Structural and functional connectivity of marine fishes within a semi-enclosed Newfoundland fjord
The interplay between structural connectivity (i.e. habitat continuity) and functional connectivity (i.e. dispersal probability) in marine fishes was examined in a coastal fjord (Holyrood Pond, Newfoundland, Canada) that is completely isolated from the North Atlantic Ocean for most of the year. Genetic differentiation was described in three species (rainbow smelt Osmerus mordax, white hake Urophycis tenuis and Atlantic cod Gadus morhua) with contrasting life histories using seven to 10 microsatellite loci and a protein-coding locus, PanI (G. morhua). Analysis of microsatellite differentiation indicated clear genetic differences between the fjord and coastal regions; however, the magnitude of difference was no more elevated than adjacent bays and was not enhanced by the fjord's isolation. Osmerus mordax was characterized by the highest structure overall with moderate differentiation between the fjord and St Mary's Bay (FSTc.0·047). In contrast, U. tenuis and G. morhua displayed weak differentiation (FST < 0·01). Nonetheless, these populations did demonstrate high rates (< 75%) of Bayesian self-assignment. Furthermore, elevated differentiation was observed at the PanI locus in G. morhua between the fjord and other coastal locations. Interestingly, locus-specific genetic differentiation and expected heterozygosity were negatively associated in O. mordax, in contrast to the positive associations observed in U. tenuis and G. morhua. Gene flow in these species is apparently unencumbered by limited structural connectivity, yet the observed differentiation suggests that population structuring exists over small scales despite high dispersal potential.
Document Type: Regular Paper
Ocean Sciences Centre and Biology Department, Memorial University of Newfoundland, St John's, Newfoundland A1C557, Canada
Marine Gene Probe Laboratory, Biology Department, Life Sciences Centre Dalhousie University, 1355 Oxford Street Halifax, Nova Scotia B3H4J1, Canada
Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St John's, Newfoundland A1C557, Canada
Marine Fish Division, Department of Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, St John's, Newfoundland A1C5X1, Canada
Publication date: October 1, 2009