Abstract:  One mechanism by which marine organisms may respond to climate shifts is range shifts. The corkwing wrasse (Symphodus melops) is a temperate fish species, inhabiting the coasts of Europe, that show strong indications of current as well as historical (ice-age) range shifts towards the north. Nine neutral microsatellite DNA markers were screened to study genetic signatures and spatial population structure over the entire geographic and thermal gradient of the species from Portugal to Norway. A major genetic break (FST = 0.159 average among pairs) was identified between Scandinavian and more southern populations, with a marked reduction (30% or more) in levels of genetic variability in Scandinavia. The break is probably related to bottleneck(s) associated with post-glacial colonization of the Scandinavian coasts, and indicates a lack of present gene flow across the North Sea. The lack of gene flow can most likely be attributed to the species’ need for rocky substrate for nesting and a relatively short pelagic larval phase, limiting dispersal by ocean currents. These findings demonstrate that long-distance dispersal may be severely limited in the corkwing wrasse, and that successful range-shifts following present climate change may be problematic for this and other species with limited dispersal abilities, even in the seemingly continuous marine environment.

Biography:  Halvor’s primary research interest is on connectivity and microevolutionary patterns and processes. He started working on such issues in 2000. Since then, he has worked on linking genetic data with physical and biological data in different modeling approaches in studies of several high gene flow species. The novel outcome of these papers was a better understanding of underlying mechanisms behind the observed genetic patterns; for instance, determining during which lifestage gene flow more likely occurs. Another outcome was knowledge on the extent these spatial differences are caused by ecological responses (i.e. plasticity) or local adaptations. He has also investigated mechanisms behind genetic patterns by ecological studies of egg density and current measurements in fjords, or behaviour data, all combined with advanced statistics. He has been involved in and also lead (as PI) several research projects that have received funding from several sources in EU, ESF (European Science Foundation), the Norwegian Research Council (NRC), and Nordic funding sources (Nordic Council).