A generation time effect on the rate of molecular evolution in invertebrates

Thomas JA, Welch JJ, Lanfear R & Bromham L

(2010) Mol Biol Evol 27, 1173-1180.

The rate of genome evolution varies significantly between species. Evidence is growing that at least some of this variation is associated with species characteristics, such as body size, diversification rate or population size. One of the strongest correlates of the rate of molecular evolution in vertebrates is generation time: species with faster generation turnover tend to have higher rates of molecular evolution, presumably because their genomes are copied more frequently and therefore collect more DNA replication errors per unit time. But the generation time effect has never been tested for non-vertebrate animals. Here we present the first general test of the generation time effect in invertebrates, using 15 genes from 143 species spread across the major eumetazoan superphyla (including arthropods, nematodes, molluscs, annelids, platyhelminthes, cnidarians, echinoderms and urochordates). We find significant evidence that rates of molecular evolution are correlated with generation time in invertebrates, and that this effect applies consistently across genes, and taxonomic groups. Furthermore, the generation time effect is evident in non-synonymous substitutions, whereas theory predicts (and most previous evidence has supported) a relationship only in synonymous changes. We discuss both the practical and theoretical implications of these findings.


Andrew Rambaut, 2007