TABLE 2 .
Definitions of the various terms used throughout this articlea
| Term | Definition |
|---|---|
| βNTI | β-Nearest taxon index, which uses phylogenetic information to assemble random populations of microorganisms to measure whether compared communities are more or less different than random chance; differentiates deterministic and stochastic processes |
| RCBC | Raup-Crick (Bray-Curtis), which builds null communities probabilistically based upon OTU abundances within a sample to determine whether communities are more or less different than random chance alone; differentiates stochastic processes |
| Variable selection | The result of communities being more different than would be expected by random chance alone (e.g., geochemical conditions are very different between samples); deterministic process |
| Homogenizing selection | The result of communities being less different than would be expected by random chance alone (e.g., geochemical conditions are identical/different between samples); deterministic process |
| Dispersal limitation | Indicates populations between samples are unable to interact, due to separation by either time or space; stochastic process |
| Homogenizing dispersal | Indicates populations between samples are freely able to interact, potentially due to significant hydrological connectivity; stochastic process |
| Ecological drift | Occurs when communities are as different as random chance alone; primarily occurs due to random mutations or variations in generation times |
| Undominated | Indicates no single ecological process is capable of explaining the observed results |
| Cohesion | A metric that measures the complexity/interconnectedness of a given community as measured by the degree of cocorrelation |
| Positive cohesion | The cohesion result for those community members that were positively correlated; unknown interpretation |
| Negative cohesion | The cohesion result for those community members that were negatively correlated; potentially significantly related to community turnover and complexity |
| Interconnectedness | A term used to reference the degree of negative cohesion within a community |