Document: RIC-3-42-8

Insect herbivory alters competitive interactions in meadows in the French Alps.

CORCKET, E.* ¹, R.M.CALLAWAY ² and R.MICHALET ²

University J. Fourier, Grenoble, France ¹
University of Montana, Missoula, MT, USA ²

Abstract:
Abandonment of farms in the foothills of the western Alps has led to substantial changes in grassland community composition. Foothill meadows once dominated by Bromus erectus are being rapidly invaded by the highly competitive but grazing-intolerant, Brachypodium pinnatum. This successional change corresponds with a substantial decrease in total plant species diversity. Because previous field experiments indicate that Brachypodium is also more susceptible to insect herbivory than Bromus, we conducted a field experiment in which the growth rates of Bromus and Brachypodium were compared with and without interspecific neighbors and in plots sprayed with insecticide versus control plots. We found that both Bromus and Brachypodium were grazed by grasshoppers, but the leaves of Brachypodium were more damaged than those of Bromus in the control (no insecticide) plots. Furthermore, without neighbors, sprayed Brachypodium produced more leaves than Bromus. These results demonstrate that grazing by insects, like that of livestock, disproportionally reduces the competitive ability of the dominant competitor, Brachypodium, and that such indirect interactions may play a crucial role in maintaining species diversity in historical grasslands in the French Alps.

Keywords: Biodiversity, Competition, European Alps, Grassland, Insect herbivory

This abstract is being presented at: 8:15 AM in session:
Oral Session #26: Invertebrate Herbivore - Plant Interactions.