Soil erosion and vegetation cover are negatively related in semiarid slopes due to the influence of erosion on important soil surface properties for plant establishment and development, but also because the removal of seeds and plants. Previous published work concluded that seed mass is the main factor explaining the seed susceptibility to removal by soil erosion but that this susceptibility can be modified by the presence of seed appendages (hairs, wings, awns) and the ability of seeds to segregate mucilage in contact with water. In the present work we first analyzed how the presence of seed appendages and the ability of seeds to segregate mucilage modify the susceptibility of seeds to removal by soil erosion, and then if soil erosion, through its effects on seed removal can explain plant community composition of semiarid slopes. Results indicate that segregation of mucilage reduces seed susceptibility to be removed and that this seed susceptibility to removal is lower for plants living on steep slopes than that of species living in communities of flat sites. We then argue that soil erosion by water has the potential to affect plant communities of semi-arid Mediterranean slopes.