UCE phylogenomics illuminates remarkable species diversity and clarifies classical taxonomy in arid-adapted ants (Formicidae: Dolichoderinae: Dorymyrmex)

The systematics and classification of Dorymyrmex ants have had a tumultuous past. Over the centuries, the genus has been subdivided into as many as seven genera and subgenera, and Dorymyrmex insanus­—an appropriate epithet—was once dubbed as having 'the most singularly unfortunate taxonomic history of any North American ant.' To untangle this longstanding taxonomic puzzle, I took an integrative approach that combines phylogenomics with classical morphological methods. I sequenced partial genomes of Dorymyrmex from across the Americas by targeting ultra-conserved elements (UCEs), inferred ML and Bayesian phylogenies, estimated divergence dates, and reconstructed hypothesized ancestral areas. Additionally, I supplemented the molecular analyses with a morphometric dataset of 24 measurements and 22 indices for 148 specimens, totaling 6,808 individual observations. The results indicate that 1) Dorymyrmex comprises four distinctive species groups; 2) the genus originated in South America and expanded its range into North America before the completion of the land bridge; and 3) the rapidly radiating Nearctic clade contains double the number of species previously recognized. In sum, this work clarifies many previous taxonomic difficulties, uncovers exciting species diversity across the United States, and paves the way for a thorough revision that is long overdue.