Supplementary Material for Chapter 14 Ants, Elephants, and Experimental Design: Understanding Science and Examining Connections between Species Interactions and Ecosystem Processes This chapter is published as: Stracey CM Ants, Elephants, and Experimental Design: Understanding Science and Examining Connections between Species Interactions and Ecosystem Processes. In: Byrne L (ed) Learner-Centered Teaching Activities for Environmental and Sustainability Studies. Springer, New York. DOI / _14 Christine M. Stracey Department of Biology, Guilford College, Greensboro, NC USA This file contains the following supplementary material: –A: Experimental design components and questions … beginning on slide #2 –B: Presentation slides … beginning on slide #3 This chapter also has the following supplementary material, available on the chapter’s website: –C: Instructor script –D: Student worksheet

Supplementary Material A : Experimental design components and questions Table 1: Key components of experimental design and questions to help students understand each component that could be used as a review prior to the start of the activity. move to a supplementary file. ComponentAnswer the following: Research Question What biological question were the researchers investigating with this study? Hypothesis What did the researchers think was going to happen? Dependent Variable What is the “response variable” in the experiment? What did the researchers measure in response to the independent variable? Independent Variable What variable(s) did the researchers manipulate or designate? Experimental Treatment For a manipulative study, which group did the researcher apply the treatment to? Control Treatment What is the “reference” group that the results from the experimental treatment are compared to? Standardization What steps did the researchers take to ensure that no additional factors influence the outcome of the experiment? Try to avoid using the word ‘control’ in this context (e.g. the researchers controlled for temperature) and only use control in the context of the control treatment to avoid confusion. Replication How did the researcher make sure that the experimental and control treatments were applied to multiple independent units? Result What did the researchers measure (in terms of how the dependent variable responded) as the outcome of the experiment? Inference What is the biological meaning of the results in relation to the hypothesis?

Supplementary Material B: Presentation slides These slides accompany the video abstract of: Goheen and Palmer Defensive plant-ants stabilize megaherbivore-driven landscape change in an African savanna. Current Biology 20:

1.What characteristics define these savanna ecosystems? 2.What effects does the relative abundance of trees/grasses have on ecosystem properties?

3. What type of “special species” are elephants in this ecosystem? Why? 4. Identify the important interspecific interactions in this ecosystem.

5. What observation started this research? 6. What was their hypothesis to explain this pattern? 7. What research question did the feeding trial address? 8. Outline their methods and identify the following components of their experimental design: dependent variable independent variable experimental treatment control treatment standardization replication

AD usually has ants AM doesn’t have ants AD, no ants AD, ants AM, no ants AM, ants Figure 5. Free-Choice Feeding Trials with Elephants and Acacia spp. Best-fitting Cox regression models as a function of food type: control A. drepanolobium (black triangles), ant-removal A. drepanolobium (black circles), control A. mellifera (red circles), ant-addition A. mellifera (red triangles). Solid and dashed thin lines represent 95% confidence intervals for probability of use of branches with and without ants, respectively. Elephants preferred branches without ants (b = 3.61, p < 0.01) but did not distinguish between tree species (b = 0.33, p = 0.57). The points in the graph are fitted from the model. 9. What does this graph show?

10. Why weren’t they satisfied with just doing experiment 1? 11. What did they do for this experiment? Be sure to identify the following in your answer: dependent variable independent variable experimental treatment control treatment standardization replication

Figure 4. Responses of Elephant Browsing to In Situ Ant Removal from Trees The number of A. drepanolobium (AD)branches browsed by elephants as a function of ant activity levels on trees from the ant-removal experiment (χ 2 1 = 28.41, p < 0.01). 12. What should their results look like if their hypothesis is correct?

Figure 4. Responses of Elephant Browsing to In Situ Ant Removal from Trees The number of A. drepanolobium branches browsed by elephants as a function of ant activity levels on trees from the ant-removal experiment (χ 2 1 = 28.41, p < 0.01). 13. What did their results show?

14. Now that they’ve shown that elephants avoid acacias with ants in the wild – what next? In other words, have the researchers convinced you that whether an area is a grassland or a woodland is determined by the presence of ants?

15. What was the experimental design for the ecosystem scale study? This is a complicated study and so it might help to answer these individual questions first: What is the difference between sandy soil and clayey soil? What are exclosures? If the presence of ants determines the amount of trees in an ecosystem and ants are NOT present, then what do you predict the effect of an exclosure will be on the amount of tree cover over time inside versus outside of an exclosure? If the presence of ants determines the amount of trees in an ecosystem and ants are present, then what do you predict the effect of an exclosure will be on the amount of tree cover over time inside versus outside of an exclosure? Relate your previous two answers to the type sandy and clayey soils. What do you predict will happen to tree cover inside and outside exclosures on sandy versus clayey soils?

16. Now that you have figured out the rationale for this study, identify the following: dependent variable independent variable standardization replication

Clayey Sandy 17. What do the satellite images show? Is this consistent with your predictions?

Figure 2. Landscape Change on Lewa Downs Conservancy and Mpala Change in tree cover in elephant exclusions (black bars) and paired controls (white bars), 2003–2008. Virtually all trees on sandy soil are nonmyrmecophytes; w 95% of trees on clayey soil are the myrmecophyte A. drepanolobium. Means (95% confidence intervals) from sandy soil represent averages across four exclusion plots and their paired controls from Lewa. Means from clayey soil represent averages across six exclusion plots and their paired controls at KLEE and two exclusion plots and their paired controls at Lewa. Letters associated with bars represent statistically significant differences between groups (p < 0.05). (ants rare) (ants common) 18. Now let’s examine the quantitative data. What do these results tell you?

Summary Questions 19. What do these results collectively tell you about the original question and hypothesis? What were the strengths and weaknesses of each individual study? 20. Discuss the role that ants, acacia, and elephants have on ecosystem processes. How does this differ from how people typically think about ecosystem processes? 21. What effects could illegal poaching of elephants have on this ecosystem? 22. How is the biodiversity of this region affected by the presence of ants and by the presence of elephants?