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Melanism Wars

Melanism Wars. Julia Kard. The Peppered Moth ( Biston betularia ). Common in England and North America Small Moths (1 ½ - 2 ½ inch wingspan) Have light wings “peppered” with black spots (Trevis).

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Melanism Wars

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  1. Melanism Wars Julia Kard

  2. The Peppered Moth (Bistonbetularia) • Common in England and North America • Small Moths (1 ½ - 2 ½ inch wingspan) • Have light wings “peppered” with black spots (Trevis) ARKive. Web. 4 Apr 2010. <http://www.arkive.org/peppered-moth/biston-betularia/image-A7959.html>.

  3. Peppered Moth Predation • Predators: flycathers, nuthatches, and the European robin • Like most moths, to avoid predators they flying at night and remain motionless during the day. • They tend to rest on tress that are covered with lichen similar in color to themselves (Trevis) Wild Birds. Web. 4 Apr 2010. <http://www.wildbirdhabitatstore.com/index.php?_a=viewDoc&docId=49>. ARKive. Web. 4 Apr 2010. <http://www.arkive.org/peppered-moth/biston-betularia/image-A7959.html>.

  4. Forms of the Peppered Moth • Biston carbonaria: almost uniformly black (this is the Melanic) • Biston insularia: the intermediate between the two extremes of primarily white and primarily black (Grant) Trevis, Craig. "Peppered Moth." Teach Apps. St. Helens Wildlife Recording Group, 2003. Web. 4 Apr 2010. <http://www.techapps.net/interactives/pepperMoths.swf>.

  5. Melanism The Life of Charles Darwin. Web. 5 Apr 2010. <http://www.smithsonianmag.com/science-nature/The-Life-of-Charles-Darwin.html>. • Melanism is the occurrence of an increased amount of dark pigmentation in an organism, resulting from the presence of melanin. • Adaptivemelanism is when dark individuals become fitter to survive and reproduce in their environment as they are better camouflaged. This makes some species less conspicuous to predatorswhile others use it as a foraging advantage (for example during night hunting). • Industrialmelanism is adaptive melanism caused by alteration of the natural environment in terms of industrial pollution. (Melanism)

  6. Industrial Melanism and The Moth • From the mid 1800’s until the mid 1900’s England was experiencing the Industrial Revolution, this meant many factories powered by coal were being built (Trevis). • Soot, smoke and other industrial pollutants from factories darkened the landscape and killed the lichen on trees (Evolution of Industrial Melanism). • The peppered moth relies on camouflage to avoid predation, and this sudden change in their environment made them highly vulnerable to predators. • This created a strong selective pressure in which moths with a darker color were much more likely to survive and contribute to the gene pool of the next generation. • Rare mutations were hence selected and over time the population adjusted to a new equilibrium.

  7. Before and After the Industrial Revolution http://biology.fullerton.edu/life/ch/ch07.html

  8. Early Interest in the Moth • By 1900 98% of peppered moths in England were of the carbonaria variety (Grant). • There were many early theories as to why the sudden increase in the carbonaria form had occurred: • The chemicals in the smoke darkened the moths (Trevis). • The adults matched their color to their resting place just as the peppered moth larvae do (Grant). • It was later discovered that the color was genetic and caused by a mutation in the DNA of a moth that caused excess amount of melanin to be present. The offspring of a light moth would be light in color and the offspring of a melanic moth would be dark (Owen 178). • The remaining question is why did the dark moth forms take over? Did they have an advantage in the now dark forests? If so this was a result of natural selection.

  9. Natural Selection At Work? • In 1896 J.W. Tutt hypothesized that the speckled moths gain protection from predators by resembling lichens, and in areas where the lichens have died and trees become black, the betularia forms have become the victims of predation, and the formerly rare black forms are now more likely to pass their traits to the next generation (Owen 180). • Over 100 other species of moths were observed to darken over time in polluted forests (Trevis). • In order to test Tutt’s hypothesis of natural selection, British biologist Henry Bernard Davis Kettlewell ran a series of experiments and field studies. The Kettlewell Archive. Web. 4 Apr 2010. <www.wolfson.ox.ac.uk/library/archives/kettlewell/>.

  10. Predation Experiments • Kettlewell’s objective: to determine whether or not birds ate camouflaged moths at rest on their normal backgrounds, and whether the birds ate them selectively. Main aspects of his experiments: • Quantitative rankings of camouflage effectiveness (degree of conspicuousness as judged by human observers) of pale and melanic peppered moths placed on various backgrounds • Direct observations of predation by birds on moths place onto tree trunks • Recapture rates of marked moths released onto trees in polluted and unpolluted areas (Grant) • By determining the rate of change and relative fitness of the moths released in Dorset and Birmingham, he found a correspondence between frequency and fitness, supporting the idea of selective visual predation (Cook 433).

  11. Criticism • If Kettlewell’s experiments worked, why are they so heavily criticized? LIFE. Web. 4 Apr 2010. <http://images.google.com/hosted/life/l?imgurl=d955f941c5eeece3&q=bernard%20kettlewell&prev=/images%3Fq%3Dbernard%2Bkettlewell%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1>.

  12. What’s wrong with this picture?

  13. That’s Not Natural • Professor of Ecology Michael Majerus’ main criticism with Kettlewell’s work was his placement of the moths on trees, on the trunk. • In 36 years of field work he only encountered 47 moths naturally resting in visible places on trees during the day. • He separated these findings into four categories based on where the moth was resting on the tree: trunk/branch, branches, unexposed trunk, and exposed trunk. (Majerus) National Center for Science Education. Web. 4 Apr 2010. <http://ncse.com/creationism/analysis/where-peppered-moths-rest>.

  14. Data from Majerus 1964-2000 (Majerus 123)

  15. The Truth About Hiding • “Moths habitually resting in only one place will be habitually sought there” (Clarke 189). • Biologist Mikkola determined that moths kept in captivity hide by day on the underside of branches in the canopy. • Biologists Grant and Howlett did research showing that captive moths move to whatever end of their holding pen light enters. • “In truth, we still don’t know the natural hiding places of peppered moths.” (Grant)

  16. Further Criticism… • Kettlewell released his subjects during the day • Moths released during daylight hours do not behave normally and if prompted to fly, they will settle quickly on just about the first thing they encounter (Majerus 143). • Grant finds this to be one the greatest weaknesses in Kettlewell’s mark-release-recapture experiments. • Kettlewell himself notes considerably in his discussion to having “release problems” created because he wanted to avoid having moths turned loose under the cover of darkness and flying directly into his traps before having the opportunity to be hunted.

  17. Even More Criticism… • The number of moths released on trees created artificially high densities that attracted birds, and predation may have a occurred more than normal (Grant). • Also, much of the time, Kettlewell “released” death moths, meaning he took marked dead moths and glued them to the trunks of the trees. • This caused conditioning of the birds to expect to be fed when looking at trees because they were getting so heavily fed (Hooper 49). "Spotted Fly Catcher with Moth." flicker. Web. 4 Apr 2010. <http://images.google.com/imgres?imgurl=http://farm3.static.flickr.com/2646/>.

  18. What’s wrong with this picture?

  19. Can’t Fake the Funk • Journalist Judith Hooper, the author of a book chiding the work of Kettlewell, questions the validity Kettlewell’s data. • For the first six days of his research Kettlewell was only catching a few moths per day, then suddenly he was netting 23-34 moths per day. • After asking pointed questions about what could have accounted for this dramatic reversal of fortune -- and checking for herself that no significant weather changes happened during that time -- Hooper speculates that he might have fudged the numbers.

  20. (Hooper 48)

  21. Further Criticism… • Kettlewell proposed that moths actively seek out different resting sights. • To test this idea he put the melanic and normal forms of the peppered moth into a barrel lined with black and white striped of card and recorded where they had settled, and concluded that the moths compared their own color to that of their landing place and tended to rest on places least contrasting to their own color. • Biologists Grant and Howlett attempted to redo this experiment by using polymorphic peppered moths caught near Liverpool, England and also painting the moths opposite colors. They found no evidence that betulariaand carbonaria prefer to rest on different backgrounds.

  22. Even More Criticism… • Kettlewell determined the fitness of his species based on how well he felt they blended into their surroundings. • Majerus points out that tha recent work on birds show that their ability to see into the UV spectrum indicates that the visual acuity of birds is greater than that of humans and this should be taken into account when undertaking experiments centering on visual predation” (142).

  23. Confounding Evidence • After the Clean air act was established in England in 1956 in response to London’s Great Fog of 1952, levels of pollution and soot plummeted and the forests slowly began to return to their original form, and numbers of the betulariadrastically increased while the carbonaria variety once again fell into rarity (Cook 439). • This was also seen more recently in North America where highly accurate accounts of the peppered moth populations in Michigan and Pennsylvania (areas affected by pollution from industry) were kept and compared to an area unaffected by pollution (Virginia). • The clean air act of 1970 was shown to have a similar effect on the frequency of carbonaria in those regions.

  24. (Wiseman)

  25. Conclusion • According to Professor of Biology Bruce S. Grant “despite design problems, Kettlewell’s predation experiments are still instructive.” • He argues that while Kettlewell made mistakes, he consistently did so in both places he did research, he always released the moths on the trunks of trees, and always did so during the day time . • Furthermore, he goes on to day that “No other evolutionary force can explain the direction, velocity and the magnitude of the changes except natural selection. That these changes have occurred in parallel fashion in two direction, on two widely separated continents, in concert with changes in industrial practices suggests the phenomenon was named well.” • Furthermore, the evidence provided from the study in North America is in perfect correlation with the data from England. While a correlation alone does not establish a causal relationship, common correlations suggest a common cause. (Wiseman)

  26. Bibliography • Clarke, C.A. Evolution in Reverse. New York: Oxford U. Press, 1994. Print. • Cook, L.M. "Changing Views on Melanic Moths." Biological Journal of Linnean Society. 69. (2000): 431-441. Print. • "Evolution of the Peppered Moth." You Tube. Web. 30 Mar 2010. <http://www.youtube.com/watch?v=LyRA807djLc&feature=related>. • Grant, bruce S. "Fine Tuning the Peppered Moth Paradigm." Evolution. 53.3 (1999): 980-984. Print. • Hooper, Judith. Of Moths and Men. New York: W.W. Norton & Co. Inc., 2002. Print. • Majerus, Michael. Industrial Melanism: Evolution in Action. Chicago: Chicago Press, 1998. Print. • "Melanism." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 4 Apr. 2010. Web. 5 Apr. 2010. • Owen, D.F. Natural Selection and Evolution in Moths. Chicago: Chicago Press, 1997. 177-181. Print. • Trevis, Craig. "Peppered Moth." Teach Apps. St. Helens Wildlife Recording Group, 2003. Web. 4 Apr 2010. <http://www.techapps.net/interactives/pepperMoths.swf>. • Wiseman, L.L. "Recent History of Melanis in American Peppered Moths." American Genetic Association . (2002): Print.

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