Phylogenomics of the Crematogaster scutellaris group

The species-level taxonomy and phylogeny of the Nearctic members of the Crematogaster scutellaris group is examined, drawing on evidence from morphology and UCE (ultra-conserved element) phylogenomics. The C. scutellaris group occurs in the Palearctic, Nearctic, and northern Neotropical regions, and it accounts for most of the North American species of the genus. Our work was motivated by the need to correct serious errors in a recent revision of Nearctic Crematogaster. We generate a well-resolved molecular phylogeny that clarifies relationships among these ants. The New World members of the C. scutellaris group form a well supported clade to the exclusion of the Palearctic species. The following Nearctic species are resurrected from synonymy and newly diagnosed: C. browni Buren stat. rev., C. californica Wheeler stat. rev., C. cedrosensis Wheeler stat. rev., stat. nov., C. colei Buren stat. rev., C. hespera Buren stat. rev., C. larreae Buren stat. rev., C. marioni Buren stat. rev., C. opuntiae Buren stat. rev., and C. rossi Buren stat. rev. In addition, we refine the characterizations of C. cerasi (Fitch), C. depilis Wheeler, C. opaca Mayr, C. pilosa Emery, C. punctulata Emery, and C. vermiculata Emery, and we describe three new species: C. detecta sp. nov., from Nevada, C. parapilosa sp. nov., from Florida, and C. vetusta sp. nov., from Arizona. C. atkinsoni and C. atkinsoni helveola are shown to be synonyms (syn. nov.) of C. pilosa, while the species that has been called C. atkinsoni in recent literature corresponds to C. parapilosa sp. nov. C. opaca texana Santschi is considered to be a junior synonym of C. punctulata Emery (syn. rev.). We provide an illustrated worker-based key to the thirty-four species of Crematogaster occurring in America north of Mexico, but emphasize that there are still ongoing taxonomic issues that need to be resolved.