Red Queen Hypothesis

Introduction

Survival of species depends on several factors. These include availability of food, adaptation to the environment, reproduction and interaction with other species (Ridley, 2009). Paleontological records have given evidence that evolution has taken place and species that have survived are those which have learned to adapt to their environment and co-exist with other species (Ridley, 2009). There are many theories used to explain the evolution of species, their survival and extinction. One of the more popular hypotheses is the Red Queen Hypothesis. Derived from Lewis Carroll’s ‘Through the Looking-Glass”, the Red Queen observed that, “Now, here, you see, it takes all the running you can do, to keep in the same place” (Lewis, 1960, p. 46). This statement inspired the Red Queen hypothesis, which proposes that in order for species to survive, it has to constantly adapt to its environment and evolve. Since most species are found in highly dynamic communities that experience perturbations and changes, organisms have to acquire mechanisms for adaptation in order to survive (Ruse and Travis, 2009).

The main aim of this essay is to relate the relevance of the Red Queen’s statement in humanity’s efforts to understand and control pests, parasites and pathogens. The First part of this brief explains the Red Queen Hypothesis and presents examples of antagonistic coevolution between parasites and hosts. The second part discusses the parasite and host’s mechanism of adaptation and coevolution. The next part critically analyses how the Red Queen’s hypothesis is used to understand and control pests, parasites and pathogens. Finally, a conclusion that summarises the key points raised in this essay will be found at the end of this essay.

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Red Queen Hypothesis

The Red Queen hypothesis is also known as the Red Arms Race (Decaestecker et al., 2007). In this hypothesis, parasites and their hosts are involved in a ‘race’ where a parasite has to use strategies in order to survive inside the body of the host (Decaestecker et al., 2007). Harvell (2004) explains that coevolution is driven by the antagonistic interactions that occur between parasites and hosts. The Red Queen Hypothesis suggests that the hosts benefits from the interaction by sexually producing offspring that are genetically heterogeneous (Harvell, 2004). As a result, the offspring are now equipped with defence mechanisms that are used against parasites. Decaestecker et al. (2007) emphasise that sexual reproduction of the host is a defence mechanism against the virulence and infection of parasites and pathogens. With offspring that are genetically unique from their parents, these new generations are better able to withstand parasitic infections.

To illustrate the Red Arms Race, Decaestecker et al. (2007) investigated the antagonistic interactions between the water flea Daphnia and their microparasites and showed how coevolution occurred over time. Noting that there is sparse literature on the dynamics of antagonistic interactions over time, these investigators were able to show that contemporary parasites of Daphnia were more infective compared to past parasite isolates. Although the group failed to establish significant net changes in the infectivity of the parasite over time, they were able to show that the parasite, Pasteuria, was able to increase its spore production. This increased production was associated with a reduction in the fecundity of the Daphnia host. Hence, Decaestecker et al. (2007) were able to establish that the fecundity of the host progressively decreased over time. The adaptation of the parasite Pasteuria is related to two mechanisms: increased spore production and increased virulence. Both of these mechanisms likely assisted in the parasites’ adaptation to the host.

Mechanism of Adaptation and Coevolution

Ruse and Travis (2009) remark that both the parasites and host undergo continuous adaptation. For instance, both hosts and parasites adapt their genotypes in order to avoid extinction. The same oscillation in the genotypes of the host and parasites actually lead to genetically diverse population of hosts and parasites (Ruse and Travis, 2009). In turn, this genetic variation leads to the survival of both host and parasite or pathogen. Hence, the application of the concept that both are running as fast as they could in order to stay alive or be in the same place.

In a meta-analysis (Greischar and Koskella, 2007), parasite migration rate significantly improves local adaptation of parasites. Similarly, virulence of the parasites and their generation time all contribute to their local adaptation. This suggests that parasites that frequently reproduce and have high virulence are able to exert higher infectivity in their local hosts. Meanwhile, Ruse and Travis (2009) observe that parasites with multihost life cycles have the ability to manipulate the behaviour of their host. By altering the behaviour of the host, the chances that a new host will consume the original host are increased. In effect, the parasite survives and infects the new host. This suggests that during natural selection, the parasites alter the behaviour of one of their hosts in order to arrive at the next host.

Controlling Pests, Parasites and Pathogens

The Red Queen hypothesis could be used to control pests, parasites and pathogens. Walter (2005) states that hosts could undergo specialisation and improve their defence mechanisms in order to eliminate their parasites. In addition, hosts undergo sexual reproduction in order to survive invasion of pathogens or parasites. Goater et al. (2013) use the example of the freshwater snail, Potamopyrgus antipodarum to exemplify the need for sexual reproduction to contain infection of parasitic trematodes. As a host to different species of trematodes, it has developed a defence mechanism that suggests that sexual reproduction is needed in order to survive (Lively et al., 2004). When the risk of infection is high, females tend to reproduce sexual individuals more than parthenogenetic individuals. Goater et al. (2013) explain that this allows the freshwater snail to reproduce heterogeneous offspring that are better able to withstand infection. Likewise, the parasitic trematodes also need to evolve in order to tract the genotypes of their freshwater snail hosts (Lively et al., 2004).

Understanding the Red Queen hypothesis is important in controlling the population of pests, pathogens and parasites. Studies cited in this brief argue that parasites have the ability to evolve along with their hosts in order to facilitate antagonistic coevolution. However, parasites are also not free from extinction. As suggested in Ruse and Travis (2009), extinction occurs when coevolution between host and parasites are not reciprocal. If the parasites fail to adapt to the host’s defences or find a new host, they are at risk of extinction. It has been shown that organisms that fail to adapt to their environment and evolve when confronted with harsh environmental conditions, are likely to become extinct (Forde et al., 2004). Today, humans control the population of parasites, pathogens and pests in a number of ways. However, biological control is seen as cost-effective and safer for the environment (Walter, 2005). Using the Red Queen Hypothesis, insect pests could be controlled through parasitism or predation. Known parasites of the insect pests could be used as biological control agents (Walter, 2005). Successful control of pests through the use of parasites or pathogens will also rely on human management. Hence, a thorough understanding of the host-parasite dynamics will help control the proliferation of animal and plan pests.

Conclusion

In conclusion, the Red Queen Hypothesis is used to explain antagonistic coevolution between host and parasites. In an effort to survive, hosts exhibit different mechanisms in order to avoid parasitic infection. These efforts include sexual reproduction of offspring that are genetically distinct from their parents and improvement of hosts’ defence mechanisms. On the other hand, to keep pace with the changes taking place in the host, parasites also coevolve in order to exert its virulence on the host. These include altering or modifying the behaviour of the host and increasing its virulence. Finally, an understanding of how parasites and host coevolve is useful in application to pest control. Parasites and pathogens could be used as biological controls of pests.

References

Decaestecker, E., Gaba, S., Raeymaekers, J., Stoks, R., Kerckhoven, L., Ebert, D. & Meester, L. (2007) ‘Host-parasite ‘Red Queen’ dynamics archived in pond sediment’, Nature Letters, 450, pp. 870-874.

Forde, S., Thompson, J. & Bohannan, B. (2004) ‘Adaptation varies through space and time in a coevolving host-parasitoid interaction’, Nature, 431, pp. 841-844.

Goater, T., Voater, C. & Esch, G. (2013) Parasitism: The diversity and ecology of animal parasites, Cambridge: Cambridge University Press.

Greischar, M. & Koskella, B. (2007) ‘A synthesis of experimental work on parasite local adaptation’, Ecology Letters 10(5), pp. 418-434.

Harvell, D. (2004) ‘Ecology and evolution of host-pathogen interactions in nature’, American Naturalist, 164, pp. S1-S5.

Lewis, C. (1960) Alice’s Adventures in Wonderland, New York: New York American Library.

Lively, C., Dybdahi, M., Jokela, J., Osnans, E. & Delph, L. (2004) ‘Host sex and local adaptation by parasites in a snail-trematode interaction’, American Naturalist, 164, pp. S16-S18.

Ridley, M. (2009) Evolution, Oxford: Oxford University Press.

Ruse, M. & Travis, J. (2009) Evolution: The first four billion years, Harvard: Harvard University Press.

Walter, G. (2005) Inspect pest management and ecological research, Cambrdige: Cambridge University Press.

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