Phylogeny of North American Aphaenogaster species (Hymenoptera: Formicidae) reconstructed with morphological and DNA data

Twenty-two Aphaenogaster species (Hymenoptera: Formicidae) occur in North America. While morphology and ecology define most species, the species limits of a group in the Eastern United States are unclear.  In particular, the morphological and behavioral characters once thought to define A. carolinensis, A. picea and A. rudis do not associate with their hypothesized species limits.  These observations suggest that these species are not monophyletic.  We therefore tested the monophyly of Aphaenogaster in the context of molecular phylogenetic analyses. We used DNA data from five genes: CO1, CAD, EF1-alpha F2, Long-wavelength Rhodopsin and Wingless to reconstruct phylogenies for 44 Aphaenogaster and outgroup species. In the resulting trees, reconstructed using parsimony and Bayesian inference, species boundaries associate with well- supported monophyletic clades of individuals collected from multiple locations.  For example, A. carolinensis was monophyletic and a missing CAD intron was a diagnostic trait for the clade. However, some clades were unresolved, and A. picea and A. rudis were not monophyletic. Given the short branch lengths, these results suggest that these ants have likely recently radiated and lack of sorting of gene lineages explains the non-monophyly of species. Conversely, these results may indicate that the clades of multiple species represent fewer but morphologically varied species. Additional biological information concerning pre- and post- mating barriers is needed before a complete revision of species boundaries for Aphaenogaster.