Polyphyly of Arundinoideae (Poaceae): Evidence from rbcL Sequence Data

Sequence data from the plastid encoded gene rbcL are used to determine phylogenetic relationships between various lineages in the grasses, with particular emphasis on the subfamily Arundinoideae. Thirty four sequences, producing 155 phylogenetically informative sites, were analysed using both parsimony and distance methods. Cladistic analyses indicate that there are two main lineages: Pooideae (including the Stipeae) and a large clade comprising Panicoideae, Arun- dinoideae, Chloridoideae, and Centothecoideae. The Bambusoideae are unresolved and basal to these two lineages. Relationships within the panicoid, arundinoid, chloridoid, and centothecoid clade indicate that Arundinoideae as presently circumscribed are paraphyletic, as lineages within this subfamily show affinities with all three of the other subfamilies. Despite poor support for some relationships, rbcL appears to be well suited for systematic studies in the Poaceae.