Communities & Ecosystem Sites
Henderson's Dictionary of Biological Terms, by Eleanor Lawrence. 10th Ed.
An organisms niche describes its function, or job within a community. Part of a niche is how a species obtains food, whether they are generalist, or specifically look for a certain type of prey. Each species has a fundamental niche, a full range of environmental conditions in which it can live. But in a community, competition for resources (e.g. food and homes) can restrict how much of its fundamental niche that it can work in. When a species' niche impede upon another species niche, both species may find itself in a smaller niche, its realized niche. An example of this comes from the work by Joseph Connell. Connell, studying intertidal communities, found that two species of barnacles along the coast of Scotland changed its niche, depending upon if the species were in the same area together, or they were separated in an area. Connell found that Balanus kept the barnacle Chthamalus from spreading throughout its fundamental niche, restricting it to a higher band in the intertidal. When Connell removed Balanus from the intertidal below Chthamalus, Chthamalus expanded its niche into deeper water. When Connell reintroduced Balanus back into the area, Chthamalus slowly retreated its lower boundary higher in the intertidal as Balanus repopulated the area. In the lower part of Chthamalus fundamental niche, it could not compete with Balanus.