What are keystone species and their impact on communities?

Keystone species are organisms that have a disproportionately large effect on their environment relative to their abundance.

Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. They can be any type of organism, including plants, animals, or bacteria. The concept of the keystone species was first introduced by Robert T. Paine in 1969, who studied the impact of the starfish, a predator, on its marine ecosystem.

The impact of keystone species on their communities is significant. For instance, they can control the population of other species, which in turn affects the availability of resources and the overall biodiversity of the community. If a keystone species is removed or declines, the nature of the ecosystem will change dramatically. This can lead to a domino effect, causing declines in other species and potentially leading to ecosystem collapse.

For example, sea otters are considered a keystone species in the Pacific Northwest. They feed on sea urchins, controlling their population. Without sea otters, the sea urchin population would explode, leading to overgrazing of kelp forests. This would drastically reduce the habitat for other species and decrease biodiversity.

Similarly, some plants can be keystone species. The saguaro cactus in the Sonoran Desert provides food and shelter for a variety of animals. If the saguaro were to disappear, many of those species would be without resources.

In conclusion, keystone species are vital for the health and balance of their ecosystems. Their presence or absence can dramatically alter the community structure and biodiversity, demonstrating the interconnectedness of all species within an ecosystem.