User:Sabol.39/sandbox

Sandbox for Evolution Topic: The evolution of warning coloration in animals.

https://en.wikipedia.org/wiki/Aposematism Three possible improvements for this page: 1. In the sentence “A second possibility is dietary conservatism, in which predators avoid new prey because it is an unknown quantity,[18] a longer-lasting effect than neophobia.” quantity should be changed to “an unknown quality” or “novel color morph” because in the article cited as the source for this sentence there is no information suggesting that the quantity is what deters predators, it instead discusses how predators’ avoidance of a new color morph could allow those individuals to increase in frequency because of their novel coloration. 2. The entire Prevalence section contains only one citation, leaving every piece of information uncited except one. Additionally once sources are found, more specific numbers should be provided in order to be clearer, like how many species exhibit aposematic coloration in each group listed or a percentage estimate of how many species in each group exhibit this coloration, for example the amount or percentage of aposematic prevalence in vertebrates vs. invertebrates. 3. The sentence “Batesian mimics are known to adapt their mimicry to match the prevalence of aposematic organisms in their environment.” is unclear and needs more explanation of how this is possible and any examples. An individual cannot change its own coloration, so the mechanics of the matching process are not well explained. However, this sentence is not linked to a citation so the source of this sentence is unknown.

Sentence: (The sentence I added provides clarity as to what distance dependent camouflage is because it is mentioned in the sentence before but not at all explained. Since the widespread belief is that warning coloration is a polar opposite of camouflage, the concept of distance dependent coloration needed explanation.) Some forms of warning coloration provide this distance dependent camouflage by having an effective pattern and color combination that do not allow for easy detection by a predator from a distance, but are warning-like from a close proximity, allowing for an advantageous balance between camouflage and aposematism.

Citation: Listed as #7 on the page. This format does not match the rest of my bibliography because I used another citation on the wikipedia page as a guide for how to cite my article so that it would show up correctly on Wikipedia and would be linked to a numbered in-text citation. For my actual paper I will have all of my sources in one format.

Annotated Bibliography: Lindstrom, L., Alatalo, R. V., Mappes, J., Riipi, M., and Vertainen, L. (1999), CAN APOSEMATIC SIGNALS EVOLVE BY GRADUAL CHANGE? Nature, 397: 249-251. doi: 10.1038/16692

Most explanations of the evolution of warning coloration assume that extreme phenotypes were instant. This study looks at the possibility of a gradual process of small changes building up to such bright coloration. While it is shown not to be a perfect explanation, it could play a small part in the evolution of this trait.

Marples, N. M., Kelly, D. J. and Thomas, R. J. (2005), PERSPECTIVE: THE EVOLUTION OF WARNING COLORATION IS NOT PARADOXICAL. Evolution, 59: 933–940. doi: 10.1111/j.0014-3820.2005.tb01032.x

Warning coloration at first seems maladaptive since the first few brightly colored individuals would be need to be eaten, to the detriment of the predator, for the warning signal to have any meaning. However, this study disproves the accepted paradox of warning coloration by showing that predators may treat novel and drastic color morphs with caution, even before the toxic element is realized.

Merilaita, S. and Tullberg, B. S. (2005), CONSTRAINED CAMOUFLAGE FACILITATES THE EVOLUTION OF CONSPICUOUS WARNING COLORATION. Evolution, 59: 38–45. doi: 10.1111/j.0014-3820.2005.tb00892.x

This article also tries to disprove the paradox of warning coloration by showing that such extreme warning coloration is a favorable alternative when there is such differentiation among different areas of a habitat that effective camouflage is difficult to develop. If camouflage is not particularly effective, alternative defense methods and coloration should be favored.

Rudh, A., Rogell, B., Håstad, O. and Qvarnström, A. (2011), RAPID POPULATION DIVERGENCE LINKED WITH CO-VARIATION BETWEEN COLORATION AND SEXUAL DISPLAY IN STRAWBERRY POISON FROGS. Evolution, 65: 1271–1282. doi: 10.1111/j.1558-5646.2010.01210.x

This article argues that aposematic (warning) coloration could be found in certain species and not others because of links to different mating behaviors. If brighter individuals also participated in drastically different mating behaviors the species would quickly diverge into two because their mating strategies would be incompatible.

Servedio, M. R. (2000), THE EFFECTS OF PREDATOR LEARNING, FORGETTING, AND RECOGNITION ERRORS ON THE EVOLUTION OF WARNING COLORATION. Evolution, 54: 751–763. doi: 10.1111/j.0014-3820.2000.tb00077.x

This article discusses how important the role of the predator is in the development of warning coloration. Both the learning and retention rate of the predators and the level of toxicity of the prey are important in how effective the warning signal coloration is, so different levels of these factors in various systems will result in different evolutionary rates.

FINAL WIKIPEDIA EDITS START HERE to https://en.wikipedia.org/wiki/Aposematism

Prevalence
Perhaps the most numerous and well-known vertebrate group with aposematic coloration being poison dart frogs.

Behaviour
Additionally, aposematic species do not need to hide or stay still to allow camouflage to work as cryptic organisms do, so aposematic individuals benefit from more freedom in exposed areas and more time spent foraging instead of hiding, allowing them to find more and better quality food. Aposematic individuals can also be more conspicuous with their mating displays because they do not need to stay hidden from predators. .

Evolution
If warning coloration puts the first few individuals at such a strong disadvantage, it would never last in the species long enough to become beneficial.

These two theories go against the original idea that novel, brightly colored individuals would be more likely to be eaten or attacked by predators. 22

Another possibility is that females may prefer brighter males, so sexual selection could result in aposematic males having higher reproductive success than non-aposematic males if they can survive long enough to mate. Sexual selection has been shown in many cases to be strong enough to allow seemingly maladaptive traits to persist despite other factors working against the trait.

Once aposematic individuals reach a certain threshold population due to one of the above theories, the predator learning process would be spread out over a larger number of individuals and therefore is less likely to wipe out the trait for warning coloration completely. Additionally, if the population of aposematic individuals all originated from the same few individuals the few that are eaten will still benefit from the higher reproductive success of their surviving relatives through kin selection. The individuals being preyed on through the predator learning process would result in a stronger warning signal for their kin, resulting in higher inclusive fitness for the dead or injured individuals because of the increased success of their surviving relatives.

References added Maan, M. E. and Cummings, M. E. (2009), Sexual dimorphism and directional sexual selection on aposematic signals in a poison frog. Proceedings of the National Academy of Sciences of the United States of America, 106: 19072-19077.

Speed, M. P., Brockhurst, M. A. and Ruxton, G. D. (2010), The dual benefits of aposematism: predator avoidance and enhanced resources collection. Evolution, 64: 1622-1633.

Rudh, A., Rogell, B., Håstad, O. and Qvarnström, A. (2011), Rapid population divergence linked with co-variation between coloration and sexual display in strawberry poison frogs. Evolution, 65: 1271–1282. doi: 10.1111/j.1558-5646.2010.01210.x

Lee, T. J., Marples, N. M. and Speed, M. P. (2010), Can dietary conservatism explain the primary evolution of aposematism? Animal Behaviour, 79: 63-74.

Servedio, M. R. (2000), The effects of predator learning, forgetting, and recognition errors on the evolution of warning coloration. Evolution, 54: 751–763. doi: 10.1111/j.0014-3820.2000.tb00077.x

FINAL PAPER DRAFT STARTS HERE

Aposematism: The Evolutionary Conundrum

Aposematic coloration, though present in a diverse array of unrelated taxa, has long been regarded as a paradox of evolution that has confounded researchers (Marples et al., 2005). Also referred to as warning coloration, aposematism is the bright coloration of a prey species, usually red or yellow, to signal that they are distasteful or toxic to predators (Thomas et al., 2003). These colors are quite common in toxic or distasteful species, and there is a clear and demonstrated benefit to aposematism, as predators do readily avoid animals like poison dart frogs that display this coloration (Servedio, 1999). Additionally, aposematic species do not need to hide or stay still to allow camouflage to work as cryptic organisms do, so aposematic individuals benefit from more freedom in exposed areas and more time spent foraging instead of hiding, allowing them to find more and better resources, resulting in better body quality and health (Speed et al., 2010). Aposematism is also beneficial to predators as they can avoid toxic or distasteful prey based on the visual color signal. This coloration is such a recognizable and strong signal that some non-toxic species that look similarly enough to aposematic species in body plan have evolved to display these same bright colors to gain the predator avoidance without actually being harmful to predators, though this paper will only focus on the evolution of true aposematic coloration, not the role of mimicry (Merilaita and Tullberg, 2005). While aposematic coloration offers a fitness benefit once it is established, the enigma lies in the initial origin of bright coloration as a signal for toxicity or distastefulness. So many species exhibit camouflage to avoid detection by predators it seems counterintuitive that such conspicuous coloration can persist or reach fixation (Merilaita and Tullberg, 2005). The individuals with novel, bright coloration would seem to be at a strong selective disadvantage because they would stand out to predators so distinctly that it seems unlikely that these few first aposematic individuals would persist and reproduce long enough for predators to develop the connection between the bright coloration and the toxicity or distastefulness (Marples et al., 2005). There have been many studies conducted in order to attempt to understand how this initially maladaptive coloration could persist long enough to evolve as an effective signaling strategy. While studies have identified many small factors that may play a role in the development and persistence of warning coloration, there are two main theories that offer much more complete, though not foolproof, explanations for the evolution of aposematism: dietary conservatism and sexual selection.

Dietary conservatism has been the predominant theory for the initial evolution of aposematism (Marples et al., 2005). The principle of dietary conservatism is that predators will avoid novel morphs of prey simply because they are unfamiliar (Lee et al., 2010). This idea goes against the original idea that novel, conspicuous color morphs would be at a selective disadvantage (Thomas et al., 2003). There have been many studies beginning in the 1960s suggesting the presence of dietary conservatism. Robins, and many predatory birds, are shown to avoid food in unfamiliar, novel colors, especially red and yellow, allowing these traits to reach fixation in a much larger percentage of laboratory trials than would be expected due to drift alone, making it seem likely that the birds were actively avoiding the novel-colored prey (Thomas et al., 2003). However, it is difficult to experimentally tease apart whether dietary conservatism contributed to the prevalence of aposematic coloration or if an evolutionary history with aposematic species led to dietary conservatism (Marples et al, 2005).

In theory, dietary conservatism could develop before aposematism because the optimal foraging strategy would be to forage for familiar food if it is available because these food sources have been proven successful (Lee et al., 2010). Additionally, dietary conservatism has been shown to be present even when the novel color is not one that is associated with aposematism, suggesting that dietary conservatism is a general initial avoidance of unfamiliar prey, not specifically developed as a response to aposematic colors (Thomas et al., 2003).

Dietary conservatism, however, would only protect the novel, conspicuous individuals when they were novel and relatively rare. Therefore, the predators would still have to learn that an actual cost, toxicity or distastefulness, is associated with aposematic colors. As aposematic coloration becomes less novel and less rare, the individuals are no longer protected by dietary conservatism, but, as shown in several laboratory studies and models, dietary conservatism can last for several generations until the individuals reach a threshold population size (Lee et al., 2010). Once the aposematic coloration was no longer rare, the negative impacts of predation, whether the individual is killed by the predation attempt or is simply injured, are spread out among a larger population so the predators can learn the connection between the unpalatable prey and the prey’s bright coloration without wiping out all of the aposematic individuals (Lee et al., 2010). Additionally, if the growing aposematic sub-population all resulted from the same first few individuals, kin selection could result in the individuals that were preyed upon having higher indirect fitness from the increased reproductive success of that individual’s aposematic kin that did survive despite the individual itself having potentially lower or nonexistent direct fitness (Servedio, 2000). The predated individual’s kin would be at a higher reproductive fitness because the predation of some aposematic individuals contributes to predators learning the association underlying aposematic coloration and therefore making this coloration signal beneficial. This kin selection theory helps show that aposematism could persist if the aposematic population could initially become large enough to support some levels of predation through to the predators’ learning process. The few individuals eaten or harmed through predator learning would be gaining indirect fitness benefits from predators recognizing aposematic coloration in future interactions with other aposematic individuals, some of which are the original individual’s kin (Servedio, 2000). Once the system is past the initial predator learning phase aposematism would offer a fitness advantage to prey due to predator avoidance, so the trait would likely persist or be driven to fixation (Marples et al., 2005). The theory of dietary conservatism has been a leading theory, however it requires so many stages before aposematism is beneficial that it is a combination of many assumptions. The specific assumptions needed for this theory to be plausible limits this theory from being generally applied to all environments and situations in which aposematism is present, so it cannot be accepted as the definitive evolutionary explanation for aposematism (Lee et al., 2010). Another possible theory for the establishment and persistence of aposematism is sexual selection. There are many cases in nature where seemingly maladaptive traits have persisted and become advantageous because these traits are preferred by potential mates and therefore become linked to higher fitness. There is some evidence that sexual selection acts in favor of bright aposematic coloration, which could account for the establishment of bright coloration that, without predator learning seems maladaptive. Additionally, females of many species have been shown to have a preference for brighter males, even those that are not aposematic (Maan and Cummings, 2009).

Poison dart frogs are a good aposematic model group on which to test this theory because the female reproductive investment is much higher; therefore females are the sex that exerts stronger mate choice (Maan and Cummings, 2009). Through experimentally brightening some males and running female choice trials, females in significantly brighter populations of dart frogs had a preference for brighter males. Furthermore, while aposematic coloration is present in both sexes, the males of these populations are brighter than females, showing that a higher level of aposematic coloration is sexually dimorphic to some level in these populations with sexual selection for bright coloration (Maan and Cummings, 2009).

The sexual selection theory could explain how the initially rare, novel aposematic individuals were able to have high enough reproductive success for the trait to persist, even if they were later damaged or eaten by a predator through the learning process. However, for this theory to work the males would have to survive long enough to mate before being eaten by a predator in order for the area’s predators to learn the connection between the bright coloration and the toxicity. The other alternative for this system would be that the initial aposematic individuals could benefit from female preference for brighter males if any initial predation left them alive or not severely injured. Another study with poison dart frogs found that males with more conspicuous coloring have mating displays that leave them much more exposed than males with more cryptic coloration (Rudh et al., 2011). These differences in mating behavior show the different strategies of cryptic and aposematic coloration and that these two strategies could diverge over time, each having their own costs and benefits. The presence of two different mating display strategies is a possible mechanism for how speciation occurred between aposematic individuals and highly camouflaged individuals, as species that exclusively exhibit each strategy occur today. Female dart frog preference has been shown to be population-specific, which reinforces that populations can diverge and become more distinct in female preference (Maan and Cummings, 2008). Any presence of female preference, however, has mainly been tested in poison dart frogs, only a small clade of the many species that exhibit aposematic coloration, whereas dietary conservatism has been observed in almost every species of predatory bird for which is has been tested, and these birds prey on a wide variety of aposematic species, including many different types of insects and other species of birds (Marples et al., 2005). Another problem with the potential role of sexual selection, similar to a problem with the dietary conservatism theory, is that it is also possible that females currently have a preference for bright males because male brightness is a true indicator of the reduced predation risk due to aposematism as an established signal (Maan and Cummings, 2009). It is difficult to tease apart whether sexual selection drove aposematism to become established or if the female preference is merely a result of the established aposematic benefits, leaving the initial evolutionary circumstances still unclear. Despite the wealth of new research being done on this topic, the paradox of aposematic evolution remains unsolved. Nevertheless, as theories are being proposed and refined a more complete picture can be developed, as one evolutionary force rarely acts alone. Dietary conservatism has been the prevailing idea for several decades, but there are many more possible variables that cannot be ignored, like sexual selection. The most prevalent issue with current theories is that today’s predatory species have evolved with aposematic individuals over time. It is nearly impossible to say if an observed theory could contribute to the initial persistence of aposematism before predators learned the signal or if that observed theory itself is a result of the fact that warning coloration signals have already been established between predators and prey. However, computer-based models could allow researchers to simulate the origin of novel aposematism without the evolutionary predispositions present in current species (Lee at al., 2010). This evolutionary paradox may have a better explanation as research techniques become more advanced and possibilities that would be impossible to test in nature can be explored.

References

Lee, T. J., Marples, N. M. and Speed, M. P. (2010), Can dietary conservatism explain the primary evolution of aposematism? Animal Behaviour, 79: 63-74.

Maan, M. E. and Cummings, M. E. (2008), Female preferences for aposematic signal components in a polymorphic poison frog. Evolution, 62: 2334-2345

Maan, M. E. and Cummings, M. E. (2009), Sexual dimorphism and directional sexual selection on aposematic signals in a poison frog. Proceedings of the National Academy of Sciences of the United States of America, 106: 19072-19077.

Marples, N. M., Kelly, D. J. and Thomas, R. J. (2005), Perspective: The evolution of warning coloration is not paradoxical. Evolution, 59: 933–940. doi: 10.1111/j.0014-3820.2005.tb01032.x

Merilaita, S. and Tullberg, B. S. (2005), Constrained camouflage facilitates the evolution of conspicuous warning coloration. Evolution, 59: 38–45. doi: 10.1111/j.0014-3820.2005.tb00892.x

Rudh, A., Rogell, B., Håstad, O. and Qvarnström, A. (2011), Rapid population divergence linked with co-variation between coloration and sexual display in strawberry poison frogs. Evolution, 65: 1271–1282. doi: 10.1111/j.1558-5646.2010.01210.x

Servedio, M. R. (2000), The effects of predator learning, forgetting, and recognition errors on the evolution of warning coloration. Evolution, 54: 751–763. doi: 10.1111/j.0014-3820.2000.tb00077.x

Speed, M. P., Brockhurst, M. A. and Ruxton, G. D. (2010), The dual benefits of aposematism: predator avoidance and enhanced resources collection. Evolution, 64: 1622-1633.

Thomas R. J., Marples N. M., Cuthill, I. C., Takahashi, M. and Gibson, E. A. (2003), Dietary conservatism may facilitate the initial evolution of aposematism. Oikos, 101: 458-466.