Increased nitrogen availability influences predator–prey interactions by altering host-plant quality |
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Authors: | John J Couture Jason S Servi Richard L Lindroth |
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Institution: | (1) Department of Entomology, University of Wisconsin, Madison, WI 53706, USA |
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Abstract: | Little is known about how plant nutritional and defensive qualities interact to influence predator–prey interactions. To address
this need, we provided the neo-tropical milkweed, Asclepias curassavica, with two levels of nitrogen availability and examined how altered host-plant quality influenced the responses of a specialist
aphid, Aphis nerii, and a coccinellid predator, Harmonia axyridis. Aphis nerii uses A. curassavica for multiple resources, including nutrition and sequestration of cardenolides for defense against natural enemies. Increased
nitrogen availability improved A. curassavica quality by decreasing carbon-to-nitrogen (C:N) ratios and cardenolide concentrations, resulting in A. nerii that also had lower C:N ratios and cardenolide concentrations. Aphis nerii population growth was higher on plants with high nitrogen availability, compared with aphids on plants with low nitrogen
availability. In no-choice feeding trials, Harmonia axyridis consumed more high C:N ratio aphids, suggesting a potential compensatory response to reduced aphid nutritional quality. Additionally,
H. axyridis were able to consume more low-quality aphids at the expense of increasing exposure to increased cardenolide concentrations,
suggesting that interactions between H. axyridis and A. nerii may be strongly influenced by prey nutritional quality. This work highlights the need to consider how variation in plant
quality influences herbivore nutritional and defensive quality when examining mechanisms that influence predator–prey interactions. |
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