Genetic variation for mitochondrial function in the New Zealand freshwater snail Potamopyrgus antipodarum
The proteins responsible for mitochondrial function are encoded by two different genomes with distinct inheritance regimes, rendering rigorous inference of genotype-phenotype connections intractable for all but a few model systems. Asexual organisms provide a powerful means for addressing these challenges because offspring produced without recombination inherit both nuclear and mitochondrial genomes from a single parent. As such, these offspring inherit mitonuclear genotypes that are identical to the mitonuclear genotypes of their parents and siblings and different from those of other asexual lineages. Here, we compared mitochondrial function across distinct asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail model for understanding the evolutionary consequences of asexuality. Our analyses revealed substantial phenotypic variation across asexual lineages at three levels of biological organization: mitogenomic, organellar, and organismal. These data demonstrate that different asexual lineages have different mitochondrial function phenotypes and that there exists heritable variation (that is, the raw material for evolution) for mitochondrial function in P. antipodarum. The discovery of this variation combined with the methods developed here sets the stage to use P. antipodarum to study central evolutionary questions involving mitochondrial function, including whether mitochondrial mutation accumulation influences the maintenance of sexual reproduction in natural populations.