Which type of species has a significant impact on an ecosystem relative to its abundance?

A keystone species is defined by its significant role in maintaining the structure of an ecological community, even if it is not the most abundant species within that ecosystem. The importance of a keystone species lies in its unique interactions with other species, which can include predation, competition, or habitat modification. These interactions often affect population sizes and the diversity of the ecosystem as a whole.

For instance, a predator that controls the population of herbivores can prevent overgrazing of vegetation, thereby maintaining plant diversity and supporting a variety of other species. The loss or removal of a keystone species can lead to dramatic shifts in the ecosystem, potentially resulting in ecological collapse or a significant change in community structure.

While invasive species can also have considerable impacts, they tend to alter ecosystems negatively, whereas keystone species are integral to the health and balance of their ecosystem. Flagship species are those that are used to symbolize conservation efforts and inspire public support, and endemic species are those that are unique to a specific geographical area. However, their roles do not inherently involve the critical ecological functions characterized by keystone species.