Peculiarities of the biology of two Diaphanosoma species (Crustacea,Cladocera) in Rybinsk Reservoir

The spatial distribution, long-term dynamics of occurrence and abundance, and the peculiarities of the seasonal cycle of two cladocerans, an alien species Diaphanosoma orghidani Negrea and a native species D. brachyurum (Liévin), were studied in Rybinsk Reservoir in 2005–2011. The successful coexistence of the species for over a 7-year period was favored by the differences in their seasonal cycles, the distributional pattern in the reservoir, the predator press, and the preference of the alien species to inhabit areas of running water where the native species was not numerous. Competitive advantages of the invader under conditions of global warming are discussed.