Parasite-mediated disruptive selection in a natural Daphnia population
Author(s)
Duffy, Meghan A.
Brassil, Chad E.
Hall, Spencer R.
Tessier, Alan J.
Cáceres, Carla E.
Conner, Jeffrey K.
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Abstract
Background.
A mismatch has emerged between models and data of host-parasite evolution. Theory readily predicts that parasites can promote host diversity through mechanisms such as disruptive selection. Yet, despite these predictions, empirical evidence for parasite-mediated increases in host diversity remains surprisingly scant.
Results.
Here, we document parasite-mediated disruptive selection on a natural Daphnia population during a parasite epidemic. The mean susceptibility of clones collected from the population before and after the epidemic did not differ, but clonal variance and broad-sense heritability of post-epidemic clones were significantly greater, indicating disruptive selection and rapid evolution. A maximum likelihood method that we developed for detecting selection on natural populations also suggests disruptive selection during the epidemic: the distribution of susceptibilities in the population shifted from unimodal prior to the epidemic to bimodal after the epidemic. Interestingly, this same bimodal distribution was retained after a generation of sexual reproduction.
Conclusion.
These results provide rare empirical support for parasite-driven increases in host genetic diversity, and suggest that this increase can occur rapidly.
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Date
2008-03-07
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