The term niche is used in ecology with a variety of distinct meanings. It may refer to a spatial unit or to a function unit. One definition focuses on niche as a role claimed exclusively by a species through competition. The word is also used to refer to "utilization distribution" or the frequency with which populations use resources. Still, niche is well enough established in ecology that Stephen Jay Gould can label it as "the fundamental concept" in the discipline, "an expression of the location and function of a species in a habitat." Niche is used to address such questions as what determines the species diversity of a biological community, how similar organisms coexist in an area, how species divide up the resources of an environment, and how species within a community affect each other over time.

Niche has not been applied very satisfactorily in the ecological study...