Abstract

I examine feeding rate and reproduction of a generalist arthropod predator Pterostichus cupreus (Coleoptera, Carabidae) at two different densities in two agricultural habitats where this beetle is commonly found; perennial ley and annual barley. I also examine effects of predator densities on arthropod community composition in each crop. The aims are to, in each of these habitats, examine if 1) previously observed food limitation in nature is caused by competition for food where prey is depleted by the competitors, or because predators starve because it is inherently difficult for them to find or consume food in a poor habitat where prey abundance is insensitive to the level of predation, and 2) to examine impact, directly or indirectly, of the predator on arthropod community composition. Predator density was manipulated in plots surrounded by barriers (Treatment) in the two habitats (Crop), and the experiment was repealed early and late in the growing season (Time). Large differences in community composition were found between crops and times. Arthropod abundance was always higher in ley, and increased markedly between the first and second experiment in barley. Predator load was high (44%) in barley in the first experiment compared to the second (26%) and compared to ley (22%). Eggload, amount of stored fat and live body weight of P. cupreus were all markedly higher in ley. The lower fat content in recaptured beetles in barley indicated lower feeding rates and a high degree of food limitation compared to ley. Indications that fat storage was reduced by intraspecific competition were found, but the main difference in fat storage was between crops. No significant treatment effects of initial predator density were detected on arthropod community composition in each crop. Food limitation was mainly caused by difficulty to find food in the barley. Adult feeding and reproduction indicates that barley and ley represent widely different habitat qualities to P. cupreus. The composition and spatial arrangement of perennial and annual crops in the agricultural landscape may be important to long-term predator population dynamics.

Published in

Oikos
1999, Volume: 87, number: 1, pages: 89-96
Publisher: MUNKSGAARD INT PUBL LTD

SLU Authors

• Bommarco, Riccardo

  • Department of Entomology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology
Agricultural Science


Publication identifier

DOI: https://doi.org/10.2307/3546999

Permanent link to this page (URI)

https://res.slu.se/id/publ/40417