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Benefits for plants in ant-plant protective mutualisms: a meta-analysis.

Trager MD, Bhotika S, Hostetler JA, Andrade GV, Rodriguez-Cabal MA, McKeon CS, Osenberg CW, Bolker BM - PLoS ONE (2010)

Bottom Line: Studies that experimentally excluded ants reported a smaller effect of ant protection on plant reproduction than studies that relied upon natural variation in ant presence, suggesting that study methods can affect results in these systems.Of the ecological variables included in our analysis, only plant life history (i.e., annual or perennial) explained variation in the protective benefit of mutualistic ants: presence of ants benefitted reproduction of perennials significantly more than that of annuals.These results contrast with other quantitative reviews of these relationships that did not include plant life history as an explanatory factor and raise several questions to guide future research on ant-plant protection mutualisms.

View Article: PubMed Central - PubMed

Affiliation: Florida Museum of Natural History, University of Florida, Gainesville, Florida, United States of America. mtrager@ufl.edu

ABSTRACT
Costs and benefits for partners in mutualistic interactions can vary greatly, but surprisingly little is known about the factors that drive this variation across systems. We conducted a meta-analysis of ant-plant protective mutualisms to quantify the effects of ant defenders on plant reproductive output, to evaluate if reproductive effects were predicted from reductions in herbivory and to identify characteristics of the plants, ants and environment that explained variation in ant protection. We also compared our approach with two other recent meta-analyses on ant-plant mutualisms, emphasizing differences in our methodology (using a weighted linear mixed effects model) and our focus on plant reproduction rather than herbivore damage. Based on 59 ant and plant species pairs, ant presence increased plant reproductive output by 49% and reduced herbivory by 62%. The effects on herbivory and reproduction within systems were positively correlated, but the slope of this relationship (0.75) indicated that tolerance to foliar herbivory may be a common plant response to absence of ant guards. Furthermore, the relationship between foliar damage and reproduction varied substantially among systems, suggesting that herbivore damage is not a reliable surrogate for fitness consequences of ant protection. Studies that experimentally excluded ants reported a smaller effect of ant protection on plant reproduction than studies that relied upon natural variation in ant presence, suggesting that study methods can affect results in these systems. Of the ecological variables included in our analysis, only plant life history (i.e., annual or perennial) explained variation in the protective benefit of mutualistic ants: presence of ants benefitted reproduction of perennials significantly more than that of annuals. These results contrast with other quantitative reviews of these relationships that did not include plant life history as an explanatory factor and raise several questions to guide future research on ant-plant protection mutualisms.

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Effect sizes (means ±95% confidence intervals) for responses of (A) plant reproduction and (B) herbivore damage to ant presence, ordered by magnitude.For both panels, the solid line indicates no effect (log-ratio  = 0) and the dashed line indicates the weighted mean effect size. Circles represent observational studies and triangles represent experimental studies; note that the y-axis scales are different for (A) and (B).
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pone-0014308-g001: Effect sizes (means ±95% confidence intervals) for responses of (A) plant reproduction and (B) herbivore damage to ant presence, ordered by magnitude.For both panels, the solid line indicates no effect (log-ratio  = 0) and the dashed line indicates the weighted mean effect size. Circles represent observational studies and triangles represent experimental studies; note that the y-axis scales are different for (A) and (B).

Mentions: Our analyses included reproductive data from 31 journal articles, comprising 28 plant species and 59 ant and plant species combinations (Table S1). Of these studies, 19 also included data on foliar herbivory. The effect sizes varied substantially but, on average, ant presence increased plant reproductive output by 49% ( = 0.40±0.074 SE) and decreased foliar herbivory by 62% ( = 0.96±0.23 SE: Fig. 1).


Benefits for plants in ant-plant protective mutualisms: a meta-analysis.

Trager MD, Bhotika S, Hostetler JA, Andrade GV, Rodriguez-Cabal MA, McKeon CS, Osenberg CW, Bolker BM - PLoS ONE (2010)

Effect sizes (means ±95% confidence intervals) for responses of (A) plant reproduction and (B) herbivore damage to ant presence, ordered by magnitude.For both panels, the solid line indicates no effect (log-ratio  = 0) and the dashed line indicates the weighted mean effect size. Circles represent observational studies and triangles represent experimental studies; note that the y-axis scales are different for (A) and (B).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3008678&req=5

pone-0014308-g001: Effect sizes (means ±95% confidence intervals) for responses of (A) plant reproduction and (B) herbivore damage to ant presence, ordered by magnitude.For both panels, the solid line indicates no effect (log-ratio  = 0) and the dashed line indicates the weighted mean effect size. Circles represent observational studies and triangles represent experimental studies; note that the y-axis scales are different for (A) and (B).
Mentions: Our analyses included reproductive data from 31 journal articles, comprising 28 plant species and 59 ant and plant species combinations (Table S1). Of these studies, 19 also included data on foliar herbivory. The effect sizes varied substantially but, on average, ant presence increased plant reproductive output by 49% ( = 0.40±0.074 SE) and decreased foliar herbivory by 62% ( = 0.96±0.23 SE: Fig. 1).

Bottom Line: Studies that experimentally excluded ants reported a smaller effect of ant protection on plant reproduction than studies that relied upon natural variation in ant presence, suggesting that study methods can affect results in these systems.Of the ecological variables included in our analysis, only plant life history (i.e., annual or perennial) explained variation in the protective benefit of mutualistic ants: presence of ants benefitted reproduction of perennials significantly more than that of annuals.These results contrast with other quantitative reviews of these relationships that did not include plant life history as an explanatory factor and raise several questions to guide future research on ant-plant protection mutualisms.

View Article: PubMed Central - PubMed

Affiliation: Florida Museum of Natural History, University of Florida, Gainesville, Florida, United States of America. mtrager@ufl.edu

ABSTRACT
Costs and benefits for partners in mutualistic interactions can vary greatly, but surprisingly little is known about the factors that drive this variation across systems. We conducted a meta-analysis of ant-plant protective mutualisms to quantify the effects of ant defenders on plant reproductive output, to evaluate if reproductive effects were predicted from reductions in herbivory and to identify characteristics of the plants, ants and environment that explained variation in ant protection. We also compared our approach with two other recent meta-analyses on ant-plant mutualisms, emphasizing differences in our methodology (using a weighted linear mixed effects model) and our focus on plant reproduction rather than herbivore damage. Based on 59 ant and plant species pairs, ant presence increased plant reproductive output by 49% and reduced herbivory by 62%. The effects on herbivory and reproduction within systems were positively correlated, but the slope of this relationship (0.75) indicated that tolerance to foliar herbivory may be a common plant response to absence of ant guards. Furthermore, the relationship between foliar damage and reproduction varied substantially among systems, suggesting that herbivore damage is not a reliable surrogate for fitness consequences of ant protection. Studies that experimentally excluded ants reported a smaller effect of ant protection on plant reproduction than studies that relied upon natural variation in ant presence, suggesting that study methods can affect results in these systems. Of the ecological variables included in our analysis, only plant life history (i.e., annual or perennial) explained variation in the protective benefit of mutualistic ants: presence of ants benefitted reproduction of perennials significantly more than that of annuals. These results contrast with other quantitative reviews of these relationships that did not include plant life history as an explanatory factor and raise several questions to guide future research on ant-plant protection mutualisms.

Show MeSH
Related in: MedlinePlus