In a field experiment, a species whose distribution was restricted to a small area expanded its distributional range dramatically when a competitively superior species was experimentally removed.
This observation is called:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Competitive release
When a competitively superior species keeps another species out of an area, the weaker species stays restricted to a small area. If the superior species is experimentally removed, the weaker species spreads into the freed area and expands its range dramatically. This is competitive release, and the book counts it as evidence that competition really happens in nature.
Option (1) Resource partitioning — Incorrect. Resource partitioning is how competing species avoid competition, for example by feeding at different times. No species is removed in it.
Option (2) Competitive release — Correct. The restricted species is ‘released’ from competition when the superior competitor is removed, so its range expands.
Option (3) Competitive exclusion — Incorrect. Competitive exclusion is the elimination of the inferior species by the superior one. Here the weaker species grows in range instead.
Option (4) Interference competition — Incorrect. In interference competition, one species lowers the feeding efficiency of another just by being present. It describes the competition itself, not what happens after a competitor is removed.
NCERT Extract:
Population Interactions – “… Another evidence for the occurrence of competition in nature comes from what is called ‘competitive release’. A species whose distribution is restricted to a small geographical area because of the presence of a competitively superior species, is found to expand its distributional range dramatically when the competing species is experimentally removed.”