Author
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Submitted to: Biological Control
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/17/2000 Publication Date: 1/1/2001 Citation: Naranjo, S.E., Hagler, J.R. 2001. Toward the quantification of predation with predator gut immunoassays: a new approach integrating functional response behavior. Biological Control 20: 175-189. Interpretive Summary: Arthropod predators are often credited with being important in suppressing populations of pest insects. However, predation is one of the most difficult processes to study and quantitative field data are lacking in most agricultural systems. The immunological detection of prey remains in a predator's gut has been widely used to identify key predator species and qualitatively evaluate predation on target prey. Despite the quantitative nature of immunoassays the translation to number of prey attacked per predator has been problematic because of the many factors that confound interpretation of the immunoassay response. We developed a new predation model that couples the proportion of predators positive for prey remains, predator density, and predator functional response to prey density for estimating total prey attacked. Using quasi-realistic plant arenas in the greenhouse we developed functional response models for two generalist predators found in cotton (Geocoris punctipes and Orius insidiosus) preyin on pink bollworm eggs. The model was then validated and compared with other immunologically-based predation models using independent greenhouse data. Our predation model was relatively accurate in predicting the total number of prey attacked by both predator species and was a significant improvement over previous models that rely on simple assumptions regarding predator attack rates. The model and approach should serve as a template for quantifying predation in other agricultural systems. Technical Abstract: Immunological methods have been widely used to identify key predator species and qualitatively evaluate predation on target prey. Despite the quantitative nature of immunoassays the translation to number of prey attacked has been problematic because of the many factors that confound interpretation of the immunoassay response. We developed a new predation model that couples the proportion of predators positive for prey remains, predator density, and predator functional response to prey density for estimating total prey attacked. We used single cotton plant arenas in the greenhouse to develop functional response models for two predators (Geocoris punctipes and Orius insidiosus) preying on pink bollworm eggs. The model was validated and compared with other immunologically-based predation models in multiple plant/multiple predator arenas. Our predation model was relatively accurate in predicting the total number of prey attacked by both predator species and was a significant improvement over previous models that rely on simple assumptions regarding predator attack rates. The model also improves the predictive capacity of the functional response model alone by correcting for the number of predators actually consuming prey. Sensitivity analyses indicated that model performance was most sensitive to accurate measurement of input variables such as temperature and the proportion of individuals positive for prey antigens by ELISA and less sensitive to changes in estimates of prey density. |
