Interactions among populations II: Dynamics of competition between species Flashcards

1
Q

Define ecological community

A

group of species that occur together in space and/or time and compete for the same limiting resources

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2
Q

Give Gause’s principle of competitive exclusion

A

two species cannot coexist on a single limiting resource if other ecological factors remain constant.

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3
Q

Discuss Connell’s barnacles

A
  • Chthamalus is competitively excluded from the lower shore by Balanus
  • persists in the upper shore because it is more tolerant towards dessication
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4
Q

Discuss Gause’s Paramecium

A
  • both Paramecium aurelia and Paramecium bursaria eat bacteria
  • when grown together in a well-stirred mixture, P. aurelia outcompetes P. bursaria
  • if the mixture is not stirred, both species persist (P. bursaria mostly confined to the anoxic bottom of the beaker)
  • P. bursaria, with its photosynthetic symbionts, generates oxygen internally
  • P. aurelia outcompetes P. bursaria under aerobic conditions, but P. bursaria can persist in anoxic conditions where P. aurelia cannot
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5
Q

Describe Fenchel’s snails (Hydrobia)

A
  • Hydrobia ulvae and Hydrobia ventrosa
  • most places you only find one species or the other; appear almost indistinguishable
  • when they are sympatric, there is character displacement
  • H. ulvae becomes significantly larger than H. ventrosa
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6
Q

Describe Tilman’s diatoms

A
  • photosynthetic, planktonic organisms
  • unique silica cell wall
  • can be grown in culture such that silica is the limiting factor
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7
Q

R*

A

concentration of resource at population equilibrium

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8
Q

Describe R*

A
  • theory of competition for a single limiting resource: R*
  • level to which the concentration of a limiting resource is reduced by an equilibrial monoculture of a species
  • minimum resource concentration a species requires for positive population growth
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9
Q

What are the assumptions of R*?

A
  • species compete for a single limiting resource
  • resource is labile and the system is well-mixed
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10
Q

Give an example of a well mixed system

A

nitrogen in soil

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11
Q

Describe the R* prediction

A

species with the lowest R* for the limiting resource is the superior competitor

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12
Q

How to measure R*?

A
  • a variety of ways
  • individuals against each other
  • seed v seed
  • ability to invade a monoculture of the other species
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13
Q

Give a two-species population model that includes both the density of intra (N1) and interspecific (N2) competitors

A
  • dN1/dt = r1N1(K1-N1-alpha12N2)/K1
  • interspecific competitors are weighted by a competition coefficient (α12).
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14
Q

“alpha values”

A

specify the effect of interspecific competition.

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15
Q

When does Lotka-Volterra coexistence occur

A

𝐾1>𝐾2 𝛼12
𝐾2>𝐾1 𝛼21
- if K1 = K2, when interspecific competition coefficients are < 1 (interspecific competition is weaker than intraspecific competition)

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