The Impact of Paternal Uncertainty on Male Parental Care

1. In Experiment 1, researchers placed two glass containers containing small cuckold males around each nest and left them there during egglaying. The cuckold males couldn’t fertilize the eggs, but they could be seen by the male at the nest. How much did the presence of cuckold males reduce egg guarding? How much did it alter offspring guarding? Why was there a difference? The presence of cuckold males reduced the egg guarding from a score of 80± 10 to 57±7 which is a significant amount. However, when it came to the score for offspring guarding, the results did not change much at all. It went from 90±10 to 95±10 which is considered unchanged as the scores were practically the same with or without the presence of a cuckold for the hatching offspring. The significant difference in egg guarding existed because the presence of the cuckold males reduced the paternity certainty of the nest owners thus, nest owners felt less inclines to guard the egg. When it came to the offspring guarding, there wasn’t much of a change because after the offsprings hatched, the next owners became certain of the fact that the eggs were their genetic offsprings. ! 2. Considering Experiments 1 and 2 together, what conclusions can you draw from these results? Why? (Refer to specific results in your answer.) In each of the two experiments, males had lower egg-guarding scores relative to males in the control group when given signs that the offspring were less likely to be descendants of their own genes. The evidence given allows us to conclude that the genetic relatedness to offspring plays an important role in parental care of bluegill sunfish. ! 3. According to the principles of inclusive fitness, should the dominant male prefer a simple pair or a trio? (Assume that each male within a trio sires half the surviving young.) Does it matter whether the second male in the trio is related to the dominant male? Inclusive fitness is a sum of an individual’s indirect and direct fitness. According to this concept, the dominant male should prefer a trio because it is most likely that both the males are brothers. This means that they both share genes and if passing on the most of the family’s gene is primality important, then he would want to pass down his genes (direct fitness) as well help his brother pass down genes too (indirect fitness). This would allow for a greater number of offspring with half of their genes. In saying this, it does matter whether the second male in the trio is related to the dominant because if he wasn’t related, then the dominant male would be more likely to prefer a simple pair and use his dominance to prevent the other from mating with his female mate. ! 4. In the pedigree below, circles represent females and squares represent males. Lines connecting the individuals are genetic pathways indicating direct relationships. This is a pedigree of a diploid species. Given the information in the chart, calculate the coefficients of relatedness requested. A) E-F = 0.5 * 0.5: r=0.25! B) D-F = 0.5 * 0.5: r=0.25! C) I-J = 0.5 * 0.5: r=0.25! D) E-D = 0.5 * 0.5: r=0.25! E) G-B = 0! F) D-J = 0.5 * 0.5 *0.5 : r=0.125! G) H-I: r=0.5! Altruistic behavior directed toward unrelated individuals has been documented in several species (including humans). For example, one male baboon might come to the aid of a totally unrelated male baboon in a fight. 1. a) Give an additional example. Another example of this reciprocal altruism can be seen in vampire bats. Vampire bats rely on getting their nutrition through ‘sucking’ the blood from other animals. They are required to drink as much blood as they weigh in order to be nourished each day. If they go two days in a row without having blood as their meal, they most likely to die. It has been observed that those that are not successful in getting their meal are helped by other bats who regurgitate some of their blood for those that didn’t have any. This is done with the expectation that the favor will be returned in the future. ! 5. 1. b) Explain how this type of behavior might be selected for. This type of altruism might be selected for in unrelated individuals in the hopes of having the favor returned in the future. If these individuals are more likely to interact in future, then this type of behavior becomes beneficial as they it becomes more likely that they will be payed back. If this also gives an advantage to an individual over its peers, then this is the type of behavior that will be selected for. Moreover, as seen with the bats, if the giver’s own survival is improved in the long run (if in the future the giver is unable to get food, the recipient will return the favor and help it survive too, then behavior is also likely to be favored by natural selection. ! 1. c) What features of an organism and its social system would likely be necessary to allow the evolution of such behavior? The features and conditions needed for Reciprocal Behavior to occur would include: ! ⁃ Repeated interactions between the individuals as this allows for them to pay each other back in the future. ! ⁃ This would allow for individuals to have an advantage in their social system as they are more certain of their survival in the future. These individuals that survive longer (and have a lower dispersal rate) would selected for their trait of altruism and increase their frequency in the population. ! Distinguish between “fitness” and “inclusive fitness.” Using an example, explain the relevance of “inclusive fitness” (as opposed to just “fitness”) for animal behavior. Fitness can be considered as a relative measure of reproductive output. Inclusive fitness is a combination of direct and indirect fitness where direct fitness is the increase in number of offspring an individual might produce and indirect fitness is the increase in number of offspring that individual’s kind may produce as they also carry the its alleles. ! Belding’s ground squirrel are an example of species that show this trait and help us understand the relevance of it.The old females always make the yell to signal that a predator or possible danger is near however, this signal results in their death 50% of the time. They still do this though because of the concept of inclusive fitness whereby the individuals around them are most likely to be their relatives (as they travel with their own colonies) and so they share the same alleles which can be passed on to offsprings and increase their allele’s market share through the relatives. ! 6. 7. Bar graphs will sometimes have an error bar. In such cases, the height of the bar typically indicates the average value for the thing reported (“number of offspring” in the graphs above). This is based on measurement of the thing in numerous different individuals. The error bar then gives an indication of how much the different individuals varied for the thing measured. Often it will be reported as a standard deviation. What does it mean if the standard deviation is large? What does it mean if it is small? How does the standard deviation influence your comparison between two bars and your likelihood of concluding that they reflect a true difference in the thing measured? Large standard deviation signifies widely spread data distribution and is therefore considered less reliable. Smaller standard deviation means that the data is more consistent and similar therefore more reliable. The standard deviation influences a. A female with one mate produces 60 offspring. A male with one mate produces the same amount of offspring. They are both the same number because both are measuring the same things which is one male and one female. ! B. Females with two mates produce 50 offspring. One possible reason as to why this is lower could be because of the variation of females tested. The number of offspring are measured for and represent different females - ones that have one mate or two mates but not both - however, this could just be a result of natural variation among females. The data showing fewer offspring could have just meant that it happened by chance and unrelated to the number of mates they had. Another reason might be because of the potential stress caused by the presence of 2 males. This might have affected the fertility in either the female or the male. Error bars would be a useful piece of additional information as they would show the extent of variation in the reproductive output among females with access to two males and those with access to one male. If the bars show more variation in both groups, the lower number of offspring could be seen as an error from the individual females measured. This would mean that the average reproductive output for a greater number of flies would be the same for females with access to one mate or two. ! c. Females with 4 mates can be assumed to have 60 offsprings. While males with four mates would most likely have 150 offspring. This is in accordance with the trends from the bar graphs. ! d. According to the graph, the reproductive output of females don’t seem to be limited the number of mates they have so it may be inferred that they are limited by production of their own eggs or outside factors affecting their fertility. Males on the other hand show that their number of offspring increase with the number of mates so they seem to be limited by the number of mates they have. ! e. In order to have draw clear comparisons between the graphs and data presented on them, they must both be measuring the same thing. Furthermore, both must be presented on the same scale otherwise comparisons may appear to be misleading if they are on different scales. !