Data from: Macrobenthic assemblage structure in a cool-temperate intertidal dwarf-eelgrass bed in comparison to those in lower latitudes.

The evolution and ecology of latitudinal patterns in marine macrofaunal biodiversity and assemblage structure are contentious. With the aim of investigating the occurrence of such patterns in intertidal dwarf-eelgrass beds (Nanozostera spp.), those at cool-temperate Scolt Head Island, UK (latitude 52°N), were examined and compared to equivalent systems in warm-temperate Knysna, South Africa (34°S), and subtropical Moreton Bay, Australia (27°S); systems that had earlier been examined using identical methodology. The Scolt Head bed supported the highest faunal density (mean 6,568 0.1m-2), lowest observed and estimated species richness (32 and 33 spp respectively), lowest species diversity (Simpson’s Index 0.34), highest mean Constancy Index (23.0), lowest proportion of total numbers contributed by singletons or doubletons (0.06%), largest Berger-Parker Dominance (0.81), and least degree of variability between component samples. The beds at Knysna were intermediate between those at Scolt Head and Moreton Bay in all those respects, as well as in nature and composition of the fauna. Similar dwarf-eelgrass beds at Arcachon, France, likewise appear intermediate between those of Scolt Head and Knysna. Community variance in all three regions was greatest at the smallest spatial scale of ≤1 m, at which scale two of the three also displayed randomly organized faunal assemblages, although this changed to non-random at larger spatial scales. Assemblages were deterministically structured at all spatial scales at Knysna. A consistent series of changes in structural characteristics of macrofaunal dwarf-eelgrass assemblages therefore occurred along the latitudinal sequence of Scolt Head (530): Arcachon (450): Knysna (340): Moreton Bay (270). Community assembly patterns did not change with latitude, however, but did so with spatial scale in two of the three regions