DOI: 10.5061/dryad.9rf5m
title: Data from: Divergent evolutionary processes associated with colonization of offshore islands

description: Oceanic islands have been a test ground for evolutionary theory, but here,
 we focus on the possibilities for evolutionary study created by offshore
 islands. These can be colonized through various means and by a wide range
 of species, including those with low dispersal capabilities. We use
 morphology, modern and ancient sequences of cytochrome b (cytb) and
 microsatellite genotypes to examine colonization history and evolutionary
 change associated with occupation of the Orkney archipelago by the common
 vole (Microtus arvalis), a species found in continental Europe but not in
 Britain. Among possible colonization scenarios, our results are most
 consistent with human introduction at least 5100 bp (confirmed by
 radiocarbon dating). We used approximate Bayesian computation of
 population history to infer the coast of Belgium as the possible source
 and estimated the evolutionary timescale using a Bayesian coalescent
 approach. We showed substantial morphological divergence of the island
 populations, including a size increase presumably driven by selection and
 reduced microsatellite variation likely reflecting founder events and
 genetic drift. More surprisingly, our results suggest that a recent and
 widespread cytb replacement event in the continental source area purged
 cytb variation there, whereas the ancestral diversity is largely retained
 in the colonized islands as a genetic ‘ark’. The replacement event in the
 continental M. arvalis was probably triggered by anthropogenic causes
 (land-use change). Our studies illustrate that small offshore islands can
 act as field laboratories for studying various evolutionary processes over
 relatively short timescales, informing about the mainland source area as
 well as the island.
description: Phylogenetic tree from
 cytb sequences of common voles, Microtus arvalisTreeBase entry
 containing DNA sequence alignment of mitochondrial cytb gene, phylogenetic
 tree from the Bayesian inference analysis, details of the analysis. This
 constitutes Figure 2 in the paper.Microsatellite genotypes
 of common voles, Microtus arvalisGenotypes of 14
 microsatellite loci in 24 populations of common voles in Arlequin format.
 Binned fragment size is given. Samples are labelled with isolate
 number.Microtus_arvalis_Orkney_Msat_24Pops_14Loci.arpInput file for isolation-with-migration analysis of common voles, Microtus arvalisThe file contains mitochondrial cytb sequences and microsatellite genotypes of common voles formatted for the IMa program. Samples are labelled with isolate number.Microtus_arvalis_Orkney_cytb_msat_IMa.txtMorphological measurements of common voles, Microtus arvalisMorphological coordinates collected from 2D images of common vole skulls. Raw cartesian coordinates in pixels are given in columns Rawx1, Rawy1 through to Rawx30, Rawy30. Columns with respective names starting with Ali are Proscrustes coordinates; the shape variables after the Procrustes superimposition. Samples are labelled with the population code and number from the individual voucher.Microtus_arvalis_Morpho_Data.xlsGenBank population set informationAncient DNA sequences of cytb from common voles, Microtus arvalis, are in GenBank under PopSet: 302202495. Modern complete sequences of the cytb gene from common voles, Microtus arvalis, are in GenBank under PopSet: 304634227.GenBank_population_sets.txt