Systematics of Baccharis (Asteraceae: Astereae)

Abstract

A comprehensive phylogenetic hypothesis for the predominantly Neotropical American genus Baccharis is necessary to test its monophyly and clarify the infrageneric relationships within the genus. Given its great morphological diversity and wide geographic distribution, phylogenetic studies based on molecular data to test the monophyly of the genus and investigate the relationships of its infrageneric groups are here proposed, allowing the recognition and taxonomic revision of smaller and monophyletic taxa. Therefore, a phylogenetic hypothesis for Baccharis is provided based on 248 species sampled, four molecular regions and Bayesian analyses. The results confirm subtribe Baccharidinae as a monogeneric lineage, and support a wide definition of Baccharis s.l., monophyletic and including all genera that were previously segregated from it. Baccharis subgen. Tarchonanthoides Heering, a group restricted to the southeastern South American grasslands and savannas, was chosen as a good target to first tackle for a taxonomic revision, due its small size, restricted area of occurrence when compared to the remaining subgenera, and morphological distinctiveness. This is the first attempt to provide a taxonomic revision of a subgenus of Baccharis according to a phylogenetic framework, and under no geographic constraint. Alongside the main goals, exploratory fieldwork and study of herbaria specimens allowed the description of eight new species. (AU)