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Main Points
1) Interspecific competition-- interference and exploitative competition-- example: competitive exclusion by singing mice-- regional species pools and local communities-- example: character displacement in mustelids
2) The dilution effect, nestedness, and Lyme disease outbreaks
Terms: interference competition, exploitative competition, Connell’s hypothesis, regional species pool, local community, habitat filtering, competitive exclusion, character displacement, dilution effect, nestedness
Pre-reading: Monday 4 Nov = NAWednesday 6 Nov = NA
Review sesh Monday 4 Nov. Please come with questions.
Test #2 Wednesday 6 Nov.
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Punchline #1: most dogs are monogamous, but the smallest dogs tend to be polygynous and the largest dogs tend to be polyandrous. This is because of an unusual negative allometrywith body mass and pup weight, and an unusual positive allometry with body mass and litter weight.
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Punchline #2: we discussed a study that tested for the influence of predator hunting strategy and plant defense on the outcome of a trophic cascade. The trophic cascade was contingent on plant defense, but not on predator hunting strategy.
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exploitative competition = negative interaction between pairs of species, routed through a resource.
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Interspecific competition
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Interspecific competition
interference competition = negative interaction between pairs of species, where one species directly inhibits another from consuming a resource.
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L. cana
Peers et al.2013.
Canada lynx bobcat
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• Connell’s hypothesis = species interactions limit distributions in benign conditions; abiotic factors (moisture, temperature) are limiting when they are severe.
Peers et al.2013.
Canada lynx bobcat
• regional species pool = all of the species whose geographic ranges overlap a site/area/locality.
• local community = area over which individuals encounter and interact with one another.
Community assembly and interspecific competition
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Regional species pools
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Regional species pools
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Regional species pools
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X
Regional species pools
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X
Regional species pools
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Regional species pools
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X X
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Regional species pools
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Discussion Q: come up with 2-3 hypotheses for why pinyon mice and American pikas did not occur at this sampling site.
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M. nivalis
• habitat filtering = species at a site share abilities to allow them to exist in particular habitats.
• competitive exclusion = only species that are not too ecologically similar can coexist at a site.
Regional species pools
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Regional species pools and competitive exclusion
19Pasch et al. 2013.
Alston’s singing mouseScotinomys teguina
Chiriqui singing mouseScotinomys xerampelinus
20Pasch et al. 2013.
Alston’s singing mouseScotinomys teguina
Chiriqui singing mouseScotinomys xerampelinus
21Pasch et al. 2013.
Alston’s singing mouseScotinomys teguina
Chiriqui singing mouseScotinomys xerampelinus
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M. nivalis
• habitat filtering = species at a site share abilities to allow them to exist in particular habitats
• competitive exclusion = only species that are not too ecologically similar can coexist at a site
• character displacement = divergence of a trait of two or more similar species where they overlap, so that both use different resources
Regional species pools
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M. nivalis
Dayan et al. 1989.upper canine diameter (mm)
1.5 2.0 2.5
Mustela frenata
M. erminea
Character displacement in Mustela
Community Assembly
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Mustela frenata
M. erminea
Community Assembly
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M. erminea
M. nivalis
Community Assembly
Mustela frenata
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M. erminea
M. nivalis
Nestedness and the Dilution Effect
• dilution effect = high host diversity reduces disease risk
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Lyme Disease and the Dilution Effect
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Ostfeld et al. 1996.
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Lyme Disease and the Dilution Effect
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Lyme Disease and the Dilution Effect
• nestedness = tendency for species-poor communities to form regular subsets of species-rich communities
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Nestedness and the Dilution Effect
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Nestedness and the Dilution Effect
From Allen et al. 200333
Nestedness and the Dilution Effect
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