Advances in ant systematics: phylogenetics and species-level taxonomy

Ants are the world’s most successful group of social insects, occupying most terrestrial habitats and exerting a strong ecological influence in many communities. Ant systematics is concerned with (i) the discovery and delimitation of ant species, (ii) the evaluation of phylogenetic relationships among ant taxa, and (iii) the development of a classification system consistent with these findings. Spurred by advances in molecular phylogenetics, the last decade has seen striking progress in attempts to estimate the relationships among the major lineages of ants. We now have a coherent picture of the main features of ant evolution, from the origin of crown-group Formicidae in the early Cretaceous to the radiation of major subgroups (subfamilies) in the Paleogene. Many details of this history remain unclear, however, especially the phylogenetic positions of poneroid and leptanilline ants. More than 12,000 species of ants have been described to date, but the task of delimiting ant species is far from complete. The species-level taxonomy of ants would benefit from greater understanding of geographical variation within species and the processes that cause population divergence and speciation. A “population approach” to studying problems in ant biology, long championed by Hölldobler and Wilson, is particularly beneficial when applied to ant systematics.