Abstract
Abstract Animal mutualisms, which involve beneficial interactions between individuals of different species, are common in nature. Insect–insect mutualism, for example, is widely regarded as a keystone ecological interaction. Some mutualisms are anticipated to be modified by climate change, but the focus has largely been on plant–microbe and plant–animal mutualisms rather than those between animals. Ant–aphid mutualisms, whereby ants tend aphids to harvest their honeydew excretions and, in return, provide protection for the aphids, are widespread. The mutualism is heavily influenced by the quality and quantity of honeydew produced by aphids, which is directly affected by host plant quality. As predicted increases in concentrations of atmospheric carbon dioxide ( eCO 2 ) are widely reported to affect plant nutritional chemistry, this may also alter honeydew quality and hence the nature of ant–aphid mutualisms. Using glasshouse chambers and field‐based open‐top chambers, we determined the effect of eCO 2 on the growth and nutritional quality (foliar amino acids) of lucerne ( Medicago sativa ). We determined how cowpea aphid ( Aphis craccivora ) populations and honeydew production were impacted when feeding on such plants and how this affected the tending behaviour of ants ( Iridomyrmex sp.). eCO 2 stimulated plant growth but decreased concentrations of foliar amino acids by 29% and 14% on aphid‐infested plants and aphid‐free plants, respectively. Despite the deterioration in host plant quality under eCO 2 , aphids maintained performance and populations were unchanged by eCO 2 . Aphids induced higher concentrations of amino acids (glutamine, asparagine, glutamic acid and aspartic acid) important for endosymbiont‐mediated synthesis of essential amino acids. Aphids feeding under eCO 2 also produced over three times more honeydew than aphids feeding under ambient CO 2 , suggesting they were imbibing more phloem sap at eCO 2 . The frequency of ant tending of aphids more than doubled in response to eCO 2 . To our knowledge, this is the first study to demonstrate the effects of atmospheric change on an ant–aphid mutualism. In particular, these results highlight how impending changes to concentrations of atmospheric CO 2 may alter mutualistic behaviour between animals. These could include positive impacts, as reported here, shifts from mutualism to antagonism, partner switches and mutualism abandonment.
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Claims 7
Claim · model-written summary
Elevated CO2 stimulated lucerne growth.
- Taxon
- lucerne
Medicago sativae1 - Treatment
- eCO 2e0
- Outcome
- plant growthe0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“eCO 2 stimulated plant growth”
e1“lucerne ( Medicago sativa )”
Claim · model-written summary
Elevated CO2 lowered foliar amino acids by 29% in aphid-infested lucerne.
- Taxon
- lucerneMedicago sativae2
- Treatment
- eCO 2e1
- Interactor
- aphide0pest
- Outcome
- concentrations of foliar amino acidse0
- Direction
- decreasede0
- Value
- 29%e0
- Qualifier
- aphid‐infested plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased concentrations of foliar amino acids by 29% and 14% on aphid‐infested plants and aphid‐free plants, respectively”
e1“eCO 2 stimulated plant growth”
e2“lucerne ( Medicago sativa )”
Claim · model-written summary
Elevated CO2 lowered foliar amino acids by 14% in aphid-free lucerne.
- Taxon
- lucerneMedicago sativae2
- Treatment
- eCO 2e1
- Outcome
- concentrations of foliar amino acidse0
- Direction
- decreasede0
- Value
- 14%e0
- Qualifier
- aphid‐free plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased concentrations of foliar amino acids by 29% and 14% on aphid‐infested plants and aphid‐free plants, respectively”
e1“eCO 2 stimulated plant growth”
e2“lucerne ( Medicago sativa )”
Claim · model-written summary
Cowpea aphid populations were unchanged under elevated CO2.
- Taxon
- lucerneMedicago sativae2
- Treatment
- eCO 2e0
- Interactor
- cowpea aphid
Aphis craccivorae1pest - Outcome
- populationse0
- Direction
- unchangede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“aphids maintained performance and populations were unchanged by eCO 2”
e1“cowpea aphid ( Aphis craccivora )”
e2“lucerne ( Medicago sativa )”
Claim · model-written summary
Aphid infestation induced higher levels of four amino acids in lucerne.
- Taxon
- lucerneMedicago sativae1
- Treatment
- Aphidse0
- Interactor
- AphidsAphidomorphae0pest
- Outcome
- concentrations of amino acids (glutamine, asparagine, glutamic acid and aspartic acid)e0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aphids induced higher concentrations of amino acids (glutamine, asparagine, glutamic acid and aspartic acid)”
e1“lucerne ( Medicago sativa )”
Claim · model-written summary
Aphids feeding under elevated CO2 produced over three times more honeydew than at ambient CO2.
- Taxon
- lucerneMedicago sativae1
- Treatment
- eCO 2e0
- Interactor
- AphidsAphidomorphae0pest
- Outcome
- Aphids feeding under eCO 2 also produced over three times more honeydewe0
- Direction
- moree0
- Value
- over three timese0
- Comparator
- ambient CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aphids feeding under eCO 2 also produced over three times more honeydew than aphids feeding under ambient CO 2”
e1“lucerne ( Medicago sativa )”
Claim · model-written summary
Ant tending of aphids more than doubled under elevated CO2.
- Taxon
- lucerneMedicago sativae1
- Treatment
- eCO 2e0
- Interactor
- aphidsAphidomorphae0pest
- Second interactor
- antsFormicidaee2other
- Outcome
- frequency of ant tending of aphidse0
- Direction
- doublede0
- Value
- more than doublede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The frequency of ant tending of aphids more than doubled in response to eCO 2”
e1“lucerne ( Medicago sativa )”
e2“ants ( Iridomyrmex sp.)”
The same questions in other papers
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- positive
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14 papers in the same direction as this paper · 5 in the opposite direction
- negative
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See all 20 papers →co2 · Aphis craccivora · Medicago sativa (alfalfa)Results agree
1 paper in the same direction as this paper
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.