Administrational note first

1. Administrational note first • Received from: Antoine, Alaa (El Chiekh Ali), Richard, Mireille, Angie. The rest? • All thus far: want quizzes, and one or two midterm exams • Remember: 12% of quizzes done; at least one exam (30%)28 • Not acceptable for evaluation: attendance, comments • Paper • Tell me: your hypothesis. Your timeline. Deadline: one week from today. • Project • Tell me: your hypothesis. Your methodology. Your timeline. Deadline: one week from today. • Final syllabus will be signed by both of us 

2. example • 12% - done (quizzes) • 30% - Final exam • 30% - research paper • 18% - 5 quizzes (3.6 % each) • 10% - homework • Total – 100%  • Research paper • Due in one week: Hypothesis & timeline • Hypothesis: Climate change will result in decreased productivity for olive trees in Lebanon • Methodology [how do you plan on answering your question? What readings? What sub questions?] – 5% - due…? • Draft: - 10% - due…? • Final: 15% - due…? Signed: student: _______________________ Prof: _______________________

3. Documentaries – must see • Thursday December 2nd, 12.30 to 2.00 pm: Microcosmos • Thursday December 9th, 12.30 to 2.00 pm: Food, Inc. • Location for both: Hariri Auditorium

4. Chapter 7: Predation, Grazing, and Disease (skipping Chapter 6)

5. Remember: True predator Grazer Parasites parasitoids

6. Prey fitness and abundance • Fundamental similarity between (true) predators, grazers, and parasites is…? • … each reduces either the fecundity or chances of survival of individual prey and may therefore reduce prey abundance. • Studied the Relative growth rates (changes in height) of a # of different clones of sand-dune willow – subjected to herbivory at different intensities, in 1990 and 1991. 1991: also drought -> greater mortality • Studied pied flycatcher

7. Prey fitness and abundance Proportion of males of male pied flycatchers infected amongst groups of migrants arriving in Finland at different times • Males that arrive earlier  more successful at finding mates • Later arrivals disproportionately infected with a blood parasite

8. Prey – Predator • Need to compare prey populations in the presence and absence of predators • Rely on observation and experiments (both artificial and natural experiments) • What is the impact of the Indian meal moth with and without a parasitoid wasp? – wasp reduced moth abundance to 1/10th

9. Prey-Predator • Predators can reduce prey abundance – as we have seen • But they do not necessarily reduce prey abundance • There are subtleties of predation – like what?

10. More than just: prey dies, predator reproduces • Interactions with other factors • Grazers and parasites (in particular)  make prey more vulnerable to other form of mortality • Interaction between competition and parasitism • Infection or grazing  more susceptible to predation • Red grouse: birds killed by predators in the spring and summer had more gut nematode parasite

11. More than just: prey dies, predator reproduces • Compensation and defense by individual prey • Individual plants can compensate in a variety of ways for the effects of herbivory • Remove leaves  other leaves have more sun  more photosynthesis • Herbivory attacks  plants use stored reserves – shifting root: shoot ratio • Or compensatory regrowth of defoliated plants when buds are stimulated to develop • Or plants can increase their production of defensive structures or chemicals

12. What is the cost/benefit? • Snails grazed on the brown seaweed for a few weeks  substantially increased [ ] of phlorotannins  reduced snail grazing. [clipping the plants did not have the same effect. Why?] End result: snails eat less. Plants have less eaten. At a cost. • Lifetime fitness of wild radish plants • Grazed by caterpillars  response induced protected plants from other herbivores; increased fitness > control • Leaf-damage controls [equivalent amount of biomass removed using scissors]  plants had 38% lower fitness than overall controls • Overall control [undamaged]

13. What about the populations – not just the individual • From individual prey to prey populations • General rule: predators are harmful to individual prey • What are the effects of predation on a population of prey?! • - not always so predictable • Impacted / influenced by food availability. • When food is tight, and competition is intense, predation may… • …relieve competitive pressures and allow individuals to survive who may not have been able to

14. True predators

15. How do predators forage? • We’ve talked a bit about what happens after a predator finds a prey • What happens to establish that contact? • Different types of foraging

16. Different types of foraging • Active predators seeking … Sit and wait predators • Direct parasite transmission • Transmission between free-living stages of a parasite shed by a host and new uninfected hosts

17. Foraging behavior • Where to eat? • How to balance risk of predation? • How long to remain in one location? • What about other competing predators? • And what to eat?

18. Optimal diet model • Optimal diet model: • Any predator will include the single most profitable type of prey in its diet [highest net rate of energy intake] – but then what? How to choose? • Predators with handling times that are typically short compared to their search times should be generalists (broad diet) • Predators with handling times are long relative to their search times should be specialist. • Other things being equal: predator should have a broader diet in an unproductive environment than in a productive environment

19. Predator-Prey interactions: a tendency to cycle Assume: large population of prey; lotka-volterra model

21. Factors Changing Equilibrium Isoclines • The prey isocline increases (r/c) if: • Reproductive rate of the prey (r) increases or capture efficiency of predators (c) decreases, or both: • the prey population would be able to support the burden of a larger predator population • The predator isocline (d/ac) increases if: • Death rate (d) increases and either reproductive efficiency of predators (a) or c decreases: • more prey would be required to support the predator population

22. Predator-prey cycles in practice

24. The Functional Response • A more realistic description of predator behavior incorporates alternative functional responses • type I response: rate of consumption per predator is proportional to prey density (no satiation) • type II response: number of prey consumed per predator increases rapidly, then plateaus with increasing prey density • type III response: like type II, except predator response to prey is depressed at low prey density (c) 2001 by W. H. Freeman and Company

26. Disease dynamics and cycles • Cycles are also apparent in dynamics of many parasites • Start with basic reproductive rate • Transmission threshold – for disease to spread: R0 > 1

27. Start 0 No predator lives alone • Predators are affected by other predators • Competitive  reduction in the consumption rate per individual as predator density increases • Mutual interference • Increased rate of emigration • Prey may hide more • Impacts: fecundity. Growth. Mortality. Of individual predators. Intensifies as predator density increases.

28. Crowding with prey too • Prey too are also subject to crowding • Prey crowding: prevents their abundance from reaching as high as level  impacts predator abundance • Damping effect on any predator-prey cycle. What does that mean?

29. Patches. • Metapopulations. Remember them? • Catch: differences between the patches tend to stabilize the interaction, to dampen any cycles that might exist. Why?

30. Predators and prey in patches • Predatory mite (Typhlodromus occidentalis) feeds on a herbivorous mite (Eotetranychus sexmaculatus) which feeds on oranges interspersed amongst rubber balls in a tray • Why? • To create ‘patches’ • First introduced a prey population with 20 females per tray, then introduced 2 female predators

31. Without its predator, the mites stabilized their pop • With the predator, the predator increased, killed all the prey, then died • Predator-prey dynamics were unstable • What about when patchy?

32. In each experimental tray, 4 oranges, half exposed, are distributed at random among the 40 positions in the tray. Other positions are occupied by rubber ball. Each orange is wrapped with paper and its edges sealed with wax. The exposed area has been divided into numbered sections to facilitate counting the mites. Then further modified to facilitate dispersal of prey and not predators

33. Each tray has 120 possible food positions Shading represents relative density of six-spotted mites at each position… …and dots indicate presence of predatory mites A spatial mosaic of habitats allows predators and prey to coexist

34. Predator-prey patches • Natural population example: • Starfish eat mussels • Mussels eat planktonic larvae • Planktonic larvae continuously colonizing new areas • Clumps of mussels that are heavily preyed upon – get dislodged by heavy seas – mussels die • End result: same mosaic

35. Take home message? • Predator-prey dynamics can take a wide variety of forms • We can understand this variety by seeing it as a reflection of the way in which different aspects of predator-prey interactions combine to play out variations of an underlying theme

36. Predation and community structure • Predator-mediated coexistence • When predation promotes the coexistence of species that might otherwise exclude one another • Eurasian pygmy owls – only on 4 islands • Five islands w/o predatory owl: 1 species (coal tit) • w/ owl: coal tit had two larger tit species (willow tit and crested tit) • Why? Coal tit is better competitor; but 2 larger species less affected by predation from owl; owl reduces the competitive dominance

37. Levels of predation • Zebu cattle: no-grazing control and 4 grazing intensities in sites in Ethiopia • More species occurred at intermediate levels of razing then where there was no grazing or heavier grazing • As a generalization: selective predation should favor an increase in species number in a community as long as the preferred prey are competitively dominant, although species numbers may also be low at very high predation pressures • balance

38. Quizzes – 4 left • December 1 – chapters 5 and 7 • December 10 or 15 • January 5 • January 19

39. homework http://www.eatinganimals.com/ “Animal agriculture makes a 40% greater contribution to global warming than all transportation in the world combined; it is the number one cause of climate change.”

40. Food…Homework • In one week (7 days), write down everything that you consume, including cigarettes, gum, etc. • Include as much locational-information about the product that you know • Be detailed. A “salad” is not enough. • Think about what you are eating • By December 7th • Give me your weekly diet • A one to two paragraph reflection on your eating habits • A one to two paragraph reflection on the relationship between what you eat and ecology