Multidimensional niche

 Multidimensional Niche

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.

Figure 1. Two plots of the fitnesses of two organismic units, A and B, versus their position along two environmental gradients, x and y. (a) A three-dimensional plot with a fitness axis. (b) A two-dimensional

1. 1. plot with the fitness axis omitted; low, medium, and high fitness represented by contour lines.

• Figure 2. A plot of fitness along three different environmental gradients, x, y, and z, showing zones of low and high fitness.

Hutchinson designates the entire set of optimal conditions under which a given organismic unit can live and replace itself as its fundamental niche, which can then be represented as a set of points in environmental space. The fundamental niche is thus a hypothetical, idealized niche in which the organism encounters no "enemies" such as competitors or predators and in which its physical environment is optimal. In contrast, the actual set of conditions under which an organism exists, which is always less than or equal to the fundamental niche, is termed its realized niche. The realized niche takes into account various forces that restrict an organismic unit, such as competition and perhaps predation. The fundamental niche is sometimes referred to as the pre-competitive or virtual niche, whereas the realized niche is the post-competitive or actual niche (however, this terminology neglects factors other than competition -- such as predation -- that might restrict the occupied region of the fundamental niche). These two concepts are thus somewhat analogous to the notions of r_max and r_actual

There are some factor that give some effect for the exsistence of an organism. Environmental Factor that give effect for the exsistence of organism lis not only environmental condition like temperature, light, humidity, salinity, but resources that is need by organism like food or a place to live.

Two organismics can have same niche.  Niche overlap occurs when two organismic units use the same resources or other environmental variables. In Hutchinson's terminology, each n-dimensional hypervolume includes part of the other, or some points in the two sets that constitute their realized niches are identical. Overlap is complete when two organismic units have identical niches; there is no overlap if two niches are completely disparate. Usually, niches overlap only partially, with some resources being shared and others being used exclusively by each organismic unit.

Hutchinson assum that the environment is fully saturated and that niche overlap cannot be tolerated for any period of time; hence, competitive exclusion must occur in the overlapping parts of any two niches.