Benstonea Callm. & Buerki (Pandanaceae): Characterization, circumscription, anddistribution of a new genus of screw-pines, with a synopsis of accepted species

Pandanaceae, a palaeotropical monocot family of c. 700 species, comprises four currently recognized genera: Freycinetia Gaudich., Martellidendron (Pic. Serm.) Callm. & Chassot, Pandanus Parkinson and Sararanga Helms. Within Pandanus (c. 500 spp.), species of sect. Acrostigma Kurz [one of four sections comprising subg. Acrostigma (Kurz) B. C. Stone] possess highly distinctive morphological features (viz. sharp spiniform, linear styles with the stigmatic groove on the abaxial side of the style and a staminate flower reduced to 1 to 3 stamens) shared with two other species (likewise belonging to subg. Acrostigma but originally placed in sect. Fusiforma B. C. Stone) that separate them from all other congeners. Based on morphology, biogeography, and recent inferences from plastid DNA sequence data, we place these distinctive species in a new genus, Benstonea Callm. & Buerki, making the necessary new combinations for the 50 recognized species, accompanied by six lectotypifications, one epitytification and two neotypifications, and placing seventeen names in synonymy. A generic key is provided to facilitate distinguishing Benstonea from the four other genera of Pandanaceae. Comments are provided on the distribution, ecology and typification of each accepted species. © CONSERVATOIRE ET JARDIN BOTANIQUES DE GENÈVE 2012.