Bactridinae include about 150 species of spiny Neotropical palms in five genera that are important in several vegetation types such as open woodlands (Acrocomia), lowland rainforest (Astrocaryum, Bactris) and montane forest (Aiphanes). The subtribe also includes the only lianescent palm genus in the Neotropics (Desmoncus). Phylogenetic relationships within this ecologically diverse group are, however, poorly known and past studies have failed in providing robust resolution of intergeneric relationships. We present a fully resolved molecular phylogeny of 41 species of Bactridinae, representing all genera as well as most of the currently accepted infrageneric taxa and recently proposed informal groups. Analyses are based on five plastid DNA regions (matK, trnQ-rps16, rps16 intron, trnD-trnT, trnL-trnF) and three nuclear markers (PRK, RPB2, ITS). A combined dataset was analysed with likelihood and parsimony methods. The results show that all accepted taxa at and above genus level are monophyletic with high support. Astrocaryum alatum and A. mexicanum, recently segregated into a genus of their own (Hexopetion Burret), form a monophyletic sister group of the remaining Astrocaryum species. Desmoncus and Acrocomia are resolved as sister genera, and together they are sister to the remaining Bactridinae. This finding is in contrast to two previous studies that found Acrocomia to be sister to the rest of the subtribe. Aiphanes is resolved as sister group of Bactris and Astrocaryum. Species-level relationships recovered within Astrocaryum and Bactris disagree to a large extent with infrageneric groups described in the literature, suggesting that morphological characters used for grouping species are homoplasious, especially within Bactris. Comprehensively sampled molecular phylogenies are clearly needed to infer species-level relationships and to identify morphological synapomorphies within these genera. A relaxed clock Bayesian dating analysis indicates that most genera of the Bactridinae diverged during a relatively short period around the Eocene-Oligocene boundary (33-35.5 mya). The mostly Andean genus Aiphanes shows an initial radiation of early lineages in the Oligocene (26 mya) corresponding to an early uplift phase of the cordillera. These taxa have today a relict distribution in mountain forests of Colombia and Ecuador. The major diversification of Aiphanes began in the Miocene (around 11 mya). This study provides the first substantial insight into Bactridinae phylogeny and thereby sets the stage for more comprehensively sampled species-level studies analysing drivers of diversity of Neotropical palms, speciation patterns, character evolution or biogeography.
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PALMS 2010 - International Symposium on the Biology of the Palm Family