Genetic differentiation of pink salmon Oncorhynchus gorbuscha Walbaum in the Asian part of the range

Genetic variation at 19 enzyme (including 11 polymorphic) and 10 microsatellite loci was examined in the population samples of odd-and even-broodline pink salmon from the southern part of Sakhalin Island, Southern Kuril Islands, and the northern coast of the Sea of Okhotsk. The estimates of relative interpopulation component of genetic variation for the allozyme loci, per broodline, were on average 0.43% (G _ST), while over the microsatellite loci it was 0.26% (the ?_ST coefficient, F-statistics based on the allele frequency variance), and 0.90% (the ρ_ST coefficient, R-statistics based on the allele size variance). The values of interlinear component constituted 2.34, 0.31, and 1.05% of the total variation, respectively. Using the allozyme loci, statistically significant intralinear heterogeneity was demonstrated among the regions, as well as among the populations of southern Sakhalin. Multidimensional scaling based on the allozyme data demonstrated regional clustering of the sample groups, representing certain populations during the spawning run or in different years. Most of the microsatellite loci examined were found to be highly polymorphic (mean heterozygosity > 0.880). The estimates of interlinear, interregional, and interpopulation variation over these loci in terms of ?_ST values were substantially lower than in terms of ρ_ST values. Regional genetic differentiation, mostly expressed at the allozyme loci between the populations from the northern Sea of Okhotsk and the Sakhalin and Kuril group of populations, was less expressed at the microsatellite loci. The differentiation between these regions observed can be considered as the evidence in favor of a large-scale isolation by distance characterizing Asian pink salmon. It is suggested that in pink salmon, low genetic differentiation at neutral microsatellite loci can be explained by extremely high heterozygosity of the loci themselves, as well as by the migration gene exchange among the populations (the estimate of the gene migration coefficient inferred from the “private” allele data constituted 2.6 to 3.4%), specifically, by the ancient migration exchange, which occurred during postglacial colonization of the range     

Interregional differentiation of chum salmon from Sakhalin and South Kurils infered from microsatellite markers

Variability at ten microsatellite loci was examined in wild and hatchery populations of chum salmon from the Sakhalin Island and Southern Kuril Islands, Iturup and Kunashir. Substantial genetic differences between Sakhalin and South Kurils chum salmon (the differentiation theta reached 6.0%) were revealed. Statistically significant differences between chum salmon from Iturup and that from Kunashir were demonstrated, as well as between the chum salmon populations from different rivers within the islands. It was shown that in different types of population comparisons, required different marker sets most informative were.     

Population structure of odd-broodline Asian pink salmon and its contrast to the even-broodline structure

Most of the variation (99%) of Asian odd-broodline pink salmon Oncorhynchus gorbuscha , based on data at 32 variable (46 total) allozyme loci from 35 populations, occurred within populations. The remaining interpopulation variation was attributable to: (1) differences between northern (the northern Sea of Okhotsk, eastern Kamchatka Peninsula and western Kamchatka Peninsula) and southern (Hokkaido Island, Kuril Islands and Sakhalin Island) populations; (2) differences between the southern areas; (3) low variation among populations within some areas. The pattern contrasted strongly with that observed for Asian even-broodline populations, which had a strong structure, possibly related to geographic and oceanographic influences. Isolation-by-distance analyses of each of the two broodlines showed a stronger relationship (x 4·8) among even- than odd-broodline populations. Allele frequency differences between even- and odd-broodlines reflected the reproductive isolation of the broodlines. However, there were no fixed frequency differences which, considered with the differing population structures, suggests that migration-drift equilibrium has not yet obtained in one or both broodlines. The structural differences also suggest it is likely that the even- and odd-broodlines are of different ages and that one is derived from the other. Allozyme data do not provide a genealogical basis for identifying the ancestral lineage.     

Population-genetic structure of Dolly varden (Salvelinus malma Walbaum) from Southeastern Sakhalin and Southern Kuril islands

The genetic structure of Dolly Varden (Salvelinus malma Walbaum) populations from six rivers of southeastern Sakhalin and six rivers of the Kuril Islands was examined using electrophoretic, analysis of 22 enzyme systems encoded by 45 loci. In all populations, mean heterozygosities (0.044-0.105), mean numbers of alleles per locus (1.15-1.52), and proportions of polymorphic loci (18.2-39.4%) were estimated for all loci that had clear resolution. Highly significant heterogeneity of allele frequencies was detected among populations of both Sakhalin and the Kuril islands. By means of cluster analysis and multidimentional scaling, all populations were divided into the Sakhalin and Kuril groups. Within the groups, no association of genetic similarity with geographic distance between populations was observed. Although the average genetic diversity was similar in these regions, the relative interpopulation diversity was almost three times higher in the Kuril (17.6%) than in the Sakhalin (6.5%) groups. In all, the proportion of genetic diversity between regions (8.4%) was somewhat lower than the proportion of mean interpopulation diversity (11.3%). In small populations isolated from the sea, genetic variation was lower than in nonisolated populations. Allozyme differences between the northern and the southern forms of Dolly Varden are discussed.     

Population genetic differentiation of white-spotted char Salvelinus leucomaenis (Pallas) in Russian Far East

The population genetic structure of white-spotted char Salvelinus leucomaenis (family Salmonidae) was determined based on variations in ten microsatellite DNA loci in samples from different parts of the species range in the Russian Far East. In a number of samples, variations in 21 allozyme loci were examined, of which five loci were found to be polymorphic. The overall diversity level at the examined markers was comparable to that observed in a closely related char species, Dolly Varden. The estimates of interpopulation genetic differentiation were highly statistically significant in most of the pairwise comparisons among the samples. The overall evaluation of the spatial genetic differentiation in white-spotted char constituted F _ST = 0.203 and R _ST = 0.202. Cluster analysis and multidimensional scaling based on microsatellite allele frequencies indicated the possible subdivision of the examined samples into two main groups, i.e., northern (represented by the regions of the north of Khabarovsk krai, Kamchatka, Yama Bay) and southern (with regions including Sakhalin, Primorye, and the Kuril Islands). The allozome data demonstrated a similar pattern of differentiation. The level of intra- and interpopulation genetic diversity in the southern group was higher than in the northern group. The isolation-by-distance test did not identify a significant correlation between genetic and geographic distances among the samples. The data obtained enabled the suggestion that the genetic structure of the populations of white-spotted char was shaped by the influence of historical geological climatic rearrangements of its range and the genetic drift because of relatively low population number and limited in the extent migration activity of its anadromous form.     

Microsatellite variability and differentiation of hatchery stocks of chum salmon Oncorhynchus keta Walbaum in Sakhalin

Variability at eight microsatellite loci was examined in five populations of chum salmon Oncorhynchus keta Walbaum from Sakhalin hatcheries. The population of Kalinino hatchery had the lowest heterozygosity and the lowest average number of alleles per locus. The populations examined exhibited significant differentiation, theta ST = 0.026 on average per locus. The maximum genetic differences were found between the populations of the Kalinino and the Ado-Tymovo hatcheries; the latter differs from the remaining populations also by the highest number and high frequencies of specific alleles. The genetic features of the Taranai hatchery population, observed at microsatellite loci, reflect its "mixed" origin.     

Interregional differentiation of chum salmon from Sakhalin and South Kurils inferred from microsatellite markers

Variability at ten microsatellite loci was examined in wild and hatchery populations of chum salmon (Oncorhynchus keta Walbaum) from the Sakhalin Island and Southern Kuril Islands, Iturup and Kunashir. Substantial genetic differences between Sakhalin and South Kurils chum salmon (the differentiation reached 6.0%) were revealed. Statistically significant differences between chum salmon from Iturup and those from Kunashir were demonstrated, as well as between the chum salmon populations from different rivers within the islands. It was shown that in different types of population comparisons, different marker sets were most informative.     

Genetic diversity of Asian chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> (Salmonidae,Salmoniformes) and the dynamics of gene pools in Sakhalin populations under artificial reproduction

The estimates of genetic diversity in populations of chum salmon Oncorhynchus keta from different regions of Sakhalin Island, Iturup Island, and the Anadyr’ River were obtained on the basis of analysis of allozyme variability. These estimates together with our published earlier data on chum salmon from the Amur River basin and the rivers of the northern coast of the Sea of Okhotsk demonstrate pronounced regional genetic differentiation in the Asian part of the fish range. The intraregional level of interpopulation genetic diversity was maximum on Sakhalin Island (G _ST = 6.6%) and was small on Iturup Island (G _ST = 0.9%) and the northern coast of the Sea of Okhotsk (G _ST = 0.6%). Interpopulation genetic diversity of Sakhalin chum salmon was almost commensurable to the diversity of the whole pool of studied Asian populations (G _ST = 7.6%) and would be presented more completely in baselines assigned for genetic identification of mixed stocks. It was demonstrated that the character and degree of genetic differentiation between populations of chum salmon from the main hatcheries situated in different regions of the Sakhalin oblast and connected to one another by numerous transplantations of fertilized eggs did not change significantly during an approximately 20-year period of our observation, and this fact suggests low efficiency of such transplantations.     

Differentiation of chum salmon Oncorhynchus keta Wallbaum populations as revealed with microsatellite and allozyme markers: A comparative study

The features and extent of population differentiation in chum salmon Oncorhynchus keta from Sakhalin and Iturup Islands were studied with 10 microsatellite and 12 allozyme markers. It was demonstrated with the example of allozyme polymorphism at the EstD locus that the effect of an individual locus with one major allele is capable of distorting the total picture of population differentiation. Multiallelic microsatellites were more efficient in revealing the genetic structure of chum salmon populations at the levels of differences between regional populations and between the stocks of individual rivers of the same region.     

Differentiation of chum salmon Oncorhynchus keta Walbaum populations as revealed with microsatellite and allozyme markers: a comparison

The character and extent of population differentiation in chum salmon Oncorhynchus keta from Sakhalin and Iturup were comparatively studied with 10 microsatellite and 12 allozyme markers. It was demonstrated with the example of allozyme polymorphism at the EstD locus that the effect of an individual locus with one major allele is capable of distorting the total picture of population differentiation. Multiallelic microsatellites were more efficient in revealing the genetic structure of chum salmon populations at the levels of differences between regional populations and between the stocks of individual rivers of the same region.     

Gene Geographic Variation and Genetic Differentiation in the Root Vole Microtus oeconomus Pallas 1776 (Cricetidae,Rodentia) from the Kuril Islands

Electrophoretic analysis of 12 enzyme systems and 3 nonenzyme proteins (in all, 24 interpretable loci) was carried out for Microtus oeconomus from ten Kuril Islands, Kamchatka Peninsula, and the vicinity of the city of Magadan. Gene geographic variation was examined and the coefficients of genetic variation and differentiation were estimated. The interpopulation allozyme differentiation was low (D _{Nei, 1972} not higher than 0.053) and caused by variation in the allele frequencies of polymorphic loci. The greatest genetic distances were found between the populations belonging to different subspecies. Allozyme differentiation of Far Eastern M. oeconomusand M. fortis are discussed in relation to the data on the age of the island isolation and paleontological records. Karyological analysis (G-, C-, and NOR-banding) demonstrated the absence of differences between M. oeconomus from Kamchatka and the vicinity of Magadan.     

Population structure of chum salmon Oncorhynchus keta in the Russian Far East, as revealed by microsatellite markers

Chum salmon populations in the Russian Far East have a complex multi-level genetic structure. A total of 53 samples (2446 fish) were grouped into five major regional clusters: the southern Kurils, eastern Sakhalin, southwestern Sakhalin, the Amur River, and a northern cluster. The northern cluster consists of chum salmon populations from a vast geographical region, including Chukotka, Kamchatka, and the continental coast of the Sea of Okhotsk. However, the degree of its genetic differentiation is low, 1.9%. In contrast, the southern population cluster exhibits much higher variation; for example, differentiation between chum salmon groups within Sakhalin Island reaches 4.6%, and the differentiation between Iturup Island and Sakhalin Island chum salmon is 7.7%. This suggests that southern populations of Asian chum salmon have a more ancient evolutionary history than northern populations. In contrast to the available data, our study indicates a great deviation of southwestern Sakhalin populations from other Sakhalin chum salmon. The Russian Far East chum salmon are genetically diverse and show statistically significant differentiation even within small geographic localities. This can be used to assign samples of unknown origins to definite local populations.     

Genetic diversity of north Okhotsk Sea chum salmon populations with natural and artificial reproduction

The variability of 32 enzyme loci was studied in chum salmon populations with different types of reproduction—natural, mixed, and artificial—in some Magadan Region rivers. Among the populations studied, the values of mean heterozygosity and allele number per locus did not differ significantly. We found evidence of definite temporal stability of the populations, and also found that their genetic variability was expressed only slightly but still remained in spite of periodic egg transplantations between rivers. Statistically significant spatial genetic differentiation of the populations accounted for 0.55 to 0.76% of the total variation and the mean inter-year differentiation accounted for 0.30% of the total. Significant temporal (seasonal) genetic subdivision was revealed in chum salmon of the Tauy River. The populations of the Okhotsk Sea coast are very similar genetically to the east Sakhalin populations. The industrial chum salmon population founded and reproduced artificially in the Kulkuty River preserves the genetic similarity of the donor Yama River chum salmon. In the industrial population, we observed a tendency toward reduction of genetic variation over time. The contribution of the Yama population to the gene pool of the Ola chum salmon, (both by natural reproduction and by farming) is small in spite of many large-scale transplantations. However, the consequences of those transplantations are revealed by means of linkage disequilibrium analysis.     

Geographical and temporal mitochondrial DNA variability in populations of pink salmon

Pink salmon Oncorhynchus gorbuscha from odd and even year generations in rivers of Sakhalin Island, Kuril Island, Kamchatka Peninsula, and Alaska were investigated with five informative restriction endonucleases for mtDNA variation. The odd and even generations from the same rivers of South Sakhalin differed greatly. The time of divergence between the two broodlines was estimated at 0.9-1.1 Myr. The variability of mtDNA in odd year generations was higher than in even year generations and may have been due to' founder' and/or' bottleneck' effects. The differences among river populations within the Sakhalin region in 1991-1993 were not significant and this confirms the highly migratory nature of pink compared with other Pacific salmon. The mtDNA samples revealed statistically significant differences between regions. The northern populations (Kamchatka, Alaska) were less diverse in number and frequency of haplotypes than the southern populations (Sakhalin). This suggests that pink salmon originated in the Sakhalin-Kuril region and that a founder effect during the spread of this species may have restricted the mtDNA variability in other regions.     

Variability of size-age indices and genetic variability of sockeye salmon <Emphasis Type="Italic">Oncorhynchus nerka</Emphasis> from the Western Coast of Kamchatka: Comparative analysis of methods of differentiation of local populations

Study of variability of size-age indices and polymorphism of 6 microsatellite loci, 5 loci of SNP, and accidentally amplified polymorphic DNA (RAPD) of sockeye salmon Oncorhynchus nerka of three largest populations from the western coast of Kamchatka Peninsula was performed. The efficiency of using different types of markers for the differentiation of populations and determination of the population belonging of sockeye salmon from lake-river systems of western Kamchatka was analyzed. Significant interpopulation differences were revealed from the frequencies of alleles of genetic markers and from a set of biological indices. It was established that genetic markers are characterized by a better differentiating capacity, as compared to biological characteristics. The most satisfactory results during determination of population belonging of sockeye salmon were obtained using an integrated data base of allele frequencies of microsatellite and SNP loci.     

Microsatellite analysis of genetic diversity and population genetic structure of a wild rice (<Emphasis Type="Italic">Oryza rufipogon</Emphasis> Griff.) in China

Genetic diversity and population genetic structure of natural Oryza rufipogon populations in China were studied based on ten microsatellite loci. For a total of 237 individuals of 12 populations collected from four regions, a moderate to high level of genetic diversity was observed at population levels with the number of alleles per locus ( A) ranging from 2 to 18 (average 10.6), and polymorphic loci ( P) from 40.0% to 100% (average 83.3%). The observed heterozygosity ( H(O)) varied from 0.163 to 0.550 with the mean of 0.332, and the expected heterozygosity ( H(E)) from 0.164 to 0.648 with the mean of 0.413. The level of genetic diversity for Guangxi was the highest. These results are in good agreement with previous allozyme and RAPD studies. However, it was unexpected that high genetic differentiation among populations was found ( R(ST) = 0.5199, theta = 0.491), suggesting that about one-half of the genetic variation existed between the populations. Differentiation (pairwise theta) was positively correlated with geographical distance ( r = 0.464), as expected under the isolation by distance model. The habitat destruction and degradation throughout the geographic range of O. rufipogon may be the main factor attributed to high genetic differentiation among populations of O. rufipogon in China.     

Genetic divergence in pink salmon introduced into the European north of Russia: microsatellite and allozyme variation analysis

The 1985 introduction into the European North of Russia resulted in the formation of a large stock of pink salmon of the odd-year breeding line. To assess the divergence of the new population and the role of various microevolutionary factors, variation of four microsatellite loci and fifteen genes encoding proteins (allozymes) in samples of fish, running for spawning in rivers of the new area, and in samples from the donor population of the Ola River (Magadan oblast). In the generations 8 and 9 of the introduced pink salmon of the odd-year line, the genetic diversity (the number of alleles and the mean heterozygosity) both at allozyme and at microsatellite loci was significantly lower, than that in the donor population. The explanations of the decline in diversity are discussed. The first evidence for spatial genetic divergence in transplanted fish within the new area has been obtained; the divergence level may be comparable with that characteristic of native populations.     

Gene Variation, Population Differentiation, and Sociogenetic Structure of Nests of Partamona seridoensis (Hymenoptera: Apidae, Meliponini)

Gene variation and the differentiation of two populations of Partamona seridoensis (Hymenoptera: Apidae: Meliponini) from the Caatinga biome, a semiarid ecosystem unique to Brazil, were estimated through allozymic and microsatellite analyses. These populations exhibited similar low degrees of enzyme gene variation. Observed genotype frequencies at the allozyme and microsatellite loci were in accordance with Hardy-Weinberg equilibrium in the two populations. Both markers demonstrated that the two populations are not genetically homogeneous and must be considered distinct populations. The occurrence of private alleles at the allozyme and microsatellite loci corroborates this differentiation, sustaining the hypothesis of a low level of interpopulation gene flow. The phenotypic segregations clearly demonstrated that the progeny inside each nest were the result of mating between the queen of the colony and only one male.     

The influence of history and contemporary stream hydrology on the evolution of genetic diversity within species: an examination of microsatellite DNA variation in bull trout,Salvelinus confluentus (Pisces: Salmonidae)

An understanding of the relative roles of historical and contemporary factors in structuring genetic variation is a fundamental, but understudied aspect of geographic variation. We examined geographic variation in microsatellite DNA allele frequencies in bull trout (Salvelinus confluentus, Salmonidae) to test hypotheses concerning the relative roles of postglacial dispersal (historical) and current landscape features (contemporary) in structuring genetic variability and population differentiation. Bull trout exhibit relatively low intrapopulation microsatellite variation (average of 1.9 alleles per locus, average He = 0.24), but high levels of interpopulation divergence (F(ST) = 0.39). We found evidence of historical influences on microsatellite variation in the form of a decrease in the number of alleles and heterozygosities in populations on the periphery of the range relative to populations closer to putative glacial refugia. In addition, one region of British Columbia that was colonized later during deglaciation and by more indirect watershed connections showed less developed and more variable patterns of isolation by distance than a similar region colonized earlier and more directly from refugia. Current spatial and drainage interconnectedness among sites and the presence of migration barriers (falls and cascades) within individual streams were found to be important contemporary factors influencing historical patterns of genetic variability and interpopulation divergence. Our work illustrates the limited utility of equilibrium models to delineate population structure and patterns of genetic diversity in recently founded populations or those inhabiting highly heterogeneous environments, and it highlights the need for approaches incorporating a landscape context for population divergence. Substantial microsatellite DNA divergence among bull trout populations may also signal divergence in traits important to population persistence in specific environments.     

Genetic divergence in pink salmon introduced into the European North of Russia: Microsatellite and allozyme variation analysis

The 1985 introduction into the European North of Russia resulted in the formation of a large stock of pink salmon of the odd-year broodline. To assess the divergence of the new population and the role of various microevolutionary factors, variation of four microsatellite loci and fifteen genes encoding proteins (allozymes) in samples of fish, running for spawning in rivers of the new area, and in samples from the donor population of the Ola River (Magadan region). In the generations 8 and 9 of the introduced pink salmon of the odd-year line, the genetic diversity (the number of alleles and the mean heterozygosity) both at allozyme and at microsatellite loci was significantly lower, than that in the donor population. The explanations of the decline in diversity are discussed. The first evidence for spatial genetic divergence in transplanted fish within the new area has been obtained; the divergence level may be comparable with that characteristic of native populations.