The rise of the ants revealed in amber

Vincent Perrichot (1)

1 GR - Géosciences Rennes

Ants are a conspicuous element of modern terrestrial ecosystems, are distributed virtually worldwide, and have an expansive range of behaviors and interactions with other organisms. The vast majority of over 13,000 extant species belongs in the "big four" subfamilies Dolichoderinae, Formicinae, Myrmicinae, and Ponerinae. However, despite the presence of ants on Earth for over 100 million years, their rise to dominance has been relatively slow, and they appear to have been only moderately abundant and diverse for about the first half of their history. This is well documented in the fossil record and a focus is made here on fossils entombed in amber, as they harbor the finest preservation and offer a tantalizing glimpse of ant diversity at various points in the past. Ants never surpass 1.5% of the total insects in Cretaceous amber deposits, where they mostly comprise stem-group ants that did not survive beyond the Cretaceous-Cenozoic boundary. In Early Eocene amber, prevalence increases up to 10%, and all identifiable ants are assignable to crown lineages. Also, dominance of the "big four" subfamilies is already largely consistent into the Eocene, during which a burst of diversification evidently occurred. In Miocene amber, ant prevalencereaches 25-36% and all specimens are assignable to extant genera. A temporal midpoint in the history of ants is thus reached in the Early Eocene, - 50 million years ago, with a distinct shift observed in their abundance and diversity. Finally, all modern lineages had appeared by the middle Miocene, -15 Ma, and major changes since then mostly comprise their geographical diversification.

Domaines: Paléontologie

Vincent Perrichot. The rise of the ants revealed in amber. Amber-Workshop, German Entomology Congress 2017, Mar 2017, Freising, Germany. pp.59. ⟨insu-01715203⟩