Phylogenetics of South American Asclepiadoideae (Apocynaceae)

According to analyses of plastid DNA, New World Asclepiadoideae (Apocynaceae) fall into four clades; most species, however, are included in just one clade endemic to the New World that comprises Metastelmatinae, Oxypetalinae and Gonolobinae (the MOG clade). Looking for better support and resolution inside the MOG core group, we sequenced the nuclear ribosomal DNA region ITS and increased the number of plastid regions (trnS-G and matK) sequenced. Because of high levels of intra-individual polymorphisms and complex alignment among subtribes, ITS could not be used at the subtribal level. According to combined analysis of the plastid regions, Blepharodon lineare and Funastrum clausum are confirmed as sister group to the rest of Metastelmatinae and Oxypetalinae, respectively. The analysis indicates that Ditassa is polyphyletic. A highly supported clade composed of shrubby species with minute leaves that were traditionally classified in Ditassa comes out as sister to the rest of the subtribe apart from B. lineare. These data clearly support the recognition of a new genus in Metastelmatinae.