1. Ecology 8310 Population (and Community) Ecology Predator-prey Response to Thursday… Empirical patterns: Luckinbill's experiments Huffaker's mites Lake patterns in phyto-zoop as f(nutrients) Causes of positive increases in consumer-resource

2. For r>aFor r<a From Arditi and Ginzburg 2012. How Species Interact

3. Tests that inform predator-prey models

4. Ecology 54:1320-1327

5. Paramecium alone Note extinction after 1-3 predator-prey cycles. Baseline dynamics:

6. Recall unstable equilibrium in "paradox"

7. N P dN/Ndt=0 dP/Pdt=0 Unstable How can we stabilize this system?

8. N P dN/Ndt=0 dP/Pdt=0 Reduce predators attack rate (add cellulose to medium):

9. N P dN/Ndt=0 dP/Pdt=0 Reduce prey's K (reduce food in medium):

10. Paramecium alone Increased persistence (stability)! Results: See Harrison (1995, Ecology) for data-model comparison

11. one predator; one prey live on oranges Huffaker's mites:

12. Results: Without predator: prey persist…

13. Results: With predator: extinction

14. How might the system be modified to facilitate persistence?

15. 1) Network: Groups of oranges, coupled by migration… Many did not work… 2) Reduce predator dispersal ability among patches: dispersed oranges amid rubber balls, non resource; added barriers to slow down predator movement…

16. Patch network: P a NP N a PN P a NP N a PN P a NP N a PN P a NP N a PN P a NP N a PN

17. Results: Patches transition: none  prey  predator and prey  predator  none

18. Other data…enrichment in lakes

19. Compared phytoplankton in enclosures with vs. without fish (i.e., phyto only vs. phyto & zoop) in lakes that varied in nutrients (TP) What do you expect based on LV pred-prey model?

20. Expectation: Enrich system: e.g., increase prey’s r and K 1)No zooplankton 2)Zooplankton (and no fish) N (phytoplankton) P (zooplankton)

21. "No" Zoops (with fish) without fish

22. Is this the pattern we see in real lakes?

23. Phytoplankton (algae)

24. Zooplankton (e.g., Daphnia)

25. Why the discrepancy?

26. 1.Interference among consumers 2.Pseudo-interference (consumer stage- structure) 3.Heterogeneity within trophic levels

27. Expectation: Effect of interference… N (phytoplankton) P (zooplankton)

28. Are they other ways to create this slanted isocline?

29. Small Bluegill Large Bluegill Littoral Invertebrates Zooplankton

30. Juvenile bottleneck: N (adult resource) P (adult density)

31. What about resource heterogeneity?

33. Zooplankton Inedible Algae Edible Algae Nutrients

34. Zooplankton Inedible Algae Edible Algae Nutrients 0

35. Field experiment (vary nutrients and fish)

36. Results: MicroflagellatesDaphnia

37. Data fit simple (not complex) model. Why?

38. Synthesize results of other nutrient experiments… Change in Density ZoopInedibleEdible Increase2078 No change 175 Decrease100

39. These systems contain different grazers.

40. Compare systems with Daphnia vs. smaller grazers (due to their size, they perceive “edibility” differently): vs.

41. Change in Density ZoopInedibleEdible Increase1012 No change 164 Decrease000 Change in Density ZoopInedibleEdible Increase1066 No change 011 Decrease100 Daphnia systems (all algae are “edible”) Systems with smaller cladocera (some algae are “inedible”)  heterogeneity key, but poorly resolved

42. Simple models have helped guide our understanding and have pointed to the role of additional biological features