Abstract
Plant resistance and predators can influence density-dependent survivorship and growth of herbivores, and their damage to plants. Although the independent effects of plant resistance and predators on herbivores and herbivory are well known, little is known about their interactive and density-dependent effects on herbivores and the amount and distribution of damage on plants. These relationships are important for understanding how herbivore and plant populations influence each other. We used a laboratory density-manipulation experiment to determine how plant resistance (three treatments: jasmonate-insensitive, unmanipulated wild type, and jasmonate-sprayed wild-type plants) and predation (two treatments: predator or no predator) affect the survivorship and growth of an herbivore, as well as per capita damage and the distribution of damage on plants. We found evidence that the density dependence of herbivore survivorship was influenced by predators and an interactive effect of plant resistance and predation. Herbivore growth was reduced by higher plant resistance but was not density-dependent nor affected by predation. Per capita plant damage was reduced by plant resistance, predation, and herbivore density. The within-plant distribution of damage became more even with increasing herbivore density but was not affected by predation or the independent effect of plant resistance. The distribution of damage was also affected by an interaction between plant resistance and herbivore density; damage became less aggregated with density across all plant resistance treatments, but the decrease was strongest for the jasmonate-insensitive plants. These results show that predators influence herbivore density dependence, and that plant resistance can affect the impact of predators on herbivores. Though plant resistance, predation, and herbivore density all reduced per capita herbivore damage to plants, only herbivore density and plant resistance affected the distribution of damage. Distributions of herbivory can influence plant success; documenting patterns of herbivory is an under-appreciated avenue for integrating effects of plant resistance, predators, and herbivore density on plant-herbivore interactions.
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Claims 13
Claim · model-written summary
Higher plant resistance reduced herbivore growth.
- Taxon
- plante1
- Treatment
- higher plant resistancee1
- Interactor
- Herbivoree1herbivore
- Outcome
- Herbivore growthe1
- Direction
- reducede1
Not reportedComparator
Verbatim
e1“Herbivore growth was reduced by higher plant resistance but was not density-dependent nor affected by predation”
Claim · model-written summary
Predation did not change herbivore growth.
- Taxon
- plante1
- Treatment
- predatione1
- Interactor
- Herbivoree1herbivore
- Outcome
- Herbivore growthe1
- Direction
- nor affectede1
Not reportedComparator
Verbatim
e1“Herbivore growth was reduced by higher plant resistance but was not density-dependent nor affected by predation”
Claim · model-written summary
Herbivore growth was not density-dependent.
Verbatim
e1“Herbivore growth was reduced by higher plant resistance but was not density-dependent nor affected by predation”
Claim · model-written summary
Predators influenced the density dependence of herbivore survivorship.
- Taxon
- plante1
- Treatment
- predatorse1
- Interactor
- herbivoree1herbivore
- Second interactor
- predatorse1biocontrol_agent
- Outcome
- density dependence of herbivore survivorshipe1
Not reportedDirection
Verbatim
e1“We found evidence that the density dependence of herbivore survivorship was influenced by predators and an interactive effect of plant resistance and predation”
Claim · model-written summary
Plant resistance and predation interacted in affecting density dependence of herbivore survivorship.
- Taxon
- plante1
- Treatment
- plant resistance and predatione1
- Outcome
- density dependence of herbivore survivorshipe1
Not reportedDirection
Verbatim
e1“We found evidence that the density dependence of herbivore survivorship was influenced by predators and an interactive effect of plant resistance and predation”
Claim · model-written summary
Higher plant resistance reduced per capita plant damage.
- Taxon
- plante1
- Treatment
- plant resistancee1
- Interactor
- herbivoree1herbivore
- Outcome
- Per capita plant damagee1
- Direction
- reducede1
Not reportedComparator
Verbatim
e1“Per capita plant damage was reduced by plant resistance, predation, and herbivore density”
Claim · model-written summary
Predation reduced per capita plant damage.
- Taxon
- plante1
- Treatment
- predatione1
- Interactor
- herbivoree1herbivore
- Outcome
- Per capita plant damagee1
- Direction
- reducede1
Not reportedComparator
Verbatim
e1“Per capita plant damage was reduced by plant resistance, predation, and herbivore density”
Claim · model-written summary
Herbivore density reduced per capita plant damage.
- Taxon
- plante1
- Treatment
- herbivore densitye1
- Interactor
- herbivoree1herbivore
- Outcome
- Per capita plant damagee1
- Direction
- reducede1
Not reportedComparator
Verbatim
e1“Per capita plant damage was reduced by plant resistance, predation, and herbivore density”
Claim · model-written summary
Increasing herbivore density made the within-plant distribution of damage more even.
- Taxon
- plante1
- Treatment
- increasing herbivore densitye1
- Interactor
- herbivoree1herbivore
- Outcome
- distribution of damagee1
- Direction
- more evene1
Not reportedComparator
Verbatim
e1“The within-plant distribution of damage became more even with increasing herbivore density but was not affected by predation or the independent effect of plant resistance”
Claim · model-written summary
Predation did not affect the within-plant distribution of damage.
Not reportedComparator
Verbatim
e1“The within-plant distribution of damage became more even with increasing herbivore density but was not affected by predation or the independent effect of plant resistance”
Claim · model-written summary
Plant resistance did not affect the within-plant distribution of damage independently of herbivore density.
- Taxon
- plante1
- Treatment
- plant resistancee1
- Outcome
- distribution of damagee1
- Direction
- not affectede1
- Qualifier
- independent effecte1
Not reportedComparator
Verbatim
e1“The within-plant distribution of damage became more even with increasing herbivore density but was not affected by predation or the independent effect of plant resistance”
Claim · model-written summary
Damage became less aggregated with herbivore density across all plant resistance treatments.
Verbatim
e1“The distribution of damage was also affected by an interaction between plant resistance and herbivore density; damage became less aggregated with density across all plant resistance treatments, but the decrease was strongest for the jasmonate-insensitive plants”
Claim · model-written summary
The decrease in aggregation of damage with density was strongest for jasmonate-insensitive plants.
Verbatim
e1“The distribution of damage was also affected by an interaction between plant resistance and herbivore density; damage became less aggregated with density across all plant resistance treatments, but the decrease was strongest for the jasmonate-insensitive plants”