Download Ecosystem Structure and Roles

Community Ecology: Structure,
Species Interactions, Succession,
and Sustainability
Other labels for species
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Native
Non-native
Indicator
keystone
Native vs. nonnative species
• The species that naturally/normally live and
thrive in a particular area are called native
species
• A species that migrates into, or is
accidentally or intentionally introduced into
an ecosystem is a nonnative species
• How do these species arrive to their new
destination?
• Nonnative = exotic = alien= invasive
Nonnative nightmares!
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Zebra mussels
Cane toads
African bees (killer bees)
Eurasian watermillfoil
Snakehead fish
Ginko trees
Purple loosestrife
Why are exotic species
intentionally brought/introduced
to a new area?
Why is this bad?
• INVASIVE and HIGHLY PROLIFIC!
Indicator species
• Species that serve as early warnings that a
community or ecosystem may be at risk or
being damaged are called indicator species
• They are very sensitive to environmental changes
• “Many species don’t need us, but we and other
species need them.”
Some additional info.
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Bioindicators
indicator sp.
coyotes as indic. sp.
lichens as bioindicators
surfers as ind. sp.
Examples of indicator species
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Most stream macro-invertebrates
Birds
Trout
Lichens
amphibians
Keystone species
• A species whose role in an ecosystem are much
more important than their numbers or biomass
would indicate are called keystone
species
• Often linked to a large number of other species
• Play critical role in the structure, function, and
integrity of an ecosystem.
• They are the link to many other species!
More of what they do…
• Process material out of proportion to their
#’s or biomass
Examples of keystone species
• Bees, bats, hummingbirds, ants for pollinating
and seed dispersal
• Dung beetles for removal, burial, and
recycling of waste
• Sea otters for eating sea urchins which
destroy kelp beds
• American alligator, wolf, lion, great white
shark for keeping prey pop.’s in check
• Beavers for modifying habitat from
streams/rivers into ponds/lakes
EXAMPLES:
• Keystone species
• another keystone species
Edward O. Wilson says….
• “The loss of a keystone species is
like a drill accidentally striking a
power line. It causes lights to go
out all over.”
Species interactions
• Intraspecific competition – same sp.
Competing for resc.
• Interspecific competition – different sp.
Competing for resc.
• Predation
• Symbiosis (mutualism, commensalism,
parasitism)
Intraspecific compet.
• SAME sp. Compete
– Through territoriality
• Sp. Mark their home, nesting or feeding site
• Defend it against members of own sp.
Interspecific competion
• When two or more different species compete for
limited resources
– LIMITED RESOURCES =space, matter, water, food,
sunlight, nesting sites, hiding spots, etc.
• Those involved are harmed to varying degrees
depending on which is the best competitor
• If resc. Are abundant...sp. get closer to occupying
their fundamental niche BUT if not…parts of
their fundamental niches overlap = COMPET.!
When fundamental niches
overlap…
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1 sp. May be forced to migrate
Change eating habits
Dec. in pop. Via nat. sel.
Extinction may occur
Types of Interspecific
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Interference competition
Exploitation competition
Competitive exclusion
Competitive exclusion principle
Interference competition
• One species may limit another’s access to
resources
• Behaviors include:
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establishment and defense of territory
Chemical secretions, poisoning
Bird calls to mark territory
Sp. ACTIVELY INTERFERE with other sp.
Access to the limited resc.
Exploitative competition
• Competing species attempt to exploit their
“fitness” over the competition by using their
adaptations (reproductive success vs. strength)
• For example:
– Faster
– Stronger
– Better vision
• So one species gets more of a resource and this
limits the growth, reproduction, and survival of
the competing species
• Species EXPLOIT their best trait!
The competitive exclusion
principle
• One niche, one species, one place
– This is why one sp. Is excluded
• No two species can occupy the same niche
at the same time, indefinitely if there is not
enough of a resource
• 1 sp. eliminates another sp. In an area via
competition for a limited resource.
• See research using paramecium
Ways to avoid competition..
• Resource partitioning = same
habitat…different niche
• USE REALIZED NICHE!!!!
– warblers
Resource partitioning
• Dividing up scarce resources so that species
with similar requirements can use them at
different times, or in different ways, or in
different places
• Examples:
– Wetlands
– Warblers in Spruce trees
Character displacement
• Happens through evolution
• When similar species in an area develop slightly differing
traits or characteristics (including behavioral) that allow
them to use different resources
• Examples:
– Bills of birds
– Tortoise shells
Predation
• Members of one species feed directly on all
or part of a living organism of another
species
• The predator benefits and the prey is
harmed (but does not have to be killed)
Predator-prey relationships
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Carnivores
Herbivores
Prey does not have to be killed
We are direct and indirect predators
Pros and cons…
• Although a single animal may be harmed,
predators actually HELP prey species by
killing the sick, weak, and aged members
– This limits competition for resources among
prey
– And may improve gene pool for species
Predatory behaviors…
• Pursuit
• Ambush
Prey behaviors….
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Camouflage
Warning coloration
Mimicry
Chemical warfare
Protective shells
Limbs that break off
Symbiosis
• Is a long-lasting relationship in which
organisms live together intimately
• Three types of symbiotic relationships are
– Parasitism
– Mutualism
– commensalism
Parasitism
• Parasites
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Live in or on host
Usually smaller than host
Draws nourishment from host
Gradually weakens host
Rarely kills host
Types of parasites….
• Endoparasites- live INSIDE host
– Tapeworms, parasitic wasps, plasmodium
• Ectoparasites – attach to OUTIDE/ ON
host
– Lice, ticks, mosquitos, athlete’s foot fungus,
lampreys
Mutualism
• Win-win relationship
• Pollination relationship between plants and
insects
• Nutritional relationships
– Lichens (algae and fungus)
– Termites and protozoans (home/digest wood)
– Rhizobium bacteria and legumes (N
conv./sugar)
More mutualism
• Protective mutualism
– Birds and elephants and Rhinos
– Stinging ants and acacia trees
Commensalism
• One species benefits while the other is
neither helped nor harmed
• Some examples are:
– Epiphytes (orchids and bromeliads)
– Barnacles on whales
Ecological succession
• Ecologists describe ecosystems by:
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Physical appearance
Niche structure
Species diversity
Species abundance
Ecosystems change
• Ecosystems change in response to changing
environmental conditions
• Succession can happen gradually or rapidly
depending on environmental conditions
Primary succession
• The development of communities in a lifeless area
with no soil or bottom sediment
• Such places might be barren rock, newly cooled
lava flow, abandoned highway, boulders/exposed
bedrock from retreating glaciers
• Primary succession begins with pioneer species
– Lichens and mosses are pioneer organisms
• They trap soil particles
• Lichens secrete acids breaking down the rock
• FORMING SOIL!
Successional species
• Pioneers
• Early successional plant species
– Grasses, herbs, ferns
• Midsuccessional plant species
– Grasses, shrubs
• Late successional plant species
– Trees
– Ends in a stable and complex forest
Secondary succession
• Begins in an area whose natural vegetation
has been removed, disturbed, destroyed
• Abandoned farms, cut forests, burned
forests
• Ends in a stable and complex forest
Pond succession
• Occurs in ponds, lakes, streams
Animal succession?
• Ecological succession focuses on changes in
vegetation
• But as plant succession proceeds, the numbers and
types of animals changes with it
• Different wildlife can be found at different
successional stages in each ecosystem
• At each stage of succession, species diversity,
trophic structure, niches, nutrient cycling and
energy flow changes!
Factors affecting the rate of
succession
• Facilitation – 1 sp. modifies the env. and
makes an area suitable for sp. with different
niche requirements to survive
• Inhibition – early sp. hinder the
establishment and growth of another sp.
(emit toxins)
• Tolerance – late successional sp. aren’t
affected by plants of earlier stages of succ.
The role of disturbances in
succession
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Human caused vs. natural
Catastrophic vs. gradual
Flood
Fire
Groundwater depletion
Waterlogging soils
Pesticide application
Pollution
Intermediate Disturbance
Hypothesis
• Communities that experience fairly
frequent, moderate disturbances have the
greatest diversity of species
Climax communities
• All succession ends theoretically with a
climax community being established
– Stable and complex ecosystem of long-lived
tree species