Wolves serve as a keystone species in every ecosystem.
Wolves serve as a keystone species in Yellowstone.
Elk serve as a keystone species in Yellowstone.
Elk serve as a keystone species in every ecosystem.
While it is true that wolves serve as a keystone species in many ecosystems, it is not accurate to say that they serve as keystone species in every ecosystem. The role of a keystone species is to have a disproportionately large impact on the structure and functioning of an ecosystem relative to its abundance. This means that the specific keystone species can vary depending on the ecosystem. In the case of Yellowstone National Park, wolves are indeed considered a keystone species as they help regulate the population of elk and other prey species, which in turn affects vegetation and other aspects of the ecosystem.
In contrast, it is not accurate to say that elk serve as a keystone species in every ecosystem. While elk can be a keystone species in Yellowstone, this does not necessarily hold true for all ecosystems. The concept of a keystone species is not universal and can vary depending on the specific ecological dynamics of each ecosystem.