Variation in physiological function across source populations of a New Zealand freshwater snail

The mitochondrial and nuclear-encoded genes responsible for cellular respiration are expected to experience relatively intense purifying selection, meaning that variation in these genes will often decrease fitness. Still, extensive variation for mitochondrial haplotype and function persists in natural populations. We integrated physiological, cellular, and behavioral approaches to quantify phenotypes relevant to mitochondrial function across a diverse sample of Potamopyrgus antipodarum , a New Zealand snail characterized by frequent coexistence between otherwise similar sexual and asexual individuals. We found extensive across-lake variation in organismal oxygen consumption and behavioral response to heat stress coupled with elevated mitochondrial membrane potential in males vs. females. These data set the stage for applying this important model system for sex, host-parasite interactions, invasion biology, and ecotoxicology to novel tests of the relationships between mitochondrial variation and performance in natural populations.