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EDITS TO EXISTING ARTICLE (DUE MONDAY 11/17):

Here is the link to the article that I edited: https://en.wikipedia.org/wiki/Phylogenetics_of_mimicry

Here is the text that I added to this article:

Imperfect Mimicry

Mimicry is often celebrated as one of the most straightforward examples of evolution by natural selection, however, several cases of imperfect mimicry have been documented. [10] The evolution of imperfect mimicry is poorly understood but is an important phenomenon to research because it can help understand the efficiency of selection as well as the necessity or lack there of within a population. It is poorly understood why selection does not further improve the imperfect mimics and why it allows imperfect mimicry to persist within a population.

One hypothesis suggests that a limitation in a predator’s cognitive ability permits imperfect mimicry. Predators may not be able to use all aspects of the prey’s phenotype to distinguish and edible vs. an inedible species. For example, an edible snake species, L. elapsoides, imperfectly mimics the deadly species, M. fulvius. Although the mimic differs from the model by the order of colorful rings surrounding their body, their phenotypes match in other respects, keeping predators at bay nonetheless. Imperfect mimics evolve only the signals necessary to deceive predators. [11] Furthermore, if the mimicked traits are equal in their level of warning and one of the more salient traits seen within the model, deception will occur. As long as the imperfect mimic is deceiving its predators, the imperfectly mimicked traits will persist into the next generation and natural selection will not occur.[12]

Another hypothesis suggests that mimics using multiple models may evolve imperfect mimicry as an intermediate form, rather than strongly resembling the several models they mimic. A study conducted with the octopus species, T. mimicus, revealed that despite its ability to impersonate a handful of different sea creatures imperfectly, enough confusion within the predators will occur, allowing the mimic to escape an unfavorable situation. [13]

Finally, a study conducted by Vesley et al revealed that the existence of predators and prey within the natural world condition the predators to avoid a certain type of prey and driving the predators to choose from a variety of different prey sources. Previous experience with the unpalatable prey increases the protection of the imperfect mimic, strongly affecting their selective advantage. Also, the model must outnumber its mimic within the natural world because the predator must experience the unpalatable prey more frequently in order to correlate unpleasantness with specific phenotypic traits. [14]

The prevalence of imperfect mimicry shows that natural selection does not always occur without fault. However, as long as the course of evolution increases the frequency of genotypes that produce phenotypes with higher fitness, the imperfections within mimics do not need to be selected against.

FINAL PAPER DRAFT STARTS HERE

Imperfect Mimicry

Evolution by natural selection produces evolutionary changes. Natural selection operates on the phenotypes of individuals, allowing traits correlated with increased population fitness to evolve. Mimicry is one of the greatest examples of evolution by natural selection. Mimicry occurs when different species resemble one another in order to relieve predation pressures, or increase average population fitness. Selecting for traits that are similar to another species can protect one or both of the species involved. Two types of mimicry are known in evolutionary biology—Müllerian and Batesian. Müllerian mimicry exists when an inedible species resemble one another. Batesian mimicry exists when an edible species resembles an inedible species1.

The predation pressures exerted on species affects the coevolutionary process between the involved species. An example of how mimicry and coevolution are linked can be seen in an edible species of salamanders, E. e. xanthoptica and an inedible species of newt, T. torosa that live sympatrically. The newts produce a neurotoxin that many predators associate with the dramatic coloration, driving the salamander species to select for the same traits in hopes of confusing predators and ultimately protecting the salamander species from predation. Although the mimicry seen between these species generally protects both, some predators will occasionally eat the salamanders and the newts, driving the newts to display their toxicity in a different way in the future. Further research on the potential of new selection pressures on the newts could hint at exactly how they are changing their modes of toxicity display and how this change is driving the operation of selection in the salamanders as well, putting these species at a co-evolutionary arms race (Bergstrom et al., 2012).

Although mimicry can show how natural selection can be a powerful force in generating adaptations, some species resemble their model imperfectly, challenging the traditional theory. The evolution of imperfect mimicry is poorly understood but is an important field to research because it can help understand the efficiency of selection and the necessity or non-necessity of selection within a population. The central question to this phenomenon begs: why doesn’t natural selection further improve the imperfect mimics?

One hypothesis suggests that a limitation in a predator’s cognitive ability permits imperfect mimicry. For example, predators may not be able to use all aspects of the prey’s phenotype to distinguish an edible vs. inedible species. A study conducted David Kikuchi and David Pfenning used two snake species to explore this hypothesis. The first snake species, M. fulvius, produces deadly venom. The second snake species, L. elapsoides, is nonvenomous but mimics the phenotype of the deadly snake species, specifically by possessing similar colored rings. However, the nonvenomous snake species’ colored rings are in a different order on their body compared to the venomous species, demonstrating imperfect mimicry. Even though the mimics do not match the ring order of their model, they match in other respects, keeping the imperfect mimicked trait from undergoing selection. Therefore, the nonvenomous snakes have evolved only the signals necessary to deceive predators. This study points to the fact that selection does not occur when the average population fitness is not at risk (Kikuchi et al., 2010).

A team of scientists used the mimic octopus species, T. mimicus, to demonstrate the same hypothesis. The T. mimicus octopus is known to possess an uncanny and unique ability to impersonate other sea creatures, more so than its relatives, suggesting that mimicry may be a secondary adaptation within this species. This octopus species has evolved to imperfectly mimic a venomous sea snake as well as a toxic flatfish. Therefore, this study suggests that “mimics that use multiple models may evolve imperfect mimicry of an intermediate form, rather than multiple strong resemblances” (Huffard et al., 2010). Although the octopus does not resemble its model species identically, it can still cause enough confusion in its predators to be able to escape an unfavorable situation. The mimic actually receives even more protection when it can imitate more than one species. As stated before, evolution by natural selection does not need to occur if the mimicry is enough to allow the species to escape production and foster survivability.

The hypothesis that imperfect mimicry exists because of limitations in the predator’s cognitive ability was also supported in a study conducted by Petr Vesely et. al. This experiment simulated conditions similar to those found in the natural world. Cockroaches were manipulated to imperfectly mimic the red firebug, a species unpalatable to the Great Tit species. The cockroaches were imperfect in color pattern as well as other visual traits. When the morphological traits of a typical red firebug were modified, the cockroaches were attacked more often than the firebug, suggesting that the Great Tits can use other cues such as antennae shape to identify their prey. However, if the traits are equal in their level of warning, the Great Tit will avoid the mimic. Therefore, this study showed that the predator couldn’t actually distinguish an imperfect mimic and their model. More specifically, the Great Tit grouped the differing patterns together as a warning signal, including imperfectly mimicked traits in this group. The results of this study also showed that “the more natural the simulated conditions, the more protected the imperfect mimics.” When predators and prey exist in the natural world, there may be other prey sources available and the predators have already been conditioned to avoid a certain type of prey, mimicked or not. Previous experience with unpalatable prey increases the protection of imperfect mimics; strongly affecting their selective advantage due to the relief of predation pressure (Vesley et al., 2013).

A study conducted by Kazemi et. al. also suggests that predators only learn to use a few noticeable traits of the prey’s appearance to determine if the prey is palatable. When the predators generalized several traits between the models and the mimics, they ignored the less noticeable traits, allowing for imperfect mimicry to exist (Kazemi et al., 2014). A study conducted by Ihalainen et. al. also showed that avian birds in the wild can select for warning signals that are common across unpalatable prey because they have previously encountered these prey (Ihalainen et al., 2008). Another study conducted by Howse and Allen also showed that certain warning traits cause predators to totally avoid or delay their response to prey when the noticeable trait is presented with other irrelevant traits than without. Therefore, as long as the imperfectly mimicked trait is one of the more salient traits of the model, it will be better protected than a novel trait, advancing these phenotypes to the next generation (Howse et al., 1994).

Another hypothesis for the existence of imperfect mimicry is centered on the abundance of models within an environment. In this hypothesis, co-evolution between the model and the mimic occurs at a greater frequency when the model species is present in greater numbers. In order for perfect mimicry to evolve, the model must outnumber its mimic because the predator would have to experience the unpalatable prey more frequently in order to associate the unpleasantness with specific phenotypic traits. When there are very few models for species to mimic, imperfect mimicry is selected for over perfect mimicry (Brower, 1960).

In contrast to the previously explored hypotheses, a study conducted by Dittrich et. al. proposes that humans, not the predator species involved, are the only species able to recognize the imperfections. In this study, pigeons were exposed to wasps and hoverflies, the palatable species that mimics the wasps. Although pigeons do not normally eat insects, they were chosen for this study because they are known to be able to classify insects “in a taxonomically relevant way” due the “highly conservative nature of their visual systems” (Dittrich et al., 1993). However, the pigeons were not able to decipher between the model and the mimic while the scientists conducting this study saw the hoverflies as very poor mimics. Therefore, predator species lower on the evolutionary hierarchy cannot recognize the existence of imperfect mimicry like humans can. Although predator species cannot differentiate between model and mimic species, the mimicked traits yield constant or increased average population fitness, therefore, evolution by natural selection selects for these traits regardless (Dittrich et al., 1993).

Mimicry is observed as the one of the best examples of evolution by natural selection. The prevalence of imperfect mimicry shows that natural selection does not always occur without fault. However, as long as the course of evolution increases the frequency of genotypes producing phenotypes that yield greater reproductive success, the imperfections do not need to be selected against. As the model and mimic species co-evolve, imperfect mimicry can persist. The phenomenon of imperfect mimicry is important to the study of evolution because it can further explain natural selection and put forth novel ideas about imperfect evolution, perhaps leading to solutions of unsolved evolutionary mysteries.

References 1.Dittrich, W., Gilbert, F., Green, P., McGregor, P., & Grewcock, D. 1993. Imperfect Mimicry: A Pigeon’s Perspective. JSTOR 251(133): 195-200.

2.Vesely, P., Luhanova, D., Praskova, M., & Fuchs, R. 2013. Generalization of Mimics Imperfect in Colour Patterns: The Point of View of Wild Avian Predators. The International Journal of Behavioral Biology 119: 138-145.

3.Kikuchi, D., & Pfenning, D. 2010. Predator Cognition Permits Imperfect Coral Snake Mimicry. The American Naturalist 176(6): 830-834.

4.Huffard, C., Saarman, N., Hamilton, H., & Simison, B. 2010. The Evolution of Conspicuous Facultative Mimicry in Octopuses: An example of Secondary Adaptation? Biology Journal of the Linnean Society 101: 68-77.

5. Brower, J. 1960. Experimental Studies of Mimicry. IV. The Reactions of Starlings to Different Proportions of Models and Mimics. The American Naturalist 94(877): 271-282.

6.Kazemi, B., Gamberale-Stille, G., Tullberg, B. S., & Leimar, O. 2014. Stimulus Salience as an Explanation for Imperfect Mimicry. Current Biology 24: 965-969.

7.Ihalainen, E., Lindstrom, L., Mappes, J., & Puolakkainen, S. 2008. Can Experienced Birds Select for Mullerian Mimicry? Behavioral Ecology: 362-368.

8.Howse, P. E., & Allen, J. A. 1994. Satyric Mimicry: The Evolution of Apparent Imperfection. The Royal Society 257(1349): 111-114.

9.1Bergstrom, C. T., & Dugatkin, L. A. 2012. Evolution. 635-637.

Wikipedia Assignment (due Oct. 1st):

Article I commented on: https://en.wikipedia.org/wiki/Talk:Phylogenetics_of_mimicry

Three ways in which this article could be improved: 1. This article is formatted as one large paragraph and may need to be broken up into sections (i.e. an introduction section, a detailed section on the types of mimicry with examples, and a section on past and current research on this topic) 2. A description of imperfect mimicry would enhance this article because it will show "both sides of the coin" on the topic of mimicry--i.e. it will show that natural selection does not always perfect advantageous traits but does so enough to allow increased fitness and survival within the population at hand. 3. This article does not have enough details about the current and past research done on the topic of mimicry. Information from research articles will enhance the viewers understanding of mimicry and how it manifests itself in the natural and experimental settings. Maddieroman7469 (talk) 23:23, 1 October 2014 (UTC)

Text I added:

Imperfect Mimicry: Mimicry is often celebrated as one of the most straightforward examples of evolution by natural selection, however, several cases of imperfect mimicry have been documented. [10] 10. ^Wilson, J., Jahner, J., Williams, K., & Forister, M. 2013. Ecological and Evolutionary Processes Drive the Origin and Maintenance of Imperfect Mimicry. PLOSONE 8(4):1.

Wikipedia Assignment 1:

Topic: What evolutionary processes are driving imperfect mimicry? Mimicry is used to show how natural selection can be a powerful force in generating adaptations. However, some species resemble their model imperfectly, challenging the traditional theory. Why doesn’t natural selection further improve imperfect mimics?

Annotated bibliography:

1.Vesely, P., Luhanova, D., Praskova, M., & Fuchs, R. (2013). Generalization of Mimics Imperfect in Colour Patterns: The Point of View of Wild Avian Predators. The International Journal of Behaviorual Biology, 119, 138-145.

This study simulates a natural situation by testing responses of the Great tit to imperfect mimics of the red firebug. Previous studies show that Great tits avoid red firebugs in a natural setting. The mimics, specifically cockroaches, were imperfect in color pattern as well as other visual traits. For example, the characteristic rounded spots found on the red firebugs were modified. When the morphological traits were modified, the cockroaches were attacked more often than the firebug, which suggests that the birds could use other cues such as antennae shape to identify their prey. However, if these traits are equal in their level of warning, the Great Tit will avoid this type of prey. Therefore, the study showed that tits are not able to discriminate between perfect and imperfect mimics. This article is helpful to my research topic because it may show that natural selection is not a highly specific process but occurs at a level that is just enough to allow the species to survive.

2.Pfenning, D., & Kikuchi, D. (2010). Predator Cognition Permits Imperfect Coral Snake Mimicry. The American Naturalist, 176(6), 830-834.

This article asks the question “why are imperfect mimics not further improved by natural selection?” The scientists in this study designed a field experiment to determine whether limitations in predator cognitive abilities can explain imperfect coral snake mimicry. Nonvenomous scarlet king snakes mimic deadly coral snakes by possessing brightly colored rings around their bodies. However, the rings differ in order. They found that good mimics that differed from the model in ring order but very similar in other ways were not under selection to resemble their model more closely. The article describes hypotheses to support their findings. For example, it was hypothesized that predators may generalize aposematic signals of models to an increasingly high probability of incorrectly identifying prey as mimics grow more similar to models in phenotype. The risk taken by predators is not favored. The differences between the model species and mimicked species might reflect differing starting points in mimicry evolution. Also, selection might not favor a change in ring order if mimics use this trait for mate recognition. As long as the mimicry exploits predator cognition, there will not be strong selection on mimics to resemble their models.

3.Huffard, C., Saarman, N., Hamilton, H., & Simison, B. (2010). The evolution of conspicous facultative mimicry in octopuses: An example of secondary adaptation? Biology Journal of the Linnean Society, 101, 68-77.

The “Mimic” octopus, T. mimicus, imperfectly mimics the venomous sea snake by intensifying high-contrast body color pattern. The visual defenses of the octopus can be maintained if they are good enough to cause pause during the speed versus accuracy decisions of the predator. This confusion seen in the predator may allow these octopuses to escape predation. Therefore, although the mimicry is imperfect, it may cause enough disruption in the predator to allow the prey to escape. Again, this research points to the fact that mimicry process due to natural selection is not highly specific.

4.Wilson, J., Jahner, J., Williams, K., & Forister, M. (2013). Ecological and Evolutionary Processes Drive the Origin and Maintenance of Imperfect Mimcry. PLOSONE, 8(4), 1-7.

This research article aimed to test the several hypotheses regarding the evolution of imperfect mimicry. The evolutionary context, such as body size and mimicry ring, of multiple groups was investigated. Pictures of 38 mimics and 3 models were shown to volunteers. The mimics were hoverflies and the models were wasps, honeybees, and bumblebees. The volunteers were asked to rank each fly on a scale of 1 (very poor mimic) to 10 (excellent mimic). Their analyses suggest a complex mixture of evolutionary and ecological context influences the evolution of imperfect mimicry. They found that community diversity is among the strongest predictors of mimetic fidelity. This study may show that human perception of mimicry may be what is driving the phenomenon of imperfect mimicry.

5.Ihalainen, E., Lindstrom, L., Mappes, J., & Puolakkainen, S. (2008). Can experienced birds select for Mullerian mimicry? Behavioral Ecology, 362-368.

In this experiment, Great tits were caught from their feeding sites and housed in plywood cages for the duration of the experiment. The experimenters created two aposematic prey types, perfect and imperfect mimics. Birds with prior experience on a warning signal selected against aposematic prey with an unfamiliar signal. Imperfect mimics had a higher predation risk than the familiar perfect mimics. This is the first experiment that showed the cost of imperfect mimicry, alluding to the fact that natural selection has not improved the flaw in current populations.