Before revision:  We show that, for a range of models, the rate of increase in heteroplasmy variance , and the rate ofde novo mutation , is proportionately modulated by the  fraction of unfused mitochondria, independently of the absolute fission-fusion rate.
After revision:  We show that, for a range of models, the rate of increase in heteroplasmy variance , and the rate ofde novo mutation , is proportionately modulated by the (physical) fraction of unfused mitochondria, independently of the absolute fission-fusion rate.