keystone species

American  

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

noun

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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Other Word Forms

Inflected Forms

noun

• keystone species
  plural

Example Sentences

Sea otters are a keystone species in kelp forest ecosystems, eating sea urchins that would otherwise consume the kelp, according to the aquarium.

From Los Angeles Times • Apr. 29, 2026

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

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

"We have been able to pinpoint the origin of baobabs, which are an iconic keystone species supporting a wide diversity of animals and plants as well as humans," she told the BBC.

From BBC • May 15, 2024

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

From "1491" by Charles C. Mann