2009 Week 4 Reproduction
Using examples from your supplements and the chapters (Krebs & Davies 1993) about parental care & mating , alternative strategies of reproduction and selfishness/altruism…
Using examples from your supplements and the chapters (Krebs & Davies 1993) about parental care & mating , alternative strategies of reproduction and selfishness/altruism…
June 23rd, 2009 at 11:30 am
what helps you synthesize ideas across the concepts in these chapters that touch on reproduction…some interesting questions to explore might include:
1) is parental care selfish or altruistic?
2) what do the mechanisms of sex change teach us about thinking like a fish, not like a human? are these genotypes ultimately selfish or making the best of a bad deal?
3) some folks think humans are the only animal that is altruistic, others that other animals help us see that what we think is altruistic in humans is really selfish….what do you think?
June 24th, 2009 at 2:15 pm
1) is parental care selfish or altruistic?
Altruism is defined as acting to increase the recipient’s fitness with no benefit to the actor’s survival and reproduction.
Parental care is viewed by some to be selfish as opposed to altruistic. Parental care can be selfish in the aspect that parents feed their offspring because natural selection favors individuals who maximize their gene contribution to their offspring; therefore the offspring will have copies of the parent’s genes.
This is measured in terms of the coefficient of relatedness discussed on page 266 of Krebs and Davis. The coefficient of relatedness quantifies the kin selection process in terms of direct, indirect, and inclusive fitness. The parent receives direct fitness from personal reproduction, indirect fitness for aiding the survival of non-descendant kin, and both routes of fitness is called an actor’s inclusive fitness (Krebs & Davis 266).
Even the act of altruistically caring for non-kin young can be perceived as selfish because the individual still benefits. An example is of the black-tailed prairie dogs. Figure 11.2 in Krebs & Davis shows the results of an experiment that shows that individual prairie dogs gave alarm calls just as frequently when there non-kin in their home as when there were offspring. The benefits from this call is selfish in the fact that it pays to warn others of a predator, even if they are not kin, because if the predator fails he may be less likely to return to hunt in the same area (Krebs & Davis 272).
The argument for selfishness in parental care is sustained because the individual benefits in terms of its own fitness by providing parental care.
June 25th, 2009 at 2:06 pm
During this week I learned about how individuals distinguish between kin and non-kin. There are three hypotheses that have been proposed: 1) “Green Beard effect” This is an unlikely theory, Hamilton et al (1964) if my father had a green beard and was nice then all my kin would have green beards and be nice. In this idea is that there may be recognition alleles that express phenotypically that allow one to recognize the same alleles in others. 2) “Treat anyone in my home as kin” If you are in my house you must be family. An example is the reed warbler mob cuckoo when they fly near their nest but raise the young cuckoos in their nest as their own. 3) Imprinting Those that you grow up with are kin. As in geese they follow the first thing they see mostly their mother, but not necessarily. This is based off of Konrad Lorenz study of the graylag geese.
Hamilton, W.D. 1964. The genetical evolution of social behavior. I, II. J.theor. Biol. 7, 1-52.
June 25th, 2009 at 2:36 pm
I found the example of the blue-headed wrasse an interesting example of an alternative breeding strategy in chapter 10 (pg 260). The sex change of the wrasse, as defined by Krebs and Davies is “socially controlled”. I looked up more information to see how it is determined which female becomes then new male.
The group size is normally five to six females for every large male. I found that these males were commonly referred to as “terminal” males. This male is very aggressive while tending to his harem and he even changes color to show aggression towards the smaller males who try to sneak mating with the females. In the cases where the terminal male suddenly dies, he is replaced by the largest female of the harem. There is a social hierarchy within the female group. The largest female is at the top and when she dies or changes to a male, then the next largest females takes her place. I also found it interesting that the female will begin to act like a male within an hour of replacing him. Within two weeks she (now a he) will be producing sperm. (Piper 2007)
I believe that the blue-headed wrasse is an example of a species making the best of a bad situation. The largest males are the most successful at reproduction. The smaller males sneak or travel in groups to get a chance to reproduce. These smaller males are forced by their circumstances to attempt less successful strategies because the females are attracted to the largest, most brightly colored males.
Piper, R. 2007. Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, pp 211-213. Greenwood Press, Connecticut.
June 26th, 2009 at 9:30 am
2) what do the mechanisms of sex change teach us about thinking like a fish, not like a human? are these genotypes ultimately selfish or making the best of a bad deal?
The mechanisms of sex change teaches us about thinking more like a fish by making the best of a bad situation. In the Blue headed wrasse example, it is better if you are small to be female rather than male. Reason one is that there is one large male that will fight and defend his territory and his group of females so small males will have to try and sneak in or form small groups and chase females in order to try to mate. In this case, its better to be female while small in order to have better reproductive success. Once the large, bright colored male, dies, then one of his females will replace him, typically the largest female, and she have the upper hand by changing to a male, which will further her reporductive success. As a male, there will be more opportunties to mate with multiple females.
In the example of the clownfish, the process is reversed. In this species, females are large. The males will benefit while small, since the sea anemones in which they live are farely small places and the male has the chance to breed with the large and fecund females. This species tends to live in pairs and the reproductive success of the pair is limited more by the females ability to produce eggs not the male producing sprem. If the female is killed and the male is then joined by a smaller individual then the male will change to begin laying eggs while the smaller newcomer acts as the male. Again this is making the best of a bad deal simply because the species are trying to better and pass on their genotype as much as possible while they are around and they have to make the best decision for the reproductive success.
June 26th, 2009 at 10:46 am
As a critique of myself, the sentence, “Again this is making the best of a bad deal simply because the species are trying to better and pass on their genotype as much as possible while they are around and they have to make the best decision for the reproductive success”, is terrible so i will try to explain what if means to me a little better. With both examples of the clownfish and the wrasse, these species use the sex change as an alternative breeding stratgey of shifting their genotype porportions within their species. Through this strategy, the wrasse for example are increasing their opportunties to reproduce by starting out as female rather than you, small males that could not compete with the large, brightly colored males. As a female producing eggs that are fertilized by the brightest largest males until the females reaches a large size. When the female gets the opportunty to change to the actions of the males, then reproduction is furthered by breeding with multiple females which will continue to increase that particular males genotype with in the gene pool of that males species.
June 26th, 2009 at 7:19 pm
I’ll focus on the second question as well because protogynous (female-male) and and protandrous (male-female) was a new concept to me and I find it fascinating. I agree with Janell that it is an alternative mating strategy that is making the most of a bad situation. Because of the high level of intrasexual competition in males within the wrasse population, males would expend all their energy trying to defend and fight with each other, and the smaller males would obviously loose out every time. Now to go off on a tangent: in the case of the olive baboons at the end of chapter 11, males would solicit help from relatives/recognized individuals to defend females in oestrus from other males in an example of reciprocal altruism. Would the wrasse still swap sex if this level of socialization was present in the fish species and smaller males could coordinate defense from larger males in the population? Alternatively, would the smaller, younger baboons be females until they had built up enough size and energy to be competative with the dominant males if their sexual organs were as “relatively simple” as the wrasse? I still don’t see the second option being viable in mammal species, even if physiology allowed it. I think Krebs and Davies make an excellent point when they highlight that experience and learning the techniques of resource/mate defense is also important in terrestrial males, and that there is a social component to the process. Really a lot of good information in these chapters, I’m just thinking out loud a little bit trying to process it.
June 26th, 2009 at 8:53 pm
Why do some animal species become extinct as a result of habitat loss and others do not? The white-winged dove has experienced a server loss of its native habitat, shrub forests, yet it has not gone extinct, rather it expanded its range northward to include agricultural and urban areas and displays alternative behaviors. Some observed behavior differences between the original habitat and the expanded habitat include: solitary nesting verses colony nesting, seasonal migration verses permanent residence, and one annual nesting attempt verses two to five annual nesting attempts (Small et al. 2005). What is the appropriate question to ask in formulating a testable hypothesis about the alternative behavior? The first question might be, is the behavior a result of cultural transmission or genotype? If a study can conclude that the behavior is a result of a genotype, then the next question may be was there a shift in the proportion of genotypes within the population or does the unchanged genotype code for a conditional response relative to the environment? Changing environmental resources change the value of their associated behavioral costs and benefits. If the behavior is not conditional for each individual then it is fixed. Did the original population have variation through multiple fixed genotypes (polymorphism)? Our assumption about a situation can bias how we address any wildlife or natural resource management issue. Conservation can be a more complex issue that just preserving habitat. Understanding the mechanism, origins and functions of behaviors can help professionals to draft more appropriate management recommendations.
Small, M.F., Schaefer, C.L., Baccus, J.T., and Robertson, J.A. 2005. Breeding Ecology of White-Winged Doves in a Recently Colonized Urban Environment. Wilson Bulletin 117:172-176.
June 28th, 2009 at 4:44 pm
I found the protogynous hermaphroditism strategy most fascinating during this block of instruction, including the discussions on the Bluehead Wrasse. I also wanted to do some additional research on the “socially controlled.” I found an article from Perry & Grober that elaborated on this situation, and they stated that large males could inhibit females from changing sex through aggressive behavior. As I was researching, I was only able to find a few fish that were used to illustrate this alternative breeding strategy; most are invertebrates like earthworms. I believe that this is a strategy that is one that makes the most out of bad situations; a genotype that selects for large females to replace the large, harem owner male that dies, ensuring the largest individuals dominate the species. Also, I found a link for a topic that relates to Week 5’s discussions on signaling and also Week 4’s parental care discussions. This is from BBC News and they usually have a weekly science and nature article that is behavior-focuses.
http://news.bbc.co.uk/2/hi/science/nature/8040259.stm
Perry, A.N. & Grober, M.S. 2003. A model for social control of sex change: interactions of behavior, neuropeptides, glucocorticoids, and sex steroids. Hormones and Behavior. 43: 31-38.
June 29th, 2009 at 12:37 pm
Jeff, thanks for a really nice reference on the mechanisms of sex change! I’m curious to learn more about the interactions they mention in the title…which neuropeptides? how are the glucocorticoids involved? is this at all related to the adrenal/testosterone linkages that make a male switch between satellite and territorial behavior?
I’m wondering if you could elaborate a bit on this sentence that I found confusing: “only able to find a few fish that were used to illustrate this alternative breeding strategy; most are invertebrates like earthworms”.
As foreshadowing for next week, I would also like to hear more dialogue about this intriguing comment: “ensuring the largest individuals dominate the species”. Does this mean you believe that natural selection happens at the level of individuals rather than genotypes?
The reason I find this confusing is that the large males also made copies of their gametes when they were smaller females. They will only be large males for a short time, when another individual goes through the sex change and defends the most attractive part of the reef. In what sense does this mean that large males dominate the species?
I am aware of the folk-psychology idea that large males dominate. We see it often in conversations around the dinner table! But what is the science behind this myth?
June 29th, 2009 at 12:39 pm
Just to get some more dialogue rolling, what is wrong with the following definition of altruism?
“Altruism is defined as acting to increase the recipient’s fitness with no benefit to the actor’s survival and reproduction. “
June 29th, 2009 at 12:53 pm
Virginia raised an interesting question about testable hypotheses about behavioral adapatations and how they may be relevant to management questions. She noted variation within the last few decades in White Winged Doves:
“Some observed behavior differences between the original habitat and the expanded habitat include: solitary nesting verses colony nesting, seasonal migration verses permanent residence, and one annual nesting attempt verses two to five annual nesting attempts (Small et al. 2005).”
This really makes us synthesize ideas across the weeks, because it draws on ideas of comparison of populations (week 1), migratory habitat (week 2), group size of nesting colony (week 3) and reproduction (week 4). It foreshadows nicely for next week, when we will be talking more about the conclusions of this course. Namely, that the nice simple models don’t always match reality very well, however, they do lead us to ask testable hypotheses in the field that we otherwise might not have thought about if we were not thinking about natural selection in terms of “selfish genes” rather than “selfish individuals”.
What I am not clear about, is how the White Winged Dove example relates to the concepts in week 4. Seems like renesting relates to reproduction in variable environments where nest loss is likely, however, I do not recall a discussion of that topic in Krebs & Davies (1993).
Who wants to help clarify?