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The predator-prey dynamic is one of the oldest relationships in the history of life on Earth. This relationship has formed the morphological and behavioral characteristics of every species alive today and has lead to the extinction of others. Predation is also one of the largest drivers of selective pressure leading to adaptation and eventually the formation of new species. This selective pressure is the main tool used to determine the relative fitness of different traits and populations. Traits with fitness bonuses in environments with high selective pressure will be naturally selected for in the environment, which will lead to eventual evolution of populations over many generations. This ongoing battle between predators and prey is present in all divisions of life on Earth. This paper will look at the general trend of evolutionary predation and defense adaptations that have arisen throughout time including the special case of invasive predators. Invasive species can be defined as organisms or populations that have migrated from their native habitat and begin colonizing in a new ecosystem. These species can be a threat to the existing ecosystem because they may not have any natural predators in the area that will control population growth. This paper will analyze themes and examples of co-evolutionary adaptation amongst predators and prey including the special case of invasive predators.

The evolution of different traits is an extremely slow process that requires heavy selective pressure for results. Without this pressure, there will be no natural selection of traits that results in evolution of a population. This will result in a higher genotypic and phenotypic variance for the population. However, this genotypic variance is essential for the adaptations of new traits within a population. Without variance in a population, the selective pressure will be equal for all traits and there will be no difference in relative fitness among traits that is needed for adaptation. Another necessary component for the evolution of a population is the heritability of traits that are being selected for or against by the predators. In order for a trait to have a fitness bonus, it must provide a reproductive advantage for the organism, which results in the trait being passed on to the organism’s offspring.

These necessary guidelines can result in a genetic predisposition of certain traits to adapt to the environment. Some of these traits have been preserved from ancestral forms of the organism and have been adapted to fit today’s environment. One such example of this phenomenon is the different toxic components of cone snail venom for predation and defense. Venomous snails from the genus Conus have evolved a strategy for predation that involves using a harpoon-like structure to inject poisonous toxins into its prey. The chemical components of these toxins are incredibly diverse and it is hypothesized that there are different toxin “coctails” for different prey. These organisms also have different combinations of toxins that are used solely for defensive purposes. It is hypothesized that the different components of these toxins evolved separately from ancestral forms of the venoms to serve different functions. This evolution is possible due to the different environments, and thus selective pressures, of the organisms. The ancestors of this genus were primarily worm hunting organisms that were preyed upon by fish and cephalopods. The genus Conus primarily hunts fish and mollusks and its defensive venom is much more potent suggesting predators that are much larger than the individual organisms. The relationship between predator and prey has been flipped in this instance due to the evolution of a trait that allows for very potent predation and defensive venoms (Dutertre 2014).

Predisposition does not have to be an ancestral trait, it can be as simple as an elevated level of a certain chemical in the body. One example of this is the level of whole body corticosterone (CORT) in tadpoles in correlation with predator biomass and phenotypic plasticity. This experiment showed that levels of CORT in tadpoles increased with the amount of predator biomass they were exposed to. This increase in perceived selective pressure and thus CORT level is correlated with increased tail length. CORT levels also correlate directly with several behavioral characteristics of the tadpoles including locomotory. When exposed to predator biomass, the tadpoles initially suppress the CORT to prevent the change in locomotory activity to increase survival. However, as time goes on the suppression stops and CORT influences an increase in tail lengths, which will help tadpoles evade predators (Maher 2013). This experiment shows the long-term adaptations that can arise from sustained predatory selective pressure.

Strong predatory selective pressure can also induce adaptations much faster in smaller populations. One example of rapid evolution in a small population involves plants and predatory herbivore insects. In an experiment at Cornell, scientists created two plots of the plant Oenothera biennis and exposed one to insect herbivores and protected the other from predators. This separation resulted in rapid evolution of the two populations for certain traits. Genotypic and phenotypic analyses showed that herbivore resistance among the protected plants was significantly lower than that of the plants exposed to the insects. Competitive ability and flowering time in the protected plants also increased compared to the exposed plants (Agrawal 2012). This shows that the protected plants had more energy to divert to reproduction due to the relaxed selective pressure from the absence of insects. This reduction of selective pressure thus resulted in a fitness bonus for the protected plants. Among the plants exposed to the insects, adaptation occurred due to the high predatory selective pressure from the insects. It can be hypothesized that the plants in the exposed plot, which have higher herbivore resistance also have a higher relative fitness in their own population. It can also be hypothesized that if both populations were exposed to the same amount of herbivores in the future that the protected plants would have a lower relative fitness to those which, were originally unprotected.

All of these examples feature a direct defense to potential predators; however, this direct morphology is not the only mechanism that has evolved for defense. Crypsis is another defense strategy that has evolved from predator selection. Crypsis is an organism’s ability to avoid detection from predators. One example of crypsis is mimicry in which an organism has evolved morphological or behavioral traits that mock a more dangerous organism. One example of this is the mimicry of insect species on parasitic wasps. These mimic organisms have evolved characteristics almost identical to the parasitic wasps. These characteristics lead predators to believe that the mimic has the same defense strategies, in this case a sting, as the original organism (Pereiraab 2012). These mimic characteristics thus provide the same fitness boost as the sting, without incurring the energy cost.

Prey adaptations in result of predatory pressure can be behavioral as well. One famous example of a behavioral prey adaptation is stotting amongst Thompson’s gazelles. Stotting is a behavioral strategy in which an organism jumps high into the air to convey a signal to either the predator or its group. It has been hypothesized in the past that stotting is meant to convey to the predator that the gazelle is too athletic to be caught by said predator and it should look elsewhere for prey. This hypothesis has been widely disputed, however. There is evidence that stotting can be used to convey to the predator that it has been spotted and that the organism is ready to flee. This is an indirect attempt by the prey to convey to the organism that it may not be worth the energy costs to hunt. Another possible benefit of stotting is signaling to ones offspring that a predator is near. This could have an evolutionary benefit because of inclusive fitness. Inclusive fitness states that an organism wants to protect those with which it is closely related because they carry shared genetic information. Inclusive fitness induces an increased risk to the stotting organism, but a fitness bonus to all of its relatives in the group. This benefit must outweigh the risk for this behavior to be evolutionarily beneficial (Caro 1986).

Another behavioral adaptation involving group living is the herd. It is hypothesized that animals live in herds because the individual fitness bonus of each organisms living in the group is increased as the size of the group increases. This is called the selfish herd theory. An example of the selfish herd theory in nature is the behavior of seals that are hunted by sharks. It is hypothesized that these seals tend to live together because of the decreased likelihood of predation. Living in groups decreases the chance of being preyed upon because the predator can only attack one animal at a time. Thus, by associating with other seals it is less likely that an individual will be preyed upon during an encounter with a shark due to the large number of seals in the group (De Vos and O’Riain 2009). This increased chance of survival provides a fitness boost, which could lead to the behavioral trait being naturally selected for by the environment.

One special case of predator-prey adaptation is the invasive predator. Invasive predators are dangerous to ecosystems because they often have no natural predator, and thus have uncontrolled population growth. This growth is dangerous for the ecosystem because it is taking away resources from other native organisms, which could cause reduced species diversity in these ecosystems. One example of the long-term effects of an invasive species is the relationship between an invasive crawfish and a native population of tadpoles. The crawfish introduced a new selective pressure on the tadpoles that was not present before the introduction of the invasive species that lead to behavioral and morphological adaptations in the small populations tested. The tadpoles exposed to the invasive crawfish featured deeper tails and an increased activity level compared to those without this predatory selective pressure (Nunes 2014). This is slowly leading to a differentiation in diversity among tadpole populations.

Another example of adaptations derived from the selective pressure of an invasive predator is the garlic mustard plant, which has invaded North America from Europe and Asia. The garlic mustard plant secretes a toxic chemical, which can stunt the growth of plants in surrounding areas. The introduction of this plant in North America has changed the distribution of many species of plants, particularly those that are most susceptible to the toxins produced by the mustard plant (Lankau 2012). This reduction of ecosystemic diversity can affect the evolutionary trajectory of many species. By reducing the population size, the native species are more susceptible to evolutionary factors such as genetic drift. Genetic drift is a phenomenon in which variance within a small population is reduced via sampling error. This reduction of population size makes it more likely for the population to become fixed for certain alleles, which reduces genetic variance. This reduction of genetic variance can reduce a population’s ability to adapt to predators, and thus decreases the population’s fitness.

Selective predatory pressure can shape the evolutionary trajectory of prey in many ways. The changes that arise as a result of this pressure can affect the evolutionary trajectory of the predator as well. This interaction has shaped the faces of the Earth in a very significant way. Without the close co-evolution of defense adaptations and hunting mechanisms none of today’s species would exist in their current form. In conclusion, predator-prey relations have impacted the world in a very significant way and are responsible for many of the morphologies and behaviors of organisms today.

References

Agrawal, Anurag A., and A. Hastings, M.T.J Johnson. 2012. Insect Herbivores Drive Real-Time Ecological and Evolutionary Change in Plant Populations. Science 338: 113-116.

Caro, T.M. 1986. The Function of Stotting in Thompson’s Gazelles: Some Tests of the Predictions. Animal Behavior 34: 663-684.

De Vos, Alta, and J.M. O’Riain. 2009. Sharks Shape The Geometry of a Selfish Seal Herd: 	Experimental Evidence from Seal Decoys. Biol. Lett. 6: 48-50.

Dutertre, Sebastein, A. Jin, and I. Vetter. 2014. Evolution of Separate Predation and Defense Evoked Venoms in Carnivorous Cone Snails. Nat. Commun. 5: 1-9.

Lankau, Richard A. 2012. Coevolution Between Invasive and Native Plants Driven by Chemical 	Competition and Soil Biota. PNAS 109: 11240-11245.

Maher, Jessica M., E.E. Werner, and R. J. Denver. 2013. Stress Hormones Mediate Predator-Induced Phenotypic Plasticity in Amphibian Tadpoles. Proc. R. Soc. B. 280: 1-9.

Nunes, Ana L., G. Orizaola, and A. Laurila. 2014. Rapid Evolution of Constitutive and Inducible Defenses Against an Invasive Predator. Ecology 95: 1520-1530.

Pereiraab, A.I.A., G.S. Andradec, and J.C. Zanuncioa. 2012. A Brief Observation of Morphological and Behavioral Similarities Between the Ichneumonidae Wasp Cryptanura sp. and Its Presumed Mimic, Holymenia Clavigera, in Brazil. Braz. J. Biol. 73: 903-909

Change to article 11/17
Addition to article:

Adaptations against invasive predator
One special case of predator-prey adaptation is the invasive predator. Invasive predators are dangerous to ecosystems because they often have no natural predator, and thus have uncontrolled population growth. This growth is dangerous for the ecosystem because it is taking away resources from other native organisms, which could cause reduced species diversity in these ecosystems. One example of the long-term effects of an invasive species is the relationship between an invasive crawfish and a native population of tadpoles. The crawfish introduced a new selective pressure on the tadpoles that was not present before the introduction of the invasive species that lead to behavioral and morphological adaptations in the small populations tested. The tadpoles exposed to the invasive crawfish featured deeper tails and an increased activity level compared to those without this predatory selective pressure (Nunes 2014). This is slowly leading to a differentiation in diversity among tadpole populations. [24] Another example of adaptations derived from the selective pressure of an invasive predator is the garlic mustard plant, which has invaded North America from Europe and Asia. The garlic mustard plant secretes a toxic chemical, which can stunt the growth of plants in surrounding areas. The introduction of this plant in North America has changed the distribution of many species of plants, particularly those that are most susceptible to the toxins produced by the mustard plant (Lankau 2012). This reduction of ecosystemic diversity can affect the evolutionary trajectory of many species. By reducing the population size, the native species are more susceptible to evolutionary factors such as genetic drift. This reduction of population size makes it more likely for the population to become fixed for certain alleles, which reduces genetic variance. This reduction of genetic variance can reduce a population’s ability to adapt to predators, and thus decreases the population’s fitness. [25]

Article link: https://en.wikipedia.org/wiki/Anti-predator_adaptation

October 1st Assignment
Article link: https://en.wikipedia.org/wiki/Anti-predator_adaptation

change to the article: These adaptations have arisen over time because they increase an organisms ability to to survive which indirectly allows them reproduce, thus increasing the overall fitness of the organism and eventually, over a number of generations, the fitness of the population.

This change is located under the behavioral strategies heading in the article

3 ways to improve article: 1. Relate more of the adaptations to the different evolutionary forces that have influenced them Which adaptations should be related to which forces? Larson.309 (talk) 01:48, 10 October 2014 (UTC) 2. Add categories of morphological defenses Which categories should be added? Larson.309 (talk) 01:48, 10 October 2014 (UTC) 3. Include more sources that pertain to the evolutionary aspect (adaptation) of this article Which sentences need sources? Larson.309 (talk) 01:48, 10 October 2014 (UTC)

Topic: Adaptation derived from the predation vs. defense relationship among organisms
Annotated Bibliography

Agrawal, Anurag, Amy P. Hastings, and Marc TJ Johnson. "Insect Herbivores Drive Real-Time Ecological and Evolutionary Change in Plant Populations." Science Magazine 338 (2012): 113-16. HighWire Press. Web. 14 Sept. 2014. . The authors collect data on the herbivore resistant characteristics of a plant, O. biennis, in insect protected and non-insect protected plots. When the data was compared it showed that the plants in the insect protected plots had reduced herbivore resistance over generations compared to non-protected plots. This is shown by changes in flowering time and levels of defensive ellagitannins in fruit. These changes are most likely a result of the relaxation of the selective pressure from insect predators.

Dutertre, Sebastien, Ai-Hua Jin, and Irinia Vetter. "Evolution of Separate Predation- and Defence-evoked Venoms in Carnivorous Cone Snails."Nature Communications 5 (2014): 1-9. Nature. Web. 14 Sept. 2014. . The authors collect data on the ability of different snails to defend against predators based on their specific venom. They propose that the predator specific toxins in the venom evolved from a common ancestor that used the toxins to defend against cephalopod and fish predators. The authors collected the data by exposing the organism, C. Geographus, to predator tissue and analyzing the toxic components of the venom.

Maher, Jessica M., Earl E. Werner, and Robert J. Denver. "Stress Hormones Mediate Predator-induced Phenotypic Plasticity in Amphibian Tadpoles." Biological Sciences 280 (2013): 1-9. Royal Society Publications. Web. 14 Sept. 2014. http://rspb.royalsocietypublishing.org.proxy.lib.ohio-state.edu/content/280/1758/20123075.full.pdf+html The authors collected data concerning corticosterone (CORT) levels in R. sylvatica tadpoles and response to predation. They found a positive relationship between CORT levels and predator biomass in naturally occurring ecosystems. High levels of CORT are correlated with physiological changes such as larger tails in tadpoles, which can lead to a greater chance of survival. Long-term exposure of tadpoles to artificial environments with caged predators lead to an increase of CORT levels after 4 days on average. The authors believe organisms with a genetic predisposition to increase CORT levels in the body have a greater chance of survival and thus can result in adaptive phenotypic changes in the environment.

Nunes, Ana L., German Orizaola, Anssi Laurila, and Rui Rebelo. "Rapid Evolution of Constitutive and Inducible Defenses against an Invasive Predator." Ecological Society of America 95.6 (2014): 1520-530. Web. 14 Sept. 2014. . The authors collect data on the changes in tadpole populations based on the selective pressure from predatory crayfish. They compared these populations to those without the invasive crayfish. The populations with the invasive crayfish showed a long-term change in behavioral activity such as activity levels amongst tadpoles and morphological changes such as deeper tails in tadpole populations that have had long-term exposure to the invasive predator. The article specifically focuses on the effect of invasive predators on defense mechanisms over long periods of time.

Schmidt, Justin O. "Evolutionary Responses of Solitary and Social Hymenoptera to Predation by Primates and Overwhelmingly Powerful Vertebrate Predators." Journal of Human Evolution 71 (2013): 12-19.Science Direct. Web. 14 Sept. 2014. . The authors collect data on the lethality and painfulness of stings from the hymenoptera order of insects and try to derive the selective pressure these stings put on potential predators, particularly primates. The study found that the damage potential from a sting increased generally with the number of adults that inhabit the nest/colony. This implies that the higher the potential nutritional reward, the higher the capacity of the insect to inflict damage. This finding implies that the two traits adapted based on a relationship between predator and prey.