Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 22, 1996
Publication Date: N/A
Technical Abstract: Borders separating landscape patches filter the movement of organisms across them. Movement across borders is based, in part, on the physical structure of the borders in relation to the physical structure and behavior of organisms. Hard edges restrict organisms from moving across them, while soft edges permit organisms to move freely across them. Species may be classified as hard-edged or soft-edged based on their movement across the borders. Carabids are polyphagous predators of wheat crop pests and frequently disperse into wheat fields from adjacent grasslands. Carabids were captured at four different locations in pitfall traps positioned in grasslands, wheat fields, and along the grassland-wheat field borders. The traps were established in October 1993 and checked weekly through May 1994. Of 51 carabid species collected, the most abundant were Agonum punctiforme, Bembidion castor, B. nigripes, and Pterostichus chalcites. Some species of carabids walked across the borders without restriction, while others were thwarted by the borders. Carabids that walked freely across borders were classified as soft-edge species. Carabids that were restricted by borders were classified as hard-edge species. Carabid activity densities were higher near borders than in the interior of wheat fields, indicating that grasslands may provide a reservoir for habitat generalist species to colonize wheat fields after planting.