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Predation – one species feeds on another  enhances fitness of predator but reduces fitness of prey

Predation – one species feeds on another  enhances fitness of predator but reduces fitness of prey. ( +/– interaction). Types of predators . Carnivores – kill the prey during attack Herbivores – remove parts of many prey, rarely lethal. Parasites – consume parts of one or few prey,

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Predation – one species feeds on another  enhances fitness of predator but reduces fitness of prey

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  1. Predation – one species feeds on another  enhances fitness of predator but reduces fitness of prey (+/– interaction)

  2. Types of predators Carnivores – kill the prey during attack Herbivores–remove parts of many prey, rarely lethal. Parasites – consume parts of one or few prey, rarely lethal. Parasitoids –kill one prey during prolonged attack.

  3. Diet breadth consumes only one prey type narrow diet specialist generalist broad diet consumes many prey types

  4. Why are ecological interactions important? Interactions can affect distribution and abundance. Interactions can influence evolution.

  5. How has predation influenced evolution? Adaptations to avoid being eaten: spines (cactii, porcupines) hard shells (clams, turtles) toxins (milkweeds, some newts) bad taste (monarch butterflies) camouflage aposematiccolors mimicry

  6. Camouflage – blending in

  7. Aposematic colors – warning

  8. Is he crazy???

  9. Mimicry– look like something that is dangerous or tastes bad

  10. Mimicry– look like something that is dangerous or tastes bad Mullerian mimicry – convergence of several unpalatable species

  11. Mimicry– look like something that is dangerous or tastes bad Batesian mimicry – palatable species mimics an unpalatable species model mimic mimics model

  12. Why are ecological interactions important? Interactions can affect distribution and abundance. Interactions can influence evolution.

  13. Predator-prey population dynamics are connected Predators kill prey  affects prey death rate dNprey/dt = rNprey – pNpreyNpredator change in prey population deaths due to predation per capita rate of growth without predation

  14. Predator-prey population dynamics are connected Predators kill prey  affects prey death rate dNprey/dt = rNprey – pNpredatorNprey predation rate • prey population size depends on number of predators • with few predators, prey population grows • with many predators, prey population shrinks

  15. Predator-prey population dynamics are connected Predators eat prey  affects predator birth rate dNpredator/dt = cpNpreyNpredator – dNpredator death rate change in predator population births due to predation

  16. Predator-prey population dynamics are connected Predators eat prey  affects predator birth rate dNpredator/dt = cpNpreyNpredator – dNpredator conversion rate of prey to baby predators predation rate • predator population size depends on number of prey • with many prey, predator population grows • with few prey, predator population shrinks

  17. Predator-prey population dynamics are connected  affects prey death rate  affects predator birth rate Predators kill and eat prey dNprey/dt = rNprey – pNpredatorNprey dNpredator/dt = cpNpreyNpredator – dNpredator • with few predators, prey population grows • with many prey, predator population grows • with many predators, prey population shrinks • with few prey, predator population shrinks N time

  18. Lotka-Volterra models describe predator and prey population cycling. Real world predator and prey populations can cycle in size.

  19. Why are ecological interactions important? Interactions can affect distribution and abundance. Interactions can influence evolution.

  20. Keystone species affect community structure Predators can allow coexistence of competing prey competitors Barnacles Mussels Balanus Mytilus (Paine 1966)

  21. Keystone species affect community structure Predators can allow coexistence of competing prey Starfish predator Pisaster competitors Barnacles Mussels Balanus Mytilus (Paine 1966)

  22. Experiment - Remove the predator How can we test the effect of a predator on community structure? Starfish Pisaster Barnacles Mussels Mytilus Balanus

  23. Removal experiment - mussels are the dominant competitor - competitive exclusion of barnacles starfish removed mussels % of inter- tidal zone barnacles time

  24. What is the effect of the predator on the structure of this community? - starfish allow coexistence of competitors starfish removed mussels % of inter- tidal zone barnacles time

  25. How do starfish promote coexistence? Starfish Pisaster Barnacles Mussels Balanus Mytilus Starfish are picky – they prefer mussels (dominant competitor), which allows barnacles (weaker competitor) to coexist.

  26. Keystone species affect community structure disproportionately to their abundance. Picky predators can promote coexistence among competing prey species. Competitive exclusion is prevented when the dominant competitor is the preferred prey.

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