Advances in systematics of Mimosa (Fabaceae): phylogeny and biogeography of the Petiolovariabilis clade

Abstract

This study analyses the phylogeny of the clade Petiolovariabilis, proposed herein, within the genus Mimosa. This clade comprises 26 species (31 taxa), predominantly cespitose, decumbent and procumbent herbs or subshrubs, but also includes climbing armed and erect shrubs. These species are primarily distributed in the Brazilian highlands and the basins of São Francisco, Paraná, and Tocantins rivers. Phylogenetic analyses were based on six loci (both plastidial and nuclear), focusing on taxa from M. sect. Batocaulon ser. Campicolae, Echinocaulae, Filipedes, and Paucifoliatae. Within the Petiolovariabilis clade, relationships were resolved, and three child clades were described following PhyloCode guidelines. This research emphasizes informative traits such as seed pleurogram and flower merosity, alongside other important vegetative characters in a taxonomic context, such as prickles, petiole morphology, and leaf pinnae/leaflet numbers. Ancestral area reconstructions for major lineages integrating phylogenetic and curated geographic data, shed light on dispersal and speciation events within the Petiolovariabilis clade. The study also addresses taxonomic challenges related to distinguishing taxa within the current infrageneric classification of Mimosa. Overall, this research enhances our understanding on the evolutionary history of Mimosa and provides valuable insights for future studies.