Behaviour 2019
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Maturation and stabilization of the infant gut microbiome in wild geladas 
Alice Baniel1,2, Jacinta C Beehner3,4, Thore J Bergman3,5, Arianne Mercer6, Lauren Petrullo 3, Laurie Reistema7, Sierra Sams6, Noah Snyder-Mackler1,2, Amy Lu8. 1Center for Evolution and Medicine, Arizona State University, Tempe, AZ, United States; 2School of Life Sciences, Arizona State University, Tempe, AZ, United States; 3Department of Psychology, University of Michigan, Ann Arbor, MI, United States; 4Department of Anthropology, University of Michigan, Ann Harbor, MI, United States; 5Department of Ecology and Evolutionary Biology, University of Michigan, Ann Harbor, MI, United States; 6Department of Psychology, University of Washington, Seattle, WA, United States; 7Department of Anthropology, University of Georgia, Athens, GA, United States; 8Department of Anthropology, Stony Brook University, Stony Brook, NY, United States

Early-life development of the gut microbiome has a long-lasting impact on metabolism, the nervous system, and immunity. Yet, gut microbiome maturation remains poorly studied in wild mammals. Here, we analyzed the gut microbiome composition of wild infant geladas (Theropithecus gelada) using 16s rRNA amplicon sequencing of 525 fecal samples from 89 individuals between 0-3 years old. We characterized age-associated changes in the composition and function of the infant gut microbiome. Age was the strongest predictor of the gut microbiome community assemblage (beta diversity). Further, microbial richness (alpha diversity) increased rapidly during the first 10 months of life and plateaued to an adult-like composition by 18 months of age, the approximate age of behavioral weaning. Younger infants had more bacterial taxa associated with milk digestion, while older infants harbored more fiber-degrading bacteria, associated with the introduction of grasses in their diet. Together, our findings highlight the dynamic nature of the gut colonization process in early life. Future studies should aim at unraveling the socioecological determinants generating inter-individual variation.