Best Practices in Microbial Macroecology
To spur future studies, we have developed a list of best practices for
the future of microbial macroecology. First, we recommend
hypothesis-driven inquiry where researchers use macroecological rules as
null hypotheses instead of surveying DNA for de novo patterns.
Second, macroecological rules should be used as a framework to connect
multiple factors influencing biogeographic patterns (e.g., patch size
and dispersal limitation among islands).
Third, we should consider unique limitations and prospects of microbial
ecology (microbial morphology and physiology, DNA-based studies,
destructive sampling, horizontal gene transfer, pooling across
replicates within sites for DNA sequencing) and interpret findings in
this light (reviewed in Shade et al. 2018). When comparing
macroecological rules across the tree of life, collection methods and
statistics should be standardized as much as possible to avoid
over-estimating microbial diversity, and efforts should be made to avoid
temperate zone sampling bias by increasing tropical sampling. Fourth,
researchers should examine more than DNA (e.g., organismal traits,
metabolomes) when surveying microorganisms to understand organismal
trait-based and functional macroecological patterns. Finally, we should
conduct longitudinal studies across years to understand microbial
fluctuations due to ecological and evolutionary processes. The future is
open for many lines of inquiry into the patterns and processes
underlying microbial macroecology. The promising analogs to established
macroecological rules for macroorganisms and notable exceptions we found
here provide a roadmap to guide forecasts of microbial distributions
under current future environmental conditions.