Small consumers like microbial pathogens and insect herbivores have long been suggested as drivers of host community composition. Small consumers reduce biomass and oftentimes promote host diversity, but their impact on the functional composition of plant communities has rarely been studied. Plant defenses, involved in ecological trade-offs, vary among species but can be costly. Thus, consumer pressure may determine community composition by shaping a community's trait composition. Using long-term consumer exclusion experiments replicated in an experimentally planted and a naturally assembling grassland, we show that small consumers push their host communities towards high structural defense, low apparency, and low palatability. Small-scale, short-term studies in natural ecosystems may overlook this, due to legacy effects of past consumption, ongoing consumption in the surroundings and dispersal limitation. The consumer-induced trait shifts may alter ecosystem functions and potentially slow down process rates in ecosystems.
