Three possible long-term consequences of two species occupying the same niche are:
- Competitive Exclusion: One species may outcompete the other, leading to the exclusion of the less competitive species from that niche or habitat area. This means the less competitive species may be pushed out or restricted to a smaller range or resource base.
- Local Extinction: If one species is outcompeted highly effectively by the other across the entire local habitat, it could become extinct in that area. This is an extreme outcome of strong competition within the same niche.
- Niche Differentiation: Instead of competitive exclusion or extinction, the species may evolve to specialize on different subsets of resources within their shared fundamental niche. This can result in subdividing the niche and reducing direct competition, allowing both species to coexist long-term by occupying distinct realized niches.
Additional ecological models also suggest coexistence may be possible in some cases through trade-offs or equalizing mechanisms, but the main long-term outcomes focus on exclusion, extinction, or niche differentiation.
Thus, the three major long-term consequences are competitive exclusion, local extinction, or niche differentiation allowing coexistence. Each outcome depends on the nature and intensity of competition and environmental factors.