Next‐generation sequencing sheds new light on a major lineage of Acanthaceae, clarifying previously uncertain relationships in Barlerieae

Abstract The Acanthaceae tribe Barlerieae is an understudied lineage that consists of ca. 500 species, many of which are rare and range restricted. Though understudied, it is clear that many species play vital roles in tropical ecosystems, including supporting a wide range of pollinators and herbivores. The tribe contains 13 genera, the two largest and most widespread of which are the primarily Paleotropical Barleria (ca. 300 spp.) and pantropical Lepidagathis (ca. 150 spp.). In a recent reclassification of Acanthaceae, three subtribes were informally proposed based on corolla and calyx characters: (1) Barleria , (2) Crabbea and allies, and (3) Lepidagathis and allies. Using a next‐generation sequencing approach, double‐digest restriction associated DNA sequencing (ddRADseq), this study estimates a well‐sampled phylogeny of the Barlerieae tribe, tests genera and infrageneric groups for monophyly, and identifies morphological characters that support monophyletic groups. Our study reveals strong support for the monophyly of Barlerieae and resolves relationships among all 13 genera currently recognized in the tribe. There is strong support for the three proposed subtribes. Our results also suggest that taxonomic revision of Lepidagathis is necessary. Species of Lepidagathis are found in three clades: (A) Lepidagathis s.str., (B) Lophostachys s.l., and (C) Teliostachya , each of which can be distinguished by inflorescence and stamen characters. The phylogenetic relationships recovered here indicate that each of the three clades should be classified as a separate genus. This research lays the groundwork for future taxonomic revisionary work as well as the construction of updated identification keys that will aid in conservation efforts and provide insight into the evolutionary processes that shape biodiversity in this remarkable lineage.