Edge effects on ant community structure and species richness in an agricultural landscape

The effect of sharp edges between three different types of land use on the species richness and structure of ant communities was examined in an agricultural landscape within Central Hesse, Germany. Species richness and nest densities of ants at the centres and the edges of meadows, crop fields, and fallow land were recorded by hand sampling during 1997 and 1998. Edges between different land-use types did not increase ant species richness at the landscape scale, nor were they unique habitats for a specialised ant fauna. Nonetheless, most species shared ecotonal effects in the way that their relative abundance either decreased (e.g. Myrmica scabrinodis) or increased (e.g. Lasius niger, Lasius flavus) at the edges, resulting in different community structure between edges and centres of the land-use types. This was influenced by two major factors: (i) the boundary contrast between the neighbouring habitats (i.e. in terms of disturbance caused by agricultural practices), and (ii) the response of different species to changing abiotic conditions. High nest densities of aggressive species with large colonies occurred along edges. We hypothesise that this can significantly reduce edge permeability for surface-dwelling arthropods.