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Abstract Many insect groups have acquired obligate microbial symbionts, and the resulting associations can have important ecological and evolutionary consequences. A notable example among ants is the species‐rich tribe Camponotini, whose members derive nutritional benefits from a vertically inherited bacterial endosymbiont,Blochmannia. We generate ultraconserved element (UCE) phylogenomic data for 220 ingroup and 5 outgroup taxa to reconstruct a detailed evolutionary history of the Camponotini, including the inference of divergence times and dispersal events. Under multiple modes of analysis, including both concatenation and species‐tree approaches, we recover a well‐supported backbone phylogeny comprising eight lineages: three large genera (Camponotus,Colobopsis,Polyrhachis) and several smaller genera or clusters of genera. Three novel lineages are uncovered that cannot be placed in any existing genus:Lathidrisgen. n., from the mountains of Mesoamerica;Retalimyrmagen. n., from the Indian Himalayas; andUwarigen. n., from eastern Asia. The species in these new genera were described and placed erroneously inCamponotus. The tribe Camponotini is estimated to have a crown origin in the Eocene (median age 38.4 Ma), with successively younger crown ages forColobopsis(22.5 Ma),Camponotus(18.6 Ma) andPolyrhachis(18.5 Ma). We infer an Australasian or Indomalayan origin for the tribe, with multiple dispersal events to the Afrotropics, Palearctic region, and New World. Phylogenetic analysis of selectedBlochmanniagenes from a subset of 97 camponotine taxa yields results that are largely congruent with the ant host phylogeny, at least for well‐supported nodes, but we find evidence thatBlochmanniafrom some old lineages—especiallyLathidris—may have discordant histories, suggesting possible lability of this symbiosis in the early evolution of camponotine ants. 

Abstract We investigate the species-level taxonomy and evolutionary history of Nearctic ants in the Crematogaster scutellaris group (Hymenoptera: Formicidae), drawing on evidence from morphology and UCE (ultraconserved element) phylogenomics. The New World species in this group form a well-supported clade that originated in the Late Miocene (~7.3 Mya) and subsequently diverged into three major lineages: the C. coarctata clade (south-western Nearctic), the C. opaca clade (south-western Nearctic and northern Neotropics) and the C. lineolata clade (eastern Nearctic and Caribbean, with four isolated south-west endemics). We hypothesize trans-Beringian dispersal into the New World, west-to-east movement within North America and restriction of mesophilic species to the east with increasing aridification of the west. The ancestral nesting behaviour of these ants is inferred to be ground-dwelling, and this is still the predominant condition in the arid west, whereas most species in the eastern United States are arboreal. We resurrect from synonymy nine species and describe three new species: C. detecta sp. nov. (from Nevada), C. parapilosa sp. nov. (Florida) and C. vetusta sp. nov. (Arizona). We provide a worker-based key to the 34 species of Crematogaster occurring in America north of Mexico, but emphasize that there are still ongoing taxonomic issues that need to be resolved.