Do Ecological Principles Encompass Other Proposed Ecological Theories Niche Theory

Hutchinson (1957, 1965) suggested that an organism's niche could be visualized as a multidimensional space, or hypervolume, formed by the combination of gradients of each single environmental condition to which the organism was exposed. The N-environmental exposure conditions form a set of N-intersecting axes within which one can define an N-dimensional niche hypervolume unique to each species. The niche hypervolume is comprised of all combinations of the environmental conditions that permit an individual of that species to survive and reproduce indefinitely (Huthchinson's Fundamental niche). Hutchinson distinguished the fundamental niche, defined as the maximum inhabitable hypervolume in the absence of competition, predation, and parasitism, from the realized niche, which is a smaller hypervolume occupied when the species is under biotic constraints. Hutchinson also defined the niche breadth for an organism as the habitable range, between the maximum and the minimum, for each particular environmental variable. Thus, the niche breadth is the projection of the niche hypervolume onto each individual environment.

Following Hutchinson's distinction, niche refers to the requirements of the species and habitat refers to a physical place in the environment where those requirements can be met (Figure 8.12).

To interpret Figure 8.12 with regard to the distribution of species 1 and 2, one must understand Hutchinson's emphasis on the fundamental importance of competition as a force influencing the distribution of species in nature. Hutchinson argued that in the face of competition, a species will not utilize its entire fundamental niche, but rather the realized niche actually used by the species will be smaller, only consisting of those portions of the fundamental niche where the species is competitively dominant. As a result of competitive exclusion, according to Hutchinson, the realized niche is smaller than the fundamental niche, and a species may frequently be absent from portions of its fundamental niche because of competition with other species. Obviously, the more limited resources two populations have in common (i.e. the more similar their niches are), the greater the impact of competition (all else being equal). In particular, niche is used to describe and analyze:

(1) Ways in which different species interact (including competition, resource portioning, exclusion, or coexistence).

(2) Why some species are rare and others abundant.

(3) What determines geographical distribution of a given species?

(4) What determines structure and stability of multi-species communities?

Food distribution

Temperature and species distribution H 03 04 05

Food distribution

Temperature and species distribution H 03 04 05

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