Abstract: Six temperate woody bamboos (Arundinarieae, Bambusoideae) from Madagascar were described in the genus Arundinaria during the 1920s to 1960s. However, recent phylogenetic studies imply that Arundinaria is restricted to North America, and taxonomic affiliation of the Malagasy temperate woody bamboos remained ambiguous. In search of phylogenetic affinity of these bamboos, herbarium observation, fieldwork, and molecular phylogenetic analysis have been carried out. Four of them and one potential new species were sampled for molecular phylogenetic analyses in the context of the tribe Arundinarieae. Maximum likelihood and Bayesian analyses indicated that those species were closely related to Oldeania alpina distributed in continental Africa, but not Arundinaria, Bergbambos, Fargesia (includingSinarundinaria), Thamnocalamus, or Yushania, in which they were placed at one time or another. On the grounds of molecular phylogeny, morphology, and phytogeography, the Malagasy temperate woody bamboos should be treated as members of the genus Oldeania. Arundinaria humbertii and A. ambositrensis are conspecific. A new species, Oldeania itremoensis, is described and illustrated. The other two temperate woody bamboo species in Madagascar not sampled in the molecular phylogeny are also transferred to Oldeania on the basis of morphology.

Key words: Arundinarieae, new combinations, Oldeania, plastid markers