Ecology: Fundamental vs Realized Niche

Fundamental Niche

• Represents the entire range of conditions and resources that a species could potentially occupy and use, without competition from other species.
• It's a theoretical concept, based on the species' physiological tolerances, resource requirements, and reproductive rate.
• Imagines an ideal scenario where no other species is present, and the species can exploit all available resources.
• Considered the potential space that a species can occupy, in the absence of biotic interactions.
• Influenced by factors like climate, availability of food, water, and shelter.

Realized Niche

• Represents the actual conditions and resources that a species does occupy and use, in the presence of competition and other interactions with other species.
• Often smaller than the fundamental niche, as species are forced to adjust their use of resources or habitats due to competition, predation, and other biotic interactions.
• A response to the presence of other species and the limitations imposed on resource use.
• Reflects the specific niche a species actually occupies, as it is actively shaped by species interactions.
• Determined by the species' abilities, and the competitive exclusion of other species.

Relationship between Fundamental and Realized Niches

• The realized niche is a subset of fundamental niche.
• Competition is a primary driver of niche differentiation; species compete for shared resources, leading to niche partitioning and specialization.
• Predation or other interspecific interactions can create additional limitations, constraining a species to a more restricted portion of the potential niche.
• The realized niche is dynamic, and can evolve over time as conditions and species interactions change.
• The niche breadth of a given species in any given environment is limited by the fundamental niche and narrowed to the realized niche due to the interactions in its existence within that environment.
• In the event of environmental changes, the realized niche may expand (if competitive pressure is reduced), or contract further if environmental factors such as climate or resource limitation change.