What is the term used to describe the phenomenon in which a species, whose distribution is limited due to the presence of a competitively superior species, significantly expands its range when the competing species is experimentally eliminated?

Competitive release

Connell's elegant field experiments on the rocky sea coasts of Scotland provided evidence for competition in nature, specifically through the phenomenon known as "competitive release." In this context, the presence of a competitively superior species restricts the distribution of another species to a small geographical area. However, when the competing species is experimentally removed, the restricted species experiences a significant expansion in its distributional range.

In the case of the rocky sea coasts of Scotland, Connell observed the interaction between two barnacle species: the larger and competitively superior species called Balanus and the smaller species known as Chathamalus. Balanus dominated the intertidal area, effectively excluding Chathamalus from that zone. This exclusion occurred due to the competitive advantage of Balanus, which was better adapted to compete for limited resources in that environment.

However, when Connell conducted experiments by removing Balanus from the intertidal area, he observed a dramatic expansion in the distributional range of Chathamalus. The removal of the competitively superior species, Balanus, created an opportunity for Chathamalus to occupy the previously restricted zone. This expansion in distribution demonstrated the impact of competitive release, as the removal of competition allowed Chathamalus to thrive in an area it was previously excluded from.

Connell's experiments provided empirical evidence for the occurrence of competition and the subsequent effects of competitive release in natural ecosystems. They highlighted how the presence or absence of a competitively superior species can have a significant influence on the distribution and abundance of other species in a given habitat.