Phylogenetic studies in the Hoya group (Apocynaceae, Marsdenieae): the position of Anatropanthus and Oreosparte

Recent molecular phylogenetic studies have shown that Hoya is paraphyletic without Absolmsia, Clemensiella, Madangia, and Micholitzia. These genera have been placed in synonymy with Hoya, but the monophyly of Hoya sensu lato relative to other genera of the broader Hoya group (Dischidia, Anatropanthus and Oreosparte, the latter two never included in a molecular phylogenetic analysis) remained unclear. Furthermore, no analysis has included both a significant sample of the Hoya group and outgroup genera of Marsdenieae to test the monophyly of the Hoya group and its position within the tribe. To address these gaps, we assembled two data sets: (1) the chloroplast trnT-trnL-trnF locus from 110 species and (2) three chloroplast loci (trnT-trnL-trnF, atpB-psbA spacer and matK) and two nuclear loci (nrDNA ITS and ETS) from 54 species. The Hoya group is monophyletic and nested in an Asian/Australian clade of Marsdenia s.l. The genus Hoya is paraphyletic unless Anatropanthus, Dischidia and Oreosparte are included. However, current evidence is not sufficient to synonymize Dischidia and Oreosparte with Hoya. Support for synonymy of Anatropanthus with Hoya is strong and the new name H. insularis is proposed. A clade of three new species with Oreosparte-like morphology is sister to the rest of the Hoya group and is described as the new genus Papuahoya.