Vegetation Structure And Interspecific Interactions Predict Distribution And Abundance Of Solidago Specialist Aphids

Volatile compounds such as terpenes are often used by plants as insect herbivory deterrents, though terpenes broadly act as semiochemicals, both priming nearby plants and providing host recognition for insects. I focused on the interactions of tall goldenrod, Solidago altissima, goldenrod galling insects, and specialist aphids. Gall insects induce a volatile terpene response in Solidago and aphids colonize goldenrod stems with high terpene concentrations. In this system, the goldenrod’s terpene response deters the inducing species while simultaneously promoting aphid colonization. Using spatial mapping techniques, I constructed a biologically-based model of terpene induction, driven by insect galls, in three patches of goldenrod in order to predict areas of aphid colonization. Terpenes were analyzed via gas chromatography in plants sampled at varying distances from insect galls in each patch. Results of terpene sampling were used to develop a spatial model of terpene induction and aphid distribution. Aphid counts were made in each patch and compared to model projections. My analysis revealed that terpenes in the field varied significantly by distance and in a similar way across all patches. My spatial models demonstrated an aphid response to the gall induced terpenes, and when combined with models of vegetation structure, accurately predicted aphid distribution.