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Review – Consumer-Resource Interactions

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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  1. 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

  2. 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

  3. Review – Consumer-Resource Interactions • consumer-resource systems can have more than one stable state: • consumer-imposed equilibrium • resource-imposed equilibrium K

  4. Facilitation commensalism, mutualism & symbiosis

  5. 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

  6. Mutualism • Obligate: one or both partners require mutualistic relationship for survival • Facultative: species can live without their mutualistic partner

  7. 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

  8. 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

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

  10. Facilitation – refuge from predation • One species can protect another species from predators • physical or chemical shelter (or both) • camouflage

  11. Facilitation – refuge from predation

  12. Facilitation – refuge from predation

  13. Facilitation – refuge from competition • One species can lessen the effects of competition for another species

  14. Refuge from competition – Oculina and Mithrax

  15. Facilitation – improved nutrient / energy availability • One species can provide another species with improved access to energy or essential nutrients

  16. Interaction Case Studies

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