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Evolution of Mullerian Mimicry

Balogh A. et al., 2009. Feature Theory and the Two-step Hypothesis of Müllerian Mimicry Evolution. Evolution; International Journal of Organic Evolution [Internet]. [2010 Mar 1, cited 2014 Sep 	14] 64(3): 810-22. Available from: http://web.a.ebscohost.com.proxy.lib.ohio-	state.edu/ehost/pdfviewer/pdfviewer?sid=4a3720e7-1f96-4c16-8446-	289e026e4373%40sessionmgr4001&vid=1&hid=4212

This article is very useful because it underlines the basic process of the evolution of Mullerian Mimicry. Predator Psychology is investigated which is a unique but promising approach. Simulations were carried out so as to observe Mullerian Mimicry in as controlled a way as possible. This article is peer reviewed. The fact is approaches evolution from the predator's perspective is novel and useful. Research is backed up with large amounts of data and statistics.

Beatty CD, Beirinckx K, Sherratt TN. 2004. The Evolution of Müllerian Mimicry in Multispecies 	Communities.. Nature [Internet]. [2004 Sep 2, cited 2014 Sep 14] 431(7004): 63-6. Available 	from: http://web.b.ebscohost.com.proxy.lib.ohio-state.edu/ehost/pdfviewer/pdfviewer? sid=5c24f528-92b1-4a91-83d0-88bc56d7c525%40sessionmgr111&vid=1&hid=126

This article is unique in that it uses a human model to investigate the methods of Mullerian Mimicry. This is useful in that the data is easy to interpret and appeals to psychology as well as evolution. The article is peer reviewed. The study is easily replicable. Selection, or the lack thereof, of unpalatable species encourages extreme selective advantage which highlights the evolutionary context as well.

Baxter S. et al., 2008. Convergent Evolution in the Genetic Basis of Müllerian Mimicry in Heliconius 	Butterflies. Genetics [Internet]. [2008 Nov, cited 2014 Sep 14] 180(3): 1567-77. Available from: 	http://web.a.ebscohost.com.proxy.lib.ohio-state.edu/ehost/pdfviewer/pdfviewer?sid=0f3ab788-	4e19-475b-8dad-0285feb915ab%40sessionmgr4004&vid=1&hid=4212

This article discusses a specific species of butterfly which is a common model looked at to describe Mullerian mimicry. It also looks at geographic location as a factor. The study uses genetic mapping and phenotypic analyses to explore the understanding of the phenomena more deeply. This is important because the genetic basis is the epitome of evolution. This one is peer reviewed too.

Llaurens V. et al., 2013. The Effect of Dominance on Polymorphism in Müllerian Mimicry. Journal of 	theoretical biology [Internet]. [cited 2014 Sep 14] 337: 101-10. Available from: 	http://www.sciencedirect.com.proxy.lib.ohio-state.edu/science/article/pii/S0022519313003780

This article looks at dominant traits in populations exhibiting Mullerian mimicry and how they affect polymorphisms. Allele frequencies change as a result of this mimicry pattern which is very useful from an evolutionary standpoint. This article has been peer reviewed. Predator response is also investigated which is important data. The data is also backed by math.

Sherratt T. 2008. The Evolution of Müllerian Mimicry. Die Naturwissenschaften [Internet]. [cited 2014 	Sep 14] 95(8): 681-95. Available from: http://journals.ohiolink.edu.proxy.lib.ohio-	state.edu/ejc/pdf.cgi/Sherratt_Thomas_N.pdf? issn=00281042&issue=v95i0008&article=681_teomm

This article discusses the evolution of our understanding of Mullerian Mimicry over the years. It also investigates studies that have been done in support of the original theory. It also discusses the relationship with other forms of mimicry. This is useful because it very closely relates to my topic and approaches is from an evolutionary point of view. There is a large amount of information in this article and has been peer reviewed and is backed up by many references.

https://en.wikipedia.org/wiki/M%C3%BCllerian_mimicry

Suggestions[edit] 1. Include experimental data as support. 2. Change the tone of some sections into a more professional one - "Surely if they could all get together and agree on a common warning signal." 3. Provide more examples of non-visual Mullerian mimicry since page mentions that this type of mimicry can affect any sense but is mostly about visual cues and a mention of an auditory one.

It is commonly believed that males would be more likely to co-mimic than females (generally being the choosier sex) but in the case of sexually dimorphic species, females are the ones that tend to be mimetic.[7]

Sherratt, T. (June 10, 2008). "The Evolution of Müllerian Mimicry.". Die Naturwissenschaften: 681-695.

Contribution (https://en.wikipedia.org/wiki/M%C3%BCllerian_mimicry):

A plausible explanation of the occurrence of Mullerian mimicry is known as the "two step hypothesis." This concept states that first, a large mutational leap occurs naturally and spontaneously to establish an approximate resemblance of one species to another species (the “model”). For this occurrence to be considered a part of a Mullerian mimicry model, the mimic and model species must both separately cause an unfavorable reaction in their shared predator. Once this leap has occurred, fine tuning then proceeds somewhat gradually in the mimic species so as to approach greater similarity to the model, albeit very slowly. This aposematic model (distinctive patterning linked to undesirable trait) must already exist in the model species. Both species will share in the benefits of a superior defense mechanism by way of patterning changes; generalized distrust of this pattern develops quickly in predators and has a large basis of reinforcement. The extent of a species' likelihood of being mimicked is considerably higher when there is only one key feature involved in a predator's generalization of undesirability. Once this trait (feature) spontaneously mutates in an individual it must also be able to be passed on to subsequent generations. After a significantly large number of generations have passed, it should eventually become fixated. In contrast, “non-feature traits,” (traits that do not play a role in predator recognition and distinction) do not affect the predator's selection of the mimic. Because individuals with mutated non-feature traits do not share a significant resemblance to the model in a way that is distinctive to the predator, the mimic containing this type of mutation is more likely to be eaten than mutants containing feature-trait resembling mutations. Therefore, the genetic mutation for the non-feature trait will likely not be passed on even if it confers an evolutionary advantage (unrelated to predator selection). The greatest selective pressure in the system is the propensity of the predators to avoid certain recognized patterns and when the mimic species eventually presents the trait in an individual, this trait is significantly more likely to be conserved and passed on to the individual's progeny. The strength of the influence of predator selection will remain strong and is much more likely to continue to permit the passing along of a feature-trait; although it is in no way guaranteed, it is highly plausible that eventually the whole species comes to share this trait which defines them as mimics.

FINAL DRAFT STARTS HERE:

Mullerian mimicry is the selective evolution of two (or more) species in such a way that they come to share physical attributes – namely patterning – that makes distinguishing them difficult for shared predators. These species evolve these similarities independently without interbreeding; this is referred to as convergent evolution. The species that evolve these similar traits simultaneously benefit because their predators learn and are continually reinforced to associate the phenotype (pattern) with a negative effect. This is similar to another naturally occurring form of mimicry which is referred to as Batesian mimicry. The key difference is that in Mullerian mimicry, both of the co-evolving species are poisonous or unpalatable to their predators. With Batesian mimicry, one of the two co-evolving species is not poisonous and is, in essence, “piggy-backing” on the adaptation of the species that actually is poisonous to their predators. Mullerian mimicry works very well and appears sensible in concept but the evolutionary mechanisms that lead to these understandings encourages study and proves very difficult to definitively explain its frequent occurrence in nature. Studies and analyses attempt to explain this phenomenon with somewhat different and similarly rooted ideas. One such plausible explanation of the occurrence of Mullerian mimicry that is well supported is the two step hypothesis. This concept states that first, a large mutational leap occurs naturally and spontaneously to establish an approximate resemblance of one species to another species (the “model”). For this occurrence to be considered a part of a Mullerian mimicry model, the mimic and model species must both separately cause an unfavorable reaction in their shared predator. Once this leap has occurred, fine tuning then proceeds somewhat gradually so as to approach greater similarity to the model, albeit very slowly. This aposematic model (distinctive patterning linked to undesirable trait) must already exist in an initial species which opens the door to the possibility of mimicry. Once mimicked, another species will share in the benefits of a superior defense mechanism by way of patterning changes; generalized distrust of this pattern develops quickly in predators and has a large basis of reinforcement. The extent of a species' likelihood of being mimicked is considerably higher when there is only one key feature involved in a predator's generalization of undesirability. Once this trait (feature) spontaneously mutates in an individual it must also be able to be passed on to subsequent generations. After a significantly large number of generations have passed, it should eventually become fixated – scenario where the trait is possessed by the entire population. In contrast, “non-feature traits,” which are traits shared by a model and their mimic but do not play a role in predator recognition and distinction, do not affect the predator's selection of the mimic. Because individuals with mutated non-feature traits do not share a significant resemblance to the model in a way that is distinctive to the predator, the mimic containing this type of mutation is more likely to be eaten than mutants containing feature-trait resembling mutations. Therefore, the genetic mutation for the non-feature trait will likely not be passed on even if it confers an evolutionary advantage (unrelated to predator selection). The greatest selective pressure in the system is the propensity of the predators to avoid certain recognized patterns and when the mimic species eventually presents the trait in an individual, this trait is significantly more likely to be conserved and passed on to the individual's progeny. The strength of the influence of predator selection will remain strong and is much more likely to continue to permit the passing along of a feature-trait; although it is in no way guaranteed, is is highly plausible that eventually the whole species comes to share this trait which defines them as mimics. Although not nearly as common as appearance based traits, most commonly color and pattern, olfactory and auditory cues have the potential of being mimicked in a similar manner. When it comes to model species were multiple feature traits exist and are required by their predator for recognition; these multiple traits must be evolved simultaneously in the mimic species. In a scenario like this, Mullerian mimicry occurs incredibly infrequently. It is extremely unlikely that a mimic would evolve multiple traits in a very short window of time as would be required for predator recognition and undesirability; this also leads to a lack of selective advantage and higher probability of trait elimination. The only scenario where the evolution of multiple feature traits is plausible is where predators are very generalizing in their selection of mimics that have simultaneously evolved multiple traits that loosely resemble the multiple feature traits in the model species but are not necessarily identical. This allows for the mutations to occur and slowly accumulate/fine-tune just like in the single feature-trait model but over an even longer period of time and across the many traits. Although plausible, this scenario is highly unlikely as there are many conditions that must be met and in nature, selection is rarely so forgiving. (Balogh et al. 2009) One facet that really encourages co-evolution of two similar, toxic species is their persistence among a range of different prey species that share a common predator. This placement intensifies selection of prey that resemble one another since it encourages the predator to learn to avoid a specific color or pattern instead of many and that they then have options of other, non-defended prey to choose from in place of the undesirables. The concept of simplified decision making strongly supports the plausibility of how a rare but shared trait among two species becomes much more common and eventually fixed. This Mullerian mimicry is much more likely to arise in a multispecies community as a result of limited 'memory' in predators. It is usually the case that a predator will attack a number of each type of identifiable prey so as to come to an understanding of what recognizable colors or patterns are to be avoided in the long run to maximize the profitability of future predation. As supported by information mentioned in the feature theory hypothesis, mimicry of the patterns of a prey species recognized as undesirable will improve the mimics chance of survival and encourage the genetic information's proliferation among the species. This multispecies phenomenon provides an even greater degree of selective advantage for the mimicking species when compared to smaller populations where there are only two species that share a predator; fixation of a mimicked trait is much more likely in the multispecies community than in a two-prey per predator scenario. (Beatty, Beirinckx and Sherratt 2004) Evidence of Mullerian mimicry is most commonly recognized among insects (being generally highly preyed upon) but birds and fish have also been investigated and discovered to follow similar evolutionary developments. Birds of the Pithui genus provide an excellent model of Mullerian mimicry. Many species of this genus produce toxins in their skin and feathers that protects them from ectoparasites (as well as human hunters). A phylogenetic tree was constructed so as to analyze the relationships of the many species investigated. This tree shows a physical and graphical representation of how these species are interrelated. This tree also led to the conclusion that the divergence of these species occurred over a period of roughly 3.5-4.6 million years ago. This estimation was made possible by genetic screening and subsequent mutation rate calculations. Not all of the similar species support convergent mimetic evolution, but in the case of north-coast and West-Papuan Island species, convergent evolution is supported by an assumed loss of a similar phenotype in one clade (selection of species that share a common ancestor) and a subsequent re-emergence of a similar phenotype in a subspecies later on down the line. This re-emergence of patterning supports Mullerian mimicry. Despite the fact that the species lost the phenotype, selective pressures encouraged it to be regained Since the species does indeed have the toxin production shared by similarly patterned toxic species, Mullerian mimicry is the most likely explanation. This is further supported by the testing that was done to investigate the likelihood of a somewhat different shared ancestry that excluded the removal and re-emergence of this phenotype; statistical analysis refuted this possibility. (Dumbacher and Fleischer 2001) The concept of Mullerian mimicry can be supported by the Red Queen Hypothesis, which comments on co-evolution from the standpoint that it occurs in such a way as to balance survival and selection between opposed species. Despite how this hypothesis is typically cited in reference to the predator-prey relationship itself, the two similar, co-evolving species are somewhat opposed to one another in their survival against their shared predators. It appears somewhat counter-intuitive that species that evolve to resemble one another would be “opposed” since it would appear that they both benefit. However, the recognition of their predators to certain phenotypes drives selection to favor those that bear that phenotypic resemblance. Those that are not immediately recognized as undesirable to their predators are much more likely of being eaten, or at the very least being killed in the process. Phenotypes resembling the previously recognized undesirables will be selected for in that they are more likely to survive and reproduce whereas the unrecognized are more likely to be killed and therefore not pass their genes on 5to the next generation. This balance of encouragement of a recognized appearance is what drives the evolution of the mimicry itself. The mimicking species has to 'evolve as fast as it can' in order to keep up with the model species. Not much hard proof for Mullerian evolution exists as most explanations are proposed from a human understanding of likely cause but are in no way absolute. As such, the theories and explanations cited are insights into animal behavior and evolution. Mullerian mimicry is a frequently observed but not entirely understood facet of evolution. Many insightful suggestions have been posited that generally provide accurate representation of gathered data. The theories have come a long way since the concept's first inception and over the coming years with new technological advancements, the understanding of the evolution of Mullerian mimicry is itself an evolving process.