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Dryad

What is a mammalian omnivore? Insights into terrestrial mammalian diet diversity, body mass, and evolution

Abstract

Mammalian omnivores are a broad and diverse group of mammals that are often lumped together in ecological studies. As a result, there are open questions about what macroevolutionary and macroecological information can be gained when omnivorous dietary differences are investigated in ecological and phylogenetic comparative studies. In this study, we investigate the frequency at which vertebrate prey, invertebrate prey, fibrous plant material, and non-fibrous plant material co-occur in the diets of omnivorous species. We quantify the body size distributions and phylogenetic signal of terrestrial mammals that consume different omnivorous diets and using multistate reversible jump MCMC, we assess the transition rates between mammalian diet strategies on the mammalian phylogenetic tree. We find that omnivores that consume all four food types are rare and most omnivorous mammals consume only invertebrate prey and non-fibrous plants. We also find that omnivores that only consume invertebrate prey are on average smaller than omnivores that incorporate vertebrate prey as many are from within Rodentia. Our transition rate models show that there are high transition rates from invertivorous omnivory to herbivory, and from vertebrate predation to prey mixing and ultimately invertivory. Our results suggest that prey type is an important aspect of omnivore macroevolution and macroecology, as it is correlated with body mass, evolutionary history, and diet-related evolutionary transition rates.