Keystone Species


What are the characteristics of a keystone species?

    A keystone species is a non-abundant species that can, through a series of chain reactions, have a damaging impact on various ecosystem functions. This species generally has a relatively tiny physical impression but is vital to the health of its ecosystem. 
    The extinction of a keystone species would ultimately lead to the extinction of numerous other species. A keystone species sustains the ecosystem that it is a part of. Their presence decides the types and numbers of species within an environment.
    If a keystone species were to be removed, an ecosystem would experience a massive change. The diversity and character of the environment would be dramatically altered.
   

There are two types of keystone species: predators and engineers.

Predators prey on different species, keeping their populations in check. Their prey generally has no other natural predators.
Engineers alter their environments. Their actions physically change the ecosystem.

Predators

Starfish- Starfish prey on sea urchins, mussels and other shelfish that have no other natural preditors. If the starfish were to be removed, the mussel population would increase at an alarming rate, driving out other species, and the urchin population would increase, reulting in the destruction of coral reefs.

Sea otters- Sea otters that live in kelp forests keep sea urchin populations in check. Without the sea otter, urchin populations would explode, destroy coral reefs, and negatively alter the environment.



photo by: doozywhoop  



Engineers

Grizzly Bear- The grizzly bear is considered to be an ecosystemtem engineer because of the fact that they transfer nutrients from the oceanic ecosystem to the forest ecosystem. This process occurs when bears hunt for salmon. When a salmon is caught, the bear carries it to dry land, where the partially eaten carcass is left (which is rich in both nitrogen and potassium) and nutrient rich feces is expelled.

Elephants- Elephants help to shape the environment in which they live. They destroy trees, which allows room for various grass species. Without elephants, a sizable portion of the Savanna would be transformed into woodland.

photo by: anne makaske

Documentation of Sources

1) Wikimedia Foundation
http://en.wikipedia.org/wiki/Keystone_species

2) Prairie Dogs.org
http://www.prairiedogs.org/keystone.html