Revisiting the wax plants (Hoya, Marsdenieae, Apocynaceae): Phylogenetic tree using the matK gene and psbA-trnH intergenic spacer

Abstract

AbstractThe genus Hoya includes over 200 species with a geographic distribution covering all eight currently recognised biodiversity hotspots in the Indomalesian‐Australasian region. Despite the great horticultural interest in Hoya, which includes some of the most commonly cultivated ornamental plants, very little is known about their evolution and a phylogenetic classification for the genus is lacking. Here we explore the phylogeny of 81 species of Hoya and close relatives by adding DNA sequences of the chloroplast matK gene and the psbA‐trnH intergenic spacer to an existing molecular dataset consisting of nuclear ITS sequences and chloroplast sequences of the trnL region and the atpB‐rbcL spacer. The topology obtained confirms previously identified clades in Hoya and resolves the phylogenetic relationships among a greater number of species. The phylogenetic position of Eriostemma, a section that is well defined by morphological characters, remains unresolved. However, Clemensiella mariae is here shown for the first time to be part of Hoya and sister to sect. Eriostemma, pointing to the urgent need of intrageneric revisions in the tribe Marsdenieae. At least two additional sections, Hoya and Otostemma, do not reflect phylogenetic relationships and should not be retained in taxonomic revisions of the genus.