Author Contributions
TMB designed the field experiment. RH, FZ, MH, TMB, executed the first
phase of the field experiment. All authors contributed to maintenance of
the second phase of the experiment. RH, SEH, JDL, FZ, KS, MH, RJ, TMB
collected field data. SEH and RH analyzed data. RH led the writing of
the manuscript, in close collaboration with SEH, JDL and TMB. All
co-authors contributed critically to the manuscript and approved the
final version for publication.