Behavioral Ecology at Texas A&M University wfsc.tamu.edu/jpackard/wfsc622.html WFSC 622 Study Guide Tips Department of Wildlife & Fisheries Sciences UNIT 4. PREDATORS VS. PREY: EVOLUTIONARY ARMS RACES _______________________________________________________________________ CONTENTS 1. Reading Tips 2. Instructor's Commentary 3. Study Questions for Quiz 4 ____________________________________________________________________________________________________ READING TIPS Part 1 Adaptation or story-telling? Although the three questions for this chapter are posed in the first two pages, I found it difficult to distinguish from the headings when the topic shifts from the first to second and third questions. This whole chapter is really pretty good. In my opinion, pages 84-85 are the only ones that could be skimmed without loss of meaning. Part 2 How can an arms race begin? If the question "how do arms races begin" is more than just rhetorical, I'm guessing the relevant material starts on pg. 86. The examples provided are classics, appearing in most textbooks. Part 3 How do arms races end? The question of why "arms races" don't end in extinction is addressed, beginning on page 92. The emphasis shifts abruptly from predator/prey coevolution to parasite/host coevolution. Its still addressing issues of co-evolution. INSTRUCTOR’S COMMENTARY Part 1- Adaptation or story-telling? The three questions raised in the introduction are good, but it is hard to follow them throughout the chapter. This is why I used these questions as the subtitles for each of the 3 parts of the lecture outline. The issue of "adaptationist storytelling" is often difficult to understand for our students who have not had reason to read up on evolutionary theory. If you google "adaptationist storytelling" you will find a number of useful websites. If you want to learn more, a good place to start is Wikipedia. Search for the keyword "adaptationism" and follow the links to the scientists Richard Lewontin and Stephen J. Gould. Some of their articles are on course reserve linked to the library page. Part 2- How can an arms race begin? The answer to the question "how do arms races begin" could be made more explicit in this chapter. It is there, but pretty implicit. I like the analogy, because it makes us think of how we take our personal experiences as humans and project them onto animals. What an elaborate example of anthropomorphizing! Usually our students in the Military Sustainability Program can relate to this analogy. This is the simplistic way I think about the arms race. First the Indians had bows and arrows. Then the revolver and rifle arrived. The Indians bartered for firearms. Then somebody invented the machine gun. Armored tanks increased. Then the IED proliferated. This is an example of co-evolution in the sense of engineering design. The analogy is different than co-evolution between predator and prey species, because firearms are designed by people, and when we speak about biological co-evolution, the "design plans" are in the DNA of the organisms. In biology, a change in the trait of the prey species "exerts selection pressure" on the predatory species. Subsequently, a change in the trait of the predator species may result in differential reproduction/survival of genotypes within the gene pool of the prey species. It is more of a step by step process, where the predator is part of the environment of the prey and vice versa. As we learned in Unit 2, many behaviors are adaptations to a changing environment. Unit 4 Study Guide Tips Page 1 of 2 Behavioral Ecology at Texas A&M University wfsc.tamu.edu/jpackard/wfsc622.html WFSC 622 Study Guide Tips Department of Wildlife & Fisheries Sciences Part 3- How do arms races end? There is an imbalance in this chapter. The question of arms races starts with predator/prey, then slides into parasite/host without much explanation. It would be better titled "coevolution" rather than "predator/prey". It mainly includes the literature on predator/prey coevolution in birds and insects. The bird examples follow well from the previous chapter, but I'd like to see more information on mammals. However, the topic makes us think about how there are periods during evolutionary history when conditions are relatively stable and other periods when there are rapid changes. S.J. Gould writes about this in terms of "punctuated equilibrium". That is the idea that "natural selection" cruises along for a long time with only the accumulation of minor mutations within gene pools. This is the period when it looks like the "arms race" has come to a halt. Then something extreme happens, like a massive volcano or a meteor slamming into earth. The "truce" between predator and prey is disrupted and the co-evolutionary "arms race" starts up again. If the predator evolves faster than the prey, the arms race may end with extinction of the prey! STUDY QUESTIONS Part 1 Adaptation or story-telling? 1.1 Describe two hypotheses about the function of an anti-predator adaptation of an insect, which is explained by coevolution of predator and prey? (TIP: e.g. fore and hind wings of Catacola moth) 1.2 How was an hypothesis about the function of crypsis tested for a species of your choice? (TIP: e.g. Catacola moth) 1.3 How was an hypothesis about the anti-predator function of bright coloration tested in a species of your choice? (TIP: e.g. Catacola moth) 1.4 Describe the co-evolutionary steps in which a predator's foraging behavior "set the stage" for counter-adaptation of its prey? (TIP: e.g. birds and insects) 1.5 What distinguishes myth from science in explanations of why there appears to be such a nice match between adaptations of prey and their predators? Part 2 How can an arms race begin? 2.1 How was an hypothesis about initial steps in the evolution of a cryptic trait used as a basis for testing a model of foraging behavior for a species of your choice? (TIP: e.g. lab study of cryptic prey) 2.2 For "warning coloration", explain how an hypothesis about function was used to design and test a model about mechanisms of foraging behavior? (TIP: experimental manipulation of prey color and reward) 2.3 What is an example of heritable polymorphism in a population, related to an anti-predator adaption? (TIP: e.g. guppies) 2.4 How did Endler test the functional trade-offs between crypsis and warning coloration by examining polymorphism in a species? (TIP: Fig. 4.9 in KD'93) 2.5 How do predator/prey "arms races" get started? Part 3 How do arms races end? 3.1 Compare similarities and differences in brood parasitism behavior, between two species of your choice? (TIP: e.g. cowbirds and cuckoos). 3.2. For two species where the parasite/host "arms race" has ended, what is the evidence of coevolution of behavioral traits? (TIP: cuckoo) 3.3. Compare two brood parasites, one that shows evidence of a continuing "arms race" and one where there appears to be evolutionary equilibrium? (TIP: e.g. cowbird and cuckoo) 3.4 How does co-evolution end...or does it? Summary 4.1 What were 3 take-home messages re. coevolution of predator/prey (or parasite/host) behavior? 4.2 Why is predator/prey coevolution analogous to an "Arms Race"? Unit 4 Study Guide Tips Page 2 of 2 .