Ecology Exam 4: Keystone Species

Keystone species in depth

-A species whose very presence contributes to the diversity/stability of a community -A species whose extinction would consequently lead to the extinction of other forms of life -Help to support the ecosystem (entire community of life) of which they are a part -If species goes extinct it might be a domino effect, species are ones that might require protection and need to be around, whatever it is they are doing is helping the community, if they stopped everything would fall apart

If Keystone Species are gone, then what?

-Other mechanisms (species) take over -Another species becoming dominant -Community shift -Decline in species -Extinction?? -Ecological Unbalance -What else? -Role they play is critical, if this is disrupted can cause the ecology of the systems to fail

experimental outcome

-Pisaster Sp richness at end = 15 -Removed Pisaster Sp richness at end of yr. 1 = 8

Experimental set up

-Pisaster Sp richness at start = 15 -Removed Pisaster Sp richness at start = 15

Prairie Dogs

-Their burrows act as homes to other creatures (inquilism) 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. -Habitat modifiers, example of inquilism (building something in which other organisms can use), moving soil around helps to preserve much of the prairie plant life

Prairie dogs contd

-Their foraging and feeding practices enable a more nutritious, diverse and nitrogen-rich mixture of grasses and forbs (broad-leafed vegetation) to grow. -The enriched vegetation attracts an amazing array of wildlife who graze in their colonies -Introduce prairie dogs to certain areas might rebuild the grass habitat

Paine's sea star study

-Working with starfish along Washington coast -Paine proposed that the feeding activities of a few species have inordinate influences on community structure. -Paine R.T. 1966. Food web complexity and species diversity. American Naturalist 100:65-75.

keystone species may be

-habitat modifiers (prairie dog) -predators (coyote) -herbivores (beaver)

Paine's sea star study conclusion

-in the inter tidal, sea stars are a keystone species, i.e., a species that has an effect on the rest of the community that is stronger than its numbers alone would predict. -Acting as a predator to the mussels keeps the other species around

Prairie Dogs/BF-Ferret

Black-footed ferret, 90% of whose diet is prairie dogs, is on the brink of extinction and is designated as endangered under the Endangered Species Act. -Try to preserve areas that have prairie dogs and to introduce them to new areas to keep up the ferret species

Why did sea stars have this effect on diversity?

Feeding trials showed that mussels were sea stars' preferred prey.

How KS fit in with Food Webs?

Herring or salmon is keystone, could present problems, unless something replaces it, that linkage of energy may be lost in the food web

Wolves in yellowstone

if you take out the top predators, the ecosystem falls -keystone species

Paine's hypothesis

predation by sea stars reduces competition, allows coexistence. (exploiter mediated coexistence?)

Example of keystone species

salmon More than 137 species of fish and wildlife - from orcas to caddisflies - depend on the Northwest salmon for their survival

Paine's sea star study outcome

Species richness continued to decrease over time where sea stars were absent, until these sites were dominated by 1 sp., mussels. -Mussels grew faster than other sp., could overgrow other sp., thus they were competitively dominant.

Prairie Dogs/Plover

The mountain plover, which breeds on prairie dog towns, has declined by 63% since 1966, in part due to prairie dog declines.

keystone species

a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically. -functional role in the niche is critical