Validating a Mitochondrial Sweep Accompanying the Rapid Spread of a Maternally Inherited Symbiont

Maternally inherited symbiotic bacteria that interfere with the reproduction of their hosts can contribute to selective sweeps of mitochondrial haplotypes through hitch-hiking or coordinate inheritance of cytoplasmic bacteria and host mitochondria. The sweep will be manifested by genetic variations of mitochondrial genomic DNA of symbiont-infected hosts relative to their uninfected counterparts. In particular, at the population level, infected specimens will show a reduced mitochondrial DNA polymorphism compared to that in the nuclear DNA. This may challenge the use of mitochondrial DNA sequences as neutral genetic markers, as the mitochondrial patterns will reflect the evolutionary history of parasitism, rather than the sole evolutionary history of the host. Here, I describe a detailed step-by-step procedure to infer the occurrence and timing of symbiont-induced mitochondrial sweeps in host species.