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Competition

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... related wood warblers. Taxonomically-- closely related ... Myrtle Warbler. Black-throated green. Black-throated green. Blackburnian. Character displacement ... – PowerPoint PPT presentation

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Title: Competition


1
Competition
  • Lecture 15

2
Competition
  • Ecologists have used a variety of types of
    evidence to detect effects of competition
  • Studies of con-generic species
  • Species co-occurrence data and shifts in
    distribution after removal of a competitive
    dominant
  • Character displacement studies

3
Dendroica wablers
  • Five closely related wood warblers
  • Taxonomically-- closely related
  • Similar morphologies
  • Eat insects

4
Use of habitat
Cape May
Blackburnian
Black-throated green
Black-throated green
Bay Breasted
Myrtle Warbler
5
Character displacement
  • Members of the same species should undergo the
    most intense competition
  • Sexual dimorphism in bill size
  • Male and female select different prey

6
Character displacement
  • Comparisons of the same species in allopatry and
    sympatry
  • Allopatricgeographically separated
  • Sympatricoverlapping distributions

7
Snails in Denmark Allopatric
8
Snails in Denmark Sympatric
9
Desert plants
  • In arid and semi-arid environments
  • Water is scarce therefore we would expect plants
    to compete for water
  • Desert plants have many adaptations for
    conserving water
  • Thick cuticle
  • Low surface area leaves

10
Desert plants
  • Distribution patters can be characterized as
  • Random
  • Evenly or over-dispersed
  • Clumped or under-dispersed

11
Randomly dispersed
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
12
Clumped
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
13
Over-dispersed
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
14
If we start with a randomly dispersed plant
community, what would we expect under conditions
of competition?
o
o
o
o
o
o
o
o
o
o
o
o
o
o
High survival
o
o
Low survival
o
o
15
Over time the population will become more evenly
dispersed
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
16
Evidence that desert plants are evenly dispersed
  • Several species of desert plants are evenly
    dispersed
  • But, many other species are clumped or have
    random dispersion patterns
  • Water availability could confound the observed
    patterns

17
A more direct way to look for evidence of
competition
  • Would be to examine individual plants in the
    presence and absence of potential predators
  • Freidman et al. Experiments with Artemisia
    herba-alba
  • Transplanted seedlings near the co-dominant
    species Zygophllum dumosum

18
Size of plants
Mass
Distance to nearest
Focal plant
Neighbour
High
Distance to nearest
Focal plant
Neighbour
Low
19
Survival of Artemisia
Survival
Distance between
Artemisia
Zygophllum
High
Distance between
Artemisia
Zygophllum
Low
20
Conclusions
  • Competition is widespread
  • Evidence from a wide range of taxa
  • Using a variety of types of evidence
  • How widespread and important competition is
    relative to other forces that structure
    communities is less clear
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