Vacant niche
The subject is intimately tied into a much broader debate on whether ecosystems can reach equilibrium, where they could theoretically become maximally saturated with species.
Hutchinson defined the niche as an n-dimensional hyper-volume whose dimensions correspond to resource gradients over which species are distributed in a unimodal fashion.
• Radical disturbances in a habitat: For example, droughts or forest fires can destroy a flora and fauna partially or completely.
However, in such cases species suitable for the habitat usually survive in the neighbourhood and colonize the vacated niches, leading to a relatively fast re-establishment of the original conditions.
[15] The ground breaking theoretical investigations of Kauffman (1993)[16] and Wolfram (2002)[17] also suggest the existence of a vast number of vacant niches.
As the number of potential local optima is almost infinite, the niche space is largely unsaturated and species have little opportunity for interspecific competition.
The diversity of marine benthos, i.e. the organisms living near the seabed, though interrupted by some collapses and plateaus has increased from the Cambrian to the Recent.
However, altogether the view prevails that individuals and species are densely packed and that interspecific competition is of paramount significance.
Using SES values (standardized effect sizes) for various groups, which can be used as approximate predictors of the filling of niche space, Gotelli and Rohde (2002)[23] have shown that SES values are high for large and vagile species or for those which occur in large population densities, and that they are low for animal species which occur in small population densities and/or are of small body size and have little vagility.
However, some authors who have contributed most to the formulation of the modern niche concept (Hutchinson, Elton) apparently saw no difficulties in using the term.
But many recent studies, some empirical, some theoretical, have provided support for the alternate view that nonequilibrium conditions are widespread.
[12] In the German literature, an alternate term for vacant niches has found some acceptance - that of freie ökologische Lizens (free ecological license).
[24] It has been argued that this conceptualization has a disadvantage in that it does not convey immediately and easily what is meant, furthermore the concept does not correspond exactly to the term "vacant niche".
