Fine tuning the circumscription of Fridericia (Bignonieae, Bignoniaceae)

Abstract

AbstractThe plant family Bignoniaceae has a complicated history of supra‐specific level systematics. In the past decade, molecular phylogenetic studies have contributed substantially to an improved circumscription of clades at all taxonomic levels, especially at the generic and tribal levels. For instance, a molecular phylogeny of the tribe Bignonieae reconstructed a polyphyletic Arrabidaea, and proposed a new circumscription for members of the Arrabidaea & Allies clade. Within this new classification, most species previously included in Arrabidaea were distributed among four genera: Cuspidaria (19 spp.), Fridericia (67 spp.), Tanaecium (17 spp.), and Xylophragma (7 spp.). The taxonomy of Fridericia, the genus that received most species of Arrabidaea, remains complicated due to the high morphological variability and broad distribution of its species. Here, we used molecular data and a broad sampling of taxa within the Arrabidaea & Allies clade to reconstruct the phylogeny of Fridericia. We then studied the morphology of all species of Fridericia and identified morphological synapomorphies that characterize major clades that represent meaningful units for future taxonomic studies. Most genera included in the Arrabidaea & Allies clade were retrieved as monophyletic; however, two species of Fridericia were reconstructed within Cuspidaria, while three species of Fridericia were placed within Tanaecium. The molecular phylogenetic placements received additional support from morphology, and the necessary taxonomic changes are proposed. We combine three species of Fridericia into Tanaecium (T. dichotomum comb. nov., T. paradoxum comb. nov., T. parviflorum comb. nov.), two species into Xylophragma (X. claussenii comb. nov., X. corchoroides comb. nov.), two species into Cuspidaria (C. bracteolata comb. nov., C. monophylla comb. nov.), and one species of Adenocalymma into Fridericia (F. trichoclada comb. nov.). We also synonymize Fridericia whitei into Cuspidaria pulchra. We present a key for the seven main clades identified within the genus, as well as a detailed morphological description for Fridericia and its major lineages.