Exam 2 Answer Key. Name. Bio 368 Behavioral Ecology Dr. J. W. White Spring Total points: Multiple choice. Definitions. Short answer.

Transcription

1 Name Bio 368 Behavioral Ecology Dr. J. W. White Spring 2014 Answer Key Total points: Multiple choice /30 Definitions /10 Short answer /20 Long answer /10 Subtotal /70 Curve Bonus /4 Total /70 %

2 Part I - Multiple Choice: Answer ALL 15 questions. (2 pts each = 30 pts total) B 1) Organisms that can only distinguish hue, chroma, and brightness along a single color axis (e.g., blue-yellow) are termed a) monochromats b) dichromats c) trichromats d) tetrachromats A 2) This phenomenon partly explains why most long-distance sound communication utilizes lower-frequency, long-wavelength signals a) Rayleigh scattering b) Mie scattering c) Acoustic leakage d) Animals cannot efficiently produce wavelengths larger than their bodies C 3) Frogs use which of the following strategies to optimize the transmission of their calls through the air? a) Produce call while completely submerged in water b) Open mouth widely with flared lips c) Very thin throat membrane minimizes difference in density between frog & air d) Only call when air is warmer & thus higher density D 4) Broadside threat displays exemplify all of the following concepts except a) Tactical behavior b) Honest signal for conflict resolution c) Motivational conflict d) Eavesdropping B 5) Animals such as hummingbirds use thin-layer interference produces bright coloration when viewed from certain angles. What type of signal is this coloration likely to encode? a) territorial ownership b) courtship c) mate attraction d) food location signal p. 2

3 C 6) Ring-tailed lemurs are one of the few animals that uses odor in a threat display (a stink fight ). What is not a reason that olfaction is rarely used in that context? a) signal is slow to produce & diffuse b) signal has very low directionality c) signal can reveal individual identity d) signal is not easily changed to indicate level of aggression C 7) There should be selective pressure for conflict resolution badges to be honest indicators of fighting ability because a) cheaters will win too many interactions b) cheaters will attempt to conceal their false badges c) if cheaters are occasionally challenged, the cost of losing a fight is very high d) badges are not costly to produce E 8) Many animal signals are highly stereotyped. A potential explanation for this is a) due to errors in signal transmission, receivers can t distinguish subtle differences in signal quality, so there is no pressure to overacheive with a high-quality signal b) signal transmission has a high heritability and very low genetic variation c) receivers have narrow receptive windows, so stereotyped signals target that window precisely d) A & B e) A & C f) B & C B 9) Most animals that reproduce sexually are a) isogamous b) anisogamous c) homogamous d) protogamous p. 3

4 F 10) Female bicolor damselfish prefer to mate with males that perform a highly elaborate and energetic courtship dance, and that already have another female s eggs laid in his nest. Which of the following could explain the advantages accruing to the female from this mate choice? a) sexy sons b) good genes c) good resources d) A & B e) B & C f) A, B, & C C 11) Which of the following taxa always has female parental care but very rarely male parental care? a) fish b) amphibians c) mammals d) birds A 12) Fisher proposed the idea of runaway sexual selection. Which of these must be true for selection on a trait to follow that pattern? a) covariation in expression of the trait (in male offspring) and preference for the trait (in female offspring) b) physiological cost to produce the trait c) high genetic variability as a consequence of strong selection d) females have innate preference for traits not currently expressed in that species (e.g., platyfish prefer swordtails) A 13) In the (hypothetical) bananabird, parental care is sometimes performed by both parents and sometimes by the female only. Which of the following factors would make it more likely that the parent would stay to care for his offspring? a) low resource availability increases area the parents have to search to find food b) high population density increases the abundance of unmated females in the area c) male observes female obtaining EPCs with a neighbor d) male is young and small, and cannot bring food back to the nest as efficiently as the larger female parent p. 4

5 C 14) Which of the following is not a feature of lekking behavior? a) aggregation in hotspots that females are likely to traverse b) low male investment in parental care c) matings evenly distributed among displaying males d) highly stereotyped male displays B 15) Which of the following is not a potential benefit of EPC? a) obtain matings from higher-quality males while retaining parental care from the cuckolded partner b) coercing the cuckolded mate into providing better parental care c) obtain favorable treatment of offspring from multiple males d) obtain greater genetic diversity in offspring, ensuring better resistance against a spectrum of pathogens p. 5

6 Part II - Definitions: Provide a complete but concise definition in 1-2 sentences of ALL of the following terms. (2.5 pts each = 10 pts total). You may include a sketch if that helps you define the term. 1) Intention movement A signal of an animal s intent to perform a behavior that is linked or somehow preparatory for that behavior (i.e., it is not an arbitrary signal but is directly associated with the intended behavior). An example would be baring teeth to indicate aggression, prior to a biting attack. -Many lost point for suggesting that this was only related to aggression, or only related to teeth-baring 2) Pheromone An olfactory signal for intraspecific communication. - Many lost 1 point for suggesting that this was only related to mate attraction. 3) Parent-offspring conflict The conflict over the amount of resource provision by a parent to an offspring. Typically the optimal level of care from the parents perspective is lower than the optimal amount from the offspring s perspective, because a parent is only 50% related to each offspring, and marginal increases in provisioning to one offspring detract from investment in other potential offspring. Full credit required mentioning the idea that parents are trading off investment in one offspring vs. other offspring. If the offspring in question is the only offspring the parent will ever be able to produce, then there will be essentially no conflict because the parent only obtains fitness via that one offspring. 4) True communication Communication that benefits both the sender and receiver of a signal. p. 6

7 Part III - Short Answer: Answer ALL of the following questions. Please be as brief and concise as possible. (5 pts each = 20 pts total) 1) Two hypotheses to explain female preferences for elaborate (and honest) male ornamentations and displays are good genes and sexy sons. First, explain what each of these is and how they differ. Second, explain how you would distinguish between those hypotheses in a hypothetical species (i.e., what information would you need to obtain)? If there is selection for good genes, then females choose mates to ensure that their offspring receive genes that are associated with high condition, survival, etc. In this case the male displays are usually honest, handicapped signals of condition or ability. If there is selection for sexy sons, then females choose males with arbitrarily attractive ornamentation so that their own sons will be attractive to potential mates. There are a few ways to distinguish these options. First, if good genes is operating, then both male and female offspring of a high-quality-display male should exhibit higher survival, fitness, etc. If sexy sons is operating, then offspring should exhibit covariation for the gene for preference for the sexy trait: sons of sexy males should exhibit the sexy trait, and daughters should exhibit a preference for that trait. Testing for trait covariation to rule out sexy sons is the key here, because simply following the fitness of both sexes may not be determinative if sexy sons is operating, then female offspring will also have high fitness because they will prefer to mate with the popular sexy males. One common point of confusion was to conflate good genes with good resources. It is true that if there is female selection for good resources, preferred males will typically also have good genes. However, good genes can operate even in mating systems in which males do not provide any resources to the female, so the answer had to address good genes on its own. 2) What is the dear enemy effect? Explain how territorial interactions differ between neighbors and floaters, and why owners usually win. The dear enemy effect is the phenomenon in which neighboring territory holders are less aggressive to one another than they are to floaters or intruders who do not own a territory. This effect arises because of the asymmetry in territorial interactions. When an owner interacts with a non-owner intruder, the owner has much to lose but the intruder has virtually nothing to lose, so the owner is usually willing to fight longer and harder and will win. When two neighboring owners interact, each one already has a territory and has little to gain from obtaining more territory, thus increasing defense costs. Therefore they prefer to de-escalate quickly to avoid a fight that neither wants. p. 7

8 3) Many animals exhibit tempature-depended sex determination. Explain what this is, and why it might be adaptive. TSD is the phenomenon in which sex is determined by the environmental temperature during embryonic or early juvenile development. This is adaptive in situations in which the sexes differ in their performance during different seasons, or when it is advantageous for one sex to begin development sooner and thus be larger during the first mating season. This could also be a means for mothers to adjust the sex ratio of their offspring to reflect social dynamics or her relative ability to provision for male or female offspring. 4) There is selective pressure on bird parents to identify and remove brood parasites from their nest. This requires discriminating between the parasite and their own offspring. Consider a hypothetical brood parasite that has distinctive reddish coloration on its wings, unlike the chicks of most host species. Sketch likely ROC curves for the discrimination of brood parasite chicks by host parents in two environments: 1) host nest is in an open, brightly lit meadow, and 2) host nest is in the lower canopy of a deciduous forest. In which situation do you expect host parents to exhibit more eviction behavior, and why? Full credit required actually drawing proper ROC curves, identifying which one was appropriate for each scenario, and labeling the axes (!). The meadow would have a very steep, convex ROC curve because the sunnier environment allows better discrimination of reddish wavelengths. The forest subcanopy would be a very green place, so very few red wavelengths are available and it would be difficult to see the reddish coloration. This would lead to a very shallow ROC curve that is close to the 1:1 line. Most points were lost for drawing figures that did not resemble ROC curves and for failing to label axes. p. 8

9 PART IV Longer Answer (10 pts) The bluebanded goby, Lythrypnus dalli, exhibits an unusual form of sex allocation. These small territorial fish live on rocky reefs off the coast of southern California. Males defend mating loosely defined mating territories basically the largest male in an area mates with all of the females and harrasses smaller males to prevent them from mating. When they mate, females lay eggs in a nest that the male defends (he can defend the eggs of multiple females from his territory in a single nest). These fish are extremely site-attached (i.e., they don t move around much, and females don t really move between male territories), and quite short lived (on average < 1 year) so the number of females in a male s territory might fluctuate considerably depending on whether many new juveniles have arrived recently or if there was a recent storm that killed several fish. A) Most bluebanded gobies begin life as females then change sex to become males. What is the name of this life history strategy? Protogyny Hermaphroditism got some credit but is a less specific term. B) The currently accepted explanation for the life history strategy named in (A) is the size-advantage hypothesis. Explain what this is and how it explains the behavior of bluebanded gobies. The SAH posits that in certain social systems, the sex with the highest fitness payoffs changes as a fish grows in size. In a mating system where large territorial males dominate all matings, small males will have little mating success (can t defend a territory), so small individuals are all female (matings are ensured), and they only switch to being male when they are large enough to defend a territory. C) A small fraction of gobies begin life as males instead of females. Why might this be advantageous for those males? A small fraction of males could obtain matings as sneaker or streaker males, although only if the frequency of those strategies remains low. D) What makes bluebanded gobies really unusual is that they are techinically simultaneous hermaphrodites. Even after they change from female to male, they retain some ovarian tissue in their gonads, and they can change back to being a female. Based on the description of their ecology given above, why might a large territorial male find it advantageous to change back into a female? p. 9

10 They are short-lived and highly site-attached. So if all the females in a male s territory suddenly die, it could pay to be able to switch back to female and obtain matings from a neighboring male. This is because it may take too long (relative to the fish s lifespan) to wait for new females to arrive. Some of you also suggested that this could be adaptive if larger males invaded the territory and excluded the resident male from matings; however given what we have discussed about territory holding and the tenacity of territory owners, this kind of usurpation seems unlikely. PART VI: Bonus! (4 pts total) 1) Name a protandrous bird species. This question should have been polyandrous not protandrous oops! I gave an extra point on the curve to account for that. 2) How do St. Peter s fish care for their young? Mouth brooding. 3) What type of color vision do dogs have? Dichromatic 4) On Tuesday, a team of researchers from the BICEP2 experiment in Antarctica revealed observational data supporting what scientific theory? The inflationary big bang theory. p. 10