Towards a Monophyletic Infrageneric Circumscription of Adesmia DC. (Dalbergieae, Leguminosae): a Taxonomic Revision in Adesmia series Adesmia

Abstract

The Adesmia clade comprises five genera, with Adesmia being the most diverse and speciose, and formerly containing 206 species and 37 varieties, distributed in two subgenera and 43 series. The genus inhabits almost exclusively the South American Arid Diagonal, which hosts some of the driest environments on Earth. Within Adesmia subgenus Adesmia, three series primarily inhabit the Pampa grasslands: series Muricatae, Bicolores, and Subnudae. These taxonomically complex series display overlapping morphological characters and geographical distribution ranges, and their monophyly has never been tested. We carried out a thorough systematic study of the three series, combining Maximum Likelihood and Bayesian analyses of 87 sequences of nrITS DNA of Adesmia. Beased on our phylogenetic results, we provide a taxonomic revision of the species in series Muricatae, Bicolores, and Subnudae. Series Subnudae and Bicolores are nested within series Muricatae, and synonymization of the first two under series Muricatae is here proposed. Three clades containing species with geographical and morphological coherence were unraveled inside Adesmia. Three varieties are elevated to species level, and another six were reduced to synonyms. Seven lectotypes and one neotype are proposed. We recognize 21 species in the new circumscription of Adesmia series Muricatae, and provide a species identification key, descriptions, illustrations, and maps, as well as comments on phenology, taxonomy, etymology, distribution, and habitat. We also present conservation assessments for the species of the series.