Divergence times, historical biogeography, and shifts in speciation rates of Myrtales

We examine the eudicot order Myrtales, a Glade with strong Gondwanan representation for most of its families. Although previous phylogenetic studies greatly improved our understanding of intergeneric and interspecific relationships within the order, our understanding of inter-familial relationships still remains unresolved; hence, we also lack a robust time-calibrated chronogram to address hypotheses (e.g., biogeography and diversification rates) that have implicit time assumptions. Six loci (rbcL, ndhF, matK, matR, 18S, and 26S) were amplified and sequenced for 102 taxa across Myrtales for phylogenetic reconstruction and ten fossil priors were utilized to produce a chronogram in BEAST. Combretaceae is identified as the sister Glade to all remaining families with moderate support, and within the latter Glade, two strongly supported groups are seen: (1) Onagraceae + Lythraceae, and (2) Melastomataceae + the Crypteroniaceae, Alzateaceae, Penaeaceae Glade along with Myrtaceae + Vochysiaceae. Divergence time estimates suggest Myrtales diverged from Geraniales similar to 124 Mya during the Aptian of the Early Cretaceous. The crown date for Myrtales is estimated at similar to 116 Mya (Albian-Aptian). BioGeoBEARS showed significant improvement in the likelihood score when the jump dispersal parameter was added. South America and/or Africa are implicated as important ancestral areas in all deeper nodes. BAMM analyses indicate that the best configuration included three significant shifts in diversification rates within Myrtales: near the crown of Melastomataceae (similar to 67-64 Mya), along the stem of subfamily Myrtoideae (Myrtaceae; similar to 75 Mya), and along the stem of tribe Combreteae (Combretaceae; similar to 50-45 Mya). Issues with conducting diversification analyses more generally are examined in the context of scale, taxon sampling, and larger sets of phylogenetic trees. (C) 2015 Elsevier Inc. All rights reserved.