Practice question

Niche overlap means that two species share some portion of resource use or environmental requirements. Greater overlap can increase the potential for competition when the shared resource is limiting, but overlap may be partial rather than identical. Identical resource use represents the extreme of complete overlap, not the general meaning of the term. Species can overlap on one axis, such as food type, while differing on another, such as feeding time or microhabitat. Conversely, measured overlap does not prove competition if resources are abundant. Completely separate niches imply zero overlap, and abiotic interactions do not describe resource sharing between species. None of the listed choices states “shared or partly shared resource use,” so the keyed wording is scientifically too strong even though it is the nearest available choice. Quantitative indices such as Pianka’s measure overlap on a continuum from none to complete identity. Interpreting those indices requires information on resource availability and fitness effects. The accepted principle is therefore common use of at least part of niche space, with competition contingent on limitation and the absence of sufficient partitioning.