Shit Happens! (parte II)

Parte I.

"Hutchinson formalized naturalistic images of the niche of biotic populations and defined the fundamental niche of a population as the hypervolume of environmental space formed by the set of points for which the population's growth rate (fitness) is nonnegative. In other words, the fundamental niche consists of the set of all environmental conditions in which the population can grow or at least sustain its numbers. By extension, the fundamental niche of an organizational form consists of the social, economic, and political conditions that can sustain the functioning of organizations that embody the form.
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If two organizational populations rely on completely different kinds of resources and depend on different kinds of social and political institutions, then their fundamental niches do not intersect. Otherwise, they do intersect, and so it makes sense to measure their similarity in terms of the degree of intersection or overlap.3 Intersection in fundamental niches might be thought of as potential competition. In general, the potential for two populations to compete is proportional to the intersection of their fundamental niches. It follows that two populations compete if and only if their fundamental niches intersect.

When two or more populations with intersecting fundamental niches occupy the same system, the expansion of one population changes the conditions of the others' existence. In the case of competition, the presence of the competing population reduces the hypervolume of environmental space in which another population can sustain itself. Hutchinson coined the term realized niche to refer to the restricted environmental space in which a population's growth rate is nonnegative in the presence of competitors. The realized niche is a subset of the fundamental niche and in most realistic cases it is substantially smaller than the fundamental niche.

Except in the highly unusual case of a population isolated from all competitors, all that can be observed in any empirical setting is the realized niche. Suppose that a pair of populations compete for a resource and that one of them can exclude the other from the full range of overlap of their fundamental niches. In this case, the realized niche of the stronger competitor coincides with the fundamental niche, but the realized niche of the weaker competitor is smaller than its fundamental niche. Interestingly, the two realized niches do not intersect in such cases. It follows from the general principles that the absence of an observed niche intersection does not imply the absence of competition in other portions of fundamental niches."

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Trechos retirados de "Dynamics of Organizational Populations - Density, Legitimation, and Competition" de Michael Hannan e Glenn Carroll.