Diversity, taxocenes and biogeographical patterns of planktonic crustaceans (Copepoda, Cladocera, Anostraca) of the continental Chukotka (northeastern Russia)

Microcrustaceans in the water bodies of Chukotka have been previously studied fragmentary.Our study aimed to make an inventory of the regional fauna and analyse the structure and distribution of planktonic crustacean taxocenes in the continental part of Chukotka Autonomous Okrug (Russian Federation).In samples collected from the northern coastal plain, as well as from the Anadyr and Koryak highlands, 15 species of Cladocera, 35 species of Copepoda and two species of Anostraca were identified.Four species of Cladocera: Daphnia magna, D. umbra, Chydorus cf.biovatus and Eurycercus cf.pompholygodes and seven species of Copepoda: Eurytemora composita, E. lacustris, E. gracilicauda, Acanthodiaptomus tibetanus, Bryocamptus arcticus, B. cuspidatus, B. umiatensis represent new records for this region.Fragments of COI and 18S mitochondrial genes were sequences for the first time for the Chukotka populations of the fairy shrimp Branchinecta tolli.The main types of microcrustacean taxocenes were identified, and it was shown that their species composition significantly differs among various hydrological types of water bodies.The majority of the microcrustacean species of continental Chukotka is represented by widespread Holarctic, Palaearctic and cosmopolitan species (57% of the total species richness).Additionally, 23% of species are typical of high latitudes, and 9% are Beringian species with ranges covering northeast Eurasia and northwest North America.A comparison of the crustacean species composition in continental Chukotka and Wrangel Island showed a significant impoverishment of the island fauna, due to both geographic isolation and stronger influence of unfavorable climatic factors.