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Land-bridge calibration of molecular clocks and the post-glacial Colonization of Scandinavia by the Eurasian field vole Microtus agrestis.

Herman JS, McDevitt AD, Kawałko A, Jaarola M, Wójcik JM, Searle JB - PLoS ONE (2014)

Bottom Line: The mitochondrial substitution rate and the timescale for the genealogy are closely consistent with those obtained with a previous calibration, based on the separation of the British Isles from mainland Europe.However the result here is arguably more certain, given the level of confidence that can be placed in one of the central assumptions of the calibration, that field voles could not survive the last glaciation of the southern part of the Scandinavian peninsula.Furthermore, the similarity between the molecular clock rate estimated here and those obtained by sampling heterochronous (ancient) DNA (including that of a congeneric species) suggest that there is little disparity between the measured genetic divergence and the population divergence that is implicit in our land-bridge calibration.

View Article: PubMed Central - PubMed

Affiliation: Department of Natural Sciences, National Museums Scotland, Edinburgh, United Kingdom.

ABSTRACT
Phylogeography interprets molecular genetic variation in a spatial and temporal context. Molecular clocks are frequently used to calibrate phylogeographic analyses, however there is mounting evidence that molecular rates decay over the relevant timescales. It is therefore essential that an appropriate rate is determined, consistent with the temporal scale of the specific analysis. This can be achieved by using temporally spaced data such as ancient DNA or by relating the divergence of lineages directly to contemporaneous external events of known time. Here we calibrate a Eurasian field vole (Microtus agrestis) mitochondrial genealogy from the well-established series of post-glacial geophysical changes that led to the formation of the Baltic Sea and the separation of the Scandinavian peninsula from the central European mainland. The field vole exhibits the common phylogeographic pattern of Scandinavian colonization from both the north and the south, however the southernmost of the two relevant lineages appears to have originated in situ on the Scandinavian peninsula, or possibly in the adjacent island of Zealand, around the close of the Younger Dryas. The mitochondrial substitution rate and the timescale for the genealogy are closely consistent with those obtained with a previous calibration, based on the separation of the British Isles from mainland Europe. However the result here is arguably more certain, given the level of confidence that can be placed in one of the central assumptions of the calibration, that field voles could not survive the last glaciation of the southern part of the Scandinavian peninsula. Furthermore, the similarity between the molecular clock rate estimated here and those obtained by sampling heterochronous (ancient) DNA (including that of a congeneric species) suggest that there is little disparity between the measured genetic divergence and the population divergence that is implicit in our land-bridge calibration.

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Related in: MedlinePlus

Field vole mitochondrial cytochrome b genealogy.Maximum clade credibility tree from Bayesian coalescent modelling with 441 sequences, clade support from posterior probability of node. Clades collapsed for clarity and gray bars show 95% highest posterior density intervals for tMRCA of each lineage.
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pone-0103949-g002: Field vole mitochondrial cytochrome b genealogy.Maximum clade credibility tree from Bayesian coalescent modelling with 441 sequences, clade support from posterior probability of node. Clades collapsed for clarity and gray bars show 95% highest posterior density intervals for tMRCA of each lineage.

Mentions: The 441 cytochrome b sequences were grouped into six well-supported lineages (Figure 2), named as eastern, Scandinavia, central Europe, France, north Britain and western following the previous results of Herman and Searle [13]. The new sequences from southern Scandinavia all belong to the previously-described lineage and no sequences from the Scandinavia clade were found in mainland Europe, despite substantial numbers of samples obtained there (Figure 3). The restricted distribution of the Scandinavia clade is of course critical to our land-bridge calibration of the genealogy.


Land-bridge calibration of molecular clocks and the post-glacial Colonization of Scandinavia by the Eurasian field vole Microtus agrestis.

Herman JS, McDevitt AD, Kawałko A, Jaarola M, Wójcik JM, Searle JB - PLoS ONE (2014)

Field vole mitochondrial cytochrome b genealogy.Maximum clade credibility tree from Bayesian coalescent modelling with 441 sequences, clade support from posterior probability of node. Clades collapsed for clarity and gray bars show 95% highest posterior density intervals for tMRCA of each lineage.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128820&req=5

pone-0103949-g002: Field vole mitochondrial cytochrome b genealogy.Maximum clade credibility tree from Bayesian coalescent modelling with 441 sequences, clade support from posterior probability of node. Clades collapsed for clarity and gray bars show 95% highest posterior density intervals for tMRCA of each lineage.
Mentions: The 441 cytochrome b sequences were grouped into six well-supported lineages (Figure 2), named as eastern, Scandinavia, central Europe, France, north Britain and western following the previous results of Herman and Searle [13]. The new sequences from southern Scandinavia all belong to the previously-described lineage and no sequences from the Scandinavia clade were found in mainland Europe, despite substantial numbers of samples obtained there (Figure 3). The restricted distribution of the Scandinavia clade is of course critical to our land-bridge calibration of the genealogy.

Bottom Line: The mitochondrial substitution rate and the timescale for the genealogy are closely consistent with those obtained with a previous calibration, based on the separation of the British Isles from mainland Europe.However the result here is arguably more certain, given the level of confidence that can be placed in one of the central assumptions of the calibration, that field voles could not survive the last glaciation of the southern part of the Scandinavian peninsula.Furthermore, the similarity between the molecular clock rate estimated here and those obtained by sampling heterochronous (ancient) DNA (including that of a congeneric species) suggest that there is little disparity between the measured genetic divergence and the population divergence that is implicit in our land-bridge calibration.

View Article: PubMed Central - PubMed

Affiliation: Department of Natural Sciences, National Museums Scotland, Edinburgh, United Kingdom.

ABSTRACT
Phylogeography interprets molecular genetic variation in a spatial and temporal context. Molecular clocks are frequently used to calibrate phylogeographic analyses, however there is mounting evidence that molecular rates decay over the relevant timescales. It is therefore essential that an appropriate rate is determined, consistent with the temporal scale of the specific analysis. This can be achieved by using temporally spaced data such as ancient DNA or by relating the divergence of lineages directly to contemporaneous external events of known time. Here we calibrate a Eurasian field vole (Microtus agrestis) mitochondrial genealogy from the well-established series of post-glacial geophysical changes that led to the formation of the Baltic Sea and the separation of the Scandinavian peninsula from the central European mainland. The field vole exhibits the common phylogeographic pattern of Scandinavian colonization from both the north and the south, however the southernmost of the two relevant lineages appears to have originated in situ on the Scandinavian peninsula, or possibly in the adjacent island of Zealand, around the close of the Younger Dryas. The mitochondrial substitution rate and the timescale for the genealogy are closely consistent with those obtained with a previous calibration, based on the separation of the British Isles from mainland Europe. However the result here is arguably more certain, given the level of confidence that can be placed in one of the central assumptions of the calibration, that field voles could not survive the last glaciation of the southern part of the Scandinavian peninsula. Furthermore, the similarity between the molecular clock rate estimated here and those obtained by sampling heterochronous (ancient) DNA (including that of a congeneric species) suggest that there is little disparity between the measured genetic divergence and the population divergence that is implicit in our land-bridge calibration.

Show MeSH
Related in: MedlinePlus