Microbial Biogeography: Patterns in Microbial Diversity across Space and Time

Microbes inhabit a wide range of habitats, from hot springs to the deep subsurface, and it is highly improbable that one will be able to observe similar biogeographical patterns across the full range of possible microbial habitats. This chapter primarily focuses on selected topics that are particularly relevant to researchers studying uncultivated microbes in natural environments in order to illustrate what one do, or do not, currently know about their biogeography. However, it is important to recognize that the "unknown unknowns" and "known unknowns" in microbial biogeography currently outnumber the "known knowns." For this reason, the chapter highlights key topics where the gaps in one's knowledge of microbial biogeography are particularly apparent. A few research topics that may be ripe avenues for future research are also highlighted in this chapter. Although the field of biogeography principally focuses on the spatial distribution of organisms, the temporal aspects of microbial biogeography may be particularly important. The entire chapter emphasizes on how studies in microbial biogeography are more difficult to conduct than comparable studies of plant or animal biogeography, largely due to the problems associated with surveying microbial communities. The study of microbial biogeography will help one to move beyond anecdotal studies and observations to build a predictive understanding of microbial diversity and the factors influencing this diversity across space and time.