Museum specimens reveal evolutionary drivers and functions of oral microbiome in mammals

The microbiomes of wild animals, despite being integral to host survival, remain largely unexplored, particularly beyond the gut. Here, using > 450 museum-preserved dental calculus samples from 34 ecologically and phylogenetically diverse mammalian species, most of them previously unstudied, we determine the main drivers of oral microbiome evolution. We show that, similar to the gut, the oral microbiome is shaped by host ecology, particularly diet, and to a lesser extent host phylogenetic relationships. It may contribute to host adaptation, by synthesising essential micronutrients and degrading potentially harmful compounds. We also find that some oral microorganisms consistently associated with mammals throughout over evolutionary time scales and provide evidence for a likely oral origin of some rumen taxa. Together our findings demonstrate the importance of this mostly overlooked microbial community for mammalian biology.