Do microorganisms obey macroecological rules?

Abstract

Understanding the factors controlling the relative abundance, distribution, and diversity of organisms is a fundamental challenge in ecology. For plants and animals, macroecological rules have been developed that describe these large-scale distributional patterns and attempt to explain the underlying physiological and ecological processes behind them. Similarly, microorganisms exhibit patterns in relative abundance, distribution, and diversity across space and time, yet it remains unclear the extent to which microorganisms follow macroecological rules initially developed for macroorganisms. With rapid advancements in sequencing technology, we have seen a recent increase in microbial studies that utilize macroecological frameworks. Here we review and synthesize these macroecological microbial studies with two main objectives: (1) to determine to what extent macroecological rules explain the distribution of host-associated and free-living microorganisms, and (2) to understand which environmental factors and stochastic processes may explain these patterns among microbial clades (archaea, bacteria, fungi, protists) and habitats (host-associated and free living; terrestrial and aquatic). Our review is the first, to our knowledge, that examines whether or not the same environmental drivers contribute to similar trends to macroecological studies when rules are upheld for microorganisms. Further, we outline several outstanding questions and recommendations for future studies in microbial ecology.