  A key question in evolution is how likely a mutant is to take over. This
depends on natural selection and on stochastic fluctuations. Population spatial
structure can impact mutant fixation probabilities. We introduce a model for
structured populations on graphs that generalizes previous ones by making
migrations independent of birth and death. We demonstrate that by tuning
migration asymmetry, the star graph transitions from amplifying to suppressing
natural selection. The results from our model are universal in the sense that
they do not hinge on a modeling choice of microscopic dynamics or update rules.
Instead, they depend on migration asymmetry, which can be experimentally tuned
and measured.
