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The evolutionary history of sharp- and blunt-snouted lenok (Brachymystax lenok (Pallas, 1773)) and its implications for the paleo-hydrological history of Siberia.

Froufe E, Alekseyev S, Alexandrino P, Weiss S - BMC Evol. Biol. (2008)

Bottom Line: Evidence for repeated trans-basin exchange was especially clear between the Amur and Lena catchments.Sharp- and blunt-snouted lenok have apparently undergone a long, independent, and demographically dynamic evolutionary history in Siberia, supporting their recognition as two good biological species.Considering the timing and extent of expansions and trans-basin dispersal, it is doubtful that these historical dynamics could have been generated without major rearrangements in the paleo-hydrological network, stemming from the formation and melting of large-scale glacial complexes much older than the LGM.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centro de Investigação em Biodiversidade e Recursos Genéticos (CIBIO/UP), Campus Agrário de Vairão, 4485-661 Vairão, Portugal. elsafrouf@mail.icav.up.pt

ABSTRACT

Background: Broad-scale phylogeographic studies of freshwater organisms provide not only an invaluable framework for understanding the evolutionary history of species, but also a genetic imprint of the paleo-hydrological dynamics stemming from climatic change. Few such studies have been carried out in Siberia, a vast region over which the extent of Pleistocene glaciation is still disputed. Brachymystax lenok is a salmonid fish distributed throughout Siberia, exhibiting two forms hypothesized to have undergone extensive range expansion, genetic exchange, and multiple speciation. A comprehensive phylogeographic investigation should clarify these hypotheses as well as provide insights on Siberia's paleo-hydrological stability.

Results: Molecular-sequence (mtDNA) based phylogenetic and morphological analysis of Brachymystax throughout Siberia support that sharp- and blunt-snouted lenok are independent evolutionary lineages, with the majority of their variation distributed among major river basins. Their evolutionary independence was further supported through the analysis of 11 microsatellite loci in three areas of sympatry, which revealed little to no evidence of introgression. Phylogeographic structure reflects climatic limitations, especially for blunt-snouted lenok above 56 degrees N during one or more glacial maxima. Presumed glacial refugia as well as interbasin exchange were not congruent for the two lineages, perhaps reflecting differing dispersal abilities and response to climatic change. Inferred demographic expansions were dated earlier than the Last Glacial Maximum (LGM). Evidence for repeated trans-basin exchange was especially clear between the Amur and Lena catchments. Divergence of sharp-snouted lenok in the Selenga-Baikal catchment may correspond to the isolation of Lake Baikal in the mid-Pleistocene, while older isolation events are apparent for blunt-snouted lenok in the extreme east and sharp-snouted lenok in the extreme west of their respective distributions.

Conclusion: Sharp- and blunt-snouted lenok have apparently undergone a long, independent, and demographically dynamic evolutionary history in Siberia, supporting their recognition as two good biological species. Considering the timing and extent of expansions and trans-basin dispersal, it is doubtful that these historical dynamics could have been generated without major rearrangements in the paleo-hydrological network, stemming from the formation and melting of large-scale glacial complexes much older than the LGM.

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ML tree based on CR and ND1 sequences. Tree derived from a ML search using the Tamura-Nei model (TRN+G+I) for the CR and ND1 sequences combined. All analyses (NJ, MP, and ML) gave similar estimates of relationships. For the major clades, bootstrap values (over 50%) are shown for ML (above); MP (with gaps) (below, left) and NJ (below, right). 100*means that all bootstrap values are higher than 95. The tree is rooted with H. hucho, H. taimen and P. perryi.
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Figure 2: ML tree based on CR and ND1 sequences. Tree derived from a ML search using the Tamura-Nei model (TRN+G+I) for the CR and ND1 sequences combined. All analyses (NJ, MP, and ML) gave similar estimates of relationships. For the major clades, bootstrap values (over 50%) are shown for ML (above); MP (with gaps) (below, left) and NJ (below, right). 100*means that all bootstrap values are higher than 95. The tree is rooted with H. hucho, H. taimen and P. perryi.

Mentions: The final alignment included 494 bp of the mtDNA control region (CR) (N = 151), 987 bp of the NADH-1 gene (ND1) (N = 142), and 1481 bp (N = 114) with both genes combined. There was no significant deviation from base frequency homogeneity across taxa for either gene. In lenok the transition/transversion ratio was 2.56 for the CR, which revealed one 2-bp and four 1-bp indels, with outgroup taxa included. For the coding ND1 there were no indels nor amino acid changes. Neither transitions nor transversions were saturated in either gene segment, including third codon positions. There were 33 variable sites for the CR, 30 of which were parsimony informative (excl. indels) and 208 variable sites (109 parsimony informative) for the ND1. Pairwise sequence divergence within B. lenok ranged from 0 to 3.0% (CR) to 0 to 6.2% (ND1). In all analyses two monophyletic groups are identified corresponding to blunt- and sharp-snouted lenoks (Figure 2). Net divergence between groups ranged from 1.7% (CR) to 4.7% (ND1), while within lineage divergences ranged from 0.2% to 0.7%. Net divergences between outgroup taxa and lenok varied with the two genes: 4.3% (CR) or 7.7% (ND1) for H. hucho, 5.4%(CR) or 7.4% (ND1) for H. taimen, and 7.6% (CR) or 13.3% (ND1) for P. perryi.


The evolutionary history of sharp- and blunt-snouted lenok (Brachymystax lenok (Pallas, 1773)) and its implications for the paleo-hydrological history of Siberia.

Froufe E, Alekseyev S, Alexandrino P, Weiss S - BMC Evol. Biol. (2008)

ML tree based on CR and ND1 sequences. Tree derived from a ML search using the Tamura-Nei model (TRN+G+I) for the CR and ND1 sequences combined. All analyses (NJ, MP, and ML) gave similar estimates of relationships. For the major clades, bootstrap values (over 50%) are shown for ML (above); MP (with gaps) (below, left) and NJ (below, right). 100*means that all bootstrap values are higher than 95. The tree is rooted with H. hucho, H. taimen and P. perryi.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2275220&req=5

Figure 2: ML tree based on CR and ND1 sequences. Tree derived from a ML search using the Tamura-Nei model (TRN+G+I) for the CR and ND1 sequences combined. All analyses (NJ, MP, and ML) gave similar estimates of relationships. For the major clades, bootstrap values (over 50%) are shown for ML (above); MP (with gaps) (below, left) and NJ (below, right). 100*means that all bootstrap values are higher than 95. The tree is rooted with H. hucho, H. taimen and P. perryi.
Mentions: The final alignment included 494 bp of the mtDNA control region (CR) (N = 151), 987 bp of the NADH-1 gene (ND1) (N = 142), and 1481 bp (N = 114) with both genes combined. There was no significant deviation from base frequency homogeneity across taxa for either gene. In lenok the transition/transversion ratio was 2.56 for the CR, which revealed one 2-bp and four 1-bp indels, with outgroup taxa included. For the coding ND1 there were no indels nor amino acid changes. Neither transitions nor transversions were saturated in either gene segment, including third codon positions. There were 33 variable sites for the CR, 30 of which were parsimony informative (excl. indels) and 208 variable sites (109 parsimony informative) for the ND1. Pairwise sequence divergence within B. lenok ranged from 0 to 3.0% (CR) to 0 to 6.2% (ND1). In all analyses two monophyletic groups are identified corresponding to blunt- and sharp-snouted lenoks (Figure 2). Net divergence between groups ranged from 1.7% (CR) to 4.7% (ND1), while within lineage divergences ranged from 0.2% to 0.7%. Net divergences between outgroup taxa and lenok varied with the two genes: 4.3% (CR) or 7.7% (ND1) for H. hucho, 5.4%(CR) or 7.4% (ND1) for H. taimen, and 7.6% (CR) or 13.3% (ND1) for P. perryi.

Bottom Line: Evidence for repeated trans-basin exchange was especially clear between the Amur and Lena catchments.Sharp- and blunt-snouted lenok have apparently undergone a long, independent, and demographically dynamic evolutionary history in Siberia, supporting their recognition as two good biological species.Considering the timing and extent of expansions and trans-basin dispersal, it is doubtful that these historical dynamics could have been generated without major rearrangements in the paleo-hydrological network, stemming from the formation and melting of large-scale glacial complexes much older than the LGM.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centro de Investigação em Biodiversidade e Recursos Genéticos (CIBIO/UP), Campus Agrário de Vairão, 4485-661 Vairão, Portugal. elsafrouf@mail.icav.up.pt

ABSTRACT

Background: Broad-scale phylogeographic studies of freshwater organisms provide not only an invaluable framework for understanding the evolutionary history of species, but also a genetic imprint of the paleo-hydrological dynamics stemming from climatic change. Few such studies have been carried out in Siberia, a vast region over which the extent of Pleistocene glaciation is still disputed. Brachymystax lenok is a salmonid fish distributed throughout Siberia, exhibiting two forms hypothesized to have undergone extensive range expansion, genetic exchange, and multiple speciation. A comprehensive phylogeographic investigation should clarify these hypotheses as well as provide insights on Siberia's paleo-hydrological stability.

Results: Molecular-sequence (mtDNA) based phylogenetic and morphological analysis of Brachymystax throughout Siberia support that sharp- and blunt-snouted lenok are independent evolutionary lineages, with the majority of their variation distributed among major river basins. Their evolutionary independence was further supported through the analysis of 11 microsatellite loci in three areas of sympatry, which revealed little to no evidence of introgression. Phylogeographic structure reflects climatic limitations, especially for blunt-snouted lenok above 56 degrees N during one or more glacial maxima. Presumed glacial refugia as well as interbasin exchange were not congruent for the two lineages, perhaps reflecting differing dispersal abilities and response to climatic change. Inferred demographic expansions were dated earlier than the Last Glacial Maximum (LGM). Evidence for repeated trans-basin exchange was especially clear between the Amur and Lena catchments. Divergence of sharp-snouted lenok in the Selenga-Baikal catchment may correspond to the isolation of Lake Baikal in the mid-Pleistocene, while older isolation events are apparent for blunt-snouted lenok in the extreme east and sharp-snouted lenok in the extreme west of their respective distributions.

Conclusion: Sharp- and blunt-snouted lenok have apparently undergone a long, independent, and demographically dynamic evolutionary history in Siberia, supporting their recognition as two good biological species. Considering the timing and extent of expansions and trans-basin dispersal, it is doubtful that these historical dynamics could have been generated without major rearrangements in the paleo-hydrological network, stemming from the formation and melting of large-scale glacial complexes much older than the LGM.

Show MeSH