Experimental coevolution leads to a decrease in parasite-induced host mortality

Authors

  • C. BÉRÉNOS,

    1. Institute of Integrative Biology, Experimental Ecology, ETH Zürich Universitätstrasse, Zürich, Switzerland
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  • P. SCHMID-HEMPEL,

    1. Institute of Integrative Biology, Experimental Ecology, ETH Zürich Universitätstrasse, Zürich, Switzerland
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  • K. M. WEGNER

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    • Present address: Evolutionary Ecology of Marine Fishes, Leibniz Institute for Marine Sciences (IfM-Geomar), Düsternbroker Weg, Kiel, Germany and Alfred Wegener Institute for Polar and Marine Science, Wadden Sea Station Sylt, Hafenstrasse, List/Sylt, Germany.


Camillo Bérénos, Ashworth Laboratories, Room 1.54, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, UK.
Tel.: +44 131 650 7334; fax: +44 131 535 4355; e-mail: camillo.berenos@ed.ac.uk

Abstract

Host–parasite coevolution can lead to a variety of outcomes, but whereas experimental studies on clonal populations have taken prominence over the last years, experimental studies on obligately out-crossing organisms are virtually absent so far. Therefore, we set up a coevolution experiment using four genetically distinct lines of Tribolium castaneum and its natural obligately killing microsporidian parasite, Nosema whitei. After 13 generations of experimental coevolution, we employed a time-shift experiment infecting hosts from the current generation with parasites from nine different time points in coevolutionary history. Although initially parasite-induced mortality showed synchronized fluctuations across lines, a general decrease over time was observed, potentially reflecting evolution towards optimal levels of virulence or a failure to adapt to coevolving sexual hosts.

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