keystone species

American  

[kee-stohn spee-sheez, spee-seez] / ˈkiˌstoʊn ˈspi ʃiz, ˈspi siz /

noun

plural

keystone species

1. Ecology. a species, especially a plant or animal, that is critical to the health of the ecosystem it is part of.

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keystone species Scientific  

/ kē′stōn′ /

1. A species whose presence and role within an ecosystem has a disproportionate effect on other organisms within the system. A keystone species is often a dominant predator whose removal allows a prey population to explode and often decreases overall diversity. Other kinds of keystone species are those, such as coral or beavers, that significantly alter the habitat around them and thus affect large numbers of other organisms.

2. Compare indicator species

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Example Sentences

They "play a central role in the food web, consuming fish and invertebrates and recycling nutrients" and are one of the "keystone species" of their ecosystem.

From Barron's • Oct. 10, 2025

Sunflower sea stars are considered a keystone species, meaning they are critical in regulating the stability and diversity of their ecosystems.

From Los Angeles Times • Aug. 4, 2025

Considered "keystone species" by many, crayfish play an outsized role as food sources for other animals and as ecosystem engineers, creating burrows that act as habitat for many species in semi-terrestrial environments.

From Science Daily • Nov. 25, 2024

The beaver is a keystone species that can bring huge benefits to nature but governments are stalling on plans to reintroduce them into the wild, the Wildlife Trusts say.

From BBC • Aug. 28, 2024

Until Columbus, Indians were a keystone species in most of the hemisphere.

From "1491" by Charles C. Mann