2.1.28 (HL)—Fundamental and realized niches

The fundamental niche is the potential range without biotic restriction; the realized niche is the range actually occupied after competition, predation and other interactions.

Compare conditions with and without the competitor or predator. Biotic constraints can narrow the observed range.

Chthamalus barnacles survive lower on shore when a competitor is removed, so competition narrows their realized niche.

Fundamental niche; realized niche excludes the occupied range after competition.

Realized niche is not always the physiologically ideal range.