Taxonomy of African driver ants west of the Dahomey Gap

Driver ants (Dorylus nigricans species group) are keystone species in forest and savanna ecosystems across tropical Africa. However, their study has been hampered by considerable taxonomic confusion. A multitude of worker forms has been described under the name Dorylus nigricans Illiger, 1802, even though the link between the name-bearing type specimens, two males from Sierra Leone, and the respective conspecific workers has never been established. Extensive surveys of driver ants were first conducted at numerous West African sites from Senegal to Ghana. These yielded a total of only three species recognisable by morphological differences. We then examined the two D. nigricans syntypes and found that they belong to different species. By analysing mitochondrial and nuclear DNA sequences of males and workers from Taï National Park (Ivory Coast), males with a phenotype similar to that of the larger syntype specimen were matched to workers originally described under the name Anomma arcens by Westwood (1847). This larger syntype male is designated as the lectotype of D. nigricans Illiger, 1802, so that Anomma arcens Westwood, 1847 is synonymised under D. nigricans. A worker neotype for the species originally described as Anomma burmeisteri Shuckard, 1840, whose type specimen was lost, is designated. A key to the large workers of the three driver ant species occurring in this region, D. burmeisteri, D. nigricans, and D. mayri, is provided. By clarifying the taxonomy of the regional driver ant fauna, we resolve a centuries-old puzzle and pave the way for a comprehensive revision of the entire species group.