Similar responses of insect herbivores to leaf fluctuating asymmetry
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Fluctuating asymmetry (FA) represents small, random variation from symmetry and it has been used as an indicator of plant quality and susceptibility to herbivory. In this study, the effects of FA on the responses of distinct herbivore species belonging to several guilds were examined along an environmental gradient in south Florida. This approach was chosen because it relies on a multi-species approach to the study of fluctuating asymmetry and patterns of herbivory between and within plants along an environmental gradient of salinity and plant stress. To examine differences in FA between and within plant communities, seven plant species were investigated. Four of these plants were coastal species and three species occurred in upland communities. Levels of FA were assessed before herbivory and plants were followed for the whole herbivory season in 2006. Coastal plants exhibited significantly higher salt concentration, higher percentage of asymmetric leaves and higher asymmetry levels than upland plants. Herbivore abundance varied widely amongst the seven species studied, but quantitative syntheses of our results indicated significant and positive responses of insect herbivores to leaf asymmetry: insects were 25.11% more abundant on more asymmetric plants and stronger effects of asymmetry were observed for leaf miners compared to gall-formers. As demonstrated by other recent studies, FA might be used as a reliable stress indicator, leading to similar responses of insect herbivores to variation in leaf symmetry.
KeywordsFluctuating asymmetry Plant stress Leaf miners Gall-formers Herbivory Coastal-upland comparisons
This research was supported by the National Science Foundation (NSF grant DEB 03-15190) and T. Cornelissen was partially supported by the Brazilian National Research Council CNPq through a graduate fellowship (grant number 200064/01-0). We thank Andrey Castro and Tere Albarracin for their invaluable help in the field and Sylvia Luckanewick for help in laboratory analyses and leaf measurements.
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