On the Dutch Wadden island Schiermonnikoog, the number of ant species increased from 4 in Strandvlakte (pioneer dune) to 11 in Kobbeduinen and 18 in Kooiduinen (advanced stages in primary and secondary succession, respectively). Ant species diversity was positively related to structural diversity of soil and vegetation; a negative relationship was found between ant species diversity and the abundance of the pioneering ant Lasius niger. Microhabitat niche breadth of ant species in the advanced communities Kobbeduinen and Kooiduinen was positively correlated with worker density; this was particularly true in Kobbeduinen, where the highest overall densities of ant workers, root aphids and potential prey (except soil Collembola) were found. In the most diverse but moderately dense Kooiduinen community, only part of the ant species had niche breadths which were in the same degree proportional to worker density as in Kobbeduinen. Mean niche overlap per species was positively related to worker density in Kobbeduinen, but not in Kooiduinen; in Kooiduinen, the degree of realization of the niche breadths found in Kobbeduinen appeared to be a negative power function of the mean niche overlap per species. -from Authors