Molecular Phylogeny of Axonopus (Poaceae, Panicoideae, Paspaleae): Monophyly, Synapomorphies, and Taxonomic Implications for Infrageneric Classification and Species Complexes

Abstract

Axonopus P. Beauv. comprises nearly 90, mostly New World, species characterized by having spikelets with the inverse position (i.e., the backs of the upper glume and the upper lemma turned away from the rachis). The genus has been divided into four sections, five series, and three subseries, based exclusively on morphological features. Previous phylogenetic analyses based on a limited sampling of species showed Axonopus to be a monophyletic genus. In this study we increased the number of species sampled (46 species in the combined tree) and sequenced four DNA regions (external transcribed spacer [ETS], internal transcribed spacer [ITS], trnL-F, and ndhF). We tested the monophyly of Axonopus and its traditional infrageneric categories using parsimony, likelihood, and Bayesian inference. Additionally, we performed ancestral character state reconstructions of 45 morphological characters to infer autapomorphies of the species and synapomorphies for the genus and clades. Our findings confirmed Axonopus as a monophyletic genus only when Centrochloa Swallen and Ophiochloa Filg., Davidse & Zuloaga are included within it. Our analyses also showed that, with the exception of section Lappagopsis, infrageneric categories from previous classifications of the genus are artificial. Twenty-one morphological character states were identified as potential autapomorphies; two were reconstructed as potential synapomorphies for Axonopus, whereas 12 were reconstructed as potential synapomorphies for specific clades within the genus. Further molecular analyses, including sequencing of unlinked nuclear genes, are needed in order to reach a robust phylogenetic classification of the genus.

Phylogenetic Relationships in the Group Caespitosa of Paspalum L. (Poaceae, Panicoideae, Paspaleae)

“…We also built a new cpDNA matrix for this study [trnH-psbA (coding region, spacer, IR-B/LSC junction), encompassing the rps19 gene [33,34] including 38 accessions, totaling 81 new sequences added. In addition, nine species belonging to eight closely related genera were selected as outgroups, based on [21,[35][36][37]: Anthaenantia P. Beauv., Axonopus P.…”

A taxonomic revision of axonopus p. Beauv. (poaceae: panicoideae) in india

“…The monophyly of Axonopus is strongly recommended by López and Morrone (2012) and Delfini et al (2020). They advocated inclusion of Centrochloa Swallen and Ophiochloa Filg., Davidse & Zuloaga within the generic circumscription of Axonopus, supported by both morphological and molecular evidences.…”

Nomenclatural updates on names linked to the genus Axonopus for the Brazilian flora (Poaceae, Panicoideae, Paspaleae)

“…is one of richest genera within Paspaleae (Morrone et al 2012), comprising around 90 species (Zuloaga et al 2003;. Most of them are native to the Americas, mainly distributed in tropical and subtropical regions, with a few introduced in the Old World (Black 1963;Giraldo-Cañas 2008;Delfini et al 2020;BFG 2021). Axonopus is an economically important grass genus as it includes numerous species used as forage (e.g., Axonopus fissifolius (Raddi) Kuhlm., A. obtusifolius (Raddi) Chase, A. purpusii (Mez) Chase, A. scoparius (Flüggé) Kuhlm., A. suffultus (Mikan ex Trin.)…”

“…Axonopus have been considered a taxonomically complex group mainly due to its large number of species and the difficulty of establishing clear limits between many of them (Black 1963;Delfini et al 2020). The only revision of the entire genus was made by Black (1963) but, important advances have been done in recent years to clarify its taxonomic and phylogenetic relationships (i.e., López & Morrone 2012;Delfini et al 2020Delfini et al , 2022.…”

“…This article is part of a broader proposal that includes phylogenetic and taxonomic studies for Axonopus species, focusing on the Brazilian flora (Delfini et al 2020(Delfini et al , 2022. We aim here to contribute to the stabilization of nomenclature for 20 names that will appear in the project Flora e Funga do Brasil and also, before long, in the Flora Neotropica for the genus; thus, we designated lectotypes for nine names (i.e., Axonopus argentinus var.…”