Asymmetry: Causes, Measurements and Analysis Student Name, [email protected]; Mentor Name,...
1
Asymmetry: Causes, Measurements and Analysis Student Name, [email protected]; Mentor Name, Department, Buffalo State Fluctuating asymmetry (FA) refers to subtle deviations from perfect symmetry, which is random in direction, on otherwise bilaterally symmetrical organisms (Polak et al. 2004). When bilateral measurements are taken, the left side is subtracted from the right side (R-L) and plotted. If there were no asymmetry, this procedure would result in a vertical line forming at the zero mark. However, an FA distribution results in a bell curve where the majority of measurements are distributed around a mean of zero with only a few deviations. Fluctuating asymmetry is considered to arise from an organism’s inability to buffer against developmental noise (Swaddle 2003). Developmental noise refers to outside interference and stressors that can hinder an organism’s ability to develop properly by causing random fluctuations and mutations at the cellular level (Swaddle 2003). Ultimately, the presence of FA reflects on the organism’s developmental instability. Although commonly interchanged with fluctuating asymmetry and development noise, developmental instability refers to an organism’s inability to properly develop and buffer against developmental interruptions as a whole (Swaddle 2003). There are many genetic and environmental factors that can disrupt developmental stability and increase developmental noise and asymmetry. However, the response of an asymmetry based on stress appears to be species and trait specific (Leung and Forbes 1996). Traits of some species may show signs of FA whereas traits of others do not appear to be affected, even when severe stress-induced mortalities are present (Bjorksten et al. 2001). Due to this, the relationship between asymmetry, genetics and environmental Asymmetry is found in every species within the animal kingdom. Certain asymmetries are conspicuous, while others are subtle. Asymmetries can be exhibited internally or externally. Three kinds of asymmetry have been studied in vertebrates: directional asymmetry (DA), antisymmetry (AS) and fluctuating asymmetry (FA). The presence of an asymmetry may be an indicator as to how the animal handles developmental stress, or how a population may be evolving. Asymmetry analyses have evolved into multi-step processes with strict standards for measurement error and correction, as well as specialized tests to account for asymmetry and anomalies. Upon completion of analysis, conclusions can be drawn to indicate the presence or absence of an asymmetry and its implications for the species studied. Measurements were obtained via samples provided by the New York State Department of Environmental Conservation (DEC) from loons 2006. Overall, I would expect to see characteristics that serve an important functional role display less asymmetry than characteristics that are not critical to the survival of the bird. Asymmetry is defined as a deviation from perfect symmetry. In particular, it is a departure from symmetry among bilateral characteristics (Windig 1998). Many previous studies have been done on organisms to discover the presence or absence of an asymmetry. In a natural environment, the presence of an asymmetry is often seen. The most commonly studied asymmetries are fluctuating asymmetry, directional Directional asymmetry (DA) is defined as a fixed heritable asymmetry (Hallgrimsson and Hall 2005). All individuals of a species will exhibit the same chirality, or the same- sided asymmetry, with few exceptions. When bilateral measurements are taken, the left side is subtracted from the right side (R-L) and plotted. A typical DA plot appears as a skewed bell curve. The skewed nature follows the direction of the asymmetry, with only a few points opposite the skew. Directional asymmetry suggests that symmetry is broken at some point during development to allow for the growth of an asymmetrical feature. However, developmental consequences may abound when a reversal of the asymmetry occurs, or when the asymmetry does not fully develop (Hallgrimsson 2005). Abstract Fluctuating Asymmetry What is Asymmetry? Directional Asymmetry Bjorskten, T., Bjorskten, T., et Al. et Al. 2001. Temperature shock during development fails to increase the fluctuating 2001. Temperature shock during development fails to increase the fluctuating asymmetry of a sexual trait in stalk asymmetry of a sexual trait in stalk eyed flies. eyed flies. Proc. R. Soc. London B Biol. Sci. Proc. R. Soc. London B Biol. Sci. 268: 1503-1510. 268: 1503-1510. Campo, J. L., Campo, J. L., et Al. et Al. 2006. 2006. Genetic and phenotypic correlation between fluctuating asymmetry and two Genetic and phenotypic correlation between fluctuating asymmetry and two measurements of fear and measurements of fear and stress in chickens. stress in chickens. Applied Animal Behavior Science Applied Animal Behavior Science . In Press. . In Press. Hallgrímsson, B. and Hall B. 2005. Hallgrímsson, B. and Hall B. 2005. Varation: A Central Concept in Biology. Varation: A Central Concept in Biology. 1st ed. Academic Press. 1st ed. Academic Press. Lens, L., Lens, L., et Al. et Al. 2000. Developmental instability and inbreeding in natural bird populations exposed 2000. Developmental instability and inbreeding in natural bird populations exposed to different levels of habitat to different levels of habitat disturbance. disturbance. Journal of Evolutionary Biology Journal of Evolutionary Biology . 13: 889-896. . 13: 889-896. Leung, B., Leung, B., et Al. et Al. 2003. A critical assessment of the utility of fluctuating asymmetry as a biomarker 2003. A critical assessment of the utility of fluctuating asymmetry as a biomarker of anthropogenic stress. In: Polak, of anthropogenic stress. In: Polak, M. (Ed.), M. (Ed.), Developmental Instability: Causes and Consequences Developmental Instability: Causes and Consequences . Oxford University Press, New York, pp 415- . Oxford University Press, New York, pp 415- 426. 426. Leung, B. and Forbes, M.R. 1996. Fluctuating asymmetry in relation to stress and fitness – effects Leung, B. and Forbes, M.R. 1996. Fluctuating asymmetry in relation to stress and fitness – effects of trait type as revealed by meta- of trait type as revealed by meta- analysis. analysis. Ecoscience Ecoscience . 3: 400-413. . 3: 400-413. McIntyre, J.W. 1988. McIntyre, J.W. 1988. The Common Loon:Spirit of the Northern Lakes The Common Loon:Spirit of the Northern Lakes , 2nd ed. University of Minnesota Press. , 2nd ed. University of Minnesota Press. Moller, A.P. and Swaddle, J.P. 1997. Asymmetry, Developmental Stability and Evolution. Oxford Moller, A.P. and Swaddle, J.P. 1997. Asymmetry, Developmental Stability and Evolution. Oxford University Press, Oxford. University Press, Oxford. New York State Department of Environmental Conservation (NYS DEC), 2007. “Endangered, Threatened New York State Department of Environmental Conservation (NYS DEC), 2007. “Endangered, Threatened Literature Cited Common Loon For the purpose of this experiment, the Common Loon (Gavia immer) will be studied. No previous asymmetrical studies have been published on the Common Loon; however other avian species have been studied. These species include the Taita Thrush (Lens et al. 2000), Finches and Chickens (Campo et al. 2006). Previous studies on avian species have been performed to test for the presence of fluctuating asymmetry. Very little work has been done with avian species and directional asymmetry or antisymmetry. The loon has a wide breeding range throughout Northern North America and parts of Europe. North American Loons have a yearly migration pattern that involves summers in northern Canada, the northern US and Greenland, and winters on the east and west coasts of the southern US. Within recent years, large loon die-offs have occurred on the Great Lakes. Many of these die-offs have been confirmed as botulism type E deaths and have scientists struggling with its implications. In New York State, even with recent loon die-offs, the Common Loon is considered a species of special concern (NYS DEC 2007). Species of special concern warrant attention and consideration but current information, collected by various state agencies, do not justify listing the loon as either endangered or threatened (NYS DEC 2007). My study is specifically focusing on asymmetries of migrating loons found on Lake Erie and Lake Ontario during fall 2006. Why Do We Care? 1) Presence of an asymmetry could indicate an adaptation of the bird. - An adaptation would indicate a direct genetic link to the asymmetry. - If the bird were to exhibit a directional asymmetry, this would indicate an adaptation that explains an aspect of the life history of the species. 2) Presence of fluctuating asymmetry may indicate developmental interference. - Developmental interference could be a result of genetic factors, environmental factors, or a combination of both. - This could indicate stressors in the breeding lakes and may warrant further study. 3) An asymmetry’s sudden appearance could have implications for conservation. - Any factor that may influence the quality of loon breeding lakes (e.g., Antisymmetry (AS), is considered a random asymmetry. Antisymmetry is considered heritable in the sense that the asymmetry will be passed down to the next generation. However, it is not heritable as to which side the asymmetry will show up on. In other words, while the parent will have an asymmetry and will pass that asymmetry on to its offspring, the chance of the asymmetry being left-sided (sinistral) or right-sided (dextral) is equal (Hallgrimsson and Hall 2005). This too implies that symmetry is somehow broken during development to allow for the asymmetry. However, unlike directional asymmetry, antisymmetry has many scientists puzzled. The mechanism as to how the sided asymmetry is determined is currently unknown. Antisymmetry
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Transcript of Asymmetry: Causes, Measurements and Analysis Student Name, [email protected]; Mentor Name,...
Asymmetry: Causes, Measurements and Analysis Student Name, [email protected];
Mentor Name, Department, Buffalo State
Fluctuating asymmetry (FA) refers to subtle deviations from perfect symmetry, which is random in direction, on otherwise bilaterally symmetrical organisms (Polak et al. 2004). When bilateral measurements are taken, the left side is subtracted from the right side (R-L) and plotted. If there were no asymmetry, this procedure would result in a vertical line forming at the zero mark. However, an FA distribution results in a bell curve where the majority of measurements are distributed around a mean of zero with only a few deviations. Fluctuating asymmetry is considered to arise from an organism’s inability to buffer against developmental noise (Swaddle 2003). Developmental noise refers to outside interference and stressors that can hinder an organism’s ability to develop properly by causing random fluctuations and mutations at the cellular level (Swaddle 2003). Ultimately, the presence of FA reflects on the organism’s developmental instability. Although commonly interchanged with fluctuating asymmetry and development noise, developmental instability refers to an organism’s inability to properly develop and buffer against developmental interruptions as a whole (Swaddle 2003). There are many genetic and environmental factors that can disrupt developmental stability and increase developmental noise and asymmetry. However, the response of an asymmetry based on stress appears to be species and trait specific (Leung and Forbes 1996). Traits of some species may show signs of FA whereas traits of others do not appear to be affected, even when severe stress-induced mortalities are present (Bjorksten et al. 2001). Due to this, the relationship between asymmetry, genetics and environmental stressors are unclear.
Asymmetry is found in every species within the animal kingdom. Certain asymmetries are conspicuous, while others are subtle. Asymmetries can be exhibited internally or externally. Three kinds of asymmetry have been studied in vertebrates: directional asymmetry (DA), antisymmetry (AS) and fluctuating asymmetry (FA). The presence of an asymmetry may be an indicator as to how the animal handles developmental stress, or how a population may be evolving. Asymmetry analyses have evolved into multi-step processes with strict standards for measurement error and correction, as well as specialized tests to account for asymmetry and anomalies. Upon completion of analysis, conclusions can be drawn to indicate the presence or absence of an asymmetry and its implications for the species studied. Measurements were obtained via samples provided by the New York State Department of Environmental Conservation (DEC) from loons that had washed ashore of Lake Ontario during the fall of 2006. Overall, I would expect to see characteristics that serve an important functional role display less asymmetry than characteristics that are not critical to the survival of the bird.
Asymmetry is defined as a deviation from perfect symmetry. In particular, it is a departure from symmetry among bilateral characteristics (Windig 1998). Many previous studies have been done on organisms to discover the presence or absence of an asymmetry. In a natural environment, the presence of an asymmetry is often seen. The most commonly studied asymmetries are fluctuating asymmetry, directional asymmetry and antisymmetry.
Directional asymmetry (DA) is defined as a fixed heritable asymmetry (Hallgrimsson and Hall 2005). All individuals of a species will exhibit the same chirality, or the same-sided asymmetry, with few exceptions. When bilateral measurements are taken, the left side is subtracted from the right side (R-L) and plotted. A typical DA plot appears as a skewed bell curve. The skewed nature follows the direction of the asymmetry, with only a few points opposite the skew. Directional asymmetry suggests that symmetry is broken at some point during development to allow for the growth of an asymmetrical feature. However, developmental consequences may abound when a reversal of the asymmetry occurs, or when the asymmetry does not fully develop (Hallgrimsson 2005).
Abstract
Fluctuating Asymmetry
What is Asymmetry?
Directional Asymmetry
Bjorskten, T., Bjorskten, T., et Al.et Al. 2001. Temperature shock during development fails to increase the fluctuating asymmetry of a sexual trait in stalk 2001. Temperature shock during development fails to increase the fluctuating asymmetry of a sexual trait in stalk eyed flies. eyed flies. Proc. R. Soc. London B Biol. Sci.Proc. R. Soc. London B Biol. Sci. 268: 1503-1510. 268: 1503-1510.Campo, J. L., Campo, J. L., et Al.et Al. 2006. 2006. Genetic and phenotypic correlation between fluctuating asymmetry and two measurements of fear and Genetic and phenotypic correlation between fluctuating asymmetry and two measurements of fear and stress in chickens. stress in chickens. Applied Animal Behavior ScienceApplied Animal Behavior Science. In Press. . In Press. Hallgrímsson, B. and Hall B. 2005. Hallgrímsson, B. and Hall B. 2005. Varation: A Central Concept in Biology.Varation: A Central Concept in Biology. 1st ed. Academic Press. 1st ed. Academic Press.Lens, L., Lens, L., et Al.et Al. 2000. Developmental instability and inbreeding in natural bird populations exposed to different levels of habitat 2000. Developmental instability and inbreeding in natural bird populations exposed to different levels of habitat disturbance. disturbance. Journal of Evolutionary BiologyJournal of Evolutionary Biology. 13: 889-896.. 13: 889-896.Leung, B., Leung, B., et Al.et Al. 2003. A critical assessment of the utility of fluctuating asymmetry as a biomarker of anthropogenic stress. In: Polak, 2003. A critical assessment of the utility of fluctuating asymmetry as a biomarker of anthropogenic stress. In: Polak, M. (Ed.), M. (Ed.), Developmental Instability: Causes and ConsequencesDevelopmental Instability: Causes and Consequences . Oxford University Press, New York, pp 415-426.. Oxford University Press, New York, pp 415-426.Leung, B. and Forbes, M.R. 1996. Fluctuating asymmetry in relation to stress and fitness – effects of trait type as revealed by meta-Leung, B. and Forbes, M.R. 1996. Fluctuating asymmetry in relation to stress and fitness – effects of trait type as revealed by meta- analysis. analysis. EcoscienceEcoscience. 3: 400-413.. 3: 400-413.McIntyre, J.W. 1988. McIntyre, J.W. 1988. The Common Loon:Spirit of the Northern LakesThe Common Loon:Spirit of the Northern Lakes , 2nd ed. University of Minnesota Press., 2nd ed. University of Minnesota Press.Moller, A.P. and Swaddle, J.P. 1997. Asymmetry, Developmental Stability and Evolution. Oxford University Press, Oxford. Moller, A.P. and Swaddle, J.P. 1997. Asymmetry, Developmental Stability and Evolution. Oxford University Press, Oxford. New York State Department of Environmental Conservation (NYS DEC), 2007. “Endangered, Threatened and Special Concern Fish New York State Department of Environmental Conservation (NYS DEC), 2007. “Endangered, Threatened and Special Concern Fish & Wildlife Species of NYS.” & Wildlife Species of NYS.” http://www.dec.state.ny.us/website/dfwmr/wildlife/endspec/etsclist.html Polak, M., Polak, M., et Al.et Al. 2004. Genotype-specific responses of fluctuating asymmetry and of preadult survival to the effects of lead and 2004. Genotype-specific responses of fluctuating asymmetry and of preadult survival to the effects of lead and temperature stress in temperature stress in Drosophila melanogasterDrosophila melanogaster. . Environmental Pollution. Environmental Pollution. 127: 145-155.127: 145-155.
Literature Cited
Common Loon
For the purpose of this experiment, the Common Loon (Gavia immer) will be studied. No previous asymmetrical studies have been published on the Common Loon; however other avian species have been studied. These species include the Taita Thrush (Lens et al. 2000), Finches and Chickens (Campo et al. 2006). Previous studies on avian species have been performed to test for the presence of fluctuating asymmetry. Very little work has been done with avian species and directional asymmetry or antisymmetry. The loon has a wide breeding range throughout Northern North America and parts of Europe. North American Loons have a yearly migration pattern that involves summers in northern Canada, the northern US and Greenland, and winters on the east and west coasts of the southern US. Within recent years, large loon die-offs have occurred on the Great Lakes. Many of these die-offs have been confirmed as botulism type E deaths and have scientists struggling with its implications. In New York State, even with recent loon die-offs, the Common Loon is considered a species of special concern (NYS DEC 2007). Species of special concern warrant attention and consideration but current information, collected by various state agencies, do not justify listing the loon as either endangered or threatened (NYS DEC 2007). My study is specifically focusing on asymmetries of migrating loons found on Lake Erie and Lake Ontario during fall 2006.
Why Do We Care?
1) Presence of an asymmetry could indicate an adaptation of the bird. - An adaptation would indicate a direct genetic link to the asymmetry. - If the bird were to exhibit a directional asymmetry, this would indicate an adaptation that explains an aspect of the life history of the species.2) Presence of fluctuating asymmetry may indicate developmental interference. - Developmental interference could be a result of genetic factors, environmental factors, or a combination of both. - This could indicate stressors in the breeding lakes and may warrant further study.3) An asymmetry’s sudden appearance could have implications for conservation. - Any factor that may influence the quality of loon breeding lakes (e.g., deforestation, new home construction, chemical dumping) could create an unstable developmental environment for an embryo by contributing to excess noise and/or stress during development. This interference may prove to cause random fluctuations at the molecular level during development which can lead to the presence of an asymmetry.
Antisymmetry (AS), is considered a random asymmetry. Antisymmetry is considered heritable in the sense that the asymmetry will be passed down to the next generation. However, it is not heritable as to which side the asymmetry will show up on. In other words, while the parent will have an asymmetry and will pass that asymmetry on to its offspring, the chance of the asymmetry being left-sided (sinistral) or right-sided (dextral) is equal (Hallgrimsson and Hall 2005). This too implies that symmetry is somehow broken during development to allow for the asymmetry. However, unlike directional asymmetry, antisymmetry has many scientists puzzled. The mechanism as to how the sided asymmetry is determined is currently unknown.
Antisymmetry
![Fluctuating asymmetry and feather growth bars as ......prospects for reproduction or/and long-term survival with their conspecifics residing in pristine forests [17,18]. However, more](https://static.fdocuments.us/doc/165x107/604553f0894bfe6bfe4f36d1/fluctuating-asymmetry-and-feather-growth-bars-as-prospects-for-reproduction.jpg)
