The origins and rise of the ants revealed in amber

Vincent Perrichot (1)

1 GR - Géosciences Rennes

Ants have roamed the Earth for at least 100 million years and are present in nearly all terrestrial ecosystems today. The vast majority of over 13,000 extant and 700 extinct species of ants described to date belongs in the "big four" subfamilies Dolichoderinae, Formicinae, Myrmicinae, and Ponerinae. However, the rise of the modern lineages has been relatively slow, and ants appear to have been only moderately abundant and diverse for about the first half of their history. This long history 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 groups that did not survive beyond the Cretaceous-Cenozoic boundary despite various ecological adaptations. In Early Eocene amber, prevalence increases up to 10%, and all identifiable ants are assignable to crown lineages. Also, dominance of the "big fou~· subfamilies is already largely consistent into the Eocene, during which a tremendous burst of diversification evidently occurred. In Miocene amber, ant prevalence reaches 25-36% and virtually all specimens are assignable to extant genera. A midpoint in the history of ants is thus reached in the Early Eocene, - 50-55 million years ago, with a distinct shift observed in their abundance and diversity. Finally, almost all modem genera had appeared by the middle Miocene, -15 Ma, and major changes since then mostly comprised their geographical diversification. 4

Domaines: Paléontologie

Vincent Perrichot. The origins and rise of the ants revealed in amber. XXIII Simpósio de Mirmecologia: An International Ant Meeting, Oct 2017, Curitiba, Brazil. pp.4. ⟨insu-01715190⟩