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Rapid evolution of virulence leading to host extinction under host-parasite coevolution.

Rafaluk C, Gildenhard M, Mitschke A, Telschow A, Schulenburg H, Joop G - BMC Evol. Biol. (2015)

Bottom Line: In all parasite treatments of the experiment, coevolution resulted in extinction of the host population, with a pronounced increase in virulence being seen.The extinction of host populations was unexpected, particularly as parasite virulence is often seen to decrease in host-parasite coevolution.This, in combination with the increase in virulence and results obtained from the model, suggest that the inclusion of transmissive parasite stages is important to improving our understanding of virulence evolution.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Ecology and Genetics, Zoological Institute, Christian-Albrechts-Universitaet zu Kiel, Am Botanischen Garten 1-9, Kiel, 24118, Germany. charlotte.rafaluk@gmail.com.

ABSTRACT

Background: Host-parasite coevolution is predicted to result in changes in the virulence of the parasite in order to maximise its reproductive success and transmission potential, either via direct host-to-host transfer or through the environment. The majority of coevolution experiments, however, do not allow for environmental transmission or persistence of long lived parasite stages, in spite of the fact that these may be critical for the evolutionary success of spore forming parasites under natural conditions. We carried out a coevolution experiment using the red flour beetle, Tribolium castaneum, and its natural microsporidian parasite, Paranosema whitei. Beetles and their environment, inclusive of spores released into it, were transferred from generation to generation. We additionally took a modelling approach to further assess the importance of transmissive parasite stages on virulence evolution.

Results: In all parasite treatments of the experiment, coevolution resulted in extinction of the host population, with a pronounced increase in virulence being seen. Our modelling approach highlighted the presence of environmental transmissive parasite stages as being critical to the trajectory of virulence evolution in this system.

Conclusions: The extinction of host populations was unexpected, particularly as parasite virulence is often seen to decrease in host-parasite coevolution. This, in combination with the increase in virulence and results obtained from the model, suggest that the inclusion of transmissive parasite stages is important to improving our understanding of virulence evolution.

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Correlation between percentage of individuals alive at the end of the survival assay and average spore load of individual larvae [count data] from 3 individuals from each line. Error bars represent standard error of the mean
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Fig3: Correlation between percentage of individuals alive at the end of the survival assay and average spore load of individual larvae [count data] from 3 individuals from each line. Error bars represent standard error of the mean

Mentions: In the experiments of Bérénos et al. [5, 20] a trade-off was observed between spore load of dead larvae, in the case of obligate killers a proxy for transmission, and virulence, which was the most parsimonious explanation for the observed decrease in virulence [5]. We, however, found no correlation between the level of virulence of each of the lines and the average spore load per larvae (Spearman’s rank test: S = 46, p = 0.56) (Fig. 3), meaning that in our case an increase in virulence did not appear to come at a cost of decreased transmission potential.Fig. 3


Rapid evolution of virulence leading to host extinction under host-parasite coevolution.

Rafaluk C, Gildenhard M, Mitschke A, Telschow A, Schulenburg H, Joop G - BMC Evol. Biol. (2015)

Correlation between percentage of individuals alive at the end of the survival assay and average spore load of individual larvae [count data] from 3 individuals from each line. Error bars represent standard error of the mean
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4464865&req=5

Fig3: Correlation between percentage of individuals alive at the end of the survival assay and average spore load of individual larvae [count data] from 3 individuals from each line. Error bars represent standard error of the mean
Mentions: In the experiments of Bérénos et al. [5, 20] a trade-off was observed between spore load of dead larvae, in the case of obligate killers a proxy for transmission, and virulence, which was the most parsimonious explanation for the observed decrease in virulence [5]. We, however, found no correlation between the level of virulence of each of the lines and the average spore load per larvae (Spearman’s rank test: S = 46, p = 0.56) (Fig. 3), meaning that in our case an increase in virulence did not appear to come at a cost of decreased transmission potential.Fig. 3

Bottom Line: In all parasite treatments of the experiment, coevolution resulted in extinction of the host population, with a pronounced increase in virulence being seen.The extinction of host populations was unexpected, particularly as parasite virulence is often seen to decrease in host-parasite coevolution.This, in combination with the increase in virulence and results obtained from the model, suggest that the inclusion of transmissive parasite stages is important to improving our understanding of virulence evolution.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Ecology and Genetics, Zoological Institute, Christian-Albrechts-Universitaet zu Kiel, Am Botanischen Garten 1-9, Kiel, 24118, Germany. charlotte.rafaluk@gmail.com.

ABSTRACT

Background: Host-parasite coevolution is predicted to result in changes in the virulence of the parasite in order to maximise its reproductive success and transmission potential, either via direct host-to-host transfer or through the environment. The majority of coevolution experiments, however, do not allow for environmental transmission or persistence of long lived parasite stages, in spite of the fact that these may be critical for the evolutionary success of spore forming parasites under natural conditions. We carried out a coevolution experiment using the red flour beetle, Tribolium castaneum, and its natural microsporidian parasite, Paranosema whitei. Beetles and their environment, inclusive of spores released into it, were transferred from generation to generation. We additionally took a modelling approach to further assess the importance of transmissive parasite stages on virulence evolution.

Results: In all parasite treatments of the experiment, coevolution resulted in extinction of the host population, with a pronounced increase in virulence being seen. Our modelling approach highlighted the presence of environmental transmissive parasite stages as being critical to the trajectory of virulence evolution in this system.

Conclusions: The extinction of host populations was unexpected, particularly as parasite virulence is often seen to decrease in host-parasite coevolution. This, in combination with the increase in virulence and results obtained from the model, suggest that the inclusion of transmissive parasite stages is important to improving our understanding of virulence evolution.

Show MeSH
Related in: MedlinePlus