The ecological niche can be defined in terms of habitat, feeding relationships and interactions with other species.
Ecological niche: The role and space that an organism fills in an ecosystem, including all its interactions with the biotic and abiotic factors of its environment.
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There are two types of ecological niche:
- Fundamental niche – all the potential resources that a species can use in its environment. Requires the absence of competition.
- Realised niche – some habitats and resources are not available because competitors occupy them. This is what the species actually uses.
Realised niches are narrower than fundamental niches, therefore the species occupies a narrower range of habitats than it would in the absence of competition. The realised niche can be regarded as a ‘competitive refuge’.