Molecular phylogeny of <i>Phyllanthus</i> L. sect. <i>Phyllanthus</i> (Phyllantheae: Phyllanthaceae) reveals the need for a reclassification of <i>Phyllanthus</i> subg. <i>Phyllanthus</i>

Abstract Phyllanthus L., with five subgenera, 25 sections, and ~220 species, is one of the largest genera of Phyllanthaceae in the Americas. Despite being monophyletic, phylogenetic sampling of a typical section (comprising ~40 species) considers only the type species of two of its three subsections. We used nuclear ribosomal DNA (ITS) and plastid DNA (trnL-trnF) sequences to reconstruct the evolutionary history of P. sect. Phyllanthus based on isolated and combined analyses of 28 sampled species through Bayesian and maximum likelihood methodologies. Our results revealed: (i) P. sect. Phyllanthus as polyphyletic, with its species emerging in five main clades (i.e. A, B, C, D, and E) mixed with the sections Antipodanthus, Choretropsis, and Loxopodium; (ii) P. subsect. Phyllanthus as paraphyletic; and (iii) P. subsect. Clausseniani as polyphyletic. Seeking to make the classification in P. subg. Phyllanthus monophyletic to the section level, we: (i) elevated the subsections previously circumscribed in the section Phyllanthus (clades C and D, and subclade A2) to the status of sections: P. sect. Almadenses (subclade A2), P. sect. Phyllanthus [clade C, 1 posterior probability (PP), and 100% bootstrap (BT)], and P. sect. Clausseniani (clade D, 1 PP, 100% BT); (ii) propose the establishment of P. sect. Subemarginatae (subclade A1, 1 PP, 100% BT) and P. sect. Glaziovii (subclade A3); (iii) recovered P. sect. Antipodanthus, P. sect. Choretropsis, and P. sect. Loxopodium as paraphyletic and made them monophyletic by reducing the circumscription of the former and expanding that of the latter two; and (iv) rediscovered P. niruri as a polyphyletic species, apparently due to its polyploid nature. This study provides the most extensive phylogenetic analysis of the section and contributes to the understanding of its evolutionary history.