Figure 4 Local species pools that contribute to the regional pool of microorganisms available for colonization of the infant gut Figure 4 | Local species pools that contribute to the regional pool of microorganisms available for colonization of the infant gut. Infants are colonized by microorganisms from host-associated communities, environmental communities that are not host adapted, and unknown microbial sources. The thickness of the arrows denotes the hypothesized relative contributions of microorganisms from different sources that disperse to and stably colonize the local community (infant gastrointestinal tract). Sprockett, D. et al. (2018) Role of priority effects in the early-life assembly of the gut microbiota Nat. Rev. Gastroenterol. Hepatol. doi:10.1038/nrgastro.2017.173