Land-bridge calibration of molecular clocks and the post-glacial colonization of Scandinavia by the Eurasian field vole microtus agrestis

Herman, JS.; McDevitt, A; Kawałko, A; Jaarola, M; Wójcik, JM; Searle, JB

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.

Citation

Herman, J., McDevitt, A., Kawałko, A., Jaarola, M., Wójcik, J., & Searle, J. (2014). Land-bridge calibration of molecular clocks and the post-glacial colonization of Scandinavia by the Eurasian field vole microtus agrestis. PLoS ONE, 9(8), e103949. https://doi.org/10.1371/journal.pone.0103949

• Journal Article Type: Article
• Acceptance Date: Jul 3, 2014
• Publication Date: Aug 11, 2014
• Deposit Date: Jan 25, 2016
• Publicly Available Date: Apr 5, 2016
• Journal: PLoS ONE
• Electronic ISSN: 1932-6203
• Publisher: Public Library of Science
• Volume: 9
• Issue: 8
• Pages: e103949
• DOI: https://doi.org/10.1371/journal.pone.0103949
• Publisher URL: http://dx.doi.org/10.1371/journal.pone.0103949
• Related Public URLs: http://www.plosone.org/
• Additional Information: Funders : National Science Centre, Poland