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.     

The genetic structure of chum salmon (<Emphasis Type="Italic">Oncorhynchus keta</Emphasis> Walbaum) populations inferred from the nucleotide variation of the mitochondrial DNA cytochrome <Emphasis Type="Italic">b</Emphasis> gene

The nucleotide sequences of a fragment of the mitochondrial DNA cytochrome b gene were determined in 12 chum salmon populations from the Russian Far East. The level of genetic diversity in the chum salmon populations from the Iturup Island, northern coast of the Sea of Okhotsk, and Anadyr’ River was found to be higher than in the populations from Kamchatka and Sakhalin, which may be related to the history of their origin and dispersal. The proportions of intrapopulation genetic variability (F _CT) and interpopulation genetic variability within the groups (F _SC) account for 90.87 and 0.9%, respectively, and the intergroup component (F _ST) comprises 8.23%. The predominance of one haplotype, B1, which is common for all populations studied, and a low share of intergroup variability suggest the beginning of colonization by the species of the given region from a common source (group of founders) and a relatively recent time of divergence of the chum salmon populations from the region examined.     

Polymorphism of Chloroplast DNA and Phylogeography of Green Alder (<Emphasis Type="Italic">Alnus alnobetula</Emphasis> (Ehrh.) K. Koch s. l.) in Asiatic Russia

This paper studies the phylogeography of Alnus alnobetula s. l. in the Asian part of the Russian range with the use of chloroplast DNA (cpDNA) sequences (intergenic spacers trnH-psbA, trnS-trnG, and psaA-trnS). Nine haplotypes were identified as a result of a combination of polymorphism of all sites in 241 plants in 20 populations of A. alnobetula. High interpopulation differentiation (G_ST = 0.914, N_ST = 0.928) and a significant phylogeographic structure (N_ST > G_ST, p < 0.05) were found. Reconstruction of genealogical relationships of green alder haplotypes revealed five highly divergent genetic lineages: one geographically widespread throughout Siberia and the Urals and several allopatric lines in the Far East of Russia, namely, the Chukotka Peninsula and the mouth of the Yana River, Magadan oblast, Primorye and the central part of Sakhalin Island, and the southern part of Sakhalin Island. Our data confirm that in the past the range of this species in the Far East was fragmented in several refugia that were isolated for a long time in various ice-free regions. This could have contributed to a high level of intraspecific polymorphism of green alder as a result of the divergence of endemic haplotypes, with almost non-overlapping distribution. However, the level of their molecular divergence does not correspond to the level of morphological differences.     

Genetic differentiation and the problems of conservation of masu salmon (<Emphasis Type="Italic">Oncorhynchus masou</Emphasis> Brevoort, 1856 (Pisces: Salmonidae)) populations

This study focuses on the strategy for the conservation of masu salmon, Oncorhynchus masou, in the northern part of the species range (via the masu populations in Sakhalin Oblast), based on data of its population structure. It is shown that masu populations that inhabit different rivers genetically differ from each other in allele frequencies at microsatellite markers. In the Naiba River basin, at least two genetically distinct masu populations exist: in the upper reaches and in a tributary, the Bolshoy Takoy River. The masu populations on Iturup Island significantly differ from those on Sakhalin Island; within Sakhalin, the masu salmon from the Chernaya River in the southwestern part of the island is genetically distinct from the southeastern Sakhalin and Aniva Bay populations. The genetic diversity of Iturup populations is substantially lower than that on Sakhalin, probably due to their small sizes. The measures for the conservation and recovery of masu salmon populations should be based primarily on their own genetic resources, or, in the case of a lack of spawners, on the base populations of their ecological/geographical region. In the latter case, masu populations of large rivers can be considered as base ones: for southeastern Sakhalin, this is masu salmon of the Naiba River; for Aniva Bay, this is masu salmon of the Lyutoga River. Transplantation of fish, fertilized eggs, or any other genetic material from a population that is different genetically and inhabits the waters with different ecological gradients should be strongly restricted. The formosan masu salmon from Taiwan Island is studied as an example of a strict genetic isolate.     

Origin of juvenile chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> (Salmonidae) in the Sea of Okhotsk coastal waters off South Sakhalin

Based on the data of the analysis of distribution of juvenile chum salmon Oncorhynchus keta that were marked at salmon hatcheries in the southern part of the Sakhalin Island and Japan it has been established that their stocks in the Sea of Okhotsk coastal waters off South Sakhalin and Japan are of mixed origin. One part of the stock is composed of juveniles from hatcheries located in the southern part of Sakhalin, and the other part is composed of migrants from the waters adjacent to Japan. The first part is formed by juveniles both from hatcheries on the Sea of Okhotsk and Sea of Japan coasts of South Sakhalin. The second part is formed by juveniles reared at hatcheries in all regions of Japan: the Pacific and Sea of Okhotsk coasts of Honshu and Hokkaido, and from the Sea of Okhotsk coast of Hokkaido and Izmena (Nemuro) Strait. In July, in the Sea of Okhotsk coastal waters off South Sakhalin, the length and weight of most juvenile chum salmon of Japanese origin exceed 10 cm and 10 g, and juveniles of Sakhalin origin are always smaller than 10 cm and 10 g, which makes it possible to differentiate juveniles in trawl catches.     

High genetic diversity in an endangered medicinal plant, <Emphasis Type="Italic">Saussurea involucrata</Emphasis> (<Emphasis Type="Italic">Saussurea</Emphasis>, Asteraceae), in western Tianshan Mountains,China

Saussurea involucrata (Asteraceae) is a medicinal and second-degree national priority endangered plant that is mainly distributed in the high latitude region of the western Tianshan Mountains. The population is fragmented and isolated, and extensive human impact merits a suitable and specific conservation strategy, which can be compiled based on the genetic diversity, population structure, and demographic history. Phylogeographic studies were conducted on a total of five natural populations and 150 individuals were sampled. Data from three cpDNA intergenic spacer regions (trnL-F, matK, and ndhF-rpl32) and nrDNA ITS sequences showed that twelve haplotypes in cpDNA and five haplotypes in nrDNA indicated high genetic diversity among populations sampled (H _T?=?0.820 and 0.756) and within populations sampled (H _S?=?0.792 and 0.721). Additionally, the high genetic diversity did not mirror genetic structure in either cpDNA (F _ST?=?0.03153, G _ST?>?N _ST, p?<?0.05) or nrDNA (F _ST?=?0.03666, meaningless G _ST and N _ST). Two groups (north and south) were determined for a SAMOVA analysis. Based on this analysis, the demographic history was conducted with a Bayesian Skyline Plot and Isolation with Migration analysis, which showed sustainable and stable extension without a marked bottleneck. Divergence time was indicated at c. 6.25 Mya (90%HPD: 15.30–0.22 Mya) in the Miocene, which is consistent with the formation of the Kelasu section of Tianshan. The southern populations in the Bayanbulak and Gonglu regions require additional attention and transplanting would be an effective way to restore rare cpDNA haplotypes, increase effective population size, and migration rate. Our results suggested that in situ conservation of S. involucrata in western Tianshan should be the main strategy for protection and recovery of the species.     

Genetic variability in anadromous fishes,chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> (Walbaum, 1792), and Sakhalin taimen <Emphasis Type="Italic">Parahucho perryi</Emphasis> (Brevoort, 1856) from the Northwestern Pacific as a reflection of paleoclimate oscilations

The genetic variability distribution of two mtDNA segments of chum salmon (Oncorhynchus keta) (Walbaum, 1792) and Sakhalin taimen (Parahucho perryi) (Brevoort, 1856) was examined in populations of the Sea of Japan and the Sea of Okhotsk. The values of haplotype and nucleotide variability in these species are, in general, of the same level. The dating of the divergence time of species haplotypes revealed four evolutionary periods in Sakhalin taimen and three in chum salmon. In the taimen, the first divergence time occurred approximately 430 thousand years (kyr) ago, the second 220 kyr ago, and the third 70 kyr ago. In the chum salmon, the first divergence time corresponds to 220 kyr; the second is approximately 100 kyr ago. In both species, the main portion of presently revealed haplotypes evolved over the past 50–10 kyr. Certain glacioeustatic sea level fluctuations influenced each stage of evolution history of species, contributing to their geographic isolation. Demographic population history research found that the initial stage of population growth in the taimen occurred at the time period of approximately 12 kyr ago and was apparently associated with the end of the Last Glacial Maximum. In the chum salmon, this period began somewhat earlier, 30–35 kyr ago; it has accelerated in the past 10–15 kyr. The last glaciation to a lesser extent impacted the demographics of chum salmon, probably due to the greater eurythermity and to the larger range of this species.     

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.     

Elucidating the multiple genetic lineages and population genetic structure of the brooding coral <Emphasis Type="Italic">Seriatopora</Emphasis> (Scleractinia: Pocilloporidae) in the Ryukyu Archipelago

The elucidation of species diversity and connectivity is essential for conserving coral reef communities and for understanding the characteristics of coral populations. To assess the species diversity, intraspecific genetic diversity, and genetic differentiation among populations of the brooding coral Seriatopora spp., we conducted phylogenetic and population genetic analyses using a mitochondrial DNA control region and microsatellites at ten sites in the Ryukyu Archipelago, Japan. At least three genetic lineages of Seriatopora (Seriatopora-A, -B, and -C) were detected in our specimens. We collected colonies morphologically similar to Seriatopora hystrix, but these may have included multiple, genetically distinct species. Although sexual reproduction maintains the populations of all the genetic lineages, Seriatopora-A and Seriatopora-C had lower genetic diversity than Seriatopora-B. We detected significant genetic differentiation in Seriatopora-B among the three populations as follows: pairwise F _ST = 0.064–0.116 (all P = 0.001), pairwise G′′_ST = 0.107–0.209 (all P = 0.001). Additionally, only one migrant from an unsampled population was genetically identified within Seriatopora-B. Because the peak of the settlement of Seriatopora larvae is within 1 d and almost all larvae are settled within 5 d of spawning, our observations may be related to low dispersal ability. Populations of Seriatopora in the Ryukyu Archipelago will probably not recover unless there is substantial new recruitment from distant populations.     

On possible re-distribution of pink salmon <Emphasis Type="Italic">Onchorhynchus gorbuscha</Emphasis> between the reproduction areas of different stocks in the Sakhalin-Kuril region

The scale structure of pink salmon Oncorhynchus gorbuscha inhabiting southern Sakhalin and Iturup Island were studied in 2014. These locations are characterized by the unusual dynamics of catches and biological parameters of the fish that come to spawn in different areas in the Sakhalin-Kuril region. The pink salmon that has originated from Iturup Island appeared en masse in the waters of southern Sakhalin, according to the analysis of the scleritogram fragments that reflect the fish growth during the first months of life. This is the first confirmation of the hypothesis of the fluctuating stocks of pink salmon approved by the ichthyological methods. It is suggested that wide-scale straying of pink salmon takes place in the years of dominance shift between the generations of even and odd spawning years.     

Dynamics of the abundance and conditions of reproduction of mass species of pacific salmons (<Emphasis Type="Italic">Oncorhynchus</Emphasis>) on the northwestern coast of Sakhalin

The efficiency of reproduction of Pacific salmons of the genus Oncorhynchus in the rivers of the northwestern coast of Sakhalin Island is characterized on the basis of long-term data (1989?2014). Differences between the rivers in the northern and southern parts of the region under study have been revealed with respect to the channel type, faunistic composition of the aquatic biota, and prevailing species of salmons. A high spawning efficiency of pink salmon O. gorbuscha, high densities of filling of spawning grounds, and a relatively poor composition of the freshwater ichthyofauna have been recorded in the rivers of the northern part with the mountain–piedmont type of channel. Varied fish population and the high spawning efficiency of chum salmon O. keta have been recorded in the rivers of the southern part with the mainly lowland channel. The salmon spawning area in the rivers of the northern and southern parts has been estimated. The data on the dynamics of the abundance of salmons on the northwestern coast of Sakhalin are given. The total value of the passage of spawners to the rivers of northwestern Sakhalin that is required for effective reproduction has been estimated, ranging from 0.672 to 1.639 million specimens for pink salmon and approximately 0.43 million specimens for chum salmon.     

Microsatellite Variability of Pacific Herring <Emphasis Type="Italic">Clupea pallasii</Emphasis> Valenciennes, 1847 from the Sea of Okhotsk and Bering Sea

The genetic variability of ten microsatellite loci was examined in samples of the herring from the Sea of Okhotsk and the Bering Sea. All loci were polymorphic; the expected heterozygosity estimates varied in the range of 0.3–94.3% (mean 66.7%). The degree of genetic differentiation of the herring was statistically significant (θ = 1.38%). The level of pairwise genetic differentiation F_ST was–0.002–0.046; R_ST was–0.003–0.166. Genetic differentiation of the herring from the Sea of Okhotsk and the Bering Sea correlated with the spatial-geographic structure of the species in the studied range on the basis of F_ST (P = 0.001).     

Mitochondrial DNA variation pattern in larches of Eastern Siberia and the Far East

Genetic variation has been studied in 32 Eastern Siberian and Far Eastern populations of Larix Mill. with the use of three mitochondrial markers based on polymerase chain reaction. Eight multilocus haplotypes with a heterogeneous spatial distribution (G _ST = 0.788, N _ST = 0.829) have been found, which indicates limited gene flows between populations. Several geographic regions with specific larch haplotype sets have been determined: (1) Japan, (2) southern Sakhalin and the Kuril Islands, (3) Primor’e and Korea, (4) Kamchatka, and (5) Eastern Siberia and the northern Far East. The haplotype fixed in the Kamchatka is absent in the Magadan oblast or Chukotka but is present in southern Primor’e and Sakhalin Island. This may be explained by either the postglacial recolonization of Kamchatka by larch that spread from Primor’e through Sakhalin and the Kuril Islands or its survival through the last glacial maximum in the Kamchatka Peninsula. The biogeography of larch and other woody plants indicate that boreal species have a common history of the colonization of Kamchatka.     

Genetic population structure and low genetic diversity in the over-exploited sea cucumber <Emphasis Type="Italic">Holothuria edulis</Emphasis> Lesson, 1830 (Echinodermata: Holothuroidea) in Okinawa Island

Understanding genetic connectivity is fundamental for ecosystem-based management of marine resources. Here we investigate the metapopulation structure of the edible sea cucumber Holothuria edulis Lesson, 1830 across Okinawa Island, Japan. This species is of economic and ecological importance and is distributed from the Red Sea to Hawai‘i. We examined sequence variation in fragments of mitochondrial cytochrome oxidase subunit I (COI) and 16S ribosomal RNA (16S), and nuclear histone (H3) at six locations across Okinawa Island. We found higher haplotype diversity for mtDNA (COI: Hd = 0.69 and 16S: Hd = 0.67) and higher heterozygosity of nDNA (H3: H _E = 0.39) in populations from the west coast of Okinawa compared to individuals from populations on the east coast (COI: Hd = 0.40; 16S: Hd = 0.21; H3: H _E = 0.14). Overall population structure was significant (AMOVA results for COI: Φ _ST = 0.49, P < 0.0001; 16S: Φ _ST = 0.34, P < 0.0001; H3: Φ _ST = 0.12, P < 0.0001). One population in the east, Uruma, showed elevated pairwise Φ _ST values in comparisons with all other sites and a marked reduction of genetic diversity (COI: Hd = 0.25 and 16S: Hd = 0.24), possibly as a consequence of a shift to a more dominant asexual reproduction mode. Recent reports have indicated that coastal development in this area influences many marine organisms, and ecosystem degradation in this location could cause the observed decrease of genetic diversity and isolation of H. edulis in Uruma. Our study should provide valuable data to help with the urgently needed management of sea cucumber populations in Okinawa, and indicates particular attention needs to be paid to vulnerable locations.     

A mountain range is a strong genetic barrier between populations of <Emphasis Type="Italic">Afzelia quanzensis</Emphasis> (pod mahogany) with low genetic diversity

Understanding patterns of genetic diversity of plants is important in guiding conservation programs. The aim of our study was to characterize genetic diversity in Afzelia quanzensis, an economically important African tree species. We genotyped 192 individuals at 10 nuclear microsatellite loci. Samples were collected from nine sites in Zimbabwe, five in the north and four in the south, separated by a mountain range, the Kalahari-Zimbabwe axis. Overall, genetic diversity was relatively low across all sites (expected heterozygosity (H _E)?=?0.452, mean number of alleles (A)?=?4.367, allelic richness (A _R)?=?2.917, effective number of alleles (A _E)?=?2.208, and private allelic richness (PA_R)?=?0.197). Genetic diversity estimates, H _E, A, A _R, and PA_R, were not significantly different between northern and southern sites. Allelic richness was significantly higher in southern sites. Significant population differentiation was observed among all sites (F _ST ?=?0.0936, G′ _ST ?=?0.1982, G _ST ?=?0.1001, D _JOST?=?0.0598). STRUCTURE analysis and principal components analysis identified two gene pools, one predominantly made up of southern individuals, and the other of northern individuals. A Monmonier’s function detected a genetic barrier that coincided with the Kalahari-Zimbabwe axis. The relatively low level of genetic diversity in A. quanzensis may reduce adaptability and limit future evolutionary responses. All sites should be monitored for deleterious effects of low genetic diversity, and genetic resource management should take into consideration the existence of the distinct gene pools to capture the entire extant genetic variation.     

Comparison of molecular genetic utilities of TD,AFLP, and MSAP among the accessions of <Emphasis Type="Italic">japonica,indica</Emphasis>, and <Emphasis Type="Italic">Tongil</Emphasis> of <Emphasis Type="Italic">Oryza sativa</Emphasis> L.

Rice is one of the most important food crops in the world. Genetic diversity is essential for cultivar improvement programs. We compared genetic diversity derived from insertion–deletion (in–del) or base substitutions by amplified fragment length polymorphism (AFLP), from transposon transposition mutations by transposon display (TD), and from cytosine methylation by methylation-sensitive amplified polymorphism (MSAP) in japonica, indica, and Tongil type varieties of Oryza sativa L. Polymorphic profiles from the three marker systems allowed us to clearly distinguish the three types of varieties. The indica type varieties showed the highest genetic diversity followed by the Tongil and japonica type varieties. Of the three marker systems, TD produced the highest marker indices, and AFLP and MSAP produced similar marker indices. Pair-wise comparisons of the three marker systems showed that the correlation between the two genetic markers systems (AFLP and TD, r = 0.959) was higher than the correlations between the genetic and epigenetic marker systems (AFLP and MSAP, r = 0.52; TD and MSAP, r = 0.505). Both genetic marker systems had similar levels of gene differentiation (G _ST ) and gene flow (N _m ), which differed in the epigenetic marker system. Although the G _ST of the epigenetic marker system was lower than the genetic marker systems, the N _m of the epigenetic marker system was higher than in the genetic marker systems, indicating that epigenetic variations have a greater influence than genetic variations among the O. sativa L. types.     

Pelagic larval dispersal habits influence the population genetic structure of clam <Emphasis Type="Italic">Gomphina aequilatera</Emphasis> in China

Pelagic larval dispersal habits influence the population genetic structure of marine mollusk organisms via gene flow. The genetic information of the clam Gomphina aequilatera (short larval stage, 10 days) which is ecologically and economically important in the China coast is unknown. To determine the influence of planktonic larval duration on the genetic structure of G. aequilatera. Mitochondrial markers, cytochrome oxidase subunit i (COI) and 12S ribosomal RNA (12S rRNA), were used to investigate the population structure of wild G. aequilatera specimens from four China Sea coastal locations (Zhoushan, Nanji Island, Zhangpu and Beihai). Partial COI (685 bp) and 12S rRNA (350 bp) sequences were determined. High level and significant F_ST values were obtained among the different localities, based on either COI (F_ST?=?0.100–0.444, P?<?0.05) or 12S rRNA (F_ST?=?0.193–0.742, P?<?0.05), indicating a high degree of genetic differentiation among the populations. The pairwise N_m between Beihai and Zhoushan for COI was 0.626 and the other four pairwise N_m values were >?1, indicating extensive gene flow among them. The 12S rRNA showed the same pattern. AMOVA test results for COI and 12S rRNA indicated major genetic variation within the populations: 77.96% within and 22.04% among the populations for COI, 55.73% within and 44.27% among the populations for 12S rRNA. A median-joining network suggested obvious genetic differentiation between the Zhoushan and Beihai populations. This study revealed the extant population genetic structure of G. aequilatera and showed a strong population structure in a species with a short planktonic larval stage.     

Geographic and temporal genetic structure in <Emphasis Type="Italic">Lepeophtheirus salmonis</Emphasis> from four salmon farms along the northwest and west coasts of Ireland: results from a microsatellite analysis

The marine ectoparasitic copepod of salmonids, Lepeophtheirus salmonis (Krøyer), is a major pest of farmed Atlantic salmon (Salmo salar L.) causing great economic impact. The spatial scales over which L. salmonis populations in different salmon farms are typically connected, and the temporal scales over which L. salmonis from the same farm typically undergo genetic change are largely unknown. These questions were posed in a small-scale geographic study of population structure in L. salmonis from four salmon farms, along the northwest and west coasts of Ireland, using two outgroups from Norway and Canada. The temporal stability of genetic composition was also studied in samples collected quarterly during one year from one salmon farm in Ireland. Genetic composition in L. salmonis was characterised using four nuclear microsatellites. Significant but low genetic differentiation was observed between all sites (F _ST = 0.08), with no evidence that differentiation was correlated with geographic distance. Temporal genetic differentiation was also evident (F _ST = 0.07). An analysis of all L. salmonis samples except the ones from Norway detected two separate clusters. Each cluster contained both geographical and temporal samples. These results are consistent with a population model in which L. salmonis in salmon farms along the northwest and west coasts of Ireland are not isolated, but are potentially subject to (i) localised ecological factors at the particular farm sites or (ii) selection post-settlement or a combination thereof.     

Conditions of reproduction and population dynamics of Pacific salmons (<Emphasis Type="Italic">Oncorhynchus</Emphasis>): The northeast of Sakhalin Island

The efficiency of reproduction of Pacific salmon (Oncorhynchus) in the rivers of the northeastern Sakhalin coast is characterized based on long-term observations. The rivers of the northern, central, and southern parts differ in the type of their channel, faunistic composition of aquatic biota, and prevalent salmon species. The northern rivers have a plain type of channel with rather low spawning efficiency of salmons and relatively poor freshwater ichthyofauna. The central area houses the largest rivers (Tym’ and Nabil’ Rivers) running to the Nyiskii and Nabil’skii Gulfs; the rivers there have developed channels of a plain type, high diversity of resident ichthyofauna, low spawning efficiency of the pink salmon Oncorhynchus gorbuscha, and high (in the past) abundance of the fall chum salmon O. keta. Characteristic of the southern rivers with their prevalently mountain–foothill type of channels are poor fish population and high spawning efficiency of the pink salmon. The population dynamics of the salmonids in the northeastern coast of Sakhalin is described. The total number of breeders entering the rivers of the northeastern coast that provides an efficient reproduction is estimated as 3.5?9.0 million individuals for the pink salmon and 0.04–0.60 million individuals for the chum salmon (fall race).     

Population genetic diversity and geographical differentiation of MHC class II DAB genes in the vulnerable Chinese egret (<Emphasis Type="Italic">Egretta eulophotes</Emphasis>)

Major histocompatibility complex (MHC) genes are excellent markers for the study of adaptive genetic variation occurring over different geographical scales. The Chinese egret (Egretta eulophotes) is a vulnerable ardeid species with an estimated global population of 2600–3400 individuals. In this study, we sampled 172 individuals of this egret (approximately 6 % of the global population) from five natural populations that span the entire distribution range of this species in China. We examined their population genetic diversity and geographical differentiation at three MHC class II DAB genes by identifying eight exon 2 alleles at Egeu-DAB1, eight at Egeu-DAB2 and four at Egeu-DAB3. Allelic distributions at each of these three Egeu-DAB loci varied substantially within the five populations, while levels of genetic diversity varied slightly among the populations. Analysis of molecular variance showed low but significant genetic differentiation among five populations at all three Egeu-DAB loci (haplotype-based ?_ST: 0.029, 0.020 and 0.042; and distance-based ?_ST: 0.036, 0.027 and 0.043, respectively; all P < 0.01). The Mantel test suggested that this significant population genetic differentiation was likely due to an isolation-by-distance pattern of MHC evolution. However, the phylogenetic analyses and the Bayesian clustering analysis based on the three Egeu-DAB loci indicated that there was little geographical structuring of the genetic differentiation among five populations. These results provide fundamental population information for the conservation genetics of the vulnerable Chinese egret.