Higher resources decrease fluctuating selection during host-parasite coevolution.
Bottom Line: We still know very little about how the environment influences coevolutionary dynamics.Our model shows that range fluctuations with lower nutrient availability can be explained both by elevated costs of resistance (a direct effect of nutrient availability), and reduced benefits of resistance when population sizes of hosts and parasites are lower (an indirect effect).Nutrient availability can therefore predictably and generally affect qualitative coevolutionary dynamics by both direct and indirect (mediated through ecological feedbacks) effects on costs of resistance.
Affiliation: Oxford Regional Molecular Genetics Laboratory, Oxford University Hospitals NHS Trust, Oxford, UK.Show MeSH
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Mentions: To more clearly visualise these results, we quantified the frequency of individual bacteria and phage phenotypes through time in each population by clustering bacteria and phage clonal isolates into discrete phenotypic complexes (using a squared Euclidean similarity of 80%). The clearest examples from each of the high and low nutrient treatments are shown in Figs3 and 4. In high nutrient media, we typically observed time-lagged directional coevolution towards generalism. The ancestral bacterium, which was sensitive to the ancestral phage, was rapidly replaced by a mutant resistant to the ancestral phage. A phage that could infect this mutant subsequently evolved. This process occurred repeatedly throughout the short experiment. By contrast, although generalists readily evolved in the low nutrient media, they were frequently replaced by phenotypes with narrower resistance and infectivity ranges.
Affiliation: Oxford Regional Molecular Genetics Laboratory, Oxford University Hospitals NHS Trust, Oxford, UK.