Keystone species are usually categorized into a few key types based on their ecological roles. The most commonly recognized keystone organisms include:
- Predators: These species, such as sea otters and wolves, help maintain the structure of an ecosystem by controlling the population of prey species. Without these predators, prey populations can increase dramatically, leading to an imbalance in the ecosystem.
- Herbivores: Species like elephants and grazing animals often play essential roles in shaping plant communities, which in turn affects various other organisms. Their feeding habits can promote biodiversity by preventing any single plant species from dominating.
- Plants: Certain plants, especially those that provide critical resources or habitat, can be keystone species. An example is the American beaver, whose dam-building creates wetland habitats that support a wide range of plant and animal species.
- Decomposers: Organisms like fungi and certain bacteria may also be considered keystone species, as they break down organic matter, recycling nutrients back into the ecosystem and supporting plant growth.
These organisms are essential because their presence and activities directly influence the structure and diversity of their ecosystems. Removing a keystone species often leads to drastic changes and can make entire ecosystems less stable.