First records of sub-fossil insects from Quaternary deposits in the southeastern part of West Siberia, Russia

Data are presented on species composition in Bun'kovo taphocoenosis at the Chik River, Novosibirsk, Russia (55°03′46″ N, 82°29′50″ E) with conventional radiocarbon dating ca 11,550 ± 125 ¹⁴C BP. The entomofauna complex is unique by species composition. 90 species of Coleoptera from 15 families, 4 species from 3 families of Hymenoptera (Pamphiliidae, Formicidae, Sphecidae) and pupae of Diptera are recorded. Amongst Coleoptera the most numerous is Curculionidae represented with 41 species, especially Otiorhynchus – 10 species and Stephanocleonus – 8 species, Carabidae – 21 species and Chrysomelidae – 7 species. Among the species recorded, Otiorhynchus karkaralensis (Curculionidae) predominates with 250 specimens present. 80% of the species are not known for this territory at the present time. Species typical of open landscapes such as boggy tundra, cold northern and warm southern steppes are included in the taphocoenosis. Forest species are rare, and humid thermophilic species are completely absent. The Bun'kovo taphocoenosis is closely related to entomofaunal complexes found in older deposits (28,000–24,000 BP) in central part of West Siberia and the Urals based on species composition, but differs in the abundance of Stephanocleonus. Similar-age taphocoenosis from central and northern parts of West Siberia are contrasted with Bun'kovo, highlighting the absence of xerophilic species. Based on the beetle species composition, cold and dry climate conditions (at least 4–5 C° cooler than present) and prevalence of dry tundra-steppe landscapes are re-constructed at Bun'kovo. This conclusion is reinforced by palynological data from nearby sites in the southern part of West Siberia. Analysis of modern distribution ranges of the species found in the taphocoenosis shows that species have shifted dramatically from the late Pleistocene to present time because of increasing warmth and humidity during the Holocene. The contemporary distributions include shifts to the north in meso-hygrophilous and mesophilous species, to the east or south in xerophilous species, and to northern, eastern or southern directions in hygrophilous species.