Expression of plant phenotypes can depend on both plant genomes and interactions between plants and the microbes living in, on and near their roots. We understand a growing number of the mechanistic links between plant genotypes and phenotypes, such as defence against herbivory (see brief review in Hubbard et al., ), yet the links between root microbiomes and the comprehensive swathe of plant phenotypes they affect (Friesen et al., ) remain less clear. In this issue of Molecular Ecology, Hubbard et al. () follow microbe- and plant-driven changes in plant defence against hervibory from molecular underpinnings to ecological consequences, contrasting both the metabolites affected and the magnitude of defensive impact. Naively, we might expect plant genomes to drive more variation in phenotype than the root microbiome, but Hubbard et al. () find the opposite, implying profound consequences for plant trait evolution and ecological interactions.
