UCE phylogenomics of New World Ponera Latreille (Hymenoptera: Formicidae) illuminates the origin and phylogeographic history of the endemic exotic ant P. exotica

The ant genus Ponera is a distinct lineage of leaf litter ants, with a center of diversity in the Indo-Australian region. Two described species are known to occur in the New World; however, uncertainty exists with regard to their biogeographic origins and species limits, especially for isolated cloud forest populations in Middle America. We investigate the geographic distribution, phylogeny, and phylogeography of these two species to better characterize the American ant fauna and to gain insight into the biogeography of taxa that span hemispheres. Sequencing of Ultra-Conserved Element (UCE) loci was used to infer phylogenetic relationships, estimate divergence dates, and test species boundaries. The widespread native species P. exotica and P. pennsylvanica are each more closely related to Old World relatives than they are to each other, implying two independent colonizations of the New World. Ponera pennsylvanica is most closely related to the European species P. coarctata, while P. exotica is related to a clade of Indo-Australian species. Ponera pennsylvanica is abundant throughout the eastern United States, with scattered occurrences as far west as Washington State. Ponera exotica occurs in the southern United States, as far west as western Texas, south to Nicaragua. Both species have alate and ergatoid queens. In Central America, P. exotica is restricted to cloud forest habitats, where it is moderately abundant. Sequenced specimens from multiple populations of P. exotica reveal a pectinate phylogeographic structure, from north to south, with the potential for multiple cryptic species. The southern USA to Middle America distribution pattern of P. exotica mirrors that of many plant and some animal species and may be the result of climatic cooling in the Pliocene followed by repeated glacial cycles in the Pleistocene, which condensed and fragmented mesic forest habitat. This scenario is supported by our divergence dating results, which give P. exotica a crown age of 3.1 Ma.