Format: ORAL

Juan Chen1,2,Sijin Zeng1,2, Linya Zeng1, Nianhe Xia1,2

1 State Key Laboratory of Plant Diversity and Specialty Crops, South China Botanical Garden, Chinese Academy of Sciences, 510650, Guangzhou, People’s Republic of China 2 South China National Botanical Garden, 510650, Guangzhou, China

Costaceae comprises seven genera and 143 species, widely distributed in tropical and subtropical regions. One genus with five species was recorded in Flora of China. Since then, there has been no comprehensive taxonomic revision on Costaceae from China. Therefore, based on extensive historical literature and herbarium studies, the relationships and classification of Costaceae from China were studied by means of field survey, morphology, and molecular phylogeny. The main results are as follows: The important characters for identification of species from China include bracts (texture and shape), bracteoles (texture and shape), buds (quantity, shape, and size), stamens (anther position and appendage shape), stigmas (shape) and its dorsal appendage (shape and color), etc. Our research supported that most of Costus species from China should be transferred to Hellenia Retz. Currently, five species of Hellenia recognized from China. Hellenia deliniana ( Costus chinensis) was recovered. Two new combinations (Hellenia viridis Costus viridis, Hellenia oblonga Costus oblongus) were proposed. Plastid phylogenomic analyses of Costaceae revealed that Hellenia is strongly supported as paraphyletic. Two major clades are recovered, namely the Hellenia s.s. subclade and the Parahellenia subclade. Phylogenetic analyses based on an enlarged taxon sampling of the Asian clade using a two chloroplast markers dataset (trnK intron and trnL-F spacer) confirmed the paraphyly of Hellenia. Meanwhile, morphological analyses suggested that members of the Parahellenia subclade differ from the remaining Hellenia species in many characters including inflorescences, bracts, stigma, axillary buds, floral tubes, and labellum. According to the present molecular and morphological evidence, the latter subclade is recognized as a new genus, Parahellenia. Two new species are described, four new combinations are made, and identification keys are also provided.