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

The negative correlation between the amount of mimics and the “survivability” of both species involved[7]. This suggests that it is reproductively beneficial for both species if the number of models outnumber the mimics; this increases the negative interactions between predator and prey.

Some insight into the evolution of mimetic color mimicry in Lepidoptera in particular can be seen through the study of the Optix gene. The Optix gene is responsible for the Heliconius butterflies signature red wing patterns that help it signal to predators that it is toxic. By sharing this coloration with other poisonous red winged butterflies the predator may have pursued previously the Heliconius butterfly increases its chance of survival through association. By mapping the genome of many related species of Heliconius butterflies “show[s] that the cis-regulatory evolution of a single transcription factor can repeatedly drive the convergent evolution of complex color patterns in distantly related species…” [8]. This suggests that the evolution of a non-coding piece of DNA that regulates the transcription of nearby genes can be the reason behind similar phenotypic coloration between distant species, making it hard to determine if the trait is homologous, meaning that it evolved in both species because it existed in a previous ancestor, or that it is convergent in that both species came to a similar phenotypic expression through their own means and mutations.

Viceroy butterflies and monarchs (admiral butterflies) have often been called Batesian mimics; however, this is not the case as both are poisonous which makes them Müllerian mimics. Extensive mitochondrial DNA analysis of admiral butterflies has led to the discovery that the viceroy is the basal lineage of two western sister species in North America. The variation in the wing patterns are thought to precede the evolution of toxicity therefore challenging the hypothesis that the toxicity of the admiral butterflies is a conserved characteristic from a common ancestor. This explanation suggests that because some of the species of admiral butterflies that evolved after the node split from the viceroy lineage are not poisonous but look similar to their ancestor, the propensity for chemical defense is an analogous adaptation (an example of convergent evolution) that evolved separately after the species developed different phenotypic wing patterns.

Final Draft
The Evolution of Color Mimicry in Lepidoptera

Pretending to be something you aren’t in order to survive; it’s a common theme throughout literature, history, and even evolution. Like Viola in Shakespeare’s Twelfth Night pretending to be a man in order to work a steady job or Joan of Arc disguising herself as a male soldier in order to join the French army, evolution has helped disguise entire species as another in order to increase their rate of survival and consequently their reproductive success. One of the driving forces behind evolutionary changes and variation within a species is “… natural selection, a gradual process in which forms that are better suited to their environment increase in frequency in a population over sufficiently long periods of time.” (Bergstrom 2012). Natural selection is nature’s way of selecting against phenotypes that are at a greater disadvantage than other individuals of the same species; as a result, the individuals that are more adapted to their environment have a greater opportunity to reproduce, increasing their reproductive fitness. Overtime, natural selection and other evolutionary forces have worked in tandem to create entire species that are not what they seem. These evolutionary forces created mimics such as those found in species of Lepidoptera or what are commonly known as butterflies and moths. How did this phenomenon create phynotypically similar toxic butterfly species and how could this be evolutionarily beneficial?

There are two forms of mimicry in the natural butterfly world: Batesian mimicry and Müllerian mimicry. Batesian mimicry, termed by European naturalist Henry Bates in 1862, occurs when a nonpoisonous species mimics or resembles a poisonous or unpalatable species (“mimicry” 2014). Through this false camouflage, the nonpoisonous species is able to trick potential predators into thinking that they too are poisonous. Although this form of mimicry is based on the supposition that the predators have had previous experience with the poisonous species, it still offers some benefit to the survival of the mimic (Bergstrom 2012). In the past, the viceroys (Limenitis archippus) were considered to be Batesian mimics, suggesting that they were the palatable species of the viceroy monarch pair; however, according to a study done by David B. Ritland, “viceroys are as unpalatable as monarchs...” (Ritland et al. 1991). This discovery was revolutionary as it attributed one of the primary textbook examples of Batesian mimicry to Müllerian mimicry.

Müllerian mimicry was termed in 1878 by German zoologist Fritz Müller (“mimicry” 2014). In this particular form of mimicry, more than one unpalatable species develop similar phenotypes that reinforce poisonous signaling to predators (Bergstrom 2012). By having more than one extant species that are poisonous and phenotypicly similar, Müllerian mimicry benefits all the species involved. The more individuals in a population that exhibit coloring that signals they are poisonous, the more likely a predator will learn quickly that these individuals are not palatable. If a bird encounters one of the poisonous Lepidoptera and finds it unpalatable the bird will not likely pursue others that look similar to the inedible individual. This, in turn, increases the collective reproductive fitness of all the individuals who share phenotypic similarities with the first poisonous individual encountered. However, is Müllerian mimicry really beneficial to all the species involved, or do some species gain an advantage over the others?

Individuals such as Durrell Kapan were determined to prove that Müllerian mimicry not only existed in nature, but that it was beneficial to all the species involved. Kapan sought to determine whether or not individual butterflies that shared the warning coloration with other poisonous individuals had a better chance of survival than those that did not. Kapan was able to test his theory by releasing three different types of toxic butterflies with differing wing patterns, and recording when they were seen or captured by predators. He hypothesized that individuals that did not share common wing patterns with other poisonous species would be more likely to be pursued and eaten by predators. In the end, Kapan found that his experiment “shows that Müllerian mimicry with several co-models generates geographically divergent selection, which explains the existence of polymorphism in distasteful species with warning coloration.” (Kapan 2001). This means that although some mimics may live in different environments due to possible allopatric speciation caused by geographic or spatial separation barriers including distance, they may still look similar. These separated species may express Müllerian mimicry because of possible predator overlap or because they are under similar natural selection pressures.

Would Müllerian mimicry start to mirror the effects of Batesian mimicry if the two species involved in the co-mimicry relationship varied in their level of toxicity? In Batesian mimicry, if the mimic species (the nonpoisonous species) out numbers the model species (the poisonous species), both species suffer. As more predators encounter nonpoisonous look-a-likes than model individuals they are less apt to have a bad experience and will therefore continue to pursue phenotypicaly similar individuals, reducing both species’ reproductive success. Eria Ihalainen et al. sought to determine if this also applied to Müllerian mimicking species with differential toxicity levels. By measuring how birds reacted to food with similar and dissimilar shapes drawn on it with differing levels of palatability, they were able to determine that there may in fact be a connection between availability, taste, and color. More surprisingly, they concluded that there may be other factors that need to be taken into account in order to explain all the differential consumption across species. Overall, it was determined that there seemed to be a negative correlation between the amount of mimics and the “survivability” of both species involved (Ihalainen et al. 2008). This suggests that it is reproductively beneficial for both species if the number of models outnumber the mimics; this increases the negative interactions between predator and prey. As a result, the lifespan, survivorship, and reproductive success of both species would increase. But even with the benefits to reproductive success how did Müllerian mimicry become part of the Lepidopteron world?

The admiral butterflies (genus Limenitis) of North America in particular are great representations of Müllerian mimicry and Batesian mimicry. When existing in close proximity to one another, interbreeding and hybridization zones occur (Mullen et A. 2006). This suggests that the species involved may be part of a ring species or individual species that can breed with neighboring individuals but may not be able to breed with other individuals that their neighboring species can. This can create a hybridization zone, a blurred boundary environment with large amounts of hybrid individuals that are the offspring of a pairing between parents with differing phenotypes. Any differentiation and variation that exists within the admiral species may be relatively new as the species are not yet reproductively exclusive and may never be. But what does this have to do with Müllerian mimicry? If the individual species among admiral butterflies are closely related then this could explain the phenotypic resemblance between species resulting in their Müllerian co-mimic relationships. After extensive mitochondrial DNA analysis of many types of admiral butterflies, evolutionist Sean P. Mullen and his colleagues have found that among the types compared the viceroy is the basal lineage or base common ancestor of two western sister species in North America. Mullen then explains that variation in the wing patterns are thought to precede the evolution of toxicity therefore challenging the hypothesis that the toxicity of the admiral butterflies is a conserved characteristic from a common ancestor. This hypothesis is supported by the basal position of the Viceroy under the understanding that the development of this toxicity developed after it evolved a similar coloration to that of the Monarch (Mullen et al. 2006). This explanation suggests that because some of the species of admiral butterflies that evolved after the node split from the viceroy lineage are not poisonous but look similar to their ancestor, the propensity for chemical defense is an analogous adaptation (an example of convergent evolution) that evolved separately after the species developed different phenotypic wing patterns. An analogous adaptation is a trait that evolves in more than one species that are not ancestrally related usually as an answer to a common problem shared by both species. It could be possible that the selection for different mimetic wing patterns may have contributed to some of the admiral butterfly speciation. Any further speciation that developed after the wing pattern variation may be a result of positive assortive mating in which individuals are more likely to mate with individuals with phenotypes similar to their own.

According to H. Fredrick Nijhout, many scientists have tried to discover what causes Lepidopteran color mimicry on the genomic level and what conditions are needed to cause more than one species to evolve the same signaling coloration (Nijhout 1994). Seventeen years later, Robert Reed and his colleagues located one of the major genes that contribute to the variation found within the Heliconius butterflies. This single gene, the Optix gene, is responsible for the Heliconius butterflies signature red wing patterns that help it signal to predators that it is toxic. By sharing this coloration with other poisonous red winged butterflies the predator may have pursued previously the Heliconius butterfly increases its chance of survival through association. By mapping the genome of many related species of Heliconius butterflies, Reed and his colleagues were able to, “show that the cis-regulatory evolution of a single transcription factor can repeatedly drive the convergent evolution of complex color patterns in distantly related species…” (Reed et al. 2011). This suggests that the evolution of a non-coding piece of DNA that regulates the transcription of nearby genes can be the reason behind similar phenotypic coloration between distant species, this makes it hard to determine if the trait is homologous, meaning that it evolved in both species because it existed in a previous ancestor, or that it is convergent in that both species came to a similar phenotypic expression through their own means and mutations.

There is still much to be learned about how Müllerian mimicry affects the species involved. Most attribute this unusual relationship to very strong natural selection and a very powerful representation of how sharing signaling codes with other individuals may be beneficial. By sharing phenotypic similarities with other species that are also unpalatable to predators, a species’ survival and reproductive success greatly increases allowing them to reproduce and pass their genetic data into future generations. Whether this particular form of shared signaling developed through convergent or homologous evolution, the taste, color, and availability of the species all come in to play when determining the survivability rates of the species involved. In order to better show their toxicity, Müllerian co-mimics have evolved to share the signaling coloration of other poisonous Lepidoptera. So rather than pretending to be something they are not like the mimics in Batesian mimicry, Müllerian co-mimics instead don the colors of their toxicity in an attempt to survive.

Refrences

Bergstrom, C.T, Lee A. Dugatkin. 2012. Evolution. New York: Norton.

Ihalainen, E., Lindstrèom, L., Mappes, J., & Puolakkainen, S. 2008. Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Mèullerian co-mimics. Behavioral Ecology and Sociobiology, 62, 8, 1267-1276.

Kapan, D. D. 2001. Three-butterfly system provides a field test of müllerian mimicry. Nature, 409, 6818, 338-40.

Mullen, S. P. 2006. Wing pattern evolution and the origins of mimicry among North American admiral butterflies (Nymphalidae: Limenitis). Molecular Phylogenetics and Evolution, 39, 3, 747-758.

"mimicry". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2014. Web. 27 Oct. 2014

Nijhout, H. F. 1994. Developmental perspectives on evolution of butterfly mimicry. Bioscience, 44, 3.

Reed, R. D., Papa, R., Martin, A., Hines, H. M., Counterman, B. A., Pardo-Diaz, C., Jiggins, C. D., McMillan, W. O. 2011. optix drives the repeated convergent evolution of butterfly	wing pattern mimicry. Science, 333, 6046, 1137	41.

Ritland, D.B., Brower, L.P. 1991. The Viceroy Butterfly is not a Batesian Mimic. Nature, 350, 497-498

Talk Section + Changes
Article: https://en.wikipedia.org/wiki/M%C3%BCllerian_mimicry

Three ways the article could be improved:

1. In the second paragraph where it says “Occasionally, individuals of the predatory third species will encounter one or the other type of noxious prey, and thereafter avoid it.” The author might want to take out the word third; It doesn’t really add anything to the article and I found it confusing.

2. There is no conversation in this article about how Müllerian mimicry may have developed from an evolutionary standpoint; maybe an inclusion of the particular genes that have been found to be the reason behind specific coloration in the mimicry world such as the Optix gene in Heliconius butterflies or another example.

3. It may be beneficial to include that some species of butterflies and such become polymorphic and mimic multiple models as a way to spread out the amount of mimics so that there is greater ratio of models to mimics (co-mimicry); increasing fitness of both populations compared to if all mimics followed the same model. If there were too many mimics in the population there would be a decrease in predators suffering negative effects of eating the poisonous models and therefore both the models and mimics would have a higher chance of being eaten.

New sentence and citation added to the main page:

Recent research has found that there may be more than just taste and population size that affect Müllerian mimetic relationships. For example: co-mimicry, a mutualistic relationship that occurs when the mimicking population is polymorphic and resembles more than one model, therefore keeping the ratio of mimic to model individuals for any particular coloration low, increasing overall fitness for both parties.

Ihalainen, E., Lindstrèom, L., Mappes, J., & Puolakkainen, S. (January 1, 2008). Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Mèullerian co-mimics. Behavioral Ecology and Sociobiology, 62, 8, 1267-1276.

Topic: The evolution of color mimicry in butterflies.

Annotated Bibliography

Ihalainen, E., Lindstrèom, L., Mappes, J., & Puolakkainen, S. (January 1, 2008). Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Mèullerian co-mimics. Behavioral Ecology and Sociobiology, 62, 8, 1267-1276.

In this article, scientists conduct a study to better understand exactly what benefits the butterflies get by mimicking their poisonous counterparts. They used a study that not only controlled the abundance of both the model and mimicking food items and different exposures to the birds they used as predators. They hoped to determine whether or not it was detrimental to both models and mimics for the mimicking butterflies to be more reproductively successful than their model counterparts and therefore making the coloration patterns less useful against predators. This has a lot of information that is not necessarily needed but it may be beneficial. It tries to see if there is in fact a mularian benefit to the model mimicking. Although this does not use actual butterflies as the prey it is designed to see what would happen in reality. This might be a bit of a stretch and I wonder if there is any smell associated with the chemicals that they soaked the unpalatable almonds in that may have altered the data results.

Kapan, D. D. (January 1, 2001). Three-butterfly system provides a field test of müllerian mimicry. Nature, 409, 6818, 338-40.

This particular article focuses on whether or not it is actually beneficial for the model species to be involved in mullerian mimicry by being mimicked by other species. It seeks to explain that through natural selection against those non mimicking butterflies, those that mimic the poisonous species are selected for and this actually helps the fitness for the poisonous butterflies as well. Much of this particular fieldwork was done to correct and account for what the author saw as flaws in other previous works, particularly concerning where the butterflies for the experiment came from, how they were released, and how many times they were released. This article ends with the explanation that the results prove that it is beneficial for there to be co-models rather than one type because this decreases the amount of any one particular mimic that, if eaten often could fail to act as a warning to predators anymore.

Mullen, S. P. (June 1, 2006). Wing pattern evolution and the origins of mimicry among North American admiral butterflies (Nymphalidae: Limenitis). Molecular Phylogenetics and Evolution, 39, 3, 747-758.

This article focuses on three possible reasons behind there independent origins of mimicry. It doesn’t only talk about admiral butterflies but also the mimicry of viceroy-monarchs as well. This paper is really genetics heavy and talks about the possibility of mitochondrial connected evolution of wing color mimicry. There is also a nice breakdown of the lineages that evolved from one another and split off from a common ancestor. What may be the most useful in this particular article is the last paragraph or so that explains that this dichotomy and divergent co-mimicry could in the future cause speciation.

Nijhout, H. F. (March 1, 1994). Developmental perspectives on evolution of butterfly mimicry. Bioscience, 44, 3.

This article is less specific than the Reed article about Optix but the general overviews are really informational as to how and why scientists first started looking into the evolutionary biology behind mimicry in butterflies. It explains that rather than a lot of genes at different locations having small effects on the color of the wings of a butterfly it may be subject to a small amount of genes having an incredibly large impact. This article also has information that may be useful concerning the development and evolution of the genes involved in wing coloration, the wing patterns of butterflies and comparing those that are poisonous and those that are not, as well as the genetics behind color-pattern mimicry.

Reed, R. D., Papa, R., Martin, A., Hines, H. M., Counterman, B. A., Pardo-Diaz, C., Jiggins, C. D., ... McMillan, W. O. (January 1, 2011). optix drives the repeated convergent evolution of butterfly wing pattern mimicry. Science, 333, 6046, 1137-41.

This particular article was very helpful. It described a particular experiment that was done to the Heliconius butterfly in order to determine what genes are associated with the red wing color that is expressed by many of the individuals in this genus. The researchers wanted to learn more about what gene causes the red “warning” color of the wings in order to determine whether or not the red coloring of other butterflies is due to convergent evolution or homology. What they located was an Optix gene which controls the red coloration not just on Heliconius butterflies that are closely related but also for those which are highly divergent from one another.