Download (PDF 344 KB): https://research.fs.usda.gov/download/treesearch/31302.pdf
Abstract
Invasion biology has focused on the direct effects of plant invasion and has generally overlooked indirect interactions. Here we link theories of invasion biology and herbivory to explore an indirect effect of one invading species on associational herbivory (the effect of neighboring plants on herbivory) of native species. We studied a Great Basin shadscale (
Atriplex confertifolia)-bunchgrass community in western Utah, U.S.A. This community is dominated by native bunchgrasses, invaded by cheatgrass (
Bromus tectorum), and home to large populations of grasshoppers (
Xanthippus corallipes and
Melanoplus confusus). Observations of associational herbivory provided support for the attractant-source hypothesis for one of two native species studied.
Elymus elymoides experienced 43% greater cumulative herbivory of vegetative structures and produced 11X fewer reproductive structures in naturally high- compared to naturally low-density cheatgrass, thus demonstrating associational susceptibility. In contrast,
Poa secunda showed no indication of associational herbivory; its amount of herbivory did not differ in high- compared to low-density cheatgrass patches.
Elymus elymoides remained a viable food source when cheatgrass senesced, whereas
P. secunda entered early summer dormancy. Through indirect effects, invading species may generate important shifts in herbivory on native species.
Parent Publication
Citation
Beckstead, Julie; Meyer, Susan E.; Augsperger, Carol K. 2008. The indirect effects of cheatgrass invasion: Grasshopper herbivory on native grasses determined by neighboring cheatgrass abundance. In: Kitchen, Stanley G.; Pendleton, Rosemary L.; Monaco, Thomas A.; Vernon, Jason, comps. 2008. Proceedings-Shrublands under fire: disturbance and recovery in a changing world; 2006 June 6-8; Cedar City, UT. Proc. RMRS-P-52. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 41-48
