A phylogeny of the Areae (Araceae) implies that Typhonium, Sauromatum, and the Australian species of Typhonium are distinct clades

With in excess of 70 species, the Southeast Asian/Australian genus Typhonium is the largest genus of the Areae, a tribe that includes up to nine smaller genera of which Sauromatum and Lazarum have recently been reduced to the synonymy of Typhonium. To test the circumscription and relationships of Typhonium to the other Areae, we used chloroplast and nuclear DNA sequences (4319 aligned nucleotides) for 86 of the total 153 species, including representatives of all relevant genera. In the resulting phylogeny, Typhonium species fall into three well-supported clades: the first comprises most Typhonium species, including the type, T. trilobatum; the second consists of the type of Sauromatum, S. guttatum, and other species formerly placed in that genus; the third includes only Australian endemics. Each of the remaining six genera of Areae is monophyletic. Sauromatum and Typhonium are not sister groups, requiring the recognition of Sauromatum. The Australian clade also needs to be ranked as a genus to achieve similar levels of morphological, geographic, and genetic distinctness among the genera of Areae. However, since only 10 of the 16 described Australian endemics currently placed in Typhonium have so far been sequenced, not including the type of the name of the Australian genus Lazarum, we refrain from applying this name to the Australian clade. Among the nomenclatural and taxonomic results of this study are a key to the nine species of Sauromatum, and five new combinations. We also report two new chromosome counts and discuss the implications of the molecular phylogeny for the evolution of Sauromatum karyotypes.