W09_L4_FD_Stress_Predation_Jan12

W09_L4_FD_Stress_Predation_Jan12 - Functional Diversity I:...

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1 Clicker Question For communities that have the same species richness, the highest diversity (H’) will be exhibited by the community that shows a ______ relative abundance curve. 1. Concave 2. Convex 3. Horizontal 4. Linear Species in rank order abundance 2 Functional Diversity I: Acquiring Resources • Looking ahead – This morning theme: avoiding predation and stress – This afternoon: the stress of climate change. • READ the IPCC report Jan. 9, 2009 NOTES: The second, and final vote result 128 -120 (or so) clicker questions are NOT for points. More NOTES: textbook reading. I promise that I will have exam questions that are from the text reading assignments and that are not covered in lecture. Practice lectures from the textbook website are a good idea. 3 What determines prey choice? 2. Value of the prey 1. Effort required to capture and consume prey -relative size of predator and prey -prey defenses (e.g., spines, chemicals, cryptic) -energy content -presence of rare / critical nutrients -defenses that reduce digestibility -toxic chemicals Indicates that I probably will not spend time on this in lecture, but that it is part of the lecture notes that I expect you to learn. See the notes section of the slide for further explanation. 4 Benefits = energy content Costs = handling time, the time it takes to pursue, capture, eat and digest the prey, danger encountered Prediction . Species should strive to optimize foraging (be an optimal forager): Maximize (Benefit / Cost) . 5 Big mussels have more flesh, but they also take the longest to crack. Data from Elner and Hughes 1978, Valiela 1995 Breaking time (sec) Prey Size (cm) Small crabs large crabs # prey eaten Actual data E/t (g per sec) x 10 -3 Greatest reward per unit time comes from eating intermediate sized mussels Prediction: Prey value 6 Food for thought : Are humans doomed by our evolutionary history? Maximizing energy over time can become maladaptive when energy is abundant (when it is not limiting).
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7 Question Which statement strikes you as most plausible . A. Habitats that are rich in food resources should favor specialist feeding behaviors. B. Habitats that are rich in food resources should favor generalist feeding behaviors. C. There is no a priori reason to believe that resource rich environments should favor either generalist or specialist feeding behaviors. 8 The “optimal” solution can change with the environment. An experiment with Bluegill sunfish feeding on different sized crustaceans Werner et al. 1983 (53.10 in text) At low prey density, cost of finding new prey is high relative to costs of handling As prey density increases, cost of finding new prey is lower, so it pays to only bother with the most profitable prey Does the result fit the prediction? 9
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W09_L4_FD_Stress_Predation_Jan12 - Functional Diversity I:...

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