Résumé
Sexual conflicts are ubiquitous in nature and are expected to lead to an
antagonistic coevolution between the sexes. This coevolutionary process is
driven by selection on sexually antagonistic traits that can either be
directional or fluctuating. In this study, we used dormant cysts of
Artemia franciscana, collected in the same population in three different
years over a 23-year period (corresponding to ~160 generations in this
system), to investigate male-female coevolution in natural conditions over
time. We performed a cross experiment study where reproduction of females
mated to males from the past, present or future was monitored until death.
In agreement with a model of ‘fluctuating selection’, we found that
females survived better and had longer interbrood intervals when mated
with their contemporary males compared to when mated with males from the
future or the past. However, female weekly and lifetime reproductive
successes displayed no differences between contemporary and
non-contemporary matings. Finally, the coevolutionary patterns (‘arms race
dynamics’ or ‘fluctuating selection dynamics’) possibly acting on female
relative fitness could not be discriminated. This study is the first
direct demonstration that the process of male – female coevolution,
previously revealed by experimental evolution in laboratory artificial
conditions, can occur in nature on a short evolutionary time scale.