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Competition experiments
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What are possible response variables for a competition experiment?
What is competition? What are possible response variables for a competition experiment?
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Associate species Focal species Resource
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Some competition questions
Does associate species X affect focal species Y? How does interspecific competition (effect of X on Y) compare to intraspecific competition (effect of Y on Y)? Is competition asymmetrical? That is, does either X affect Y more than Y affect X, or vice versa? Is the strength of competition dependent on the density of the associate species (X)? Density of the focal species (Y)?
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Focal species Additive design Associate
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N associate Monoculture of focal N focal species
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Substitutive design (replacement series)
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Monoculture of associate
N associate Monoculture of focal N focal species
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Monocultures of associate
Response surface Monocultures of associate N associate Monocultures of focal N focal species
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What two factors/processes are confounded in your experimental design?
Which type of competition question can your design answer? Which can it not?
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Some possible types of competition questions
Does associate species X affect focal species Y? Additive How does interspecific competition (effect of X on Y) compare to intraspecific competition (effect of Y on Y)? Is competition asymetrical? That is, does either X affect Y more than Y affect X, or vice versa? Is the strength of competition dependent on the density of the associate species (X)? Density of the focal species (Y)?
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Some possible types of competition questions
Does associate species X affect focal species Y? Additive How does interspecific competition (effect of X on Y) compare to intraspecific competition (effect of Y on Y)? Substitutive Is competition asymetrical? That is, does either X affect Y more than Y affect X, or vice versa? Is the strength of competition dependent on the density of the associate species (X)? Density of the focal species (Y)?
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L-shaped additive or substitutive
Some possible types of competition questions Does associate species X affect focal species Y? Additive How does interspecific competition (effect of X on Y) compare to intraspecific competition (effect of Y on Y)? Substitutive Is competition asymetrical? That is, does either X affect Y more than Y affect X, or vice versa? Is the strength of competition dependent on the density of the associate species (X)? Density of the focal species (Y)? L-shaped additive or substitutive
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L-shaped additive or substitutive
Some possible types of competition questions Does associate species X affect focal species Y? Additive How does interspecific competition (effect of X on Y) compare to intraspecific competition (effect of Y on Y)? Substitutive Is competition asymetrical? That is, does either X affect Y more than Y affect X, or vice versa? Is the strength of competition dependent on the density of the associate species (X)? Density of the focal species (Y)? Additive L-shaped additive or substitutive
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Additive series design for container mosquito larvae
Example: Additive series design for container mosquito larvae
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Aedes albopictus invades N America from SE Asia in 1985, via used tire trade at Houston
1985 1996
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Breeds in containers habitats (old tires, treeholes), like native species, Aedes aegypti
Aedes albopictus
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Ranges overlap, potential for interspecific competition
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Experimental design (“Additive series”)
Aedes albopictus Substitutive or replacement series Aedes aegypti Juliano, S Species introduction and replacement amongst mosquitoes: interspecific resource competition or apparent competition? Ecology 79:
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Experimental design (Additive series)
Aedes albopictus Addition design Aedes aegypti Juliano, S Species introduction and replacement amongst mosquitoes: interspecific resource competition or apparent competition? Ecology 79:
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Aedes aegypti performance in these treatments Aedes albopictus
Experimental design Can asses Aedes aegypti performance in these treatments Aedes albopictus Aedes aegypti Juliano, S Species introduction and replacement amongst mosquitoes: interspecific resource competition or apparent competition? Ecology 79:
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Aedes aegypti response Aedes aegypti response Aedes aegypti response
Hypotheses: Albo has an effect on Aeg, and effect of 1 Albo = 1Aeg Aedes aegypti response aeg albo Aedes albopictus Albo has no effect on Aeg, so effect of 1 Albo = 0 Aeg Aedes aegypti response Aedes aegypti aeg albo Albo has an effect on Aeg, but effect of 1 Albo < 1Aeg Aedes aegypti response aeg albo
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Aedes aegypti response Aedes aegypti response Aedes aegypti response
Hypotheses: Albo has an effect on Aeg, and effect of 1 Albo = 1Aeg Aedes aegypti response aeg albo Aedes albopictus Albo has no effect on Aeg, so effect of 1 Albo = 0 Aeg Aedes aegypti response Aedes aegypti aeg albo Albo has an effect on Aeg, but effect of 1 Albo < 1Aeg Aedes aegypti response aeg albo
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Aedes aegypti response Aedes aegypti response Aedes aegypti response
Hypotheses: Albo has an effect on Aeg, and effect of 1 Albo = 1Aeg Aedes aegypti response aeg albo Aedes albopictus Albo has no effect on Aeg, so effect of 1 Albo = 0 Aeg Aedes aegypti response Aedes aegypti aeg albo Albo has an effect on Aeg, but effect of 1 Albo < 1Aeg Aedes aegypti response aeg albo
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Aedes aegypti survivorship
Results Aedes aegypti survivorship aeg albo ANOVA: treatment x food x tire(=block) Followed by posthoc to find difference between levels
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