Differentiation of Salvelinus malma charr and Taranetz Charr Salvelinus taranetzi from PCR-RFLP analysis of mitochondrial DNA

Genetic differentiation of two sympatric charr species, the Dolly Varden charr (Salvelinus malma Walbaum) and the Taranetz charr (S. taranetzi Kaganovski), has been studied. Restriction fragment length polymorphism (RFLP) analysis has been used to compare three mitochondrial DNA (mtDNA) fragments (ND1/ND2, ND5/ND6, and Cytb/D-loop) amplified via polymerase chain reaction (PCR). The divergence between S. malma and S. taranetzi inferred from mtDNA nucleotide sequences is 2.8%; between S. leucomaenis and S. taranetzi, 7.1%; and between S. malma and S. leucomaenis, 7.5%. The absence of common haplotypes and the degree of divergence indicate that the Dolly Varden charr and the Taranetz charr are genetically isolated and confirm that S. taranetzi may be regarded as a separate species.     

Genetic divergence of sympatric charrs of the genus Salvelinus from Nachikinskoe Lake (Kamchatka)

We studied genetic differentiation of two charr species, Dolly Varden Salvelinus malma malma Walbaum and resident lacustrine charr Salvelinus sp., which sympatrically inhabit Nachikinskoe Lake (the Bol'shaya River basin) in southwestern Kamchatka Peninsula. Using restriction analysis (RFLP), three mitochondrial DNA fragments (ND1/ND2, ND5/ND6, and Cytb/D loop) amplified in polymerase chain reaction (PCR) were compared. The divergence of the mtDNA sequences between Salvelinus sp. and S. malma malma was 2.8%; Salvelinus sp. and S. taranetzi, 0.36%; Salvelinus sp. and S. krogiusae, 0.21%; Salvelinus sp. and S. alpinus, 3.0%. These results point to reproductive isolation of charrs in Nachikinskoe Lake and support the earlier suggestion on a close relationship between Salvelinus sp., S. taranetzi, and S. krogiusae.     

Genetic Differentiation of Three Sympatric Charr Species from the Genus SalvelinusInferred from PCR–RFLP Analysis of Mitochondrial DNA

We examined differentiation of three sympatric charr species Dolly Varden charr Salvelinus malmaWalbaum, white-spotted charrS.leucomaenisPallas, and Levanidov charrS. levanidovi Chereshnev, Scopetz, Gudkov. Using restriction fragment length polymorphism analysis (RFLP), three mitochondrial DNA fragments (ND1/ND2, ND5/ND6, and Cytb/D-loop) amplified in PCR were compared. The divergence of mtDNA nucleotide sequences betweenS. levanidovi and S. leucomaenis was about 9.7%, between S. levanidovi and S. malma, 8.7%, and between S. malma andS. laecomaenis, 7.5%. These results indicate genetic isolation of the species examined and support the earlier suggestion on closeness of Levanidov charr to the common ancestor of the genus Salvelinus.     

Genetic divergence of sympatric charrs of the genus <Emphasis Type="Italic">Salvelinus</Emphasis> from Nachikinskoe Lake (Kamchatka)

We studied genetic differentiation of two charr species, Dolly Varden Salvelinus malma malma Walbaum and resident lacustrine charr Salvelinus sp., which sympatrically inhabit Nachikinskoe Lake (the Bol’shaya River basin) in southwestern Kamchatka Peninsula. Using restriction analysis (RFLP), three mitochondrial DNA fragments (ND1/ND2, ND5/ND6, and Cyt b/D-loop) amplified in polymerase chain reaction (PCR) were compared. The divergence of the mtDNA sequences between Salvelinus sp. and S. malma malma was 2.8%; Salvelinus sp. and S. taranetzi, 0.36%; Salvelinus sp. and S. krogiusae, 0.21%; Salvelinus sp. and S. alpinus, 3.0%. These results point to reproductive isolation of charrs in Nachikinskoe Lake and support the earlier suggestion on a close relationship between Salvelinus sp., S. taranetzi, and S. krogiusae.     

Genetic differentiation of charrs in the Russian north and far east

Genetic differences and relationships within charrs Salvelinus alpinus , northern and southern S. malma, S. taranetzi, S. levanidovi and S. leucomaenis , were studied by examination of 31–35 allozyme loci and PCR-RFLP analysis of mtDNA segment (about 2600 bp) including the cytochrome b gene and D-loop. Data for mtDNA were also obtained for samples of S. drjagini, S. albus and for European samples of S. alpinus. Generally allozyme and mtDNA segment analyses produced similar pictures of genetic divergence and relationships. The southern S. malma exhibited the greatest genetic variability (allozyme heterozygosity and mtDNA haplotype diversity). S. alpinus, S. malma, S. levanidovi and S. leucomaenis had fixed differences from one another at various allozyme loci, and differed in fixed (but polymorphic in S. malma ) individual mtDNA haplotypes produced with MspI restrictase. Such genetic individuality is typical of distinct taxa. S. taranetzi is closest genetically to allopatric S. alpinus , but exhibited fixed differences from the northern S. malma in sympatry. In all samples of S. alpinus the only mtDNA haplotype was shared with S. drjagini. S. albus shared its single haplotype with the northern S. malma from the same locality. S. leucomaenis is differentiated from the other species to the greatest extent, possibly reflecting an early evolutionary divergence. Some evolutionary and taxonomic implications of the genetic relationships of charrs studied are discussed.     

Phylogenetic relationships of Sakhalin taimen Parahucho perryi inferred from PCR-RFLP analysis of mitochondrial DNA

RFLP analysis of three amplified mtDNA fragments (Cytb/D-loop, ND1/ND2, and ND3/ND4L/ND4) was performed in the following taxa: Parahucho perryi, Hucho taimen, Brachymystax lenok, B. tumensis, Salmo salar, Salvelinus leucomaenis, and S. levanidovi. For mtDNA of P. perryi, a substantial decrease in the haplotype and nucleotide diversity was observed as a result of random genetic drift, caused by a reduction in the effective population size. Nucleotide divergence estimates between the mtDNA haplotypes were determined. Sakhalin taimen P. perryi was found to be approximately equally diverged from S. salar and from the charrs of the genus Salvelinus, by 11.0 and 10.0%, respectively. The divergence between P. perryi and H. taimen constituted 14.6%, between P. perryi and lenoks of the genus Brachymystax, 14.2%, and between H. taimen and Brachymystax, 7.7%. The analysis of possible phylogenetic relationships of the mtDNA from P. perryi among the group of taxa examined confirmed validity of the genus Parahucho. Phylogenetic reconstructions performed showed that robustness of the trees constructed for the complex of phylogenetically informative characters over three mtDNA fragments was considerably higher than that of the trees constructed for individual genes.     

Introgressive hybridization off chars of the genus Salvelinus as inferred from mitocchondrial DNA variation

Nucleotide sequence analysis of the mitochondrial cyttochrome b gene in the genus Salvelinus revealed hybrids with S. leucomaenis in S. malma malma populations ofthe Northern Okhotsk Sea basin. Hybrids of S. m. malma and S. m. krascheninnikovi were found in S. m. malma populations from the Northern Okhotsk Sea basin and Kamchatka. The findings testify to a secondary contact and mtDNA transfer between these species and forms. It was assumed that introgressive hybridization took place both long ago and relatively recently and occurred in one direction: from S. leucomaenis or S. m. krascheninnikovi to S. m. malma.     

Potential fragmentation and loss of thermal habitats for charrs in the Japanese archipelago due to climatic warming

1. The upper thermal limits of the present distributions of two charr species, Dolly Varden, Salvelinus malma , and white-spotted charr, S. leucomaenis , in streams of the Japanese archipelago were examined using groundwater temperature as an index of thermal condition. The lower limits of the altitudinal distributions of Dolly Varden and white-spotted charr were delineated, respectively, by 8 and 16 °C groundwater isotherms.
2. The potential impact of future climatic warming on the geographical distribution, habitat extent and population fragmentation of each species was predicted at both the full archipelago and individual catchment levels.
3. For Dolly Varden, analysis at the full archipelago level indicated a loss of 27.6, 67.2, 79.6 and 89.6% of the current geographical range, respectively, for a 1, 2, 3 and 4 °C increase in mean annual air temperature. The present distribution area of white-spotted charr would likewise reduce by 4.1, 20.5, 33.8 and 45.6%, respectively.
4. Based on the analyses of three individual catchments, one for Dolly Varden and two for white-spotted charr, the lower habitat boundaries for the two charr species could be expected to rise increasingly to higher elevations in each catchment as warming proceeded. As a consequence, there would be large reductions in mean habitat area, with increasing habitat fragmentation followed by localized extinctions of the two species.     

Potential fragmentation and loss of thermal habitats for charrs in the Japanese archipelago due to climatic warming

1. The upper thermal limits of the present distributions of two charr species, Dolly Varden, Salvelinus malma , and white-spotted charr, S. leucomaenis , in streams of the Japanese archipelago were examined using groundwater temperature as an index of thermal condition. The lower limits of the altitudinal distributions of Dolly Varden and white-spotted charr were delineated, respectively, by 8 and 16 °C groundwater isotherms.
2. The potential impact of future climatic warming on the geographical distribution, habitat extent and population fragmentation of each species was predicted at both the full archipelago and individual catchment levels.
3. For Dolly Varden, analysis at the full archipelago level indicated a loss of 27.6, 67.2, 79.6 and 89.6% of the current geographical range, respectively, for a 1, 2, 3 and 4 °C increase in mean annual air temperature. The present distribution area of white-spotted charr would likewise reduce by 4.1, 20.5, 33.8 and 45.6%, respectively.
4. Based on the analyses of three individual catchments, one for Dolly Varden and two for white-spotted charr, the lower habitat boundaries for the two charr species could be expected to rise increasingly to higher elevations in each catchment as warming proceeded. As a consequence, there would be large reductions in mean habitat area, with increasing habitat fragmentation followed by localized extinctions of the two species.     

Evolutionary relationships of the salmonid fish genus Salvelinus inferred from DNA sequences of the first internal transcribed spacer (ITS 1) of ribosomal DNA.

DNA sequences of the ribosomal DNA (rDNA) first internal transcribed spacer region (ITS 1) of six species of the salmonid fish genus Salvelinus (alpinus, malma, confluentus, leucomaenis, fontinalis, and namaycush) and the closely related species Hucho perryi were determined. Phylogenetic analysis of the aligned sequences by both phenetic and cladistic methods with H. perryi as an outgroup generated one best topology which pairs S. alpinus with S. malma as the most recently derived species, and pairs S. confluentus with S. leucomaenis. Three other possible topologies favor the pairing of S. namaycush and S. fontinalis, with one tree placing them on separate branches, and vary the branching order of the interior groups. These results agree with previous studies based on comparisons of morphologies, isozymes, karyotypes, and restriction sites showing a close genetic relationship and possible hybridization between the members of this genus.     

Population genetic structure of northern Dolly Varden char Salvelinus malma malma in Asia and North America

The level of genetic differentiation of northern Dolly Varden char Salvelinus malma malma from Asia and North America was evaluated using the data on mtDNA variation (regions ND1/ND2, ND5/ND6, and Cytb/D loop) obtained by means of PCR-RFLP analysis. For S. m. malma, the mean values of haplotype and nucleotide diversity were 0.5261 +/- 0.00388 and 0.001558, respectively. The mean estimate of the population nucleotide divergence constituted 0.055%. It was demonstrated that S. m. malma on the most part of the species range examined (drainages of the Beaufort Sea, Chukotka Sea, Bering Sea, and the Sea of Okhotsk) was characterized by the population genetic structure with the low level of genetic differentiation and divergence. At the same time, populations from the Pacific Ocean Gulf of Alaska demonstrated marked genetic differentiation, supported by the high pairwise phi(ST) values (from 0.4198 to 0.5211) and nucleotide divergence estimates (mean divergence, 0.129%), from Asian and North American populations. Nested analysis of molecular variance (AMOVA) showed that most of the mtDNA variation in S. m. malma fell in the intrapopulation component (72.5%). At the same time, the differences between the populations (21.1%) and between the regions (6.4%) made lower contribution to the total variation.     

A Rare Case of Permanent Introgressive Hybridization in Char of the Genus Salvelinus (Salmonidae: Salmoniformes) in the Utkholok River,Western Kamchatka

Russian Journal of Marine Biology - Hybrids between the whitespotted char Salvelinus leucomaenis and the northern Dolly Varden S.&nbsp;malma malma have been found to regularly occur and exist...     

The divergence of the dolly varden char Salvelinus malma in Asian Northern Pacific populations inferred from the PCR-RFLP analysis of the mitochondrial DNA

Genetic differentiation of the dolly varden char Salvelinus malma Walbaum was studied in five populations from the western part of the Northern Pacific. Using restriction analysis (RFLP), we examined polymorphism of three mitochondrial DNA (mtDNA) fragments amplified in polymerase chain reaction (PCR). MtDNA haplotypes were shown to fall into two phylogenetic groups, which probably reflect the existence of two previously described subspecies of Asian dolly varden, S. malma malma and S. malma krascheninnikovi. The divergence of mtDNA nucleotide sequences in the dolly varden subspecies (about 4%) corresponds to the differences between the valid char species from the genus Salvelinus.     

Evidence for interspecific hybridization between native white-spotted charr Salvelinus leucomaenis and non-native brown trout Salmo trutta on Hokkaido Island, Japan

Hybrids between native white-spotted charr Salvelinus leucomaenis and non-native brown trout Salmo trutta were identified in streams of Hokkaido, Japan, using both appearance and genetic characters. The DNA analyses indicated that the specimens were hybrids between female S. leucomaenis and male S. trutta . Occurrence of such hybrids implies increased mating opportunities between these species in wild streams.     

Occurrence of a hybrid between endemic Miyabe charr Salvelinus malma miyabei and introduced masu salmon Oncorhynchus masou masou in the Lake Shikaribetsu system, Hokkaido, Japan

A hybrid specimen between endemic Miyabe charr Salvelinus malma miyabei and introduced masu salmon Oncorhynchus masou masou was collected in an inlet stream (Yamada Creek) of the Lake Shikaribetsu. This specimen showed intermediate external characteristics between two species and was also confirmed as a hybrid by DNA markers. The mtDNA of the specimen was identical with that of S. malma miyabei, suggesting that the mating occurred between a female Miyabe charr and a male masu salmon. Hybridization with introduced masu salmon may cause deleterious effects on S. malma miyabei.     

Differentiation of Dolly Varden char Salvelinus malma from Asia and North America inferred from PCR-RFLP analysis of mitochondrial DNA

Genetic differentiation of Dolly Varden char Salvelinus malma Walbaum from the Asian and North American Pacific coasts was studied. We examined restriction fragment length polymorphism of three mitochondrial DNA (mtDNA) fragments amplified in polymerase chain reaction, which encoded four NADH dehydrogenase subunits, the cytochrome b gene, and a D-loop segment. The mtDNA haplotypes were shown to form three phylogenetic groups, whose geographic distribution corresponded to three Dolly Varden subspecies: S. malma malma, S. malma krascheninnikovi, and S. malma lordi. The nucleotide sequence divergence between S. malma malma and S. malma krascheninnikovi was 3.8%; between S. malma malma and S. malma lordi, 3.1%; and between S. malma krascheninnikovi and S. malma lordi, 2.5%. The northern Dolly Varden S. malma malma from Asia was shown to be genetically identical to that from North America.     

Introgressive hybridization between Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis on Hokkaido Island, Japan

Intra‐ and interspecific phylogenetic analysis of Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis throughout Hokkaido Island was conducted using nucleotide sequences of the mitochondrial DNA control region and three nuclear DNA markers [ribosomal DNA (ITS‐1), microsatellite ( u ‐85), SINE ( Fok ‐223)]. A total of 19 mtDNA haplotypes from 271 individuals of Dolly Varden, nine haplotypes from 134 white‐spotted charr were defined, and identified two well‐supported monophyletic clades for each species. Two haplotypes of Dolly Varden, however, were clustered together in the white‐spotted charr clade. Those haplotypes were found only from several rivers in the Shiretoko Peninsula, and a neighbouring river of that region. Analyses of ribosomal DNA and Fok ‐223 loci revealed that both species are characterized by having completely species‐specific diagnostic sequence and fragment patterns. Dolly Varden of the Shiretoko populations are typically allopatric in distribution where white‐spotted charr do not currently occur. In addition, incongruence in genetic relationships between mtDNA and nuclear DNA markers give strong evidence of historical mtDNA introgression between Dolly Varden and white‐spotted charr. Some white‐spotted charr diagnostic alleles in a nuclear microsatellite locus ( u ‐85) were found in some Shiretoko Dolly Varden populations, suggesting that introgressive hybridization might have also occurred in relatively recent contact and potentially ongoing evolutionary event. The present study presents an example of historical hybridization and introgression at the southernmost distribution limits of Dolly Varden.     

Change in nucleotide sequence of mitochondrial DNA from cytochrome b gene in chars of Salvelinus genus

Nucleotide sequences of two (405- and 1050-bp) regions of mitochondrial DNA (mtDNA) cytochrome c gene were established in chars of the genus Salvelinus from Russian Far East and Siberia. Based on the divergence and phylogenetic analysis of nucleotide sequences of the mtDNA cytochrome c gene, S. laecomaenis was shown to carry the most ancient mitochondrial lineage, which is close to the ancestral one. The archaic mtDNA of S. levanidovi occupied an isolated position on the phylogenetic trees. The mtDNA lineage of the southern S. malma was close to the S. alpinus-S. malma complex group. Within the S. alpinus-S. malma complex, three groups of mtDNA types having particular geographic distributions were distinguished. The Kolyma-Chukotka group includes lake S. taranetzi, S. boganidae and S. elgyticus from Chukotka, lake chars from Kolyma. The Okhotsk group is represented by northern S. malma, lake chars from northern Sea of Okhotsk, and anadromous S. taranetzi. The Siberian group is close to the Okhotsk one and consists of Taimyr and Baikal region chars as well as Arctic char from Finland. The divergence of char mitochondrial lineages was dated to the Pliocene-Pleistocene.     

Evidence of multiple migrations between freshwater and marine habitats of Salvelinus leucomaenis

The migratory history of the white‐spotted charr Salvelinus leucomaenis was examined using otolith microchemical analysis. The fish migrated between freshwater and marine environments multiple times during their life history. Some white‐spotted charr used an estuarine habitat prior to smolting and repeated seaward migration within a year.     

Phylogeography of mitochondrial DNA in South Asian Dolly Varden char Salvelinus curilus Pallas, 1814 (Salmoniformes, Salmonidae): mediated gene introgression?

In 41 individuals of South Asian Dolly Varden char Salvelinus curilus, nucleotide sequences of tRNA-Pro gene fragment (27 bp) and mtDNA control region (483-484 bp) were analyzed. The fish were collected in 20 localities covering virtually the whole range of the species: Kuril Islands, Sakhalin Island. and Primorye. In addition, six individuals of three other char species (S. albus, S. malma, and S. leucomaenis), which are closely related to S. curilus and inhabit the Russian Far East, were examined. In all, we detected 12 different variants of mtDNA haplotypes that formed three distinct groups differing in 14--20 nucleotide positions. The first group consisted of six haplotypes found in S. curilus in Kuril Islands, Sakhalin, and Primorye (mtDNA phylogroup OKHOTSKIA). The second group comprised four haplotypes representing the mtDNA phylogroup BERING, which had been described earlier (Brunner et al, 2001); they were found in S. curilus in Kuril Islands and Sakhalin, as well as in S. albus and S. malma in Kamchatka and northern Kurils. The third group included two haplotypes detected in S. leucomaenis. The existence of two mtDNA lineages (OKHOTSKIA and BERING) in S. curilus from Kurils and Sakhalin was explained by hybridization and DNA transfer from S. malma to S. curilus. The absence of the BERING haplotypes in S. curilus from Primorye water reservoirs is related to the physical isolation of the Sea of Okhotsk and Sea of Japan basins in past epochs. On the basis of comparing phylogenetic trees, constructed from the data on allozyme and mtDNA variation, we suggest that in this case, an indirect transfer of mtDNA in Alpinoid chars--> S. malma-->S. curilus chain could occur.