isotrema sanyaense is only known from two populations in Sanya City, Hainan island, China, with fewer than 30 individuals seen at each site. Therefore, 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). Additional specimens examined (paratypes). CHINA. Hainan : Sanya City, Haitang District, Haitangwan Town, 18°17'24"N , 109°39'43"E , 400m a.s.l., 28 October 2017 (vegetative), X.X.Zhu & R.T.Li ZXX17106 (CSH); same location, 18°17'29"N , 109°39'46"E , 376m a.s.l., 21 May 2018 (fr), X.X.Zhu & J.Wang ZXX18075 (CSH, KUN). Table 1. Morphological comparison of key characters among Isotrema sanyaense , I. ledongense and I. jianfenglingense .

Characters	I. sanyaense	I. ledongense	I. jianfenglingense
Leaf blade	adaxially glabrous, abaxially sparsely with white pubescence	adaxially mixed with yellow-brown villous and white pubescence, abaxially densely yellow-brown villous	adaxially sparsely yellow-brown villous and white pubescence, abaxially mixed with yellow-brown villous and white pubescence
Inflorescence	cyme 1-5-flowered, in hanging clusters of 1 to numerous branches	solitary	solitary
Pedicel	1.1-2.6 cm, nearly equal in length to flower	0.7-1 cm, significantly shorter than flower	2.7-3.5cm, nearly equal in length to flower
Calyx	white, with purple-red stripes; basal tube ca. 22 x 5 mm, upper tube significantly longer than basal tube	light yellow, with purple-red stripes; basal tube 15-16 x 4.5-5 mm, upper tube almost equal to basal tube	light red brown, without stripes; basal tube 23-26 x 5-6 mm, upper tube significantly longer than basal tube
Limb	discoid, yellow, 13-18 mm in diameter, with purple-red stripes and spots, lobes without papillae and pubescent	discoid, yellow, 5-7 mm in diameter, only with unobvious light red spots, lobes densely papillate	trumpet-shaped, pink, 8-9 mm in diameter, lobes densely papillae and white pubescent
Throat	dark red without spots, 4-6 mm wide, significantly smaller than the limb	dark red with light yellow spots, ca. 5 mm wide, significantly smaller than the limb	pink with red-brown spots, ca. 8-9 mm wide, approximately to the limb
Gynostemium	ca. 5 mm long, lobes nearly equal in length to anthers, apex acute	ca. 3 mm long, lobes significantly shorter than anthers, apex obtuse	ca. 4 mm long, lobes significantly shorter than anthers, apex curved