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The Niche: What is a NICHE?
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fundamental niche
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realized niche
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Generalists
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Specialists
Bug-Eyed Baby Aye-Aye
April 20, 2005—Kintana is the United Kingdom's first
captive-bred aye-aye lemur.
Kintana brandishes outlandish adaptations for survival
in lemurs' only native home, the African island of
Madagascar. In the forest the aye-aye's batlike ears can
detect insect larvae squirming inside trees. A barkbreaking bite from tough incisors and a subsequent
probe with a long, bony second digit seals the meal.
That adaptation is more curse than blessing for some of these tree dwellers, which are
beaten by Madagascan villagers who see the crooked claw as a harbinger of death.
Farmers too get their licks, persecuting the world's largest nocturnal primates for their night
raids on sweet crops like coconuts and sugarcane. Also, some Madagascans hunt the 4.5pound (2-kilogram) aye-ayes for their meat.
But the aye-aye's greatest threat is deforestation, which is largely responsible for its listing
as endangered on the World Conservation Union's Red List of Threatened Species—and
which may one day make captive births crucial to the species's survival.
http://news.nationalgeographic.com/news/2005/04/0419_050419_ayeaye.html
Generalists
Specialists
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Community Interactions
Competition:
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Interspecific competition
Balanus behaviorally excludes Chthamalus from the region where both can survive
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Intraspecific competition
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Interference competition
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Exploitation competition
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Resource partitioning
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Competitive exclusion principle:
"complete competitors cannot coexist."
For example, competition between Paramecium for bacteria in lab cultures, as first studied by
Gause (density dependence, intra-specific competition):
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If two species create an active demand on the same limited resource, then interspecific
competition occurs:
In this example, P. aurelia outcompetes P. caudatum, which dies off.
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In another experiment, in contrast:
In this case, competitive coexistence is the outcome. Why the difference?
P. bursaria feeds on bacteria that adhere to the glass the culture flask whereas P. aurelia feeds
on suspended bacteria.
Thus the species compete, but differ sufficiently in the resources used that they coexist
indefinitely.
The greater the ecological difference between two species, the more likely they are to coexist.
Predation
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Predator
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Prey
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Adaptations for each
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Wolves feeding on Elk
Symbiosis:
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Mutualism
Example: Flatworm & Algae
http://www.rzuser.uniheidelberg.de/~bu6/Convoluta.html
Clown fish and Sea Anemone
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Commensalism
Example: Remora & Ray http://www.oceanlight.com/lightbox.php
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Parasitism
Loa Loa: Eye Worm
Hookworm
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Ecological Succession
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Primary Succession
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Pioneer Species
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Secondary Succession
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Role of Disturbance
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Other Roles of Species in Ecosystems
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Native/Endemic Species
Immigrant / Alien / Exotic / Invasive Species
Example: KUDZU http://www.lib.niu.edu/ipo/oi000208.html
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Indicator Species
Something in water likely causes
deformed frogs
October 1, 1997
Web posted at: 3:31 p.m. EDT (1931 GMT)
ST. PAUL, Minnesota (AP) -- Tainted water probably is to blame for the
deformities of frogs that were born with extra or misshapen limbs, missing or
shrunken eyes and small sex organs..
Reports of deformed frogs have come from throughout Minnesota, two dozen
other states and Canada over the past two years, and researchers say water is almost certainly the cause.
Researchers took water from three northern Minnesota wetlands where deformed frogs had been seen, mixed that
water with tap water in varying ratios, and used the mixtures to grow frog eggs. Plain tap water was also tested, as
was 100 percent wetlands water.
QUESTIONS:
1. What are the Independent / Dependent Variables in this experiment?
2. What is the control?
3. What are the Levels of Treatment?
When the researchers used mixtures with more than 50 percent wetlands water, most of the African clawed frog
embryos showed a wide range of abnormalities.
Copyright 1997 The Associated Press. All rights reserved. This material may not be published, broadcast,
rewritten, or redistributed.
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Keystone Species:
Wolves Reshape Yellowstone National Park: An Example of
Systems Thinking
In the late 1990s scientists began to notice changes in
Yellowstone National Park, in Wyoming. Trees that had stopped
growing decades ago began to grow again. Animals started
behaving differently. What caused these mysterious changes?
Scientists believe they found the answer—wolves.
Wolves used to live in Yellowstone, which is in the northern U.S.
Rocky Mountains. But many people thought wolves were pests
that killed livestock and harmed crops. In 1926 the last wolf in
Yellowstone was shot and killed. For the next 70 years
Yellowstone did not have any wolves. Scientists decided to bring
them back to the area in 1995. The U.S. Fish and Wildlife Service
brought in 15 gray wolves from Canada.
"Wolves were reintroduced because historically wolves lived in
Yellowstone," explained William Ripple, a forest ecologist at
Oregon State University. Ripple studies wolves' effects on
Yellowstone. "Now with the reintroduction of wolves,
Yellowstone has all of the top predators it has had for thousands
of years." Today between 250 and 300 wolves live in
Yellowstone—and they have already left their mark.
For example, wolves have been hunting and eating elk, a member of the deer family. The elk leftovers
provide food for animals such as ravens, eagles, and bears. Wolves also scare elk from streams. With
fewer elk near the water, plants that grow there, such as willows, can grow taller.
"Benefits of this new plant growth include more habitat for birds and more plant food for beaver,"
Ripple explained. "The number of beaver in northern Yellowstone has increased dramatically since
wolves were reintroduced."
Wolves have such a big effect on Yellowstone because scientists believe wolves are a keystone species.
Keystone species are species on which a large number of other plants and animals depend.
"The removal of a keystone species can lead to the extinction of other species," Ripple said.
According to Smith, the reintroduction of wolves has affected more than 25 species in Yellowstone.
"We think that Yellowstone will be a different place in 20 years because of wolves," Smith said.
Not everyone is happy with the wolves' return, however. Some farmers say that wolves kill their
animals.
"Ranchers want to limit the number of wolves in the area, because if there are too many wolves, they
always get in trouble," said Jennifer Ellis of the Idaho Cattle Association. "Many people who live in
wolf-inhabited areas have had not only their cows, calves, and sheep killed by wolves, but also their
cats, dogs, and horses."
Ripple noted that there is a program in place to pay farmers for any money they lose due to wolves
killing cattle. Some farmers may not be happy, but many scientists believe that Yellowstone is starting
to look more like it did before people began to interfere with the animals there.
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http://www.ypf.org/pdfs/19.pdf
Relationship between the sea otters and kelp
The relationship between the sea otters and kelp
is a prime example of the top-down cascade type
of food chain that the highest trophic level can
determine the populations of the lower trophic
levels (Ricklefs, 1997). Sea otters affect the
abundance of kelp indirectly by consuming sea
urchins at a high rate because sea urchins are
usually more abundant than other herbivorous
species. Without the presence of sea urchins,
kelps manage to establish successfully along
the rocky shoreline.
In areas where sea otters are absent, sea urchins
population growth explodes due to the lack of
predators and they tend to be more efficient
competitors among the other marine invertebrate
species. This results in the decline of kelp
abundance because they can not sustain the high grazing rate by sea urchins.
In areas where large sea otter population has occupied for a long period of time (i.e. several decades), the
sea urchin population has either diminished or high density of small sea urchins have formed. Heavy
growth of kelp is found in areas like this. Without the sea urchins, sea otter's diet in these areas tends to
have a larger selection that ranges from crabs to migratory fish (Paine, 1993).
The presence of sea otter population in a kelp forest
community has great impacts. When sea otters are
present in great numbers, species in the community tend
to be more diverse. The heavy growth of kelp attracts
small species that use kelp as a shelter to avoid
predation. Therefore, larger fish species are attracted into
the area due to the abundant of food resource. Larger
mammals such as seals will colonize along these
shorelines as feeding ground and gray whales will also
use it as a breeding ground due to the safe environment.
The large biodiversity also suggests why sea otters' diet
varies greatly in heavily occupied territory.
Since sea otters have such great impacts on the kelp
forest community, they are recognized as "keystone" species that can determine the health of a
community due to their presence. Interaction between the sea otters and sea urchins also prevents the
competitive exclusion of other marine invertebrates. By lowering the sea urchin population, sea otters
give other species populations more advantages to grow.
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