title: Genetic structure in the European endemic seabird, Phalacrocorax aristotelis, shaped by a complex interaction of historical and contemporary, physical and nonphysical drivers.
abstract: Geographically separated populations tend to be less connected by gene flow, as a result of physical or nonphysical barriers preventing dispersal, and this can lead to genetic structure. In this context, highly mobile organisms such as seabirds are interesting because the small effect of physical barriers means nonphysical ones may be relatively more important. Here, we use microsatellite and mitochondrial data to explore the genetic structure and phylogeography of Atlantic and Mediterranean populations of a European endemic seabird, the European shag, Phalacrocorax aristotelis, and identify the primary drivers of their diversification. Analyses of mitochondrial markers revealed three phylogenetic lineages grouping the North Atlantic, Spanish/Corsican and eastern Mediterranean populations, apparently arising from fragmentation during the Pleistocene followed by range expansion. These traces of historical fragmentation were also evident in the genetic structure estimated by microsatellite markers, despite significant contemporary gene flow among adjacent populations. Stronger genetic structure, probably promoted by landscape, philopatry and local adaptation, was found among distant populations and those separated by physical and ecological barriers. This study highlights the enduring effect of Pleistocene climatic changes on shag populations, especially within the Mediterranean Basin, and suggests a role for cryptic northern refugia, as well as known southern refugia, on the genetic structure of European seabirds. Finally, it outlines how contemporary ecological barriers and behavioural traits may maintain population divergence, despite long-distance dispersal triggered by extreme environmental conditions (e.g. population crashes).
authors.affiliation: Section of Animal Biology, Department of Biology, University of Patras, Patras, GR-26504, Greece.|Centre for Ecology & Hydrology, Penicuik, EH26 0QB, UK.
authors.forename: Evanthia
authors.initials: E
authors.lastname: Thanou
authors.affiliation: Department of Mathematics and Geosciences, University of Trieste, I-34127, Trieste, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Sponza
authors.affiliation: Centre for Ecology & Hydrology, Penicuik, EH26 0QB, UK.|Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Nelson
authors.affiliation: Centre for Ecology & Hydrology, Penicuik, EH26 0QB, UK.
authors.forename: Annika
authors.initials: A
authors.lastname: Perry
authors.affiliation: Centre for Ecology & Hydrology, Penicuik, EH26 0QB, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Wanless
authors.affiliation: Centre for Ecology & Hydrology, Penicuik, EH26 0QB, UK.
authors.forename: Francis
authors.initials: F
authors.lastname: Daunt
authors.affiliation: Centre for Ecology & Hydrology, Penicuik, EH26 0QB, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Cavers
mesh_terms: D000818:Animals; D001717:Birds / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D051456:Gene Flow; D014644:Genetic Variation; D005828:Genetics, Population; D018895:Microsatellite Repeats; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: European seabird; Pleistocene refugia; demography; genetic structure; molecular clock; phylogeography