Understanding marine reserve function in a seascape genetics context: Nucella lapillus in Strangford Lough (Northern Ireland) as an example

Abstract

A conservation priority in the marine environment is the establishment of ecologically coherent reserve networks. Since these networks will integrate existent reserves, an understanding of spatial genetic diversity and genetic connectivities between areas is necessary. Using Strangford Lough marine nature reserve (MNR) as a model, spatial genetic analyses were employed to evaluate the function of the lough. Samples of the marine gastropod Nucella lapillus (L.) from 7 locations in the reserve and adjacent areas were screened at 6 microsatellites. Genetic variation was temporally stable. Significant genetic structuring (FST = 0.133) was observed among samples. Genetic diver- gence and isolation by distance indicated reduced gene flow between the marine reserve and coastal samples relative to that between adjacent coastal samples. Partitioning of genetic variation between the reserve and coast was significant (AMOVA, 7.45%, p < 0.005). Samples within the reserve were not homogeneous, and genetic diversity decreased away from the mouth of the lough. Relative genetic isolation and reduced genetic diversity in the reserve may be caused by hydrographic barri- ers. A cline in genetic structure was observed in the Irish Sea. This is consistent with patterning of gene flow by predominant currents, habitat availability and seasonal oceanographic features. It appears that mesoscale topographic and hydrographic features drive patterns of genetic diversity, and these factors are likely to be important for understanding MNR function. For direct developers lacking a planktonic phase, such as N. lapillus, considerations of the ecological coherence of a net- work are likely to be highly dependent on the habitat lying outside reserves.