Invasion biology of Ponto-Caspian onychopod cladocerans (Crustacea: Cladocera: Onychopoda)

We review the patterns of recent range expansions and the biology of the invasive Ponto-Caspian predatory onychopod cladocerans: Cercopagis pengoi, Evadne anonyx, Podonevadne trigona, Cornigerius maeoticus and Cornigerius bicornis. Recent invasions of C. pengoi, E. anonyx and C. maeoticus into the Baltic Sea can be attributed to the climate change, facilitating invasibility of the eastern Baltic Sea coastal ecosystems by the warm water Ponto-Caspian species and intensive shipping activities via the Volga-Baltic waterway (European “northern invasion corridor”). All three species can be considered to be established in pelagic communities of the eastern Gulf of Finland. Only one onychopod species, C. pengoi has invaded the North American Great Lakes via an existing invasion corridor between the eastern Baltic and the Great Lakes. Invasive onychopods may possess adaptive life cycles, switching to early gamogenetic reproduction which enables their establishment in recipient ecosystems and further dispersal. Analysis of temperature and salinity ranges of the Ponto-Caspian onychopod species in native and invaded habitats, indicates that they are potentially able to form populations in a wide range of inland and coastal water ecosystems in temperate zones. Ponto-Caspian onychopods can be considered as “high risk” invasive species, in terms of their potential for range expansion and impact on recipient ecosystems.