Dental calculus formation is linked to diet and phylogeny in mammals

Abstract 1) As a point of entry, the oral cavity serves as a potential first area of colonization of the host with environmental bacteria. As such, the oral microbial community not only affects a wide range of internal host processes, including health and digestion but may also reflect the external environment and ecology of the host. 2) Dental calculus, a mineralized form of dental plaque, preserves the DNA of the host microbiome through time, serving as a rich source of historical microbiota. Despite its potential to provide temporal information on the ecological and evolutionary processes of microbiomes, dental calculus has rarely been explored outside of humans and non-human primates. Hence, it remains unclear how ubiquitous it is across mammals. 3) Using natural history museum collections, we surveyed > 1600 specimens belonging to 142 species, representative of every mammalian order, to investigate the taxonomic distribution of dental calculus, and to identify factors that most strongly contribute to its formation. We found dental calculus to be abundant across mammalian taxa, with 104 of the surveyed species showing calculus deposits. 4) High fiber diets were most strongly associated with calculus presence and abundance, whereas species with high protein and fat diets showed little to no calculus deposits. We also found evidence of phylogenetic signal in calculus formation, pointing to the effects of oral/dental morphology. In addition, captivity strongly affected dental calculus formation in almost all dietary categories. Using this information, we made predictions about the likelihood of finding dental calculus in unsurveyed mammalian species, with the aim of informing future investigations. 5) Our study found that dental calculus is readily available in natural history museum collections, making it an easily accessible source of oral microbiota from wild animals. We highlight the taxonomic diversity of species presenting dental calculus and provide information and suggestions to researchers and museum curators interested in utilizing dental calculus for the study of oral microbiota, past and present.