Interactive effects of light environment and herbivory on growth and productivity of an invasive annual vine, Persicaria perfoliata |
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Authors: | Judith Hough-Goldstein Shane J LaCoss |
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Institution: | (1) Department of Entomology and Wildlife Ecology, University of Delaware, Newark, DE 19716-2160, USA;(2) Present address: DuPont Experimental Station, Building E357 Room 1024H, Route 141, Henry Clay Rd., Wilmington, DE 19880, USA |
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Abstract: | Plant populations often exist in spatially heterogeneous environments with varying light levels, which can affect plant growth
directly through resource availability or indirectly by altering behavior or success of herbivores. The plant vigor hypothesis
predicts that herbivores are more likely to attack vigorously growing plants than those that are suppressed, for example in
more shaded conditions. Plant tolerance of herbivory can also vary under contrasting resource availability. Observations suggest
that damage by Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae), introduced into the United States in 2004 as a biological control agent for mile-a-minute
weed (Persicaria perfoliata L.] H. Gross), is greater in the sun than in shade. We compared weevil densities and plant growth in paired plots in full
sun or under shade cloth; a second experiment included insecticide-treated plots in sun and shade, to assess the ability of
the plant to compensate for herbivore damage. Greater density of weevils and more node damage (indicating internal larval
feeding) were found on P. perfoliata plants growing in sun than on those in shade. Nodes were 14% thicker in the sun, which may have provided better larval habitat.
Biomass produced by plants without weevils in the sun was about twice that produced in any other treatment. Herbivory had
a greater effect on plant growth in the high-light environment than in the shade, apparently because of movement into the
sun and increased feeding there by the monophagous herbivore, R. latipes. Results support the plant vigor hypothesis and suggest that high weevil densities in the sunny habitats favored by P. perfoliata can suppress plant growth, negating the resource advantage to plants growing in the sun. |
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