Molecular phylogenetics of Distephanus supports the recognition of a new tribe, Distephaneae (Asteraceae)

The genus Distephanus Cass. comprises 43 distinctive species of shrubs and small trees that have been placed historically within the ironweed tribe, Vernonieae (Asteraceae). Utilizing the most expansive sampling of Distephanus to date, this study aims to test the monophyly of this genus and facilitate its classification. Molecular phylogenetic analyses were conducted using four molecular markers from the nuclear and plastid genomes. These data also supported divergence dating analyses that were performed to understand the timing of diversification events within Distephanus and other related genera. Results from this study indicate that as currently circumscribed, Vernonieae is not monophyletic and that Distephanus is actually sister to a clade that comprises Vernonieae and another tribe, Moquinieae, which only includes two species restricted to Brazil. Based on these findings, Distephanus is recognized in a new tribe that we describe here, Distephaneae. This new tribe comprises 41 species of Disptehanus that are easily distinguished from Moquinieae and Vernonieae based on the presence of florets with yellow corollas and trinervate leaves.

Methods
Sequence data was collected from whole genomic DNA extracted from silica-preserved leaf tissue. Sequences were generated using Sanger dideoxy chain termination chemistry and chromatogram data were subsequently checked for accuracy using the software Geneious. Chromatogram data were assembled into contigs from the forward and reverse sequence and alignments for each locus were assembled using the software MAFFT. Phylogenetic reconstruction from sequence data was performed using the software IQ-TREE and MrBayes. A time-calibrated divergence dating analysis was carried out using BEAST and ancestral area reconstruction was carried out using BioGeoBEARS in R. 

Sequence data has been submitted to GenBank and Accession numbers are provided in the Appendix that accompanies this manuscript. This Dryad submission includes all multiple sequence alignments, BEAST .xml configuration files, and BioGeoBEARS scripts (as well as the accompanying geog.txt file for geographic area designation).