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Marine Ecology May 7, 2007 Between the tides: Interactions 1
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Zonation: Role of physical/chemical factors vs. biological interactions Joe Connell, 1972: Hypothesis Physical factors primarily responsible for upper limits Biological interactions primarily responsible for lower limits Support for hypothesis?
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Effects of biological interactions on zonation/distribution in intertidal Competition for space Predator-prey interactions Role of grazers Symbiotic relationships and species distribution Larval ecology Role of disturbance
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Competition for space Example: Vertical distribution of the intertidal barnacles Chthamalus Balanus
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Barnacle zonation (after Connell, 1961)
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Barnacle zonation in New England
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Competition for space Example: Algal distribution Species with small body forms initially settle and grow (opportunistic) Species with small body forms initially settle and grow (opportunistic) Slower-growing, larger forms outcompete if no disturbance occurs Slower-growing, larger forms outcompete if no disturbance occurs
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Competition for space Example: Lottia gigantea (owl limpet) territoriality
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Competition for space Example: Mussel bed succession
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Predator-prey interactions Example: Pisaster ochraceus and the mussel Mytilus californianus Caging experiments Follow-up (14-17 yrs) Comparisons to Chile and New Zealand studies
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Bob Paine’s experiments Castro and Huber, Fig. 11.22
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Fig. 6.18: Pisaster ochraceus as a Keystone species
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Fig. 6.19: Natural experiments on New England coast (Menge and Lubchenco)
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Predator-prey interactions Example: Nucella sp. Predatory snail Excretes enzymes with an accessory boring organ to dissolve “shell” of barnacles Has operculum: enables it to retreat into shell at low tide
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Predator-prey interactions Distribution within a zone Oystercatchers affect limpet distribution Black oystercatcher (Pacific) Variable oystercatcher (New Zealand)
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Role of grazers Limitation of algae by grazers Overview Case study: Katharina tunicata (chiton)
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Role of grazers Maintenance of diversity by grazers Example: Effects of snails on algal diversity in a tidepool.
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And then the gulls move in…
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Role of grazers Grazing deterrents Morphological Chemical defenses Crustose vs. erect forms Size refuges Limitation of grazers by algae
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Symbiotic relationships One species creating a suitable habitat for another Example: Mussel beds
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Symbiotic relationships Mutualistic relationships Example: Anthopleura elegantissima
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