Phylogenetic systematics of Hoya (Apocynaceae)

Hoya with perhaps 300 species is one of the most diverse angiosperm genera in the tropical rainforests of Southeast Asia and New Guinea. Knowledge of the number of species and their relationships is still very unsatisfactory. Floral characters have been used to subdivide the genus into sections, although none of these groups were based on phylogenetic relationships. Recently, molecular phylogenetic studies have shed new light on the intrageneric relationships of the genus by identifying three main monophyletic clades, in addition to a core Hoya group that includes most of the species examined. One clade includes New Guinean/Australian species, while the other two, the Acanthostemma and the Eriostemma clades, mainly correspond to existing sections. I here discuss the phylogenetic findings in the light of the traditional morphological classifications, as a first step towards a new classification of Hoya based on phylogenetic relationships.