**Figure A.1: Evolution of a founder mutation in a system with NSS 75 over time.**

The non-rounded approximation spreads quickly and increases to mean heteroplasmy 1 over time, implying a fixation probability of 1. For a closer look at the rounded system see the figure below.

**Figure A.2: Evolution of a founder mutation in a system with NSS 75 over time in a rounded system.**

Taking a closer look at the rounded approximation of the system we see that the peak of the mean heteroplasmy fixes and then spreads out over time.

*Note that all of the animations are of mean heteroplasmy against distance in micrometres.*