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The effect of disturbance on an ant-plant mutualism.

Piovia-Scott J - Oecologia (2010)

Bottom Line: Protective ant-plant mutualisms-where plants provide food or shelter to ants and ants protect the plants from herbivores-are a common feature in many ecological communities, but few studies have examined the effect of disturbance on these interactions.The effect of ant-exclusion did not differ between pruned and unpruned plants, despite the fact that pruned plants had higher ant and herbivore densities, produced more extrafloral nectaries, and had fewer physical defenses.I suggest that compensatory predation by these spiders diminished the effect of ant-exclusion on pruned plants.

View Article: PubMed Central - PubMed

Affiliation: Center for Population Biology, University of California, Davis, CA 95616-8755, USA. jpioviascott@ucdavis.edu

ABSTRACT
Protective ant-plant mutualisms-where plants provide food or shelter to ants and ants protect the plants from herbivores-are a common feature in many ecological communities, but few studies have examined the effect of disturbance on these interactions. Disturbance may affect the relationship between plants and their associated ant mutualists by increasing the plants' susceptibility to herbivores, changing the amount of reward provided for the ants, and altering the abundance of ants and other predators. Pruning was used to simulate the damage to buttonwood mangrove (Conocarpus erectus) caused by hurricanes. Pruned plants grew faster than unpruned plants, produced lower levels of physical anti-herbivore defenses (trichomes, toughness), and higher levels of chemical defenses (tannins) and extrafloral nectaries. Thus, simulated hurricane damage increased plant growth and the amount of reward provided to ant mutualists, but did not have consistent effects on other anti-herbivore defenses. Both herbivores and ants increased in abundance on pruned plants, indicating that the effects of simulated hurricane damage on plant traits were propagated to higher trophic levels. Ant-exclusion led to higher leaf damage on both pruned and upruned plants. The effect of ant-exclusion did not differ between pruned and unpruned plants, despite the fact that pruned plants had higher ant and herbivore densities, produced more extrafloral nectaries, and had fewer physical defenses. Another common predator, clubionid spiders, increased in abundance on pruned plants from which ants had been excluded. I suggest that compensatory predation by these spiders diminished the effect of ant-exclusion on pruned plants.

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The effect of factorial manipulations of pruning and ant-exclusion on Conocarpus erectus: a trichomes b toughness c tannins d EFNs per leaf e growth and f leaf damage (n = 10 plants for each treatment combination). The verticaldotted line represents the initiation of treatments. Means and standard errors are shown, with the predicted mean of post-treatment samples for each plant presented at the right of each plot. Predictions were obtained from the mixed models described in the text. Statistical significance of tests comparing pruned and unpruned plants are shown: ***p < 0.001, **p < 0.01, *p < 0.05, +p < 0.1
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Fig1: The effect of factorial manipulations of pruning and ant-exclusion on Conocarpus erectus: a trichomes b toughness c tannins d EFNs per leaf e growth and f leaf damage (n = 10 plants for each treatment combination). The verticaldotted line represents the initiation of treatments. Means and standard errors are shown, with the predicted mean of post-treatment samples for each plant presented at the right of each plot. Predictions were obtained from the mixed models described in the text. Statistical significance of tests comparing pruned and unpruned plants are shown: ***p < 0.001, **p < 0.01, *p < 0.05, +p < 0.1

Mentions: Anti-herbivore defenses differed between pruned and unpruned plants (MANOVA: F4,25 = 35.7, p < 0.0001; Fig. 1a–d), with pruned plants possessing fewer physical defenses than unpruned plants, but higher levels of chemical and indirect defenses. Mean trichome density was reduced by 21% on pruned plants (F1,28 = 31.1, p < 0.0001; Fig. 1a) and mean toughness was reduced by 27% (F1,28 = 60.5, p < 0.0001; Fig. 1b); in both cases, the difference between pruned and unpruned plants diminished over the course of the experiment (pruning × date interaction: F2,69 = 16.6, p < 0.0001, F2,69 = 44.6, p < 0.0001, respectively). In contrast, pruned plants tended to have higher levels of chemical and indirect defenses than unpruned plants. Mean tannin concentration was 30% higher in pruned plants than in unpruned plants (F1,28 = 11.8, p = 0.002; Fig. 1c) and pruned plants had 33% more EFNs than unpruned plants (F1,28 = 5.6, p = 0.03; Fig. 1d). For tannins, the difference between pruned and unpruned plants decreased during the course of the experiment (date × pruning interaction: F2,64 = 9.9, p = 0.0002; Fig. 1c), while EFNs did not show an effect of pruning until May 2008 (date × pruning interaction: F2,58 = 12.9, p < 0.0001; Fig. 1d).Fig. 1


The effect of disturbance on an ant-plant mutualism.

Piovia-Scott J - Oecologia (2010)

The effect of factorial manipulations of pruning and ant-exclusion on Conocarpus erectus: a trichomes b toughness c tannins d EFNs per leaf e growth and f leaf damage (n = 10 plants for each treatment combination). The verticaldotted line represents the initiation of treatments. Means and standard errors are shown, with the predicted mean of post-treatment samples for each plant presented at the right of each plot. Predictions were obtained from the mixed models described in the text. Statistical significance of tests comparing pruned and unpruned plants are shown: ***p < 0.001, **p < 0.01, *p < 0.05, +p < 0.1
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3094537&req=5

Fig1: The effect of factorial manipulations of pruning and ant-exclusion on Conocarpus erectus: a trichomes b toughness c tannins d EFNs per leaf e growth and f leaf damage (n = 10 plants for each treatment combination). The verticaldotted line represents the initiation of treatments. Means and standard errors are shown, with the predicted mean of post-treatment samples for each plant presented at the right of each plot. Predictions were obtained from the mixed models described in the text. Statistical significance of tests comparing pruned and unpruned plants are shown: ***p < 0.001, **p < 0.01, *p < 0.05, +p < 0.1
Mentions: Anti-herbivore defenses differed between pruned and unpruned plants (MANOVA: F4,25 = 35.7, p < 0.0001; Fig. 1a–d), with pruned plants possessing fewer physical defenses than unpruned plants, but higher levels of chemical and indirect defenses. Mean trichome density was reduced by 21% on pruned plants (F1,28 = 31.1, p < 0.0001; Fig. 1a) and mean toughness was reduced by 27% (F1,28 = 60.5, p < 0.0001; Fig. 1b); in both cases, the difference between pruned and unpruned plants diminished over the course of the experiment (pruning × date interaction: F2,69 = 16.6, p < 0.0001, F2,69 = 44.6, p < 0.0001, respectively). In contrast, pruned plants tended to have higher levels of chemical and indirect defenses than unpruned plants. Mean tannin concentration was 30% higher in pruned plants than in unpruned plants (F1,28 = 11.8, p = 0.002; Fig. 1c) and pruned plants had 33% more EFNs than unpruned plants (F1,28 = 5.6, p = 0.03; Fig. 1d). For tannins, the difference between pruned and unpruned plants decreased during the course of the experiment (date × pruning interaction: F2,64 = 9.9, p = 0.0002; Fig. 1c), while EFNs did not show an effect of pruning until May 2008 (date × pruning interaction: F2,58 = 12.9, p < 0.0001; Fig. 1d).Fig. 1

Bottom Line: Protective ant-plant mutualisms-where plants provide food or shelter to ants and ants protect the plants from herbivores-are a common feature in many ecological communities, but few studies have examined the effect of disturbance on these interactions.The effect of ant-exclusion did not differ between pruned and unpruned plants, despite the fact that pruned plants had higher ant and herbivore densities, produced more extrafloral nectaries, and had fewer physical defenses.I suggest that compensatory predation by these spiders diminished the effect of ant-exclusion on pruned plants.

View Article: PubMed Central - PubMed

Affiliation: Center for Population Biology, University of California, Davis, CA 95616-8755, USA. jpioviascott@ucdavis.edu

ABSTRACT
Protective ant-plant mutualisms-where plants provide food or shelter to ants and ants protect the plants from herbivores-are a common feature in many ecological communities, but few studies have examined the effect of disturbance on these interactions. Disturbance may affect the relationship between plants and their associated ant mutualists by increasing the plants' susceptibility to herbivores, changing the amount of reward provided for the ants, and altering the abundance of ants and other predators. Pruning was used to simulate the damage to buttonwood mangrove (Conocarpus erectus) caused by hurricanes. Pruned plants grew faster than unpruned plants, produced lower levels of physical anti-herbivore defenses (trichomes, toughness), and higher levels of chemical defenses (tannins) and extrafloral nectaries. Thus, simulated hurricane damage increased plant growth and the amount of reward provided to ant mutualists, but did not have consistent effects on other anti-herbivore defenses. Both herbivores and ants increased in abundance on pruned plants, indicating that the effects of simulated hurricane damage on plant traits were propagated to higher trophic levels. Ant-exclusion led to higher leaf damage on both pruned and upruned plants. The effect of ant-exclusion did not differ between pruned and unpruned plants, despite the fact that pruned plants had higher ant and herbivore densities, produced more extrafloral nectaries, and had fewer physical defenses. Another common predator, clubionid spiders, increased in abundance on pruned plants from which ants had been excluded. I suggest that compensatory predation by these spiders diminished the effect of ant-exclusion on pruned plants.

Show MeSH
Related in: MedlinePlus