Competition

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Competition

• Chapter 9

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Niche Concept

• A niche (Hutchinsonian niche) is defined as the
  set of n-resource hypervolume in multidimensional
  space. Each axes represents a resource.
• Functional niche the ecological role that a
  species plays in a community.
• Niche breadth variance in resource use among
  individuals
• Niche separation distance between the mean
  resource use among two species
• Resource overlap is where competition is expected

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Specialist vs. generalist
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Competition Defined

• Competition interaction of 2 or more species
  over a limiting resource causing decreased
  population growth in at least one species
• Preemptive competition competition for space in
  plants
• Interspecific competition competition among 2
  species
• Intraspecific competition competition within a
  species

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Competition defined

• Exploitation competition one species/individual
  significantly reducing the availability of said
  resource for another
• Interference competition a species/individual
  interferes with the ability of another species
  from using a resource (i.e. allelopathy,
  chemicals preventing growth in plants)
• Diffuse competition competition due to
  combination of several competing species

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Proof of competition

• Experimentation (barnacles)
• Observation and inference

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Intraspecific Vs. Interspecific

• Individuals within a species utilize more similar
  resources than individuals among species,
  therefore
• Intraspecific competition is greater than
  interspecific competition
• Plants and self-thinning

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Effects of competition

• Long-term effects character displacement
• Short-term effects competitive exclusion
• Character displacement the two species will
  gradually separate in morphology and physiology,
  to reduce or eliminate the area of competitive
  overlap (character displacement may be useful to
  reduce intraspecific competition (between
  different age classes, sexes, etc))

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Effects of competition

• Competitive exclusion local extinction due to
  interspecific competition
• Competitive exclusion principle no two species
  can coexist for a long time on the same limiting
  resources
• Fugitive species species that quickly colonize a
  disturbed site frequently undergo competitive
  exclusion.

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Conditions for coexistence

• Lotka-Volterra Models
• Zero-growth isoclines (line dN/dt 0)
• Below line, dN/dt is positive, resulting in
  population growth
• Above line, dN/dt is negative, resulting in
  population decline

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Competitive exclusion
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Competitive exclusion
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Unstable equilibrium
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Stable equilibrium
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The End