The influence of size, longevity and environmental temperature on mitochondrial DNA evolution in fishes

Abstract The link between longevity and mitochondrial function has been documented; therefore, we suspect that the evolution of mitochondrial DNA (mtDNA) is linked to the evolution of longevity. We selected 128 fish species with a wide range of longevity and inhabiting habitats with differing temperatures and examined their association with dN/dS ratios of mtDNA genes. Our findings (i) rule out environmental temperature as a primary driver of longevity, (ii) confirm the negative relationship between synonymous substitution rate and longevity for four of the mitochondrial protein coding genes, (iii) reveal a correlation of the fish body length at maturity with the dN/dS ratio for ATP6, ND1 and ND4, and (iv) highlight for the first time to our knowledge, a link between high conservation of the three cytochrome c oxidase (COX) genes and adaptation to temperatures in fishes. By extending conclusions drawn from mtDNA to individual genes, our study opens new avenues for exploring the ageing process. Moreover, the specific link between the evolution of COX genes and habitat temperature confirms the importance of complex IV in temperature adaptation. Our findings also suggest a link between dN/dS in complex I genes and longevity, highlighting the need to examine the functional association between their encoded peptides and lifespan. This article is part of the theme issue ‘Evolutionary genetics of mitochondria: on diverse and common evolutionary constraints across eukarya’.