Abstract

The post-Miocene climatic history of arid environments in South America has been identified as a key driver of dispersal and diversification, particularly among plant groups such as Cactaceae. Despite their iconic status, many cactus genera remain poorly understood, and comprehensive taxonomic and systematic revisions using morphological and genomic data are complex and time-consuming, resulting in few such studies to date. Here we present a comprehensive systematic study of the genus Austrocactus, currently with 10 accepted species native to southern and Andean Argentina and parts of Chile. The study is based on an extensive sampling covering both the overall range and the morphological diversity of the genus. We used a ddRADseq approach to study phylogenetic relationships incorporating 44 individuals representing all morphospecies, and widespread species are represented by several samples covering their morphological and geographical spectrum. The data were analyzed using maximum likelihood and multispecies coalescence-based models, as well as principal component analyses, providing a well-supported and robust evolutionary framework. Based on phylogenetic and morphological data, we propose a revised classification of the genus, with a total of 17 species, 5 of which are described as new. We also provide an updated infrageneric classification with two subgenera and three sections, and a revised circumscription of the genus, including descriptions of all species, as well as a respective key. Finally, we suggest specific research directions focused on integrating genomic data with ecological modeling to complement our work and enhance the biogeographic understanding of these species. © 2025 The Author(s). TAXON published by John Wiley & Sons Ltd on behalf of International Association for Plant Taxonomy.