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PAPER FINAL DRAFT Strategies of a Successful Invasion An introduced species is defined as a living organism that is not native to an ecosystem but has arrived there as a result of human activity. These species can have many effects on the native ecosystem as well as humans and even the economy. An introduced species that has negative effects on the local ecosystem are considered invasive species. Not all introduced species are considered invasive, however, as some have no effect or are even proven to be beneficial to the existing populations. Although, more often than not, these species have large effects and are very detrimental to the local ecosystem. Most non-native speciation events are caused by humans. Many of these events are unintentional, but people and goods travel around the world very fast and with great regularity and thus, there are many species of plants and animals that unknowingly go along for the ride and are then dropped off in a new area. Other invasive species are attributed to the pet trade and come about from animals that are either accidentally or intentionally released by their owners. Taking this into consideration, the question has to be asked, how do introduced populations who, have greatly reduced variation due to bottleneck and founder effects, adapt and thrive to new conditions? One of the largest factors in population dynamics is the coevolution of species. This is the relationship of a few or many species in an ecosystem exerting selection pressures on each other and thereby influencing evolution. One of the most well-known models is the Red Queen Hypothesis. This states that organisms must be constantly adapting and evolving not solely to gain advantages over competitors, but just to allow them to survive with other organisms that are constantly doing this as well. When a new species is introduced, they are no longer held in check by their natural enemies and coevolution with competitors. This allows them to make use of their full competitive potential (Aschehoug & Callaway, 2000). This can mean a big advantage over the native species who might be poorly equipped to compete with the invader. Invasive species may become established in communities because they are better competitors than the natives, but in order to hold their place, the competitive advantage of the invasive species must be maintained. Native species that are not displaced when invasive species are introduced are likely to begin to compete with invaders (Espeland & Leger, 2010). This goes back to the Red Queen Hypothesis in that all species in the same ecosystem will compete with each other either for the same resources, or a continuing battle between predator and prey. When population size and genetic diversity of native species are large enough, natives may be able to evolve traits that allow them to co-exist with invasive species. Native species can also evolve to become significant competitors with the invasive species, and thus having an effect on the fitness of invaders. Invasive species may respond the same way, creating coevolution between competing species (Espeland & Leger, 2010). Other research proposes a way for predicting if a non-native species will become established. The propagule pressure is defined as the number of individuals introduced to an area and the number of times they have been released (Allendorf & Lundquist, 2003). A greater number of individual founders would be expected to reduce the bottleneck effect by increasing variance within the founding population. Different release events may have different source populations and this would increase the variance as well. In addition, the hybridization between the populations of the discrete release events may result in the introduced species having more variance than the natives of the same species (Allendorf & Lundquist, 2003). Hybridization does not necessarily mean an increase in fitness, but it can lead to adaptive evolution in a number of ways (Ellstrand & Schierenbeck, 2000). The biggest factor is the increased genetic variation in the hybrid individual. Genetic variation by itself can be responsible for the success of populations. Another theory is the recombination between the offspring of the hybrids. This recombination will not always produce genotypes that give a fitness advantage but there is a chance some of them will lead to better adaptations than the genotypes of the parents. One of the limiting factors of populations that come about from bottleneck and founder effects are the presence of deleterious mutations or alleles that reduce the fitness of the individual. Hybridization is an opportunity to cleanse the population of these traits and reduce the genetic load. If recombination creates genotypes without this load, the descendants will have increased fitness relative to the parent generation (Ellstrand & Schierenbeck, 2000). This is another reason as to why hybridization can produce invasive populations with adaptive evolution and increased fitness. The introduction of different species into new habitats can cause major problems for the ecosystem as well as the native species populations that already inhabit the area. When a new species is introduced, it is likely that it might not have any natural predators or controls. In addition, the native species likely has not evolved defenses to the invader or they do not have the traits necessary to compete successfully with the new species. This can lead to rapid reproduction and population growth of the new species which can eventually allow them to take over an area. Not only can these species be devastating to natural ecosystems, they can cost the national government billions of dollars every year. Most of these damages come from invasive weeds and pests that destroy farmlands and the crops that our economy depends on. It is estimated that the total cost of economic damages associated with the effects of alien species and their control total approximately $120 billion dollars per year (Pimentel et al., 2008). There are around 50,000 invasive species and the numbers are increasing. In addition to these huge economic costs, around 42% of species that are threatened or endangered are at risk because of invasive species. These estimates put the problem of invasive species into a new perspective and shows how desperately education and prevention need to be improved. Even with reduced genetic variation, introduced species can adapt and thrive to new environments by bringing in competitive advantages, the potential for adaptive evolution, and utilizing hybridization advantages. It is very rare that introduced species are able to establish and become invasive. It takes at least one of the factors above but it is usually a combination that provides the right circumstances for success. With that being said, there are still a huge number of invasive species on Earth and the numbers continue to grow. These species are responsible for the destruction of many ecosystems and have cost governments billions of dollars’ worth of damage. This along with the amazing potential for population studies has put invasive species on the forefront of scientific research. There is a high demand for more knowledge on the subject and ways to prevent this from happening as well as controlling the existing populations. Being able to contain these species is crucial for future ecosystem sustainability and worldwide diversity.

References Allendorf, Fred W., and Laura L. Lundquist. (2003) "Introduction: population biology, 	evolution, and 	control of invasive species." Conservation Biology 17.1, 24-30. Callaway, Ragan M., and Erik T. Aschehoug. (2000) "Invasive plants versus their new and old 	neighbors: a mechanism for exotic invasion." Science 290.5491, 521-523. Ellstrand, Norman C., and Kristina A. Schierenbeck. (2000) "Hybridization as a stimulus for the 	evolution of invasiveness in plants?." Proceedings of the National Academy of Sciences 	97.13, 	7043-7050. Lee, Carol Eunmi. (2002) "Evolutionary genetics of invasive species." Trends in Ecology & 	Evolution 17.8, 386-391. Leger, Elizabeth A., and Erin K. Espeland. (2010) "PERSPECTIVE: Coevolution between native 	and invasive plant competitors: implications for invasive species management." Evolutionary applications 3.2, 169-178. Prentis, Peter J., et al. (2008) "Adaptive evolution in invasive species." Trends in plant science 	13.6, 	288-294. Pimentel, D., Zuniga, R., & Morrison, D. (2005). Update on the environmental and economic 	costs associated with alien-invasive species in the United States. Ecological 	economics, 52(3), 273-288. Zenni, R D, J B. Lamy, L J. Lamarque, and A J. Porté. (2014) "Adaptive Evolution and 	Phenotypic Plasticity During Naturalization and Spread of Invasive Species: 	Implications for Tree 	Invasion Biology." Biological Invasions. 16.3, 635-644.

WIKIPEDIA CONTRIBUTION https://en.wikipedia.org/wiki/Invasive_species One interesting finding in studies of invasive species has shown that introduced populations have great potential for rapid adaptation and this is used to explain how so many introduced species are able to establish and become invasive in new environments. When bottlenecks and founder effects cause a great decrease in the population size, the individuals begin to show additive variance as opposed to epistatic variance. This conversion can actually lead to increased variance in the founding populations which then allows for rapid adaptive evolution [24]. Following invasion events, selection may initially act on the capacity to disperse as well as physiological tolerance to the new stressors in the environment. Adaptation then proceeds to respond to the selective pressures of the new environment. These responses would most likely be due to temperature and climate change, or the presence of native species whether it be predator or prey [25]. Adaptations include changes in morphology, physiology, phenology, and plasticity.

Rapid adaptive evolution in these species leads to offspring that have higher fitness and are better suited for their environment. Intraspecific phenotypic plasticity, pre- adaptation and post-introduction evolution are all major factors in adaptive evolution [26]. Plasticity in populations allows room for changes to better suit the individual in its environment. This is key in adaptive evolution because the main goal is how to best be suited to the ecosystem that the species has been introduced. The ability to accomplish this as quickly as possible will lead to a population with a very high fitness. Pre-adaptations and evolution after the initial introduction also play a role in the success of the introduced species. If the species has adapted to a similar ecosystem or contains traits that happen to be well suited to the area that it is introduced, it is more likely to fare better in the new environment. This, in addition to evolution that takes place after introduction, all determine if the species will be able to become established in the new ecosystem and if it will reproduce and thrive.

https://en.wikipedia.org/wiki/American_bison It is shown, however, the wisent may have emerged by species divergence initiated by the introgression of bison bulls in a separate ancestral species. In the Section of Genetics It would be helpful to know how the Henry Mountains bison herd is fairing, being cattle gene free, compared to other populations of bison. How does the introduction of cattle genes contribute to the genetic variance of the bison after the severe bottleneck If the plains bison of antelope island are more closely related to the wood buffalo in the wood buffalo national park then to the purebred plain buffalo in Yellowstone, what does this say about the genetic variance of the subspecies.

How do introduced populations, who, more likely than not, have greatly reduced variation due to bottleneck effects, adapt and thrive to new conditions?

Herrel, Anthony, et al. "Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource." Proceedings of the National Academy of Sciences 105.12 (2008): 4792-4795. Vervust, Bart, Irena Grbac, and Raoul Van Damme. "Differences in morphology, performance and behaviour between recently diverged populations of Podarcis sicula mirror differences in predation pressure." Oikos 116.8 (2007): 1343-1352. Irschick, Duncan J., and D. R. Reznick. "Field experiments, introductions, and experimental evolution." Experimental evolution: concepts, methods, and applications of selection experiments. University of California Press, Berkeley(2009): 173-193. Kolbe, Jason J., et al. "Genetic variation increases during biological invasion by a Cuban lizard." Nature 431.7005 (2004): 177-181. Whitney, Kenneth D., and Christopher A. Gabler. "Rapid evolution in introduced species,‘invasive traits’ and recipient communities: challenges for predicting invasive potential." Diversity and Distributions 14.4 (2008): 569-580.