Figure 1. Schematic illustration of the potential compounded effect of stochastic invasion combined with host genetics on the trajectory and mature state of the rumen microbial community.

(I) Some of the microorganisms from the common species pool in the environment are able to colonize the newborn's rumen. The shape of the bacteria represents different species, while the color represents their metabolic requirement. In the illustration, the different species of bacteria, depicted in green, can colonize the early‐life rumen along with two other species from the species pool. (II) Stochastic invasion of species in newborn hosts. The two green depicted species with high niche overlap randomly colonize different host, both setting different trajectories of colonization and exclude each other from colonizing their respective hosts. (III) Differential establishment of the microbe community based on the genetic background of the cow. The different shades of the rumen represent the different rumen conditions induced by the host. (IV) Niche modification induced by the different initial invasion. The invading and selected microbes modify the rumen environment, facilitating the arrival of late colonizers. The different rumen shades signify the differences in environmental conditions induced by the niche modification process. (V) Differential phenotypic outcome as a result of the stochastic early colonization combined with the genetic background and management history.