Bidens meyeri (Asteraceae, Coreopsideae): a new critically endangered species from Rapa, Austral Islands

Bidensmeyeri (Asteraceae/Compositae) is described and illustrated from Rapa, Austral Islands, (French Polynesia). This new species is presumed to be most closely related to Bidenssaint-johniana from nearby Marotiri Island. Bidensmeyeri may be distinguished from Bidenssaint-johniana based on the length of the peduncle (3 cm versus 10 cm), apex of the inner involucral bracts (glabrous vs. puberulent), smaller leaves (2.0-2.3 cm vs. 5-6 cm), and the general smaller size of the new species. Known from less than 50 individuals and restricted to one remote location, Bidensmeyeri falls into the IUCN Critically Endangered (CR) category. The new species is named in honor of Dr. Jean-Yves Meyer, Délégation à la Recherche, Polynésie Française.