Molecular data, geographic disjunction and morphological divergence support species-level recognition of Oxalis hyalotricha subsp. borealis

Abstract The widespread use of morphologically based subspecies in plants can obscure our understanding of biodiversity and hinder conservation strategies. In the genus Oxalis, some subspecies were created to encompass morphologically similar but geographically disjunct entities, as is the case of Oxalis hyalotricha subsp. borealis. Due to the substantial geographic distance between this subspecies and the typical form, combined with divergent habitats and morphological differences that exceed those originally described, we conducted an integrative taxonomic study, in order to verify the taxonomic circumscription between them. Phylogenetic analyses using the molecular markers ITS, trnL-trnF, and petA-psbJ indicate that O. hyalotricha is paraphyletic and that O. diamantinae may be the closest relative of O. hyalotricha subsp. borealis. Together with morphological and anatomical distinctions and the maintenance of geographic disjunction associated with ecological divergence, these findings support the recognition of O. hyalotricha subsp. borealis as a distinct species within Oxalis sect. Thamnoxys. We present updated taxonomic treatments for each of the newly recognized species and assessed O. borealis as Endangered following the International Union for Conservation of Nature (IUCN) categories and criteria, warranting attention from conservation authorities.