Development of an immunological technique for identifying multiple predator–prey interactions in a complex arthropod assemblage

A simplified but highly effective approach for the post-mortem evaluation of predation on several targetedmembers of an arthropod assemblage that does not require the development of pest-specific enzyme-linked immunosorbent assay (ELISA) (e.g. pest-specific monoclonal antibodies) or PCR assays (DNA primers) is described. Laboratory feeding studies were conducted to determine if predation events could be detected from predators that consumed prey marked with foreign protein. I determined that large and small rabbit immunoglobulin G (IgG)-marked prey can be detected by a rabbit-IgG-specific ELISA in the guts of chewing and piercing–sucking type predators. I then conducted multifaceted inclusion and exclusion field cage studies to qualify the degree of interguild and intraguild predation occurring among a complex arthropod assemblage during four separate light phase treatments. The field cages contained an arthropod assemblage consisting of 11 or 12 species of predaceous arthropods and three pest species. The three pests introduced into the cages included third instar Trichoplusia ni marked with rabbit IgG, third instar Lygus hesperus marked with chicken IgG and Pectinophora gossypiella sentinel egg masses. The inclusion cages allowed foraging fire ants, Solenopis xyloni, to freely enter the cages while the exclusion cages contained barriers that prevented ant entry. The results obtained using the conventional inclusion/exclusion field cage methodology revealed that there was substantial interguild and intraguild predation occurring on the majority of the arthropods in the assemblage, particularly in those cages that included ants. I then precisely identified which predators in the assemblage were feeding on the three targeted pests by conducting three post-mortem gut content analyses on each individual predator (1503 individuals) in the assemblage. Specifically, P. gossypiella egg predation events were detected using an established P. gossypiella-egg-specific ELISA, and third instar T. ni and L. hesperus predation events were detected using rabbit-IgGspecific and chicken-IgG-specific ELISAs, respectively. Generally, the gut ELISAs revealed that Collops vittatus, Spanagonicus albofasciatus and Geocoris punctipes readily preyed on P. gossypiella eggs; Nabis alternatus, Zelus renardii and spiders (primarily Misumenops celer) readily preyed on marked L. hesperus nymphs, and spiders, S. albofasciatus and N. alternatus readily preyed on T. ni larvae. Furthermore, the cage methods and the post-mortem predator gut ELISAs revealed very few distinctive patterns of predation with regard to the light cycle the assemblage was exposed to. Annals of Applied Biology ISSN 0003-4746