A niche can be defined simply as the area in which an organism inhabits. However, more specifically, it is an area occupied by a species within an ecological community which shapes and is shaped by, its surrounding environment. Food, shelter, predation, temperature, reproduction, and behaviour are all factors which contribute to the construction of a niche.
Additionally, there are two types of niche, the realised and the fundamental. A fundamental niche is the range of environmental conditions in which a species can survive in, whereas a realised niche is the range of environmental conditions in which a species is found in reality. Factors such as the principle of competitive exclusion, wherein two species utilising the same resource are not likely to remain evenly balanced in number, can lead to this niche compression.
Niches are also hotspots for intra and inter-specific competition, due to ecologically similar species having similar fundamental niches. An example of this can be seen in Figure 1 between the barnacle species Chthamalus and Semibalanus, which shows Chthamalus being outcompeted by Semibalanus for space and thus relegating Chthamalus to the less hospitable upper shore where Semibalanys cannot survive (see Competition article for more information).
Figure 1 – Fundamental and Realised Niches and Chthamalus and Seminbalanus
“Fundamental vs Realised Niche – Rocky Shore Data”, 2018, Graphic, BioNinja. Source: http://ib.bioninja.com.au/options/option-c-ecology-and-conser/c1-species-and-communities/ecological-niche.html
Community – A group of species in association occupying the same area over the same period of time.
Fundamental Niche – The theoretical space a species could inhabit if it wasn’t limited by competition with other species.
Inter-specific competition – Competition between different species.
Intra-specific competition – Competition within a species.
Niche Compression – The process of the area where a species could survive in theory, reducing to where a species can actually survive due to competition.
Organism – An individual animal, plant, or single-celled life form.
Principle of Competitive Exclusion – Only one species can exist when two species require approximately the same resources in the same place.
Realised Niche – The actual space a species inhabits and the resources it uses as a result of competition with other species