Evolution and Origins of Polyploid Sonchus (Subgenus Sonchus) and the Woody Sonchus Alliance

The Sonchinae is the most widely distributed subtribe in the tribe Cichorieae, with a discontinuous, almost cosmopolitan, and very peculiar phytogeographic distribution. In particular, genus Sonchus subgenus Sonchus, appears to be responsible for the origin of several island endemics both in the Pacific Ocean (Dendroseris, Thamnoseris, Actites, Kirkianella and Embergeria ) and the Atlantic Ocean (woody Sonchus alliance in the Macaronesian Islands). So polyploidy Sonchus and their relative Pacific polyploidy endemics are an ideal system to study the polyplodization for the island plants. Several hypotheses have been proposed based on the morphology and karyology. We use the cloning technique to retrieve the different ITS repeat types in order to test the origin of several polyploidy Sonchus as well as polyploidy in the related Pacific islands. The Pacific endemics (Dendroseris, Embergeria, Kirkianella, and Actites) are all formed the monophyletic clade with all the their repeat types which support the single origin of these endemics. S. arvensis has been identified as a potential allopolyploid. The Stebbins hypothesis of allpolyploid origin for S. oleraceus is partially supported with confirmation of S. asper as one donor. The data also indicate a hybrid origin for S. hydrophilus which might have subsequently homogenized with ITS copies from the hybrid ancestor via concerned evolution.The woody Sonchus alliance is one of the largest Macaronesia diverse endemic groups with 6 genera and approximately 31 species. Determining accurate phylogenetic relationships among the members of the woody Sonchus alliance presents challenges because of insufficient level of molecular variation and the convergent evolution of similar morphological traits in island settings. All taxa of woody Sonchus alliance were sampled to investigate the phylogenetic relationships as well as to test the potential role of hybridization and introgression using three independent low-copy nuclear genes: glyceraldehyde 3-phosphate dehydrogenase (G3pdh) , B12 and calmodulin (Cam) . B12 and CAM phylogeny is not well resolved due to the limited informative sites. The G3PDH data set was not significantly different from that of B12 and CAM,and subsequent combined analysis provided a better resolved and supported phylogeny within the alliance. In the MP combined tree, the basal lineages of monotypic genera were not identified. The all Taeckholmia species except T. arborea formed a well-support clade. It partly supports Boulos' classification to treat Taeckholmia as a genus. But the Dendrosonchus is highly polyphyletic which does not support either Boulos' or Aldridge's classification of tree Dendrosonchus. Assessment of the role of hybridization and introgression was limited due to low sequence variability of B12 and CAM genes, however, potential hybridization has been recognized comparing independent gene regions. The members of woody Sonchus alliance display extensive morphological, ecological, and anatomical diversity, but all taxa have a uniform chromosome number. Furthermore, all the members have no crossing barriers, there are extensive opportunities for hybridization between these species. We include two independent low-copy nuclear genes: glyceraldehyde 3-phosphate dehydrogenase (G3PDH) and Calmodulin (CAM) with the cloning with several key species to test the possible homoploid hybrid speciation. There is no evidence in our data to support a hybrid origin for the monotypic species (Babcockia platylepis, Sventenia bupleuroides and Lactucosonchus webbii). The hybridization between Dendrosonchus and Taeckholmia is not supported in our data. S. tuberifer might have hybrid origin between herbaceous and small woody species