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Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/9/2006 Publication Date: 9/1/2006 Citation: Hagler, J.R. 2006. An immunological technique for identifying multiple predator—prey interactions in a complex arthropod assemblage. Annals of Applied Biology 00: 1-13. Interpretive Summary: A new method to study arthropod predation was developed. Specifically, potential prey items can be marked with foreign proteins. In turn, predators that consume protein marked prey can be assayed by an immunological assay designed to detect the foreign protein in predator guts. In laboratory feeding trials I determined that prey marked with rabbit IgG protein can be detected by a rabbit IgG-specific enzyme-linked immunosorbent assay (ELISA). I then conducted multi-faceted inclusion and exclusion field cage studies to qualify the degree of interguild and intraguild predation occurring amongst a complex arthropod assemblage. The field cages contained an arthropod assemblage consisting of 11 or 12 species of predators and three pest species. The three pests introduced into the cages included cabbage looper marked with rabbit IgG, lygus marked with chicken IgG, and pink bollworm eggs. I 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 in the assemblage. Specifically, pink bollworm egg predation events were detected using an established pink bollworm egg specific ELISA and cabbage looper and lygus bug predation events were detected using rabbit IgG and chicken IgG specific ELISAs, respectively. The gut assay results precisely identified which predators were consuming the targeted pests. My results demonstrate a simplified but highly effective approach for the post-mortem evaluation of predation on several targeted members of an arthropod assemblage that does not require the development of pest-specific ELISA (e.g. pest-specific monoclonal antibodies) or PCR assays (DNA primers). Technical Abstract: A laboratory feeding study was conducted to determine if predation events could be detected from predators that consumed prey marked with foreign protein. In laboratory feeding trials I determined that large and small rabbit immunoglobulin G (IgG) marked prey can be detected by a rabbit IgG-specific enzyme-linked immunosorbent assay (ELISA) in the guts of chewing and piercing—sucking type predators. I then conducted multi-faceted inclusion and exclusion field cage studies to qualify the degree of interguild and intraguild predation occurring amongst 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 inclusion cage tests allowed foraging fire ants, Solenopis xylonii McCook to freely enter the cages while the exclusion cage tests contained barriers that prevented ant entry. The three pests introduced into the cages included third instar Trichoplusia ni (Hübner) marked with rabbit IgG, third instar Lygus hesperus Knight marked with chicken IgG, and Pectinophora gossypiella sentinel egg masses. 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 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 IgG and chicken IgG specific ELISAs, respectively. Generally, the gut ELISAs revealed that C. vittatus, S. albofasciatus, and G. punctipes readily preyed on P. gossypiella eggs; N. alternatus, Z. 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. My results demonstrate a simplified but highly effective approach for the post-mortem evaluation of predation on several targeted members of an arthropod assemblage that does not require the development of pest-specific ELISA (e.g. pest-specific monoclonal antibodies) or PCR assays (DNA primers). |
