[Analysis of mtDNA and Nuclear Markers Points to Homoploid Hybrid Origin of the New Species of Far Eastern Redfins of the Genus Tribolodon (Pisces, Cyprinidae)].

The nucleotide sequences of two mitochondrial genes (cytochrome c oxidase subunit I, COI, and cytochrome b, cyt b) and four nuclear genes (growth hormone gene GH1, ribosomal protein S7 gene RP1, recombination activating gene RAG1, and rhodopsin gene RH) from the Far Eastern redfins of the genus Tribolodon were examined to clarify the status of the southern form of T. hakonensis. Nucleotide sequence analysis of the mitochondrial genes showed differences of 2.6% between individuals of T. hakonensis inhabiting the north and south of the range. Analysis of the nuclear genes showed that Tribolodon sp. (southern form of T. hakonensis) has a mosaic of nuclear genes received from the Pacific redfin T. brandtii and big-scaled redfin T. hakonensis. It is suggested that the new species could have formed as a result of homoploid hybridization between the true T. hakonensis (by original description) and T. brandtii, which probably made it possible for this species to occupy a new ecological niche.

[Comparative analysis of mitochondrial DNA variation in four species of far eastern redfins of the genus Tribolodon (Pisces, Cyprinidae)].

MtDNA variations were examined in four endemic species of the Far Eastern redfins of the genus Tribolodon across considerable parts of their ranges. No close correlation was revealed between the lifespan of the species and the level of mtDNA variations. An association was revealed between the degree of manifestation of the genetic structure population and the degree ofamphidromy in the species. The presence of differing mtDNA phylogroups in three out of four species indicates that the history of these species included long period of independent intraspecific divergent evolution. This period occurred at approximately the same historical time and was probably caused by the same factors. The period appeared to be not long enough and ended with the association of genetically independent units into single species.

[Phylogeographic analysis reveals two periods of divergence in large-scaled redfin Tribolodon hakonensis (Pisces, Cyprinidae)].

Analysis of mtDNA variation in one of the amphidromic Far Eastern redfins, Tribolodon hakonensis, revealed the presence of three considerably genetically different mtDNA phylogroups in the individuals from the Russian part of the range. These data suggest the presence of the two periods of divergent evolution in the history of the species examined. Comparison of the haplotype distributions from different phylogroups over the species range revealed geographic localization of only one phylogroup in the population samples from southern continental coastal regions of the Sea of Japan. At the same time, two other phylogroups were found in almost equal ratios in northern continental samples and near the Sakhalin Island. These results suggest that the first stage of the divergent evolution, which occured between Pliocene and Pleistocene, resulted in the formation of genetically isolated form (probably, a species) in the region of the Sea of Japan. The second, later period of divergence, probably associated with the separation of the Sea of Okhotsk from the Pacific Ocean then ended with the integration of earlier genetically separated forms into one species with the common gene pool.

[Erratic divergent evolution in fish from the Northern Pacific].

The mtDNA divergence was examined in some families of anadromous and semi-anadromous fish. Heterogeneous distribution of the divergence values along the scale was demonstrated. Statistically significantly higher number of the species pairs were characterized by divergence values ranging from 2 to 4% and 5 to 12% of nucleotide substitutions. These results suggest that in different monophyletic groups occupying common historical ranges, divergence-associated speciation often happened within similar time intervals. Comparison of the species divergence time calculated using the molecular clock pointed to the coincidence of the radiation periods in the taxa with paleogeological and paleoclimatic global changes in the history of Northern Pacific.

Analysis of mitochondrial DNA: taxonomic and phylogenetic relationships in two fish taxa (Pisces: Mugilidae and Cyprinidae).

To solve some systematic questions as well as to study genetic variability and evolutionary relationships in two groups of fish belonging to the Mugilid (Mugilidae) and Cyprinid (Cyprinidae) families, we have used restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA) fragments amplified in polymerase chain reaction. The analysis of three mtDNA fragments of 7220 bp total length of six Mugilid species has shown that Mediterranean Liza aurata, L. ramada, L. saliens, and Chelon labrosus form a common cluster, L. aurata and C. labrosus being the closest relatives, whereas L. haematocheilus (syn. C. haematocheilus) of the Sea of Japan forms a sister group to the Mediterranean cluster. It was found that Chelon and Liza genera are paraphyletic, and therefore their division into two genera is unnatural and they should be synonymized. According to priority, Liza species should be ascribed to Chelon genus. Mugil cephalus is the most distant compared to the rest of the species studied. The level of genetic divergence between allopatric samples of M. cephalus from the Sea of Japan and the Mediterranean Sea has proved to be very high--4.5% of nucleotide substitutions. The analysis of four mtDNA fragments of 9340 bp total length of six Cyprinid species has shown that L. waleckii is the most genetically distant. Pseudaspius leptocephalus is a sister group to Tribolodon species. All Tribolodon species form a common cluster with T. sachalinensis as a root. The remaining species form two branches, one of which includes T. nakamurai and T. brandtii, another one combines T. hakonensis and a new form of Tribolodon revealed that is close to T. hakonensis by its mtDNA (2.4% of nucleotide substitutions). This new form might be an independent species.

[The variation in chum salmon Oncorhynchus keta (Walbaum) mitochondrial DNA and its connection with the paleogeographic events in the Northwest Pacific].

The results of examining mtDNA variation in populations of chum salmon Oncorhynchus keta from the rivers of the basins of the seas of Japan and Okhotsk and in the chum salmon seasonal races of the Amur River are presented. A significant level of polymorphism between the majority of the populations studied was detected. The groups of chum salmon from the Japan and Okhotsk Seas displayed the most pronounced differences. Analysis of genetic variation demonstrated that periodic paleontologic and climatic changes in the past of this region were the most probable factor that caused the divergence of these populations. The advances and retreats of glaciers and the accompanying regressions and transgressions of the ocean level caused isolation of chum salmon in the refugia belonging hypothetically to the paleo-Suifun and paleo-Amur regions. These population groups diverged presumably 350-450 thousand years ago. Differences between the seasonal races of the Amur chum salmon are insignificant, and their emergence dates back to the period of the last Wisconsin glaciation. Probably, the main isolation factor now is the genetically determined time of spawning.