The last Pleistocene glaciation, gaps in the bird areas of Eastern Siberia and their role in increasing the species diversity of its territory during periods of sharp climate warming

Abstract

Based on many years of work (1968-2022) and the analysis of special literature, the main features of the modern avifauna of Eastern Siberia and its relationship with Pleistocene glaciations and the climate of the previous epoch are shown. The eastern regions of Russia and the adjacent more southern large mountain systems were characterized by mountain-valley glaciations in the Pleistocene. As a result, up to the Himalayas, the continuous ranges of birds of this period were torn into two parts, and, taking into account the very complex terrain of the territory, into a larger number of isolates. Gaps in bird ranges caused intensive speciation and, in comparison with the previous period, to the formation of increased diversity. Modern climate warming, especially pronounced in Eastern Siberia, has led to the intensive movement of birds to the north, as well as the formation of western and eastern bird settlement flows. As a result, the total diversity of the species composition of birds in Eastern Siberia increased by 116 species (23.6% of the original diversity). The basis of the new species are birds whose habitats were torn apart during the last Pleistocene glaciation. After the discontinuities of the ranges, the tendency to the formation of new species is clearly visible in forest and mountain bird species. In waterfowl and waterfowl, they often did not lead to the formation of new species. This is due to the fact that coastal birds often had a common range far in the south of Asia, where the overall climate cooling was the least. Currently, some species have already formed extensive zones of intergradation of the habitats of closely related species, and many have a clear general trend towards the development of this process. Consequently, mountain-valley glaciers dramatically increased the diversity and isolation of habitats and increased the intensity of speciation of birds based on new geographical isolates. Undoubtedly, prolonged cooling and warming of the climate in a complex and diverse geographical environment are environmental factors of the evolutionary process.