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Evolutionary Biology
Antagonistic coevolution
Question | Answer |
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Coevolution | The evolution of one species is affected by its interaction with another species and vice versa |
Antagonistic coevolution | Coevolution between species where at least one harms the other, such as coevolution of predators and prey, of pathogens and hosts, or of competitor species |
Virulence | Severity of disease/parasite - Ewald's theory: virulence is the rate in which a parasite converts a host to parasite offspring |
Coevolution of Rabbits and Myxoma virus | 1859 – Victoria, Australia rabbit introduction 1950 virus introduction The decline in lethality of the myxoma virus resulted from evolutionary responses by the rabbit and the virus |
The rabbit host evolved resistance | - Selection for myxoma-resistant genotypes in the host - Eventually the strain became less fatal |
The virus evolved lower lethality | • Original 1950 strain had case fatality rate (CFR) of almost 100% • Rapidly replaced by strains with 70-95% CFR • Some strains with less than 50% CFR |
It is thought that the virus evolved to become less lethal because this increases the number of new rabbit hosts that the virus can infect | The higher the pathogen’s reproductive rate (exploding cells/hour), the sicker the host |
W/ natural selection | Natural selection could therefore select for lower virus fecundity (= lower virulence), because lower virus fecundity increases host survival time and mobility, which results in higher virus transmission rate, which on balance increases virus fitness |
REFER TO POWERPOINT ON BLACKBOARD |