Limits...
Water stress strengthens mutualism among ants, trees, and scale insects.

Pringle EG, Akçay E, Raab TK, Dirzo R, Gordon DM - PLoS Biol. (2013)

Bottom Line: Abiotic environmental variables strongly affect the outcomes of species interactions.A model of the carbon trade-offs for the mutualistic partners shows that the observed strategies can arise from the carbon costs of rare but extreme events of herbivory in the rainy season.Thus, water limitation, together with the risk of herbivory, increases the strength of a carbon-based mutualism.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Stanford University, Stanford, California, United States of America ; Michigan Society of Fellows, University of Michigan, Ann Arbor, Michigan, United States of America ; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, United States of America ; School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan, United States of America.

ABSTRACT
Abiotic environmental variables strongly affect the outcomes of species interactions. For example, mutualistic interactions between species are often stronger when resources are limited. The effect might be indirect: water stress on plants can lead to carbon stress, which could alter carbon-mediated plant mutualisms. In mutualistic ant-plant symbioses, plants host ant colonies that defend them against herbivores. Here we show that the partners' investments in a widespread ant-plant symbiosis increase with water stress across 26 sites along a Mesoamerican precipitation gradient. At lower precipitation levels, Cordia alliodora trees invest more carbon in Azteca ants via phloem-feeding scale insects that provide the ants with sugars, and the ants provide better defense of the carbon-producing leaves. Under water stress, the trees have smaller carbon pools. A model of the carbon trade-offs for the mutualistic partners shows that the observed strategies can arise from the carbon costs of rare but extreme events of herbivory in the rainy season. Thus, water limitation, together with the risk of herbivory, increases the strength of a carbon-based mutualism.

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Related in: MedlinePlus

Tree NSC pools and water stress.Total NSCs, starch and sucrose pools in main stems in (A) the late dry season (April 2009) at a wetter site (Santa Rosa; black bars) and a drier site (Chamela; white bars) and (B) the early dry season (October 2009; gray bars) and the late dry season (April 2009; white bars) at the drier site. Bars indicate means, and error bars indicate SE; values are based on plant dry weights. Starch bars are open, glucose (free sugars) bars have diagonal lines, and sucrose bars have vertical lines. Asterisks (*) indicate p<0.05 by two-tailed t tests.
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pbio-1001705-g004: Tree NSC pools and water stress.Total NSCs, starch and sucrose pools in main stems in (A) the late dry season (April 2009) at a wetter site (Santa Rosa; black bars) and a drier site (Chamela; white bars) and (B) the early dry season (October 2009; gray bars) and the late dry season (April 2009; white bars) at the drier site. Bars indicate means, and error bars indicate SE; values are based on plant dry weights. Starch bars are open, glucose (free sugars) bars have diagonal lines, and sucrose bars have vertical lines. Asterisks (*) indicate p<0.05 by two-tailed t tests.

Mentions: (A) Map showing the 26 study sites and (B) their annual precipitation. Additional work was conducted at three of the sites, Chamela (white circle), Huatulco (gray diamond), and Santa Rosa (black triangle), that spanned the Mesoamerican dry-forest precipitation gradient.


Water stress strengthens mutualism among ants, trees, and scale insects.

Pringle EG, Akçay E, Raab TK, Dirzo R, Gordon DM - PLoS Biol. (2013)

Tree NSC pools and water stress.Total NSCs, starch and sucrose pools in main stems in (A) the late dry season (April 2009) at a wetter site (Santa Rosa; black bars) and a drier site (Chamela; white bars) and (B) the early dry season (October 2009; gray bars) and the late dry season (April 2009; white bars) at the drier site. Bars indicate means, and error bars indicate SE; values are based on plant dry weights. Starch bars are open, glucose (free sugars) bars have diagonal lines, and sucrose bars have vertical lines. Asterisks (*) indicate p<0.05 by two-tailed t tests.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3818173&req=5

pbio-1001705-g004: Tree NSC pools and water stress.Total NSCs, starch and sucrose pools in main stems in (A) the late dry season (April 2009) at a wetter site (Santa Rosa; black bars) and a drier site (Chamela; white bars) and (B) the early dry season (October 2009; gray bars) and the late dry season (April 2009; white bars) at the drier site. Bars indicate means, and error bars indicate SE; values are based on plant dry weights. Starch bars are open, glucose (free sugars) bars have diagonal lines, and sucrose bars have vertical lines. Asterisks (*) indicate p<0.05 by two-tailed t tests.
Mentions: (A) Map showing the 26 study sites and (B) their annual precipitation. Additional work was conducted at three of the sites, Chamela (white circle), Huatulco (gray diamond), and Santa Rosa (black triangle), that spanned the Mesoamerican dry-forest precipitation gradient.

Bottom Line: Abiotic environmental variables strongly affect the outcomes of species interactions.A model of the carbon trade-offs for the mutualistic partners shows that the observed strategies can arise from the carbon costs of rare but extreme events of herbivory in the rainy season.Thus, water limitation, together with the risk of herbivory, increases the strength of a carbon-based mutualism.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Stanford University, Stanford, California, United States of America ; Michigan Society of Fellows, University of Michigan, Ann Arbor, Michigan, United States of America ; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, United States of America ; School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan, United States of America.

ABSTRACT
Abiotic environmental variables strongly affect the outcomes of species interactions. For example, mutualistic interactions between species are often stronger when resources are limited. The effect might be indirect: water stress on plants can lead to carbon stress, which could alter carbon-mediated plant mutualisms. In mutualistic ant-plant symbioses, plants host ant colonies that defend them against herbivores. Here we show that the partners' investments in a widespread ant-plant symbiosis increase with water stress across 26 sites along a Mesoamerican precipitation gradient. At lower precipitation levels, Cordia alliodora trees invest more carbon in Azteca ants via phloem-feeding scale insects that provide the ants with sugars, and the ants provide better defense of the carbon-producing leaves. Under water stress, the trees have smaller carbon pools. A model of the carbon trade-offs for the mutualistic partners shows that the observed strategies can arise from the carbon costs of rare but extreme events of herbivory in the rainy season. Thus, water limitation, together with the risk of herbivory, increases the strength of a carbon-based mutualism.

Show MeSH
Related in: MedlinePlus