What term refers to the actual extent of a species' distribution when in competition with other species?

The term that refers to the actual extent of a species' distribution when it is in competition with other species is known as the realized niche. This concept captures the idea that a species may have a larger potential range of habitats and resources it could use (its fundamental niche), but that in reality, other species may limit its actual utilization of those resources due to competition, predation, or other ecological interactions.

In a complex ecosystem, species often do not occupy their entire fundamental niche due to these interactions, resulting in a realized niche that reflects the conditions under which the species can survive and reproduce in the presence of competitors and predators. The realized niche is thus a more accurate representation of how a species fits into its environment, taking into consideration the effects of biotic factors like competition.

Other terms like ecological footprint and trophic level relate to different ecological concepts, such as the impact of a species on its environment in terms of resource use, and its position in the food chain, respectively. These do not capture the specific interaction dynamics related to competition that define the realized niche.