What are the main types of keystone species and their roles in ecosystems?

Keystone species are those that have a disproportionately large impact on the structure and function of their ecosystem relative to their abundance. They play critical roles in maintaining the balance and diversity of ecosystems, and their loss can have far-reaching consequences.

There are two main types of keystone species:

• Predator keystone species: These are species that have a strong control on the abundance of their prey, which in turn affects the entire food web of the ecosystem. For example, sea otters in kelp forest ecosystems control the population of sea urchins, which would otherwise overgraze the kelp and destroy the habitat for many other species.
• Engineer keystone species: These species modify the physical environment of the ecosystem in ways that create and maintain habitats for other species. For example, beavers create wetland habitats that support a variety of other species, and elephants create and maintain open grasslands that benefit both grazers and browsers.

Other types of keystone species include mutualist keystone species, which play a critical role in maintaining the relationships between different species in an ecosystem, and foundation species, which are the dominant species in an ecosystem and provide the foundation for many other species.