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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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UPGMA dendrogram of external morphological and osteological characters. UPGMA dendrogram of lenok populations (N = 50) based on 46 external morphological and osteological characters. H. taimen is added to the analysis. Photograph of both sharp- and blunt-snouted lenoks’heads. Population numbers corresponding to those in Table 1 can be found in Additional File 11 and Additional file 12.
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Figure 3: UPGMA dendrogram of external morphological and osteological characters. UPGMA dendrogram of lenok populations (N = 50) based on 46 external morphological and osteological characters. H. taimen is added to the analysis. Photograph of both sharp- and blunt-snouted lenoks’heads. Population numbers corresponding to those in Table 1 can be found in Additional File 11 and Additional file 12.

Mentions: The phenogram based on external morphological and osteological characters parallels the genetic results revealing two clusters corresponding to sharp- and blunt-snouted lenoks (Figure 3). Similarly, a plot of the first two factors of a Principal Component Analysis (PCA) reveals two clusters clearly representing the two forms (Figure 4). Only the position of sharp-snouted lenok from the Ob basin, intermediate along the first factor (PC1) between blunt-snouted lenok and all other sharp-snouted individuals prevents 100% diagnosis of all individuals to a form. Size effects were assumed to be minimal as there was no correlation between PC1 and size (Additional File 2) and mean total length of individuals analyzed in both forms was nearly identical (sharp-snouted 41.2 cm; blunt-snouted 41.6 cm). Application of a Discriminant Function (DF) produced from a 25% random sample of the data set resulted in 99.9% and 99.6% correct identification for the blunt- and sharp-snouted lenok, respectively. DF values for the misclassified individuals (two Ob basin sharps and 5 Primor'e region blunts) were intermediate to the ranges of values defining each form.


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)

UPGMA dendrogram of external morphological and osteological characters. UPGMA dendrogram of lenok populations (N = 50) based on 46 external morphological and osteological characters. H. taimen is added to the analysis. Photograph of both sharp- and blunt-snouted lenoks’heads. Population numbers corresponding to those in Table 1 can be found in Additional File 11 and Additional file 12.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: UPGMA dendrogram of external morphological and osteological characters. UPGMA dendrogram of lenok populations (N = 50) based on 46 external morphological and osteological characters. H. taimen is added to the analysis. Photograph of both sharp- and blunt-snouted lenoks’heads. Population numbers corresponding to those in Table 1 can be found in Additional File 11 and Additional file 12.
Mentions: The phenogram based on external morphological and osteological characters parallels the genetic results revealing two clusters corresponding to sharp- and blunt-snouted lenoks (Figure 3). Similarly, a plot of the first two factors of a Principal Component Analysis (PCA) reveals two clusters clearly representing the two forms (Figure 4). Only the position of sharp-snouted lenok from the Ob basin, intermediate along the first factor (PC1) between blunt-snouted lenok and all other sharp-snouted individuals prevents 100% diagnosis of all individuals to a form. Size effects were assumed to be minimal as there was no correlation between PC1 and size (Additional File 2) and mean total length of individuals analyzed in both forms was nearly identical (sharp-snouted 41.2 cm; blunt-snouted 41.6 cm). Application of a Discriminant Function (DF) produced from a 25% random sample of the data set resulted in 99.9% and 99.6% correct identification for the blunt- and sharp-snouted lenok, respectively. DF values for the misclassified individuals (two Ob basin sharps and 5 Primor'e region blunts) were intermediate to the ranges of values defining each form.

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