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.

Population structure and historical demography of the thorny skate (Amblyraja radiata, Rajidae) in the North Atlantic

“…Similar results were obtained in the European plaice (Pleuronectes platesssa) with the mitochondrial marker (Hoarau et al 2004) and in the cod (Gadus morhua) (Nielsen et al 2001). Other groups of marine organisms that showed strong differentiation between the North Sea and the Baltic Sea include the seagrass Zostera marina (Van Oppen et al 1995;Reusch et al 1999;Olsen et al 2004), the seaweeds Cladophora rupestris (Johansson et al 2003) and Fucus serratus (Coyer et al 2003). Salinity and temperature play a major role in shaping population structure in the herring, Clupea harengus (Jørgensen et al 2005).…”

Scaling of processes shaping the clonal dynamics and genetic mosaic of seagrasses through temporal genetic monitoring

“…The pattern of spatial distribution of genetic and clonal diversities and their respective evolution in time will therefore be highly dependent on the balance between these two strategies. Numerous spatial studies have been carried out for diverse species, reporting highly variable levels of clonal richness that suggest a differential intensity between ISR and RSR strategies (Escaravage et al, 1998;Coyer et al, 2004;Olsen et al, 2004;Pluess and Stocklin, 2004;Diaz-Almela et al, 2007;Alberto et al, 2008). The extreme and most demonstrative cases of ISR dominance are the monoclonal meadows of some seagrass species, including Z. marina (Reusch et al, 1999;Olsen et al, 2004), C. nodosa (Alberto et al, 2008) or P. oceanica (Arnaud-Haond et al, 2007b.…”

“…Numerous spatial studies have been carried out for diverse species, reporting highly variable levels of clonal richness that suggest a differential intensity between ISR and RSR strategies (Escaravage et al, 1998;Coyer et al, 2004;Olsen et al, 2004;Pluess and Stocklin, 2004;Diaz-Almela et al, 2007;Alberto et al, 2008). The extreme and most demonstrative cases of ISR dominance are the monoclonal meadows of some seagrass species, including Z. marina (Reusch et al, 1999;Olsen et al, 2004), C. nodosa (Alberto et al, 2008) or P. oceanica (Arnaud-Haond et al, 2007b. Meadows of the seagrass Z. marina surveyed simultaneously for their demographic evolution and genetic composition in Brittany were shown to be fluctuating mosaics of genetically differentiated patches with variable levels of genotypic and genetic diversity (Becheler et al, 2010).…”

New evidence for habitat-specific selection in Wadden Sea Zostera marina populations revealed by genome scanning using SNP and microsatellite markers

“…In contrast, there are still substantial populations in intertidal areas (Reise et al 2005). Due to its ecological importance, Wadden Sea populations of eelgrass have been the focus of recent genetic research that provided valuable insights on genetic diversity, colonization history and genetic exchange in populations (Reusch 2002;Olsen et al 2004). The increasing genetic information available for Z. marina, including an EST (Expressed Sequence Tag) database available at http://drzompo.uni-muenster.de/ Wissler et al 2009) now allows investigating the genetic basis of physiological adaptation to extreme natural environments such as tidal Xats (Reise 1985).…”