How does competition affect an organism's population within a community?

Two barnacle species, Chthalamus stellatus & Balanus balanoides, can be found in communities on rocks along the coast. C. stellatus live higher up on the rocks than B. balanoides, who live closer to the surface of the water. In an experiment, all the B. balanoides are removed from the rock and over time the C. stellatus colonized the entire surface of the rock, including the area where only B. balanoides previously lived. In another area, all the C. stellatus were removed but the habitat of B. balanoides did not change. What does this suggest about the relationship between the two species?

In which of the following scenarios is character displacement most likely to occur?