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.

---

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

---

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

Some scientists trying to recover sunflower sea stars see the finding as a strong guide for future research — and efforts to boost the decimated keystone species.

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

Beavers are a keystone species on which many other species rely.

From BBC • May 28, 2024

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

From "1491" by Charles C. Mann