Site-specific distribution of the bivalve <i>Scrobicularia plana</i> along the European coast

The development and maintenance of spatial patterns and the way they affect the dynamics of populations and ecosystems is a key issue in ecology. Since each individual and each species experiences the environment on a unique range of scales, it is vital to determine the spatial scales across which organisms interact with each other and the structuring influence of their environments, which can be achieved by analyzing species’ distribution patterns. Here, the spatial variation in the distribution of <i>Scrobicularia plana</i> is described for 4 intertidal areas along the species’ distributional range. Spatial autocorrelation correlograms based on Moran’s coefficient reveal that while the Trondheim (Norway) population was randomly distributed, at Minho (Portugal), the Westerschelde, and the Wadden Sea (both in The Netherlands) populations were aggregated. Patch diameter varied from 150 to 1250 m, in Minho and Westerschelde, respectively; while in the Wadden Sea, patches of 4 to 10 km were detected. Comparisons of spatial patterns with those of other co-occurring bivalve species (<i>Abra tenuis</i>, <i>Cerastoderma edule</i>, and <i>Macoma balthica</i>) revealed that <i>S. plana</i>’s distribution was generally patchier. The distribution of <i>S. plana</i> was correlated with sediment type at Westerschelde and Trondheim, but not Minho. The observed differences in distribution patterns and their correlation with environmental factors reveal that spatial patterns of <i>S. plana</i> are site-specific rather than species-specific