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Abstract The ant genus Tapinoma Foerster, 1850 is a moderately diverse group (81 valid species) that occurs worldwide. It includes the tramp species T. melanocephalum, whose evolutionary history, biogeographic origin, and population limits remain unclear. Here, we present a time-calibrated phylogeny and a biogeographic history inference of the genus based on thousands of Ultraconserved Element (UCE) loci. Focusing on T. melanocephalum, we used single nucleotide polymorphisms from UCE loci and COI sequences to analyze species boundaries based on nuclear and mitochondrial DNA. We recovered a monophyletic Tapinoma with an estimated crown age corresponding to middle Eocene (49.4 to 34.4 Ma). Phylogenomic data differentiated T. melanocephalum from T. jandai, a recently established species based on morphology, and revealed that the 2 species diverged ∼12 Ma. Population genetic analyses identified considerable molecular divergence among sampled T. melanocephalum populations, and a heterogeneous genetic structure, showing a weak relationship between genetic differentiation and geographic distance. A phylogeographic comparison of habitat preferences of T. melanocephalum revealed an ecological shift from undisturbed to urban environments, a phenomenon which may have facilitated its ubiquitous and global distribution. Our study presents the first phylogenomic framework for this globally distributed ant genus and molecularly delineates a worldwide pest ant species. 

Abstract The classification of ants (Hymenoptera: Formicidae) has progressed in waves since the first 17 species were described by Linnaeus in the 1758 edition of Systema Naturae. Since then, over 18,000 species-rank names have accumulated for the global myrmecofauna, of which ~14,260 living and ~810 fossil species are valid. Here, we provide a synopsis of ant biodiversity and review the history and classification of the family, while highlighting the massive growth of the field in the new millennium. We observe that major transformation has occurred for ant classification due to advances in DNA sequencing technologies, model-based hypothesis testing, and imaging technologies. We therefore provide a revised and illustrated list of diagnostic character states for the higher clades of Formicidae, recognizing that vastly more work is to be done. To facilitate discussion and the systematic accumulation of evolutionary knowledge for the early evolution of the ants, we suggest an informal nomenclatural system for the higher clades of ants, based on names currently in use and a set of names that have been democratically selected by the authors. To guide future work on ant systematics, we summarize currently available databases and present perspectives on regions in need of biodiversity exploration, challenges facing the field, and the future of ant taxonomy. 

Evolutionary innovations underlie the rise of diversity and complexity—the 2 long-term trends in the history of life. How does natural selection redesign multiple interacting parts to achieve a new emergent function? We investigated the evolution of a biomechanical innovation, the latch-spring mechanism of trap-jaw ants, to address 2 outstanding evolutionary problems: how form and function change in a system during the evolution of new complex traits, and whether such innovations and the diversity they beget are repeatable in time and space. Using a new phylogenetic reconstruction of 470 species, and X-ray microtomography and high-speed videography of representative taxa, we found the trap-jaw mechanism evolved independently 7 to 10 times in a single ant genus ( Strumigenys ), resulting in the repeated evolution of diverse forms on different continents. The trap mechanism facilitates a 6 to 7 order of magnitude greater mandible acceleration relative to simpler ancestors, currently the fastest recorded acceleration of a resettable animal movement. We found that most morphological diversification occurred after evolution of latch-spring mechanisms, which evolved via minor realignments of mouthpart structures. This finding, whereby incremental changes in form lead to a change of function, followed by large morphological reorganization around the new function, provides a model for understanding the evolution of complex biomechanical traits, as well as insights into why such innovations often happen repeatedly.