Study questions for final exam. Note that for brevity here, I’m not including natural history details from papers and examples we discussed in class.  Such details would be included in the exam.

A. Communication.

1. It is often argued that signaling can only evolve when it is beneficial to the sender.

a. Use cost/benefit analysis to explain this assumption.

b. Does the same assumption hold for the receiver of the signal? Use a biological example to support your argument.

2. Separation of proximal and ultimate mechanisms is necessary to understand why some organisms respond to signals that may not be beneficial to them.  Using the example of “femme fetale” fireflies, distinguish proximal and ultimate mechanisms for male behavior. Use a cost-benefit analysis to explain why males have not evolved to avoid “femme fetale” females.

3. We discussed the “hawk-dove” dichotomy to introduce evolutionary stable strategies (ESS).

a. In your own words, explain why neither strategy is stable over evolutionary time.

b. What is the relevance of to our understanding of “honesty” in signaling within a species? Does “honesty” of signal apply to interspecific interactions?

c. Within species, “exploitation” is argued to refer to the order of evolution of signal and response, not to the fitness benefits of sender and receiver.  Do you agree? Support your answer.

4. In the text, and in class, it was proposed that rather than view the evolution of signaling as “information exchange”, it is better to think of signaling as “manipulation”. What circumstances (biological examples) are easier to understand with this definition?

5. Dr. Cahan argued that male spiders exploit sensory biases in females, and used the differences in courtship between web-building spiders and jumping spiders as examples. How do these courtship behaviors differ, and are those differences indeed correlated with sensory biases in the females? What is the source of the sensory biases?

B. Sexual selection.

1. Fisher argued that in order for exaggerated male secondary sexual characteristics to evolve, these must be associated with adaptive male attributes.  However, it has also been argued that in the case of supernormal stimuli (such as a female platyfish preferring a male with a sword tail), this link is not necessary. Explain this apparent connundrum. (hint:  consider proximate and ultimate mechanisms).

2. Why, a priori, do we expect males to be more reproductively active than females? Why do shifts in the operational sex ration (male biased versus female biased) influence male and female sexual selection?

3. We discussed a paper about sexual choosiness in an Australian pollen-feeding katidid.  In this species, males produce spermatophores that include a high resource investment. Females eat the spermatophore (but not the sperm), and have increased reproductive output. Researchers noticed that in the early spring, when pollen quantities were low, males were choosey and females courted males.  In late spring, when pollen quantitites were high, females were choosey and males courted females.

a.  Make predictions about the operational sex ratio that could explain the shift in male and female behavior.

b.  Derive two alternative hypotheses that could be the mechanism for the changes in operational sex ratio. (use two different driving forces, not a “null hypothesis” as the alternative)

c.  Develop an experimental procedure that would allow you to simultaneously test both hypotheses.

4.  Increased choosiness by females is hypothesized to result in fitness benefits.

a.  distinguish between “phenotypic” and “genetic” benefits of female choosiness. Which was demonstrated by late-spring behavior in the katidids?

b.  We discussed a paper about an arctiid moth, where both phenotypic and genetic benefits of female choosiness were explored.

 -- how did they demonstrate “phenotypic” benefits?

-- how did they demonstrate “genetic” benefits

-- do you feel that the experiment adequately distinguished between these two benefit types? Why or why not?

5.  What is “male-female” conflict, and under what circumstances might it occur?

C.  Mating systems

1.  Be sure you are comfortable with the terms “polyandry” and “polygyny”. What is the difference between “social” and “genetic” monogamy? How can the two be distinguished?

2.  After many years of arguing (as in the sexual selection arguments, above) that females should be choosy and males should mate as many different females as possible, recent information indicates that many presumed “monogamous” species are polyandrous. What are these new data, and how might they influence our understanding of the evolution of male secondary sexual characteristics?

3.  There are many alternative hypotheses for polyandry (page 370 in the text book).  How is the “sexy son” (good genes) hypothesis potentially confounded by biased female investment?  Use the moth example (B4, above) to discuss the difficulty of making this distinction.

4.  We also discussed a paper using pseudoscorpions. Fertility insurance and genetic compatibility are two hypotheses that were two alternative hypotheses they tested. Discuss the rejection of the following alternative hypotheses; note that some of them are rejected based upon knowledge of the natural history of the species, and some are rejected because the experimental design eliminated them as a possibility.

a.  On what basis do the authors rule out all phenotypic benefits (material benefits) of polyandry in this species?

b.  On what basis do the authors rule out the “trading up” or good genes hypothesis of polyandry?

c.  On what basis do the authors the “fertility insurance” hypothesis of polyandry?

5.  In the text book, on page 367, two traits are mapped onto prosimian primate phylogeny:  mother-infant association and male-female association. In contrast, we discussed a paper by Komers & Brotherton concerning monogamy in all mammals, in which figure 1 provides a similar phylogeny with the mapping of mating system and paternal care. In the first phylogeny, there is a close correlation of the two behavioral traits but in the second there is little correlation.

a.  What hypothesis concerning maternal care and male female association is tested in the analysis presented in the text book? Is male-female association necessarily the same as social or genetic monogamy?

b.  What hypothesis concerning paternal care and monogamy is tested in the analysis presented in Komers & Brotherton?

c.  Komers & Brotherton did a lot of their analysis using extracted pair-wise comparisons of sister groups. What is a sister group, and why is this a particularly strong mechanism for testing evolutionary hypotheses of behavior?

c.  What unexpected (to me at least) hypothesis survived the phylogenetic analysis presented in Komers & Brotherton? Can you provide a cost/benefit explanation for this hypothesis?

D.  Parental care.

1.  The text book makes extensive use of “cost/benefit” analysis for the evolution of parental care. How is “lost opportunity” a cost of parental care, and which sex might be expected to more often incur this cost? How is this analogous to the “lost opportunity” we modeled in prey selection? How is “lost opportunity” measured in foraging compared to reproductive behavior?

2.  In midshipman fish, beta or secondary males are “sneakers” into nests where alpha or primary males court females and care for eggs, where the sneakers attempt to fertilize some eggs.

a.  Why, in this species, are the males the primary care-providers, not the females? (hint: use the cost/benefit analyses from other fish to structure your answer).

b.  How might alpha male behavior change as the frequency of successful “sneaker males” increases in the population? Why?

c.  In these fish, as in many others, parental care is a fixed trait. Discuss what this means, and why it makes phylogenetic comparisons necessary in order to test hypotheses about the evolution of parental care.

3.  In most insects, the extent of parental care consists of provisioning of the egg with yolk and oviposition upon a suitable host or substrate.

a.  What physiological processes appear to have driven the evolution of more elaborate parental care in the belostomatid bugs?

b.  Consider the phylogeny presented on page 401 of the text. What mapping of female resource or time requirements for maturation of an egg clutch would cause you to reject the hypothesis "paternal care evolved because of egg size ”?

c.  How would you expect male versus female “lost opportunity” to differ within the belostomatid species? How might male “lost opportunity” differ between the belostomatid bugs and the water striders (Ranatrinae)?

d.  What would you expect the operational sex ratio to be in the belostomatid bugs (i.e., male biased or female biased)? Who should be courting whom?

4. Imagine that, in a particular nest-building belostomatid species, parental care could be provided either by the male or the female.

a.  How might cost/benefits play a role in determining which parent provides care?

b.  How might operational sex ratio play a role?

c.  If it is possible to distinguish them, design an experiment that would test the relative importance of OSR and cost/benefits of parental care in determining which sex provides parental care.

5.  Drummond and his co-authors compared siblicide and junior chick behavior in two booby species, an obligate (brown) and a facultatively siblicidal (blue).

a.  What appears to drive siblicide in each of these two bird species?

b.  The two species inhabit the same islands in the sea of Cortez. How does this common ecology influence your understanding of the behavioral differences?

c.  There are two hypotheses concerning siblicide: the runt hypothesis (the senior chick is in control) and the desperado chick hypothesis (the senior chick could loose). The former hypothesis is the one most often presented; what observational data from obligate siblicidal species calls this hypothesis into question?

d.   Drummond et al. observed a very wide range of behavior in the foster brown booby chicks.  What factors do they present as possible explanations? Develop an experiment with two treatment groups that could allow you to test one of these explanations.

6. Considering junior chick behavior in blue-footed boobies, choose one behavior and describe it alternately as an “event” and a “state”.

a. Develop a testable hypothesis for each.

b. For each hypothesis described above, determine whether you should measure it as a “rate”, “conditional probability” or “time allocation”.

c. Choose the best sampling scheme (focal individual or scanning) for each hypothesis given the “event” or “state” definition you used. Briefly explain why the sampling scheme is appropriate

Highlights from prior exams for review:

section I: basic behavioral concepts and experimental design.

A. Animal behavior as a scientific discipline.

1. “Non-adaptive” models are important null-hypotheses in evolutionary ecology. Briefly describe what is meant by “non-adaptative model”, and provide an example (you do not need to use the biology of the midshipman fish as the source of your example). Explain why your example is a non-adaptive model.

2. Under what circumstances can we state that a hypothesis is “strongly supported”? Why is a study designed to test multiple alternative viable hypotheses stronger than a study testing a single hypothesis and the null hypothesis?

3. Mike Ryan has found that there are two populations of cricket frogs on the Louisiana – Texas border. The males in the eastern population sing a distinct song from the males in the western population. In controlled play-back experiments in a sound-proof laboratory setting, females from each population strongly prefer the songs of males from that population. In further neuro-anatomical studies, Ryan and his colleagues have shown that the females of each population are physiologically incapable of hearing the songs of the other population (i.e., the ear does not respond to the song).

a. Define the term “genetic constraint”.

b. Does female cricket frog behavior suggest the presence of genetic constraint?

4. We read a paper by Swallow, Carter & Garland describing an artifical selection experiment testing for the evolution of wheel-running behavior.

a. What is artificial selection, and why is this a particularly important tool for studying the evolution of behavior?

b. What two things must be true for this artificial selection program to succeed? (hint: recall the three requirements for evolution through natural selection to proceed)

c. In addition to selecting for two behaviors, what additional treatment should be included in the experiment? Why?

5. Imagine you can do a breeding experiment using midshipman fish. Using offspring produced with the following crosses, design subsequent treatments that would enable you to test for genetic (G), environmental (E), and genetic variation in environmental responses (G x E) in determining male phenotype.  (Assume you cannot know the “phenotype” of the females.) Note – this question can be reframed for foraging, parental behavior, habitat selection or many other subjects where both genes and environment play a potential role, and you should anticipate that I will reuse it in one of those other contexts.

cross #1: 1° male x female

cross #2: 2° male x female

experimental treatment(s):

6. For each of the possible mechanisms (G, E, G x E), choose one pair of offspring groups (by genotype and/or treatment, from your protocol above) that you would expect to be different if that mechanism is operating. Describe how they would differ.

a. significant Genetic effects on male phenotype:

b. significant Environmental effects on male phenotype:

c. significant G x E effects on male phenotype:

Section II: Behavioral ecology of the individual

1. Fitness has two primary components: survival and reproductive success. What component(s) of fitness were emphasized in this particular section of the class? We distinguished “relative” and “absolute” fitness. Which is more appropriate for study of evolution of behavior within a population?

2. In this course, we spent a lot of time discussing “cost/benefit” analyses of behavior. “Lost opportunity” plays a role in prey selection models, and in parental care models. In foraging models, the frequency of high-value prey plays a major role in determining “lost opportunity”, and in parental care models the operational sex ratio plays a major role in determining “lost opportunity”. Discuss “lost opportunity” in both of these circumstances, using one or two biological systems as examples.

a. Why is the role of OSR in determining parental care more difficult to examine experimentally than the role of abundance of high-value prey in foraging behavior?

b. What does this imply about the ecological, evolutionary and genetic constraints that might be imposed in foraging compared to reproductive behavior?

c. Where would you expect to find a greater reliance on comparative studies for understanding the evolution of behavior, in reproductive behavior or in foraging behavior? Why?

3. Dragonflies, while highly territorial in breeding areas, are not at all territorial when foraging. We discussed three main questions concerning territoriality: benefits of holding a territory, costs of holding a territory, and size of territory. Considering likely frequency of intruders, resource predictability, and resource density, answer the following questions.

a. How do the two types of resources, female oviposition sites and flying insects, differ in costs of holding a territory?

b. How do the two types of resources differ in benefits of holding a territory?

c. Based upon your answers to parts (a) and (b), does it seem logical that territoriality is only expressed in breeding areas not in foraging areas?

Explain your answer

4. Habitat selection by individuals in a particular species is one area where the proximal mechanisms and the ultimate mechanisms are very distinct.

a. Choose one organism we have discussed, and develop one hypothesis concerning a proximal mechanism of habitat choice.

b. Develop one hypothesis concerning an ultimate mechanism of habitat choice.

c. The proximate mechanism(s) for habitat choice could be either learned (“environmental”) or genetic. Are there circumstances under which you might expect one or the other to be more likely?

d. What kind of experiment could distinguish learned from genetic?

e. Assuming that habitat selection is genetically determined, how could you determine whether it was fixed or variable? If it is variable, how is this distinct from learned?