title: North Atlantic phylogeography and large-scale population differentiation of the seagrass Zostera marina L.
abstract: As the most widespread seagrass in temperate waters of the Northern Hemisphere, Zostera marina provides a unique opportunity to investigate the extent to which the historical legacy of the last glacial maximum (LGM18 000-10 000 years bp) is detectable in modern population genetic structure. We used sequences from the nuclear rDNA-internal transcribed spacer (ITS) and chloroplast matK-intron, and nine microsatellite loci to survey 49 populations (> 2000 individuals) from throughout the species' range. Minimal sequence variation between Pacific and Atlantic populations combined with biogeographical groupings derived from the microsatellite data, suggest that the trans-Arctic connection is currently open. The east Pacific and west Atlantic are more connected than either is to the east Atlantic. Allelic richness was almost two-fold higher in the Pacific. Populations from putative Atlantic refugia now represent the southern edges of the distribution and are not genetically diverse. Unexpectedly, the highest allelic diversity was observed in the North Sea-Wadden Sea-southwest Baltic region. Except for the Mediterranean and Black Seas, significant isolation-by-distance was found from ~150 to 5000 km. A transition from weak to strong isolation-by-distance occurred at ~150 km among northern European populations suggesting this scale as the natural limit for dispersal within the metapopulation. Links between historical and contemporary processes are discussed in terms of the projected effects of climate change on coastal marine plants. The identification of a high genetic diversity hotspot in Northern Europe provides a basis for restoration decisions.
authors.affiliation: Department of Marine Biology, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands. j.l.olsen@biol.rug.nl
authors.forename: Jeanine L
authors.initials: JL
authors.lastname: Olsen
authors.forename: Wytze T
authors.initials: WT
authors.lastname: Stam
authors.forename: James A
authors.initials: JA
authors.lastname: Coyer
authors.forename: Thorsten B H
authors.initials: TB
authors.lastname: Reusch
authors.forename: Martin
authors.initials: M
authors.lastname: Billingham
authors.forename: Christoffer
authors.initials: C
authors.lastname: Boström
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Calvert
authors.forename: Hartvig
authors.initials: H
authors.lastname: Christie
authors.forename: Stephen
authors.initials: S
authors.lastname: Granger
authors.forename: Richard
authors.initials: R
authors.lastname: la Lumière
authors.forename: Nataliya
authors.initials: N
authors.lastname: Milchakova
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Oudot-Le Secq
authors.forename: Gabriele
authors.initials: G
authors.lastname: Procaccini
authors.forename: Bahram
authors.initials: B
authors.lastname: Sanjabi
authors.forename: Ester
authors.initials: E
authors.lastname: Serrao
authors.forename: Jan
authors.initials: J
authors.lastname: Veldsink
authors.forename: Stephen
authors.initials: S
authors.lastname: Widdicombe
authors.forename: Sandy
authors.initials: S
authors.lastname: Wyllie-Echeverria
mesh_terms: D001483:Base Sequence; D016000:Cluster Analysis; D017931:DNA Primers; D018742:DNA, Chloroplast / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003710:Demography; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D019684:Magnoliopsida / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics; D008969:Molecular Sequence Data; D009792:Oceans and Seas; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D018742:DNA, Chloroplast; D021903:DNA, Ribosomal Spacer