Mutational jackpot: crossing a fitness valley

Spatial structured populations primarily grow at the edge. In 2016, an interesting paper by Diana Fusco et al. has shown how spatial growth promotes the emergence of "jackpot mutations", resulting in mutant clones with an unexpectedly high abundance. Here, I illustrated how this effect enables a lineage to go through a fitness valley, where the first mutation (yellow) has an elevated death rate compared to the wild type (purple), and the double-mutant (blue) has a lower death rate (death rates are 0.1, 0.2, and 0.0). Subsequent mutations (green) do not affect the death rate.