MacArthur studied five closely related species of warblers living on the same tree. He found that all five species were able to co-exist on that tree.
Which of the following best explains this observation?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Behavioural differences in their foraging activities helped them avoid competition.
Gause’s principle says that two closely related species competing for the same resources cannot co-exist indefinitely. Later studies showed that species facing competition may instead evolve ways that let them live together. MacArthur’s warblers are the book’s example: five closely related species lived on the same tree and still co-existed.
Option (1) The competitively superior species was slowly eliminating the other four species. — Incorrect. If one species were wiping out the others, the five species would not be co-existing. The observation says all five lived together on that tree.
Option (2) Resources on the tree were unlimited, so competition could not occur among them. — Incorrect. The book says resources need not be limiting for competition to occur; one species can lower the feeding efficiency of another even when food and space are abundant. So plenty of resources does not by itself rule out competition.
Option (3) Behavioural differences in their foraging activities helped them avoid competition. — Correct. Each species fed in its own way on the same tree. These behavioural differences in foraging divided the resource among them, so they avoided competition and co-existed. This kind of mechanism is called resource partitioning.
Option (4) The five species had a mutualistic relationship with the tree they lived on. — Incorrect. Mutualism benefits both partners, but the warblers and the tree were not studied as partners. The point of the study was how closely related warblers avoided competing with one another.
NCERT Extract:
Population Interactions – “… While they do not rule out the occurrence of interspecific competition in nature, they point out that species facing competition might evolve mechanisms that promote co-existence rather than exclusion. One such mechanism is ‘resource partitioning’. If two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging patterns. MacArthur showed that five closely related species of warblers living on the same tree were able to avoid competition and co-exist due to behavioural differences in their foraging activities.”