title: Divergent evolutionary processes associated with colonization of offshore islands.
abstract: 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.
authors.affiliation: Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK; Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Květná 8, Brno, 603 65, Czech Republic.
authors.forename: Natália
authors.initials: N
authors.lastname: Martínková
authors.forename: Ross
authors.initials: R
authors.lastname: Barnett
authors.forename: Thomas
authors.initials: T
authors.lastname: Cucchi
authors.forename: Rahel
authors.initials: R
authors.lastname: Struchen
authors.forename: Marine
authors.initials: M
authors.lastname: Pascal
authors.forename: Michel
authors.initials: M
authors.lastname: Pascal
authors.forename: Martin C
authors.initials: MC
authors.lastname: Fischer
authors.forename: Thomas
authors.initials: T
authors.lastname: Higham
authors.forename: Selina
authors.initials: S
authors.lastname: Brace
authors.forename: Simon Y W
authors.initials: SY
authors.lastname: Ho
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Quéré
authors.forename: Paul
authors.initials: P
authors.lastname: O'Higgins
authors.forename: Laurent
authors.initials: L
authors.lastname: Excoffier
authors.forename: Gerald
authors.initials: G
authors.lastname: Heckel
authors.forename: A Rus
authors.initials: AR
authors.lastname: Hoelzel
authors.forename: Keith M
authors.initials: KM
authors.lastname: Dobney
authors.forename: Jeremy B
authors.initials: JB
authors.lastname: Searle
mesh_terms: D063147:Animal Distribution; D000818:Animals; D003411:Arvicolinae / Q000033:anatomy & histology / Q000235:genetics*; D001499:Bayes Theorem; D001530:Belgium; D005075:Biological Evolution; D045303:Cytochromes b / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D005828:Genetics, Population; D062312:Islands; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010802:Phylogeny; D006113:United Kingdom
chemical_list: D004272:DNA, Mitochondrial; D045303:Cytochromes b
keywords: Microtus arvalis; demographic analysis; genetic replacement; island colonization; phylogeography