Niche Concept

The Niche Concept

A species' niche is its ecological role or "way of life," which is defined by the full set of conditions, resources, and interactions it needs. Each species fits into an ecological community in its own special way and has its own tolerable ranges for many environmental factors. For example, a fish species' niche might be defined partly by ranges of salinity (saltiness), pH (acidity), and temperature it can tolerate, as well as the types of food it can eat.

As we'll see, two organisms with exactly the same niche can't survive in the same habitat (because they compete for exactly the same resources, so one will drive the other to extinction). However, species whose niches only partly overlap may be able to coexist. Also, over long periods of time, they may evolve to make use of more different, or less overlapping, sets of resources.

Hutchinson defines an organism's niche as an n-dimensional hypervolume enclosing the complete range of conditions under which that organism can successfully replace itself. All variables relevant to the life of the organism must be included, and all must be independent of each other. An immediate difficulty with this model of the niche is that not all environmental variables can be nicely ordered linearly. To avoid this problem and to make the entire model more workable, Hutchinson translated his n-dimensional hypervolume formulation into a set theory mode of representation.