Molecular phylogeny of the palm genus Chamaedorea, based on the low-copy nuclear genes PRK and RPB2

Sequence data from the low-copy nuclear genes encoding phosphoribulokinase (PRK) and the second largest subunit of RNA polymerase II (RPB2) are used to generate the first phylogenetic analysis of Chamaedorea (Arecaceae: Arecoideae: Chamaedoreeae), the largest neotropical genus of palms. The prevailing current taxonomy of Chamaedorea recognizes approximately 100 species in eight subgenera, all delimited using floral characters, which provide a useful starting point to explore species-level systematics. Sequence data from 63 species, including representatives of all eight subgenera, were analyzed using maximum parsimony and Bayesian inference optimality criteria. Genus Chamaedorea is resolved as monophyletic with strong support in all separate and combined analyses. The less species-rich subgenera are convincingly monophyletic and can be diagnosed using morphological synapomorphies. In contrast, the two largest subgenera, Chamaedorea and Chamaedoropsis, which are supposedly distinguishable from each other by the degree of connation in the staminate petals, are both resolved as highly polyphyletic. Several well supported monophyletic groups resolved by these gene regions have never before been proposed within Chamaedorea and are challenging to delimit using morphological criteria. Although PRK proved more informative than RPB2, both regions have strong utility for interpreting species-level relationships among the palms, which are notoriously recalcitrant subjects for molecular phylogenetic studies. In addition, a paralog of the target copy of PRK identified during the analysis represents a potentially valuable source of phylogenetic information for future studies.