Chloroplast phylogenomic data support Eocene amphi‐Pacific early radiation for the Asian Palmate core Araliaceae

Traditional phylogenies based on analysis of multiple genes have failed to obtain a well‐resolved evolutionary history for the backbone of the Asian Palmate group of Araliaceae, the largest clade of the family. In this study, we applied the genome skimming approach of next‐generation sequencing to address whether the lack of resolution at the base of the Asian Palmate tree is due to molecular sampling error or the footprint of ancient radiation. Twenty‐nine complete plastid genomes of Araliaceae (17 newly sequenced) were analyzed (RAxML, Beast, Lagrange, and BioGeoBears) to provide the first phylogenomic reconstruction of the group (95% of genera included). As a result, the early divergences of the Asian Palmate group have been clarified but the backbone of its core is not totally resolved, with short internal branches pointing to an ancient radiation scenario. East Asia is inferred as the most likely ancestral area for the Asian Palmate group (from late Paleocene to Eocene) from which early colonization of the Neotropics is inferred during the Eocene. The radiation of the core Palmate group took place during the late Eocene, most likely in the context of the Boreotropical hypothesis. Recurrent episodes of southward migration (to the tropics) coupled with northern latitude local extinctions (promoting geographic isolation of lineages) followed by northward expansion (promoting contact of lineages that erased the trace of preceding geographic isolation) are hypothesized to have linked to the alternation of the cold and warm periods of the Eocene.