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The poison frogs display a wide range of coloration and toxicity among their family. The evolution and maintenance of color polymorphisms within species has emerged as an important focus of attention within evolutionary biology. Polymorphism, phenotypic variation in nature, is one of important research topics that can enhance our understanding of the evolutionary forces as well as to understand the origin and maintenance of genetic variation in natural population (Brown et al. 2010). The main evolutionary forces behind such divergence are drift and selection. Genetic drift leads to fixation or alleles or genotypes in population, in which homogenize geographically separated populations by the sufficient amount of gene flow Rudh, Rogell and Hoglund 2007). Strong divergent selection such as sexual selection can rapidly drive the fixation of different phenotypic traits in different populations (Brown et al. 2010).

Some species such as the strawberry poison frog, Oophaga pumilio, show extreme variation in color and pattern between populations that have been geographically isolated for more than 10,000 years (Brown et al. 2010). When populations are separated by geographic distances and landscape barriers, they frequently experience restricted gene flow, which can enable phenotypic divergence between populations through selection or drift (Wang and Summers 2010). In Boca del Toro archipelago western Panama, Oophaga pumilio shows an extreme example of color polymorphism by diverging their mainland phenotype with a red dorsum and blue legs into orange, yellow, green, blue and black and white morphs with various forms of melanistic patterning (Brown et al. 2010). Their variety in warning coloration is used for their visibility, toxicity and resistance to predators. Frogs that are more resistant to predators tend to have brighter colors than frogs that rely their warning coloration on their conspicuous appearance mostly (Summers and Clough 2001). When divergent phenotypes are mostly restricted to separate islands, the biogeography of color polymorphism suggests a major role for neutral process. However, the evidences that the isolation of the islands was not completed until as little as 1000 years ago when it began more than 10,000 years ago and gene flow among island populations was substantially reduced make it hard to explain that neutral process played a major role in color polymorphism(Summers et al. 1998). Therefore, some authors have argued that the extreme speed of this divergence suggests the involvement of divergent selection on coloration, rather than neutral diversification due to drift (Brown et al. 2010). Summers et al (1997) provides evidence that neutral divergence alone is unlikely to have caused the variation in color patterns. Based on Lande’s find, rapid evolution in sexually selecting species is led by the interaction of random genetic drift with natural and sexual selection such as random genetic drift in female mating preferences (Tazzyman and Iwasa 2009). Adaptive explanations for the color divergence in O. pumilio invoke major roles for natural selection (Rudh et al. 2007). Spatial variation in predators or habitat features could exert divergent natural selection on coloration in response to its subjection to predator selection. Other species such as dyeing dart frog, Dendrobates tinctorius, provides the evidence for diversifying natural selection by showing strong selection from avian predators rather than from genetic differentiation or geographic distance. Furthermore, O. pumilio coloration is likely to be subject to natural selection contributing their toxicity and color signals to avoidance of predation (Brown et al. 2010). Males present their ventral colors through similar posturing when they contest territories against invaders; therefore, ventral coloration and dorsal coloration that function primarily for predator avoidance may be subject to substantially different forms of selection (Reynolds and Fitzpatrick 2007). Since local predator community, availability of defensive alkaloids and light environments vary, it is possible to lead to variations of optical signal design. Divergence in aposematic coloration may be driven by sexual selection in response to female color preference, which in turn may be driven by selection such as sensory drive or genetic drift (Brown et al. 2010).

When a population goes through a period of reduced toxicity, evolutionary forces such as sexual selection or natural selection for local adaptation may be enough to generate divergence (Wang and Shaffer 2008). Color is known to play a role in male–female signaling, mate attraction, and male–male signaling in anurans. Mate choice plays a critical role in generating and maintaing biodiversity (Reynolds and Fitzpatrick 2007). Recent experimental tests proved that the females have preference over color morphs and their choice for dorsal coloration has contributed to divergence (Summers et al., 1997). Ventral coloration may play a larger role than dorsal coloration when they are signaling for mates. In order to reveal their ventral coloration, males enlarge their vocal sacs and posture on their front legs (Reynolds and Fitzpatrick 2007). Although sexual selection alone would not necessarily explain the initial divergence in coloration among populations, but it is quite possible that genetic drift would interact with female color preferences to trigger divergence (Brown et al. 2010). Based on Tazzyman and Iwasa’s study that involved collections of samples from main islands in the Bocas del Toro archipelago, its results proved that female preference on male calls led to call divergence and therefore divergence was driven by sexual selection. Also, sexual selection might have played an important role in bright displays in males, females or both sexes. It was shown that females prefer mates of their own color morphs.

It is possible that the color of offspring from crosses between different morphs would itself lower the survivorship of those offspring, For example, the offspring tends to show less saturated and less intense coloration than the parents. This different morphs among generations can impose a cost in terms of predation attempts in the wild (Summers, Cronin and Kennedy 2004). It is still unclear to what extent sexual selection has driven the evolution of color morphs rather than reinforcing the reproductive isolation of morphs (Wang and Shaffer 2008). In an aposematic organism such as O. pumilio, we cannot attribute a phylogenetic signal of selection to female mate choice alone.

Several studies have shown that natural or sexual selection or both can explain genetic structures. However, in order to determine the relative influences of selection and geography on genetic structure in nature, more studies will be needed(Wang and Summers 2010). Divergent color patterns and preferences may have established by a drift in small islands. They were resulted from divergent selection based on different light environments, different predator communities or combination of all. (Reynolds and Fitzpatrick 2007). When divergence is mediated by selection, it may occur among populations where gene flow is present and they are less dependent on isolation. Instead, the magnitude of divergence is dependent on the existing genetic variation and the strength of selection. For example, morph-specific mate preference including female choosiness and sexual selection on male coloration could explain the extent of phenotypic variation among populations. However, more studies need to be investigated why such distinct mate preferences have evolved and maintained. It is possible that drift and selection may interact with each other to create population divergences(Rudh, Rogell and Hoglund 2007). Direct links between mate choice and ecologically important traits are expected to contribute to speciation by producing new species as a consequence of natural selection. The shift from a uniform aposematic signal in most of the mainland distribution to morphological variation in the adjacent mainland can be explained by both changes in natural selection and increase in sexual selection (Rudh, Rogell and Hoglund 2007).

Reference Brown, J; Maan, M; Cummings, M; Summers, K (2010). "Evidence for selection on coloration in a Panamanian poison frog: a coalescent-based approach". Journal of Biogeography 37: 891-901. Daly, J. W., & Myers, C. W. (1967). Toxicity of Panamanian poison frogs (Dendrobates): some biological and chemical aspects. Science (new York, N.y.), 156,3777, 970-3. Reynolds, R. G., & Fitzpatrick, B. M. (2007). ASSORTATIVE MATING IN POISON-DART FROGS BASED ON AN ECOLOGICALLY IMPORTANT TRAIT.Evolution, 61, 9, 2253-2259. Reynolds, R. G., Fitzpatrick, B. M., & McMillan, W. O. (2007). ASSORTATIVE MATING IN POISON-DART FROGS BASED ON AN ECOLOGICALLY IMPORTANT TRAIT. Evolution, 61, 9, 2253-2259. Rudh, A; Rogell, B; Höglund, J (2007). "Non-gradual variation in colour morphs of the strawberry poison frog Dendrobates pumilio: genetic and geographical isolation suggest a role for selection in maintaining polymorphism". Molecular Ecology 16: 4284-4294. Summers, K., Bermingham, E., Weigt, L., McCafferty, S., & Dahlstrom, L. (1997). Phenotypic and genetic divergence in three species of dart-poison frogs with contrasting parental behavior. The Journal of Heredity, 88, 1.) Summers, K; Clough, ME (2001). "The evolution of coloration and toxicity in the poison frog family (Dendrobatidae)". Proceedings of the National Academy of Sciences of the United States of America 98: 6227-32. Summers, K; Cronin, T; Kennedy, T (2004). "Cross-Breeding of Distinct Color Morphs of the Strawberry Poison Frog ( Dendrobates pumilio ) from the Bocas del Toro Archipelago, Panama". Journal of Herpetology 38: 1-8. Tazzyman, S. J., & Iwasa, Y. (2010). Sexual selection can increase the effect of random genetic drift--a quantitative genetic model of polymorphism in Oophaga pumilio, the strawberry poison-dart frog. Evolution; International Journal of Organic Evolution, 64, 6, 1719-28. Wang, I; Shaffer, H (2008). "Rapid color evolution in an aposematic species: a phylogenetic analysis of color variation in the strikingly polymorphic strawberry poison-dart frog". Evolution 62: 2742-2759. Wang, I. J., & Summers, K. (2010). Genetic structure is correlated with phenotypic divergence rather than geographic isolation in the highly polymorphic strawberry poison-dart frog. Molecular Ecology, 19, 3, 447-58.

Contribution to Strawberry Poison Frog https://en.wikipedia.org/wiki/Strawberry_poison-dart_frog Strawberry poison frog, Oophaga pumilio, shows extreme variation in color and pattern between populations that have been geographically isolated for more than 10,000 years. [23] When populations are separated by geographic distances and landscape barriers, they frequently experience restricted gene flow, which can enable phenotypic divergence between populations through selection or drift. [24] Their variety in warning coloration is used for their visibility, toxicity and resistance to predators. When divergent phenotypes are mostly restricted to separate islands, the biogeography of color polymorphism suggests a major role for neutral process. However, Summers et al. (1997) [25]provide evidences that neutral divergence alone is unlikely to have caused the variation in color patterns. Based on Lande’s find, rapid evolution in sexually selecting species is led by the interaction of random genetic drift with natural and sexual selection such as random genetic drift in female mating preferences. [26] Color is known to play a role in male–female signaling, mate attraction, and male–male signaling in anurans. Based on Tazzyman and Iwasa’s study that involved collections of samples from main islands in the Bocas del Toro archipelago, its results proved that female preference on male calls led to call divergence and therefore divergence was driven by sexual selection. Mate choice plays a critical role in generating and maintaining biodiversity. [27] Furthermore, spatial variation in predators or habitat features could exert divergent natural selection on coloration in response to its subjection to predator selection. [28] It is still unclear to what extent sexual selection has driven the evolution of color morphs rather than reinforcing the reproductive isolation of morphs. [29]In an aposematic organism such as Oophaga pumilio, we cannot attribute a phylogenetic signal of selection to female mate choice alone but is quite possible that genetic drift would interact with female color preferences to trigger divergence [30]

The Evolutionary relationship of color variation and toxicity in the poison frog family

 * 1) This article focuses on the evolutionary relationship of color variation and toxicity in the poison frogs. This research shows the variation of coloration among species. Its result was also significant for showing that coloration has evolved with toxicity in the poison frog family.
 * 2) This article focuses on Strawberry Poison Frog’s color variation and pattern among island and mainland locations. After crossing the same species that are from the different locations, the researchers indicated that different color morphs can interbreed to produce viable offspring. This study is significant for proving that color pattern is under single locus control with dominance while coloration is not.
 * 3) This article focuses on the evolution of aposematism in a timely manner. Its research indicates that changes in coloration in aposematic species can occur repeatedly as independent events.   This study is important since the shifts in coloration in aposematic species can occur more regularly than predicted, which means there is a selective force.
 * 4) This study focuses on Strawberry poison frog’s gene tree across 15 distinct populations. Its result shows that there is a phenotypic divergence in lineage by colors but not by body size. Like Wang and Shaffer’s paper, it agrees that divergence in color is occurring at a fast rate.
 * 5) This study focuses on Strawberry Poison frog’s variations of genetic structure and isolation by distance based on amplified fragment length polymorphism markers. This study is important since it explains that color variation is due to the natural selection on an aposematic signal towards visual predators and sexual selection.

Assignment by Oct 1 https://en.wikipedia.org/wiki/Strawberry_poison-dart_frog Rudh, A., Rogell, B., & Höglund, J. 2007. Non-gradual variation in colour morphs of the strawberry poison frog Dendrobates pumilio: genetic and geographical isolation suggest a role for selection in maintaining polymorphism. Molecular Ecology, 16, 20, 4284-4294.

Three ways to improve the article: This is a fairly short article that has general information on Straweberry poison-dart frog. It briefly talks about the color morphs; however, it doesn't mention anything about their evolutionary relationship of color variation and toxicity. More information about their evolution of colors would be helpful. Also, this article mentions the difference of males and females on their behavior and parental care but could focus on sexual dimorphism on their phenotypic level and explain further evolutionary reasons. Lastly, a few sentences and even an entire paragraph don't have citations. It is important to cite sources.

Edit:The color variation in a strawberry poison-dart frog family is due to the natural selection on an aposematic signal towards visual predators and sexual selection generated by color morph-specific mate preferences.