Positive predator-predator interactions: enhanced predation rates and synergistic suppression of aphid populations

• Published in: Ecology (Durham) 1998-09, Vol.79 (6), p.2143-2152
• Main Authors: Losey, John E., Denno, Robert F.
• Format: Article
• Language: English
• Subjects: ACYRTHOSIPHON PISUM; agroecosystem; Alfalfa; Animal and plant ecology; Animal ecology; Animal populations; Animal, plant and microbial ecology; Animals; aphid; Aphididae; Autoecology; Biological and medical sciences; BUSQUEDA DE ALIMENTO; carabid; COCCINELLA SEPTEMPUNCTATA; coccinellid; Coccinellidae; DENSIDAD DE LA POBLACION; DENSITE DE POPULATION; DEPREDACION; DEPREDADORES; Ecology; Ecosystems; facilitation; FOLIAR FORAGING PREDATORS; FORAGING; Fundamental and applied biological sciences. Psychology; GROUND FORAGING PREDATORS; HARPALUS; HARPALUS PENNSYLVANICUS; Homoptera; indirect effects; INSECTE NUISIBLE; INSECTOS DANINOS; Insects; Maryland; Pea aphid; Peas; PEST INSECTS; POPULATION DENSITY; Population ecology; Population size; positive interactions; PREDATEUR; PREDATION; Predation (Biology); PREDATOR PREY RELATIONS; PREDATORS; predator–prey interaction; prey density vs. predator interaction; Protozoa. Invertebrata; RECHERCHE DE NOURRITURE; RELACIONES PREDATOR PRESA; RELATION PREDATEUR PROIE; Synecology; synergistic vs. additive
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/0012-9658(1998)079[2143:pppiep]2.0.co;2

Interactions among predators can a have substantial effect on the total impact of the predator complex. We investigated the interaction between foliar-foraging (Coccinella septempunctata) and ground-foraging (Harpalus pennsylvanicus) predators of the pea aphid (Acyrthosiphon pisum) in a series of laboratory and field experiments. The intensity and direction of the interaction were determined by comparing the combined and individual impacts of both predators. In a laboratory mesocosm, the combined predation rate of both predators was nearly double the sum of their individual predation rates. The mechanism for the interaction was the aphid "dropping" behavior elicited by C. septempunctata, which rendered the aphids susceptible to predation by H. pennsylvanicus on the ground. The strength of the synergistic interaction increased with increasing prey density. The interaction between the predators was also demonstrated in both open and closed field cages where the combined impact of the two predators on aphid population growth was significantly greater than the sum of their individual impacts. These results indicate that the importance of ground-foraging predators in agroecosystems may need to be reevaluated and that positive interactions between predators must be considered in models predicting the impact of multiple predator complexes.