Reinstatement of Isotrema, a new generic delimitation of Aristolochia subgen. Siphisia (Aristolochiaceae)

Abstract

Aristolochia subgen. Siphisia, comprising 98 species, is mainly distributed in East and South Asia, with some scattered in North and Central America. It has often been recognized as one of three subgenera of Aristolochia and can be distinguished from both remaining subgenera (Aristolochia subgen. Aristolochia and Aristolochia subgen. Pararistolochia) by morphological synapomorphies such as a strongly curved perianth with a 3-lobed limb, and especially the 3-lobed gynostemium, anthers paired on the outer surface of each gynostemium segment. However, recent cladistic analyses based on morphological characters and molecular data suggested that Aristolochia s.l. should be divided into four genera in two subtribes. In this study, a comprehensive analysis of molecular data of two plastid genic spacers (rps16-trnK and petB-petD), and two nuclear genes (phyA and ITS2) with an extensive sampling of Asian and American species was conducted. The combined datasets confirmed that Aristolochia subgen. Siphisia should be treated as an independent genus. Then Isotrema is reinstated here with 87 new combinations for the most comprehensive enumeration.

Taxonomic studies on the genus Isotrema (Aristolochiaceae) from China: II. I. brevilimbum (Aristolochiaceae), a new species from Guizhou, China

“…Zhu, S. Liao & J.S. Ma was recently published (Zhu et al 2019a) based on its basionym A. wardiana J.S. Ma, previously only known from Myanmar and India (Ma 1989a), which was recently collected from Medog County, Tibet, and here its distribution in China is confirmed.…”

“…I. brevilimbum (Aristolochiaceae), a new species from Guizhou, China Introduction Isotrema Raf. (Aristolochiaceae), previously treated as a subgenus of Aristolochia L., was recently reinstated as an independent genus based on molecular and morphological evidence (Zhu et al 2019a). It can be distinguished from Aristolochia by the follow-ing set of characters: perianth strongly curved, gynostemium 3-lobed, anthers paired on the outer surface of each gynostemium segment, and capsule dehiscing basipetally (Do et al 2015a;Zhu et al 2019a).…”

“…(Aristolochiaceae), previously treated as a subgenus of Aristolochia L., was recently reinstated as an independent genus based on molecular and morphological evidence (Zhu et al 2019a). It can be distinguished from Aristolochia by the follow-ing set of characters: perianth strongly curved, gynostemium 3-lobed, anthers paired on the outer surface of each gynostemium segment, and capsule dehiscing basipetally (Do et al 2015a;Zhu et al 2019a). Several new species of Isotrema have been found and described from China and its neighbouring countries during recent years (Liu and Deng 2009;Xu et al 2011;Yao 2012;Huang et al 2013Huang et al , 2015Wu et al 2013Wu et al , 2015Do et al 2014Do et al , 2015aDo et al , 2015bDo et al , 2015cDo et al , 2015dDo et al , 2016Do et al , 2019Huong et al 2014;Lu and Wang 2014;Ohi-Toma et al 2014;Zhu et al 2015Zhu et al , 2016Zhu et al , 2017aZhu et al , 2017bZhu et al , 2018Zhu et al , 2019bZhu et al , 2019cGong et al 2018;Yang et al 2018;Li et al 2019;Peng et al 2019;Zhou et al 2019;Cai et al 2020aCai et al , 2020b.…”

“…China accommodates ca. 66 species, among which 55 species are endemic (Huang et al 2003;Li et al 2019;Peng et al 2019;Zhou et al 2019;Zhu et al 2019aZhu et al , 2019bZhu et al , 2019cZhu et al , 2019dCai et al 2020aCai et al , 2020b.…”

“…During our recent field explorations to southern China, an unknown species of Isotrema was collected. Our subsequent examination of specimens from 39 public herbaria (A, BM, BR, CDBI, CSFI, CSH, E, EMA, GXMI, HAST, HENU, HHBG, HIB, HITBC, HNWP, IBK, IBSC, K, KYO, KUN, L, LBG, LE, NAS, NTUF, P, PE, PEM, SM, SNU, SYS, TAI, TI, W, WCU, WU, WUK, XYTC, YUKU; abbreviations follow Thiers 2020) and study of related literature (Hwang 1981(Hwang , 1988Ma 1989aMa , 1989bTao 1997;Huang et al 2003;Do et al 2015a;Do and Nghiem 2017;Yang et al 2018;Zhu et al 2019aZhu et al , 2019d suggested it to be a new species. Hereafter, we describe it as I. brevilimbum X.X.Zhu, Jun Wang & F.Cao.…”