Review Article

Fossil ants (Hymenoptera: Formicidae): ancient diversity and the rise of modern lineages

Barden, P.

Abstract: The ant fossil record is summarized with special reference to the earliest ants, first occurrences of modern lineages, and the utility of paleontological data in reconstructing evolutionary history. During the Cretaceous, from approximately 100 to 78 million years ago, only two species are definitively assignable to extant subfamilies – all putative crown group ants from this period are discussed. Among the earliest ants known are unexpectedly diverse and highly social stemgroup lineages, however these stem ants do not persist into the Cenozoic. Following the Cretaceous-Paleogene boundary, all well preserved ants are assignable to crown Formicidae; the appearance of crown ants in the fossil record is summarized at the subfamilial and generic level. Generally, the taxonomic composition of Cenozoic ant fossil communities mirrors Recent ecosystems with the "big four" subfamilies Dolichoderinae, Formicinae, Myrmicinae, and Ponerinae comprising most faunal abundance. As reviewed by other authors, ants increase in abundance dramatically from the Eocene through the Miocene. Proximate drivers relating to the "rise of the ants" are discussed, as the majority of this increase is due to a handful of highly dominant species. In addition, instances of congruence and conflict with molecularbased divergence estimates are noted, and distinct "ghost" lineages are interpreted. The ant fossil record is a valuable resource comparable to other groups with extensive fossil species: There are approximately as many described fossil ant species as there are fossil dinosaurs. The incorporation of paleontological data into neontological inquiries can only seek to improve the accuracy and scale of generated hypotheses.