Conditionally rare taxa disproportionately contribute to temporal changes in microbial diversity

Area of Science:

• Microbial Ecology
• Environmental Microbiology
• Community Dynamics

Background:

• Microbial communities contain numerous rare taxa, often termed the 'rare biosphere'.
• The ecological significance and contribution of these rare taxa to community dynamics remain largely unexplored.
• Rare microorganisms are hypothesized to enhance ecosystem stability by responding to environmental shifts.

Purpose of the Study:

• To develop and apply a novel method for detecting and quantifying conditionally rare taxa (CRT).
• To assess the contribution of CRT to temporal shifts in microbial community structure across diverse ecosystems.
• To understand the ecological role of rare taxa in microbial community dynamics.

Main Methods:

• Analysis of 16S rRNA amplicon sequencing data from 3,237 samples across 42 time series.
• Inclusion of diverse ecosystems: air, marine, freshwater, human-associated, and industrial wastewater.
• Development of a method to identify and quantify typically rare taxa that become temporarily abundant (CRT).

Main Results:

• Conditionally rare taxa (CRT) constituted 1.5% to 28% of community membership across ecosystems.
• CRT explained a substantial proportion of temporal community dissimilarity, up to 97%.
• CRT were frequently detected across multiple time points, with some appearing as 'one-hit wonders'.

Conclusions:

• Rare microbial taxa, particularly CRT, play a disproportionately large role in microbial community dynamics.
• The findings highlight the importance of considering rare taxa for a comprehensive understanding of ecosystem function.
• The presence and impact of CRT are consistent across a wide range of environmental and host-associated microbial communities.