Percorrer por autor "Bruhn, Annette"
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- Genetic diversity of Saccharina latissima (Phaeophyceae) along a salinity gradient in the North Sea-Baltic Sea transition zonePublication . Nielsen, Mette Moller; Paulino, Cristina; Neiva, J.; Krause-Jensen, Dorte; Bruhn, Annette; Serrão, EsterThe North Sea-Baltic Sea transition zone constitutes a boundary area for the kelp species Saccharina latissima due to a strong salinity gradient operating in the area. Furthermore, the existence of S.latissima there, along Danish waters, is fairly patchy as hard bottom is scarce. In this study, patterns of genetic diversity of S.latissima populations were evaluated along the salinity gradient area of Danish waters (here designated brackish) and were compared to reference sites (here designated marine) outside the gradient area, using microsatellite markers. The results showed that the S.latissima populations were structured into two clusters corresponding to brackish versus marine sites, and that gene flow was reduced both between clusters and between populations within clusters. In addition, results provided empirical evidence that marginal populations of S.latissima in the salinity gradient area exhibited a distinct genetic structure when compared to marine ones. Brackish populations were less diverse, more related, and showed increased differentiation over distance compared to marine populations. The isolation of the brackish S.latissima populations within the salinity gradient area of Danish waters in conjunction with their general low genetic diversity makes these populations vulnerable to ongoing environmental and climate change, predicted to result in declining salinity in the Baltic Sea area that may alter the future distribution and performance of S.latissima in the area.
- Glacial vicariance drives phylogeographic diversification in the amphi-boreal kelp Saccharina latissimaPublication . MACHADO, JOÃO NEIVA; Paulino, Cristina; Nielsen, Mette M.; Krause-Jensen, Dorte; Saunders, Gary W.; Assis, Jorge; Barbara, Ignacio; Tamigneaux, Eric; Gouveia, Licínia; Aires, Tânia; Marba, Nuria; Bruhn, Annette; Pearson, Gareth; Serrao, Ester A.Glacial vicariance is regarded as one of the most prevalent drivers of phylogeographic structure and speciation among high-latitude organisms, but direct links between ice advances and range fragmentation have been more difficult to establish in marine than in terrestrial systems. Here we investigate the evolution of largely disjunct (and potentially reproductively isolated) phylogeographic lineages within the amphi-boreal kelp Saccharina latissima s.l. Using molecular data (COI, microsatellites) we confirm that S. latissima comprises also the NE Pacific S. cichorioides complex and is composed of divergent lineages with limited range overlap and genetic admixture. Only a few genetic hybrids were detected throughout a Canadian Arctic/NW Greenland contact zone. The degree of genetic differentiation and sympatric isolation of phylogroups suggest that S. latissima s.l. represents a complex of incipient species. Phylogroup distributions compared with paleo-environmental reconstructions of the cryosphere further suggest that diversification within S. latissima results from chronic glacial isolation in disjunct persistence areas intercalated with ephemeral interglacial poleward expansions and admixture at high-latitude (Arctic) contact zones. This study thus supports a role for glaciations not just in redistributing pre-existing marine lineages but also as a speciation pump across multi-glacial cycles for marine organisms otherwise exhibiting cosmopolite amphi-boreal distributions.