Prey nutrient content creates omnivores out of predators

The proximate forces that create omnivores out of herbivores and predators have long fascinated ecologists, but the causal reasons for a shift to omnivory are poorly understood. Determining what factors influence changes in trophic position are essential as omnivory plays a central role in theoretic...

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Bibliographic Details
Published in:Ecology letters 2019-02, Vol.22 (2), p.275-283
Main Authors: Ugine, Todd A., Krasnoff, Stuart B., Grebenok, Robert J., Behmer, Spencer T., Losey, John E., Irwin, Rebecca
Format: Article
Language:English
Subjects:
Animals
Appetite
Beetles
Cholesterol
Coleoptera
Diet
Dietary supplements
Ecological effects
evolution
facultative predator
Fitness
Foliage
Food Chain
Herbivores
Herbivory
lipid
macronutrient
nutrient
Nutrient balance
Nutrient content
Nutrients
Nutrition
Omnivores
omnivory
Phytosterols
Predators
Predatory Behavior
Prey
sterol
Sterols
zoophytophagy
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Summary:The proximate forces that create omnivores out of herbivores and predators have long fascinated ecologists, but the causal reasons for a shift to omnivory are poorly understood. Determining what factors influence changes in trophic position are essential as omnivory plays a central role in theoretical and applied ecology. We used sevenspotted lady beetles (Coccinella septempunctata) to test how prey nutrient content affects beetles’ propensity to engage in herbivory. We show that beetles consuming an all‐prey diet demonstrate normal growth and development, but suffer a complete loss of fitness (spermatogenic failure) that is restored via herbivory and supplementation with phytosterols and cholesterol. Furthermore, we show that lady beetles possess a state‐dependent sterol‐specific appetite and redressed their sterol deficit by feeding on foliage. These results demonstrate that predators balance their nutrient intake via herbivory when prey quality is low, and reveal a selective force (sterol nutrition) that drives predatory taxa to omnivory.
ISSN:1461-023X
1461-0248
DOI:10.1111/ele.13186