11 Biology - Keystone Species

Keystone Species

A species that has a disproportionately large effect on its natural environment relative to its abundance

• Often are Apex Predators (Limit prey populations)

Examples

• Sea Otters

• Beavers (Dams)

• Sharks

• Kangaroos (Grazing on grass)

What if they are gone?

• No other organism could fill the ecological niche

• It would be a dramatically different ecosystem or it would not exist

Trophic Cascade

• Powerful indirect interactions that can control entire ecosystems

• When Predators limit the density and/or behaviour of their prey and thereby enhancing survival of the next lower trophic level

• Can be triggered by the introduction OR Withdrawal of a species

Examples

• The overfishing of cod in the Northwest Atlantic

• The decimation of kelp forests by sea urchins after the mass hunting of sea otters (who hunt the urchins)

Consequences

• CAN BE POSITIVE FOR MAINTAINING BIODIVERSITY

• Returning predators to an area can therefore help woodlands regenerate and lead to more carnon being captured in the trees and soil

• Without Marine predators (especially whales) = Increased greenhouse gases

  (Each great whale sequesters 33 tons of CO₂ on average, taking that carbon out of the atmosphere for centuries.)

Umbrella Species

A species that, through protection of its habitat, protects other species

• Have large territories and once under protection = lead to the improved survival of other species that depend on their habitat

(VS) Keystone species regulates the ecosystem (balance)

Foundation Species

• Habitat forming organisms that define many ecosystems

eg) Coral reefs, Hardwood forests, Kelp forests

(VS) Pioneer = The first organism to colonise a barren area

Indicator Species

A species that can provide information on ecological changes and give early warning signals of sensitive reactions

Eg) Lichens, Owls, Fungi

Why are these terms relevant to an ecosystem’s survival?

Umbrella Species

Grizzly bear needs a wide area, protecting its habitat also protects birds and other organisms in the area.

Biodiversity grows, it is not hit as hard with things such as disease

Indicator Species

Amphibians like frogs and toads indicates that an ecosystem is largely free of pollution

Foundation Species

Deep sea coral and sponges contribute to the creation of habitats/ecosystems that support other species (like fish)

Ecological Engineers