Data from: 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 phylogenetic
comparative approach and leveraging on a large number of Firmicutes
genomes, we found sporulation significantly reduces the genome-wide
spontaneous DNA mutation rate and protein evolutionary rate. Contrary to
the previous study, our results provide strong evidence that the
evolutionary rates of bacteria, like those of plants and animals, are
influenced by generation-time.