The experimental evolution of herbicide resistance in Chlamydomonas reinhardtii results in a positive correlation between fitness in the presence and absence of herbicides.
Pleiotropic fitness trade-offs will be key determinants of the evolutionary dynamics of selection for pesticide resistance. However, for herbicide resistance, empirical support for a fitness cost of resistance is mixed, and it is therefore also questionable what further ecological trade-offs can be assumed to apply to herbicide resistance. Here, we test the existence of trade-offs by experimentally evolving herbicide resistance in Chlamydomonas reinhardtii. Although fitness costs are detected for all herbicides, we find that, counterintuitively, the most resistant populations also have the lowest fitness costs as measured by growth rate in the ancestral environment. Furthermore, after controlling for differences in the evolutionary dynamics of resistance to different herbicides, we also detect significant positive correlations between resistance, fitness in the ancestral environment and cross-resistance to other herbicides. We attribute this to the highest levels of nontarget-site resistance being achieved by fixing mutations that more broadly affect cellular physiology, which results in both more cross-resistance and less overall antagonistic pleiotropy on maximum growth rate. Consequently, the lack of classical ecological trade-offs could present a major challenge for herbicide resistance management.
School of Life Sciences, University of Warwick, Coventry, UKSchool of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
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Vogwill
School of Life Sciences, University of Warwick, Coventry, UKSchool of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
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Lagator
School of Life Sciences, University of Warwick, Coventry, UKSchool of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
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Colegrave
School of Life Sciences, University of Warwick, Coventry, UKSchool of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
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Neve
D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D056084:Genetic Fitness; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000008:administration & dosage / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D008954:Models, Biological
D006540:Herbicides