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Boulder Oaks Owners Club

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Bronislav Prokhorov
Bronislav Prokhorov


The laws of the Indies, though framed in many respects with a humane tendency, and liberal policy, were seldom carried into effect, and almost never for the benefit of the community. Spain in her poverty was a continual drain upon the colonies; and all the revenue that could be raised from them on the plan of a jealous and restricted commercial policy, was ever urgently called for by the mother country. So much only was kept back as was necessary to defray the expenses of the local government, and satisfy the demands of a corrupt and rapacious colonial administration. In proportion as the exigencies of Spain increased, a still greater relaxation in the government of the colonies took place. More supplies were wanted by the mother country, in consequence of the growing expense to which she was put by the French invasion.57


Understanding pathogen infectivity and virulence requires combining insights from epidemiology, ecology, evolution and genetics. Although theoretical work in these fields has identified population structure as important for pathogen life-history evolution, experimental tests are scarce. Here, we explore the impact of population structure on life-history evolution in phage T4, a viral pathogen of Escherichia coli. The host-pathogen system is propagated as a metapopulation in which migration between subpopulations is either spatially restricted or unrestricted. Restricted migration favours pathogens with low infectivity and low virulence. Unrestricted migration favours pathogens that enter and exit their hosts quickly, although they are less productive owing to rapid extirpation of the host population. The rise of such 'rapacious' phage produces a 'tragedy of the commons', in which better competitors lower productivity. We have now identified a genetic basis for a rapacious life history. Mutations at a single locus (rI) cause increased virulence and are sufficient to account for a negative relationship between phage competitive ability and productivity. A higher frequency of rI mutants under unrestricted migration signifies the evolution of rapaciousness in this treatment. Conversely, spatially restricted migration favours a more 'prudent' pathogen strategy, in which the tragedy of the commons is averted. As our results illustrate, profound epidemiological and ecological consequences of life-history evolution in a pathogen can have a simple genetic cause.


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