The genus Pandanus Parkinson (Pandanaceae) on Halmahera Island (Moluccas, Indonesia) with descriptions ofthree new species and a key to the species on the island

Halmahera is the largest (c. 18,000 km²) island of the Moluccan archipelago, but naturalists have only sporadically visited Halmahera and it has remained very poorly explored botanically. However, an intensive botanical inventory project was undertaken between 2012 and 2014 in part of the island to inform flora biodiversity management for certain proposed mining activities. This effort has contributed over 3600 plant collections and nearly doubled the number of Pandanus Parkinson (Pandanaceae) specimens (bringing the total to 55) available for Halmahera. After careful examination ofall available material and comparison with other material from the region, we are able to present the first overview of the genus for the island. We have identified ten species from the island ofwhich three are new to science and not known elsewhere, while the other seven are all representatives ofspecies already described from other localities. The new species are formally described here as Pandanus beguinii Callm. & A. P. Keim, Pandanus benstoneoides Callm., Buerki & Phillipson and Pandanus halmaherensis Callm. & A. P. Keim. The new species are provided with notes on their respective morphology and known distributional and ecological ranges, line drawings. Those three new species are assigned a preliminary status of Endangered following IUCN Red List Categories and Criteria. All ten species are illustrated with colour photographs and a key to the species is provided.