Phylogeny and divergence times of Bactridinae (Arecaceae, Palmae) based on plastid and nuclear DNA sequences

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Abstract:

Bactridinae include about 150 species of spiny Neotropical palms in five genera that are ecologically important in several vegetation types such as open woodland (Acrocomia), lowland rainforest (Astrocaryum, Bactris), and montane forest (Aiphanes). The subtribe also includes the only exclusively lianescent palm genus in the Neotropics (Desmoncus). We present a fully resolved molecular phylogeny of 41 species of Bactridinae, representing all genera as well as most of the currently ac - cepted infrageneric taxa (subgenera, sections etc.) 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 the generic level are monophyletic with high support. Astrocaryum alatum and A. mexicanum, recently segregated into a genus of their own (Hexopetion), form a strongly supported monophyletic group sister to the remaining Astrocaryum species. Desmoncus and Acrocomia are resolved as sister genera, and together they are sister to the remaining Bactridinae. This finding contrasts with that of two previous studies reporting Acrocomia to be sister to the rest of the subtribe. Aiphanes is resolved as sister to Bactris and Astrocaryum. Species-level relationships recovered within Astrocaryum and Bactris disagree to a large extent with previous morphology-based infrageneric classifications, suggesting that those characters are homoplasious, particularly within Bactris . A Bayesian dating analysis using the relaxed-clock model indicates that most genera of Bactridinae diverged during a relatively short period around the Eocene–Oligocene boundary, which might explain the difficulties in resolving the phylogenetic backbone of the group. The mostly Andean genus Aiphanes shows an initial radiation of early lineages in the Oligocene (around 25 Ma ago) corresponding to an early uplift phase of the cordillera. These taxa are nowadays restricted to the mountain forests of Colombia and Ecuador. The main diversification of Andean Aiphanes began in the Miocene (around 11 Ma ago). This study provides the first substantial insight into Bactridinae phylogeny and sets the stage for more comprehensively sampled species-level studies analysing drivers of diversity of Neotropical palms, speciation patterns, character evolution, or biogeography.

Keywords: AIPHANES; ARECACEAE; ASTROCARYUM; BACTRIS; MOLECULAR PHYLOGENY; RELAXED-CLOCK DATING

Document Type: Research Article

Affiliations: 1: Department of Biological Sciences, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark 2: IRD, UMR DIAPC, 34394 Montpellier 5, France 3: Department of Agriculture and Ecology, University of Copenhagen, 1958 Frederiksberg C, Denmark 4: Department of Biology, Georgetown University, Washington, D. C. 20057, U. S. A. 5: Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Apartado 7495, Bogotá, Colombia

Publication date: April 1, 2011

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