A Phylogenetic Analysis of Loasaceae Subfamily Loasoideae Based on Plastid DNA Sequences

Abstract

Questions of tribal and generic circumscriptions and relationships in Loasaceae subfamily Loasoideae are addressed in phylogenetic analyses that apply four plastid regions in parsimony and maximum likelihood analyses. As circumscribed in the influential monograph of Urban and Gilg, Loaseae are paraphyletic to the sister clades Klaprothieae (Klaprothia, Plakothira, and Xylopodia) and Kissenieae (Kissenia). This problem centers on the paraphyly of Huidobria: Huidobria chilensis is sister to $$\mathrm{Klaprothieae}\,+\mathrm{Kissenieae}\,$$ , and Huidobria fruticosa is sister to all other Loasoideae. Parametric bootstrapping finds topologies that force the monophyly of Huidobria to be significantly different from the optimal topologies in which the genus is paraphyletic; however, Templeton and Shimodaira‐Hasegawa tests did not distinguish between these phylogenetic alternatives. We recognize a strongly supported Loaseae sensu stricto (s.str.) as a clade consisting of Nasa, Aosa, Chichicaste, Presliophytum, Blumenbachia, Cajophora, Loasa sect. Loasa, and Scyphanthus. In Loaseae s.str., the monophyly of each of the following has strong support: (1) Nasa, (2) $$Aosa+Chichicaste$$ , (3) $$Presliophytum+Loasa\,malesherbioides$$ , and (4) a higher Loaseae clade that consists of Blumenbachia, Cajophora, Scyphanthus, and the Loasa complex (=sect. Loasa, excluding L. malesherbioides). Blumenbachia, Cajophora (including exemplars from sections Bialatae and Bicallosae), and Scyphanthus are independently monophyletic, and clades of the Loasa complex are mixed among them. The paraphyletic Loasa complex includes the following clades: (1) ser. Pinnatae, (2) ser. $$Acaules+Volubile$$ , (3) ser. Macrospermae, placed as the sister of Blumenbachia, and (4) ser. $$Acanthifolia+Floribundae+Deserticolae$$ , which includes the type for Loasa and is the group we recommend as the basis for a revised circumscription of Loasa.