Dating Alphaproteobacteria evolution with eukaryotic fossils

摘要: Abstract Elucidating the timescale of evolution bacteria is key to testing hypotheses on their co-evolution with eukaryotic hosts, which, however, largely limited by scarcity bacterial fossils. Here, we incorporate fossils date divergence times Alphaproteobacteria, based endosymbiosis theory that mitochondria evolved from an alphaproteobacterial lineage. We estimate Alphaproteobacteria arose ~1900 million years (Ma) ago, followed rapid major clades. show origin Rickettsiales, order obligate intracellular whose hosts are mostly animals, predates emergence animals for ~700 Ma but coincides eukaryotes. This, together reconstruction ancestral strongly suggests early Rickettsiales lineages had established previously underappreciated interactions unicellular Our mitochondria-based approach displays higher precision and robustness uncertainties compared traditional strategy using cyanobacterial fossils, previous applications modern symbiotic tree life may need be revisited.