Hoya ignorata(Apocynaceae, Asclepiadoideae): An Overlooked Species Widely Distributed across Southeast Asia

A new species, Hoya ignorata T. B. Tran, Rodda, Simonsson & Joongku Lee (Apocynaceae, Asclepiadoideae) is described and illustrated from Vietnam. The new taxon, widely distributed in Southeast Asia, does not seem to be related to any previously described Hoya R. Br., due to its small cupular coronas lacking lobes, and pendulous pollinia. These morphological characters, new for the genus Hoya, are discussed in light of the recent broadening of the circumscription of the genus following the results of molecular phylogenies and morphological studies.