The distribution of ant nests (Hymenoptera, Formicidae) in coastal grey dunes of Flanders (Belgium) and their relationship to myrmecochorous plants

During the summer of 2001, we conducted a study on the spatial distribution of ants in coastal grey dunes (Oostduinkerke, Western Flanders, Belgium). Nest locations of the most abundant ant species were analysed with multivariate techniques. Tetramorium caespitum frequented moss-dominated vegetation, whereas Myrmica sabuleti, M. scabrinodis, Lasius flavus and L. meridionalis preferred grassy vegetations. Formica cunicularia and L. psammophilus occurred in all types of grey dune vegetation. According to recent literature, a positive spatial relationship can exist between the positioning of ant nests and the location of the myrmecochorous plants Viola curtisii, Luzula campestris and Polygala vulgaris in coastal dunes. Neither preliminary investigations, nor our study could confirm this significant positive relationship : the occurrence of myrmecochorous plants seems to be independent of the proximity of nests. It is possible that relationships are masked by a high turnover rate of the nest sites or by a restricted seedling establishment. We did not, however, observe ants transporting seeds of Viola, Luzula or Polygala in the field, possibly indicating the inefficiency of searching for those seeds in areas where population densities of these plants are rather low and other food sources are abundantly available.