Competition and Intraguild Predation Between Beetles, Pterostichus Stygicus (coleoptera) Carabidae and Centipedes, Scolopocryptops Sexspinosus (scolopemdromorpha: Scolopocryptopidae)

Studying interactions between distantly related species is necessary to understand the complexity of food webs. Generalist predator interactions, such as intraguild predation (IGP) and competition, can alleviate predation pressure and weaken top-down control that predators have on lower trophic levels. Centipedes (Chilopoda) and carabid beetles (Coleoptera) are common deciduous forest floor generalist predators that may interact by competing for resources beneath rocks and logs on the forest floor, especially during dry periods when prey become confined to such microhabitats. We used laboratory and field studies to determine whether the carabid beetle, Pterostichus stygicus (Say), and the centipede, Scolopocryptops sexspinosus (Say) co-occur under artificial cover. Additionally, a laboratory mesocosm experiment was used to examine competitive interactions in intra- and interspecific trials. There was significant negative co-occurrence of beetles and centipedes beneath cover objects in the field and laboratory. Pairings of S. sexspinosus and P. stygicus within mesocosms resulted in high mortality of P. stygicus, and reciprocal but asymmetric IGP. Centipedes maintained weight within solitary, intra- and interspecific mesocosm treatments, however, beetles lost mass in all treatments. Scolopocryptops sexspinosus responded more favorably to intra- and interspecific competition than did P. stygicus. Analysis of the leaf litter mesofauna indicated that these predators consumed similar prey in laboratory mesocosms. Our results suggest that species with very different trophic morphology have the potential to compete for shared microhabitat and prey.