Relict occurrence of East Palaearctic dragonflies in northern European Russia, with first records of Coenagrion glaciale in Europe (Odonata: Coenagrionidae)

The East Palaearctic Coenagrion glaciale and C. hylas are characterized by a current disjunct distribution. New data from northern European Russia significantly modify the earlier known pattern of their distribution. The first European records of C. glaciale and a new record of C. hylas west of the Urals are reported from the environs of Pinega village (Arkhangelsk oblast, Pinega region). Distribution ranges of these two species are analysed in light of their palaeogeography. These postglacial relicts in Europe are representatives of a cold-stenothermal fauna that probably colonized the continent during the late Pleistocene and early Holocene in the period of the maximum spread of birch and pine. During the Atlantic period they withdrew far to the East remaining probably only as isolates in the Urals and in Europe. However, the new records suggest that the European remains of the early Holocene distribution may be more numerous and extensive than previously believed and are concentrated especially in the almost unexplored northeast. The survival of C. glaciale and C. hylas in the presumptive isolate of their distribution range in the Pinega region is probably a consequence of a specific combination of severe climate and habitat and microclimatic conditions, largely influenced by karst. The habitat conditions at Tinega' localities are analysed in the context of the species' requirements. Additionally, biogeographically important findings of the North and Central Asian Aeshna serrata are recorded. This species was previously assumed to occur in Europe only as an isolate around the Baltic Sea, but the new records suggest that it has a much more extensive but fragmented distribution in the European north and northeast.