Résumé
Batch cultures are frequently used in experimental evolution. Even though
they are generally considered to simply drive a growth rate increase,
traits evolution can be more complex. Indeed, recurrent batches form a
seasonal environment as different phases repeat periodically and different
traits can be under selection in the different seasons. Moreover, during
culture the impact of organisms on the environment is important since the
system is closed. Thus, the study of adaptation should take into account
the environment and eco-evolutionary feedbacks. Using the data of an
experimental evolution on yeast Saccharomyces cerevisiae, we develop a
mathematical model to understand which traits are under selection, and
what is the role of the environment for selection in a batch culture. We
show that two kinds of traits are under selection in seasonal
environments: life-history traits, related to growth and mortality, and
transition traits, related to the ability to maintain high growth rate
when the environment changes. The impact of environmental conditions can
be summarized by the length of the different seasons which weight the
importance of selection on each trait: the longer a season is, the higher
is selection on the associated traits. Since phenotypes drive the length
of each season, eco-evolutionary feedbacks emerge. Such feedbacks are
known to promote coexistence between different species or strains. Our
results show that the design of the batch in an experimental evolution can
affect which traits are most selected because of these feedbacks.