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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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Coalescence estimates for the CR and ND1 genes. Coalescence estimates for the CR, based on τ and its 95% CI shown for a range (0.5%–3%) of divergence rates for (A) blunt-snouted and (B) sharp-snouted lenok. Coalescence estimates for the ND1 gene based on τ and its 95% CI shown for a range (1.5%–6%) of divergence rates for (C) blunt-snouted and (D) for sharp-snouted lenok.
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Figure 7: Coalescence estimates for the CR and ND1 genes. Coalescence estimates for the CR, based on τ and its 95% CI shown for a range (0.5%–3%) of divergence rates for (A) blunt-snouted and (B) sharp-snouted lenok. Coalescence estimates for the ND1 gene based on τ and its 95% CI shown for a range (1.5%–6%) of divergence rates for (C) blunt-snouted and (D) for sharp-snouted lenok.

Mentions: Using estimates for the expansion parameter tau, along with divergence rate estimates ranging from 0.5 to 3% per million years for the CR and 1.5 to 6% for the ND1, we estimated the mean age of expansion for both genes in both forms (Figure 7A–D). Mean estimates of expansion times, regardless of the gene or presumed substitution rate clearly relate to periods in the mid- to late Pleistocene (50,000 to 400,000 year ago) but in all cases earlier than the LGM (18,000 years ago).


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)

Coalescence estimates for the CR and ND1 genes. Coalescence estimates for the CR, based on τ and its 95% CI shown for a range (0.5%–3%) of divergence rates for (A) blunt-snouted and (B) sharp-snouted lenok. Coalescence estimates for the ND1 gene based on τ and its 95% CI shown for a range (1.5%–6%) of divergence rates for (C) blunt-snouted and (D) for sharp-snouted lenok.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Coalescence estimates for the CR and ND1 genes. Coalescence estimates for the CR, based on τ and its 95% CI shown for a range (0.5%–3%) of divergence rates for (A) blunt-snouted and (B) sharp-snouted lenok. Coalescence estimates for the ND1 gene based on τ and its 95% CI shown for a range (1.5%–6%) of divergence rates for (C) blunt-snouted and (D) for sharp-snouted lenok.
Mentions: Using estimates for the expansion parameter tau, along with divergence rate estimates ranging from 0.5 to 3% per million years for the CR and 1.5 to 6% for the ND1, we estimated the mean age of expansion for both genes in both forms (Figure 7A–D). Mean estimates of expansion times, regardless of the gene or presumed substitution rate clearly relate to periods in the mid- to late Pleistocene (50,000 to 400,000 year ago) but in all cases earlier than the LGM (18,000 years ago).

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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