Taxonomy, phylogeny and biogeography of seed-harvesting ants in the Tetramorium solidum-group (Hymenoptera:Formicidae)

Ants emerged during the Cretaceous Period more than 100 million years ago (Grimaldi & Engel 2005; Perrichot et al. 2008) and diversified independently on different landmasses following the Early Cretaceous fragmentation of Pangaea (Grimaldi & Agosti 2000). Today, ants represent one of the most ecologically successful groups globally (Wilson 1987), and their diversity far exceeds that of other social insects (Hölldobler & Wilson 1990). Currently 21 subfamilies, 305 genera and 12465 recorded ant species exist (Bolton 2012). Ants occur in almost all terrestrial habitats (Brown 2000) and are not uniformly distributed across regions, biomes and continents. As with all other taxa, historical abiotic factors have played a major role in their diversification and biogeographic structure (Tolley et al. 2006), including climatic changes (Holldobler & Wilson 1990) and the necessity to adapt to new environmental conditions (Tolley et al. 2006). Many global areas still lack data on regional biodiversity and the historical processes that may have shaped it. This is particularly so for southern Africa where the ant fauna is still relatively poorly known (Robertson 2000) and where there have been no published biogeographic analyses for any ant taxon.