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Herbivores highly reduce the performance of many plant species. However, little empirical information exists on the real effect that these organisms have on plant populations. With a long-term (seven-year) ungulate exclusion experiment in two areas of southeastern Spain, I demonstrated that these organisms can affect not only individual performance, but also the population dynamics and spatial structure of two short-lived monocarpic herbs, Erysimum mediohispanicum and E. baeticum. There was between-year and among-microhabitat variability in damage, with plants growing under shrubs being less damaged than those growing in open sites. Ungulates consumed flowers and fruits, severely decreasing plant reproductive output. The postdispersal seed predation rate increased after ungulates were excluded, presumably as a consequence of the relaxation of competition between seed predators and ungulates. The effect of ungulates on Erysimum early establishment was nonsignificant, although > 50% of Erysimum seedlings died due to ungulate trampling. The exclusion experiment also revealed that, as a consequence of their impact on seed production, ungulates affected the population dynamics of their host plants; their removal produced a significant increase in the abundance of the two studied plant species. Furthermore, habitat distribution of plants was also influenced by the activity of ungulates. In control plots, most Erysimum individuals grew under the canopy of co-occurring shrubs. In contrast, a dramatic spatial redistribution of plants occurred in ungulate-excluded plots, where they started to colonize open sites. Consequently, the spatial structure of the plants excluded from ungulates significantly differed from that in control plots and became statistically similar to the structure expected according to the cover of every microhabitat. Finally, this experiment revealed that, for plants inhabiting heterogeneous landscapes, abundance and spatial structure are tightly related. Thus, I found that abundance increased in ungulate-excluded plots due not to a general and homogeneous increase, but to a significant increase in those microhabitats inaccessible to ungulates in control plots. These findings suggest that herbivory effects on plants are intricate, affecting not only their performance or population dynamics, but also their habitat distribution and niche structure.