First record of insects from the oldest and older Dryas of Altai (Russia). Coleoptera assemblages from Lebed River

Abstract

Subfossil remains of insects found in the Lebed site (52.25220°N, 87.15692°E) located on the Lebed River, Altai Republic are recorded. The calibrated radiocarbon dates for two layers of these deposits were 16,461–17,056 cal BP, and 13,520–14,077 cal BP, which correspond to the oldest and older Dryas (Late Pleistocene). Insect assemblages of these deposits are mainly represented by Coleoptera, which are noteworthy there for high taxonomic and ecological diversity and include several endemic and relic species. At least 120 beetle species from 17 families have been found altogether, of them, 37 species are recorded for the Pleistocene deposits of Western Siberia for the first time. Three families, Carabidae, Staphylinidae and Curculionidae are most abundantly represented in the examined Lebed site. Ecologically, this beetle assemblage is dominated by species that are currently confined to the taiga belt and alpine meadows of the Altai Mountains; aquatic and near-water species are also well represented. The studied assemblages are rather different from the previously studied Pleistocene insect fauna in the south of the West Siberian Plain. The taxonomic and ecological compositions of the beetle fauna of Lebed site suggest its existence under humid palaeoclimate that was significantly colder than modern climate in this area.