A PRELIMINARY MOLECULAR PHYLOGENY OF THE ABAREMA ALLIANCE (LEGUMINOSAE) AND IMPLICATIONS FOR TAXONOMIC REARRANGEMENT

Premise of research. Here we present the first molecular phylogeny of the Abarema alliance, based on a large species sampling from across its geographical range. Our aim was to test the monophyly of the alliance and to analyze the major biogeographical patterns throughout the Neotropics. Methodology. DNA sequence data were derived from the chloroplast matK region and nuclear external transcribed spacers (ETSs) and were phylogenetically analyzed in order to resolve systematic relationships. Pivotal results. Our results agree in part with Barneby and Grimes’s circumscription of the alliance, including the genera Hydrochorea and Balizia and part of Abarema. However, Abarema, the largest genus within the alliance, is polyphyletic. The type species of Abarema, Abarema cochliacarpos, is closer to genera of the Inga alliance. There is also an Andean clade distinct from the remaining species of Abarema sensu lato, Hydrochorea, and Balizia. Conclusions. Two groups of Abarema sensu lato (one restricted to the Andes), but excluding the type species A. cochliacarpos, are here proposed, together with the genera Hydrochorea and Balizia, as a new alliance. The results demonstrate that monophyletic groups have to be recircumscribed and some described as new taxa. We also present preliminary observations about the biogeography of the group in different Neotropical forest formations. The Andean clade appears as sister to all other taxa within the new alliance when combined ETS and matK data are analyzed. Multiple independent events must have occurred during the colonization of the West Indies and Central America. Species in the Atlantic forest and Amazonia are the result of the most recent radiation events within the group.