Intra-specific variation in plant associated herbivore communities is phylogenetically structured in Brassicaceae

As a result of co-evolution between plants and herbivores, related plants often interact with similar herbivore communities. Variation in plant-herbivore interactions is determined by variation in underlying functional traits and by ecological and stochastic processes. Hence, typically only a subset of possible interactions is realized on individual plants. We show that insect herbivore communities assembling on individual plants are structured by plant phylogeny among twelve species in two phylogenetic lineages of Brassicaceae. This community sorting to plant phylogeny was retained when splitting the community according to herbivore feeding guilds. Relative abundance of herbivores as well as the size of the community structured community dissimilarity among plant species. Importantly, the amount of intra-specific variation in realized plant-herbivore interactions is also phylogenetically structured. We argue that variability in realized interactions that is not directly structured by plant traits is ecologically relevant and must be considered in the evolution of plant defences.