Download keystone species - Wando High School

KEYSTONE SPECIES
• KEYSTONE - the
central stone of an
arch or vault.
• It is the most
important stone in an
arch bridge, without
this stone the arch
would collapse.
DEFINED
• A keystone species
is one whose
impact on its
community or
ecosystem are
larger and greater
than would be
expected from its
relative abundance
or total biomass.
• The term “keystone” was coined by Robert
Pain and was based on his studies of
rocky shore communities in California.
• When he removed a top predator (starfish)
from a section of the shore, aggressive
mussels multiplied reducing the original 15
species assemblage to 8.
EFFECTS OF KS SPECIES
1. Control potential dominants (sea otters
control urchins that feed on kelp forests)
2. Provide critical resources (certain fruit
trees that provide a resource to a range
of organisms at a time of scarcity)
3. Act as mutualists (fig wasps pollinate fig
trees which provide a vital resource to
frugivores who disperse seeds)
4. Modify the environment (beavers
building dams)
KEYSTONE SPECIES
1.
2.
3.
4.
5.
6.
7.
8.
starfish
sea otter
gopher tortoise
American alligator
African elephant
salmon
beaver
prairie dog
NOT KEYSTONE SPECIES
•
•
•
•
trees
giant kelp
prairie grasses
reef-building corals
Not KS species because their impact on
the ecosystem is proportional to their
biomass.
IMPORTANCE OF KEYSTONES
“Its importance," says Paine, "is that it
convinced managers and conservationists
alike that the ecological impact of single
species matters. That is, in order to
manage, understand, and restore
ecological assemblages, the roles of
individual species have to be understood
and considered."
Starfish
• Keeps predatory mussel populations in
check
Sea Otter
• Keeps urchins from consuming the kelp
forest
Gopher Tortoise
• Tortoise burrows provide shelter for more
than 360 species of mammals, birds,
reptiles and amphibians
• Species which utilize the burrows include
skunks, opossums, rabbits, armadillos,
Florida mice, burrowing owls, quail, indigo
snakes, gopher frogs, snakes, lizards,
frogs, toads, and over 300 invertebrates
• These species are commensalistic and
use the burrows to escape fire, weather,
predators, etc.
• Some species are dependent on the
burrows
American Alligator
• Alligators dig holes which provide habitat
for many other species
African Elephant
• Scarafication
• Many plant species are dependent on
passing through an elephant’s digestive
tract before they can germinate. It is
calculated that at least a third of tree
species in west African forests rely on
elephants in this way.
Elephant Extras
• They modify their habitat by converting Savannah and
woodlands to grasslands
• Elephants can provide water for other species by digging
water holes in dry riverbeds
– the depressions created by their footprints and their bodies trap
rainfall
• Elephants act as seed dispersers by their fecal matter. It
is often carried below ground by dung beetles and
termites causing the soil to become more aerated and
further distributing the nutrients
• Their paths act as firebreaks and rain water conduits
• An Elephants journey through the high grass provides
food for birds by disturbing small reptiles, amphibians or
insects.
Salmon
• 137 species have been documented to
depend on salmon
• 41 are mammals including killer whales,
bears and river otters
• 89 are birds, including bald eagles,
Caspian terns and grebes
• five are reptiles and two are amphibians.
Salmon Con’t
• Several species depend on salmon both
directly and indirectly—feeding on salmon
as well as preying on species that eat
salmon
• Many insects feed on salmon, and then
become food for juvenile salmon
• No less than 82 species feed directly on
salmon carcasses
Beaver
• Beaver dams serve to create wetlands and
ponds.
• The benefits to humans include: flood
control, removal of pollutants, drought
protection and decreased erosion
• American Indians called the beaver the
“sacred center” of the land b/c this species
creates rich habitats for other mammals,
fish, turtles, frogs, birds, and ducks
Prairie Dog
• Black-tailed prairie dogs play an integral role in
the prairie food chain
• They are a critical food source for such animals
as the endangered black-footed ferret, swift fox,
coyotes, hawks, eagles and badgers
• 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