Competitive exclusion
Step-by-step explanation:
Competitive exclusion principle states that if two species compete for same resources then they cannot coexist together that is why Chthamalus is excluded by zones from Semibalanus balanoides
Zonation of barnacles is influenced by competition
Chthamalus not only occupy the mid-shore but survive and grow better than in its normal high-shore zone
Chthamalus is more tolerant of physical stresses than Semibalanus, and can therefore survive in the high-shore, where it has a ‘spatial refuge’ beyond the limits of Semibalanus
In the mid-shore, however, Semibalanus thrives and competitively excludes Chthamalus by undercutting or overgrowing it