Background/Question/Methods Two key strides have been made in the last decade in understanding the underlying causes of variation among communities. First, community genetics studies have examined the role of intraspecific genetic variation in determining the diversity of associated communities. Second, the development of metacommunity ecology has adopted a spatially explicit framework in which the structure of local communities results from a combination of local species interactions and regional migration. We combine both community genetics and metacommunity perspectives to ask whether host-plant genetic variation within tall goldenrod (Solidago altissima) structures a diverse community of arthropods that occur within distinct habitat ‘patches' - rosette leaf galls created by the galling midge, Rhopalomyia solidaginis.

Results/Conclusions We found that genetic variation determined inquiline diversity within galls from local (within-gall) to regional (among-gall) spatial scales. Host-plant genetic variation also determined herbivore and predator inquiline diversity, but herbivores responded predominantly at the local level (alpha diversity), while predators responded at larger spatial scales (beta and gamma diversity). Our results show that incorporating spatial scaling is essential for predicting how different community members perceive and respond to genetically variable host-plant traits. Furthermore, our results provide some of the first empirical evidence that genetically-based variation in local patches can drive metacommunity structure.