Community Ecology: Study of interactions among species, ecological succession'

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Community Ecology Study of interactions among
species, ecological succession.

• Community interactions are classified by whether
  they help, harm, or have no effect on species
  involved.

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Interspecific Interactions

• Interactions of different species
• Competition, Predation, Herbivory, Symbiosis
  (parasitism, mutualism, commensalism)

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Competition

• Interspecific competition (-/-) Individuals of
  different species compete for the same resource
  that limits their growth and survival.
• With unlimited resources
• would there be a need
• for war?

Country
Labor
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Competitive Exclusion

• In the absence of disturbance, one species
  will use the resources more efficiently and thus
  reproduce more rapidly than the other.
• Even a slight reproductive advantage will
  eventually lead to a local elimination of the
  inferior competitor.

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Ecological Niches

• Definition the sum of a species use of the
  biotic and abiotic resources in its environment.
• An organisms ecological role in an ecosystem.
  Job.
• Components examples temperature range, size of
  branches, kinds of insects it eats, etc.

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Resource Partitioning

• Resource partitioning is the division of
  environmental resources by coexisting species
  populations such that the niche of each species
  differs by one or more significant factors from
  the niches of all coexisting species populations.
  Two sympatric species may eat slightly different
  foods or utilise other resources in different
  ways.
• The differentiation of niches that enable similar
  species to coexist in a community.
• Evolution through natural selection
• The ghost of competition past
• Indirect evidence of earlier niche
  differentiation.
• As a result of competition, a species
  fundamental niche, which is the niche potentially
  occupied by that species, is often different from
  its realized niche, the portion of fundamental
  niche that it actually occupies in a particular
  environment.

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Character Displacement

• Definition The divergence of adaptations or
  other characteristics in two similar species in
  locations where the animals share habitat. This
  divergence is spurred on by competition between
  the two species in areas where their ranges
  overlap.

Hummingbirds
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Herbivory

• ( /- ) An herbivore eats part of a plant or
  alga.
• Plants have various chemical mechanical
  defenses against herbivory.
• Herbivores have specialized
• adaptations for feeding.

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Predation

• ( /- )
• One species, the predator, kills and eats the
  other, the prey.

Predation has led to diverse adaptations,
including mimicry.
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Symbiosis

• Individuals of two or more species live in close
  contact with one another.
• Parasitism The parasite derives nutrishment from
  a second organism, its host, which is harmed.
• Mutualism Both species benefit from the
  interaction.
• Commensalism One species benefits from the
  interaction, while the other is unaffected by it.

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Dominant and keystone species exert strong
controls on community structure.

• Dominant species are those species in a
  community that are the most abundant or that
  collectively have the most mass.
• A keystone species is a species whose very
  presence contributes to a diversity of life and
  whose extinction would consequently lead to the
  extinction of other forms of life. Keystone
  species help to support the ecosystem (entire
  community of life) of which they are a part.

Black Tailed Prairie Dog
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Invasive Species

• Noxious Weed
• Pests

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Foundation Species (Ecosystem Engineers)

• A foundation species is a dominant primary
  producer in an ecosystem both in terms of
  abundance and influence. Examples include kelp
  in kelp forests and corals in coral reefs.
• Some organisms exert their influence on a
  community not through trophic interactions, but
  by causing physical changes in the environment.
  Ex Beavers
• Facilitators

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Climax Community

• Group of plants and animals that is best able to
  exploit the environment in which it exists. It is
  brought about by succession (a change in the
  species present) and represents the point at
  which succession ceases to occur.

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Biodiversity consists of the variety of life on
earth.

• It contains several components
• Genetic diversity (eg. heterozygosity, alleles)
  
• Species diversity (eg. richness, H')
• Diversity index some overall measure of
  diversity. Usually combines aspects of richness
  and evenness. The most commonly used index is the
  Shannon index (H')
• H' - ? pilog(pi)
• Community diversity (many measures)
• Landscape diversity (many measures)
•  
• Species richness is the number of species in a
  given area.

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Equitability (evenness) Uniformity of abundance
in an assemblage of species. Equitability is
greatest when species are equally abundant.
                                                  
                                                  
              
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ALPHA, BETA, AND GAMMA DIVERSITY

• alpha diversity the diversity within a site, or
  quadrant. a.k.a. local diversity.
• beta diversity the change in species composition
  from site to site. a.k.a. species turnover
• gamma diversity the diversity of a landscape, or
  of all sites combined. a.k.a. regional diversity

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Food Webs
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Limits

• Most food chains are 4 5 links or less. Why?
• Energetic Hypothesis The length of the food
  chain is limited by the inefficiency of energy
  transfer along the link. 10 rule
• Dynamic Stability Hypothesis Long food chains
  are less stable than short ones.

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Bottom-Up Top-Down Controls

• Relationships between plants and herbivores
• V vegetation H herbivores
• Bottom up model V H more vegetation
  more herbivores
• H V
• Top down model H V herbivores control
  the vegetation
• Trophic Cascade Model
• P H V N predators control the
  herbivores which control the vegetation which
  controls the nutrients.

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Biomanipulation
Polluted State
Restored State
Fish
Abundant
Rare
Zooplanton
Rare
Abundant
Algae
Abundant
Rare
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Disturbance influences species diversity
composition.

• Nonequilibrium Model
• Most communities are constantly changing after
  being affected by disturbances.

• Disturbance
• an event storm, fire, flood, drought, over
  grazing, or human activity
• The intermediate disturbance hypothesis states
  that intermediate levels of disturbance maximize
  species diversity because competitively dominant
  species exclude subordinate species at low
  disturbance, but too much disturbance leads to
  local extinctions.

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Ecological Succession

• Secondary occurs after a primary has been
  cleared by some disturbance.

Primary From beginnings of nature.
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Biogeographic factors affect community
biodiversity.

• The two key factors in latitudinal gradients of
  species richness are probably evolutionary
  history and climate.
• Evapotranspiration
• Species area curve
• The larger the geographic area, the more species
  it has.

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Island Equilibrium Model
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Community ecology is useful for understanding
pathogen life cycles and controling disease.

• PathogensDisease causing microorganisms,
  viruses, viroids, prions
• Zoonatic pathogens Those that are transferred
  from other animals to humans, either by direct
  contact with infected animal or through a an
  intermediate organism, a vector.
• Vector Usually parasites such as ticks, lice,
  mosquitoes

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Images

• www.okstate.edu/.../bisc3034/lnotes/richsucc.jpg
• www.okstate.edu/.../bisc3034/lnotes/biodiver.htm
• http//evolution.berkeley.edu/evosite/evo101/image
  s/katydid_225.jpg
• http//images.encarta.msn.com/xrefmedia/aencmed/ta
  rgets/images/scp/T014832A.gif
• www.livewild.org/CostaRica/Pics/a6024.jpg
• www.spiritoftrees.org
• http//www.cbu.edu/seisen/ExamplesOfCommensalism_
  files/image002.jpg
• www.nearctica.com
• http//faculty.etsu.edu/karsai/ot257.jpg
• http//www.boquetriver.org/adopttrophic.gif
• http//www.arcytech.org/java/population/images/foo
  d_chain.jpg
• http//www.rndindia.info/newslet/_newsl2.gif
• http//faculty.southwest.tn.edu/rburkett/GB20Pro1
  1.jpg
• http//animals.about.com/od/c/g/characterdispla.ht
  m
• http//web2.uwindsor.ca/courses/biology/macisaac/5
  5-437/lecture10/MWBASIC.JPG