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

Molecular evolutionary rate varies significantly among species and a strict global molecular clock has been rejected across the tree of life. Generation time is one primary life-history trait that influences the molecular evolutionary rate. Theory predicts that organisms with shorter generation times evolve faster because of the accumulation of more DNA replication errors per unit time. While the generation-time effect has been demonstrated consistently in plants and animals, the evidence of its existence in bacteria is lacking. The bacterial phylum Firmicutes offers an excellent system for testing generation-time effect because some of its members can enter a dormant, non-reproductive endospore state in response to harsh environmental conditions. It follows that spore-forming bacteria would—with their longer generation times—evolve more slowly than their non-spore forming relatives. It is therefore surprising that a previous study found no generation-time effect in Firmicutes. Using a ...