Résumé
Environmental change represents a major threat to species persistence.
When change is rapid, a population's only means of persisting may be
to evolve resistance. Understanding such ‘evolutionary rescues’ is
important for conservation in the face of global change, but also in the
agricultural and medical sciences, where the objective is rather
population control or eradication. Theory predicts that evolutionary
rescue is fostered by large populations and genetic variation, but this
has yet to be tested. We replicated hundreds of populations of the
bacterium Pseudomonas fluorescens SBW25 submitted to a range of doses of
the antibiotic streptomycin. Consistent with theory, population size, and
initial genetic diversity influenced population persistence and the
evolution of antibiotic resistance. Although all treated populations
suffered initial declines, those experiencing the smallest decreases were
most likely to be evolutionarily rescued. Our results contribute to our
understanding of how evolution may or may not save populations and species
from extinction.