Can Insect Herbivory Control Grassland Composition, Productivity and Dynamics: An Alternative View

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9615184 CARSON For more than 35 years evidence has accumulated that herbivorous insects will not harm native prairies and grasslands (with the exception of grasshoppers). New evidence suggests, however, that insect attack dramatically reduces the diversity and abundance of broad-leaved herbaceous plants, or forbs, that occur in North American prairies. Damage by certain insects may lead to less diverse prairies that are more susceptible to environmental perturbations. The goal of this research is to determine if damage by beetles, native specialist insect herbivores, control the distribution and abundance of three species of native, clonal goldenrods which form large, productive patches in the prairies of Minnesota. The investigators' hypothesis, based on work by Grover is that specialist insects, such as beetles, play a "keystone" role especially in infertile grasslands by reducing the abundance of dominant plant species. "Patch-centered" insect exclusion, transplant, and competition experiments will be conducted in native prairies in Minnesota to determine whether beetles reduce the abundance of goldenrods in natural grasslands. This work will help us understand how some plant species become rare or threatened by natural processes that are not strongly related to human activities. Furthermore, many of the most important agricultural crops are grasses (e.g., corn and wheat) and are plagued by weeds including a large number of forbs. Understanding and identifying those insects that damage forbs and not grasses could lead to a greater use of biological control agents (e.g., insects) to control weeds. This would ultimately reduce the use of expensive and potentially harmful herbicides.