Figure 1.—

Substitution of an allele in a Moran model. Birth events are shown as gray circles and death events as black circles. The time step indicated with an arrow is immediately before a fixation event occurs. At this step, three of the chromosomes share a most recent common ancestor with each other before having a common ancestor with the fourth chromosome. One of these three chromosomes is chosen to reproduce, and the fourth is chosen to die, and a fixation event takes place (all individuals in the next step are descendants of a single reproduction event in the past). The genealogy of the substitution event is shown as dashed lines. This figure is adapted from Tajima (1990).