Radchenko A.G., Perkovsky E.E. 2021. Wheeler’s dilemma revisited: first Oecophylla–Lasius syninclusion and other ants syninclusions in the Bitterfeld amber (late Eocene) // Invertebrate Zoology. Vol.18. No.1: 47–65 [in English].
ABSTRACT. The first syninclusions of extant tropical and Holarctic ant genera are reported from Bitterfeld amber: the tropical Oecophylla F. Smith (O. brischkei Mayr, 1868) with the Holarctic genus Lasius F. (four workers of L. schiefferdeckeri Mayr, 1868), and others. The ratio of tropical and Holarctic ants in Bitterfeld, Baltic, Rovno and Danish ambers is analyzed; Holarctic ants dominate in all ambers, consistent with late Eocene climate. Oecophylla, Lasius and the temperate extant Palaearctic caddisfly genus Beraeodes Eaton are dominant as compression fossils in the terminal Eocene Bembridge Marls, UK. Syninclusions of Oecophylla with Lasius, as well as syninclusions of Beraeodes with Yantaromyrmex Dlussky et Dubovikoff, 2013 in Rovno amber, are consistent with an equable climate of the late Eocene amber forests of Europe. The cooccurrence of Oecophylla, Lasius and Beraeodes at the terminal Eocene in the Bembridge Marls supports a late Eocene age of European ambers. The coexistence of Oecophylla and Lasius in Europe was possible only from the late Eocene to the late Miocene: until the late Eocene, the climate in European middle latitudes was too hot for aphids, the obligate symbionts of Lasius, but after the late Miocene it became too cold for Oecophylla. The dominance of Oecophylla in the periodically flooded terminal Eocene Bembridge environment might be explained by its arboreal lifestyle providing a competitive advantage over terrestrial Formica species, for which nesting places were quite limited under these conditions.
KEY WORDS: age of Baltic amber, Priabonian, paleoclimate, Europe, palaeontology, Bembridge, Formica, Beraeodes.