More Information at:
http://www.eoearth.org/article/Biological_mimicry
http://www.christs.cam.ac.uk/darwin200/pages/index.php?page_id=g6
Thursday, February 21, 2013
Mimicry
In chapter 10 the textbook talks about one instance of mimicry. Mimicry is when one species has developed similar characteristic to a model, that is not closely related to it. The example in the textbook discusses the tephritid fly that mimics the jumping spider in order to keep from becoming prey to the jumping spiders. This form of mimicry is odd because it is unusual for the prey animal to mimic its predator. It was described as "a sheep in wolves clothing." There are many different forms of mimicry. The adaptation of mimicry increases the animal's fitness by reducing its chances of being preyed on or by increasing its ability to capture prey. The evolution process is slow, but sometimes it does not take a great deal of variation to increase one's fitness over another of the same species. One site I found talks about the Eastern tiger swallowtail caterpillar and says that " any mutation that occurred which made one caterpillar look 2% more
turd-like than the others would give that caterpillar a greater chance
of survival," (Montgomery). That sums up the evolution process for this form of mimicry in my opinion; the caterpillar would have an increased fitness just because it had a slight similarity to something that repels its normal predators. Then since it is a heritable trait it would be passed on and become more common. The predator would eventually become aware of the ones that are a little similar to scat, and we would see an arms race to become more similar to and to be able to identify the actual caterpillar.
More Information at:
http://www.eoearth.org/article/Biological_mimicry
http://www.christs.cam.ac.uk/darwin200/pages/index.php?page_id=g6
More Information at:
http://www.eoearth.org/article/Biological_mimicry
http://www.christs.cam.ac.uk/darwin200/pages/index.php?page_id=g6
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Would copying the behavior of another animal be a form of mimicry? The definition says the species "developed" similar characteristics but could they develop similar actions? Is that called mimicry or is there another term for this?
ReplyDeleteThat is an interesting question. In this context the term "developing" suggests that the trait(s) being mimicked must have a genetic basis. This is, of course, the only way a trait could be passed from generation to generation and ultimately become "developed" through selection. But, what about behavior? Does behavior have a genetic basis? Could a person be genetically predisposed to be a "mean person", "nice person", "murderer"? To what degree do genes influence the behavior of organisms?
DeleteOne of Eathan's links talk about the Cuckoo birds. They are famous and baffling in that they lay their eggs in the nests of other species (e.g., reed warblers) and when they hatch they push out the other eggs and trick the warbler into raising it (even though it looks very different). How did this come about? The mother cuckoo laying eggs in nests (a behavior...genetic basis...?). Furthermore, the Cuckoo eggs look very similar to warbler eggs (genetic basis...likely) and when the cuckoo hatches the hatchling makes calls that sound like the warbler (behavior…genetic basis…?) which presumably coaxes the warbler into providing parental care.
The fact that these behaviors are seen in the adults and their subsequent children suggest that there is a genetic basis for this behavior. Is it possible that cuckoos are trained by other cuckoos to lay eggs in the nests of other species? If so, that weakens the hypothesis pertaining to a genetic basis. What about the hatchlings, are they simply copying the warbler species call? If so, this also weakens the hypothesis with respect to genetic control. Perhaps there is another possibility. Could it be possible that the cuckoos have an aptitude for repeating the behaviors of those around them? Now, that could clearly have a genetic basis. It would seem; however, that simply having this “aptitude” for copying would simply not be enough or would it? An extreme case but, what if the egg of a snake looked enough like the bird egg and it were allowed to remain and the snake hatched. If the snake could make calls like the bird, do you think the bird would care for it? It is unlikely that the snake would have the genetic basis to make the bird call sounds, so it seems for this all to work the organisms (in this case) would have to be somewhat related (i.e., both be birds…which would be more closely related to one another than to the snake) in order to have the genetic prerequisites for the behaviors.
In short, looking at behaviors is quite tricky and the cuckoo example is just one of many strange behaviorally-based mimicry events. The tephritid fly example that Eathan mentions has coloration patterns suggestive of its predator (certainly can be genetic basis), but it also “acts” like (genetic basis…?...) the predator - it’s movement patterns when confronted by a predator. This is another tricky example to work through. As far as I am aware these types of behavioral mimicry are often thrown under the label of “aggressive mimicry”. It is a rather complex mix and collectively these types of inquiries are usually thrown under the label of a “mimicry complex”.
If someone was walking by the hallway and heard a statement like the following...I suspect they would think we were crazy. The example is good, and it made me chuckle.
ReplyDelete" any mutation that occurred which made one caterpillar look 2% more turd-like than the others would give that caterpillar a greater chance of survival," (Montgomery).
Yea, I didn't really know how else I should state it. The way he said it made sense and was applicable.
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