Abstract
Increased concentrations of CO2 and ozone are predicted to lower nutritional quality of leaves for insect herbivores, which may increase herbivory as insects eat more to meet their nutritional demands. To test this prediction, we measured levels of herbivory in soybean grown in ambient air and air enriched with CO2 or O3 using free air gas concentration enrichment (FACE). Under open-air conditions and exposure to the full insect community, elevated [CO2] increased the susceptibility of soybeans to herbivory early in the season, whereas exposure to elevated [O3] seemed to have no effect. In the region of the canopy exposed to high levels of herbivory, the percentage of leaf area removed increased from 5 to >11% at elevated [CO2]. We found no evidence for compensatory feeding at elevated [CO2] where leaf nitrogen content and C:N ratio were unaltered in plants experiencing increased herbivory. However, levels of leaf sugars were increased by 31% at elevated [CO2] and coincided with a significant increase in the density of the invasive species Popillia japonica Newman (Japanese beetle). In two-choice feeding trials, Japanese beetles and Mexican bean beetles (Epilachna varivestis Mulsant.) preferred foliage grown at elevated [CO2] to foliage grown at ambient [CO2]. These data support the hypothesis that the increased level of sugar in leaves grown at elevated [CO2] may act as a phagostimulant for the Japanese beetle. If these results apply more widely to soybean production, the expectation of agricultural yield increases as a result of increasing elevated [CO2] may need to be reevaluated.
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Claims 10
Claim · model-written summary
Elevated CO2 increased the susceptibility of soybean to insect herbivory early in the season under open-air conditions.
- Taxon
- soybean
Glycine maxe0 - Treatment
- elevated [CO2]e1
- Interactor
- insect communitye1herbivore
- Outcome
- susceptibility of soybeans to herbivorye1
- Direction
- increasede1
- Comparator
- ambient aire0
- Setting
- open-air conditionse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e1“Under open-air conditions and exposure to the full insect community, elevated [CO2] increased the susceptibility of soybeans to herbivory early in the season”
Claim · model-written summary
Elevated O3 seemed to have no effect on soybean herbivory.
- Taxon
- soybeanGlycine maxe0
- Treatment
- elevated [O3]e2
- Outcome
- herbivorye1
- Direction
- no effecte2
- Comparator
- ambient aire0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e1“Under open-air conditions and exposure to the full insect community, elevated [CO2] increased the susceptibility of soybeans to herbivory early in the season”
e2“exposure to elevated [O3] seemed to have no effect”
Claim · model-written summary
Elevated CO2 increased the percentage of leaf area removed from 5 to over 11% in the canopy region exposed to high herbivory.
- Taxon
- soybeanGlycine maxe0
- Treatment
- elevated [CO2]e3
- Outcome
- percentage of leaf area removede3
- Direction
- increasede3
- Value
- 5 to >11%e3
- Comparator
- ambient aire0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e3“the percentage of leaf area removed increased from 5 to >11% at elevated [CO2]”
Claim · model-written summary
At elevated CO2, leaf nitrogen content and C:N ratio were unaltered in herbivory-exposed soybean plants; no evidence of compensatory feeding was found.
- Taxon
- soybeanGlycine maxe0
- Treatment
- elevated [CO2]e4
- Outcome
- leaf nitrogen content and C:N ratioe4
- Direction
- unalterede4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e4“We found no evidence for compensatory feeding at elevated [CO2] where leaf nitrogen content and C:N ratio were unaltered in plants experiencing increased herbivory”
Claim · model-written summary
Elevated CO2 increased leaf sugar levels by 31% in soybean.
- Taxon
- soybeanGlycine maxe0
- Treatment
- elevated [CO2]e5
- Outcome
- levels of leaf sugarse5
- Direction
- increasede5
- Value
- 31%e5
- Comparator
- ambient aire0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e5“levels of leaf sugars were increased by 31% at elevated [CO2]”
Claim · model-written summary
The density of the invasive Japanese beetle, Popillia japonica, increased significantly with elevated CO2 in soybean.
- Taxon
- soybeanGlycine maxe0
- Interactor
- Popillia japonica
Popillia japonicae6herbivore - Outcome
- density of the invasive species Popillia japonicae6
- Direction
- increasee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e6“coincided with a significant increase in the density of the invasive species Popillia japonica”
Claim · model-written summary
In two-choice feeding trials, Japanese beetles preferred soybean foliage grown at elevated CO2 over foliage grown at ambient CO2.
- Taxon
- soybeanGlycine maxe0
- Treatment
- elevated [CO2]e7
- Interactor
- Japanese beetlesPopillia japonicae7herbivore
- Outcome
- preferred foliagee7
- Direction
- preferrede7
- Comparator
- ambient [CO2]e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e7“In two-choice feeding trials, Japanese beetles and Mexican bean beetles (Epilachna varivestis Mulsant.) preferred foliage grown at elevated [CO2] to foliage grown at ambient [CO2]”
Claim · model-written summary
In two-choice feeding trials, Mexican bean beetles preferred soybean foliage grown at elevated CO2 over foliage grown at ambient CO2.
- Taxon
- soybeanGlycine maxe0
- Treatment
- elevated [CO2]e7
- Interactor
- Mexican bean beetles
Epilachna varivestise7herbivore - Outcome
- preferred foliagee7
- Direction
- preferrede7
- Comparator
- ambient [CO2]e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e7“In two-choice feeding trials, Japanese beetles and Mexican bean beetles (Epilachna varivestis Mulsant.) preferred foliage grown at elevated [CO2] to foliage grown at ambient [CO2]”
Claim · model-written summary
Higher leaf sugar at elevated CO2 may act as a phagostimulant for the Japanese beetle.
- Taxon
- soybeanGlycine maxe0
- Interactor
- Japanese beetlePopillia japonicae7herbivore
- Compound
- sugare7
- Outcome
- phagostimulante7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean grown in ambient air and air enriched with CO2 or O3”
e7“These data support the hypothesis that the increased level of sugar in leaves grown at elevated [CO2] may act as a phagostimulant for the Japanese beetle”
Claim · model-written summary
If the results apply more widely to soybean production, the expectation of agricultural yield increases under elevated CO2 may need to be reevaluated.
- Taxon
- soybeanGlycine maxe6
- Treatment
- increasing elevated [CO2]e6
- Outcome
- agricultural yield increasese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“If these results apply more widely to soybean production, the expectation of agricultural yield increases as a result of increasing elevated [CO2] may need to be reevaluated”
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