Revisiting Alpinia cumingii (Zingiberaceae): phylogenetic placement, recircumscription and a description of a new morphologically similar species

Alpinia cumingii was described by Karl Moritz Schumann from the Philippines in 1904. Two remarkably similar species, also from the Philippines, Alpinia penduliflora and Alpinia pendula, were described respectively in 1909 by Henry Nicholas Ridley and 1928 by Eduardo Quisumbing and Elmer Drew Merrill, without any reference to A. cumingii, and placed in different sections of Alpinia. A fourth morphologically similar species was collected in New Guinea during fieldwork in 2008. Using molecular data, we aim to determine the phylogenetic relationships of the four species and integrate morphological data to assess the rank at which these should be recognised. We collected new material close to the three type localities in the Philippines and used these new collections as a basis for an updated morphological description, including the previously undescribed species from New Guinea. Molecular analyses revealed that all four species grouped within the Alpinia eubractea clade both in the internal transcribed spacer (ITS) and trnK–matK regions with strong support. The undescribed species from New Guinea appeared as a sister taxon to the Philippine species in the ITS tree, whereas using the trnK–matK region, it grouped with Vanoverberghia, both with weak support. We name the species Alpinia oktediensis, referring to the type locality. Our data support A. pendula as a distinct species, whereas A. cumingii and A. penduliflora are considered conspecific. We also report a collection from Karekelong Island, as evidence for a new record of A. cumingii in the flora of Indonesia. We provide provisional conservation assessments for each species.