ECOL 182L LAB7

Predators and Prey: Adaptations to Lifestyle: 

Predators and Prey: Adaptations to Lifestyle Biology 182 Lab 7 Joanna Gress Sections 23 and 43

Slide2: 

Optimality Theory 1. Decisions - selecting a behavioral option 2. Currency - what is being maximized? 3. Constraints - behavior, morphology, physiology Optimality models attempt to predict the combination of costs and benefits that will ultimately maximize an individual’s inclusive fitness Animals are not perfectly adapted to their environment (mutation, rapid environmental change, evol. lag). Also, they don’t “work” on the assumptions presented in models. Natural selection is the mechanism which works as a maximizing process.

Slide3: 

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

Slide4: 

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.

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

Slide6: 

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

Slide7: 

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 aposematic colors mimicry

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Camouflage – blending in

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Aposematic colors – warning

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Is he crazy???

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Mimicry – look like something that is dangerous or tastes bad

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

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

Slide14: 

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

Slide15: 

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

Slide16: 

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

Slide17: 

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

Slide18: 

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

Slide19: 

Predator-prey population dynamics are connected Predators kill and eat prey 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  affects prey death rate  affects predator birth rate dNprey/dt = rNprey – pNpredatorNprey N time

Slide20: 

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

Slide21: 

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

Slide22: 

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

Slide23: 

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

Slide24: 

Barnacles Mussels Balanus Mytilus How can we test the effect of a predator on community structure? Starfish Pisaster

Slide25: 

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

Slide26: 

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

Slide27: 

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

Slide28: 

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.

Guppies: 

Guppies Common Freshwater aquarium fish species. Wild guppies live in mountain streams of tropical forests of Venezuela, Trinidad and Tobago There is a great deal of variety between the populations, many with distinctive coloring or patterning. Those that live in habitats where predators are common tend to be less vividly decorated as a protective measure. Populations that deal with fewer predators are much more colorful. Recent studies suggest that vividly colored males are favored via sexual selection (Handicap principle) while natural selection via predation favors subdued tones. As a result, the dominant phenotypes observed within a reproductively isolated community are a function of the relative importance each factor has in a particular environment

Today’s Lab: 

Today’s Lab Dissection of Rat, Frog and Tadpole-Rinse them off well before dissecting to remove smell! Need to Draw, Label and Answer Questions-can work as a group! EvoBeaker Guppy computer exercise-directions are in the lab manual, handout to turn in. Project Proposal Part II is due after Spring Break. I will approve all projects by Wednesday and email you with my decision. See Handouts for more info!