Step 1: Understanding the Concept:
In ecology, when two species compete for the same resource, the presence of the superior competitor limits the distribution of the inferior one. Step 2: Detailed Explanation:
1. Identification: The observation that Chthamalus (the smaller barnacle) expands its distribution once Balanus (the larger, superior barnacle) is removed is a classic example of competitive release.
2. Definition: Competitive release occurs when a species whose distribution is restricted biologically because of the presence of a competitively superior species, expands its distributional range dramatically when the competing species is experimentally removed.
3. This demonstrates that Chthamalus is capable of living in the lower intertidal zone but is normally excluded from it by the more aggressive Balanus. Step 3: Final Answer:
The phenomenon is Competitive Release, which is the expansion of a species' niche when a competitor is removed.
