Niche
From EvoWiki
The niche has a variety of related meanings within Ecology, Evolutionary biology and Anthropology.
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Ecological niche concepts
Grinnellian niche: The Ecologist J. Grinnell was the first to use the term niche to describe the relationship between a species and its environment. His conceptualization pictured the niche as being the sum of the habitat requirements of a species. Niches in his view could be differentially occupied and vacated by species (Grinnell, 1917).
Eltonian niche: C. Elton is most famous for his work on understanding the flow of energy throughout ecosystems via food-webs. He devised a niche concept that was based on the role of a species in its environment in terms of its position within a food-web (Elton, 1927).
Hutchinsonian niche: G. E. Hutchinson, perhaps the most famous Ecologist who ever lived, developed a fully quantitative and revolutionary conception of the niche, based partly on the work of G. F. Gause who developed the competative exclusion principle. He suggested that the niche could be represented mathematically as an n-dimensional hypervolume whose dimensions corresponded to resource/environmental gradients over which the species in question was distributed in some unimodal fashion. The niche according to Hutchinson could be divided into two facets; the realized niche which is the sum of a species niche dimensions that are unique to that particular species (if any) and the fundamental niche, which is the totality of a species niche dimensions, both shared with other species and unshared. The Hutchinsonian niche is defined by the species that it contains, in the absence of a species the niche can not exist in any Hutchinsonian sense, also competition can be measured by the magnitude of species nice overlap. (Hutchinson, 1944).
Chase and Leibold's ecological niche: J. Chase and M. Leibold have attempted to re-evaluate the usefulness of the niche concept after it fell into scientific 'disrepute' in the 1960s due to hypothetico-deductive criticisms concerning the lack of adequate null hypotheses when it was applied for the purpose of making long term and long range biodiversity predictions. Their fundamental premise is to address the niche in terms of criticisms levelled against it by biogeographers and neutralists, especially advocates of S. Hubbell's particular variety of neutralism. They 're-work' the niche concept to take into account the per-capita effects of a species on its environment and the idea that a minimum number of resources are required to sustain a species fittness (Chase and Leibold, 2003).
Evolutionary niches
This concept of niche is central to any understanding of Evolutionary Ecology. F. J. Odling-Smee et al's central thesis of niche construction is a by product of ecological engineering. According to their models this process is thought to drive evolution through species facilitated environmental modifications which generate feedback-selection pressures, which in turn effect an evolutionary change to the species. Their evolutionary niche counted amongst its dimensions the natural selection histories of the species which define it. Chase and Leibold build upon this with reference to the work of P. Amarasekare, who saw parallels between the process of ecological sorting, where species traits are fixed through 'sorting' on the community level and ecologically 'dead end' species are eliminated, with phenotypic sorting, which entails very similar processes. Relating gene frequency changes to resource gradient changes is thought to be one productive way to look at the evolutionary niche (Odling-Smee et al, 2003, Chase and Leibold, 2003).
Cultural niches
Similar to the evolutionary niche, the cultural niche is (for the time being) exclusive to Humans, and according to F. Odling-Smee, K. Laland and M. Feldman who created the concept, it takes the sum of Humanities interactions with both its self and its environment as its dimensions. What distinguishes it from other niche concepts is the fact that Humanity is able to retain information about its encounters and interactions through memory (both biological and external) which it can share and use to inform the nature of subsequent interactions. Such changes in culture are thought to have been a driving force in the evolution of modern Humans, especially in as much as the evolution of intelligence is concerned (Odling-Smee et al, 2003).
Vacant niches
Ecologists are divided on the question of whether or not it is possible to have such a thing as a vacant niche. The debate focuses largely on the question of whether or not ecosystems can exist in a species 'saturated' state or not (Chase and Leibold, 2003). There is evidence that ecosystems never reach saturation, even when disruption is controlled for - implying the existence of unutilized resources and what some ecologists choose to call 'vacant niches'. The largely qualitative framework of Grinnell and Elton seemed to imply the existence of niche vacancies as either unclaimed areas of Habitat or unclaimed links in a food web. Hutchinsonian niche theory however, as has already been mentioned, precludes the possibility of vacant niches existing as in order for there to be a Hutchinsonian niche, there needs to be a species to define it in the first place. The same Can be said for the framework of Chase and Leibold - their models preclude the existence of vacant niches. A recent entrant into the debate is a model proposed by the Ecologist M. Woodley and the Mathematician K. Sikes. They have suggested that vacant niches can in fact exist within a Hutchinsonian context, but only under very special conditions. In order for a vacant niche to exist it requires the presence of other species niches to 'surround' but not occupy the space of the vacancy. These 'occupied' niches parameterize the vacancy and 'define' it through the absence of these species along certain regions of resource gradients. According to Woodley and Sikes these vacant niches would only exist for very brief periods of time as they would get filled by either new species or one of the parameterizing species rapidly, but they would continuously 'pop' in and out of existence within an ecosystem as a result of genetic drift and other factors, preventing it from ever reaching equilibrium (Woodley and Sikes, 2006).
References
Chase, J. M., and Leibold, M. A. (2003). Ecological Niches: Linking Classical and Contemporary Approaches. University of Chicago Press, Chicago, Il, USA.
Elton, C. (1927). Animal Ecology. Sidgwick and Jackson, London, UK.
Grinnell, J. (1917). "The niche relationship of the California Thrasher." Auk, 34, 427-233.
Hutchinson, G. E. (1944). "Limnological studies in Connecticut. VII. A critical examination of the supposed relation between phytoplancton periodicity and chemical changes in lake waters." Ecology, 25, 3-26.
Odling-Smee, F, J., Laland, K. N., and Feldman, M. W. (2003). Niche Construction: The Neglected Process in Evolution. Princeton University Press, Princeton, NJ, USA.
Woodley, M. A., and Sikes, K. J. (2006). "Consequences of a geometric approach to adaptation." Geombinatorics, 16:2, 270-277.
