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

Abstract

Distephanus Cass. comprises 43 distinctive species of shrubs and small trees that have been placed historically within the ironweed tribe, Vernonieae (Asteraceae). Using 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 as well as ancestral area reconstruction analyses to infer the biogegraphic history of species diversity in this group. Results from this study indicate that, as currently circumscribed, Vernonieae is not monophyletic and that Distephanus is, in fact, sister to a clade that comprises Vernonieae and another tribe, Moquinieae, which only includes two species restricted to Brazil. On the basis of these findings, Distephanus is classified in a new tribe that we describe here, Distephaneae. This new tribe comprises 41 species of Distephanus that are easily distinguished from Moquinieae and Vernonieae based on the presence of florets with yellow corollas and trinervate leaves.