Download Week 12

Biology 156
Evolutionary Ecology
2 Apr 2001
Bob Podolsky
Week 12. Coevolution
Study guide
After the module on coevolution, you should be able to:
Lecture 12.1. Specificity in mutualisms:
1. Explain why Darwin claimed that "natural selection cannot produce a structure in one
organism that is exclusively for the good of another species."
2. Distinguish between the concepts of "diffuse" and "pairwise" coevolution, and give
hypothetical examples of each.
3. Give an argument for whether or not Seeley's crab/snail interaction is likely to lead to a
coevolutionary relationship.
4. Provide an argument for why there are relatively few examples of specific coevolution
between species pairs
5. Describe the initial observations concerning ant/plant interactions that led Davidson et al. to
examine costs and benefits to the two types of interactors
6. Describe the experiments and controls that Davidson et al. used to distinguish between two
hypotheses for the evolution of "pruning" behavior by ant species
7. Describe a particular observation suggesting that pruning was likely driven by selfish
interests of ants
8. Explain the results of a survey of ant/plant associations which supported experimental
observations of the consequences of pruning
9. Describe the basic life cycle and interaction between yucca plants and a pollinating species of
yucca moth
10. Explain the basic reproductive tradeoff that demonstrates a conflict of interest between the
two mutualists
11. Explain why intermediate levels of moth oviposition are best for the plant, but not best for
the moth
12. Explain Pellmyr and Huth's hypothesis for how the plant appears to exert selection on the
moth to maintain intermediate levels of oviposition
13. Describe their experimental results suggesting that plants must have some way of detecting
the degree of moth oviposition
14. Explain why their data rule out the hypothesis that seed destruction leads to selective fruit
abortion
15. Explain what their phylogenetic data across groups of pollinating moths suggest about the
number of times mutualism (active pollination) has evolved
16. Explain how detailed phylogenetic data are consistent with the idea that mutualism and
parasitism may be in a dynamic flux
Lecture 12.2. Evolution of virulence, cospeciation
17. Describe the original conditions of the experiment by Jeon with amoebae and bacteria
18. Explain details of experiments they used to examine responses of host and symbiont to one
another after several years of association
19. Use their experimental results, or similar hypothetical results, to support or refute the
hypothesis that coevolution had occurred between the symbionts
20. Explain why their conclusions are relevant to the evolution of endosymbiosis
21. Describe the basic life cycle of the fig wasp in relation to the development of fig syconia
22. Give a definition of virulence and explain whether it is a property of the host or the parasite
23. Explain the likely causal relationship between reproductive rate of the parasite and virulence
24. Explain why the mechanism underlying virulence sets up a tradeoff between parasite
replication and transmission to new hosts
25. Describe the difference between horizontal and vertical transmission of the parasite, and why
these two modes would influence the evolution of virulence
26. Explain Herre's prediction concerning the evolution of virulence in nematode parasites of fig
wasps, and the relationship of virulence to the ecological conditions of foundress number
27. Describe the nature of the data collected by Herre and whether they supported his predictions
28. Evaluate the statement that parasitism always evolves to more and more benign states
29. Give a definition of cospeciation, and describe its relationship to coevolution
30. Recognize phylogenetic patterns that are consistent with a process of co-speciation, and those
that are not
31. Give the basic biology of the leaf-cutter ant/fungus association, and why species were
predicted to show patterns of cospeciation
32. Describe the results of Hinkle et al., and explain why they support a pattern of cospeciation
between ants and fungi
33. Point out patterns in the data of Chapela et al. which indicate that some species of formerly
cultivated fungi have "escaped" cultivation by ants, while other species of formerly freeliving fungi have apparently been newly captured and cultivated by formerly unassociated
ant species