Abstract
We present a dated phylogenetic tree for the Neotropical genus Attalea (Arecaceae). We used six orthologues from the nuclear WRKY gene family across 98 accessions to address relationships among species and biogeographical hypotheses. We found that the formerly recognized groups within Attalea are not monophyletic and therefore there is no support for multiple genera as previously thought. Species of Attalea-like palms from the Atlantic forest form a well-supported clade sister to the Attalea species from Amazonia, the Andean valleys and Mesoamerica. Dates for the main divergence events suggest a relationship with the development of the dry forests that now span eastern South America and the now-lost Pebas Lake region in the western Amazon. Attalea crassispatha possibly colonized Hispaniola by a long-distance dispersal event, not via the land bridge Great Antilles Avian Ridge (GAAR), before the Panama channel closed. The common ancestor of Attalea appears to have been an Atlantic forest clade c. 30 Mya. The early split between the Atlantic-forest clade and the two Amazonian-northern Andean clades was probably the result of climatic changes that caused an increase in aridity in South America.