Transition–transversion bias at the CYTB gene level in the order Cypriniformes (Actinopterygii) as evidence for the influence of metabolic rate on molecular evolutionary rate

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, whereas transversions are more strongly associated with oxidative DNA damage, the relative accumulation of these substitution types may reflect metabolic intensity.The order Cypriniformes provides an exceptional model system for such analyses, as it includes both small- and large-bodied lineages distributed across tropical and temperate climatic zones, and is characterized by extensive availability of mitochondrial DNA sequence data.