Tracking mtDNA heteroplasmy through multiple generations in the North Atlantic right whale (Eubalaena glacialis)

Mitochondrial heteroplasmy has been identified in a variety of species and can result from either paternal leakage, whereby sperm mitochondria enter the ova during fertilization, or more commonly by the "survival" and proliferation of mutant variants within an organism. From an evolutionary perspective, this process represents the generation of new mitochondrial diversity within a species. Although this has been documented in some mammalian species, it has been reported from relatively few wild mammalian populations and in no wild nonhuman population has the transfer and segregation of mitochondrial heteroplasmy been tracked through multiple generations. We report on the first case of the identification and tracking of mitochondrial control region heteroplasmy through 3 generations in the North Atlantic right whale, Eubalaena glacialis. We also identify the full segregation to the mutant variant within a single generation and thus the development of a new haplotype (haplotype G) in a maternal lineage of this endangered species. Witnessed here is the generation of mitochondrial diversity in a genetically depauperate species.