Monday, April 6, 2009
Great diversity of Fruit fly wing patterns
On page 209, there are numerous pictures of Fruit fly wing patterns. Explain the uses of these patterns and how evolutionary process led to the great diversity of wing patterns. Describe how these wing patterns of Fruit fly is connected to the evolution of fruit flies.
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There is a great variation in wing patters, as seen by FIG 8.7. As Carroll states, by changing and playing around “with the switches of pigmentation genes, flies have evolved a great diversity of wing patterns under both sexual and natural selection” (210). The most common pattern is a black spot near the tip of the wing. Even though this seems like a simple design, it actually could be a process of “multistep series of changes” (208) in order for the spot to evolve. In fact, most physical traits do not just appear but evolve over and build up over many generations, just like the wings of fruit flies.
ReplyDeleteOne reasons that fruit flies develop these patters is in order to find a mate and for sexual reasons. The males are usually the only ones restricted to the pigment patters and “are displayed during elaborate courtship dances…in front of the female”( 208). But when the females stop selecting on the traits then there is less pressure to maintain it so it disappears and the wing patterns change. Another reason that the wing pattern might change is that there is a mutation in the switch that made the spot and it becomes inactivated and stops producing that pattern.
So it seems as if the wing patterns evolve over time when “old” genes learn new tricks. What this means is that there are different variations that could happen but the ones that are more common and would attract more females, in this case the black spot at the tip of the wing, is the one that evolves.
http://www.fcla.edu/FlaEnt/fe88p321.pdf
http://entomology.ifas.ufl.edu/creatures/fruit/tropical/Schoepfia_fruit_fly.htm
http://www.hhmi.org/news/pdf/carroll3.pdf
On page 209, Carroll describes the evolution of the patterns on the wings of fruit flies to further study evolution in other species. Over time, melanin is used by fruit flies as a “paint brush” to show the darker pigmentation on the wings of the fruit flies (Carroll 209). The enzymes that create the spots synthesize melanin to make the wings darker. To control the patterns made in the wings, genes are switched on or off.
ReplyDeleteThe study done on fruit flies by Carroll also shows how traits can disappear. In many cases, Carroll found that spots stopped showing up in different species. One reason was given that the females stopped looking for this trait when looking for reproduction. Therefore, the pressure to create this trait in males decreases and the trait fades away since it is no longer needed to help reproduction.
The study of these fruit flies has been so interesting because of the fact that the protein that aids in the production of the spots is an “old” protein. This means that the new genes didn’t produce this protein just to help create patterns on the wings. Instead, mutations over time changed the binding sites for these proteins so different patterns were made. Over time, spots began to show up and this was a selective advantage for males wanting to mate with females.
This is called co-opting. In other words, something that already existed, such as an organ or a protein, evolved to show a different purpose in surviving and reproducing. In one article, Carroll was quoted comparing this event to a Christmas tree. For example, if there is a pine tree in your yard, it’s just a regular tree until the winter season comes along. It was always there, but it isn’t until it’s decorated with lights and ornaments that it has any specific function. Overall, this is what the protein did in fruit flies. It was always present, but mutations soon made it a selective advantage for the proteins to have a specific function in the pattern of the wings.
http://www.hhmi.org/news/pdf/carroll3.pdf
http://en.wikipedia.org/wiki/Drosophila_melanogaster
There is a great variation in wing patters, as seen by FIG 8.7. As Carroll states, by changing and playing around “with the switches of pigmentation genes, flies have evolved a great diversity of wing patterns under both sexual and natural selection” (210). The most common pattern is a black spot near the tip of the wing. Even though this seems like a simple design, it actually could be a process of “multistep series of changes” (208) in order for the spot to evolve. In fact, most physical traits do not just appear but evolve over time and build up over many generations, just like the wings of fruit flies.
ReplyDeleteOne reasons that fruit flies develop these patterns is to find a mate. The males are usually the only ones that are restricted to the pigment patterns. The patterns “are displayed during elaborate courtship dances…in front of the female”( 208). But when the females stop selecting on the traits then there is less pressure to maintain it so it disappears and the wing patterns change. Another reason that the wing pattern might change is that there is a mutation in the switch that made the spot and it becomes inactivated. As a result, the switch will stop making the pattern.
It seems as if the wing patterns evolve over time when “old” genes learn new tricks. What this means is that there are different variations that could happen but the ones that would attract more females are the ones that evolve. In this example the black spot is the selected pattern.
http://www.fcla.edu/FlaEnt/fe88p321.pdf
http://entomology.ifas.ufl.edu/creatures/fruit/tropical/Schoepfia_fruit_fly.htm
http://www.hhmi.org/news/pdf/carroll3.pdf
There is a great variation in wing patters, as seen by FIG 8.7. As Carroll states, by changing and playing around “with the switches of pigmentation genes, flies have evolved a great diversity of wing patterns under both sexual and natural selection” (210). The most common pattern is a black spot near the tip of the wing. Even though this seems like a simple design, it actually could be a process of “multistep series of changes” (208) in order for the spot to evolve. In fact, most physical traits do not just appear but evolve over and build up over many generations, just like the wings of fruit flies.
ReplyDeleteOne reasons that fruit flies develop these patters is in order to find a mate and for sexual reasons. The males are usually the only ones restricted to the pigment patters and “are displayed during elaborate courtship dances…in front of the female”( 208). But when the females stop selecting on the traits then there is less pressure to maintain it so it disappears and the wing patterns change. Another reason that the wing pattern might change is that there is a mutation in the switch that made the spot and it becomes inactivated and stops producing that pattern.
So it seems as if the wing patterns evolve over time when “old” genes learn new tricks. What this means is that there are different variations that could happen but the ones that are more common and would attract more females, in this case the black spot at the tip of the wing, is the one that evolves.
Due to the studies of Carroll and his colleagues at the University of Wisconsin-Madison , there have been a lot of questions answered regarding fruit fly wing patterns. The researcher said their findings emphasize the evolutionary significance of "pleiotropic" genes -- those with multiple on-switches that enable the expression of a single gene in different tissues or at different stages of development. This explains why the wing patterns change and evolve over time. Their genetic studies focused on the role of DNA segments called cis-regulatory elements that were thought to be involved in the evolution of wing spots. The researchers' comparison of the different species revealed that all the gains or losses of spots involved mutations that altered CREs for the yellow gene. It showed how the fruit flies use a gene that is already active in the wing and modifies the patter. The scientist thinks that this is strong clue to how nature invents, which is by using material that is already available
http://www.biology-online.org/articles/fruitfly_study_shows_evolution.html
http://www.hhmi.org/news/pdf/carroll3.pdf
the book Carroll addresses the various patterns that can be found on the wings of fruit flies. Although they may seem purely decorative these patterns are used in the process of sexual selection that is discussed on page 109-110. Just as the peacock uses an elaborate tail to attract a mate, the fruit fly has wings patterns and uses these in a dance to court his mate. In this way sexual and natural selection play the role in creating these intricate patterns. Because they are advantageous to the male in reproducing, they are a characteristic that is more likely to be passed on through generations and help in sexual selection once more.
ReplyDeleteFor the fruit fly these patterns normally consist of a black spot near the tip of their wings. This variation in color, the black spot, is formed with the use of pleiotropic genes. These are genes that have different switches that turn it “on” in certain body cells and at different stages of maturation and development. This is what explains the vast variety of patterns on the fruit fly wings. The pigment melanin, discussed in chapter 7 with human skin and its affect on skin color, is used to create these spots. The genes that express melanin in the fruit fly are pleiotropic and are turned on in certain cells for either a longer or shorter duration of time. This creates the different patters that one sees. Yet this should not be seen as an overnight change, the offspring of one fruit fly being completely different from the parent, but rather a progressive change that took time. The melanin gradually becomes darker and lighter in certain areas, spreading or shrinking, creating a plethora of different patterns through the process of evolution.
The patterns on the fruit fly wings are connected to evolution through sexual selection and how these spots are used in attracting mates. The higher advantage of the pattern to attract a mate increases the probability that the fruit fly will have offspring who carry the certain characteristic that attracted the mate in the first place. In doing this the pattern on the fruit fly wing could be passed on and spread throughout the population, evolution needing both survival and reproduction.
http://www.biology-online.org/articles/fruitfly_study_shows_evolution.html
http://en.wikipedia.org/wiki/Melanin#Biosynthetic_pathways
http://en.wikipedia.org/wiki/Sexual_selection