The Neotropical tribe Geonomeae belongs to the palm subfamily Arecoideae and consists of small or medium sized, solitary or multistemmed palms within six genera: Geonoma (approx. 60 spp.), Asterogyne (5 spp.), Welfia (1 sp.), Calyptrogyne (8 spp.), Calyptronoma (3 spp.), and Pholidostachys (5 spp.). The Geonomeae are monophyletic but previous studies based on non-coding plastid DNA sequences have not fully resolved the generic relationships within the tribe. The nuclear genes phosphoribulokinase (PRK) and intron 23 of RNA polymerase II subunit 2 (RPB2) were shown to be useful for palm phylogenetics at the species level and higher. The present study tests the utility of these two nuclear DNA markers in the phylogenetic reconstruction of tribe Geonomeae. The phylogeny includes the six genera of Geonomeae and representatives from all tribes within the Arecoideae. Our results add support to the previously reported monophyly of the tribe. The genus Geonoma is resolved as a weakly supported monophyletic group, and some groupings within the genus are resolved. Additionally, Pholidostachys is strongly supported as monophyletic. Calyptronoma and Calyptrogyne form a well-supported clade, and Calyptronoma is paraphyletic with respect to Calyptrogyne. However, the PRK and RPB2 sequences did not resolve relationships between Asterogyne and Welfia.

Key words: Arecaceae, molecular phylogenetics, phosphoribulokinase, RNA polymerase II, tribe Geonomeae