Insights into the bovine rumen microbial assembly submission #1

We studied the forces that drive the assembly of rumen microbiomes throughout an animal's life, with an emphasis on the balance between stochastic and deterministic processes. We documented the development of the rumen microbiome from birth to adulthood in 45 animals over 3 years using 16S-rRNA amplicon data. We found that the animals shared a group of core successional species that invaded early on in life and persisted until adulthood. Along with deterministic factors, such as age and diet, early-arriving species exerted strong priority effects, whereby the dynamics of late successional taxa was strongly dependent on the microbiome composition at early life stages. Priority effects also manifested as dramatic changes in microbiome development dynamics between animals delivered by C-section vs. natural birth, with the former undergoing much more rapid species invasion and accelerated microbiome development. Overall, our findings show that chance events early in life have a strong impact on the development of animal microbiomes.