A keystone species is a species that has a disproportionate effect on its environment relative to its abundance^[1]. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and Such species affect many other organisms in an ecosystem and help to determine the types and numbers of various others species in a community.

Such an organism plays a role in its ecosystem that is analogous to the role of a keystone in an arch. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( A keystone is the architectural piece at the crown of a vault or Arch and marks its apex, locking the other pieces into position An arch is a structure that spans a space while supporting weight (e 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. Biomass, in Ecology, is the mass of living biological organisms in a given area or Ecosystem at a given time It has become a very popular concept in conservation biology. "Conservation Biology" redirects here For the Scientific journal, see Conservation Biology (journal. ^[2]

Contents 1 Definition 2 Examples 2.1 Predators 2.2 Engineers 3 References 4 See also 5 External links

Definition

The definition given here is somewhat qualitative in nature because there is not yet an accepted, rigorous definition. ^[3] An 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. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions ^[4]

The term is often misused in places where foundation species would be more appropriate. A foundation species is a dominant Primary producer in an ecosystem both in terms of abundance and influence 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. ^[3]

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 eliminating dominant plant species. Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell Plants are living Organisms belonging to the kingdom Plantae. 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. One example is the weevil and its suggested keystone effects on aquatic plant species diversity by prey activities on nuisance Euransian Watermilfoil. ^[5]

Predators

Some starfish may perform this function by preying on sea urchins, mussels, and other shellfish that have no other natural predators. Starfish (also called sea stars) are any Echinoderms belonging to the class Asteroidea. Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea. The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats Shellfish is a Culinary and Fisheries term for those aquatic Invertebrate animals that are used as Food: various species of molluscs If the sea star is removed from the ecosystem, the mussel population explodes uncontrollably, driving out most other species, while the urchin population annihilates coral reefs. In his classic 1966 paper, Dr. Robert Paine described such a system in Mukkaw Bay in Washington State. ^[6] This led to his 1969 paper where he proposed the keystone species concept. ^[7]

Similarly, sea otters in kelp forests keep sea urchins in check. The sea otter ( Enhydra lutris) is a Marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Kelp forests are underwater areas with a high density of Kelp. 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. ^{[8] [9]}

These creatures need not be apex predators. Sea stars are prey for sharks, rays, and sea anemones. Sea otters are prey for orca. The Orca or Killer Whale ( Orcinus orca) less commonly Blackfish or Seawolf, is the largest species of the Oceanic dolphin family ^[10]

Engineers

In North America, the grizzly bear is a keystone species - not as a predator but as ecosystem engineers. The Grizzly Bear (Ursus arctos horribilis, also known as the Silvertip Bear, is a Subspecies of Brown bear (Ursus arctos that lives An ecosystem engineer is any Organism that creates or modifies habitats. They transfer nutrients from the oceanic ecosystem to the forest ecosystem. An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. A forest is an area with a high density of Trees There are many definitions of a forest based on various criteria The first stage of the transfer is performed by salmon, rich in nitrogen and potassium, who swim up rivers, sometimes for hundreds of miles. Salmon is the common name for several species of Fish of the family Salmonidae. The bears then capture the salmon and carry them onto dry land, dispersing nutrient-rich feces and partially-eaten carcasses. Feces, faeces, or fæces (see spelling differences) is a waste product from an animal's digestive tract expelled through the Anus It has been estimated that the bears leave up to half of the salmon they harvest on the forest floor.

Another ecosystem engineering keystone species is the beaver, which transforms its territory from a stream to a pond or swamp. Beavers are two primarily nocturnal semi-aquatic species of Rodent, one native to North America and one to Europe ^[11]

In the African savanna, the larger herbivores, especially the elephants, shape their environment. A savanna or savannah is a Tropical or Subtropical Grassland or Woodland Ecosystem. Elephants ( family: Elephantidae) are large land Mammals of the order Proboscidea. The elephants destroy trees, making room for the grass species. Without these animals, much of the savanna would turn into woodland. Ecologically a woodland is an area covered in trees differentiated from a Forest. ^[12]

References

See also

• Foundation species
• Indicator species
• Flagship species
• Indigenous
• Introduced species

External links

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

A foundation species is a dominant Primary producer in an ecosystem both in terms of abundance and influence An indicator species is any Biological species that defines a trait or Characteristic of the environment A flagship species is a Species chosen to represent an environmental cause such as an Ecosystem in need of conservation. In Ecology, an indigenous Species is an Organism which is native to a given region or Ecosystem. An introduced species (also known as naturalized species or exotic species) is an Organism that is not indigenous to a given location but

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic