Transition-Transversion Bias at the

A positive relationship between metabolic rate and the rate of mutation accumulation is regarded as a core prediction of the metabolic theory of ecology; however, empirical support for this relationship remains limited. One indirect but rigorous approach to testing this hypothesis is to analyze the transition-transversion bias across increasing levels of genetic divergence. This approach allows comparison of evolutionary substitution patterns among taxonomic groups that differ in metabolic rate, which can be inferred from body size and species-specific body temperature. Because transitions largely arise from spontaneous molecular processes while transversions are more strongly associated with oxidative DNA damage. These two mutation types exhibit distinct origins and mutational spectra, comparison of which will allow us to estimate the rate of mutation caused by oxidative DNA damage in taxonomic groups with different metabolic rates. The order Cypriniformes represents an excellent model system for such analyses because it includes both small- and large-bodied lineages distributed across tropical and temperate climatic zones. To identify patterns of evolutionary transition-transversion bias in the mitochondrial