1. Selection/Recruitment
Table 1: Dissemination of genes and microorganisms throughout Earth’s Critical Zone. Three phenomena, or drivers, affect microbial/gene spread. These are: opportunity for dispersal; stochastics (the number of foreign cells landing at a particular location); and recruitment (the persistence of cells at the new location, often driven by local selection). Historically, these forces generate biogeographic patterns for microorganisms that are similar to those of animals and plants. Human impacts have changed the dynamics of these phenomena, and are altering microbial biogeography in the process.
Drivers
Dispersal
Stochastics
Selection/Recruitment
Natural forces
Wind transport
Low cell numbers
Favours endemic species
Ocean currents
Population drift
Local differentiation
Freshwater flows
Human impacts
Human movement
High cell numbers
Co-dispersal with selective agents
Animal movement
Increased evolvability
Co-selection with domesticated hosts
Agriculture
Ballast water
Moving soil / sediment
Wastewater flows