No 5 (2022)

This work was aimed to a comparative analysis and reconstruction of the phylogenetic position of sunbleak Leucaspius delineatus (Heckel, 1843) from the Irkutsk Reservoir. Determination of a species specific fragment of the Cox1 gene allowed to reveal a unique common haplotype present in all specimens analyzed. Comparative analysis and phylogenetic reconstruction based on nucleotide sequences available in genetic databases showed that the studied species is represented by three phylogenetic lineages. Intraspecific differences of nucleotide sequences of fragments of the Cox1 gene amounted to 5.5%, and within phylogenetic lineages - < 3%. The studied fishes were related to the genetic lineage widely distributed in Europe and northwestern Russia. It is shown that all specimens with 100% genetic similarity belong to the same genotype, which is due to recent introduction of sunbleak into Pre-Baikal and to the “founder effect”.

The dispersal of aquatic organisms has especially increased since the 19th century, mainly due to the introduction of metal ships with ballast compartments or with birds. Along with easily visible aquatic organisms, there are invasions of less noticeable aquatic organisms, like copepods, which can mainly be recognized by experts. A special group is made up of cryptic species for which morphological identification is inaccessible or very difficult. This review is devoted to the identification, description and analysis of the dispersal routes of three copepod cryptic species complexes into waterbodies. Using molecular-genetic methods, Eurytemora carolleeae introduction were revealed in 2007. After describing this invader as a new species, its distribution was also studied using morphology. The invasions of Acanthocyclops americanus and Eurytemora caspica were mainly studied using morphological methods since the species have already been described; however, molecular-genetic methods were also used to confirm their distinctions from local forms. The real distribution of the former “cosmopolitan” species Eucyclops serrulatus was studied using a multidisciplinary approach that combined molecular-genetic, cross-hybridization and morphological methods. Judging by the distribution of local E. serrulatus sensu stricto populations in coastal waterbodies of most continents, this species can apparently serve as a good marker of the species dispersal processes with ships. The three possible scenarios resulting from cryptic species introductions and their interaction with local fauna were competitive displacement (A. americanus), competitive coexistence (E. carrolleeae) and independent development without competition (E. serrulatus). The role of cryptic species invasion in aquatic biodiversity modification is discussed.

The review examines the work on biodiversity in the reservoirs of Eastern Siberia of a wide, but poorly studied group of organisms forming siliceous scales and bristles – these are scaled chrysophytes, chrysophycean stomatocysts and heterotrophic protists: rotosphaerids, colorless free-living thaumatomonad flagellates, centrohelid heliozoans. The difficulty in studying these objects is the need to use electron microscopy for their species identification. High biodiversity of silica scaled Protozoa has been revealed in the reservoirs of Eastern Siberia and the relationship of their species composition with the parameters of the aquatic environment, including in areas of local anthropogenic impact, has been shown. The recorded enrichment of the mouths of Arctic rivers with boreal species is important for predicting changes in aquatic ecosystems in the context of GCC. The proposed scenario of the settlement of siliceous chrysophytes at the beginning of the Holocene may be valid for other small planktonic organisms. The high degree of preservation of siliceous stomatocysts in sediments allows them to be used as an additional signal of changes in lake ecosystems in the past, this is based in particular on the reconstruction of the ecosystem and changes in the level of Lake Vorota (Yakutia) in the Holocene-Upper Pleistocene.