Phylogenomics and biogeography of the New World ant genus Dorymyrmex (Hymenoptera: Formicidae)

The ant genus Dorymyrmex (Hymenoptera: Formicidae: Dolichoderinae) is a common sight in most open habitats in the Americas. With their conspicuous crater nests and daytime foraging habits, they have been frequently collected by entomologists, but the superficially similar appearance of Dorymyrmex species has hindered taxonomic efforts. By revisiting this challenging group in the context of modern molecular genetics, it is possible to uncover the evolutionary history of major lineages and relationships between species. The following work comprises three studies of Dorymyrmex evolution that utilize targeted genomics of ultraconserved elements (UCEs). Chapter I is the first phylogenetic assessment of Dorymyrmex, which outlines a historical overview of the higher taxonomy, establishes species relationships for the major lineages, and describes the opportunities and challenges in Dorymyrmex systematic research. Dorymyrmex is found to comprise three species groups that align with some former [sub]generic boundaries, and to have originated in southern South America. Chapter II is a detailed phylogenetic and biogeographic study of Dorymyrmex ants from across their entire range. By sequencing 185 taxa, inferring phylogenies, and performing divergence dating and biogeographic analyses, it is revealed that Dorymyrmex comprises not three, but four species groups, and the "amphitropical" distribution of the genus (i.e., north and south of the tropics) was largely started by a single dispersal event from South America to North America via the Isthmus of Panama. This journey occurred before the completion of the land bridge, indicating some overwater dispersal by flight and/or an earlier, complex origin of the isthmus; accordingly, the discussion draws on characteristics of Dorymyrmex life history and nesting habits that have contributed to the success of the genus in colonizing new habitats. Finally, Chapter III is a phylogenetic exploration of Dorymyrmex diversity in the taxonomically chaotic Nearctic clade, in which species are newly delimited by morphology in light of genetically independent lineages. The number of species known from the continental US is increased from 14 to 27, a provisional identification key is presented for Dorymyrmex species of the entire Nearctic clade, and each of these provisional species is given a characterization, diagnosis, and discussion, illustrated by 54 figures. The formal taxonomic revision Dorymyrmex needs is quite extensive, but this resolution—which is now within sight—will inform a variety of studies in behavior, sensory morphology, social parasitism, community ecology, and even agricultural pest management. Although these ants are a familiar sight in North and South America, they have until now been known to myrmecologists "mainly as a taxonomic headache"; the present work signifies a tremendous improvement in our knowledge