keystone and foundation species
DESCRIPTION
Describes labels given to species of critical importance in an ecosystem.TRANSCRIPT
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Keystone or Foundation Species?
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Keystone or Foundation?
• Keystone • Pisaster ochraceus is an
efficient predator of the common mussel, Mytilus californicus.
• It reduces abundance of M. californicus, allowing other macroinvertebrates to persist.
• If Pisaster present = diverse intertidal community.
Based on the research of Dr. Robert T. Paine
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(a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates.
With Pisaster (control)
Without Pisaster (experimental) N
umbe
r of s
peci
es
pres
ent
0
5
10
15
20
1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73
(b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.
Dr. Robert T. Paine’s Work
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Keystone or Foundation?
• Keystone • Removing three species of
kangaroo rats changed a desert plain into an arid grassland. In areas without kangaroo rats, grasses filled in between the shrubs, stems and other plant litter accumulated, large-seeded plants replaced those with smaller seeds, snow melted more slowly and the numbers of the other rodents increased significantly.
Based on the research of Dr. James H. Brown
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Keystone or Foundation? • Keystone • Their burrows act as homes to
other creatures, including burrowing owls, badgers, rabbits, black-footed ferrets, snakes, salamanders, and insects.
• Their burrowing activity works to loosen and churn up the soil, increasing its ability to sustain plant life.
• Their foraging and feeding practices enable a more nutritious, diverse and nitrogen-rich mixture of grasses and forbs (broad-leafed vegetation) to grow.
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Keystone or Foundation?
• Foundation • Dominant primary producer
that provides food and shelter for many other species
*Note: Some authors, including Miller, equate this with “engineer” type keystone species
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Effects of losing the “keystone” predator…
• A trophic cascade- in a food web, the
cascading effect that a change in the size of one population (usually an apex predator) in the web has on the populations below it
Example: Gray Wolf in Yellowstone National Park (Wolf -> Elk -> Cottonwood/Aspen/Willow -> Bird Populations)
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Don’t forget…
• A keystone species is one that has a disproportionate impact on its ecosystem when compared to its abundance.
• A foundation species is usually a primary producer that dominates an ecosystem in abundance and influence.
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Sources
• http://www.washington.edu/research/pathbreakers/1969g.html (starfish)
• http://query.nytimes.com/gst/fullpage.html?res=9C0CE1DB1530F936A15751C1A966958260 (kangaroo rats)
• http://www.prairiedogs.org/keystone.html (praire dogs)
• http://www.eoearth.org/article/Global_marine_biodiversity_trends (kelp)