A keystone species is a species that has a disproportionate effect on its environment relative to its abundance. Such an organism plays a role in its ecosystem that is analogous to the role of a keystone in an arch. While the keystone feels the least pressure of any of the stones in an arch, the arch still collapses without it. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measures of biomass or productivity. It has become a very popular concept in conservation biology. In biology, a species is one of the basic units of biodiversity. ... In ecology, an ecosystem is a combination of all the living and non-living elements of an area. ... In architecture, a keystone is the stone at the top of an arch. ... Isometric view of a typical arch An arch is a curved structure capable of spanning a space while supporting significant weight (e. ... An Antarctic krill, whose species comprises roughly 0. ... Conservation biology is the protection and management of biodiversity that uses principles and experiences from the biological sciences, from natural resource management, and from the social sciences, including economics. ...

Notes on the definition

The definition given here is somewhat qualitative in nature because there is not yet an accepted, rigorous definition. At issue is how to measure both abundance and impact and at what point to draw the line. Abundance in this context can be measured by biomass or productivity, among other metrics. Impact is even harder to define. It has been suggested that such keystone predators can be identified in ecosystems by their biomass dominance within ecological functional groups, even though they may be relatively rare in relation to the ecosystem as a whole. [1] In ecology, an ecosystem is a community of organisms (plant, animal and other living organisms - also referred as biocenose) together with their environment (or biotope), functioning as a unit. ... In ecology functional groups are collections of organisms based on morphological, physiological, behavioral, biochemical, or environmental responses or on trophic criteria. ...

The term is often misused in places where foundation species would be more appropriate. A keystone species is not simply one whose disappearance would alter the ecosystem. Removing any abundant species from any ecosystem will drastically alter that ecosystem by definition. What makes the concept of keystone species attractive to conservationists is that a species with a relatively tiny physical footprint can be critical to the health of its ecosystem. A foundation species is a dominant primary producer in an ecosystem both in terms of abundance and influence. ...

Examples

Without a consensus on its exact definition, we are left to illustrate the concept of keystone species with a list of examples.

A classic keystone species is a small predator that prevents a particular herbivorous species from decimating a dominant plant species. Since the prey numbers are low, the keystone predator numbers can be even lower and still be effective. Yet without the predators, the herbivorous prey would explode in numbers, wipe out the dominant plants, and dramatically alter the character of the ecosystem. The exact scenario changes in each example, but the central idea remains that through a chain of interactions, a non-abundant species has an outsized impact on ecosystem functions. This snapping turtle is trying to make a meal of a Canada goose, but the goose is too wary. ... In zoology, an herbivore is an animal that is adapted to eat primarily plants (rather than meat). ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants...

Predators

Some sea stars may perform this function by preying on sea urchins, mussels, and other shellfish that have no other natural predators. If the sea star is removed from the ecosystem, the mussel population explodes uncontrollably, driving out most other species, while the urchin population decimates coral reefs. Orders Forcipulatida Paxillosida Notomyotida Platyasterida Spinulosida Valvatida Velatida Brisingida starfish redirects here. ... Subclasses Euechinoidea Superorder Atelostomata Order Cassiduloida Order Spatangoida (heart urchins) Superorder Diadematacea Order Diadematoida Order Echinothurioida Order Pedinoida Superorder Echinacea Order Arbacioida Order Echinoida Order Phymosomatoida Order Salenioida Order Temnopleuroida Superorder Gnathostomata Order Clypeasteroida (sand dollars) Order Holectypoida Perischoechinoidea Order Cidaroida (pencil urchins) Group of black, long-spined Caribbean sea... Subclasses Heterodonta Palaeoheterodonta A mussel is a bivalve mollusk that can be found in lakes, rivers, creeks, intertidal areas, and throughout the ocean. ... Cooked mussels Shellfish is a term used to describe shelled molluscs and crustaceans used as food. ...

Similarly, sea otters in kelp forests keep sea urchins in check. Kelp roots are merely anchors, and not the vast nutrient gathering networks of land plants. Thus the urchins only need to eat the roots of the kelp, a tiny fraction of the plant's biomass, to remove it from the ecosystem. Binomial name Enhydra lutris (Linnaeus, 1758) The Sea Otter (Enhydra lutris) is a large otter native to the North Pacific, from northern Japan and Kamchatka west across the Aleutian Islands south to California. ... Kelp Forest Kelp forests are a type of marine ecosystem established around colonies of kelp; they contain rich biodiversity. ...

Domestic cats have taken the role of a keystone species in many environments, including human habitations, where they control some rodent populations. Feral cats are known to decimate native populations in many places in which they are introduced. Trinomial name Felis silvestris catus (Linnaeus, 1758) The cat (or domestic cat, house cat) is a small carnivorous mammal of the subspecies Felis silvestris catus. ...

These creatures need not be apex predators. Sea stars are prey for sharks, rays, and sea anemones. Cats and sea otters and are prey for raptor birds. Apex predators (also alpha predators or superpredators) are predators that are not preyed upon in the wild. ...

Engineers

In North America, the grizzly bear is a keystone species, but not as a predator; they serve as ecosystem engineers. They transfer nutrients from the oceanic ecosystem to the forest ecosystem. The first stage of the transfer is performed by salmon who swim up rivers, sometimes for hundreds of miles. The bears then capture the salmon and carry them onto dry land, dispersing nutrient-rich feces and partially-eaten carcasses. World map showing North America A satellite composite image of North America. ... Trinomial name Ursus arctos horribilis (Ord, 1815) Current and historical range of the Grizzly Bear in North America The Grizzly Bear, sometimes called the Silvertip Bear, has traditionally been treated as a subspecies, Ursus arctos horribilis, of the brown bear living in North America. ... An ecosystem engineer is any organism that modifies its own ecosystem. ... The worlds oceans as seen from the South Pacific Ocean Oceans (from Okeanos in Greek, the ancient Greeks noticing the strong current that flowed off Gibraltar and assuming it was a great river) cover almost three quarters (71%) of the surface of the Earth, and nearly half of the... Eucalyptus Forest at Swifts Creek in East Gippsland, Victoria, Australia. ... Illustration of a male Coho Salmon The Chinook or King Salmon is the largest salmon in North America and can grow to 1. ... Feces, faeces, or fæces (see spelling differences) is waste product from an animals digestive tract expelled through the anus (or cloaca) during defecation. ...

Another ecosystem engineering keystone species is the beaver, which transforms its territory from a stream to a pond or swamp. Species C. canadensis C. fiber Beavers are semi-aquatic rodents native to North America and Europe. ...

Others

Other examples of keystone species are: Homo (genus), the Black-tailed Prairie Dog, and elephants in grasslands. Species Homo sapiens sapiens See text for extinct species. ... Binomial name Cynomys ludovicianus (Ord, 1815) The Black-tailed Prairie Dog (Cynomys ludovicianus), is found in the Great Plains of North America from about the USA-Canada border to the USA-Mexico border. ... Genera and Species Loxodonta Loxodonta cyclotis Loxodonta africana Elephas Elephas maximus Proboscidea is an order including only one extant family, Elephantidae or the elephants, with three species: the Savannah Elephant and Forest Elephant (which were collectively known as the African Elephant), and the Asian Elephant (formerly known as the Indian... An Inner Mongolia Grassland. ...

See also

• Foundation species
• Indicator species
• Flagship species

A foundation species is a dominant primary producer in an ecosystem both in terms of abundance and influence. ... Indicator species are unique environmental indicators as they offer a signal of the biological condition in a watershed or ecosystem, and are a warning system that pollution has entered the food web. ... A flagship species is a species chosen to represent an environmental cause, such as an ecosystem in need of conservation. ...

External links

• A summary of Paine's original hypothesis from the University of Washington's Pathbreaker series

• Intraspecific Diversity of Lupins