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Review – Consumer-Resource Interactions PowerPoint PPT Presentation


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Review – Consumer-Resource Interactions. Exploitative interactions (+,-) occur when a consumer species benefits at the expense of a resource species – e.g., herbivory, parasitism, predation Consumers can set limits on the distribution and abundance of resource populations

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Review – Consumer-Resource Interactions

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Review – Consumer-Resource Interactions

  • Exploitative interactions (+,-) occur when a consumer species benefits at the expense of a resource species – e.g., herbivory, parasitism, predation

  • Consumers can set limits on the distribution and abundance of resource populations

  • Consumer-resource interactions produce cyclical growth and decline in population sizes of the interacting species: predator-prey cycles


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Review – Consumer-Resource Interactions

  • predator-prey cycles generally stable, but environmental changes can act to change intensity, periodicity of cycles

  • Lotka-Volterra model can reproduce predator prey cycles mathematically, but lacks some important aspects of the real process:

    • time lag in predator-prey cycling due to time required to convert energy into actual offspring

    • limits set on growth by carrying capacity

    • limits set on predators by functional response


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Review – Consumer-Resource Interactions

  • consumer-resource systems can have more than one stable state:

    • consumer-imposed equilibrium

    • resource-imposed equilibrium

K


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Facilitation

commensalism, mutualism & symbiosis


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Facilitation

  • Interaction in which one or both parties benefits, and neither is negatively affected

  • Commensalism (+,0): one individual benefits from interaction, the other is unaffected

  • Mutualism (+,+): both individuals benefit from their interaction

  • Symbiosis: a long-term, close mutualistic association between two organisms


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Mutualism

  • Obligate: one or both partners require mutualistic relationship for survival

  • Facultative: species can live without their mutualistic partner


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Facilitation

  • The beneficial effects of facilitation can be realized in several different ways:

    • reduced environmental stress

    • reduced predation

    • reduced competition

    • increased access to resources

    • transport / dispersal


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Facilitation – refuge from physical stress

  • One species can provide another species with protection from a stressful environment

    • nature of interaction can shift with time or changes in environment


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Refuge from physical stress: mussels, spartina, marsh elder and black rush


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Facilitation – refuge from predation

  • One species can protect another species from predators

    • physical or chemical shelter (or both)

    • camouflage


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Facilitation – refuge from predation


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Facilitation – refuge from predation


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Facilitation – refuge from competition

  • One species can lessen the effects of competition for another species


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Refuge from competition – Oculina and Mithrax


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Facilitation – improved nutrient / energy availability

  • One species can provide another species with improved access to energy or essential nutrients


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Interaction Case Studies


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