Format: ORAL

Kenneth M. Cameron1, Shenyi Wang1, Pan Li2

1 Department of Botany, University of Wisconsin-Madison, USA 2 Zhejiang University, Hangzhou, P.R. China

Liliaceae always have been a challenge to classify and the taxonomy of one subfamily, Streptopoideae, also has been plagued with controversy. As currently circumscribed Streptopoideae contain three genera: Prosartes, Scoliopus, and Streptopus with 17 species distributed across the Northern Hemisphere. A few of the species even exhibit inter-continental disjunctions. Although several higher-level molecular phylogenetic studies have included a handful of species from this subfamily as placeholders, the whole picture of finer scale phylogenetics among these plants has never been studied adequately. We resolved the phylogenetic relationships, estimated divergence times among clades, and reconstructed historical biogeography within Streptopoideae and several outgoup taxa using newly sequenced de novo assembled and annotated whole chloroplast genomes. We achieved a high level of sampling for the ingroup (15 of 17 species), and also considered a moderate level of intraspecific sampling for the two species, S. amplexifolius and S.lanceolatus, with the widest geographic distribution. We compared and contrasted the structure of Streptopoideae plastomes, demonstrating that they have relatively large genomes, but with same gene arrangement that characterizes other Liliaceae. A relatively well resolved and supported phylogenetic reconstruction supports the North American genera Prosartes and Scoliopus sharing a recent common ancestor, with Streptopus as sister to them. The subfamily diverged from its shared ancestor with Tricyrtis at least 57 Mya in the late Paleocene of either Western North America or East Asia. The species of Streptopus in North America appear to have migrated to the east from Asia more recently. Relationships within each genus are fully resolved, but mostly supported only by short branch lengths. One individual of S. lanceolatus from the Pacific Northwest showed evidence of chloroplast capture from sympatric S.amplexfolius.These results indicate that alternative molecular methods targeting the nuclear genome will be needed to further tease apart the evolutionary history of this group.