Data from: Experimental demonstration of the impact of hard and soft selection regimes on polymorphism maintenance in spatially heterogeneous environments

Predicting and managing contemporary adaption requires a proper
understanding of the determinants of genetic variation. Spatial
heterogeneity of the environment may stably maintain polymorphism when
habitat contribution to the next generation can be considered independent
of the degree of adaptation of local populations within habitats (i.e.,
under soft selection). In contrast, when habitats contribute
proportionally to the mean fitness of the populations they host (hard
selection), polymorphism is not expected to be maintained by selection.
Although mathematically established decades ago, this prediction had never
been demonstrated experimentally. Here we provide an experimental test in
which polymorphic populations of Escherichia coli growing in heterogeneous
habitats were exposed to hard and soft selection regimes. As predicted by
theory, polymorphism was preserved longer under soft selection.
Complementary tests established that soft selection slowed fixation
processes and could even protect polymorphism in the long term by
providing a systematic advantage to rare genotypes.