Synopsis of Aristolochia L. and Isotrema Raf. (Aristolochiaceae) in China

Abstract

Aristolochia (s. l.) is widely distributed in tropical, subtropical and temperate regions of the world, with monochlamydeous and tubular flowers, gynostemia, inferior ovaries, axile placentations, pluriovulate capsules, and others as the main characters. It is the largest genus in Aristolochiaceae, which consists of about 600 species. According to Flora of China, there are 45 species in China, 33 of which are endemic. In recent years, many new species have been discovered in China, especially in Yunnan and Guangxi. Additionally, some taxa were confirmed, reinstated, republished and revised. Isotrema, previously treated as a subgenus of Aristolochia, was recently reinstated as an independent genus based on molecular and morphological evidences. This genus has strongly curved calyxes, 3-lobed gynostemia with paired anthers on the outer surface of each gynostemium segment, and basipetally dehiscent capsules. Through extensive field work, careful examination of many specimens, digital photos and related literatures, an updated checklist and identification key of Aristolochia (s. s.) and Isotrema in China are presented here. Relevant discussions and distribution for the 17 species of Aristolochia, 58 species and one subspecies of Isotrema are also provided. Among them, I. mollis and I. neolongifolia are reinstated and illustrated, the relationship among A. gentilis, A. chuandianensis and A. gracillima, and the relationship between I. kunmingense and A. bonatii are discussed, knotty taxa, such as I. ovatifolium complex, I. cucurbitoides complex, I. griffithii complex, I. versicolor complex, I. dabieshanensis complex and suspected species I. saccata, are also discussed.