Influence of field margins and landscape context on ground beetle diversity in Wisconsin (USA) potato fields

The influence of natural areas on ground beetle (Coleoptera: Carabidae) diversity and community composition in Wisconsin potatoes was assessed at local and large spatial scales. To accomplish this, ground beetle communities were sampled in potatoes and grassy field-margin habitats set in landscapes composed of varying amounts of natural area. At a local scale, field-margin habitats supported more, and different, carabid species than potatoes. Large carabids, brachypterous species, species typical of dry habitats and species that feed on seeds were all underrepresented in potatoes compared to field margins. However, the amount of field-margin habitat surrounding potatoes did not affect carabid community structure in the crop. At a larger scale, beetle diversity in potatoes increased and community composition changed with increases in the amount of natural area within 1.5 km of the crop. However, this effect was not evident in adjacent field-margin habitats. These results suggest that the amount of natural area surrounding potatoes affects the composition of potential crop colonizers at a large spatial scale but that disturbances currently limit the types of species that colonize potatoes.