North Atlantic phylogeography and large-scale population differentiation of the seagrass Zostera marina L.
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.
Olsen
Jeanine L
JL
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
Stam
Wytze T
WT
Coyer
James A
JA
Reusch
Thorsten B H
TB
Billingham
Martin
M
Boström
Christoffer
C
Calvert
Elizabeth
E
Christie
Hartvig
H
Granger
Stephen
S
la Lumière
Richard
R
Milchakova
Nataliya
N
Oudot-Le Secq
Marie-Pierre
MP
Procaccini
Gabriele
G
Sanjabi
Bahram
B
Serrao
Ester
E
Veldsink
Jan
J
Widdicombe
Stephen
S
Wyllie-Echeverria
Sandy
S
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
D017931:DNA Primers; D018742:DNA, Chloroplast; D021903:DNA, Ribosomal Spacer