Estimating macrozoobenthic species richness along an environmental gradient: Sample size matters

► We studied patterns of species numbers per sample in tidal-flat bivalves. ► Sampling sites were arranged in an order of increasing distance from the coast. ► These gradients included intertidal height and sediment character. ► The location along the gradient of hotspots of species density depended on sample size. ► We explain the findings by the differential distribution patterns of abundant and rare species.