Spatial and Temporal Distribution of Ground Beetle (Coleoptera: Carabidae) Assemblages in Riparian Strips and Adjacent Wheat Fields

Abstract

Ground beetles are polyphagous predators that often colonize cereal fields from adjacent habitats. Boundaries separating these habitats may filter the movement of species across them resulting in differences in species composition among the habitats. Ground beetles were captured in spring 1995 at 3 sites, autumn through spring 1995–1996 at 4 sites, and autumn through spring 1996–1997 at 2 sites using pitfall traps positioned in riparian strips, wheat fields, and along riparian-wheat field edges. Canonical correspondence analysis was used to arrange ground beetles along temporal and spatial gradients. Autumn and spring assemblages of ground beetles were separated along the 1st canonical axis. The 2nd canonical axis further separated spring and winter assemblages of ground beetles. With the effects of season removed, ground beetles were classified with respect to habitat association along axes 1 and 2 of a partial canonical correspondence analysis. Based on this analysis, ground beetles occupying wheat field interiors and wheat field edges were separated from those occupying riparian interiors and riparian edges along the 1st canonical axis. The 2nd canonical axis separated beetles occupying interior habitats from those occupying edge habitats. We classified beetles as habitat generalists, wheat specialists, riparian specialists, or boundary specialists. Riparian areas may serve as permanent habitats for ground beetles to colonize cereal fields. Because of their continuous seasonal activity and predatory nature many species of ground beetles are good candidates for biological control of wheat pests.