Keystone species: Ecology

Definition: a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically. Examples: Sea Otter, Beaver, Grey Wolf, Acorn Banksia Types: Predators, Mutualists, Engineers Not dominant species (dominant species is all of one species weighed together and equal the most out of all species)

Keystone Predator Example Sea Otter: Does not have to be the apex predator, orca’s prey on sea otters sea otters eat sea urchins, sea urchins eat kelp holdfasts, so sea otters protect the kelp forests from damage. The kelp provides the major backbone of the ecosystem (protection, primary food producer) so it is possibly the dominant species. If the sea otter is not present the sea urchins eat all the kelp and totally wipe out the ecosystem This is what makes the sea otter the keystone species in this case

With Sea Otter Without

Keystone Predator Example: Jaguar The jaguar, whose numbers in Central and South America have been classified as Near Threatened, acts as a keystone predator by its widely varied diet, helping to balance the mammalian jungle ecosystem with its consumption of 87 different species of prey. Any mammal that begins to thrive becomes the easy meal for the jaguar and as such its numbers decrease. This keeps species diversity high.

Keystone Mutualists Keystone mutualists are organisms that participate in mutually beneficial interactions, the loss of which would have a profound impact upon the ecosystem as a whole. Example: Banksia prionotes (Acorn Banksia) At one time of year the acorn Banksia is the sole food source for honeyeaters Honeyeaters are the primary pollination facilitators in the region Without the acorn Banksia the pollinators will die and as such the pollinating plants of the area will die out totally changing the ecosystem.

With Acorn Banksia Without

Keystone Mutualist Example: Cassowary Frugifore (fruit eater) Spreads fruit seeds all over rainforest Without it plants cannot spread out and competition increases If this is the case species diversity will dramatically decrease

Keystone Engineer Example: prairie dog. Prairie dog burrows provide the nesting areas for Mountain Plovers and Burrowing Owls. Prairie dog tunnel systems also help channel rainwater into the water table to prevent runoff and erosion, and can also serve to change the composition of the soil in a region by increasing aeration and reversing soil compaction that can be a result of cattle grazing. Prairie dogs also trim the vegetation around their colonies, perhaps to remove any cover for predators. Even grazing species such as Plains bison, pronghorn, and Mule deer have shown a proclivity for grazing on the same land used by prairie dogs. It is believed that they prefer the vegetative conditions after prairie dogs have foraged through the area.

Keystone Engineer Example: American Beaver transforms its territory from a stream to a pond or swamp affect the environment first altering the edges of riparian areas by cutting down older trees to use for their dams, allowing younger trees to take their place these dams change the riparian edges of streams and rivers into wetlands, meadows, or riverine forests. These dams have shown to be beneficial to myriad of species including amphibians, salmon, and song birds.

Summary Keystone species Doesn’t have to be apex predator but can be. Its role must irreplaceable Tends to not have any competition or very little for its niche Quite often it is not discovered to be the keystone until it is too late, but then other ecosystems can be saved.

links http://www.youtube.com/watch?v=kEh4r4iQiBU Prairie dogs http://www.youtube.com/watch?v=EUyxzAulkGk Cassowary http://www.youtube.com/watch?v=D3W4OCnHyCs Sea Urchins http://www.youtube.com/watch?v=ArhWJts2sg8 Otters vs Crocodile http://www.youtube.com/watch?v=VuMRDZbrdXc Beavers building a lodge http://www.youtube.com/watch?v=tJ800AoqpdQ Elephant knocking down tree http://www.youtube.com/watch?v=50tlF3kGbT4 Marula fruit https://www.youtube.com/watch?v=ASJ82wyHisE Sea otters vs urchins in kelp forests https://www.youtube.com/watch?v=Uc7Ahp5--eE Sea otter using rocks to open clams https://www.youtube.com/watch?v=DBNYwxDZ_pA Jaguar hunting Caimans https://www.youtube.com/watch?v=zUC4hjueTiM New Holland honeyeater https://www.youtube.com/watch?v=CzUbgYT1yIU Cassowary Doco https://www.youtube.com/watch?v=_M1lK_aMszQ Swamp loggers vs beaver dams https://www.youtube.com/watch?v=LU8DDYz68kM Battle at Kruger