Competition and the Evolution of Novel Resource Use: An Experimental Test in a Virus Public Deposited

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  • March 19, 2019
Creator
  • Bono, Lisa
    • Affiliation: College of Arts and Sciences, Department of Biology
Abstract
  • Competition for resources has long been hypothesized to be a key agent of diversification: individuals utilizing a novel resource have an advantage when competition for a preferred resource is strong. Over time, competition could drive the evolution of alternative resource-use phenotypes and potentially new species. Here, we use an experimental evolution approach to establish a direct link between competition and adaptive diversification in the bacteriophage (bacteria-infecting virus) phi 6. First, we demonstrated that reducing the availability of a standard host (a vital resource) drives the origin of novel host use by selecting for a phenotype with an expanded niche (generalist). However, the generalists evolved without a detectable trade-off on the original, standard host and competitively excluded the phenotype that specialized on the standard host in all but one population. Second, we tested if competition could drive the maintenance of diversity by enabling coexistence of generalists and specialists. By increasing the ratio of the standard to novel resources, we simultaneously decreased competition for the standard resource and reduced ecological opportunity. Sustained coexistence was more likely because specialists had more time to evolve a have higher fitness on the standard host, generating a trade-off in host performance. Third, we tested if the presence of a competitor could act as a wedge, driving generalists and a competitor phenotype (the specialist) to diverge in resource use in sympatry. As a control, we evolved the generalist alone on the novel resource in allopatry. However, sympatric generalists adapted to the standard host while allopatric generalists declined on the standard host. Sympatric generalists evolved to take advantage of both hosts and minimized antagonistic pleiotropy, while allopatric generalists evolved in the absence of such selection and thereby decreased in standard host adsorption. Overall, direct costs to expanded host range remained difficult or elusive to detect, despite previous studies documenting antagonistic pleiotropy in phi 6. Rather, generalists consistently evolved with both host experienced selection to minimize antagonistic pleiotropy, which has serious implications for theory that uses these costs as the basis for divergence. Taken together, these results show strong support for the hypothesis that competition is a key agent of diversification.
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  • In Copyright
Advisor
  • Burch, Christina L.
  • Pfennig, David William
  • Zeyl, Clifford
  • Willett, Christopher
  • Servedio, Maria
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2015
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  • Chapel Hill, NC
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