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Submitted to: Ecological Applications
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/25/2011 Publication Date: N/A Citation: N/A Interpretive Summary: A simple, versatile, and effective method for quantifying predation by gut analysis is described. Predator gut content assays were conducted on chewing and piercing—sucking type predators that consumed a 3rd instar plant bugs (Lygus hesperus) marked with rabbit IgG. The rabbit IgG gut content assay detected the marked prey in the vast majority of both types of predators for up to a day after feeding. Then, field cage studies were conducted to quantify predation rates of the natural cotton predator assemblage on protein marked plant bugs. Bugs were marked with rabbit IgG, chicken IgG, and soy milk and one of each type was released into 360 field cages containing a cotton plant and the natural population of predators. After 7 h, each caged plant was pulled from the field, the predaceous arthropods in each cage were tallied, and each predator was assayed for the presence of marked prey items by a suite of protein-specific assays. A procedural error with the soy mark application negated the anti-soy assay data, but the rabbit and chicken assays showed which predators preyed on the protein-marked lygus. The protein-specific assays revealed that various spiders, true bugs and beetles were the most common predators of lygus. In all, 73 predation events were recorded in the guts of the 556 predators encountered in the field cages. Of these 25, 23, and 14 marked individuals were eaten by various spiders, true bugs and beetles, respectively. This study verifies that prey marking is a powerful method for quantifying predation rates on lygus. Technical Abstract: A simple, versatile, and effective method for post-mortem quantification of predation on prey items marked with protein antigens is described. First, short-term protein marking retention tests were conducted on the targeted prey, immature Lygus hesperus Knight (Heteroptera: Miridae). Chicken IgG, rabbit IgG, or soy milk proteins were readily detectable by a suite of protein specific enzyme-linked immunosorbent assays (ELISA) on the L. hesperus. Then, predator gut content assays were conducted on chewing and piercing—sucking type predators that consumed a 3rd instar L. hesperus marked with rabbit IgG. The rabbit IgG gut content ELISA detected the marked prey in the vast majority of both types of predators for up to 24 hours after feeding. Finally, field cage studies were conducted to quantify predation rates of the natural cotton predator assemblage on protein marked L. hesperus nymphs. Each 4th instar L. hesperus marked with rabbit IgG, chicken IgG, and soy milk was released into one of 360 field cages containing a cotton plant and the natural population of predators. After 7 h, each caged plant was pulled from the field, the predaceous arthropods in each cage were tallied, and each individual predator was assayed for the presence of marked prey by a suite of protein-specific ELISAs. A procedural error with the soy mark application negated the anti-soy ELISA data, but the anti-rabbit IgG and anti-chicken IgG ELISAs showed which predators preyed on the IgG marked nymphs. The protein-specific gut ELISAs revealed that various members of Araneae, Heteroptera, and Coleoptera were the most common predators of the marked prey items. In all, 73 predation events were recorded in the guts of the 556 predators encountered in the field cages. Of these 25, 23, and 14 marked individuals were eaten by various members of Araneae, Heteroptera, and Coleoptera, respectively. This study verifies that prey immunomarking is a powerful method for quantifying predation rates on L. hesperus. |
