Fig. 1

Time-scale and fitness effects of mutations in the model. A Phylogenetic tree representing the evolution of a non-genic locus. A model time step t spans the average time it takes for a mutation to occur in the locus. The grey dot at \(t=0\) represents the initial non-genic sequence. Grey branches represent lineages that die out, and colored branches represent the lineage that gets fixed in the population. Fitness levels of colored branches in the fixed lineage are indicated in the color bar. The blue dot at \(t=n\) represents the most recent common ancestor of all surviving lineages whose fitness contribution is above the threshold. B Estimates of the number of years equivalent to a single time-step of the model in the different species listed on the x-axis. The point representing Chlamydomonas reinhardtii is circled in red. See Additional file 1: Table 1 for calculations. C Distributions of fitness effects (DFE) for different values of model parameters (listed for each distribution). All DFEs shown here have the same shape parameter, \(s = 0.3\), which controls how long-tailed the distributions are. The top left panel represents the DFE with model parameters closest to those measured for C reinhardtii in [18]. The bottom left panel represents the DFE with the most deleterious and least beneficial mutations. The bottom right panel represents the DFE with the most beneficial and least deleterious mutations sampled in this work